use std::{
    borrow::Cow,
    collections::BTreeMap,
    fmt::Write as _,
    io::{self, Stdout},
    panic::{self, AssertUnwindSafe, PanicHookInfo},
    sync::{Arc, Mutex},
    time::{Duration, Instant},
};

use crossterm::{
    cursor::Show,
    event::{
        self, DisableBracketedPaste, DisableFocusChange, DisableMouseCapture, EnableBracketedPaste,
        EnableFocusChange, EnableMouseCapture, Event, KeyCode, KeyEvent, KeyEventKind,
        KeyModifiers, MouseEvent, MouseEventKind,
    },
    execute,
    terminal::{
        BeginSynchronizedUpdate, EndSynchronizedUpdate, EnterAlternateScreen, LeaveAlternateScreen,
        disable_raw_mode, enable_raw_mode,
    },
};
use ratatui::{
    Frame, Terminal,
    backend::CrosstermBackend,
    layout::{Constraint, Layout, Position, Rect},
    style::{Color, Modifier, Style},
    text::{Line, Span},
    widgets::{Block, Borders, Clear, Paragraph, Wrap},
};
use unicode_segmentation::UnicodeSegmentation;
use unicode_width::UnicodeWidthStr;

use crate::{
    diff::{ChangedFile, DiffState, DisplayRow, FileStatus, Focus, PaneLayout, Phase, RowKind},
    editor::{
        Completion, Cursor, Editor, Hover, Input, Mode, Palette, Selection, StartupDiagnostic,
    },
    files::{DockSide, FilePicker, FilePresentation, FileView},
    panes::{PaneRect, SplitAxis, split_rect},
    plugin::{
        Diagnostic, DiagnosticSeverity, SemanticToken, SemanticTokenKind, SemanticTokenModifier,
    },
    session::EditorSession,
    syntax::{SyntaxCache, SyntaxKind, SyntaxSpan},
    terminal_colors::{TerminalColors, ThemeColors},
    wrap::{Segment, WrapCache, caret_segment},
};

pub const CAPABILITIES: &[&str] = &["text", "styled_text", "diagnostics"];
pub(crate) const TAB_WIDTH: usize = 4;

type PanicHook = Box<dyn Fn(&PanicHookInfo<'_>) + Send + Sync + 'static>;

struct HookState {
    previous: Option<PanicHook>,
    active: bool,
}

struct TerminalSession {
    hook: Arc<Mutex<HookState>>,
}

struct ColorSchemeNotifications(bool);

impl crossterm::Command for ColorSchemeNotifications {
    fn write_ansi(&self, f: &mut impl std::fmt::Write) -> std::fmt::Result {
        f.write_str(if self.0 { "\x1b[?2031h" } else { "\x1b[?2031l" })
    }

    #[cfg(windows)]
    fn execute_winapi(&self) -> io::Result<()> {
        Ok(())
    }
}

fn restore_terminal() {
    let _ = disable_raw_mode();
    let _ = execute!(
        io::stdout(),
        EndSynchronizedUpdate,
        DisableBracketedPaste,
        DisableMouseCapture,
        DisableFocusChange,
        ColorSchemeNotifications(false),
        LeaveAlternateScreen,
        Show
    );
}

impl TerminalSession {
    fn run(body: impl FnOnce() -> io::Result<()>) -> io::Result<()> {
        let hook = Arc::new(Mutex::new(HookState {
            previous: Some(panic::take_hook()),
            active: false,
        }));
        let during_session = Arc::clone(&hook);
        panic::set_hook(Box::new(move |info| {
            let mut state = during_session
                .lock()
                .unwrap_or_else(|error| error.into_inner());
            if state.active {
                restore_terminal();
                state.active = false;
            }
            if let Some(previous) = &state.previous {
                previous(info);
            }
        }));
        let session = Self { hook };
        // set_hook is forbidden on a panicking thread. Catch first, drop the
        // owner while not panicking, then resume the original panic unchanged.
        let result = panic::catch_unwind(AssertUnwindSafe(|| {
            enable_raw_mode()?;
            session
                .hook
                .lock()
                .unwrap_or_else(|error| error.into_inner())
                .active = true;
            execute!(
                io::stdout(),
                EnterAlternateScreen,
                EnableBracketedPaste,
                EnableMouseCapture,
                EnableFocusChange,
                ColorSchemeNotifications(true)
            )?;
            body()
        }));
        drop(session);
        match result {
            Ok(result) => result,
            Err(payload) => panic::resume_unwind(payload),
        }
    }
}

impl Drop for TerminalSession {
    fn drop(&mut self) {
        let mut state = self.hook.lock().unwrap_or_else(|error| error.into_inner());
        if state.active {
            restore_terminal();
            state.active = false;
        }
        let previous = state
            .previous
            .take()
            .expect("terminal session owns its prior hook");
        drop(state);
        panic::set_hook(previous);
    }
}

#[derive(Default)]
struct DocumentViewport {
    geometry: Option<(usize, Rect)>,
    manual: Option<ManualViewport>,
    text_width: usize,
    horizontal_extent: Option<(usize, u64, usize)>,
    wrap: WrapCache,
    continuations: BTreeMap<usize, usize>,
    presentation: Option<(usize, bool, usize, usize)>,
    visible: Vec<(usize, usize, Segment)>,
    anchor: Option<(usize, u64, Cursor)>,
}

#[derive(Clone)]
struct ManualViewport {
    buffer_id: usize,
    revision: u64,
    caret_reveal_revision: u64,
    mode: Mode,
    cursor: Cursor,
    carets: Vec<Cursor>,
    selections: Vec<Selection>,
}

#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
struct VisualRow {
    source: usize,
    continuation: usize,
}

fn next_visual(cache: &mut WrapCache, lines: &[String], position: VisualRow) -> Option<VisualRow> {
    if position.continuation + 1
        < cache
            .segments(position.source, &lines[position.source])
            .len()
    {
        Some(VisualRow {
            continuation: position.continuation + 1,
            ..position
        })
    } else if position.source + 1 < lines.len() {
        Some(VisualRow {
            source: position.source + 1,
            continuation: 0,
        })
    } else {
        None
    }
}

fn previous_visual(
    cache: &mut WrapCache,
    lines: &[String],
    position: VisualRow,
) -> Option<VisualRow> {
    if position.continuation > 0 {
        Some(VisualRow {
            continuation: position.continuation - 1,
            ..position
        })
    } else if position.source > 0 {
        let source = position.source - 1;
        Some(VisualRow {
            source,
            continuation: cache.segments(source, &lines[source]).len() - 1,
        })
    } else {
        None
    }
}

fn visual_page(
    cache: &mut WrapCache,
    lines: &[String],
    start: VisualRow,
    height: usize,
) -> (VisualRow, usize) {
    let mut end = start;
    let mut count = usize::from(height > 0);
    while count < height {
        let Some(next) = next_visual(cache, lines, end) else {
            break;
        };
        end = next;
        count += 1;
    }
    (end, count)
}

fn clamp_visual_bottom(
    cache: &mut WrapCache,
    lines: &[String],
    mut start: VisualRow,
    height: usize,
) -> VisualRow {
    let (_, count) = visual_page(cache, lines, start, height);
    for _ in count..height {
        let Some(previous) = previous_visual(cache, lines, start) else {
            break;
        };
        start = previous;
    }
    start
}

#[derive(Default)]
struct BufferViewports {
    offsets: BTreeMap<usize, (usize, usize)>,
    syntax: BTreeMap<usize, SyntaxCache>,
    document: DocumentViewport,
    document_buffer: Option<usize>,
    documents: BTreeMap<usize, DocumentViewport>,
    panels: WheelPanels,
    pane: Option<usize>,
    parked: BTreeMap<usize, PaneViewport>,
    rects: Vec<(usize, Rect)>,
    theme: Option<ThemeColors>,
    diff_visible: bool,
}

#[derive(Default)]
struct PaneViewport {
    offsets: BTreeMap<usize, (usize, usize)>,
    document: DocumentViewport,
    document_buffer: Option<usize>,
    documents: BTreeMap<usize, DocumentViewport>,
    panels: WheelPanels,
}

fn pane_rect(area: Rect) -> PaneRect {
    PaneRect {
        x: area.x,
        y: area.y,
        width: area.width,
        height: area.height,
    }
}

fn terminal_rect(area: PaneRect) -> Rect {
    Rect::new(area.x, area.y, area.width, area.height)
}

impl BufferViewports {
    fn set_theme(&mut self, theme: Option<ThemeColors>) {
        if self.theme == theme {
            return;
        }
        self.theme = theme;
        let colors = DiffColors::new(theme);
        self.panels.diff_colors = colors;
        for pane in self.parked.values_mut() {
            pane.panels.diff_colors = colors;
        }
    }

    fn activate(&mut self, id: usize, editor: &Editor) {
        if self.pane == Some(id) {
            return;
        }
        if self.pane.is_none() {
            self.pane = Some(id);
            return;
        }
        if !self.parked.contains_key(&id) {
            let mut inherited = (|| {
                let buffer = editor.pane_buffer_id(id)?;
                let source = editor.pane_origin(id);
                let (offsets, document, document_buffer, documents) = if source == self.pane {
                    (
                        &self.offsets,
                        &self.document,
                        self.document_buffer,
                        &self.documents,
                    )
                } else {
                    let source = self.parked.get(&source?)?;
                    (
                        &source.offsets,
                        &source.document,
                        source.document_buffer,
                        &source.documents,
                    )
                };
                let document = if document_buffer == Some(buffer) {
                    Some(document)
                } else {
                    documents.get(&buffer)
                };
                Some(PaneViewport {
                    offsets: offsets
                        .get(&buffer)
                        .map_or_else(BTreeMap::new, |offset| BTreeMap::from([(buffer, *offset)])),
                    document: DocumentViewport {
                        continuations: document
                            .and_then(|document| document.continuations.get(&buffer))
                            .map_or_else(BTreeMap::new, |continuation| {
                                BTreeMap::from([(buffer, *continuation)])
                            }),
                        manual: document.and_then(|document| document.manual.clone()),
                        presentation: document.and_then(|document| document.presentation),
                        ..DocumentViewport::default()
                    },
                    ..PaneViewport::default()
                })
            })()
            .unwrap_or_default();
            inherited.panels.diff_colors = self.panels.diff_colors;
            self.parked.insert(id, inherited);
        }
        let outgoing = self
            .parked
            .entry(self.pane.expect("current pane exists"))
            .or_default();
        std::mem::swap(&mut self.offsets, &mut outgoing.offsets);
        std::mem::swap(&mut self.document, &mut outgoing.document);
        std::mem::swap(&mut self.document_buffer, &mut outgoing.document_buffer);
        std::mem::swap(&mut self.documents, &mut outgoing.documents);
        std::mem::swap(&mut self.panels, &mut outgoing.panels);
        let incoming = self.parked.get_mut(&id).expect("incoming pane initialized");
        std::mem::swap(&mut self.offsets, &mut incoming.offsets);
        std::mem::swap(&mut self.document, &mut incoming.document);
        std::mem::swap(&mut self.document_buffer, &mut incoming.document_buffer);
        std::mem::swap(&mut self.documents, &mut incoming.documents);
        std::mem::swap(&mut self.panels, &mut incoming.panels);
        self.pane = Some(id);
    }

    fn activate_document(&mut self, buffer: usize) {
        if self.document_buffer == Some(buffer) {
            return;
        }
        if self.document_buffer.is_none() {
            self.document_buffer = Some(buffer);
            return;
        }
        let previous = self.document_buffer.expect("current document exists");
        std::mem::swap(
            &mut self.document,
            self.documents.entry(previous).or_default(),
        );
        std::mem::swap(
            &mut self.document,
            self.documents.entry(buffer).or_default(),
        );
        self.document_buffer = Some(buffer);
    }

    fn draw(&mut self, frame: &mut Frame, editor: &mut Editor) {
        let focused = editor.pane_id();
        self.activate(focused, editor);
        self.parked
            .retain(|id, _| editor.pane_buffer_id(*id).is_some());
        self.syntax.retain(|id, _| editor.has_buffer(*id));
        let area = frame.area();
        let area = draw_tab_bar(frame, editor, area);
        let multiple = editor.pane_layout().len() > 1;
        let chrome = if !multiple && editor.diff().is_some() {
            None
        } else {
            Some(document_layout(area, editor))
        };
        let full_workspace = chrome.map_or(area, |areas| areas[0]);
        let diff_header = editor
            .diff()
            .filter(|diff| !multiple && diff.phase == Phase::View)
            .map(|_| {
                Rect::new(
                    full_workspace.x,
                    full_workspace.y,
                    full_workspace.width,
                    full_workspace.height.min(1),
                )
            });
        let (workspace, dock) = match editor.file_picker() {
            Some(picker) if picker.presentation == FilePresentation::Docked => dock_layout(
                full_workspace,
                if editor.diff().is_some() {
                    DockSide::Right
                } else {
                    editor.file_explorer_side()
                },
                picker.focused,
            ),
            _ => (full_workspace, None),
        };
        let dock = dock.map(|mut panel| {
            if let Some(header) = diff_header {
                panel.y = panel.y.saturating_add(header.height);
                panel.height = panel.height.saturating_sub(header.height);
            }
            panel
        });
        editor.set_pane_bounds(pane_rect(workspace));
        self.rects.clear();
        editor
            .pane_layout()
            .visit_rects(pane_rect(workspace), |id, area| {
                self.rects.push((id, terminal_rect(area)));
            });
        // Paint focused overlays last, so an adjacent leaf cannot erase them.
        for active_pass in [false, true] {
            for index in 0..self.rects.len() {
                let (id, mut leaf) = self.rects[index];
                if (id == focused) != active_pass {
                    continue;
                }
                self.activate(id, editor);
                self.panels.workspace_managed = true;
                if multiple {
                    let block =
                        Block::default()
                            .borders(Borders::ALL)
                            .border_style(Style::default().fg(if id == focused {
                                Color::Cyan
                            } else {
                                Color::DarkGray
                            }));
                    let inner = block.inner(leaf);
                    frame.render_widget(block, leaf);
                    leaf = inner;
                }
                let status = chrome
                    .filter(|_| id == focused)
                    .map_or(Rect::default(), |a| a[1]);
                let prompt = chrome
                    .filter(|_| id == focused)
                    .map_or(Rect::default(), |a| a[2]);
                editor.with_render_pane(id, |view| {
                    self.activate_document(view.buffer_id());
                    self.documents.retain(|id, _| view.has_buffer(*id));
                    self.offsets.retain(|id, _| view.has_buffer(*id));
                    self.document
                        .continuations
                        .retain(|id, _| view.has_buffer(*id));
                    let (top, left) = self.offsets.entry(view.buffer_id()).or_default();
                    let syntax = self.syntax.entry(view.buffer_id()).or_default();
                    draw_document(
                        frame,
                        view,
                        [leaf, status, prompt],
                        area,
                        top,
                        left,
                        syntax,
                        &mut self.document,
                        &mut self.panels,
                    );
                });
                if let Some(geometry) = &self.panels.diff {
                    editor.set_diff_pane_bounds(
                        geometry
                            .regions
                            .map(|(area, focus)| (focus, pane_rect(area))),
                    );
                }
            }
        }
        self.activate(focused, editor);
        self.panels.workspace_managed = false;
        if let Some(header) = diff_header
            && let Some(diff) = editor.diff()
        {
            draw_diff_header(frame, diff, Some(editor), header);
        }
        if let Some(panel) = dock
            && let Some(picker) = editor.file_picker()
        {
            draw_file_list(
                frame,
                picker,
                panel,
                editor.file_navigation_hint(),
                &mut self.panels,
                editor
                    .diff()
                    .and_then(|diff| diff.comparison.as_ref())
                    .map(|comparison| comparison.files.as_slice()),
            );
            if let Some(geometry) = &mut self.panels.diff {
                geometry.regions[0] = (panel, Focus::Files);
                editor.set_diff_pane_bounds(
                    geometry
                        .regions
                        .map(|(area, focus)| (focus, pane_rect(area))),
                );
            }
        }
        if let Some(diff) = editor.diff().filter(|diff| diff.phase != Phase::View) {
            draw_diff(
                frame,
                diff,
                area,
                editor.selection_navigation_hint(),
                editor.file_navigation_hint(),
                &mut self.panels,
                Some(editor),
            );
        } else {
            draw_overlays(frame, editor, area, self.panels.caret, &mut self.panels);
        }
        self.diff_visible = self
            .panels
            .diff
            .iter()
            .chain(
                self.parked
                    .iter()
                    .filter(|(id, _)| editor.pane_layout().contains(**id))
                    .filter_map(|(_, pane)| pane.panels.diff.as_ref()),
            )
            .any(|geometry| geometry.viewport.is_some());
    }

    fn draw_session(&mut self, frame: &mut Frame, session: &mut EditorSession) {
        self.draw(frame, session.editor_mut());
        if let Some((comparison_id, file, top, left_before, left_after)) = self
            .panels
            .diff
            .as_ref()
            .and_then(|geometry| geometry.viewport)
        {
            session.set_diff_viewport(comparison_id, file, top, left_before, left_after);
        }
        for (pane_id, _) in &self.rects {
            let Some(pane) = self.parked.get(pane_id) else {
                continue;
            };
            if let Some((id, file, top, before, after)) = pane
                .panels
                .diff
                .as_ref()
                .and_then(|geometry| geometry.viewport)
            {
                session.set_diff_viewport(id, file, top, before, after);
            }
        }
    }

    // Shift-wheel is the fallback for terminals without native horizontal reports.
    // Keep classification shared with popup routing.
    fn scroll(&mut self, session: &mut EditorSession, mouse: MouseEvent) -> bool {
        if wheel_kind(&mouse).is_none() {
            return false;
        }
        if self.panels.scroll(session, mouse) {
            return true;
        }
        let focused = session.editor().pane_id();
        let Some(target) = self.rects.iter().find_map(|(id, area)| {
            area.contains(Position::new(mouse.column, mouse.row))
                .then_some(*id)
        }) else {
            return false;
        };
        self.activate(target, session.editor());
        let handled = if self.panels.diff.is_some() {
            self.panels.scroll_comparison(session, mouse, target);
            true
        } else {
            session
                .editor_mut()
                .with_render_pane(target, |editor| self.scroll_document(editor, mouse))
        };
        self.activate(focused, session.editor());
        handled
    }

    fn scroll_document(&mut self, editor: &Editor, mouse: MouseEvent) -> bool {
        let Some(kind) = wheel_kind(&mouse) else {
            return false;
        };
        if editor.palette().is_some() || editor.startup_diagnostic().is_some() {
            return true;
        }
        let Some((buffer_id, viewport)) = self.document.geometry else {
            return false;
        };
        if buffer_id != editor.buffer_id()
            || viewport.width == 0
            || viewport.height == 0
            || !viewport.contains((mouse.column, mouse.row).into())
        {
            return false;
        }
        let (top, left) = self.offsets.entry(buffer_id).or_default();
        if editor.word_wrap() {
            if matches!(
                kind,
                MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
            ) {
                return true;
            }
            let continuation = self.document.continuations.entry(buffer_id).or_default();
            let mut position = VisualRow {
                source: *top,
                continuation: *continuation,
            };
            for _ in 0..3 {
                let next = if kind == MouseEventKind::ScrollDown {
                    next_visual(&mut self.document.wrap, editor.lines(), position)
                } else {
                    previous_visual(&mut self.document.wrap, editor.lines(), position)
                };
                let Some(next) = next else { break };
                position = next;
            }
            position = clamp_visual_bottom(
                &mut self.document.wrap,
                editor.lines(),
                position,
                usize::from(viewport.height),
            );
            *top = position.source;
            *continuation = position.continuation;
        } else if matches!(
            kind,
            MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
        ) {
            let key = (buffer_id, editor.text_revision());
            let columns = match self.document.horizontal_extent {
                Some((id, revision, columns)) if (id, revision) == key => columns,
                _ => {
                    let columns = editor
                        .lines()
                        .iter()
                        .map(|line| display_column(line, usize::MAX))
                        .max()
                        .unwrap_or(0);
                    self.document.horizontal_extent = Some((key.0, key.1, columns));
                    columns
                }
            };
            *left = if kind == MouseEventKind::ScrollRight {
                left.saturating_add(3)
            } else {
                left.saturating_sub(3)
            }
            .min(
                columns
                    .saturating_add(1)
                    .saturating_sub(self.document.text_width.max(1)),
            );
        } else {
            let last_page = editor
                .lines()
                .len()
                .saturating_sub(usize::from(viewport.height));
            *top = if kind == MouseEventKind::ScrollDown {
                top.saturating_add(3)
            } else {
                top.saturating_sub(3)
            }
            .min(last_page);
        }
        if self.document.manual.is_none() {
            self.document.manual = Some(ManualViewport {
                buffer_id,
                revision: editor.text_revision(),
                caret_reveal_revision: editor.caret_reveal_revision(),
                mode: editor.mode(),
                cursor: editor.cursor(),
                carets: editor.carets(),
                selections: editor.selections(),
            });
        }
        true
    }

    fn scroll_ready(
        &mut self,
        session: &mut EditorSession,
        mut mouse: MouseEvent,
        mut next: impl FnMut() -> io::Result<Option<Event>>,
    ) -> io::Result<(bool, Option<Event>)> {
        let mut redraw = false;
        // Bound input work so drawing and background replies cannot starve.
        for index in 0..64 {
            redraw |= self.scroll(session, mouse);
            if index == 63 {
                break;
            }
            match next()? {
                Some(Event::Mouse(report)) => mouse = report,
                pending => return Ok((redraw, pending)),
            }
        }
        Ok((redraw, None))
    }
}

fn wheel_kind(mouse: &MouseEvent) -> Option<MouseEventKind> {
    Some(match mouse.kind {
        MouseEventKind::ScrollUp if mouse.modifiers.contains(KeyModifiers::SHIFT) => {
            MouseEventKind::ScrollLeft
        }
        MouseEventKind::ScrollDown if mouse.modifiers.contains(KeyModifiers::SHIFT) => {
            MouseEventKind::ScrollRight
        }
        kind @ (MouseEventKind::ScrollUp
        | MouseEventKind::ScrollDown
        | MouseEventKind::ScrollLeft
        | MouseEventKind::ScrollRight) => kind,
        _ => return None,
    })
}

fn draw_frame<W: io::Write>(
    terminal: &mut Terminal<CrosstermBackend<Vec<u8>>>,
    output: &mut W,
    render: impl FnOnce(&mut Frame),
) -> io::Result<()> {
    // Do not suspend the terminal's presentation while computing the next frame.
    terminal.backend_mut().writer_mut().clear();
    crossterm::queue!(terminal.backend_mut(), BeginSynchronizedUpdate)?;
    // Terminals without synchronized updates still hide the painting cursor.
    let result = terminal
        .hide_cursor()
        .and_then(|()| terminal.draw(render).map(|_| ()));
    let finish = execute!(terminal.backend_mut(), EndSynchronizedUpdate);
    result.and(finish)?;
    output.write_all(terminal.backend().writer())?;
    output.flush()
}

/// Renders session state and translates terminal input; the session owns plugin
/// execution and retirement, so the adapter needs no lifecycle callback.
pub fn run(session: &mut EditorSession) -> io::Result<()> {
    TerminalSession::run(|| {
        let mut output: Stdout = io::stdout();
        let mut terminal = Terminal::new(CrosstermBackend::new(Vec::new()))?;
        let mut viewports = BufferViewports::default();
        let mut colors = TerminalColors::default();
        let mut query_theme = true;
        let mut redraw = true;
        let mut pending = None;
        while !session.editor().should_quit() {
            redraw |= session.poll();
            colors.expire(Instant::now());
            if viewports.theme != colors.colors {
                viewports.set_theme(colors.colors);
                redraw = true;
            }
            if redraw {
                draw_frame(&mut terminal, &mut output, |frame| {
                    viewports.draw_session(frame, session)
                })?;
                redraw = false;
            }
            // Start the reply deadline after painting, not before expensive syntax initialization.
            if query_theme || viewports.diff_visible {
                let now = Instant::now();
                if query_theme || colors.refresh_due(now) {
                    colors.query(&mut output, now)?;
                    query_theme = false;
                }
            }
            let input = if let Some(input) = pending.take() {
                input
            } else {
                let Some(input) = next_terminal_event(&mut colors, Duration::from_millis(25))?
                else {
                    continue;
                };
                input
            };
            match input {
                Event::Key(key) if key.kind != KeyEventKind::Release => {
                    if session.editor().mode() == Mode::Insert && typing_key(&key) {
                        viewports.panels.follow_files();
                        pending = typing_ready(session, key, || {
                            next_terminal_event(&mut colors, Duration::ZERO)
                        })?;
                        redraw = true;
                    } else if let Some(input) = translate(key) {
                        viewports.panels.follow_files();
                        session.handle(input);
                        redraw = true;
                    }
                }
                Event::Paste(text) => {
                    viewports.panels.follow_files();
                    session.handle(Input::Paste(text));
                    redraw = true;
                }
                Event::Mouse(mouse) => {
                    let (changed, following) = viewports.scroll_ready(session, mouse, || {
                        next_terminal_event(&mut colors, Duration::ZERO)
                    })?;
                    redraw |= changed;
                    pending = following;
                }
                Event::Resize(_, _) => redraw = true,
                Event::FocusGained | Event::ColorSchemeChanged => query_theme = true,
                _ => {}
            }
        }
        Ok(())
    })
}

fn next_terminal_event(
    colors: &mut TerminalColors,
    mut timeout: Duration,
) -> io::Result<Option<Event>> {
    colors.expire(Instant::now());
    if let Some(input) = colors.pop() {
        return Ok(Some(input));
    }
    while event::poll(timeout)? {
        colors.push(event::read()?, Instant::now());
        if let Some(input) = colors.pop() {
            return Ok(Some(input));
        }
        timeout = Duration::ZERO;
    }
    colors.expire(Instant::now());
    Ok(colors.pop())
}

fn typing_key(key: &KeyEvent) -> bool {
    key.kind != KeyEventKind::Release
        && matches!(key.code, KeyCode::Char(ch) if !ch.is_control())
        && !key.modifiers.intersects(
            KeyModifiers::CONTROL
                | KeyModifiers::ALT
                | KeyModifiers::SUPER
                | KeyModifiers::HYPER
                | KeyModifiers::META,
        )
}

// Coalesce frames, not edits: bindings, snippets and history still see each key.
fn typing_ready(
    session: &mut EditorSession,
    mut key: KeyEvent,
    mut next: impl FnMut() -> io::Result<Option<Event>>,
) -> io::Result<Option<Event>> {
    for handled in 1..=64 {
        session.handle(translate(key).expect("plain typing key"));
        if handled == 64
            || session.editor().mode() != Mode::Insert
            || session.editor().should_quit()
        {
            return Ok(None);
        }
        match next()? {
            Some(Event::Key(next)) if typing_key(&next) => key = next,
            pending => return Ok(pending),
        }
    }
    unreachable!()
}

fn translate(key: KeyEvent) -> Option<Input> {
    if key
        .modifiers
        .intersects(KeyModifiers::SUPER | KeyModifiers::HYPER | KeyModifiers::META)
    {
        return None;
    }
    if key.modifiers.contains(KeyModifiers::ALT) {
        return match key.code {
            KeyCode::Char(c) => Some(if key.modifiers.contains(KeyModifiers::CONTROL) {
                Input::CtrlAlt(c.to_ascii_lowercase())
            } else {
                Input::Alt(c.to_ascii_lowercase())
            }),
            _ => None,
        };
    }
    Some(match key.code {
        KeyCode::Char(c) if key.modifiers.contains(KeyModifiers::CONTROL) => {
            Input::Ctrl(c.to_ascii_lowercase())
        }
        KeyCode::Char(c) => Input::Char(c),
        KeyCode::Esc => Input::Escape,
        KeyCode::Enter => Input::Enter,
        KeyCode::Backspace => Input::Backspace,
        KeyCode::Delete => Input::Delete,
        KeyCode::Left => Input::Left,
        KeyCode::Right => Input::Right,
        KeyCode::Up => Input::Up,
        KeyCode::Down => Input::Down,
        KeyCode::Home => Input::Home,
        KeyCode::End => Input::End,
        KeyCode::Tab => Input::Char('\t'),
        KeyCode::BackTab => Input::BackTab,
        _ => return None,
    })
}

fn display_column(line: &str, grapheme_column: usize) -> usize {
    line.graphemes(true)
        .take(grapheme_column)
        .fold(0, |column, grapheme| {
            column
                + if grapheme == "\t" {
                    TAB_WIDTH - column % TAB_WIDTH
                } else {
                    UnicodeWidthStr::width(grapheme)
                }
        })
}

fn visible_line(line: &str, left: usize, width: usize) -> String {
    let mut visible = String::new();
    let mut column = 0;
    let right = left.saturating_add(width);
    for grapheme in line.graphemes(true) {
        let cells = if grapheme == "\t" {
            TAB_WIDTH - column % TAB_WIDTH
        } else {
            UnicodeWidthStr::width(grapheme)
        };
        let end = column + cells;
        if column >= right {
            break;
        }
        if end > left || (cells == 0 && column >= left) {
            if grapheme == "\t" || column < left || end > right {
                for _ in column.max(left)..end.min(right) {
                    visible.push(' ');
                }
            } else {
                visible.push_str(grapheme);
            }
        }
        column = end;
    }
    visible
}

fn diagnostic_severity(severity: DiagnosticSeverity) -> (usize, Color, &'static str) {
    match severity {
        DiagnosticSeverity::Error => (0, Color::Red, "E"),
        DiagnosticSeverity::Warning => (1, Color::Yellow, "W"),
        DiagnosticSeverity::Information => (2, Color::Cyan, "I"),
        DiagnosticSeverity::Hint => (3, Color::DarkGray, "H"),
    }
}

fn diagnostic_on_row(diagnostic: &Diagnostic, row: usize) -> bool {
    diagnostic.start.row <= row
        && row <= diagnostic.end.row
        && (row < diagnostic.end.row
            || diagnostic.end.column > 0
            || diagnostic.start == diagnostic.end)
}

fn draw_tab_bar(frame: &mut Frame, editor: &Editor, area: Rect) -> Rect {
    if editor.tab_count() <= 1 || area.height == 0 {
        return area;
    }
    let bar = Rect::new(area.x, area.y, area.width, 1);
    let workspace = Rect::new(
        area.x,
        area.y.saturating_add(1),
        area.width,
        area.height - 1,
    );
    if bar.width == 0 {
        return workspace;
    }
    let labels: Vec<_> = (0..editor.tab_count())
        .map(|index| {
            let buffer = editor.tab_buffer(index);
            let name = buffer
                .as_ref()
                .and_then(|buffer| buffer.path)
                .map(|path| {
                    path.file_name()
                        .unwrap_or(path.as_os_str())
                        .to_string_lossy()
                })
                .unwrap_or(Cow::Borrowed("[No Name]"));
            display_text(&format!(
                "{}{} {name}{} ",
                if bar.width > 1 { " " } else { "" },
                index + 1,
                if buffer.is_some_and(|buffer| buffer.dirty) {
                    " [+]"
                } else {
                    ""
                },
            ))
        })
        .collect();
    let active = editor.tab_index();
    let mut first = active;
    let fade_width = if active == 0 { 3 } else { 6 };
    let fade = usize::from(bar.width) >= labels[active].width() + fade_width;
    let mut width = labels[active].width() + if fade { fade_width } else { 0 };
    while first > 0 && width + labels[first - 1].width() <= usize::from(bar.width) {
        first -= 1;
        width += labels[first].width();
    }
    let inactive = Style::default().fg(Color::Gray);
    let mut x = bar.x;
    for (index, label) in labels.iter().enumerate().skip(first) {
        let decorated = index == active && fade;
        let width = (label.width() + if decorated { fade_width } else { 0 })
            .min(usize::from(bar.right() - x)) as u16;
        let highlight = Style::default()
            .fg(Color::Black)
            .bg(Color::Cyan)
            .add_modifier(Modifier::BOLD);
        let edge = Style::default().fg(Color::Cyan);
        let line = if decorated {
            Line::from(vec![
                Span::styled(if index == 0 { "" } else { "░▒▓" }, edge),
                Span::styled(label.as_str(), highlight),
                Span::styled("▓▒░", edge),
            ])
        } else {
            Line::from(Span::styled(
                label.as_str(),
                if index == active { highlight } else { inactive },
            ))
        };
        frame.render_widget(Paragraph::new(line), Rect::new(x, bar.y, width, 1));
        x += width;
        if x == bar.right() {
            break;
        }
    }
    workspace
}

fn document_layout(area: Rect, editor: &Editor) -> [Rect; 3] {
    let prompting = matches!(editor.mode(), Mode::Command | Mode::Search);
    let dock_focused = editor
        .file_picker()
        .is_some_and(|picker| picker.focused && picker.presentation == FilePresentation::Docked);
    Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(u16::from(area.height >= 3)),
        Constraint::Length(u16::from(area.height >= 2 || (prompting && !dock_focused))),
    ])
    .areas(area)
}

#[cfg(test)]
fn draw(
    frame: &mut Frame,
    editor: &Editor,
    top: &mut usize,
    left: &mut usize,
    syntax: &mut SyntaxCache,
    document: &mut DocumentViewport,
    panels: &mut WheelPanels,
) {
    let area = frame.area();
    let area = draw_tab_bar(frame, editor, area);
    let areas = if editor.diff().is_some() {
        [area, Rect::default(), Rect::default()]
    } else {
        document_layout(area, editor)
    };
    draw_document(
        frame, editor, areas, area, top, left, syntax, document, panels,
    );
}

#[allow(clippy::too_many_arguments)]
fn draw_document(
    frame: &mut Frame,
    editor: &Editor,
    [workspace, status_area, prompt_area]: [Rect; 3],
    overlay_area: Rect,
    top: &mut usize,
    left: &mut usize,
    syntax: &mut SyntaxCache,
    document: &mut DocumentViewport,
    panels: &mut WheelPanels,
) {
    panels.begin_frame();
    document.geometry = None;
    let area = workspace;
    let focused = editor.render_pane_focused();
    if let Some(diff) = editor.diff() {
        draw_status(frame, editor, syntax, status_area);
        if panels.workspace_managed && diff.phase != Phase::View {
            return;
        }
        draw_diff(
            frame,
            diff,
            area,
            editor.selection_navigation_hint(),
            editor.file_navigation_hint(),
            panels,
            Some(editor),
        );
        return;
    }
    panels.diff_syntax = None;
    if overlay_area.width == 0 || overlay_area.height == 0 {
        return;
    }
    let prompting = matches!(editor.mode(), Mode::Command | Mode::Search);
    let (viewport, dock) = match editor.file_picker() {
        Some(picker)
            if !panels.workspace_managed
                && focused
                && picker.presentation == FilePresentation::Docked =>
        {
            dock_layout(workspace, editor.file_explorer_side(), picker.focused)
        }
        _ => (workspace, None),
    };
    let digits = editor.lines().len().ilog10() as usize + 1;
    let gutter_width = (digits + 1) as u16;
    let [gutter, viewport] = Layout::horizontal([
        Constraint::Length(if viewport.width > gutter_width {
            gutter_width
        } else {
            0
        }),
        Constraint::Fill(1),
    ])
    .areas(viewport);
    let height = usize::from(viewport.height);
    let width = usize::from(viewport.width);
    document.text_width = width;
    let cursor = editor.cursor();
    let mut document_caret = None;
    let carets = editor.carets();
    let selections = editor.selections();
    let wrapped = editor.word_wrap();
    let presentation = (editor.buffer_id(), wrapped, width, height);
    let identity = (editor.buffer_id(), editor.text_revision(), cursor);
    if document.anchor != Some(identity)
        || document
            .presentation
            .is_some_and(|previous| previous.2 != width || previous.3 != height)
    {
        document.anchor = None;
    }
    let toggle_row = document
        .presentation
        .filter(|previous| previous.0 == editor.buffer_id() && previous.1 != wrapped)
        .and_then(|previous| {
            let column = display_column(&editor.lines()[cursor.row], cursor.column);
            let part = if previous.1 {
                caret_segment(
                    document
                        .wrap
                        .segments(cursor.row, &editor.lines()[cursor.row]),
                    column,
                )
            } else {
                0
            };
            document
                .visible
                .iter()
                .position(|&(row, continuation, segment)| {
                    row == cursor.row
                        && continuation == part
                        && (previous.1 || (column >= segment.start && column < segment.end))
                })
        })
        .map(|row| row.min(height.saturating_sub(1)));
    if toggle_row.is_some() {
        document.anchor = Some(identity);
    }
    if document.presentation.is_some_and(|previous| {
        previous.0 != presentation.0
            || previous.1 != wrapped
            || (wrapped && previous != presentation)
    }) {
        document.manual = None;
    }
    document.presentation = Some(presentation);
    document.visible.clear();
    if !focused && let Some(manual) = &mut document.manual {
        // Shared text edits alone must not pull an untouched pane back to its caret.
        manual.revision = editor.text_revision();
        manual.mode = editor.mode();
        manual.cursor = cursor;
        if manual.carets != carets {
            manual.carets.clone_from(&carets);
        }
        if manual.selections != selections {
            manual.selections.clone_from(&selections);
        }
    }
    if document.manual.as_ref().is_some_and(|manual| {
        manual.buffer_id != editor.buffer_id()
            || manual.revision != editor.text_revision()
            || manual.caret_reveal_revision != editor.caret_reveal_revision()
            || manual.mode != editor.mode()
            || manual.cursor != cursor
            || manual.carets != carets
            || manual.selections != selections
    }) {
        document.manual = None;
    }
    document.geometry = Some((
        editor.buffer_id(),
        Rect::new(
            gutter.x,
            viewport.y,
            gutter.width + viewport.width,
            viewport.height,
        ),
    ));
    if !wrapped {
        let limit = if document.anchor.is_some() {
            editor.lines().len() - 1
        } else {
            editor.lines().len().saturating_sub(height)
        };
        *top = (*top).min(limit);
        if let Some(row) = toggle_row {
            *top = cursor.row.saturating_sub(row);
        }
        if document.manual.is_some()
            && let Some((id, revision, columns)) = document.horizontal_extent
            && id == editor.buffer_id()
            && revision == editor.text_revision()
        {
            *left = (*left).min(columns.saturating_add(1).saturating_sub(width.max(1)));
        }
    }
    if height > 0 && width > 0 {
        if wrapped {
            document
                .wrap
                .prepare((editor.buffer_id(), editor.text_revision()), width);
            let continuation = document
                .continuations
                .entry(editor.buffer_id())
                .or_default();
            *top = (*top).min(editor.lines().len() - 1);
            *continuation =
                (*continuation).min(document.wrap.segments(*top, &editor.lines()[*top]).len() - 1);
            let mut start = VisualRow {
                source: *top,
                continuation: *continuation,
            };
            if document.manual.is_none() {
                let column = display_column(&editor.lines()[cursor.row], cursor.column);
                let caret = VisualRow {
                    source: cursor.row,
                    continuation: caret_segment(
                        document
                            .wrap
                            .segments(cursor.row, &editor.lines()[cursor.row]),
                        column,
                    ),
                };
                if let Some(row) = toggle_row {
                    start = caret;
                    for _ in 0..row {
                        let Some(previous) =
                            previous_visual(&mut document.wrap, editor.lines(), start)
                        else {
                            break;
                        };
                        start = previous;
                    }
                } else if caret < start {
                    start = caret;
                } else if caret > visual_page(&mut document.wrap, editor.lines(), start, height).0 {
                    start = caret;
                    for _ in 1..height {
                        let Some(previous) =
                            previous_visual(&mut document.wrap, editor.lines(), start)
                        else {
                            break;
                        };
                        start = previous;
                    }
                }
            }
            if document.anchor.is_none() {
                start = clamp_visual_bottom(&mut document.wrap, editor.lines(), start, height);
            }
            *top = start.source;
            *continuation = start.continuation;
            let mut position = start;
            for _ in 0..height {
                let segment = document
                    .wrap
                    .segments(position.source, &editor.lines()[position.source])
                    [position.continuation];
                document
                    .visible
                    .push((position.source, position.continuation, segment));
                let Some(next) = next_visual(&mut document.wrap, editor.lines(), position) else {
                    break;
                };
                position = next;
            }
        } else {
            if document.manual.is_none() {
                if cursor.row < *top {
                    *top = cursor.row;
                } else if cursor.row >= top.saturating_add(height) {
                    *top = cursor.row + 1 - height;
                }
                let column = display_column(&editor.lines()[cursor.row], cursor.column);
                if column < *left {
                    *left = column;
                } else if column >= left.saturating_add(width) {
                    *left = column + 1 - width;
                }
            }
            document.visible.extend(
                (*top..top.saturating_add(height).min(editor.lines().len())).map(|row| {
                    (
                        row,
                        0,
                        Segment {
                            start: *left,
                            end: left.saturating_add(width),
                        },
                    )
                }),
            );
        }
        let last = document.visible.last().map_or(*top, |(row, _, _)| *row);
        syntax.update_visible(
            editor.lines(),
            editor.path(),
            editor.text_revision(),
            std::slice::from_ref(&(*top..last + 1)),
        );
        if gutter.width > 0 {
            let numbers: Vec<Line> = document
                .visible
                .iter()
                .map(|&(row, continuation, _)| {
                    if continuation > 0 {
                        return Line::default();
                    }
                    let style = if row == cursor.row {
                        Style::default()
                            .fg(Color::Cyan)
                            .add_modifier(Modifier::BOLD)
                    } else {
                        Style::default().fg(Color::DarkGray)
                    };
                    let style = match editor
                        .diagnostics()
                        .filter(|diagnostic| diagnostic_on_row(diagnostic, row))
                        .map(|diagnostic| diagnostic_severity(diagnostic.severity))
                        .min_by_key(|(severity, _, _)| *severity)
                    {
                        Some((_, color, _)) => style.fg(color),
                        None => style,
                    };
                    let number = if row == cursor.row {
                        row + 1
                    } else {
                        row.abs_diff(cursor.row)
                    };
                    Line::styled(format!("{number:>digits$} "), style)
                })
                .collect();
            frame.render_widget(Paragraph::new(numbers), gutter);
        }
        let lines: Vec<Line> = document
            .visible
            .iter()
            .map(|&(row, _, segment)| {
                Line::from(visible_line(
                    &editor.lines()[row],
                    segment.start,
                    segment.end.saturating_sub(segment.start).min(width),
                ))
            })
            .collect();
        frame.render_widget(Paragraph::new(lines), viewport);
        for (screen_row, &(row, continuation, segment)) in document.visible.iter().enumerate() {
            let line = &editor.lines()[row];
            let cells: usize = if wrapped {
                segment
                    .end
                    .saturating_sub(segment.start)
                    .saturating_add(usize::from(
                        continuation + 1 == document.wrap.segments(row, line).len(),
                    ))
                    .min(width)
            } else {
                width
            };
            let area = Rect::new(viewport.x, viewport.y + screen_row as u16, cells as u16, 1);
            paint_syntax_line(frame, line, syntax.line(row), area, segment.start);
            paint_semantic_line(
                frame,
                line,
                editor.semantic_tokens(),
                row,
                area,
                segment.start,
            );
            paint_editor_line(
                frame,
                editor,
                row,
                area,
                segment.start,
                &carets,
                &selections,
            );
        }
    }
    draw_status(frame, editor, syntax, status_area);
    if prompting && prompt_area.height > 0 && prompt_area.width > 0 {
        let prefix = if editor.mode() == Mode::Search {
            '/'
        } else {
            ':'
        };
        let command = format!("{prefix}{}", editor.command_line());
        let command_width = display_column(&command, usize::MAX);
        let prompt_width = usize::from(prompt_area.width);
        let offset = command_width.saturating_sub(prompt_width.saturating_sub(1));
        frame.render_widget(
            Paragraph::new(visible_line(&command, offset, prompt_width)),
            prompt_area,
        );
        if focused && !editor.file_picker().is_some_and(|picker| picker.focused) {
            frame.set_cursor_position((
                prompt_area.x + (command_width - offset) as u16,
                prompt_area.y,
            ));
        }
    } else {
        let message = if let Some(diagnostic) = editor.diagnostic_at_cursor() {
            let (_, _, label) = diagnostic_severity(diagnostic.severity);
            let diagnostic = display_text(&diagnostic.message);
            Cow::Owned(if editor.message().is_empty() {
                format!("{label}: {diagnostic}")
            } else {
                format!("{} | {label}: {diagnostic}", editor.message())
            })
        } else {
            Cow::Borrowed(editor.message())
        };
        frame.render_widget(Paragraph::new(message), prompt_area);
        if height > 0 && width > 0 && !editor.file_picker().is_some_and(|picker| picker.focused) {
            let column = display_column(&editor.lines()[cursor.row], cursor.column);
            let continuation = if wrapped {
                caret_segment(
                    document
                        .wrap
                        .segments(cursor.row, &editor.lines()[cursor.row]),
                    column,
                )
            } else {
                0
            };
            if let Some((screen_row, (_, _, segment))) =
                document
                    .visible
                    .iter()
                    .enumerate()
                    .find(|(_, (row, part, segment))| {
                        *row == cursor.row
                            && *part == continuation
                            && column >= segment.start
                            && column < segment.start.saturating_add(width)
                    })
            {
                let position = Position::new(
                    viewport.x + (column - segment.start) as u16,
                    viewport.y + screen_row as u16,
                );
                if focused {
                    frame.set_cursor_position(position);
                }
                document_caret = Some(position);
            }
        }
    }
    if !focused {
        return;
    }
    panels.caret = document_caret.map(|caret| (viewport, caret));
    if !panels.workspace_managed {
        if let Some(panel) = dock
            && let Some(picker) = editor.file_picker()
        {
            draw_file_list(
                frame,
                picker,
                panel,
                editor.file_navigation_hint(),
                panels,
                None,
            );
        }
        draw_overlays(frame, editor, overlay_area, panels.caret, panels);
    }
}

fn draw_overlays(
    frame: &mut Frame,
    editor: &Editor,
    area: Rect,
    caret: Option<(Rect, Position)>,
    panels: &mut WheelPanels,
) {
    if let Some(completion) = editor.completion()
        && let Some((_, caret)) = caret
    {
        panels.completion = draw_completion(frame, completion, area, caret);
    }
    if let Some(picker) = editor.file_picker()
        && picker.presentation == FilePresentation::Floating
    {
        let panel = floating_panel(area);
        frame.render_widget(Clear, panel);
        draw_file_list(
            frame,
            picker,
            panel,
            editor.file_navigation_hint(),
            panels,
            editor
                .diff()
                .and_then(|diff| diff.comparison.as_ref())
                .map(|comparison| comparison.files.as_slice()),
        );
    }
    if let Some(palette) = editor.palette() {
        draw_palette(
            frame,
            palette,
            area,
            editor.mode(),
            editor.selection_navigation_hint(),
        );
    }
    if let Some(hover) = editor.hover() {
        draw_hover(frame, hover, area, panels);
    }
    if let Some(diagnostic) = editor.startup_diagnostic() {
        draw_startup_diagnostic(frame, diagnostic, area);
    }
}

fn draw_status(frame: &mut Frame, editor: &Editor, syntax: &SyntaxCache, status_area: Rect) {
    if status_area.width == 0 || status_area.height == 0 {
        return;
    }
    let cursor = editor.cursor();
    let path = editor
        .path()
        .map(|p| p.to_string_lossy().into_owned())
        .unwrap_or_else(|| "[No Name]".into());
    let path: String = path
        .chars()
        .map(|c| if c.is_control() { '�' } else { c })
        .collect();
    let mut status = if editor.visual_linewise() {
        " VISUAL LINE".into()
    } else {
        format!(" {}", editor.mode())
    };
    let mode_end = status.len();
    if let Some(sequence) = editor.sequence_pending() {
        write!(status, "  {sequence}").unwrap();
    }
    if editor.g_pending() {
        status.push_str("  g");
    }
    if let Some(operator) = editor.line_operator_pending() {
        write!(status, "  {operator}").unwrap();
    }
    if let Some(seek) = editor.seek_pending() {
        write!(status, "  {seek}").unwrap();
    }
    if editor.buffer_count() > 1 {
        write!(
            status,
            "  [buffer {}/{}]",
            editor.buffer_id(),
            editor.buffer_count()
        )
        .unwrap();
    }
    let mut diagnostic_counts = [0; 4];
    for diagnostic in editor.diagnostics() {
        diagnostic_counts[diagnostic_severity(diagnostic.severity).0] += 1;
    }
    for (label, count) in ["E", "W", "I", "H"].into_iter().zip(diagnostic_counts) {
        if count > 0 {
            write!(status, "  {label}:{count}").unwrap();
        }
    }
    write!(
        status,
        "  {}{}",
        path,
        if editor.dirty() { " [+]" } else { "" },
    )
    .unwrap();
    if editor.selection_count() > 1 {
        write!(status, "  {} selections", editor.selection_count()).unwrap();
    }
    if let Some(count) = editor.count() {
        write!(status, "  count: {count}").unwrap();
    }
    if let Some(error) = syntax.error() {
        write!(status, "  syntax: {error}").unwrap();
    } else if let Some(language) = syntax.language() {
        write!(status, "  {language}").unwrap();
    }
    let highlight = Style::default().fg(Color::Black).bg(Color::Cyan);
    let edge = Style::default().fg(Color::Cyan);
    let position = format!(" {}:{} ", cursor.row + 1, cursor.column + 1);
    let right_width = (position.width() + 3) as u16;
    let show_right = status_area.width >= right_width + 12;
    let left = Rect::new(
        status_area.x,
        status_area.y,
        status_area.width - if show_right { right_width } else { 0 },
        status_area.height,
    );
    frame.render_widget(
        Paragraph::new(Line::from(vec![
            Span::styled(&status[..mode_end], highlight),
            Span::styled("▓▒░", edge),
            Span::raw(&status[mode_end..]),
        ])),
        left,
    );
    if show_right {
        frame.render_widget(
            Paragraph::new(Line::from(vec![
                Span::styled("░▒▓", edge),
                Span::styled(position, highlight),
            ])),
            Rect::new(left.right(), status_area.y, right_width, status_area.height),
        );
    }
}

struct DiffGeometry {
    regions: [(Rect, Focus); 3],
    viewport: Option<(u64, usize, usize, usize, usize)>,
    text_widths: [u16; 2],
    wrapping: bool,
}

fn diff_panel(frame: &mut Frame, area: Rect, title: &str, focused: bool) -> Rect {
    if area.width < 4 || area.height < 4 {
        return area;
    }
    let block = Block::default()
        .borders(Borders::ALL)
        .border_style(Style::default().fg(if focused {
            Color::Cyan
        } else {
            Color::DarkGray
        }))
        .title(title);
    let inner = block.inner(area);
    frame.render_widget(block, area);
    inner
}

fn paint_cells(frame: &mut Frame, area: Rect, left: usize, start: usize, end: usize, style: Style) {
    if area.height == 0 {
        return;
    }
    for column in start.max(left)..end.min(left.saturating_add(usize::from(area.width))) {
        frame.buffer_mut()[(area.x + (column - left) as u16, area.y)].set_style(style);
    }
}

fn paint_grapheme_range(
    frame: &mut Frame,
    area: Rect,
    left: usize,
    line: &str,
    range: std::ops::Range<usize>,
    style: Style,
) {
    let right = left.saturating_add(usize::from(area.width));
    let mut column = 0;
    let mut count = 0;
    for (index, grapheme) in line.graphemes(true).enumerate() {
        let cells = if grapheme == "\t" {
            TAB_WIDTH - column % TAB_WIDTH
        } else {
            UnicodeWidthStr::width(grapheme)
        };
        let next = column + cells;
        if range.contains(&index) && (grapheme == "\t" || (column >= left && next <= right)) {
            paint_cells(frame, area, left, column, next, style);
        }
        column = next;
        count = index + 1;
        if column >= right {
            break;
        }
    }
    if range.start <= count && range.end > count {
        paint_cells(frame, area, left, column, column.saturating_add(1), style);
    }
}

fn paint_semantic_line(
    frame: &mut Frame,
    line: &str,
    semantic: &[SemanticToken],
    row: usize,
    area: Rect,
    left: usize,
) {
    let mut token = semantic.partition_point(|token| token.start.row < row);
    let mut token_style = None;
    let mut column = 0;
    let right = left.saturating_add(usize::from(area.width));
    for (index, grapheme) in line.graphemes(true).enumerate() {
        if column >= right {
            break;
        }
        let cells = if grapheme == "\t" {
            TAB_WIDTH - column % TAB_WIDTH
        } else {
            UnicodeWidthStr::width(grapheme)
        };
        let end = column + cells;
        while token < semantic.len()
            && semantic[token].start.row == row
            && semantic[token].end.column <= index
        {
            token += 1;
            token_style = None;
        }
        if let Some(item) = semantic
            .get(token)
            .filter(|token| token.start.row == row && token.start.column <= index)
            && (grapheme == "\t" || (column >= left && end <= right))
        {
            let style = *token_style.get_or_insert_with(|| semantic_style(item));
            paint_cells(frame, area, left, column, end, style);
        }
        column = end;
    }
}

fn paint_editor_line(
    frame: &mut Frame,
    editor: &Editor,
    row: usize,
    area: Rect,
    left: usize,
    carets: &[Cursor],
    selections: &[Selection],
) {
    let Some(line) = editor.lines().get(row) else {
        return;
    };
    for severity in [
        DiagnosticSeverity::Hint,
        DiagnosticSeverity::Information,
        DiagnosticSeverity::Warning,
        DiagnosticSeverity::Error,
    ] {
        for diagnostic in editor
            .diagnostics()
            .filter(|item| item.severity == severity && diagnostic_on_row(item, row))
        {
            let start = if row == diagnostic.start.row {
                diagnostic.start.column
            } else {
                0
            };
            let end = if row == diagnostic.end.row {
                diagnostic
                    .end
                    .column
                    .saturating_add(usize::from(diagnostic.start == diagnostic.end))
            } else {
                usize::MAX
            };
            let style = Style::default()
                .underline_color(diagnostic_severity(severity).1)
                .add_modifier(Modifier::UNDERLINED);
            paint_grapheme_range(frame, area, left, line, start..end, style);
        }
    }
    if let Some(found) = editor.search_match().filter(|found| found.start.row == row) {
        paint_cells(
            frame,
            area,
            left,
            display_column(line, found.start.column),
            display_column(line, found.end_column),
            Style::default().fg(Color::Black).bg(Color::Yellow),
        );
    }
    let selection_style = Style::default().fg(Color::White).bg(Color::Blue);
    if editor.linewise_rows().any(|rows| rows.contains(&row)) {
        paint_cells(
            frame,
            area,
            left,
            left,
            display_column(line, usize::MAX).saturating_add(1),
            selection_style,
        );
    }
    for selection in selections
        .iter()
        .filter(|_| !editor.visual_linewise())
        .chain(editor.snippet_selections())
    {
        if selection.start.row <= row && row <= selection.end.row {
            let start = if row == selection.start.row {
                display_column(line, selection.start.column)
            } else {
                0
            };
            let end = if row == selection.end.row {
                display_column(line, selection.end.column)
            } else {
                display_column(line, usize::MAX).saturating_add(1)
            };
            paint_cells(frame, area, left, start, end, selection_style);
        }
    }
    for caret in carets.iter().filter(|caret| {
        editor.render_pane_focused() && caret.row == row && **caret != editor.cursor()
    }) {
        let column = display_column(line, caret.column);
        paint_cells(
            frame,
            area,
            left,
            column,
            column.saturating_add(1),
            Style::default().fg(Color::Black).bg(Color::Magenta),
        );
    }
}

fn paint_diff_editor(
    frame: &mut Frame,
    editor: &Editor,
    diff: &DiffState,
    area: Rect,
    focus: Focus,
    viewport: (usize, usize),
    wrapped: Option<&[WrappedDiffRow]>,
) -> Option<Position> {
    let (top, left) = viewport;
    let carets = editor.carets();
    let selections = editor.selections();
    let source_cursor = editor.cursor();
    let cursor_column = display_column(&editor.lines()[source_cursor.row], source_cursor.column);
    let mut cursor = None;
    for (screen, display, segments) in diff_screen_rows(diff, top, area.height, wrapped) {
        let DisplayRow::Line(aligned) = diff.display_rows[display] else {
            continue;
        };
        let Some(source) = (match focus {
            Focus::Before => diff.rows[aligned].before,
            Focus::After => diff.rows[aligned].after,
            Focus::Files => None,
        }) else {
            continue;
        };
        let mut line_area = Rect::new(area.x, area.y + screen as u16, area.width, 1);
        let segment = segments.and_then(|segments| segments[usize::from(focus == Focus::After)]);
        if segments.is_some() && segment.is_none() {
            continue;
        }
        let left = segment.map_or(left, |segment| segment.start);
        if let Some(segment) = segment {
            let final_segment = wrapped.is_some_and(|rows| {
                rows[screen].final_segments[usize::from(focus == Focus::After)]
            });
            line_area.width =
                segment_paint_width(segment, final_segment, usize::from(area.width)) as u16;
        }
        paint_editor_line(frame, editor, source, line_area, left, &carets, &selections);
        if source == source_cursor.row && editor.diff_interacting() {
            let column = cursor_column;
            if column >= left && column < left.saturating_add(usize::from(line_area.width)) {
                cursor = Some(Position::new(area.x + (column - left) as u16, line_area.y));
            }
        }
    }
    if let Some(position) = cursor.filter(|_| editor.render_pane_focused())
        && !matches!(editor.mode(), Mode::Command | Mode::Search)
        && editor.palette().is_none()
    {
        frame.set_cursor_position(position);
    }
    cursor
}

fn draw_diff_popups(
    frame: &mut Frame,
    editor: &Editor,
    area: Rect,
    caret: Option<(Rect, Position)>,
    panels: &mut WheelPanels,
) {
    if !editor.render_pane_focused() {
        return;
    }
    if area.width > 0 && area.height > 0 {
        let footer = Rect::new(area.x, area.bottom() - 1, area.width, 1);
        if matches!(editor.mode(), Mode::Command | Mode::Search) {
            let prefix = if editor.mode() == Mode::Search {
                '/'
            } else {
                ':'
            };
            let command = format!("{prefix}{}", editor.command_line());
            let column = display_column(&command, usize::MAX);
            let offset = column.saturating_sub(usize::from(area.width).saturating_sub(1));
            frame.render_widget(Clear, footer);
            frame.render_widget(
                Paragraph::new(visible_line(&command, offset, usize::from(area.width))),
                footer,
            );
            frame.set_cursor_position((footer.x + (column - offset) as u16, footer.y));
        } else if !editor.message().is_empty() {
            frame.render_widget(Clear, footer);
            frame.render_widget(Paragraph::new(display_text(editor.message())), footer);
        }
    }
    panels.caret = caret;
    if !panels.workspace_managed {
        draw_overlays(frame, editor, area, caret, panels);
    }
}

fn draw_diff_header(frame: &mut Frame, diff: &DiffState, editor: Option<&Editor>, header: Rect) {
    if header.width == 0 || header.height == 0 {
        return;
    }
    let (before, after) = diff.comparison.as_ref().map_or(("", ""), |comparison| {
        (comparison.before.as_str(), comparison.after.as_str())
    });
    frame.render_widget(
        Paragraph::new(format!(
            "Diff · {} → {} · {:?} focus · {}",
            display_text(before),
            display_text(after),
            diff.focus,
            editor
                .filter(|editor| editor.diff_interacting())
                .map_or_else(
                    || "read-only".into(),
                    |editor| format!(
                        "{} · {}{} · {}:{}",
                        if editor.diff_editing() {
                            "editable"
                        } else {
                            "read-only"
                        },
                        if editor.visual_linewise() {
                            "VISUAL LINE".into()
                        } else {
                            editor.mode().to_string()
                        },
                        if editor.dirty() { " [+]" } else { "" },
                        editor.cursor().row + 1,
                        editor.cursor().column + 1,
                    ),
                )
        ))
        .style(Style::default().fg(Color::Black).bg(Color::Cyan)),
        header,
    );
}

fn draw_diff(
    frame: &mut Frame,
    diff: &DiffState,
    area: Rect,
    navigation_hint: &str,
    file_navigation_hint: &str,
    panels: &mut WheelPanels,
    editor: Option<&Editor>,
) {
    let comparison = diff.comparison.as_ref();
    let selected = comparison.and_then(|comparison| comparison.files.get(diff.file));
    if diff.phase != Phase::View || !diff.selected_file_loaded() {
        panels.diff_syntax = None;
    }
    if area.width == 0 || area.height == 0 {
        return;
    }
    if diff.phase != Phase::View {
        let panel = floating_panel(area);
        frame.render_widget(Clear, panel);
        let stage = if diff.phase == Phase::Before {
            "Before"
        } else {
            "After"
        };
        let title = format!(" Diff · Choose {stage} ");
        let content = diff_panel(frame, panel, &title, true);
        let notice = diff.error.as_deref().or_else(|| {
            if diff.loading {
                Some(if diff.after.is_some() {
                    "Loading comparison…"
                } else {
                    "Loading repository…"
                })
            } else {
                diff.catalog
                    .as_ref()
                    .and_then(|catalog| catalog.notice.as_deref())
            }
        });
        let [
            stage_area,
            tabs_area,
            query_area,
            notice_area,
            pinned_area,
            results,
            help,
        ] = Layout::vertical([
            Constraint::Length(u16::from(content.height >= 5)),
            Constraint::Length(u16::from(content.height >= 4)),
            Constraint::Length(1),
            Constraint::Length(u16::from(notice.is_some() && content.height >= 3)),
            Constraint::Length(u16::from(content.height >= 2)),
            Constraint::Fill(1),
            Constraint::Length(u16::from(content.height >= 7)),
        ])
        .areas(content);
        let before = diff
            .before
            .as_ref()
            .map_or("not selected", |revision| revision.label.as_str());
        frame.render_widget(
            Paragraph::new(format!("Choose {stage} · Before: {}", display_text(before))),
            stage_area,
        );
        if let Some(catalog) = &diff.catalog {
            let tabs: Vec<Span> = catalog
                .kind
                .categories()
                .iter()
                .enumerate()
                .map(|(index, category)| {
                    Span::styled(
                        format!(" {} ", category.label()),
                        if index == diff.category {
                            Style::default()
                                .fg(Color::Black)
                                .bg(Color::Cyan)
                                .add_modifier(Modifier::BOLD)
                        } else {
                            Style::default().fg(Color::DarkGray)
                        },
                    )
                })
                .collect();
            frame.render_widget(Paragraph::new(Line::from(tabs)), tabs_area);
        }
        let query = format!("> {}", display_text(&diff.query));
        let width = usize::from(query_area.width);
        let query_width = display_column(&query, usize::MAX);
        let offset = query_width.saturating_sub(width.saturating_sub(1));
        frame.render_widget(
            Paragraph::new(visible_line(&query, offset, width))
                .style(Style::default().fg(Color::Yellow)),
            query_area,
        );
        if query_area.width > 0
            && query_area.height > 0
            && editor.is_none_or(|editor| editor.render_pane_focused())
        {
            frame.set_cursor_position((query_area.x + (query_width - offset) as u16, query_area.y));
        }
        if let Some(notice) = notice {
            frame.render_widget(
                Paragraph::new(display_text(notice)).style(Style::default().fg(
                    if diff.error.is_some() {
                        Color::Red
                    } else {
                        Color::Yellow
                    },
                )),
                notice_area,
            );
        }
        let mut entries = diff.entries();
        if let Some(working) = entries.next() {
            let label = format!(
                "{} {} · pinned",
                if diff.selected == 0 { ">" } else { " " },
                display_text(&working.label)
            );
            frame.render_widget(
                Paragraph::new(visible_line(&label, 0, usize::from(pinned_area.width))).style(
                    if diff.selected == 0 {
                        Style::default()
                            .bg(Color::Blue)
                            .add_modifier(Modifier::BOLD)
                    } else {
                        Style::default().fg(Color::Cyan)
                    },
                ),
                pinned_area,
            );
        }
        let row_height = if results.width >= 50 && results.height >= 4 {
            2
        } else {
            1
        };
        let count = usize::from(results.height) / row_height;
        let first = diff.selected.saturating_sub(count.saturating_sub(1)).max(1);
        let mut lines = Vec::with_capacity(count * row_height);
        for (index, revision) in entries
            .enumerate()
            .map(|(index, revision)| (index + 1, revision))
            .skip(first - 1)
            .take(count)
        {
            let style = if index == diff.selected {
                Style::default()
                    .bg(Color::Blue)
                    .add_modifier(Modifier::BOLD)
            } else {
                Style::default()
            };
            let label = format!(
                "{} {}",
                if index == diff.selected { ">" } else { " " },
                display_text(&revision.label)
            );
            let width = usize::from(results.width);
            if row_height == 2 {
                lines.push(Line::styled(visible_line(&label, 0, width), style));
                lines.push(Line::styled(
                    visible_line(
                        &format!("  {}", display_text(&revision.description)),
                        0,
                        width,
                    ),
                    style.fg(Color::DarkGray),
                ));
            } else {
                lines.push(Line::styled(
                    visible_line(
                        &format!("{label} · {}", display_text(&revision.description)),
                        0,
                        width,
                    ),
                    style,
                ));
            }
        }
        if lines.is_empty() && !diff.loading {
            frame.render_widget(Paragraph::new("No matching revisions"), results);
        } else {
            frame.render_widget(Paragraph::new(lines), results);
        }
        frame.render_widget(
            Paragraph::new(format!(
                "{navigation_hint} · Tab categories · type search · Enter select · Esc back/clear · :diff.close"
            ))
            .style(Style::default().fg(Color::DarkGray)),
            help,
        );
        panels.diff = Some(DiffGeometry {
            regions: [
                (panel, Focus::Files),
                (Rect::default(), Focus::Before),
                (Rect::default(), Focus::After),
            ],
            viewport: None,
            text_widths: [0; 2],
            wrapping: diff.word_wrap,
        });
        if let Some(editor) = editor {
            draw_diff_popups(frame, editor, area, None, panels);
        }
        return;
    }
    frame.render_widget(Clear, area);

    let syntax_error = panels
        .diff_syntax
        .as_ref()
        .and_then(|syntax| syntax.before.error().or_else(|| syntax.after.error()));
    let notice = diff.error.as_deref().or_else(|| {
        if diff.loading {
            Some("Loading file…")
        } else {
            syntax_error.or_else(|| selected.and_then(|file| file.notice.as_deref()))
        }
    });
    let [header, notice_area, workspace, help] = Layout::vertical([
        Constraint::Length(1),
        Constraint::Length(u16::from(notice.is_some() && area.height >= 3)),
        Constraint::Fill(1),
        Constraint::Length(u16::from(area.height >= 3)),
    ])
    .areas(area);
    if !panels.workspace_managed || editor.is_none_or(|editor| editor.pane_layout().len() > 1) {
        draw_diff_header(frame, diff, editor, header);
    }
    if let Some(notice) = notice {
        frame.render_widget(
            Paragraph::new(display_text(notice)).style(Style::default().fg(
                if diff.error.is_some() || syntax_error.is_some() {
                    Color::Red
                } else {
                    Color::Yellow
                },
            )),
            notice_area,
        );
    }
    let (panes, navigator) = if !panels.workspace_managed
        && diff.files_visible
        && diff
            .files
            .as_ref()
            .is_some_and(|files| files.presentation == FilePresentation::Docked)
    {
        dock_layout(workspace, DockSide::Right, diff.focus == Focus::Files)
    } else {
        (workspace, None)
    };
    let pane_layout = diff.pane_layout();
    let [before_area, after_area] = match pane_layout {
        PaneLayout::Split => split_rect(pane_rect(panes), SplitAxis::Vertical).map(terminal_rect),
        PaneLayout::Before | PaneLayout::Empty => [panes, Rect::default()],
        PaneLayout::After => [Rect::default(), panes],
    };
    let mut document_caret = None;
    let mut top = diff.top;
    let mut before_left = diff.left_before;
    let mut after_left = diff.left_after;
    let wrapping = diff.word_wrap;
    let toggle_row = panels
        .previous_diff
        .as_ref()
        .filter(|previous| {
            previous.wrapping != wrapping
                && previous.viewport.is_some_and(|(id, file, _, _, _)| {
                    Some(id) == diff.comparison_id && file == diff.file
                })
        })
        .and_then(|previous| {
            let editor = editor?;
            let focus = editor.diff_buffer_focus()?;
            let cursor = editor.cursor();
            if previous.wrapping {
                let file = selected?;
                let viewport = panels.diff_wrap.as_mut()?;
                let position = viewport.caret_position(diff, file, focus, cursor)?;
                viewport
                    .rows
                    .iter()
                    .position(|row| row.position == position)
            } else {
                let display = diff.source_display_row(focus, cursor.row)?;
                let row = display.checked_sub(previous.viewport?.2)?;
                let side = usize::from(focus == Focus::After) + 1;
                (row < usize::from(diff_inner(previous.regions[side].0).height)).then_some(row)
            }
        });
    if wrapping && let Some(file) = selected.filter(|file| file.loaded) {
        let caret = editor
            .filter(|editor| editor.diff_interacting() && diff.follow_caret)
            .and_then(|editor| {
                editor
                    .diff_buffer_focus()
                    .map(|focus| (focus, editor.cursor()))
            });
        let viewport = panels
            .diff_wrap
            .get_or_insert_with(DiffWrapViewport::default);
        viewport.update(diff, file, [before_area, after_area], caret, toggle_row);
        top = viewport.top.display;
    } else {
        panels.diff_wrap = None;
    }
    if let Some(editor) =
        editor.filter(|editor| !wrapping && editor.diff_interacting() && diff.follow_caret)
        && let Some(focus) = editor.diff_buffer_focus()
    {
        let (pane, left) = match focus {
            Focus::Before => (before_area, &mut before_left),
            Focus::After => (after_area, &mut after_left),
            Focus::Files => unreachable!("native diff buffers belong to a text pane"),
        };
        let height = usize::from(pane.height.saturating_sub(2));
        if let Some(row) = diff.source_display_row(focus, editor.cursor().row) {
            if let Some(anchor) = toggle_row {
                top = row.saturating_sub(anchor.min(height.saturating_sub(1)));
            }
            if row < top {
                top = row;
            } else if height > 0 && row >= top.saturating_add(height) {
                top = row + 1 - height;
            }
        }
        let source_len = selected.map_or(0, |file| match focus {
            Focus::Before => file.before.len(),
            Focus::After => file.after.len(),
            Focus::Files => unreachable!("native buffer belongs to a text pane"),
        });
        let digits = source_len.max(1).ilog10() as usize + 1;
        let content_width = usize::from(pane.width.saturating_sub(2));
        let gutter = if content_width > digits + 2 {
            digits + 2
        } else {
            0
        };
        let width = content_width.saturating_sub(gutter);
        let column = display_column(&editor.lines()[editor.cursor().row], editor.cursor().column);
        if column < *left {
            *left = column;
        } else if width > 0 && column >= left.saturating_add(width) {
            *left = column + 1 - width;
        }
    }
    if let Some(id) = diff.comparison_id
        && let Some(file) = selected.filter(|file| file.loaded)
    {
        let wrapped = panels
            .diff_wrap
            .as_ref()
            .map(|viewport| viewport.rows.as_slice());
        panels
            .diff_syntax
            .get_or_insert_with(DiffSyntaxCache::default)
            .update(
                id,
                diff.file,
                file,
                diff.live_revision,
                Some(DiffSyntaxViewport {
                    diff,
                    top,
                    areas: [before_area, after_area],
                    wrapped,
                }),
            );
    }
    if let Some(picker) = &diff.files
        && let Some(navigator) = navigator
    {
        draw_file_list(
            frame,
            picker,
            navigator,
            file_navigation_hint,
            panels,
            comparison.map(|comparison| comparison.files.as_slice()),
        );
    }
    let mut text_widths = [0; 2];
    let previous_text_widths = panels
        .previous_diff
        .as_ref()
        .filter(|geometry| {
            geometry.viewport.is_some_and(|(id, file, _, _, _)| {
                Some(id) == diff.comparison_id && file == diff.file
            })
        })
        .map(|geometry| geometry.text_widths);
    let wrapped = panels
        .diff_wrap
        .as_ref()
        .map(|viewport| viewport.rows.as_slice());
    if let Some(file) = selected.filter(|file| file.loaded)
        && let Some(syntax) = &panels.diff_syntax
    {
        if pane_layout == PaneLayout::Empty {
            diff_panel(frame, before_area, "", diff.focus == Focus::Before);
        } else {
            if before_area != Rect::default() {
                let text_area = draw_diff_pane(
                    frame,
                    diff,
                    file,
                    before_area,
                    true,
                    &syntax.before,
                    editor.map_or(&[], |editor| editor.diff_semantic_tokens(Focus::Before)),
                    (
                        top,
                        &mut before_left,
                        previous_text_widths.map(|widths| widths[0]),
                    ),
                    wrapped,
                    panels.diff_colors,
                );
                text_widths[0] = text_area.width;
                if let Some(editor) =
                    editor.filter(|editor| editor.diff_buffer_focus() == Some(Focus::Before))
                {
                    document_caret = paint_diff_editor(
                        frame,
                        editor,
                        diff,
                        text_area,
                        Focus::Before,
                        (top, before_left),
                        wrapped,
                    )
                    .map(|position| (text_area, position));
                }
            }
            if after_area != Rect::default() {
                let text_area = draw_diff_pane(
                    frame,
                    diff,
                    file,
                    after_area,
                    false,
                    &syntax.after,
                    editor.map_or(&[], |editor| editor.diff_semantic_tokens(Focus::After)),
                    (
                        top,
                        &mut after_left,
                        previous_text_widths.map(|widths| widths[1]),
                    ),
                    wrapped,
                    panels.diff_colors,
                );
                text_widths[1] = text_area.width;
                if let Some(editor) =
                    editor.filter(|editor| editor.diff_buffer_focus() == Some(Focus::After))
                {
                    document_caret = paint_diff_editor(
                        frame,
                        editor,
                        diff,
                        text_area,
                        Focus::After,
                        (top, after_left),
                        wrapped,
                    )
                    .map(|position| (text_area, position));
                }
            }
        }
    } else {
        frame.render_widget(
            Paragraph::new(if diff.loading {
                "Loading file…"
            } else if selected.is_some() {
                "File details unavailable · select the file to retry"
            } else {
                "No changed files"
            }),
            panes,
        );
    }
    frame.render_widget(
        Paragraph::new(
            "Native buffer bindings · Tab focus · [/] expand above/below in Normal · :diff.close",
        )
        .style(Style::default().fg(Color::DarkGray)),
        help,
    );
    panels.diff = Some(DiffGeometry {
        regions: [
            (navigator.unwrap_or_default(), Focus::Files),
            (before_area, Focus::Before),
            (after_area, Focus::After),
        ],
        viewport: diff
            .comparison_id
            .map(|id| (id, diff.file, top, before_left, after_left)),
        text_widths,
        wrapping,
    });
    if let Some(editor) = editor {
        draw_diff_popups(frame, editor, area, document_caret, panels);
    }
}

fn diff_status(status: FileStatus) -> &'static str {
    match status {
        FileStatus::Added => "A",
        FileStatus::Removed => "D",
        FileStatus::Modified => "M",
        FileStatus::Renamed => "R",
    }
}

#[allow(clippy::too_many_arguments)]
fn draw_diff_pane(
    frame: &mut Frame,
    diff: &DiffState,
    file: &ChangedFile,
    area: Rect,
    before: bool,
    syntax: &SyntaxCache,
    semantic: &[SemanticToken],
    viewport: (usize, &mut usize, Option<u16>),
    wrapped: Option<&[WrappedDiffRow]>,
    colors: DiffColors,
) -> Rect {
    if area.width == 0 || area.height == 0 {
        return area;
    }
    let label = if before { "Before" } else { "After" };
    let path = if before {
        file.old_path.as_ref().unwrap_or(&file.path)
    } else {
        &file.path
    };
    let title = format!(
        " {label} · {} · {} ",
        diff_status(file.status),
        display_text(&path.to_string_lossy())
    );
    let focus = if before { Focus::Before } else { Focus::After };
    let content = diff_panel(frame, area, &title, diff.focus == focus);
    if diff.display_rows.is_empty() {
        frame.render_widget(
            Paragraph::new(file.notice.as_deref().map(display_text).unwrap_or_else(|| {
                if diff.rows.is_empty() {
                    "Empty file"
                } else {
                    "No text changes"
                }
                .into()
            })),
            content,
        );
        return content;
    }
    let source = if before { &file.before } else { &file.after };
    let (top, left, previous_width) = viewport;
    let digits = source.len().max(1).ilog10() as usize + 1;
    let gutter = if usize::from(content.width) > digits + 2 {
        digits + 2
    } else {
        0
    };
    let width = usize::from(content.width).saturating_sub(gutter);
    if wrapped.is_none() && previous_width.is_some_and(|previous| usize::from(previous) != width) {
        *left = diff.bound_horizontal(focus, *left, width);
    }
    let left = *left;
    for (screen, display_row, segments) in diff_screen_rows(diff, top, content.height, wrapped) {
        let row = &diff.display_rows[display_row];
        let row_area = Rect::new(content.x, content.y + screen as u16, content.width, 1);
        let aligned_row = match row {
            DisplayRow::Line(index) => *index,
            DisplayRow::Fold { start, end } => {
                frame.render_widget(
                    Paragraph::new(format!(
                        "… {} unchanged lines hidden · [/] expand context",
                        end - start
                    ))
                    .style(Style::default().fg(Color::DarkGray)),
                    row_area,
                );
                continue;
            }
        };
        let row = &diff.rows[aligned_row];
        let index = if before { row.before } else { row.after };
        let Some(index) = index else {
            let style = Style::default().fg(Color::Rgb(72, 72, 72)).bg(Color::Reset);
            let buffer = frame.buffer_mut();
            for x in 0..content.width {
                buffer[(content.x + x, row_area.y)]
                    .set_symbol("╱")
                    .set_style(style);
            }
            continue;
        };
        let Some(source_text) = source.get(index) else {
            continue;
        };
        let segment = segments.and_then(|segments| segments[usize::from(!before)]);
        if segments.is_some() && segment.is_none() {
            continue;
        }
        let left = segment.map_or(left, |segment| segment.start);
        let text_width = segment.map_or(width, |segment| segment.end - segment.start);
        let paint_width = segment.map_or(width, |segment| {
            let final_segment =
                wrapped.is_some_and(|rows| rows[screen].final_segments[usize::from(!before)]);
            segment_paint_width(segment, final_segment, width)
        });
        let text_area = Rect::new(content.x + gutter as u16, row_area.y, paint_width as u16, 1);
        let changed = matches!(row.kind, RowKind::Changed)
            || (before && row.kind == RowKind::Removed)
            || (!before && row.kind == RowKind::Added);
        let background =
            if changed && !matches!(file.status, FileStatus::Added | FileStatus::Removed) {
                colors.row[usize::from(!before)]
            } else {
                Color::Reset
            };
        let text = if source_text.chars().any(|ch| ch.is_control() && ch != '\t') {
            Cow::Owned(
                source_text
                    .chars()
                    .map(|ch| {
                        if ch.is_control() && ch != '\t' {
                            '�'
                        } else {
                            ch
                        }
                    })
                    .collect::<String>(),
            )
        } else {
            Cow::Borrowed(source_text.as_str())
        };
        frame.render_widget(
            Paragraph::new(visible_line(&text, left, text_width.min(width)))
                .style(Style::default().fg(Color::Reset).bg(background)),
            Rect::new(content.x + gutter as u16, row_area.y, width as u16, 1),
        );
        if gutter > 0 && wrapped.is_none_or(|rows| rows[screen].position.continuation == 0) {
            let marker = if changed {
                if before { '-' } else { '+' }
            } else {
                ' '
            };
            let color = if changed {
                if before { Color::Red } else { Color::Green }
            } else {
                Color::DarkGray
            };
            frame.render_widget(
                Paragraph::new(format!("{:>digits$}{marker} ", index + 1))
                    .style(Style::default().fg(color).bg(background)),
                Rect::new(content.x, row_area.y, gutter as u16, 1),
            );
        }
        paint_syntax_line(frame, source_text, syntax.line(index), text_area, left);
        paint_semantic_line(frame, source_text, semantic, index, text_area, left);
        if !matches!(file.status, FileStatus::Added | FileStatus::Removed) {
            let style = Style::default().bg(colors.character[usize::from(!before)]);
            for change in &row.changes {
                let range = &change[usize::from(!before)];
                if !range.is_empty() {
                    paint_grapheme_range(frame, text_area, left, source_text, range.clone(), style);
                }
            }
        }
    }
    Rect::new(
        content.x + gutter as u16,
        content.y,
        width as u16,
        content.height,
    )
}

fn floating_panel(area: Rect) -> Rect {
    let [_, column, _] = Layout::horizontal([
        Constraint::Fill(1),
        Constraint::Length(area.width.min(100)),
        Constraint::Fill(1),
    ])
    .areas(area);
    let [_, panel, _] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(area.height.min(24)),
        Constraint::Fill(1),
    ])
    .areas(column);
    panel
}

fn draw_startup_diagnostic(frame: &mut Frame, diagnostic: &StartupDiagnostic, area: Rect) {
    let panel = floating_panel(area);
    frame.render_widget(Clear, panel);
    let bordered = panel.width >= 4 && panel.height >= 4;
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .border_style(Style::default().fg(Color::Red))
        .title(" Configuration error ");
    let content = if bordered { block.inner(panel) } else { panel };
    if bordered {
        frame.render_widget(block, panel);
    }
    let [text_area, help_area] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(u16::from(content.height >= 3)),
    ])
    .areas(content);
    let lines: Vec<Line> = diagnostic
        .lines
        .iter()
        .skip(diagnostic.top)
        .take(usize::from(text_area.height))
        .map(|line| {
            let line = display_text(line);
            Line::from(visible_line(
                &line,
                display_column(&line, diagnostic.left),
                usize::from(text_area.width),
            ))
        })
        .collect();
    frame.render_widget(Paragraph::new(lines), text_area);
    frame.render_widget(
        Paragraph::new("Arrows scroll · Home reset · Enter/Esc continue")
            .style(Style::default().fg(Color::DarkGray)),
        help_area,
    );
    if text_area.width > 0 && text_area.height > 0 {
        frame.set_cursor_position((text_area.x, text_area.y));
    }
}

fn segment_paint_width(segment: crate::wrap::Segment, final_segment: bool, width: usize) -> usize {
    let cells = segment.end - segment.start + usize::from(final_segment);
    width.min(cells.max(1))
}

#[derive(Clone, Copy, Debug, Default, Eq, Ord, PartialEq, PartialOrd)]
struct DiffWrapPosition {
    display: usize,
    continuation: usize,
}

#[derive(Clone, Copy)]
struct WrappedDiffRow {
    position: DiffWrapPosition,
    segments: [Option<crate::wrap::Segment>; 2],
    final_segments: [bool; 2],
}

#[derive(Default)]
struct DiffWrapViewport {
    key: Option<(u64, usize, Option<u64>)>,
    revision: u64,
    before: crate::wrap::WrapCache,
    after: crate::wrap::WrapCache,
    widths: [usize; 2],
    top: DiffWrapPosition,
    rows: Vec<WrappedDiffRow>,
}

fn diff_inner(area: Rect) -> Rect {
    if area.width >= 4 && area.height >= 4 {
        Rect::new(area.x + 1, area.y + 1, area.width - 2, area.height - 2)
    } else {
        area
    }
}

fn diff_text_width(area: Rect, source_len: usize) -> usize {
    let width = usize::from(diff_inner(area).width);
    let digits = source_len.max(1).ilog10() as usize + 1;
    width.saturating_sub(if width > digits + 2 { digits + 2 } else { 0 })
}

impl DiffWrapViewport {
    fn row(
        &mut self,
        diff: &DiffState,
        file: &ChangedFile,
        position: DiffWrapPosition,
    ) -> WrappedDiffRow {
        let mut segments = [None; 2];
        let mut final_segments = [false; 2];
        if let Some(DisplayRow::Line(index)) = diff.display_rows.get(position.display) {
            let aligned = &diff.rows[*index];
            for (side, source) in [aligned.before, aligned.after].into_iter().enumerate() {
                if let Some(source) = source.filter(|_| self.widths[side] > 0) {
                    let (cache, lines) = if side == 0 {
                        (&mut self.before, &file.before)
                    } else {
                        (&mut self.after, &file.after)
                    };
                    let text = lines.get(source).map_or("", String::as_str);
                    let parts = cache.segments(source, text);
                    segments[side] = parts.get(position.continuation).copied();
                    final_segments[side] = position.continuation + 1 == parts.len();
                }
            }
        }
        WrappedDiffRow {
            position,
            segments,
            final_segments,
        }
    }

    fn height(&mut self, diff: &DiffState, file: &ChangedFile, display: usize) -> usize {
        let Some(DisplayRow::Line(index)) = diff.display_rows.get(display) else {
            return 1;
        };
        let aligned = &diff.rows[*index];
        let mut height = 1;
        for (side, source) in [aligned.before, aligned.after].into_iter().enumerate() {
            if let Some(source) = source.filter(|_| self.widths[side] > 0) {
                let (cache, lines) = if side == 0 {
                    (&mut self.before, &file.before)
                } else {
                    (&mut self.after, &file.after)
                };
                height = height.max(
                    cache
                        .segments(source, lines.get(source).map_or("", String::as_str))
                        .len(),
                );
            }
        }
        height
    }

    fn step(
        &mut self,
        diff: &DiffState,
        file: &ChangedFile,
        mut position: DiffWrapPosition,
        down: bool,
    ) -> DiffWrapPosition {
        if down {
            if position.continuation + 1 < self.height(diff, file, position.display) {
                position.continuation += 1;
            } else if position.display + 1 < diff.display_rows.len() {
                position.display += 1;
                position.continuation = 0;
            }
        } else if position.continuation > 0 {
            position.continuation -= 1;
        } else if position.display > 0 {
            position.display -= 1;
            position.continuation = self.height(diff, file, position.display) - 1;
        }
        position
    }

    fn fill(&mut self, diff: &DiffState, file: &ChangedFile, height: usize) {
        self.rows.clear();
        if diff.display_rows.is_empty() {
            return;
        }
        let mut position = self.top;
        for _ in 0..height {
            let row = self.row(diff, file, position);
            self.rows.push(row);
            let next = self.step(diff, file, position, true);
            if next == position {
                break;
            }
            position = next;
        }
    }

    fn caret_position(
        &mut self,
        diff: &DiffState,
        file: &ChangedFile,
        focus: Focus,
        cursor: Cursor,
    ) -> Option<DiffWrapPosition> {
        let display = diff.source_display_row(focus, cursor.row)?;
        let (cache, source) = if focus == Focus::Before {
            (&mut self.before, &file.before)
        } else {
            (&mut self.after, &file.after)
        };
        let text = source.get(cursor.row).map_or("", String::as_str);
        let column = display_column(text, cursor.column);
        let continuation = caret_segment(cache.segments(cursor.row, text), column);
        Some(DiffWrapPosition {
            display,
            continuation,
        })
    }

    fn update(
        &mut self,
        diff: &DiffState,
        file: &ChangedFile,
        areas: [Rect; 2],
        caret: Option<(Focus, Cursor)>,
        anchor_row: Option<usize>,
    ) {
        let Some(id) = diff.comparison_id else { return };
        let key = Some((id, diff.file, diff.live_revision));
        if self.key.map(|(id, file, _)| (id, file)) != Some((id, diff.file))
            || self.top.display != diff.top
        {
            self.top = DiffWrapPosition {
                display: diff.top,
                continuation: 0,
            };
        }
        if self.key != key {
            self.key = key;
            self.revision = self
                .revision
                .checked_add(1)
                .expect("wrap revisions exhausted");
        }
        self.widths = [
            diff_text_width(areas[0], file.before.len()),
            diff_text_width(areas[1], file.after.len()),
        ];
        self.before.prepare((diff.file, id), self.widths[0]);
        self.after
            .prepare((diff.file, self.revision), self.widths[1]);
        self.top.display = self
            .top
            .display
            .min(diff.display_rows.len().saturating_sub(1));
        self.top.continuation = self
            .top
            .continuation
            .min(self.height(diff, file, self.top.display) - 1);
        let height = usize::from(diff_inner(areas[0]).height.max(diff_inner(areas[1]).height));
        self.fill(diff, file, height);
        if let Some((focus, cursor)) = caret
            && let Some(position) = self.caret_position(diff, file, focus, cursor)
        {
            if let Some(row) = anchor_row {
                self.top = position;
                for _ in 0..row.min(height.saturating_sub(1)) {
                    self.top = self.step(diff, file, self.top, false);
                }
                self.fill(diff, file, height);
            } else if position < self.top {
                self.top = position;
                self.fill(diff, file, height);
            } else if !self.rows.iter().any(|row| row.position == position) {
                self.top = position;
                for _ in 1..height {
                    self.top = self.step(diff, file, self.top, false);
                }
                self.fill(diff, file, height);
            }
        }
    }
}

fn diff_screen_rows<'a>(
    diff: &'a DiffState,
    top: usize,
    height: u16,
    wrapped: Option<&'a [WrappedDiffRow]>,
) -> impl Iterator<Item = (usize, usize, Option<[Option<crate::wrap::Segment>; 2]>)> + 'a {
    (0..usize::from(height)).filter_map(move |screen| {
        if let Some(rows) = wrapped {
            rows.get(screen)
                .map(|row| (screen, row.position.display, Some(row.segments)))
        } else {
            (top + screen < diff.display_rows.len()).then_some((screen, top + screen, None))
        }
    })
}

struct DiffSyntaxViewport<'a> {
    diff: &'a DiffState,
    top: usize,
    areas: [Rect; 2],
    wrapped: Option<&'a [WrappedDiffRow]>,
}

#[derive(Default)]
struct DiffSyntaxCache {
    key: Option<(u64, usize, Option<u64>)>,
    revision: u64,
    before_revision: u64,
    before: SyntaxCache,
    after: SyntaxCache,
    before_rows: Vec<std::ops::Range<usize>>,
    after_rows: Vec<std::ops::Range<usize>>,
}

impl DiffSyntaxCache {
    fn update(
        &mut self,
        comparison_id: u64,
        file_index: usize,
        file: &ChangedFile,
        live_revision: Option<u64>,
        visible: Option<DiffSyntaxViewport<'_>>,
    ) {
        let key = Some((comparison_id, file_index, live_revision));
        if self.key.map(|(id, index, _)| (id, index)) != Some((comparison_id, file_index)) {
            self.before_revision = self
                .before_revision
                .checked_add(1)
                .expect("diff syntax revisions exhausted");
        }
        if self.key != key {
            self.key = key;
            self.revision = self
                .revision
                .checked_add(1)
                .expect("diff syntax revisions exhausted");
        }
        if let Some(DiffSyntaxViewport {
            diff,
            top,
            areas,
            wrapped,
        }) = visible
        {
            diff_visible_rows(diff, top, areas[0], true, &mut self.before_rows, wrapped);
            diff_visible_rows(diff, top, areas[1], false, &mut self.after_rows, wrapped);
            self.before.update_visible(
                &file.before,
                Some(file.old_path.as_deref().unwrap_or(&file.path)),
                self.before_revision,
                &self.before_rows,
            );
            self.after.update_visible(
                &file.after,
                Some(&file.path),
                self.revision,
                &self.after_rows,
            );
        } else {
            self.before.update(
                &file.before,
                Some(file.old_path.as_deref().unwrap_or(&file.path)),
                self.before_revision,
            );
            self.after
                .update(&file.after, Some(&file.path), self.revision);
        }
    }
}

fn diff_visible_rows(
    diff: &DiffState,
    top: usize,
    pane: Rect,
    before: bool,
    ranges: &mut Vec<std::ops::Range<usize>>,
    wrapped: Option<&[WrappedDiffRow]>,
) {
    ranges.clear();
    let height = if pane.width >= 4 && pane.height >= 4 {
        pane.height - 2
    } else {
        pane.height
    };
    let count = wrapped.map_or(usize::from(height), |rows| {
        rows.last().map_or(0, |row| row.position.display - top + 1)
    });
    for row in diff.display_rows.iter().skip(top).take(count) {
        let DisplayRow::Line(index) = *row else {
            continue;
        };
        let source = if before {
            diff.rows[index].before
        } else {
            diff.rows[index].after
        };
        if let Some(source) = source {
            if let Some(last) = ranges.last_mut()
                && last.end == source
            {
                last.end += 1;
            } else {
                ranges.push(source..source + 1);
            }
        }
    }
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct DiffColors {
    row: [Color; 2],
    character: [Color; 2],
}

impl DiffColors {
    fn new(theme: Option<ThemeColors>) -> Self {
        let Some(theme) = theme else {
            return Self {
                row: [Color::Reset; 2],
                character: [Color::Reset; 2],
            };
        };
        let blend = |tint: [u8; 3], weight: u16| {
            let channels = std::array::from_fn::<_, 3, _>(|index| {
                ((u16::from(theme.background[index]) * (100 - weight)
                    + u16::from(tint[index]) * weight
                    + 50)
                    / 100) as u8
            });
            Color::Rgb(channels[0], channels[1], channels[2])
        };
        Self {
            row: [blend(theme.red, 18), blend(theme.green, 18)],
            character: [blend(theme.red, 38), blend(theme.green, 38)],
        }
    }
}

impl Default for DiffColors {
    fn default() -> Self {
        Self::new(None)
    }
}

#[derive(Default)]
struct WheelPanels {
    workspace_managed: bool,
    caret: Option<(Rect, Position)>,
    completion: Option<Rect>,
    hover: Option<(Rect, usize)>,
    hover_syntax: SyntaxCache,
    files: Option<(Rect, usize, usize)>,
    manual_files: Option<FileWheelOffset>,
    diff: Option<DiffGeometry>,
    diff_colors: DiffColors,
    diff_syntax: Option<DiffSyntaxCache>,
    previous_diff: Option<DiffGeometry>,
    diff_wrap: Option<DiffWrapViewport>,
}

struct FileWheelOffset {
    top: usize,
    root: std::path::PathBuf,
    query: String,
    state: (usize, usize, FilePresentation, FileView, bool, bool),
}

impl FileWheelOffset {
    fn state(picker: &FilePicker) -> (usize, usize, FilePresentation, FileView, bool, bool) {
        (
            picker.selected,
            picker.entries().len(),
            picker.presentation,
            picker.view,
            picker.searching,
            picker.focused,
        )
    }

    fn matches(&self, picker: &FilePicker) -> bool {
        self.state == Self::state(picker) && self.root == picker.root && self.query == picker.query
    }
}

impl WheelPanels {
    fn begin_frame(&mut self) {
        if self.files.is_none() {
            self.manual_files = None;
        }
        self.hover = None;
        self.caret = None;
        self.completion = None;
        self.files = None;
        self.previous_diff = self.diff.take();
    }

    // Keyboard/paste may change the catalog without changing its length.
    fn follow_files(&mut self) {
        self.manual_files = None;
    }

    fn file_top(&mut self, picker: &FilePicker, panel: Rect, height: usize) -> usize {
        if self
            .manual_files
            .as_ref()
            .is_some_and(|offset| !offset.matches(picker))
        {
            self.manual_files = None;
        }
        let count = picker.entries().len();
        let following = picker
            .selected
            .min(count.saturating_sub(1))
            .saturating_sub(height.saturating_sub(1));
        let top = self.manual_files.as_mut().map_or(following, |offset| {
            offset.top = offset.top.min(count.saturating_sub(height.max(1)));
            offset.top
        });
        self.files = Some((panel, height, top));
        top
    }

    // A horizontal report over a popup must not pan the underlying buffer.
    fn scroll(&mut self, session: &mut EditorSession, mouse: MouseEvent) -> bool {
        let Some(kind) = wheel_kind(&mouse) else {
            return false;
        };
        let horizontal = matches!(
            kind,
            MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
        );
        let down = matches!(
            kind,
            MouseEventKind::ScrollDown | MouseEventKind::ScrollRight
        );
        let position = Position::new(mouse.column, mouse.row);
        if horizontal
            && (session.editor().palette().is_some()
                || session.editor().startup_diagnostic().is_some()
                || self.completion.is_some_and(|area| area.contains(position))
                || self.hover.is_some_and(|(area, _)| area.contains(position))
                || self
                    .files
                    .is_some_and(|(area, _, _)| area.contains(position)))
        {
            return true;
        }
        let editor = session.editor();
        if editor.palette().is_some() || editor.startup_diagnostic().is_some() {
            return true;
        }
        let position = ratatui::layout::Position::new(mouse.column, mouse.row);
        if editor.completion().is_some()
            && self
                .completion
                .is_some_and(|panel| panel.contains(position))
        {
            return true;
        }
        if let Some(hover) = editor.hover()
            && let Some((panel, height)) = self.hover
            && panel.contains(position)
        {
            if height > 0 {
                let top = hover.top;
                let target = if down {
                    top.saturating_add(3)
                } else {
                    top.saturating_sub(3)
                }
                .min(hover.lines().len().saturating_sub(height));
                let input = if target < top { Input::Up } else { Input::Down };
                for _ in 0..top.abs_diff(target) {
                    session.handle(input.clone());
                }
            }
            return true;
        }
        let pane = session.editor().pane_id();
        let floating_files = editor.file_picker().is_some_and(|picker| {
            picker.presentation == FilePresentation::Floating
                && self
                    .files
                    .is_some_and(|(area, _, _)| area.contains(position))
        });
        if !floating_files && self.diff.is_some() && self.scroll_comparison(session, mouse, pane) {
            return true;
        }
        let editor = session.editor();
        if let Some(picker) = editor.file_picker()
            && let Some((panel, height, drawn_top)) = self.files
            && panel.contains(position)
        {
            if height > 0 {
                if self
                    .manual_files
                    .as_ref()
                    .is_some_and(|offset| !offset.matches(picker))
                {
                    self.manual_files = None;
                }
                let offset = self.manual_files.get_or_insert_with(|| FileWheelOffset {
                    top: drawn_top,
                    root: picker.root.clone(),
                    query: picker.query.clone(),
                    state: FileWheelOffset::state(picker),
                });
                offset.top = if down {
                    offset.top.saturating_add(3)
                } else {
                    offset.top.saturating_sub(3)
                }
                .min(picker.entries().len().saturating_sub(height));
            }
            return true;
        }
        false
    }

    fn scroll_comparison(
        &mut self,
        session: &mut EditorSession,
        mouse: MouseEvent,
        pane: usize,
    ) -> bool {
        let Some(kind) = wheel_kind(&mouse) else {
            return false;
        };
        let horizontal = matches!(
            kind,
            MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
        );
        let down = matches!(
            kind,
            MouseEventKind::ScrollDown | MouseEventKind::ScrollRight
        );
        let Some(focus) = self.diff.as_ref().and_then(|geometry| {
            geometry.regions.iter().find_map(|(area, focus)| {
                area.contains(Position::new(mouse.column, mouse.row))
                    .then_some(*focus)
            })
        }) else {
            return false;
        };
        let (wrapping, wrapped_viewport) = session.editor_mut().with_render_pane(pane, |editor| {
            let wrapping = editor.word_wrap();
            let viewport = if !horizontal && wrapping && focus != Focus::Files {
                editor.diff().and_then(|diff| {
                    let file = diff.comparison.as_ref()?.files.get(diff.file)?;
                    if !file.loaded {
                        return None;
                    }
                    let id = diff.comparison_id?;
                    let wrap = self.diff_wrap.as_mut()?;
                    for _ in 0..3 {
                        wrap.top = wrap.step(diff, file, wrap.top, down);
                    }
                    Some((
                        id,
                        diff.file,
                        wrap.top.display,
                        diff.left_before,
                        diff.left_after,
                    ))
                })
            } else {
                None
            };
            (wrapping, viewport)
        });
        if horizontal && !wrapping && focus != Focus::Files {
            let width = self.diff.as_ref().unwrap().text_widths[usize::from(focus == Focus::After)];
            if width > 0 {
                session.scroll_diff_horizontal(focus, down, usize::from(width));
            }
        } else if let Some((id, file, top, before, after)) = wrapped_viewport {
            session.scroll_diff(focus, down);
            session.set_diff_viewport(id, file, top, before, after);
        } else if !horizontal {
            for _ in 0..3 {
                session.scroll_diff(focus, down);
            }
        }
        true
    }
}

fn draw_completion(
    frame: &mut Frame,
    completion: &Completion,
    area: Rect,
    caret: Position,
) -> Option<Rect> {
    if area.width == 0 || area.height == 0 || !area.contains(caret) {
        return None;
    }
    let count = completion.items.len().saturating_add(1);
    let selected = completion.selected.min(count - 1);
    let desired_height = count.min(8) as u16;
    let below = area.bottom() - caret.y - 1;
    let above = caret.y - area.y;
    let downward = below >= desired_height || below >= above;
    let height = desired_height.min(if downward { below } else { above }.max(1));
    let first = selected.saturating_sub(usize::from(height) - 1);
    let lines: Vec<Line> = (first..count)
        .take(usize::from(height))
        .map(|index| {
            let label = if index == 0 {
                "Original text".to_owned()
            } else {
                let item = &completion.items[index - 1];
                let mut label = display_text(&item.label);
                if let Some(detail) = &item.detail {
                    label.push_str(" · ");
                    label.push_str(&display_text(detail));
                }
                label
            };
            let style = if index == selected {
                Style::default().fg(Color::Black).bg(Color::Cyan)
            } else {
                Style::default().fg(Color::Gray).bg(Color::Black)
            };
            Line::styled(
                visible_line(&label, 0, usize::from(area.width.min(60))),
                style,
            )
        })
        .collect();
    let width = lines.iter().map(Line::width).max().unwrap_or(1).max(1) as u16;
    let panel = Rect::new(
        caret.x.min(area.right() - width),
        if below == 0 && above == 0 {
            caret.y
        } else if downward {
            caret.y + 1
        } else {
            caret.y - height
        },
        width,
        height,
    );
    frame.render_widget(Clear, panel);
    frame.render_widget(
        Paragraph::new(lines).style(Style::default().fg(Color::Gray).bg(Color::Black)),
        panel,
    );
    Some(panel)
}

fn draw_hover(frame: &mut Frame, hover: &Hover, area: Rect, panels: &mut WheelPanels) {
    if area.width == 0 || area.height == 0 {
        return;
    }
    let [_, column, _] = Layout::horizontal([
        Constraint::Fill(1),
        Constraint::Length(area.width.min(100)),
        Constraint::Fill(1),
    ])
    .areas(area);
    let [_, panel, _] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(
            area.height
                .min(hover.lines().len().saturating_add(3).min(24) as u16),
        ),
        Constraint::Fill(1),
    ])
    .areas(column);
    frame.render_widget(Clear, panel);
    let bordered = panel.height >= 4 && panel.width >= 4;
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .border_style(Style::default().fg(Color::Cyan))
        .title(" Hover ");
    let content = if bordered { block.inner(panel) } else { panel };
    if bordered {
        frame.render_widget(block, panel);
    }
    let [text_area, help_area] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(u16::from(content.height >= 3)),
    ])
    .areas(content);
    panels.hover = Some((panel, usize::from(text_area.height)));
    let lines: Vec<Line> = hover
        .lines()
        .skip(hover.top)
        .take(usize::from(text_area.height))
        .map(|line| {
            Line::from(visible_line(
                line,
                display_column(line, hover.left),
                usize::from(text_area.width),
            ))
        })
        .collect();
    frame.render_widget(Paragraph::new(lines), text_area);
    panels
        .hover_syntax
        .update_text(hover.text(), std::path::Path::new("hover.md"));
    let width = usize::from(text_area.width);
    for (row, line) in hover
        .lines()
        .enumerate()
        .skip(hover.top)
        .take(usize::from(text_area.height))
    {
        let spans = panels.hover_syntax.line(row);
        if spans.is_empty() {
            continue;
        }
        let left = display_column(line, hover.left);
        let right = left.saturating_add(width);
        let mut column = 0;
        let mut span_index = 0;
        for (byte, grapheme) in line.grapheme_indices(true) {
            if column >= right {
                break;
            }
            let cells = if grapheme == "\t" {
                TAB_WIDTH - column % TAB_WIDTH
            } else {
                UnicodeWidthStr::width(grapheme)
            };
            let end = column + cells;
            while span_index < spans.len() && spans[span_index].end_byte <= byte {
                span_index += 1;
            }
            if let Some(span) = spans.get(span_index).filter(|span| span.start_byte <= byte)
                && end > left
                && (grapheme == "\t" || (column >= left && end <= right))
            {
                let style = syntax_style(span.kind);
                let y = text_area.y + (row - hover.top) as u16;
                for cell in column.max(left)..end.min(right) {
                    frame.buffer_mut()[(text_area.x + (cell - left) as u16, y)].set_style(style);
                }
            }
            column = end;
        }
    }
    frame.render_widget(
        Paragraph::new("Arrows/Ctrl+h/j/k/l scroll · Esc close")
            .style(Style::default().fg(Color::DarkGray)),
        help_area,
    );
}

fn dock_layout(area: Rect, side: DockSide, focused: bool) -> (Rect, Option<Rect>) {
    if area.width == 0 || area.height == 0 {
        return (area, None);
    }
    let horizontal = matches!(side, DockSide::Left | DockSide::Right);
    let available = if horizontal { area.width } else { area.height };
    if !focused && available < if horizontal { 24 } else { 8 } {
        return (area, None);
    }
    let extent = if available < if horizontal { 20 } else { 6 } {
        available
    } else if horizontal {
        (available / 3).clamp(12, 38).min(available - 8)
    } else {
        (available / 3).clamp(4, 12).min(available - 2)
    };
    let leading = matches!(side, DockSide::Left | DockSide::Top);
    let constraints = if leading {
        [Constraint::Length(extent), Constraint::Fill(1)]
    } else {
        [Constraint::Fill(1), Constraint::Length(extent)]
    };
    let [first, second] = if horizontal {
        Layout::horizontal(constraints).areas(area)
    } else {
        Layout::vertical(constraints).areas(area)
    };
    if leading {
        (second, Some(first))
    } else {
        (first, Some(second))
    }
}

fn display_text(text: &str) -> String {
    text.chars()
        .map(|ch| if ch.is_control() { '�' } else { ch })
        .collect()
}

fn draw_file_list(
    frame: &mut Frame,
    picker: &FilePicker,
    panel: Rect,
    navigation_hint: &str,
    panels: &mut WheelPanels,
    changed_files: Option<&[ChangedFile]>,
) {
    if panel.width == 0 || panel.height == 0 {
        return;
    }
    let color = if picker.focused {
        Color::Cyan
    } else {
        Color::DarkGray
    };
    let bordered = panel.width >= 4 && panel.height >= 4;
    let browsing = picker.view == FileView::Tree && !picker.searching;
    let title = match (picker.presentation, picker.view, browsing) {
        (FilePresentation::Floating, FileView::List, _) => " Files · List ",
        (FilePresentation::Docked, FileView::List, _) => " Explorer · List ",
        (FilePresentation::Floating, FileView::Tree, true) => " Files · Tree NORMAL ",
        (FilePresentation::Docked, FileView::Tree, true) => " Explorer · Tree NORMAL ",
        (FilePresentation::Floating, FileView::Tree, false) => " Files · Tree INSERT ",
        (FilePresentation::Docked, FileView::Tree, false) => " Explorer · Tree INSERT ",
    };
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .border_style(Style::default().fg(color))
        .title(title);
    let content = if bordered { block.inner(panel) } else { panel };
    if bordered {
        frame.render_widget(block, panel);
    }
    let show_root = content.height >= 4 && !picker.root.as_os_str().is_empty();
    let show_error = picker.error.is_some() && content.height >= 2;
    let show_help = changed_files.is_none() && content.height >= 5 + u16::from(show_error);
    let root = show_root.then(|| {
        Paragraph::new(display_text(&picker.root.to_string_lossy()))
            .style(Style::default().fg(Color::DarkGray))
            .wrap(Wrap { trim: false })
    });
    // Reserve the query, optional notices/footer, and at least one file row.
    let root_rows = root.as_ref().map_or(0, |root| {
        root.line_count(content.width).min(usize::from(
            content
                .height
                .saturating_sub(2 + u16::from(show_error) + u16::from(show_help)),
        )) as u16
    });
    let [query_area, root_area, error_area, results_area, help_area] = Layout::vertical([
        Constraint::Length(1),
        Constraint::Length(root_rows),
        Constraint::Length(u16::from(show_error)),
        Constraint::Fill(1),
        Constraint::Length(u16::from(show_help)),
    ])
    .areas(content);
    let first = panels.file_top(picker, panel, usize::from(results_area.height));
    let query = if browsing && picker.query.is_empty() {
        "i filter · ^U clear · ^T view".into()
    } else if browsing {
        format!("filter: {} · ^U clear", display_text(&picker.query))
    } else {
        format!("> {}", display_text(&picker.query))
    };
    let query_width = display_column(&query, usize::MAX);
    let width = usize::from(query_area.width);
    let offset = if browsing {
        0
    } else {
        query_width.saturating_sub(width.saturating_sub(1))
    };
    frame.render_widget(
        Paragraph::new(visible_line(&query, offset, width)).style(Style::default().fg(
            if picker.focused {
                Color::Yellow
            } else {
                Color::DarkGray
            },
        )),
        query_area,
    );
    if picker.focused
        && query_area.width > 0
        && query_area.height > 0
        && (!browsing || picker.entries().len() == 0 || results_area.height == 0)
    {
        let cursor_x = if browsing { 0 } else { query_width - offset };
        frame.set_cursor_position((query_area.x + cursor_x as u16, query_area.y));
    }
    if let Some(root) = root {
        frame.render_widget(root, root_area);
    }
    if show_error {
        frame.render_widget(
            Paragraph::new(display_text(picker.error.as_deref().unwrap()))
                .style(Style::default().fg(Color::Red)),
            error_area,
        );
    }
    let entries = picker.entries();
    if entries.len() == 0 {
        frame.render_widget(
            Paragraph::new(if picker.query.is_empty() {
                "No project files"
            } else {
                "No matching files"
            }),
            results_area,
        );
    } else if results_area.height > 0 {
        let count = usize::from(results_area.height);
        let selected_index = picker.selected.min(entries.len() - 1);
        let lines: Vec<Line> = entries
            .enumerate()
            .skip(first)
            .take(count)
            .map(|(index, entry)| {
                let selected = index == selected_index;
                let mut style = if entry.is_dir {
                    Style::default().fg(Color::Cyan)
                } else {
                    Style::default()
                };
                if selected {
                    style = style
                        .bg(if picker.focused {
                            Color::Blue
                        } else {
                            Color::DarkGray
                        })
                        .add_modifier(Modifier::BOLD);
                }
                let changed = entry
                    .catalog_index
                    .and_then(|index| changed_files.and_then(|files| files.get(index)));
                let prefix = format!(
                    "{} {:indent$}",
                    if selected { ">" } else { " " },
                    "",
                    indent = if picker.view == FileView::Tree {
                        entry.depth * 2
                    } else {
                        0
                    },
                );
                let mut spans = Vec::with_capacity(if changed.is_some() { 6 } else { 3 });
                spans.push(Span::raw(prefix));
                if let Some(file) = changed {
                    let color = match file.status {
                        FileStatus::Added => Color::Green,
                        FileStatus::Removed => Color::Red,
                        FileStatus::Modified => Color::Yellow,
                        FileStatus::Renamed => Color::Cyan,
                    };
                    spans.push(Span::styled(
                        diff_status(file.status),
                        Style::default().fg(color),
                    ));
                    spans.push(Span::raw(" "));
                }
                if let Some(file) = changed
                    && file.status == FileStatus::Renamed
                    && let Some(old_path) = &file.old_path
                {
                    spans.push(Span::raw(display_text(&old_path.to_string_lossy())));
                    spans.push(Span::raw(" -> "));
                    spans.push(Span::raw(display_text(&file.path.to_string_lossy())));
                } else {
                    spans.push(Span::raw(entry.label));
                    if entry.is_dir && picker.view == FileView::Tree {
                        spans.push(Span::raw("/"));
                    }
                }
                Line::from(spans).style(style)
            })
            .collect();
        frame.render_widget(Paragraph::new(lines), results_area);
        if browsing
            && picker.focused
            && results_area.width > 0
            && selected_index >= first
            && selected_index - first < count
        {
            frame.set_cursor_position((
                results_area.x,
                results_area.y + (selected_index - first) as u16,
            ));
        }
    }
    if !show_help {
        return;
    }
    let help = if picker.focused {
        let controls = match (picker.presentation, browsing) {
            (FilePresentation::Floating, true) => "Enter · i filter · Esc/^W close · ^R · ^T",
            (FilePresentation::Docked, true) => "Enter · i filter · Esc/Tab edit · ^W · ^R · ^T",
            (_, false) if picker.view == FileView::Tree => "Enter · Esc NORMAL · ^W · ^R · ^T",
            (FilePresentation::Floating, false) => "Enter · Esc/^W close · ^R · ^T",
            (FilePresentation::Docked, false) => "Enter · Esc/Tab edit · ^W · ^R · ^T",
        };
        format!("^U clear · {navigation_hint} · {controls}")
    } else {
        "Editor focus · invoke explorer to browse".into()
    };
    frame.render_widget(
        Paragraph::new(help).style(Style::default().fg(Color::DarkGray)),
        help_area,
    );
}

fn draw_palette(
    frame: &mut Frame,
    palette: &Palette,
    area: Rect,
    mode: Mode,
    navigation_hint: &str,
) {
    if area.width == 0 || area.height == 0 {
        return;
    }
    let [_, column, _] = Layout::horizontal([
        Constraint::Fill(1),
        Constraint::Length(area.width.min(100)),
        Constraint::Fill(1),
    ])
    .areas(area);
    let [_, panel, _] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(area.height.min(16)),
        Constraint::Fill(1),
    ])
    .areas(column);
    frame.render_widget(Clear, panel);
    let bordered = panel.height >= 4 && panel.width >= 4;
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .title(format!(" Commands · {mode} "));
    let content = if bordered { block.inner(panel) } else { panel };
    if bordered {
        frame.render_widget(block, panel);
    }
    let [query_area, results_area, help_area] = Layout::vertical([
        Constraint::Length(1),
        Constraint::Fill(1),
        Constraint::Length(u16::from(content.height >= 4)),
    ])
    .areas(content);
    let query = format!("> {}", palette.query);
    let query_width = display_column(&query, usize::MAX);
    let width = usize::from(query_area.width);
    let offset = query_width.saturating_sub(width - 1);
    frame.render_widget(
        Paragraph::new(visible_line(&query, offset, width))
            .style(Style::default().fg(Color::Yellow)),
        query_area,
    );
    frame.set_cursor_position((query_area.x + (query_width - offset) as u16, query_area.y));
    if palette.entries.is_empty() {
        frame.render_widget(Paragraph::new("No matching commands"), results_area);
    } else if results_area.height > 0 {
        let row_height = usize::from(results_area.height >= 2) + 1;
        let count = usize::from(results_area.height) / row_height;
        let first = palette.selected.saturating_sub(count - 1);
        let mut lines = Vec::with_capacity(count * row_height);
        for (index, entry) in palette.entries.iter().enumerate().skip(first).take(count) {
            let mut style = Style::default();
            if !entry.enabled {
                style = style.add_modifier(Modifier::DIM);
            }
            if index == palette.selected {
                style = style.bg(Color::Blue).add_modifier(Modifier::BOLD);
            }
            let bindings = if entry.bindings.is_empty() {
                "unbound".into()
            } else {
                entry.bindings.join(", ")
            };
            let modes = entry
                .modes
                .iter()
                .map(ToString::to_string)
                .collect::<Vec<_>>()
                .join("/");
            let metadata = format!("{} | {bindings} | {modes}", entry.owner);
            let label = format!(
                "{} {} ({})",
                if index == palette.selected { ">" } else { " " },
                entry.label,
                entry.name
            );
            if row_height == 2 {
                lines.push(Line::from(label).style(style));
                lines.push(Line::from(format!("  {metadata}")).style(style));
            } else {
                lines.push(Line::from(format!("{label} | {metadata}")).style(style));
            }
        }
        frame.render_widget(Paragraph::new(lines), results_area);
    }
    frame.render_widget(
        Paragraph::new(format!(
            "{mode} · {navigation_hint} · Enter accept · Esc/Ctrl+p cancel"
        )),
        help_area,
    );
}

fn paint_syntax_line(
    frame: &mut Frame,
    source: &str,
    spans: &[SyntaxSpan],
    area: Rect,
    left: usize,
) {
    if spans.is_empty() || area.width == 0 || area.height == 0 {
        return;
    }
    let right = left.saturating_add(usize::from(area.width));
    let mut span_index = 0;
    let mut column = 0;
    for (byte, grapheme) in source.grapheme_indices(true) {
        if column >= right {
            break;
        }
        let cells = if grapheme == "\t" {
            TAB_WIDTH - column % TAB_WIDTH
        } else {
            UnicodeWidthStr::width(grapheme) + grapheme.chars().filter(|ch| ch.is_control()).count()
        };
        let end = column + cells;
        while span_index < spans.len() && spans[span_index].end_byte <= byte {
            span_index += 1;
        }
        if let Some(span) = spans.get(span_index).filter(|span| span.start_byte <= byte)
            && end > left
            && (grapheme == "\t" || (column >= left && end <= right))
        {
            let style = syntax_style(span.kind);
            for cell in column.max(left)..end.min(right) {
                frame.buffer_mut()[(area.x + (cell - left) as u16, area.y)].set_style(style);
            }
        }
        column = end;
    }
}

fn syntax_style(kind: SyntaxKind) -> Style {
    Style::default().fg(match kind {
        SyntaxKind::Comment => Color::DarkGray,
        SyntaxKind::String => Color::Green,
        SyntaxKind::Keyword => Color::Magenta,
        SyntaxKind::Number => Color::Yellow,
        SyntaxKind::Type | SyntaxKind::Markup => Color::Cyan,
        SyntaxKind::Function => Color::LightBlue,
    })
}

fn semantic_style(token: &SemanticToken) -> Style {
    use SemanticTokenKind::*;
    let readonly = token.modifiers & SemanticTokenModifier::Readonly as u16 != 0;
    let color = match token.kind {
        Namespace => Color::Gray,
        Type | Class | Enum | Interface | Struct | TypeParameter => Color::Cyan,
        Function | Method | Event | Macro => Color::LightBlue,
        Parameter | Variable => Color::LightCyan,
        Property => Color::Blue,
        EnumMember | Number => Color::Yellow,
        Keyword | Modifier | Operator | Decorator => Color::Magenta,
        String | Regexp => Color::Green,
        Comment => Color::DarkGray,
    };
    let mut style = Style::default().fg(color);
    if readonly && matches!(token.kind, Parameter | Variable | Property) {
        style = style.add_modifier(ratatui::style::Modifier::ITALIC);
    }
    if token.modifiers
        & (SemanticTokenModifier::Declaration as u16 | SemanticTokenModifier::Definition as u16)
        != 0
    {
        style = style.add_modifier(ratatui::style::Modifier::BOLD);
    }
    if token.kind == Comment && token.modifiers & SemanticTokenModifier::Documentation as u16 != 0 {
        style = style.add_modifier(ratatui::style::Modifier::ITALIC);
    }
    if token.modifiers & SemanticTokenModifier::Deprecated as u16 != 0 {
        style = style.add_modifier(ratatui::style::Modifier::CROSSED_OUT);
    }
    style
}

#[cfg(test)]
// These fixtures intentionally contain ranges, not lists of indices.
#[allow(clippy::single_range_in_vec_init)]
mod tests {
    use super::*;
    use std::{
        fs,
        path::PathBuf,
        sync::atomic::{AtomicUsize, Ordering},
    };

    struct Directory(PathBuf);

    impl Directory {
        fn new() -> Self {
            static NEXT_ID: AtomicUsize = AtomicUsize::new(0);
            let id = NEXT_ID.fetch_add(1, Ordering::Relaxed);
            let path =
                std::env::temp_dir().join(format!("vamp-tui-test-{}-{id}", std::process::id()));
            fs::create_dir(&path).unwrap();
            Self(path)
        }

        fn file(&self, name: &str, text: &str) -> PathBuf {
            let path = self.0.join(name);
            fs::create_dir_all(path.parent().unwrap()).unwrap();
            fs::write(&path, text).unwrap();
            path
        }
    }

    impl Drop for Directory {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.0);
        }
    }

    fn screen_text(terminal: &Terminal<ratatui::backend::TestBackend>) -> String {
        let buffer = terminal.backend().buffer();
        let area = buffer.area;
        (area.y..area.bottom())
            .map(|y| {
                (area.x..area.right())
                    .map(|x| buffer[(x, y)].symbol())
                    .collect::<String>()
            })
            .collect::<Vec<_>>()
            .join("\n")
    }

    fn diff_catalog() -> crate::diff::Catalog {
        use crate::diff::{Catalog, Category, RepoKind, Revision, RevisionTarget};
        let mut entries = vec![Revision {
            target: RevisionTarget::Working,
            label: "Working checkout".into(),
            description: "On-disk files".into(),
            category: Category::Commits,
        }];
        entries.extend((0..20).map(|index| Revision {
            target: RevisionTarget::Commit(format!("commit-{index:02}")),
            label: format!("commit-{index:02}"),
            description: if index == 19 {
                "needle description".into()
            } else {
                "ordinary change".into()
            },
            category: Category::Commits,
        }));
        entries.push(Revision {
            target: RevisionTarget::Commit("branch-tip".into()),
            label: "feature-branch".into(),
            description: "branch description".into(),
            category: Category::Branches,
        });
        Catalog {
            kind: RepoKind::Git,
            entries,
            notice: None,
        }
    }

    fn syntax_diff_file(path: &str, before: &str, after: &str) -> ChangedFile {
        let before: Vec<String> = before.split('\n').map(str::to_owned).collect();
        let after: Vec<String> = after.split('\n').map(str::to_owned).collect();
        ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: path.into(),
            old_path: None,
            status: FileStatus::Modified,
            hunks: vec![crate::diff::Hunk {
                before_start: 0,
                before_len: before.len(),
                after_start: 0,
                after_len: after.len(),
            }],
            before,
            after,
            notice: None,
        }
    }

    #[test]
    fn diff_syntax_refreshes_same_path_working_snapshots_without_live_buffer_styles() {
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 12)).unwrap();
        let mut panels = WheelPanels::default();
        for (source, foreground) in [
            ("fn main() {}", Color::Magenta),
            ("// current snapshot", Color::DarkGray),
            ("const VALUE: u8 = 3;", Color::Magenta),
        ] {
            let mut diff =
                diff_comparison(vec![syntax_diff_file("working.rs", "fn old() {}", source)]);
            diff.files_visible = false;
            render_diff(&mut terminal, &diff, &mut panels);
            let after = panels.diff.as_ref().unwrap().regions[2].0;
            let cell = &terminal.backend().buffer()[(after.x + 4, after.y + 1)];
            assert_eq!(cell.fg, foreground, "{source}");
            let before = panels.diff.as_ref().unwrap().regions[1].0;
            let cell = &terminal.backend().buffer()[(before.x + 4, before.y + 1)];
            assert_eq!(cell.fg, Color::Magenta);
        }
    }

    #[test]
    fn diff_syntax_uses_each_historic_path_shebang_and_injected_language() {
        let mut file = syntax_diff_file("new.rs", "return 42", "fn main() {}");
        file.old_path = Some("old.py".into());
        let mut syntax = DiffSyntaxCache::default();
        syntax.update(1, 0, &file, None, None);
        assert_eq!(syntax.before.language(), Some("Python"));
        assert_eq!(syntax.after.language(), Some("Rust"));
        assert_eq!(syntax.before.line(0)[0].kind, SyntaxKind::Keyword);
        assert_eq!(syntax.after.line(0)[0].kind, SyntaxKind::Keyword);
        file.path = "unknown.extension".into();
        syntax.update(1, 0, &file, None, None);
        assert_eq!(syntax.after.language(), None);
        assert!(syntax.after.line(0).is_empty());

        let mut file = syntax_diff_file(
            "script",
            "```rust\nfn old() {}\n```",
            "#!/usr/bin/env python3\nreturn 42",
        );
        file.old_path = Some("history.md".into());
        let mut diff = diff_comparison(vec![file]);
        diff.files_visible = false;
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 12)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let syntax = panels.diff_syntax.as_ref().unwrap();
        assert_eq!(syntax.before.language(), Some("Markdown"));
        assert_eq!(syntax.after.language(), Some("Python"));
        assert!(syntax.before.parse_counts().1 > 0);
        assert_eq!(syntax.before.line(1)[0].kind, SyntaxKind::Keyword);
        assert_eq!(syntax.after.line(1)[0].kind, SyntaxKind::Keyword);
        for region in [
            panels.diff.as_ref().unwrap().regions[1].0,
            panels.diff.as_ref().unwrap().regions[2].0,
        ] {
            let cell = &terminal.backend().buffer()[(region.x + 4, region.y + 2)];
            assert_eq!(cell.fg, Color::Magenta);
        }
    }

    #[test]
    fn diff_syntax_parses_selected_snapshots_not_scroll_focus_or_redraw() {
        let first = syntax_diff_file("a.rs", "fn old() {}\n// old", "fn main() {}\n// new");
        let second = syntax_diff_file("b.rs", "// prior file", "// selected file");
        let mut diff = diff_comparison(vec![first, second]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 12)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let syntax = panels.diff_syntax.as_ref().unwrap();
        let counts = (syntax.before.parse_counts(), syntax.after.parse_counts());
        assert_eq!(counts, ((1, 0), (1, 0)));
        for focus in [Focus::Before, Focus::After, Focus::Files] {
            diff.focus = focus;
            diff.top = 1;
            diff.left_before = 1;
            diff.left_after = 2;
            render_diff(&mut terminal, &diff, &mut panels);
            let syntax = panels.diff_syntax.as_ref().unwrap();
            assert_eq!(
                (syntax.before.parse_counts(), syntax.after.parse_counts()),
                counts
            );
            let after = panels.diff.as_ref().unwrap().regions[2].0;
            assert_eq!(
                terminal.backend().buffer()[(after.x + 4, after.y + 1)].fg,
                Color::DarkGray,
            );
        }
        diff.files
            .as_mut()
            .unwrap()
            .reveal_path(std::path::Path::new("b.rs"));
        diff.handle(Input::Enter);
        render_diff(&mut terminal, &diff, &mut panels);
        let syntax = panels.diff_syntax.as_ref().unwrap();
        assert_eq!(syntax.before.parse_counts(), (2, 0));
        assert_eq!(syntax.after.parse_counts(), (2, 0));
        let after = panels.diff.as_ref().unwrap().regions[2].0;
        assert_eq!(
            terminal.backend().buffer()[(after.x + 4, after.y + 1)].fg,
            Color::DarkGray,
        );
        let mut editor = Editor::open(None, vec![]).unwrap();
        let mut views = BufferViewports {
            panels,
            ..BufferViewports::default()
        };
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert!(views.panels.diff_syntax.is_none());
    }

    fn diff_comparison(files: Vec<ChangedFile>) -> DiffState {
        static NEXT_ID: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(1);
        let id = NEXT_ID.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
        let mut diff = DiffState::new();
        diff.take_request();
        diff.apply_result(id, Ok(crate::diff::Outcome::Catalog(diff_catalog())));
        diff.handle(Input::Enter);
        diff.handle(Input::Enter);
        diff.take_request();
        diff.apply_result(
            id,
            Ok(crate::diff::Outcome::Comparison(crate::diff::Comparison {
                root: std::path::PathBuf::new(),
                editable_paths: Default::default(),
                before: "old revision".into(),
                after: "Working checkout".into(),
                files,
            })),
        );
        diff
    }

    fn deletion_file() -> ChangedFile {
        ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "deleted-lines.txt".into(),
            old_path: None,
            status: FileStatus::Modified,
            before: ["keep", "gone", "tail"].map(String::from).to_vec(),
            after: ["keep", "tail"].map(String::from).to_vec(),
            hunks: vec![crate::diff::Hunk {
                before_start: 1,
                before_len: 1,
                after_start: 1,
                after_len: 0,
            }],
            notice: None,
        }
    }
    #[test]
    fn diff_status_layouts_hide_absent_panes_and_leave_unchanged_renames_blank() {
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(160, 12)).unwrap();
        let mut panels = WheelPanels {
            diff_colors: DiffColors::new(Some(LIGHT_DIFF_THEME)),
            ..WheelPanels::default()
        };
        for status in [FileStatus::Added, FileStatus::Removed] {
            let added = status == FileStatus::Added;
            let mut file = deletion_file();
            file.status = status;
            file.before = if added {
                vec![]
            } else {
                vec!["removed content".into()]
            };
            file.after = if added {
                vec!["added content".into()]
            } else {
                vec![]
            };
            file.hunks = vec![crate::diff::Hunk {
                before_start: 0,
                before_len: usize::from(!added),
                after_start: 0,
                after_len: usize::from(added),
            }];
            let mut diff = diff_comparison(vec![file]);
            diff.files_visible = false;
            diff.focus = if added { Focus::After } else { Focus::Before };
            diff.left_after = 2;
            render_diff(&mut terminal, &diff, &mut panels);
            let geometry = panels.diff.as_ref().unwrap();
            let present = geometry.regions[if added { 2 } else { 1 }].0;
            assert_eq!(
                geometry.regions[if added { 1 } else { 2 }].0,
                Rect::default()
            );
            assert_eq!(present.x, 0);
            assert_eq!(present.width, 160);
            assert_eq!(geometry.viewport.unwrap().3, 0);
            assert_eq!(geometry.viewport.unwrap().4, 2);
            assert_eq!(geometry.regions[if added { 2 } else { 1 }].1, diff.focus);
            assert_eq!(
                terminal.backend().buffer()[(present.x, present.y)].fg,
                Color::Cyan
            );
            for x in present.x + 1..present.right() - 1 {
                assert_eq!(
                    terminal.backend().buffer()[(x, present.y + 1)].bg,
                    Color::Reset
                );
            }
            let text = screen_text(&terminal);
            assert!(text.contains(if added {
                "ded content"
            } else {
                "removed content"
            }));
            assert!(text.contains(if added { "After · A" } else { "Before · D" }));
            assert!(!text.contains(if added { "Before ·" } else { "After ·" }));
            assert!(!text.contains('╱'));
        }
        let mut empty_added = deletion_file();
        empty_added.status = FileStatus::Added;
        empty_added.before.clear();
        empty_added.after.clear();
        empty_added.hunks.clear();
        empty_added.notice = Some("metadata-only addition".into());
        let mut diff = diff_comparison(vec![empty_added]);
        diff.files_visible = false;
        diff.focus = Focus::After;
        render_diff(&mut terminal, &diff, &mut panels);
        let geometry = panels.diff.as_ref().unwrap();
        assert_eq!(geometry.regions[1].0, Rect::default());
        assert_eq!(geometry.regions[2].0.width, 160);
        assert!(screen_text(&terminal).contains("metadata-only addition"));

        let mut renamed = deletion_file();
        renamed.status = FileStatus::Renamed;
        renamed.old_path = Some("old/path.txt".into());
        renamed.path = "new/path.txt".into();
        renamed.before = vec!["unchanged rename content".into()];
        renamed.after = renamed.before.clone();
        renamed.hunks.clear();
        let mut diff = diff_comparison(vec![renamed]);
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(screen_text(&terminal).contains("old/path.txt -> new/path.txt"));
        assert_eq!(
            diff.files.as_mut().unwrap().accept(),
            Some("new/path.txt".into())
        );
        diff.files_visible = false;
        render_diff(&mut terminal, &diff, &mut panels);
        let geometry = panels.diff.as_ref().unwrap();
        let blank = geometry.regions[1].0;
        assert_eq!(blank.width, 160);
        assert_eq!(geometry.regions[2].0, Rect::default());
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(blank.x, blank.y)].symbol(), "┌");
        for y in blank.y + 1..blank.bottom() - 1 {
            for x in blank.x + 1..blank.right() - 1 {
                assert_eq!(buffer[(x, y)].symbol(), " ");
                assert_eq!(buffer[(x, y)].bg, Color::Reset);
            }
        }
        let text = screen_text(&terminal);
        assert!(!text.contains("Before ·"));
        assert!(!text.contains("After ·"));
        assert!(!text.contains("unchanged rename content"));
        assert!(!text.contains('╱'));

        let mut modified = diff_comparison(vec![deletion_file()]);
        modified.files_visible = false;
        render_diff(&mut terminal, &modified, &mut panels);
        let regions = panels.diff.as_ref().unwrap().regions;
        assert_eq!(regions[1].0.width, 80);
        assert_eq!(regions[2].0.width, 80);
        let text = screen_text(&terminal);
        assert!(text.contains("Before · M"));
        assert!(text.contains("After · M"));
    }

    fn render_diff(
        terminal: &mut Terminal<ratatui::backend::TestBackend>,
        diff: &DiffState,
        panels: &mut WheelPanels,
    ) {
        terminal
            .draw(|frame| {
                panels.begin_frame();
                draw_diff(frame, diff, frame.area(), "↑/↓", "h/j/k/l", panels, None);
            })
            .unwrap();
    }

    const LIGHT_DIFF_THEME: ThemeColors = ThemeColors {
        background: [250, 245, 240],
        red: [210, 30, 50],
        green: [20, 150, 60],
    };
    const DARK_DIFF_THEME: ThemeColors = ThemeColors {
        background: [20, 25, 30],
        red: [220, 60, 80],
        green: [40, 180, 100],
    };

    #[test]
    fn character_diff_backgrounds_preserve_common_unicode_and_syntax_across_viewports() {
        for theme in [Some(LIGHT_DIFF_THEME), Some(DARK_DIFF_THEME), None] {
            let mut diff = diff_comparison(vec![syntax_diff_file(
                "changes.rs",
                "let 界e\u{301} = old + old;",
                "let 界e\u{301} = new + new;",
            )]);
            diff.files_visible = false;
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
            let mut panels = WheelPanels {
                diff_colors: DiffColors::new(theme),
                ..WheelPanels::default()
            };
            render_diff(&mut terminal, &diff, &mut panels);
            let row = panels.diff_colors.row;
            let character = panels.diff_colors.character;
            if let Some(theme) = theme {
                for (index, accent) in [theme.red, theme.green].into_iter().enumerate() {
                    let Color::Rgb(r, g, b) = row[index] else {
                        panic!("theme row background must be RGB");
                    };
                    let Color::Rgb(cr, cg, cb) = character[index] else {
                        panic!("theme character background must be RGB");
                    };
                    for ((common, changed), (background, accent)) in [r, g, b]
                        .into_iter()
                        .zip([cr, cg, cb])
                        .zip(theme.background.into_iter().zip(accent))
                    {
                        assert!(
                            (background.min(accent)..=background.max(accent)).contains(&common)
                        );
                        assert!(
                            (background.min(accent)..=background.max(accent)).contains(&changed)
                        );
                        if background != accent {
                            assert!(changed.abs_diff(accent) < common.abs_diff(accent));
                        }
                    }
                }
            } else {
                assert_eq!(row, [Color::Reset; 2]);
                assert_eq!(character, [Color::Reset; 2]);
            }
            for index in 0..2 {
                let pane = panels.diff.as_ref().unwrap().regions[index + 1].0;
                let buffer = terminal.backend().buffer();
                for column in [0, 3, 4, 6, 8, 14, 19] {
                    assert_eq!(buffer[(pane.x + 4 + column, pane.y + 1)].bg, row[index]);
                }
                for column in [10, 11, 12, 16, 17, 18] {
                    let cell = &buffer[(pane.x + 4 + column, pane.y + 1)];
                    assert_eq!(cell.bg, character[index]);
                    assert_eq!(cell.fg, Color::Reset);
                }
                assert_eq!(buffer[(pane.x + 4, pane.y + 1)].fg, Color::Magenta);
                assert_eq!(buffer[(pane.x + 8, pane.y + 1)].symbol(), "界");
                assert_eq!(buffer[(pane.x + 10, pane.y + 1)].symbol(), "e\u{301}");
            }
            diff.left_before = 11;
            diff.left_after = 11;
            render_diff(&mut terminal, &diff, &mut panels);
            let after = panels.diff.as_ref().unwrap().regions[2].0;
            let buffer = terminal.backend().buffer();
            assert_eq!(buffer[(after.x + 4, after.y + 1)].symbol(), "e");
            assert_eq!(buffer[(after.x + 4, after.y + 1)].bg, character[1]);
            assert_eq!(buffer[(after.x + 7, after.y + 1)].bg, row[1]);
            diff.word_wrap = true;
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(24, 12)).unwrap();
            render_diff(&mut terminal, &diff, &mut panels);
            let after = panels.diff.as_ref().unwrap().regions[2].0;
            let buffer = terminal.backend().buffer();
            let mut words = 0;
            for y in after.y + 1..after.bottom() - 1 {
                for x in after.x + 4..after.right().saturating_sub(3) {
                    if buffer[(x, y)].symbol() == "n"
                        && buffer[(x + 1, y)].symbol() == "e"
                        && buffer[(x + 2, y)].symbol() == "w"
                    {
                        words += 1;
                        for column in x..x + 3 {
                            assert_eq!(buffer[(column, y)].bg, character[1]);
                            assert_eq!(buffer[(column, y)].fg, Color::Reset);
                        }
                    }
                }
            }
            assert_eq!(words, 2);
        }
    }

    #[test]
    fn diff_picker_keeps_working_pinned_while_windowing_searching_and_changing_stage() {
        let mut diff = DiffState::new();
        diff.take_request();
        diff.apply_result(1, Ok(crate::diff::Outcome::Catalog(diff_catalog())));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 16)).unwrap();
        let mut panels = WheelPanels::default();
        diff.handle(Input::End);
        render_diff(&mut terminal, &diff, &mut panels);
        let text = screen_text(&terminal);
        assert!(text.contains("Choose Before"));
        assert!(text.contains("Working checkout · pinned"));
        assert!(text.contains("> commit-19"));
        assert!(!text.contains("commit-00"));
        for ch in "needle".chars() {
            diff.handle(Input::Char(ch));
        }
        diff.handle(Input::Down);
        render_diff(&mut terminal, &diff, &mut panels);
        let text = screen_text(&terminal);
        assert!(text.contains("> needle"));
        assert!(text.contains("Working checkout · pinned"));
        assert!(text.contains("> commit-19"));
        diff.handle(Input::Enter);
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(screen_text(&terminal).contains("Choose After · Before: commit-19"));
        diff.handle(Input::Escape);
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(screen_text(&terminal).contains("> needle"));
        assert!(screen_text(&terminal).contains("> commit-19"));
        diff.handle(Input::Ctrl('u'));
        diff.handle(Input::Char('\t'));
        render_diff(&mut terminal, &diff, &mut panels);
        let text = screen_text(&terminal);
        assert!(text.contains("feature-branch"));
        assert!(!text.contains("ordinary change"));
        assert!(text.contains("Working checkout · pinned"));
        let buffer = terminal.backend().buffer();
        assert!(
            buffer
                .content
                .iter()
                .any(|cell| cell.symbol() == "B" && cell.bg == Color::Cyan)
        );
    }

    #[test]
    fn diff_excerpts_render_original_lines_and_expand_without_losing_changes() {
        let before: Vec<_> = (0..80)
            .map(|index| format!("let row_{index:03} = {index};"))
            .collect();
        let mut after = before.clone();
        after[30] = "let first_change = 900;".into();
        after[60] = "let second_change = 901;".into();
        let mut diff = diff_comparison(vec![ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "excerpts.rs".into(),
            old_path: None,
            status: FileStatus::Modified,
            before,
            after,
            hunks: [30, 60]
                .map(|index| crate::diff::Hunk {
                    before_start: index,
                    before_len: 1,
                    after_start: index,
                    after_len: 1,
                })
                .into(),
            notice: None,
        }]);
        diff.set_context_options(1, 3);
        diff.files_visible = false;
        diff.focus = Focus::Before;
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(160, 24)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let text = screen_text(&terminal);
        for visible in [
            "30  let row_029",
            "31- let row_030",
            "31+ let first_change",
            "61+ let second_change",
        ] {
            assert!(text.contains(visible), "missing {visible}: {text}");
        }
        for hidden in ["row_028", "row_032", "row_058", "row_062"] {
            assert!(!text.contains(hidden), "unexpected {hidden}: {text}");
        }
        let before_area = panels.diff.as_ref().unwrap().regions[1].0;
        let buffer = terminal.backend().buffer();
        assert_eq!(
            buffer[(before_area.x + 5, before_area.y + 3)].fg,
            Color::Magenta
        );
        diff.handle(Input::Char('['));
        diff.handle(Input::Home);
        render_diff(&mut terminal, &diff, &mut panels);
        let text = screen_text(&terminal);
        assert!(text.contains("row_026"));
        assert!(!text.contains("row_025"));
        assert!(text.contains("first_change"));
        assert!(text.contains("second_change"));
    }

    #[test]
    fn diff_view_aligns_deletion_holes_numbers_colors_and_shared_vertical_scroll() {
        let mut diff = diff_comparison(vec![deletion_file()]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
        let mut panels = WheelPanels {
            diff_colors: DiffColors::new(Some(LIGHT_DIFF_THEME)),
            ..WheelPanels::default()
        };
        render_diff(&mut terminal, &diff, &mut panels);
        let geometry = panels.diff.as_ref().unwrap();
        let before = geometry.regions[1].0;
        let after = geometry.regions[2].0;
        let buffer = terminal.backend().buffer();
        let y = before.y + 2;
        assert_eq!(buffer[(before.x + 4, y)].symbol(), "g");
        assert_eq!(buffer[(before.x + 4, y)].fg, Color::Reset);
        assert_eq!(buffer[(before.x + 2, y)].symbol(), "-");
        for x in before.x + 1..before.right() - 1 {
            assert_eq!(buffer[(x, y + 1)].bg, Color::Reset);
        }
        let gap_symbols: Vec<_> = (after.x + 1..after.right() - 1)
            .map(|x| {
                let cell = &buffer[(x, y)];
                assert_eq!(cell.symbol(), "╱");
                assert_eq!(cell.bg, Color::Reset);
                assert_eq!(cell.fg, Color::Rgb(72, 72, 72));
                cell.symbol().to_owned()
            })
            .collect();
        assert_eq!(buffer[(before.x + 1, y + 1)].symbol(), "3");
        assert_eq!(buffer[(after.x + 1, y + 1)].symbol(), "2");
        assert_eq!(buffer[(before.x + 4, y + 1)].symbol(), "t");
        assert_eq!(buffer[(after.x + 4, y + 1)].symbol(), "t");
        diff.handle(Input::Char('\t'));
        diff.handle(Input::Down);
        render_diff(&mut terminal, &diff, &mut panels);
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(before.x + 4, before.y + 1)].symbol(), "g");
        for (x, symbol) in (after.x + 1..after.right() - 1).zip(gap_symbols) {
            assert_eq!(buffer[(x, after.y + 1)].symbol(), symbol);
        }
        assert_eq!(buffer[(before.x, before.y)].fg, Color::Cyan);
        assert_eq!(buffer[(after.x, after.y)].fg, Color::DarkGray);
        assert!(screen_text(&terminal).contains("Before focus"));
    }

    #[test]
    fn diff_added_rows_hatch_missing_before_but_tint_real_empty_after_lines() {
        let mut diff = diff_comparison(vec![ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "added.txt".into(),
            old_path: None,
            status: FileStatus::Modified,
            before: vec![],
            after: vec!["first addition".into(), String::new()],
            hunks: vec![crate::diff::Hunk {
                before_start: 0,
                before_len: 0,
                after_start: 0,
                after_len: 2,
            }],
            notice: None,
        }]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
        let mut panels = WheelPanels {
            diff_colors: DiffColors::new(Some(LIGHT_DIFF_THEME)),
            ..WheelPanels::default()
        };
        render_diff(&mut terminal, &diff, &mut panels);
        let geometry = panels.diff.as_ref().unwrap();
        let before = geometry.regions[1].0;
        let after = geometry.regions[2].0;
        let buffer = terminal.backend().buffer();
        for offset in 0..2 {
            let y = before.y + 1 + offset;
            for x in before.x + 1..before.right() - 1 {
                let cell = &buffer[(x, y)];
                assert_eq!(cell.symbol(), "╱");
                assert_eq!(cell.bg, Color::Reset);
                assert_eq!(cell.fg, Color::Rgb(72, 72, 72));
            }
            assert_eq!(buffer[(after.x + 1, y)].symbol(), (offset + 1).to_string());
            assert_eq!(buffer[(after.x + 2, y)].symbol(), "+");
            assert_eq!(buffer[(after.x + 2, y)].fg, Color::Green);
            assert_eq!(buffer[(after.x + 4, y)].fg, Color::Reset);
            for x in after.x + 1..after.right() - 1 {
                if offset == 1 && x >= after.x + 4 {
                    assert_eq!(buffer[(x, y)].symbol(), " ");
                }
            }
        }
        diff.top = 1;
        diff.left_before = 1;
        render_diff(&mut terminal, &diff, &mut panels);
        let buffer = terminal.backend().buffer();
        for x in before.x + 1..before.right() - 1 {
            assert_eq!(buffer[(x, before.y + 1)].symbol(), "╱");
        }
        assert_eq!(buffer[(before.x, before.y + 1)].symbol(), "│");
        assert_eq!(buffer[(before.right() - 1, before.y + 1)].symbol(), "│");
    }

    #[test]
    fn diff_changed_backgrounds_preserve_syntax_and_clipped_source_cells() {
        let mut diff = diff_comparison(vec![ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "changed.rs".into(),
            old_path: None,
            status: FileStatus::Modified,
            before: [
                "fn old() {",
                "\tlet word = \"界e\u{301}old\";",
                "\tlet count = 42; //\u{1b}note",
                "",
                "}",
            ]
            .map(String::from)
            .to_vec(),
            after: [
                "fn new() {",
                "\tlet word = \"界e\u{301}new\";",
                "\tlet count = 24; //\u{1b}note",
                "",
                "}",
            ]
            .map(String::from)
            .to_vec(),
            hunks: vec![crate::diff::Hunk {
                before_start: 0,
                before_len: 5,
                after_start: 0,
                after_len: 5,
            }],
            notice: None,
        }]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 12)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let geometry = panels.diff.as_ref().unwrap();
        let before = geometry.regions[1].0;
        let after = geometry.regions[2].0;
        let buffer = terminal.backend().buffer();
        for pane in [before, after] {
            for (column, row, foreground) in [
                (0, 0, Color::Magenta),
                (3, 0, Color::LightBlue),
                (4, 1, Color::Magenta),
                (15, 1, Color::Green),
                (16, 1, Color::Green),
                (18, 1, Color::Green),
                (16, 2, Color::Yellow),
                (22, 2, Color::DarkGray),
                (23, 2, Color::DarkGray),
            ] {
                assert_eq!(
                    buffer[(pane.x + 4 + column, pane.y + 1 + row)].fg,
                    foreground
                );
            }
            assert_eq!(buffer[(pane.x + 20, pane.y + 2)].symbol(), "界");
            assert_eq!(buffer[(pane.x + 22, pane.y + 2)].symbol(), "e\u{301}");
            assert_eq!(buffer[(pane.x + 26, pane.y + 3)].symbol(), "�");
            assert_eq!(buffer[(pane.x + 27, pane.y + 3)].symbol(), "n");
            for x in pane.x + 4..pane.right() - 1 {
                assert_eq!(buffer[(x, pane.y + 4)].symbol(), " ");
                assert_eq!(buffer[(x, pane.y + 4)].fg, Color::Reset);
            }
        }
        diff.top = 1;
        diff.left_before = 17;
        diff.left_after = 16;
        render_diff(&mut terminal, &diff, &mut panels);
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(before.x + 4, before.y + 1)].symbol(), " ");
        assert_eq!(buffer[(before.x + 4, before.y + 1)].fg, Color::Reset);
        assert_eq!(buffer[(before.x + 5, before.y + 1)].symbol(), "e\u{301}");
        assert_eq!(buffer[(before.x + 5, before.y + 1)].fg, Color::Green);
        assert_eq!(buffer[(after.x + 4, after.y + 1)].symbol(), "界");
        assert_eq!(buffer[(after.x + 4, after.y + 1)].fg, Color::Green);
        assert_eq!(buffer[(after.x + 6, after.y + 1)].symbol(), "e\u{301}");
        assert_eq!(buffer[(after.x + 6, after.y + 1)].fg, Color::Green);
    }

    #[test]
    fn diff_view_changes_files_focus_and_keeps_horizontal_offsets_independent() {
        let added = ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "new-name.txt".into(),
            old_path: Some("old-name.txt".into()),
            status: FileStatus::Renamed,
            before: vec!["\t界e\u{301}OLD".into()],
            after: vec!["\t界e\u{301}NEW".into()],
            hunks: vec![crate::diff::Hunk {
                before_start: 0,
                before_len: 1,
                after_start: 0,
                after_len: 1,
            }],
            notice: None,
        };
        let mut diff = diff_comparison(vec![deletion_file(), added]);
        diff.handle(Input::Down);
        diff.handle(Input::Enter);
        for _ in 0..4 {
            diff.handle(Input::Right);
        }
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let text = screen_text(&terminal);
        assert!(text.contains("Before · R · old-name.txt"));
        assert!(text.contains("After · R · new-name.txt"));
        let geometry = panels.diff.as_ref().unwrap();
        let before = geometry.regions[1].0;
        let after = geometry.regions[2].0;
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(before.x + 4, before.y + 1)].symbol(), "界");
        assert_eq!(buffer[(before.x + 6, before.y + 1)].symbol(), "e\u{301}");
        assert_eq!(buffer[(after.x + 4, after.y + 1)].symbol(), " ");
        assert_eq!(buffer[(after.x + 8, after.y + 1)].symbol(), "界");
        assert_eq!(buffer[(after.x + 8, after.y + 1)].fg, Color::Reset);
        diff.handle(Input::Char('\t'));
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(screen_text(&terminal).contains("After focus"));
        assert_eq!(
            terminal.backend().buffer()[(after.x, after.y)].fg,
            Color::Cyan
        );
    }

    #[test]
    fn diff_reuses_right_explorer_compact_tree_and_tracks_browse_focus() {
        let mut leaf = deletion_file();
        leaf.path = "chain/a/b/leaf.txt".into();
        let mut root = deletion_file();
        root.path = "root.txt".into();
        let mut diff = diff_comparison(vec![leaf, root]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 18)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let regions = panels.diff.as_ref().unwrap().regions;
        let navigator = regions[0].0;
        let before = regions[1].0;
        let after = regions[2].0;
        let workspace = Rect::new(0, 1, 120, 16);
        let (panes, dock) = dock_layout(workspace, DockSide::Right, true);
        assert_eq!(Some(navigator), dock);
        assert_eq!(before.x, panes.x);
        assert_eq!(before.right(), after.x);
        assert_eq!(after.right(), navigator.x);
        assert_eq!(navigator.right(), workspace.right());
        assert_eq!(panels.files.unwrap().0, navigator);
        let tree_text = |terminal: &Terminal<ratatui::backend::TestBackend>| {
            let buffer = terminal.backend().buffer();
            (navigator.y..navigator.bottom())
                .map(|y| {
                    (navigator.x..navigator.right())
                        .map(|x| buffer[(x, y)].symbol())
                        .collect::<String>()
                })
                .collect::<Vec<_>>()
                .join("\n")
        };
        let text = tree_text(&terminal);
        assert!(text.contains("Explorer · Tree"));
        assert!(text.contains("chain/a/b/"));
        assert!(text.contains("leaf.txt"));
        assert!(!text.contains("chain/a/b/leaf.txt"));
        let cursor = terminal.get_cursor_position().unwrap();
        assert!(navigator.contains(cursor));
        assert_eq!(
            terminal.backend().buffer()[(cursor.x, cursor.y)].bg,
            Color::Blue
        );
        assert_eq!(
            terminal.backend().buffer()[(navigator.x, navigator.y)].fg,
            Color::Cyan
        );
        diff.handle(Input::Left);
        diff.handle(Input::Enter);
        render_diff(&mut terminal, &diff, &mut panels);
        let text = tree_text(&terminal);
        assert!(!text.contains("leaf.txt"));
        assert!(text.contains("chain/a/b/"));
        assert_eq!(diff.file, 0);
        diff.handle(Input::Char('\t'));
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(!diff.files.as_ref().unwrap().focused);
        assert_eq!(
            terminal.backend().buffer()[(navigator.x, navigator.y)].fg,
            Color::DarkGray
        );
        assert_eq!(
            terminal.backend().buffer()[(before.x, before.y)].fg,
            Color::Cyan
        );
    }

    #[test]
    fn changed_file_markers_follow_catalog_indices_in_every_explorer_view() {
        let files: Vec<_> = [
            ("z.txt", FileStatus::Added),
            ("chain/a/m.txt", FileStatus::Modified),
            ("d.txt", FileStatus::Removed),
            ("r.txt", FileStatus::Renamed),
        ]
        .into_iter()
        .map(|(path, status)| {
            let mut file = deletion_file();
            file.path = path.into();
            file.status = status;
            file.old_path = (status == FileStatus::Renamed).then(|| "old\nname.txt".into());
            file
        })
        .collect();
        let mut picker = FilePicker::from_paths(
            PathBuf::new(),
            files
                .iter()
                .enumerate()
                .map(|(index, file)| (index, file.path.clone())),
        );
        picker.reveal_path(std::path::Path::new("chain/a/m.txt"));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 16)).unwrap();
        for view in [FileView::Tree, FileView::List] {
            picker.set_view(view);
            for focused in [true, false] {
                picker.focused = focused;
                for index in 0..files.len() {
                    picker.reveal_path(&files[index].path);
                    terminal
                        .draw(|frame| {
                            draw_file_list(
                                frame,
                                &picker,
                                frame.area(),
                                "",
                                &mut WheelPanels::default(),
                                Some(&files),
                            );
                        })
                        .unwrap();
                    let buffer = terminal.backend().buffer();
                    for (file, color) in
                        files
                            .iter()
                            .zip([Color::Green, Color::Yellow, Color::Red, Color::Cyan])
                    {
                        let path = if view == FileView::Tree {
                            std::path::Path::new(file.path.file_name().unwrap())
                        } else {
                            file.path.as_path()
                        };
                        let expected = if file.status == FileStatus::Renamed {
                            format!("R old�name.txt -> {}", file.path.to_string_lossy())
                        } else {
                            format!("{} {}", diff_status(file.status), path.to_string_lossy())
                        };
                        let (x, y) = (0..16)
                            .find_map(|y| {
                                let row = (0..100)
                                    .map(|x| buffer[(x, y)].symbol())
                                    .collect::<String>();
                                row.find(&expected).map(|offset| {
                                    (UnicodeWidthStr::width(&row[..offset]) as u16, y)
                                })
                            })
                            .unwrap_or_else(|| panic!("missing {expected}"));
                        assert_eq!(buffer[(x, y)].fg, color);
                    }
                    assert_eq!(picker.accept(), Some(files[index].path.clone()));
                    assert!(picker.query.is_empty());
                }
            }
        }
        // A reverted first file disappears without shifting the remaining status markers.
        picker.replace_paths(
            files
                .iter()
                .enumerate()
                .skip(1)
                .map(|(index, file)| (index, file.path.clone())),
        );
        picker.query = "m.txt".into();
        picker.refilter();
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    &picker,
                    frame.area(),
                    "",
                    &mut WheelPanels::default(),
                    Some(&files),
                );
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("M chain/a/m.txt"));
        assert!(!screen_text(&terminal).contains("R r.txt"));
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    &picker,
                    frame.area(),
                    "",
                    &mut WheelPanels::default(),
                    None,
                );
            })
            .unwrap();
        assert!(!screen_text(&terminal).contains("M chain/a/m.txt"));
    }

    #[test]
    fn hiding_diff_explorer_reclaims_workspace_and_restores_its_geometry() {
        let mut diff = diff_comparison(vec![deletion_file()]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 18)).unwrap();
        let mut panels = WheelPanels::default();
        render_diff(&mut terminal, &diff, &mut panels);
        let original = panels.diff.as_ref().unwrap().regions;
        diff.files_visible = false;
        diff.focus = Focus::Before;
        diff.files.as_mut().unwrap().focused = false;
        render_diff(&mut terminal, &diff, &mut panels);
        let hidden = panels.diff.as_ref().unwrap().regions;
        assert_eq!(hidden[0].0, Rect::default());
        assert!(panels.files.is_none());
        assert_eq!(hidden[1].0.x, 0);
        assert_eq!(hidden[1].0.right(), hidden[2].0.x);
        assert_eq!(hidden[2].0.right(), 120);
        assert!(hidden[1].0.width + hidden[2].0.width > original[1].0.width + original[2].0.width);
        assert!(!screen_text(&terminal).contains("Explorer"));
        diff.files_visible = true;
        diff.focus = Focus::Files;
        diff.files.as_mut().unwrap().focused = true;
        render_diff(&mut terminal, &diff, &mut panels);
        assert_eq!(panels.diff.as_ref().unwrap().regions, original);
        assert_eq!(panels.files.unwrap().0, original[0].0);
    }

    #[test]
    fn diff_notices_empty_comparisons_and_tiny_layouts_remain_renderable() {
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
        let mut panels = WheelPanels::default();
        let mut diff = DiffState::new();
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(screen_text(&terminal).contains("Loading repository"));
        diff.take_request();
        diff.apply_result(1, Err("permission denied".into()));
        render_diff(&mut terminal, &diff, &mut panels);
        assert!(screen_text(&terminal).contains("permission denied"));
        let empty = diff_comparison(vec![]);
        render_diff(&mut terminal, &empty, &mut panels);
        assert!(screen_text(&terminal).contains("No changed files"));
        assert!(screen_text(&terminal).contains("Explorer · Tree"));
        let binary = diff_comparison(vec![ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "image.bin".into(),
            old_path: None,
            status: FileStatus::Added,
            before: vec![],
            after: vec![],
            hunks: vec![],
            notice: Some("Binary file; text comparison unavailable".into()),
        }]);
        render_diff(&mut terminal, &binary, &mut panels);
        assert!(screen_text(&terminal).contains("Binary file"));
        let blank = diff_comparison(vec![ChangedFile {
            loaded: true,
            before_eof: false,
            after_eof: false,
            path: "empty.txt".into(),
            old_path: None,
            status: FileStatus::Added,
            before: vec![],
            after: vec![],
            hunks: vec![],
            notice: None,
        }]);
        render_diff(&mut terminal, &blank, &mut panels);
        assert!(screen_text(&terminal).contains("Empty file"));
        for (width, height) in [(1, 1), (2, 2), (3, 3), (8, 4), (39, 5)] {
            let mut tiny =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            for state in [&diff, &empty, &binary, &blank] {
                render_diff(&mut tiny, state, &mut panels);
                if let Some(geometry) = &panels.diff {
                    for (rect, _) in geometry.regions {
                        assert!(rect.right() <= width && rect.bottom() <= height);
                    }
                    let [navigator, before, after] = geometry.regions.map(|(rect, _)| rect);
                    if before.width > 0 && after.width > 0 {
                        assert!(before.right() <= after.x);
                    }
                    if navigator.width > 0 {
                        assert!(before.right().max(after.right()) <= navigator.x);
                    }
                }
            }
        }
    }

    #[test]
    fn immutable_diff_draw_path_preserves_document_until_explicit_close() {
        let directory = Directory::new();
        let mut editor = Editor::open(
            Some(directory.file("source.txt", "original\nsecond")),
            vec![],
        )
        .unwrap();
        let original = editor.lines().to_vec();
        let cursor = editor.cursor();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        editor.execute("diff");
        let (id, _) = editor.take_diff_request().unwrap();
        editor.apply_diff_result(id, Ok(crate::diff::Outcome::Catalog(diff_catalog())));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("Choose Before"));
        assert!(viewports.document.geometry.is_none());
        editor.handle(Input::Enter);
        editor.handle(Input::Enter);
        let (id, _) = editor.take_diff_request().unwrap();
        editor.apply_diff_result(
            id,
            Ok(crate::diff::Outcome::Comparison(crate::diff::Comparison {
                root: std::path::PathBuf::new(),
                editable_paths: Default::default(),
                before: "old revision".into(),
                after: "Working checkout".into(),
                files: vec![deletion_file()],
            })),
        );
        editor.handle(Input::Paste("must not edit".into()));
        editor.handle(Input::Char('i'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("deleted-lines.txt"));
        assert!(viewports.document.geometry.is_none());
        editor.handle(Input::Escape);
        assert!(editor.diff().is_some());
        editor.execute("diff.close");
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("original"));
        assert!(viewports.document.geometry.is_some());
        assert_eq!(editor.lines(), original);
        assert_eq!(editor.cursor(), cursor);
    }

    fn pane_screen(terminal: &Terminal<ratatui::backend::TestBackend>, area: Rect) -> String {
        let buffer = terminal.backend().buffer();
        (area.y..area.bottom())
            .map(|y| {
                (area.x..area.right())
                    .map(|x| buffer[(x, y)].symbol())
                    .collect::<String>()
            })
            .collect::<Vec<_>>()
            .join("\n")
    }

    #[test]
    fn tab_bar_shows_shared_dirty_titles_and_reserves_document_and_overlay_rows() {
        let directory = Directory::new();
        let mut editor =
            Editor::open(Some(directory.file("a\tname.txt", "DOCUMENT")), vec![]).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 12)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(views.document.geometry.unwrap().1.y, 0);
        assert!(pane_screen(&terminal, Rect::new(0, 0, 80, 1)).contains("DOCUMENT"));

        editor.execute("tab.new");
        editor.handle(Input::Char('i'));
        editor.handle(Input::Paste("changed ".into()));
        editor.handle(Input::Escape);
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        let titles = pane_screen(&terminal, Rect::new(0, 0, 80, 1));
        assert!(titles.contains("1 a�name.txt [+]"), "{titles}");
        assert!(titles.contains("2 a�name.txt [+]"), "{titles}");
        assert_eq!(views.document.geometry.unwrap().1.y, 1);
        assert!(terminal.get_cursor_position().unwrap().y >= 1);
        assert!(pane_screen(&terminal, views.rects[0].1).contains("changed DOCUMENT"));

        editor.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(pane_screen(&terminal, Rect::new(0, 0, 80, 1)), titles);
        assert!(terminal.get_cursor_position().unwrap().y >= 1);
        assert!(screen_text(&terminal).contains("Commands"));
    }

    #[test]
    fn narrow_tab_bar_keeps_the_active_title_visible_and_handles_empty_areas() {
        let directory = Directory::new();
        let mut editor = Editor::open(
            Some(directory.file("a-very-long-inactive-title.txt", "first")),
            vec![],
        )
        .unwrap();
        editor.execute("tab.new");
        editor.execute("tab.new");
        editor.execute(&format!(
            "edit {}",
            directory.file("active.txt", "ACTIVE").display()
        ));
        let mut views = BufferViewports::default();
        for (width, height) in [(12, 9), (7, 9), (1, 9), (0, 9), (12, 1), (12, 0)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| views.draw(frame, &mut editor))
                .unwrap();
            if width > 0 && height > 0 {
                let title = pane_screen(&terminal, Rect::new(0, 0, width, 1));
                assert!(title.trim_start().starts_with('3'), "{title}");
            }
        }

        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.execute("tab.new");
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(40, 6)).unwrap();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        let titles = pane_screen(&terminal, Rect::new(0, 0, 40, 1));
        assert!(titles.contains("1 [No Name]"), "{titles}");
        assert!(titles.contains("2 [No Name]"), "{titles}");
    }

    #[test]
    fn tab_switches_restore_independent_pane_viewports_and_retire_only_closed_panes() {
        let directory = Directory::new();
        let text = (0..80)
            .map(|row| format!("row-{row:02} {}", "long ".repeat(30)))
            .collect::<Vec<_>>()
            .join("\n");
        let mut session =
            EditorSession::open(Some(directory.file("rows.txt", &text)), vec![], None).unwrap();
        let buffer = session.editor().buffer_id();
        session.execute("tab.new");
        let other = session.editor().pane_id();
        session.execute("tab.previous");
        session.execute("pane.split_vertical");
        let split = session.editor().pane_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 24)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        let area = views.rects.iter().find(|(id, _)| *id == split).unwrap().1;
        assert_eq!(area.y, 1);
        assert!(!views.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 2, 0)
        ));
        for _ in 0..2 {
            for kind in [MouseEventKind::ScrollDown, MouseEventKind::ScrollRight] {
                assert!(views.scroll(&mut session, document_wheel(kind, area.x + 2, area.y + 2)));
            }
        }
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        let split_offset = views.offsets[&buffer];
        assert!(split_offset.0 > 0 && split_offset.1 > 0);

        session.execute("tab.next");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(views.rects.len(), 1);
        assert_eq!(views.parked[&split].offsets[&buffer], split_offset);
        for kind in [MouseEventKind::ScrollDown, MouseEventKind::ScrollRight] {
            assert!(views.scroll(&mut session, document_wheel(kind, 2, 2)));
        }
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        let other_offset = views.offsets[&buffer];
        assert_ne!(other_offset, split_offset);

        session.execute("tab.previous");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(session.editor().pane_id(), split);
        assert_eq!(views.rects.len(), 2);
        assert_eq!(views.offsets[&buffer], split_offset);
        assert_eq!(views.parked[&other].offsets[&buffer], other_offset);
        session.execute("tab.next");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(views.offsets[&buffer], other_offset);
        session.execute("tab.close");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(!views.parked.contains_key(&other));
        assert_eq!(views.offsets[&buffer], split_offset);
    }

    #[test]
    fn hidden_tab_diff_caches_do_not_poll_colors_or_report_stale_viewports() {
        let directory = Directory::new();
        let mut session = EditorSession::open(
            Some(directory.file("source.txt", "WORKSPACE")),
            vec![],
            None,
        )
        .unwrap();
        let source = (0..80)
            .map(|row| format!("old-{row:02} {}", "x ".repeat(30)))
            .collect::<Vec<_>>()
            .join("\n");
        install_readonly_diff(
            session.editor_mut(),
            syntax_diff_file("history.txt", &source, &source.replace("old", "new")),
        );
        let owner = session.editor().pane_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 30)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(views.diff_visible);
        let (id, file, _, _, _) = views.panels.diff.as_ref().unwrap().viewport.unwrap();
        session.set_diff_viewport(id, file, 24, 7, 8);
        session.execute("tab.new");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(!views.diff_visible);
        assert!(views.parked[&owner].panels.diff.is_some());
        assert!(views.rects.iter().all(|(id, _)| *id != owner));

        session.execute("tab.previous");
        let diff = session.editor().diff().unwrap();
        assert_eq!((diff.top, diff.left_before, diff.left_after), (24, 7, 8));
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(views.diff_visible);
        assert_eq!(terminal.backend().buffer()[(0, 1)].bg, Color::Cyan);
        assert_eq!(views.panels.files.unwrap().0.y, 2);

        session.execute("diff");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(views.panels.diff.as_ref().unwrap().regions[0].0.y >= 1);
    }

    #[test]
    fn explorer_dock_reserves_space_outside_all_workspace_panes() {
        let directory = Directory::new();
        let mut editor =
            Editor::open(Some(directory.file("shared.txt", "first\nsecond")), vec![]).unwrap();
        editor.set_project_root(directory.0.clone());
        editor.handle(Input::Char('|'));
        editor.handle(Input::Char('_'));
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('e'));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 30)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        let dock = views.panels.files.unwrap().0;
        assert!(views.rects.iter().all(|(_, pane)| pane.right() <= dock.x));
        assert_eq!(dock.right(), 120);
        assert_eq!(dock.y, 0);
        assert_eq!(dock.height, 28);
    }

    #[test]
    fn native_diff_dock_stays_below_the_full_width_header() {
        let mut editor = readonly_diff_editor(deletion_file());
        let mut views = BufferViewports::default();
        for (width, height) in [(120, 30), (32, 9)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| views.draw(frame, &mut editor))
                .unwrap();
            let dock = views.panels.files.unwrap().0;
            let before = views.panels.diff.as_ref().unwrap().regions[1].0;
            assert_eq!(dock.y, before.y);
            assert_eq!(dock.y, 1);
            assert_eq!(dock.right(), width);
            for x in 0..width {
                assert_eq!(terminal.backend().buffer()[(x, 0)].bg, Color::Cyan);
            }
        }
    }

    #[test]
    fn revision_selector_overlays_and_clears_workspace_pane_borders() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.handle(Input::Char('|'));
        editor.execute("diff");
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 30)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("Choose Before"));
        let results = views.panels.diff.as_ref().unwrap().regions[0].0;
        assert!(results.x < 60 && results.right() > 60);
        for x in [59, 60] {
            assert_eq!(terminal.backend().buffer()[(x, 20)].symbol(), " ");
        }
    }

    #[test]
    fn diff_floating_picker_overlays_the_whole_workspace() {
        let directory = Directory::new();
        let mut editor =
            Editor::open(Some(directory.file("source.txt", "workspace")), vec![]).unwrap();
        editor.handle(Input::Char('|'));
        install_readonly_diff(&mut editor, syntax_diff_file("history.txt", "old", "new"));
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('o'));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 30)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(
            views.panels.files.unwrap().0,
            floating_panel(Rect::new(0, 0, 120, 30))
        );
    }

    #[test]
    fn nested_workspace_panes_share_edits_and_undo_but_not_carets() {
        let directory = Directory::new();
        let mut editor = Editor::open(
            Some(directory.file("shared.rs", "fn original() {}\nsecond")),
            vec![],
        )
        .unwrap();
        let root = editor.pane_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(90, 22)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        editor.handle(Input::Char('|'));
        let right = editor.pane_id();
        editor.handle(Input::Char('_'));
        let bottom = editor.pane_id();
        assert_ne!(root, right);
        assert_ne!(right, bottom);
        editor.handle(Input::Right);
        assert_eq!(
            editor.with_render_pane(root, |view| view.cursor()),
            Cursor::default()
        );
        assert_eq!(
            editor.with_render_pane(right, |view| view.cursor()),
            Cursor::default()
        );
        assert_eq!(editor.cursor().column, 1);
        editor.handle(Input::Home);
        editor.handle(Input::Char('i'));
        editor.handle(Input::Paste("SHARED ".into()));
        editor.handle(Input::Escape);
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(views.rects.len(), 3);
        for (_, area) in &views.rects {
            assert!(pane_screen(&terminal, *area).contains("SHARED"));
        }
        let focused = views.rects.iter().find(|(id, _)| *id == bottom).unwrap().1;
        assert!(focused.contains(terminal.get_cursor_position().unwrap()));
        assert_eq!(
            terminal.backend().buffer()[(focused.x, focused.y)].fg,
            Color::Cyan
        );
        assert_eq!(views.syntax.len(), 1);
        editor.handle(Input::Char('u'));
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert!(!screen_text(&terminal).contains("SHARED"));
        editor.execute("pane.close");
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(views.rects.len(), 2);
        assert!(!views.parked.contains_key(&bottom));
    }

    #[test]
    fn wheel_targets_inactive_workspace_pane_and_split_inherits_offsets() {
        let directory = Directory::new();
        let text = (0..80)
            .map(|row| format!("row-{row:02} {}", "long ".repeat(30)))
            .collect::<Vec<_>>()
            .join("\n");
        let mut session =
            EditorSession::open(Some(directory.file("rows.txt", &text)), vec![], None).unwrap();
        let root = session.editor().pane_id();
        let buffer = session.editor().buffer_id();
        for _ in 0..3 {
            session.handle(Input::Right);
        }
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 20)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(views.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 2, 1)
        ));
        session.handle(Input::Char('|'));
        let focused = session.editor().pane_id();
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(views.offsets[&buffer], views.parked[&root].offsets[&buffer]);
        let focused_offset = views.offsets[&buffer];
        let root_area = views.rects.iter().find(|(id, _)| *id == root).unwrap().1;
        let cursor = session.editor().cursor();
        assert!(views.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, root_area.x + 2, root_area.y + 2)
        ));
        assert!(views.scroll(
            &mut session,
            document_wheel(
                MouseEventKind::ScrollRight,
                root_area.x + 2,
                root_area.y + 2
            )
        ));
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(session.editor().pane_id(), focused);
        assert_eq!(session.editor().cursor(), cursor);
        assert_eq!(views.offsets[&buffer], focused_offset);
        assert!(views.parked[&root].offsets[&buffer].0 > focused_offset.0);
        assert!(views.parked[&root].offsets[&buffer].1 > focused_offset.1);
        let inactive_offset = views.parked[&root].offsets[&buffer];
        let inactive_cursor = session
            .editor_mut()
            .with_render_pane(root, |view| view.cursor());
        // Even a motion that leaves the focused caret in place requests reveal.
        session.handle(Input::Home);
        session.handle(Input::Home);
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(views.parked[&root].offsets[&buffer], inactive_offset);
        session.handle(Input::Down);
        session.handle(Input::End);
        session.handle(Input::Char('i'));
        session.handle(Input::Paste(" typed".into()));
        session.handle(Input::Escape);
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(
            session
                .editor_mut()
                .with_render_pane(root, |view| view.cursor()),
            inactive_cursor
        );
        assert_eq!(views.parked[&root].offsets[&buffer], inactive_offset);
        session.handle(Input::Up);
        session.handle(Input::Home);
        session.handle(Input::Char('i'));
        session.handle(Input::Paste("PREFIX ".into()));
        session.handle(Input::Escape);
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        let rebased = session
            .editor_mut()
            .with_render_pane(root, |view| view.cursor());
        assert_eq!(rebased.row, inactive_cursor.row);
        assert!(rebased.column > inactive_cursor.column);
        assert_eq!(views.parked[&root].offsets[&buffer], inactive_offset);
        let focused_after_typing = views.offsets[&buffer];
        session.handle(Input::Alt('h'));
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(session.editor().pane_id(), root);
        assert!(views.offsets[&buffer].0 > focused_offset.0);
        assert_eq!(
            views.parked[&focused].offsets[&buffer],
            focused_after_typing
        );
    }

    #[test]
    fn wrapped_workspace_panes_scroll_independently_and_keep_toggle_anchor() {
        let directory = Directory::new();
        let text = (0..40)
            .map(|row| format!("row-{row:02} {}", "word ".repeat(35)))
            .collect::<Vec<_>>()
            .join("\n");
        let mut session =
            EditorSession::open(Some(directory.file("wrap.txt", &text)), vec![], None).unwrap();
        session.execute("word_wrap.toggle");
        let root = session.editor().pane_id();
        let buffer = session.editor().buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(70, 24)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(views.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 2, 1)
        ));
        session.handle(Input::Char('|'));
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        let inherited = (
            views.offsets[&buffer].0,
            views.document.continuations[&buffer],
        );
        assert_eq!(
            inherited,
            (
                views.parked[&root].offsets[&buffer].0,
                views.parked[&root].document.continuations[&buffer]
            )
        );
        let root_area = views.rects.iter().find(|(id, _)| *id == root).unwrap().1;
        assert!(views.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, root_area.x + 2, root_area.y + 2)
        ));
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(
            (
                views.offsets[&buffer].0,
                views.document.continuations[&buffer]
            ),
            inherited
        );
        assert_ne!(
            (
                views.parked[&root].offsets[&buffer].0,
                views.parked[&root].document.continuations[&buffer]
            ),
            inherited
        );
        session.handle(Input::Right);
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        let caret = terminal.get_cursor_position().unwrap();
        session.execute("word_wrap.toggle");
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(terminal.get_cursor_position().unwrap().y, caret.y);
    }

    #[test]
    fn comparison_owner_coexists_with_workspace_and_inactive_diff_wheel_keeps_focus() {
        let directory = Directory::new();
        let mut session = EditorSession::open(
            Some(directory.file("source.txt", "WORKSPACE\nsecond")),
            vec![],
            None,
        )
        .unwrap();
        let source = (0..80)
            .map(|row| format!("old-{row:02} {}", "x ".repeat(30)))
            .collect::<Vec<_>>()
            .join("\n");
        let after = source.replace("old", "new");
        let workspace = session.editor().buffer_id();
        install_readonly_diff(
            session.editor_mut(),
            syntax_diff_file("history.txt", &source, &after),
        );
        let owner = session.editor().pane_id();
        session.execute("pane.split_horizontal");
        let focused = session.editor().pane_id();
        session.execute(&format!("buffer {workspace}"));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 34)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert!(session.editor().diff().is_none());
        assert!(screen_text(&terminal).contains("WORKSPACE"));
        assert!(screen_text(&terminal).contains("Before"));
        assert!(screen_text(&terminal).contains("After"));
        let geometry = views.parked[&owner].panels.diff.as_ref().unwrap();
        let before = geometry.regions[1].0;
        let cursor = session.editor().cursor();
        let offsets = views.offsets.clone();
        assert!(views.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, before.x + 1, before.y + 1)
        ));
        terminal
            .draw(|frame| views.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(session.editor().pane_id(), focused);
        assert_eq!(session.editor().cursor(), cursor);
        assert_eq!(views.offsets, offsets);
        assert!(
            session
                .editor_mut()
                .with_render_pane(owner, |view| view.diff().unwrap().top > 0)
        );
        let area = views.rects.iter().find(|(id, _)| *id == focused).unwrap().1;
        assert!(area.contains(terminal.get_cursor_position().unwrap()));
    }

    fn readonly_diff_editor(file: ChangedFile) -> Editor {
        let mut editor = Editor::open(None, vec![]).unwrap();
        install_readonly_diff(&mut editor, file);
        editor
    }

    fn install_readonly_diff(editor: &mut Editor, file: ChangedFile) {
        editor.set_clipboard_mode("separate").unwrap();
        editor.execute("diff");
        let (id, _) = editor.take_diff_request().unwrap();
        editor.apply_diff_result(id, Ok(crate::diff::Outcome::Catalog(diff_catalog())));
        editor.handle(Input::Down);
        editor.handle(Input::Enter);
        editor.handle(Input::Down);
        editor.handle(Input::Enter);
        let (id, _) = editor.take_diff_request().unwrap();
        editor.apply_diff_result(
            id,
            Ok(crate::diff::Outcome::Comparison(crate::diff::Comparison {
                root: std::path::PathBuf::new(),
                editable_paths: Default::default(),
                before: "baseline".into(),
                after: "historic".into(),
                files: vec![file],
            })),
        );
    }

    fn render_native_diff(
        terminal: &mut Terminal<ratatui::backend::TestBackend>,
        views: &mut BufferViewports,
        editor: &mut Editor,
    ) -> Position {
        terminal.draw(|frame| views.draw(frame, editor)).unwrap();
        let (id, file, top, before, after) = views.panels.diff.as_ref().unwrap().viewport.unwrap();
        editor.set_diff_viewport(id, file, top, before, after);
        terminal.get_cursor_position().unwrap()
    }

    #[test]
    fn modified_sequences_navigate_diff_files_and_readonly_panes() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.handle(Input::Char('|'));
        install_readonly_diff(
            &mut editor,
            syntax_diff_file("history.txt", "before", "after"),
        );
        editor
            .bind("normal", "ctrl+w h", Some("core.pane.focus_left".into()))
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 30)).unwrap();
        let mut views = BufferViewports::default();
        render_native_diff(&mut terminal, &mut views, &mut editor);
        assert_eq!(editor.diff().unwrap().focus, Focus::Files);
        editor.handle(Input::Ctrl('w'));
        assert_eq!(editor.sequence_pending(), Some("Ctrl+w"));
        assert!(editor.diff().unwrap().files_visible);
        editor.handle(Input::Char('h'));
        assert_eq!(editor.diff().unwrap().focus, Focus::After);
        render_native_diff(&mut terminal, &mut views, &mut editor);
        editor.handle(Input::Ctrl('w'));
        editor.handle(Input::Char('h'));
        assert_eq!(editor.diff().unwrap().focus, Focus::Before);
        render_native_diff(&mut terminal, &mut views, &mut editor);
        editor.handle(Input::Ctrl('w'));
        editor.handle(Input::Char('h'));
        assert_eq!(editor.pane_id(), 1);
        assert_eq!(editor.sequence_pending(), None);
    }

    #[test]
    fn wrap_toggle_preserves_caret_screen_row_in_normal_buffers() {
        let directory = Directory::new();
        let text = (0..35)
            .map(|row| format!("line{row} {}", "word ".repeat(15)))
            .collect::<Vec<_>>()
            .join("\n");
        let mut editor = Editor::open(Some(directory.file("anchor.txt", &text)), vec![]).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(24, 10)).unwrap();
        let mut views = BufferViewports::default();
        for _ in 0..12 {
            editor.handle(Input::Down);
        }
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        for _ in 0..3 {
            editor.handle(Input::Up);
        }
        for _ in 0..30 {
            editor.handle(Input::Right);
        }
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        let row = terminal.get_cursor_position().unwrap().y;
        let source = editor.cursor();
        for _ in 0..4 {
            editor.execute("word_wrap.toggle");
            terminal
                .draw(|frame| views.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap().y, row);
            terminal
                .draw(|frame| views.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap().y, row);
            assert_eq!(editor.cursor(), source);
            assert_eq!(editor.lines().join("\n"), text);
        }
        for _ in 0..35 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::Home);
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        editor.execute("word_wrap.toggle");
        editor.handle(Input::Right);
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        let near_eof_row = terminal.get_cursor_position().unwrap().y;
        let near_eof_source = editor.cursor();
        editor.execute("word_wrap.toggle");
        for _ in 0..2 {
            terminal
                .draw(|frame| views.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap().y, near_eof_row);
            assert_eq!(editor.cursor(), near_eof_source);
        }
    }

    #[test]
    fn wrap_toggle_preserves_caret_screen_row_in_diff_buffers() {
        let before = (0..35)
            .map(|row| format!("old{row} {}", "word ".repeat(15)))
            .collect::<Vec<_>>()
            .join("\n");
        let after = before.replace("old", "new");
        let mut editor = readonly_diff_editor(syntax_diff_file("anchor.txt", &before, &after));
        editor.handle(Input::Char('\t'));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 14)).unwrap();
        let mut views = BufferViewports::default();
        for _ in 0..12 {
            editor.handle(Input::Down);
        }
        render_native_diff(&mut terminal, &mut views, &mut editor);
        for _ in 0..3 {
            editor.handle(Input::Up);
        }
        for _ in 0..30 {
            editor.handle(Input::Right);
        }
        let row = render_native_diff(&mut terminal, &mut views, &mut editor).y;
        let source = editor.cursor();
        for _ in 0..4 {
            editor.execute("word_wrap.toggle");
            assert_eq!(
                render_native_diff(&mut terminal, &mut views, &mut editor).y,
                row
            );
            assert_eq!(
                render_native_diff(&mut terminal, &mut views, &mut editor).y,
                row
            );
            assert_eq!(editor.cursor(), source);
        }
    }

    #[test]
    fn wrapped_diff_aligns_continuations_and_preserves_native_selection_and_caret() {
        let before = format!("// {}BEFORE_END\nsentinel", "old ".repeat(70));
        let after = format!("// {}AFTER_END\nsentinel", "new ".repeat(20));
        let mut editor = readonly_diff_editor(syntax_diff_file("history.rs", &before, &after));
        editor.execute("word_wrap.toggle");
        editor.handle(Input::Char('\t'));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(140, 20)).unwrap();
        let mut views = BufferViewports::default();
        render_native_diff(&mut terminal, &mut views, &mut editor);
        let geometry = views.panels.diff.as_ref().unwrap();
        let before_area = diff_inner(geometry.regions[1].0);
        let after_area = diff_inner(geometry.regions[2].0);
        let buffer = terminal.backend().buffer();
        let find_sentinel = |area: Rect| {
            (area.y..area.bottom())
                .find(|y| {
                    (area.x..area.right())
                        .map(|x| buffer[(x, *y)].symbol())
                        .collect::<String>()
                        .contains("sentinel")
                })
                .unwrap()
        };
        assert_eq!(find_sentinel(before_area), find_sentinel(after_area));
        editor.handle(Input::End);
        let caret = render_native_diff(&mut terminal, &mut views, &mut editor);
        assert!(before_area.contains(caret));
        assert_eq!(
            terminal.backend().buffer()[(caret.x, caret.y)].symbol(),
            "D"
        );
        assert_eq!(
            terminal.backend().buffer()[(caret.x, caret.y)].fg,
            Color::DarkGray
        );
        editor.handle(Input::Char('v'));
        editor.handle(Input::Home);
        render_native_diff(&mut terminal, &mut views, &mut editor);
        let wrap = views.panels.diff_wrap.as_ref().unwrap();
        let continuation = wrap
            .rows
            .iter()
            .position(|row| row.position.display == 0 && row.position.continuation == 1)
            .unwrap();
        let x = before_area.x
            + (before_area.width - views.panels.diff.as_ref().unwrap().text_widths[0]);
        assert_eq!(
            terminal.backend().buffer()[(x, before_area.y + continuation as u16)].bg,
            Color::Blue
        );
        let selection = editor.selections();
        let text = editor.lines().to_vec();
        editor.execute("word_wrap.toggle");
        render_native_diff(&mut terminal, &mut views, &mut editor);
        assert!(views.panels.diff_wrap.is_none());
        assert_eq!(editor.selections(), selection);
        assert_eq!(editor.lines(), text);
        assert_eq!(editor.mode(), Mode::Visual);
    }

    #[test]
    fn readonly_diff_panes_render_native_caret_visual_search_and_paired_focus() {
        let mut editor = readonly_diff_editor(syntax_diff_file(
            "history.rs",
            "fn old() {}\nlet value = \"old\";",
            "fn new() {}\nlet value = \"new\";",
        ));
        editor.handle(Input::Char('\t'));
        assert!(editor.diff_interacting());
        assert!(!editor.diff_editing());
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 14)).unwrap();
        let mut views = BufferViewports::default();
        views.set_theme(Some(LIGHT_DIFF_THEME));
        let caret = render_native_diff(&mut terminal, &mut views, &mut editor);
        let before = views.panels.diff.as_ref().unwrap().regions[1].0;
        assert!(before.contains(caret));
        assert_eq!(
            terminal.backend().buffer()[(caret.x, caret.y)].symbol(),
            "f"
        );
        assert_eq!(
            terminal.backend().buffer()[(caret.x, caret.y)].fg,
            Color::Magenta
        );
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        render_native_diff(&mut terminal, &mut views, &mut editor);
        assert_eq!(
            terminal.backend().buffer()[(caret.x, caret.y)].bg,
            Color::Blue
        );
        editor.handle(Input::Escape);
        editor.handle(Input::Down);
        editor.handle(Input::Home);
        editor.handle(Input::Char('V'));
        render_native_diff(&mut terminal, &mut views, &mut editor);
        assert_eq!(
            terminal.backend().buffer()[(caret.x, caret.y + 1)].bg,
            Color::Blue
        );
        assert_eq!(
            terminal.backend().buffer()[(caret.x + 16, caret.y + 1)].bg,
            Color::Blue
        );
        editor.handle(Input::Escape);
        editor.handle(Input::Char('/'));
        for ch in "value".chars() {
            editor.handle(Input::Char(ch));
        }
        render_native_diff(&mut terminal, &mut views, &mut editor);
        assert_eq!(terminal.get_cursor_position().unwrap().y, 13);
        editor.handle(Input::Enter);
        let searched = render_native_diff(&mut terminal, &mut views, &mut editor);
        assert!(before.contains(searched));
        assert_eq!(
            terminal.backend().buffer()[(searched.x, searched.y)].bg,
            Color::Yellow
        );
        assert_eq!(
            terminal.backend().buffer()[(searched.x, searched.y)].fg,
            Color::Black
        );
        let before_row = editor
            .diff()
            .unwrap()
            .source_display_row(Focus::Before, editor.cursor().row)
            .unwrap();
        let column = display_column(&editor.lines()[editor.cursor().row], editor.cursor().column);
        editor.handle(Input::Char('\t'));
        assert!(editor.diff_interacting());
        assert!(!editor.diff_editing());
        let switched = render_native_diff(&mut terminal, &mut views, &mut editor);
        let after = views.panels.diff.as_ref().unwrap().regions[2].0;
        assert!(after.contains(switched));
        assert_eq!(switched.y, searched.y);
        assert_eq!(switched.x - after.x, searched.x - before.x);
        assert_eq!(
            editor
                .diff()
                .unwrap()
                .source_display_row(Focus::After, editor.cursor().row),
            Some(before_row)
        );
        assert_eq!(
            display_column(&editor.lines()[editor.cursor().row], editor.cursor().column),
            column
        );
        editor.handle(Input::Right);
        let moved = render_native_diff(&mut terminal, &mut views, &mut editor);
        editor.handle(Input::Char('\t'));
        editor.handle(Input::Char('\t'));
        assert_eq!(editor.diff().unwrap().focus, Focus::Before);
        let returned = render_native_diff(&mut terminal, &mut views, &mut editor);
        assert!(before.contains(returned));
        assert_eq!(returned.y, moved.y);
        assert_eq!(returned.x - before.x, moved.x - after.x);
        assert_eq!(returned.x, searched.x + 1);
    }

    #[test]
    fn readonly_diff_viewport_retains_both_offsets_on_direction_and_focus_reversal() {
        let before = (0..80)
            .map(|row| format!("old row {row:03} {}", "x".repeat(100)))
            .collect::<Vec<_>>()
            .join("\n");
        let after = before.replace("old row", "new row");
        let mut editor = readonly_diff_editor(syntax_diff_file("history.txt", &before, &after));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 18)).unwrap();
        let mut views = BufferViewports::default();
        let mut retained_before_left = 0;
        for focus in [Focus::Before, Focus::After] {
            editor.handle(Input::Char('\t'));
            assert_eq!(editor.diff().unwrap().focus, focus);
            assert!(editor.diff_interacting());
            assert!(!editor.diff_editing());
            render_native_diff(&mut terminal, &mut views, &mut editor);
            for _ in 0..40 {
                editor.handle(Input::Down);
                render_native_diff(&mut terminal, &mut views, &mut editor);
            }
            let top = editor.diff().unwrap().top;
            assert!(top > 0);
            let bottom = render_native_diff(&mut terminal, &mut views, &mut editor);
            editor.handle(Input::Up);
            let reversed = render_native_diff(&mut terminal, &mut views, &mut editor);
            assert_eq!(editor.diff().unwrap().top, top);
            assert_eq!(reversed.y + 1, bottom.y);
            while editor
                .diff()
                .unwrap()
                .source_display_row(focus, editor.cursor().row)
                .unwrap()
                > top
            {
                editor.handle(Input::Up);
                render_native_diff(&mut terminal, &mut views, &mut editor);
                assert_eq!(editor.diff().unwrap().top, top);
            }
            editor.handle(Input::Up);
            render_native_diff(&mut terminal, &mut views, &mut editor);
            assert!(editor.diff().unwrap().top < top);
            for _ in 0..80 {
                editor.handle(Input::Right);
                render_native_diff(&mut terminal, &mut views, &mut editor);
            }
            let left = if focus == Focus::Before {
                editor.diff().unwrap().left_before
            } else {
                editor.diff().unwrap().left_after
            };
            assert!(left > 0);
            let right = render_native_diff(&mut terminal, &mut views, &mut editor);
            editor.handle(Input::Left);
            let reversed = render_native_diff(&mut terminal, &mut views, &mut editor);
            let offsets = views.panels.diff.as_ref().unwrap().viewport.unwrap();
            assert_eq!(
                if focus == Focus::Before {
                    offsets.3
                } else {
                    offsets.4
                },
                left
            );
            assert_eq!(reversed.x + 1, right.x);
            while editor.cursor().column > left {
                editor.handle(Input::Left);
                render_native_diff(&mut terminal, &mut views, &mut editor);
                let diff = editor.diff().unwrap();
                assert_eq!(
                    if focus == Focus::Before {
                        diff.left_before
                    } else {
                        diff.left_after
                    },
                    left
                );
            }
            editor.handle(Input::Left);
            render_native_diff(&mut terminal, &mut views, &mut editor);
            if focus == Focus::Before {
                retained_before_left = editor.diff().unwrap().left_before;
                assert!(retained_before_left < left);
            } else {
                assert!(editor.diff().unwrap().left_after < left);
                assert_eq!(editor.diff().unwrap().left_before, retained_before_left);
            }
        }
    }

    #[test]
    fn diff_semantic_colors_stay_buffer_local_across_focus_changes() {
        for writable in [false, true] {
            let directory = Directory::new();
            let path = directory.file("live.rs", "let value = 2;");
            let mut editor = Editor::open(Some(path), vec![]).unwrap();
            editor.execute("diff");
            let (id, _) = editor.take_diff_request().unwrap();
            editor.apply_diff_result(id, Ok(crate::diff::Outcome::Catalog(diff_catalog())));
            editor.handle(Input::Down);
            editor.handle(Input::Enter);
            editor.handle(Input::Enter);
            let (id, _) = editor.take_diff_request().unwrap();
            editor.apply_diff_result(
                id,
                Ok(crate::diff::Outcome::Comparison(crate::diff::Comparison {
                    root: directory.0.clone(),
                    editable_paths: if writable {
                        [std::path::PathBuf::from("live.rs")].into()
                    } else {
                        Default::default()
                    },
                    before: "baseline".into(),
                    after: "Working checkout".into(),
                    files: vec![syntax_diff_file(
                        "live.rs",
                        "let value = 1;",
                        "let value = 2;",
                    )],
                })),
            );
            editor.handle(Input::Char('\t'));
            assert_eq!(editor.diff_buffer_focus(), Some(Focus::Before));
            editor
                .replace_semantic_tokens(
                    editor.buffer_id(),
                    editor.text_revision(),
                    Some(Arc::from([semantic_token(
                        0,
                        4,
                        9,
                        SemanticTokenKind::Parameter,
                        0,
                    )])),
                )
                .unwrap();
            editor.handle(Input::Char('\t'));
            editor
                .replace_semantic_tokens(
                    editor.buffer_id(),
                    editor.text_revision(),
                    Some(Arc::from([semantic_token(
                        0,
                        4,
                        9,
                        SemanticTokenKind::Function,
                        SemanticTokenModifier::Declaration as u16,
                    )])),
                )
                .unwrap();
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 14)).unwrap();
            let mut views = BufferViewports::default();
            views.set_theme(Some(LIGHT_DIFF_THEME));
            for _ in 0..4 {
                terminal
                    .draw(|frame| views.draw(frame, &mut editor))
                    .unwrap();
                let regions = views.panels.diff.as_ref().unwrap().regions;
                for (index, color, bold) in
                    [(1, Color::LightCyan, false), (2, Color::LightBlue, true)]
                {
                    let pane = regions[index].0;
                    let cell = &terminal.backend().buffer()[(pane.x + 8, pane.y + 1)];
                    assert_eq!(cell.symbol(), "v");
                    assert_eq!(cell.fg, color);
                    assert_eq!(cell.modifier.contains(ratatui::style::Modifier::BOLD), bold);
                }
                editor.handle(Input::Char('\t'));
            }
            editor
                .replace_semantic_tokens(editor.buffer_id(), editor.text_revision(), None)
                .unwrap();
            terminal
                .draw(|frame| views.draw(frame, &mut editor))
                .unwrap();
            let regions = views.panels.diff.as_ref().unwrap().regions;
            let before = regions[1].0;
            let after = regions[2].0;
            assert_eq!(
                terminal.backend().buffer()[(before.x + 8, before.y + 1)].fg,
                Color::LightCyan
            );
            let value = &terminal.backend().buffer()[(after.x + 8, after.y + 1)];
            assert_eq!(value.fg, Color::Reset);
            assert!(!value.modifier.contains(ratatui::style::Modifier::BOLD));
            assert_eq!(
                terminal.backend().buffer()[(after.x + 4, after.y + 1)].fg,
                Color::Magenta
            );
        }
    }

    #[test]
    fn editable_after_renders_live_syntax_caret_visual_selection_and_command_prompt() {
        let directory = Directory::new();
        let path = directory.file("live.rs", "let value = \"new\";");
        let mut editor = Editor::open(Some(path), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor.execute("diff");
        let (id, _) = editor.take_diff_request().unwrap();
        editor.apply_diff_result(id, Ok(crate::diff::Outcome::Catalog(diff_catalog())));
        editor.handle(Input::Down);
        editor.handle(Input::Enter);
        editor.handle(Input::Enter);
        let (id, _) = editor.take_diff_request().unwrap();
        editor.apply_diff_result(
            id,
            Ok(crate::diff::Outcome::Comparison(crate::diff::Comparison {
                root: directory.0.clone(),
                editable_paths: [std::path::PathBuf::from("live.rs")].into(),
                before: "baseline".into(),
                after: "Working checkout".into(),
                files: vec![syntax_diff_file(
                    "live.rs",
                    "let value = \"old\";",
                    "let value = \"new\";",
                )],
            })),
        );
        editor.handle(Input::Char('\t'));
        editor.handle(Input::Char('\t'));
        assert!(editor.diff_editing());
        editor.handle(Input::Char('c'));
        editor.handle(Input::Char('c'));
        editor.handle(Input::Paste("// live comment".into()));
        editor.handle(Input::Escape);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 14)).unwrap();
        let mut views = BufferViewports::default();
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        let after = views.panels.diff.as_ref().unwrap().regions[2].0;
        let caret = terminal.get_cursor_position().unwrap();
        assert!(after.contains(caret));
        let text_x = after.x + 4;
        assert_eq!(terminal.backend().buffer()[(text_x, caret.y)].symbol(), "/");
        assert_eq!(
            terminal.backend().buffer()[(text_x, caret.y)].fg,
            Color::DarkGray
        );
        editor.handle(Input::Home);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(
            terminal.backend().buffer()[(text_x, caret.y)].bg,
            Color::Blue
        );
        editor.handle(Input::Escape);
        editor.handle(Input::Char(':'));
        for ch in "diff.close".chars() {
            editor.handle(Input::Char(ch));
        }
        terminal
            .draw(|frame| views.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.get_cursor_position().unwrap().y, 13);
        assert!(screen_text(&terminal).contains(":diff.close"));
        editor.handle(Input::Enter);
        assert!(editor.diff().is_none());
        assert_eq!(editor.lines(), ["// live comment"]);
        assert!(editor.dirty());
    }

    #[test]
    fn session_diff_draw_retains_rendered_offsets_until_caret_crosses_edges() {
        let directory = Directory::new();
        let original = (0..80)
            .map(|row| format!("old row {row:03} {}", "x".repeat(100)))
            .collect::<Vec<_>>()
            .join("\n");
        let path = directory.file("source.txt", &original);
        let git = |args: &[&str]| {
            let output = std::process::Command::new("git")
                .args(args)
                .current_dir(&directory.0)
                .env("GIT_CONFIG_NOSYSTEM", "1")
                .env("GIT_CONFIG_GLOBAL", "/dev/null")
                .env("GIT_AUTHOR_NAME", "Diff fixture")
                .env("GIT_AUTHOR_EMAIL", "fixture@example.invalid")
                .env("GIT_COMMITTER_NAME", "Diff fixture")
                .env("GIT_COMMITTER_EMAIL", "fixture@example.invalid")
                .env("GIT_AUTHOR_DATE", "2000-01-01T00:00:00Z")
                .env("GIT_COMMITTER_DATE", "2000-01-01T00:00:00Z")
                .output()
                .unwrap();
            assert!(output.status.success(), "{output:?}");
        };
        git(&["init", "-q"]);
        git(&["add", "."]);
        git(&["commit", "-qm", "base"]);
        directory.file("source.txt", &original.replace("old row", "new row"));
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let ready = |session: &mut EditorSession, phase| {
            let deadline = std::time::Instant::now() + Duration::from_secs(10);
            loop {
                session.poll();
                let diff = session.editor().diff().unwrap();
                assert!(diff.error.is_none(), "{:?}", diff.error);
                if diff.phase == phase && !diff.loading {
                    break;
                }
                assert!(std::time::Instant::now() < deadline, "{diff:?}");
                std::thread::sleep(Duration::from_millis(1));
            }
        };
        session.execute("diff");
        ready(&mut session, Phase::Before);
        session.handle(Input::Down);
        session.handle(Input::Enter);
        session.handle(Input::Enter);
        ready(&mut session, Phase::View);
        session.handle(Input::Char('\t'));
        session.handle(Input::Char('\t'));
        assert!(session.editor().diff_editing());
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 18)).unwrap();
        let mut views = BufferViewports::default();
        let mut render = |session: &mut EditorSession| {
            terminal
                .draw(|frame| views.draw_session(frame, session))
                .unwrap();
            terminal.get_cursor_position().unwrap()
        };
        render(&mut session);
        for _ in 0..40 {
            session.handle(Input::Down);
            render(&mut session);
        }
        let top = session.editor().diff().unwrap().top;
        assert!(top > 0);
        let bottom_caret = render(&mut session);
        session.handle(Input::Up);
        let reversed_caret = render(&mut session);
        assert_eq!(session.editor().diff().unwrap().top, top);
        assert_eq!(reversed_caret.y + 1, bottom_caret.y);
        while session
            .editor()
            .diff()
            .unwrap()
            .after_display_row(session.editor().cursor().row)
            .unwrap()
            > top
        {
            session.handle(Input::Up);
            render(&mut session);
            assert_eq!(session.editor().diff().unwrap().top, top);
        }
        session.handle(Input::Up);
        render(&mut session);
        assert!(session.editor().diff().unwrap().top < top);
        for _ in 0..80 {
            session.handle(Input::Right);
            render(&mut session);
        }
        let left = session.editor().diff().unwrap().left_after;
        assert!(left > 0);
        let right_caret = render(&mut session);
        session.handle(Input::Left);
        let reversed_caret = render(&mut session);
        assert_eq!(session.editor().diff().unwrap().left_after, left);
        assert_eq!(reversed_caret.x + 1, right_caret.x);
        while session.editor().cursor().column > left {
            session.handle(Input::Left);
            render(&mut session);
            assert_eq!(session.editor().diff().unwrap().left_after, left);
        }
        session.handle(Input::Left);
        render(&mut session);
        assert!(session.editor().diff().unwrap().left_after < left);
    }

    #[test]
    fn diff_wheel_routes_right_tree_and_both_panes_without_touching_document() {
        let directory = Directory::new();
        let path = directory.file("source.txt", &["original"; 60].join("\n"));
        let git = |args: &[&str]| {
            let output = std::process::Command::new("git")
                .args(args)
                .current_dir(&directory.0)
                .env("GIT_CONFIG_NOSYSTEM", "1")
                .env("GIT_CONFIG_GLOBAL", "/dev/null")
                .env("GIT_AUTHOR_NAME", "Diff fixture")
                .env("GIT_AUTHOR_EMAIL", "fixture@example.invalid")
                .env("GIT_COMMITTER_NAME", "Diff fixture")
                .env("GIT_COMMITTER_EMAIL", "fixture@example.invalid")
                .env("GIT_AUTHOR_DATE", "2000-01-01T00:00:00Z")
                .env("GIT_COMMITTER_DATE", "2000-01-01T00:00:00Z")
                .output()
                .unwrap();
            assert!(output.status.success(), "{:?}", output);
        };
        git(&["init", "-q"]);
        for index in 0..8 {
            directory.file(
                &format!("file-{index}.txt"),
                &format!("{}\nsecond\nthird\n", "before.".repeat(30)),
            );
        }
        git(&["add", "."]);
        git(&["commit", "-qm", "base"]);
        for index in 0..8 {
            directory.file(
                &format!("file-{index}.txt"),
                &format!("{}\nsecond\nthird\n", "after.".repeat(30)),
            );
        }
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let original = session.editor().lines().to_vec();
        let cursor = session.editor().cursor();
        let ready = |session: &mut EditorSession, phase| {
            let deadline = std::time::Instant::now() + Duration::from_secs(10);
            loop {
                session.poll();
                let diff = session.editor().diff().unwrap();
                assert!(diff.error.is_none(), "{:?}", diff.error);
                if diff.phase == phase && !diff.loading {
                    break;
                }
                assert!(std::time::Instant::now() < deadline, "{diff:?}");
                std::thread::sleep(Duration::from_millis(1));
            }
        };
        session.execute("diff");
        ready(&mut session, Phase::Before);
        session.handle(Input::Enter);
        session.handle(Input::Down);
        session.handle(Input::Enter);
        ready(&mut session, Phase::View);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 18)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        let regions = viewports.panels.diff.as_ref().unwrap().regions;
        let tree = regions[0].0;
        let before = regions[1].0;
        let after = regions[2].0;
        let initial_focus = session.editor().diff().unwrap().focus;
        let initial_cursor = session.editor().cursor();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollRight, before.x + 1, before.y + 1)
        ));
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert!(screen_text(&terminal).contains("ore.before."));
        assert_eq!(session.editor().diff().unwrap().left_before, 3);
        assert_eq!(session.editor().diff().unwrap().left_after, 3);
        let mut shift = document_wheel(MouseEventKind::ScrollDown, after.x + 1, after.y + 1);
        shift.modifiers = KeyModifiers::SHIFT;
        assert!(viewports.scroll(&mut session, shift));
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert!(screen_text(&terminal).contains("after.after."));
        assert_eq!(session.editor().diff().unwrap().left_before, 6);
        assert_eq!(session.editor().diff().unwrap().left_after, 6);
        assert_eq!(session.editor().diff().unwrap().top, 0);
        assert_eq!(session.editor().diff().unwrap().focus, initial_focus);
        assert_eq!(session.editor().cursor(), initial_cursor);
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, tree.x + 1, tree.y + 1),
        ));
        let diff = session.editor().diff().unwrap();
        assert_eq!(diff.focus, Focus::Files);
        assert_eq!(diff.files.as_ref().unwrap().selected, 3);
        assert_eq!(diff.file, 0);
        session.handle(Input::Enter);
        assert_eq!(session.editor().diff().unwrap().file, 3);
        ready(&mut session, Phase::View);
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, before.x + 1, before.y + 1),
        ));
        let diff = session.editor().diff().unwrap();
        assert_eq!(diff.focus, Focus::Before);
        assert_eq!(diff.top, 2);
        assert_eq!(diff.file, 3);
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollUp, after.x + 1, after.y + 1),
        ));
        let diff = session.editor().diff().unwrap();
        assert_eq!(diff.focus, Focus::After);
        assert_eq!(diff.top, 0);
        assert_eq!(diff.file, 3);
        let selected = diff.files.as_ref().unwrap().selected;
        session.handle(Input::Char(' '));
        session.handle(Input::Char('e'));
        session.handle(Input::Ctrl('w'));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, tree.x + 1, tree.y + 1),
        ));
        let diff = session.editor().diff().unwrap();
        assert_eq!(diff.focus, Focus::After);
        assert_eq!(diff.files.as_ref().unwrap().selected, selected);
        assert!(!diff.files.as_ref().unwrap().focused);
        assert!(viewports.panels.files.is_none());
        assert!(viewports.document.geometry.is_none());
        session.execute("diff.close");
        assert_eq!(session.editor().lines(), original);
        assert_eq!(session.editor().cursor(), cursor);
    }

    #[test]
    fn diff_wheel_cannot_scroll_the_hidden_document_even_outside_the_picker() {
        let directory = Directory::new();
        let path = directory.file("rows.txt", &["original"; 60].join("\n"));
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 30)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        let id = session.editor().buffer_id();
        let offset = viewports.offsets[&id];
        let cursor = session.editor().cursor();
        session.execute("diff");
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 0, 0)
        ));
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 60, 15)
        ));
        assert_eq!(viewports.offsets[&id], offset);
        assert_eq!(session.editor().cursor(), cursor);
        assert!(viewports.document.geometry.is_none());
        session.execute("diff.close");
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.document.geometry.is_some());
    }

    #[test]
    fn completion_windows_selected_unicode_without_overwriting_gutter_dock_or_cursor() {
        let mut completion = Completion {
            items: (0..20)
                .map(|index| crate::plugin::CompletionItem {
                    label: if index == 19 {
                        "界e\u{301}👩‍🚀\u{1b}".into()
                    } else {
                        format!("item-{index:02}")
                    },
                    detail: Some("\tTAIL".into()),
                    primary_edit: 0,
                    edits: vec![],
                    snippet: None,
                })
                .collect(),
            selected: 20,
        };
        for (width, height) in [(14, 6), (9, 1), (5, 1)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            let workspace = Rect::new(2, 0, width - 4, height);
            let caret = Position::new(2, 0);
            let mut panel = None;
            completion.selected = 20;
            terminal
                .draw(|frame| {
                    let rows: Vec<Line> = (0..height)
                        .map(|_| Line::from(format!("GG{}EE", ".".repeat(usize::from(width - 4)))))
                        .collect();
                    frame.render_widget(Paragraph::new(rows), frame.area());
                    frame.set_cursor_position(caret);
                    panel = draw_completion(frame, &completion, workspace, caret);
                })
                .unwrap();
            let mut panel = panel.unwrap();
            let selected_y = panel.bottom() - 1;
            let buffer = terminal.backend().buffer();
            assert_eq!(buffer[(panel.x, selected_y)].bg, Color::Cyan);
            assert!(!screen_text(&terminal).contains("item-00"));
            for y in 0..height {
                for x in [0, 1] {
                    assert_eq!(buffer[(x, y)].symbol(), "G");
                }
                for x in [width - 2, width - 1] {
                    assert_eq!(buffer[(x, y)].symbol(), "E");
                }
            }
            if workspace.width >= 5 {
                assert_eq!(buffer[(panel.x, selected_y)].symbol(), "界");
                assert_eq!(buffer[(panel.x + 2, selected_y)].symbol(), "e\u{301}");
                assert_eq!(buffer[(panel.x + 3, selected_y)].symbol(), "👩‍🚀");
            } else {
                assert_eq!(buffer[(panel.x, selected_y)].symbol(), " ");
            }
            if workspace.width >= 6 {
                assert_eq!(buffer[(panel.x + 5, selected_y)].symbol(), "�");
            }
            assert_eq!(terminal.get_cursor_position().unwrap(), caret);
            completion.selected = 0;
            terminal
                .draw(|frame| {
                    frame.set_cursor_position(caret);
                    panel = draw_completion(frame, &completion, workspace, caret).unwrap();
                })
                .unwrap();
            assert_eq!(
                terminal.backend().buffer()[(panel.x, panel.y)].symbol(),
                "O"
            );
            assert_eq!(
                terminal.backend().buffer()[(panel.x, panel.y)].bg,
                Color::Cyan
            );
            assert_eq!(terminal.get_cursor_position().unwrap(), caret);
        }
    }

    #[test]
    fn snippet_highlight_tracks_argument_graphemes_without_filling_the_row() {
        use crate::plugin::{
            CompletionEdit, CompletionItem, CompletionSnippet, SnippetTabstop, TextPosition,
        };
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.handle(Input::Char('i'));
        editor
            .show_completion(vec![CompletionItem {
                label: "call".into(),
                detail: None,
                primary_edit: 0,
                edits: vec![CompletionEdit {
                    start: TextPosition { row: 0, column: 0 },
                    end: TextPosition { row: 0, column: 0 },
                    text: "call(界e\u{301}, tail)".into(),
                }],
                snippet: Some(CompletionSnippet {
                    tabstops: vec![
                        SnippetTabstop {
                            index: 1,
                            ranges: vec![5..11],
                            ancestors: vec![vec![]],
                        },
                        SnippetTabstop {
                            index: 2,
                            ranges: vec![13..17],
                            ancestors: vec![vec![]],
                        },
                        SnippetTabstop {
                            index: 0,
                            ranges: vec![18..18],
                            ancestors: vec![vec![]],
                        },
                    ],
                }),
            }])
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(28, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        for (key, selected, caret) in [
            (None, 7..10, Position::new(7, 0)),
            (Some(Input::Char('\t')), 12..16, Position::new(12, 0)),
        ] {
            if let Some(key) = key {
                editor.handle(key);
            }
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            let buffer = terminal.backend().buffer();
            // A wide glyph's leading cell owns its terminal style.
            for x in (0..28).filter(|x| *x != 8) {
                assert_eq!(
                    buffer[(x, 0)].bg == Color::Blue,
                    selected.contains(&x),
                    "column {x}, selection {:?}, screen:\n{}",
                    editor.snippet_selections(),
                    screen_text(&terminal),
                );
            }
            assert_eq!(terminal.get_cursor_position().unwrap(), caret);
        }
        editor.handle(Input::Escape);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        for x in 0..28 {
            assert_ne!(terminal.backend().buffer()[(x, 0)].bg, Color::Blue);
        }
    }

    #[test]
    fn hover_shows_more_documentation_with_markdown_and_fenced_code_colors() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        let title = format!("# {}TAIL", "Heading ".repeat(11));
        let details = (5..36)
            .map(|row| format!("detail-{row:02}"))
            .collect::<Vec<_>>()
            .join("\n");
        editor
            .show_hover(format!(
                "{title}\n\n```rust\nfn answer() -> i32 {{ 42 }}\n```\n{details}"
            ))
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 32)).unwrap();
        let mut panels = WheelPanels::default();
        terminal
            .draw(|frame| draw_hover(frame, editor.hover().unwrap(), frame.area(), &mut panels))
            .unwrap();
        assert!(screen_text(&terminal).contains("TAIL"));
        assert!(screen_text(&terminal).contains("detail-20"));
        let (panel, _) = panels.hover.unwrap();
        let (x, y) = (panel.x + 1, panel.y + 1);
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(x, y)].fg, Color::Cyan);
        assert_eq!(buffer[(x, y + 3)].symbol(), "f");
        assert_eq!(buffer[(x, y + 3)].fg, Color::Magenta);
        assert_eq!(buffer[(x + 6, y + 3)].fg, Color::LightBlue);
        assert_eq!(buffer[(x + 21, y + 3)].fg, Color::Yellow);

        for _ in 0..3 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::Right);
        terminal
            .draw(|frame| draw_hover(frame, editor.hover().unwrap(), frame.area(), &mut panels))
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(x, y)].symbol(), "n");
        assert_eq!(buffer[(x, y)].fg, Color::Magenta);
        assert_eq!(buffer[(x + 20, y)].fg, Color::Yellow);

        editor.show_hover("# Replacement".into()).unwrap();
        terminal
            .draw(|frame| draw_hover(frame, editor.hover().unwrap(), frame.area(), &mut panels))
            .unwrap();
        assert!(screen_text(&terminal).contains("# Replacement"));
        assert!(!screen_text(&terminal).contains("answer"));
    }

    #[test]
    fn hover_scroll_renders_whole_graphemes_in_tiny_workspace() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(6, 1)).unwrap();
        let mut syntax = SyntaxCache::new();
        let (mut top, mut left) = (0, 0);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                );
            })
            .unwrap();
        let document_cursor = terminal.get_cursor_position().unwrap();
        editor.show_hover("x界e\u{301}👩‍🚀z\nlast".into()).unwrap();
        for _ in 0..2 {
            editor.handle(Input::Right);
        }
        let mut panels = WheelPanels::default();
        let rendered = terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut panels,
                )
            })
            .unwrap();
        let origin = panels.hover.unwrap().0;
        assert_eq!(rendered.buffer[(origin.x, origin.y)].symbol(), "e\u{301}");
        assert_eq!(rendered.buffer[(origin.x + 1, origin.y)].symbol(), "👩‍🚀");
        assert_eq!(rendered.buffer[(origin.x + 3, origin.y)].symbol(), "z");
        assert_eq!(terminal.get_cursor_position().unwrap(), document_cursor);
        assert_eq!((top, left), (0, 0));
        editor.handle(Input::Down);
        editor.handle(Input::Home);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).trim().ends_with("last"));
        for (width, height) in [(1, 1), (2, 2), (3, 3), (4, 4)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
        }
        assert_eq!(editor.cursor(), crate::editor::Cursor::default());
        assert_eq!(editor.lines(), &[""]);
    }

    fn annotation(
        start: (usize, usize),
        end: (usize, usize),
        severity: DiagnosticSeverity,
        message: &str,
    ) -> Diagnostic {
        Diagnostic {
            start: crate::plugin::TextPosition {
                row: start.0,
                column: start.1,
            },
            end: crate::plugin::TextPosition {
                row: end.0,
                column: end.1,
            },
            severity,
            message: message.into(),
        }
    }

    fn semantic_token(
        row: usize,
        start: usize,
        end: usize,
        kind: SemanticTokenKind,
        modifiers: u16,
    ) -> SemanticToken {
        SemanticToken {
            start: crate::plugin::TextPosition { row, column: start },
            end: crate::plugin::TextPosition { row, column: end },
            kind,
            modifiers,
        }
    }

    #[test]
    fn diagnostic_underlines_preserve_syntax_and_whole_graphemes_at_viewport_edges() {
        let directory = Directory::new();
        let source = "#a\t界e\u{301}👩‍🚀z";
        let mut editor = Editor::open(Some(directory.file("unicode.py", source)), vec![]).unwrap();
        editor
            .replace_diagnostics(
                "fixture",
                editor.buffer_id(),
                editor.text_revision(),
                vec![
                    annotation((0, 2), (0, 6), DiagnosticSeverity::Warning, "range"),
                    annotation((0, 4), (0, 5), DiagnosticSeverity::Error, "combining"),
                ],
            )
            .unwrap();
        let mut syntax = SyntaxCache::new();
        for (offset, width, caret, underlines) in [
            (
                2,
                5,
                4,
                vec![
                    Some(Color::Yellow),
                    Some(Color::Yellow),
                    Some(Color::Yellow),
                    Some(Color::Yellow),
                    Some(Color::Red),
                ],
            ),
            (5, 2, 4, vec![None, Some(Color::Red)]),
            (7, 2, 5, vec![Some(Color::Yellow), Some(Color::Yellow)]),
            (8, 2, 6, vec![None, None]),
            (
                0,
                5,
                2,
                vec![None, None, Some(Color::Yellow), Some(Color::Yellow), None],
            ),
        ] {
            editor.handle(Input::Home);
            for _ in 0..caret {
                editor.handle(Input::Right);
            }
            let area = Rect::new(3, 2, width + 2, 4);
            let mut terminal = Terminal::with_options(
                ratatui::backend::TestBackend::new(20, 8),
                ratatui::TerminalOptions {
                    viewport: ratatui::Viewport::Fixed(area),
                },
            )
            .unwrap();
            let (mut top, mut left) = (0, offset);
            let rendered = terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap()
                .buffer
                .clone();
            assert_eq!(left, offset);
            for (cell, underline) in underlines.into_iter().enumerate() {
                let position = (area.x + 2 + cell as u16, area.y);
                assert_eq!(
                    rendered[position].modifier.contains(Modifier::UNDERLINED),
                    underline.is_some(),
                    "left={offset}, cell={cell}",
                );
                if let Some(color) = underline {
                    assert_eq!(rendered[position].underline_color, color);
                    assert_eq!(rendered[position].fg, Color::DarkGray);
                }
                assert_eq!(rendered[position].bg, Color::Reset);
            }
            assert_eq!(rendered[(area.x, area.y)].fg, Color::Red);
            assert_eq!(
                terminal.backend().buffer()[(0, 0)].modifier,
                Modifier::empty()
            );
            assert_eq!(editor.lines(), &[source]);
        }
    }

    #[test]
    fn diagnostics_render_newlines_anchors_counts_and_messages_without_hiding_core_errors() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "abc\n\nxy\nlast".into(),
            )])
            .unwrap();
        editor
            .replace_diagnostics(
                "fixture",
                editor.buffer_id(),
                editor.text_revision(),
                vec![
                    annotation((0, 2), (0, 2), DiagnosticSeverity::Error, "point"),
                    annotation((0, 1), (3, 0), DiagnosticSeverity::Warning, "multiline"),
                    annotation((3, 4), (3, 4), DiagnosticSeverity::Information, "end"),
                    annotation((3, 0), (3, 4), DiagnosticSeverity::Hint, "hint"),
                ],
            )
            .unwrap();
        editor.handle(Input::Home);
        editor.handle(Input::Right);
        editor.handle(Input::Right);
        editor.set_message("write failed: permission denied");
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(120, 7)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let buffer = terminal.backend().buffer();
        for (position, color) in [
            ((3, 0), Color::Yellow),
            ((4, 0), Color::Red),
            ((5, 0), Color::Yellow),
            ((2, 1), Color::Yellow),
            ((2, 2), Color::Yellow),
            ((3, 2), Color::Yellow),
            ((4, 2), Color::Yellow),
            ((2, 3), Color::DarkGray),
            ((6, 3), Color::Cyan),
        ] {
            assert!(buffer[position].modifier.contains(Modifier::UNDERLINED));
            assert_eq!(buffer[position].underline_color, color);
        }
        for (row, color) in [
            (0, Color::Red),
            (1, Color::Yellow),
            (2, Color::Yellow),
            (3, Color::Cyan),
        ] {
            assert_eq!(buffer[(0, row)].fg, color);
        }
        assert!(!buffer[(6, 0)].modifier.contains(Modifier::UNDERLINED));
        let text = screen_text(&terminal);
        assert!(text.contains("E:1  W:1  I:1  H:1"), "{text}");
        assert!(
            text.contains("write failed: permission denied | E: point"),
            "{text}"
        );
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(4, 0),
        );

        editor.handle(Input::Char('i'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(editor.diagnostics().count(), 0);
        assert!(!screen_text(&terminal).contains("E:1"));
        assert!(!screen_text(&terminal).contains("E: point"));
        assert_ne!(terminal.backend().buffer()[(0, 0)].fg, Color::Red);
        assert!(
            !terminal.backend().buffer()[(4, 0)]
                .modifier
                .contains(Modifier::UNDERLINED)
        );
        for message in ["intermediate", "latest"] {
            editor
                .replace_diagnostics(
                    "fixture",
                    editor.buffer_id(),
                    editor.text_revision(),
                    vec![annotation(
                        (0, 0),
                        (0, 3),
                        DiagnosticSeverity::Error,
                        message,
                    )],
                )
                .unwrap();
        }
        editor.handle(Input::Escape);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("E:1"));
        assert!(screen_text(&terminal).contains("E: latest"));
        assert!(!screen_text(&terminal).contains("intermediate"));
        assert_eq!(terminal.backend().buffer()[(0, 0)].fg, Color::Red);
        assert!(
            terminal.backend().buffer()[(3, 0)]
                .modifier
                .contains(Modifier::UNDERLINED)
        );
        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('!'));
        assert_eq!(editor.mode(), Mode::Insert);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(editor.diagnostics().count(), 0);
        assert!(!screen_text(&terminal).contains("E:1"));
        assert!(
            !terminal.backend().buffer()[(4, 0)]
                .modifier
                .contains(Modifier::UNDERLINED)
        );
        editor.handle(Input::Escape);
        assert_eq!(editor.diagnostics().count(), 0);
    }

    #[test]
    fn idle_session_updates_redraw_annotations_and_navigation_while_native_editing_continues() {
        let directory = Directory::new();
        let source = directory.file("source.txt", "broken TARGET");
        let target_text = format!("{}{}TARGET", "# line\n".repeat(15), "#".repeat(40));
        let target = directory.file("target.py", &target_text);
        directory.file(
            "semantic.rb",
            r#"
Vamp.plugin "semantic", requires: ["text", "diagnostics"], async: true
work = Queue.new
Vamp.on_document { |event| work << ["document", event] }
Vamp.command "fixture_definition" do |editor, _|
  raise "No target reference" unless editor.text.include?("TARGET")
  work << ["definition", editor.buffer_id, editor.revision, editor.request_id]
end
Thread.new do
  documents = {}
  loop do
    kind, *args = work.pop
    if kind == "document"
      event = args[0]
      document = event.fetch("document")
      if event.fetch("event") == "close"
        documents.delete(document.fetch("id"))
        next
      end
      documents[document.fetch("id")] = document
      next unless ["open", "change"].include?(event.fetch("event"))
      items = []
      document.fetch("text").split("\n", -1).each_with_index do |line, row|
        graphemes = line.each_grapheme_cluster.to_a
        graphemes.each_cons(6).with_index do |token, column|
          next unless token.join == "broken"
          items << {start: {row: row, column: column},
                    end: {row: row, column: column + 6},
                    severity: "error", message: "Unresolved token"}
        end
      end
      Vamp.publish([{type: "diagnostics", buffer_id: document.fetch("id"),
                     revision: document.fetch("revision"), items: items},
                    {type: "message", text: "diagnostic revision #{document.fetch('revision')}"}])
    else
      target = documents.values.find { |document| document["path"] == Vamp.options.fetch("target") }
      raise "Target document is not open" unless target
      lines = target.fetch("text").split("\n", -1)
      row = lines.index { |line| line.include?("TARGET") }
      raise "Target definition missing" unless row
      column = lines[row].each_grapheme_cluster.to_a.each_cons(6).find_index { |token| token.join == "TARGET" }
      Vamp.publish([{type: "navigate", buffer_id: args[0], revision: args[1],
                     path: target.fetch("path"), row: row, column: column}],
                   request_id: args[2])
    end
  end
end
"#,
        );
        let config = directory.file(
            "config.rb",
            &format!(
                "Vamp.configure do |config|\n  config.clipboard_mode = \"separate\"\n  config.plugin \"semantic.rb\", options: {{target: {}}}\nend\n",
                serde_json::to_string(&target.to_string_lossy()).unwrap(),
            ),
        );
        let mut session = EditorSession::open(
            Some(source),
            CAPABILITIES
                .iter()
                .map(|capability| (*capability).into())
                .collect(),
            Some(&config),
        )
        .unwrap();
        let source_id = session.editor().buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(18, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();

        fn poll_until(
            session: &mut EditorSession,
            terminal: &mut Terminal<ratatui::backend::TestBackend>,
            viewports: &mut BufferViewports,
            ready: impl Fn(&Editor) -> bool,
        ) {
            for _ in 0..2_000 {
                if session.poll() {
                    terminal
                        .draw(|frame| viewports.draw(frame, session.editor_mut()))
                        .unwrap();
                }
                if ready(session.editor()) {
                    return;
                }
                std::thread::sleep(Duration::from_millis(1));
            }
            panic!(
                "async fixture did not update editor: {}",
                session.editor().message()
            );
        }

        session.handle(Input::Char('A'));
        session.handle(Input::Char('!'));
        assert_eq!(session.editor().mode(), Mode::Insert);
        assert_eq!(session.editor().lines(), &["broken TARGET!"]);
        poll_until(&mut session, &mut terminal, &mut viewports, |editor| {
            editor.message() == "diagnostic revision 1"
        });
        assert_eq!(session.editor().diagnostics().count(), 0);
        assert!(!screen_text(&terminal).contains("E:1"));
        assert!(
            !terminal.backend().buffer()[(2, 0)]
                .modifier
                .contains(Modifier::UNDERLINED)
        );
        assert_eq!(session.editor().mode(), Mode::Insert);
        session.handle(Input::Escape);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(screen_text(&terminal).contains("E:1"));
        assert!(
            terminal.backend().buffer()[(2, 0)]
                .modifier
                .contains(Modifier::UNDERLINED)
        );
        session.handle(Input::Char('u'));
        assert_eq!(session.editor().lines(), &["broken TARGET"]);
        assert_eq!(session.editor().diagnostics().count(), 0);

        session.execute(&format!("edit {}", target.display()));
        let target_id = session.editor().buffer_id();
        session.handle(Input::Char('i'));
        session.handle(Input::Char('!'));
        session.handle(Input::Escape);
        session.execute(&format!("buffer {source_id}"));
        session.execute("fixture_definition");
        session.handle(Input::Char('l'));
        assert_eq!(session.editor().buffer_id(), source_id);
        poll_until(&mut session, &mut terminal, &mut viewports, |editor| {
            editor.buffer_id() == target_id
        });
        assert_eq!(session.editor().buffer_count(), 2);
        assert!(session.editor().dirty());
        assert_eq!(session.editor().lines()[0], "!# line");
        assert_eq!(session.editor().cursor().row, 15);
        assert_eq!(session.editor().cursor().column, 40);
        assert_eq!(session.editor().mode(), Mode::Normal);
        assert_eq!(viewports.offsets[&target_id], (12, 26));
        let cursor = terminal.get_cursor_position().unwrap();
        assert_eq!(
            terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
            "T"
        );
        assert_eq!(
            terminal.backend().buffer()[(cursor.x, cursor.y)].fg,
            Color::DarkGray
        );
        assert_eq!(fs::read_to_string(target).unwrap(), target_text);
    }

    #[test]
    fn syntax_tokens_refresh_after_native_edits_and_undo_without_changing_text_on_draw() {
        let directory = Directory::new();
        let path = directory.file("number.rs", "42");
        let mut editor = Editor::open(Some(path), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(40, 5)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Yellow);
        let revision = editor.text_revision();
        editor.handle(Input::Right);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(editor.text_revision(), revision);
        assert_eq!(editor.lines(), &["42"]);
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Yellow);

        editor.handle(Input::Home);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        editor.handle(Input::Char('c'));
        for ch in "\"ok\"".chars() {
            editor.handle(Input::Char(ch));
        }
        editor.handle(Input::Escape);
        assert_eq!(editor.lines(), &["\"ok\""]);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Green);
        assert!(editor.text_revision() > revision);
        editor.handle(Input::Char('u'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(editor.lines(), &["42"]);
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Yellow);

        editor
            .apply(vec![crate::editor::Effect::Replace(
                "fn main() { let n = 42; let s = \"ok\"; } // note".into(),
            )])
            .unwrap();
        editor.handle(Input::Home);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let buffer = terminal.backend().buffer();
        let source = &editor.lines()[0];
        for (token, color) in [
            ("fn", Color::Magenta),
            ("main", Color::LightBlue),
            ("let", Color::Magenta),
            ("42", Color::Yellow),
            ("\"ok\"", Color::Green),
        ] {
            let x = 2 + source.find(token).unwrap() as u16;
            assert_eq!(buffer[(x, 0)].fg, color, "{token}");
            assert_eq!(buffer[(x, 0)].bg, Color::Reset);
        }
    }

    #[test]
    fn syntax_continuations_above_viewport_refresh_when_the_opening_line_changes() {
        let directory = Directory::new();
        for (name, before, after, color) in [
            (
                "comment.rs",
                "/*\nhidden\nvisible\n*/",
                "//\nhidden\nvisible\n//",
                Color::DarkGray,
            ),
            (
                "string.py",
                "text = \"\"\"\nhidden\nvisible\n\"\"\"",
                "text = \"\"\nhidden\nvisible\n\"\"",
                Color::Green,
            ),
        ] {
            let path = directory.file(name, before);
            let mut editor = Editor::open(Some(path), vec![]).unwrap();
            editor.handle(Input::Down);
            editor.handle(Input::Down);
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(30, 3)).unwrap();
            let mut viewports = BufferViewports::default();
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(viewports.offsets[&editor.buffer_id()].0, 2);
            assert_eq!(terminal.backend().buffer()[(2, 0)].symbol(), "v");
            assert_eq!(terminal.backend().buffer()[(2, 0)].fg, color, "{name}");
            editor
                .apply(vec![crate::editor::Effect::Replace(after.into())])
                .unwrap();
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(terminal.backend().buffer()[(2, 0)].symbol(), "v");
            assert_eq!(
                terminal.backend().buffer()[(2, 0)].fg,
                Color::Reset,
                "{name}"
            );
            editor.handle(Input::Char('u'));
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(terminal.backend().buffer()[(2, 0)].fg, color, "{name}");
        }
    }

    #[test]
    fn semantic_roles_remain_distinct_when_values_and_fields_are_readonly() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "ns Type local frozen field fixed param frozenparam".into(),
            )])
            .unwrap();
        let readonly = SemanticTokenModifier::Readonly as u16;
        editor
            .replace_semantic_tokens(
                editor.buffer_id(),
                editor.text_revision(),
                Some(Arc::from([
                    semantic_token(0, 0, 2, SemanticTokenKind::Namespace, 0),
                    semantic_token(0, 3, 7, SemanticTokenKind::Type, 0),
                    semantic_token(0, 8, 13, SemanticTokenKind::Variable, 0),
                    semantic_token(0, 14, 20, SemanticTokenKind::Variable, readonly),
                    semantic_token(0, 21, 26, SemanticTokenKind::Property, 0),
                    semantic_token(0, 27, 32, SemanticTokenKind::Property, readonly),
                    semantic_token(0, 33, 38, SemanticTokenKind::Parameter, 0),
                    semantic_token(0, 39, 50, SemanticTokenKind::Parameter, readonly),
                ])),
            )
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(60, 4)).unwrap();
        terminal
            .draw(|frame| BufferViewports::default().draw(frame, &mut editor))
            .unwrap();
        let buffer = terminal.backend().buffer();
        let foregrounds = [0, 3, 8, 14, 21, 27, 33, 39].map(|column| buffer[(column + 2, 0)].fg);
        assert_ne!(foregrounds[0], foregrounds[1]);
        assert_ne!(foregrounds[1], foregrounds[2]);
        assert_ne!(foregrounds[2], foregrounds[4]);
        assert_eq!(foregrounds[2], foregrounds[3]);
        assert_eq!(foregrounds[4], foregrounds[5]);
        assert_eq!(foregrounds[6], foregrounds[7]);
        for (column, is_readonly) in [
            (0, false),
            (3, false),
            (8, false),
            (14, true),
            (21, false),
            (27, true),
            (33, false),
            (39, true),
        ] {
            assert_eq!(
                buffer[(column + 2, 0)].modifier.contains(Modifier::ITALIC),
                is_readonly,
            );
        }
    }

    #[test]
    fn semantic_colors_modifiers_and_syntax_fallback_cover_whole_graphemes_and_clipped_tabs() {
        let directory = Directory::new();
        let source = "#a\t界e\u{301}👩‍🚀z";
        let mut editor = Editor::open(Some(directory.file("unicode.py", source)), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor
            .replace_semantic_tokens(
                editor.buffer_id(),
                editor.text_revision(),
                Some(Arc::from([
                    semantic_token(
                        0,
                        0,
                        1,
                        SemanticTokenKind::Comment,
                        SemanticTokenModifier::Documentation as u16,
                    ),
                    semantic_token(
                        0,
                        2,
                        6,
                        SemanticTokenKind::Property,
                        SemanticTokenModifier::Readonly as u16
                            | SemanticTokenModifier::Definition as u16
                            | SemanticTokenModifier::Deprecated as u16,
                    ),
                    semantic_token(0, 2, 3, SemanticTokenKind::Variable, 0),
                ])),
            )
            .unwrap();
        editor
            .replace_diagnostics(
                "fixture",
                editor.buffer_id(),
                editor.text_revision(),
                vec![annotation(
                    (0, 2),
                    (0, 6),
                    DiagnosticSeverity::Warning,
                    "semantic",
                )],
            )
            .unwrap();
        let mut syntax = SyntaxCache::new();
        for (offset, width, caret, coverage) in [
            (2, 5, 4, vec![true; 5]),
            (5, 2, 4, vec![false, true]),
            (7, 2, 5, vec![true; 2]),
            (8, 2, 6, vec![false; 2]),
            (0, 5, 2, vec![false, false, true, true, false]),
        ] {
            editor.handle(Input::Home);
            for _ in 0..caret {
                editor.handle(Input::Right);
            }
            let area = Rect::new(3, 2, width + 2, 4);
            let mut terminal = Terminal::with_options(
                ratatui::backend::TestBackend::new(20, 8),
                ratatui::TerminalOptions {
                    viewport: ratatui::Viewport::Fixed(area),
                },
            )
            .unwrap();
            let (mut top, mut left) = (0, offset);
            let rendered = terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap()
                .buffer
                .clone();
            assert_eq!(left, offset);
            let text_area = Rect::new(area.x + 2, area.y, width, 1);
            let mut expected = ratatui::buffer::Buffer::empty(text_area);
            use ratatui::widgets::Widget;
            Paragraph::new(visible_line(source, offset, usize::from(width)))
                .render(text_area, &mut expected);
            let buffer = terminal.backend().buffer();
            for (cell, semantic_cell) in coverage.into_iter().enumerate() {
                let position = (text_area.x + cell as u16, text_area.y);
                assert_eq!(buffer[position].symbol(), expected[position].symbol());
                assert_eq!(rendered[position].bg, Color::Reset);
                assert_eq!(
                    rendered[position].modifier.contains(Modifier::BOLD),
                    semantic_cell
                );
                assert_eq!(
                    rendered[position].modifier.contains(Modifier::CROSSED_OUT),
                    semantic_cell
                );
                assert_eq!(
                    rendered[position].modifier.contains(Modifier::UNDERLINED),
                    semantic_cell
                );
                if semantic_cell {
                    assert_eq!(rendered[position].underline_color, Color::Yellow);
                }
                assert_eq!(
                    rendered[position].modifier.contains(Modifier::ITALIC),
                    semantic_cell || (offset == 0 && cell == 0)
                );
            }
            assert_eq!(buffer[(area.x, area.y)].fg, Color::Yellow);
            assert_eq!(buffer[(0, 0)].fg, Color::Reset);
            assert_eq!(editor.lines(), &[source]);
        }
        editor.handle(Input::Char('x'));
        assert!(editor.semantic_tokens().is_empty());
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(20, 4)).unwrap();
        let (mut top, mut left) = (0, 0);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::DarkGray);
        assert!(
            !terminal.backend().buffer()[(2, 0)]
                .modifier
                .contains(Modifier::ITALIC)
        );
    }

    #[test]
    fn search_visual_selection_and_secondary_carets_override_semantic_foreground() {
        let directory = Directory::new();
        let mut editor = Editor::open(
            Some(directory.file("overlays.py", "# word\n# word\n# word")),
            vec![],
        )
        .unwrap();
        editor
            .replace_semantic_tokens(
                editor.buffer_id(),
                editor.text_revision(),
                Some(Arc::from(
                    (0..3)
                        .map(|row| {
                            semantic_token(
                                row,
                                2,
                                6,
                                SemanticTokenKind::Function,
                                SemanticTokenModifier::Declaration as u16,
                            )
                        })
                        .collect::<Vec<_>>(),
                )),
            )
            .unwrap();
        editor
            .replace_diagnostics(
                "fixture",
                editor.buffer_id(),
                editor.text_revision(),
                vec![annotation(
                    (0, 2),
                    (2, 6),
                    DiagnosticSeverity::Error,
                    "overlays",
                )],
            )
            .unwrap();
        editor.handle(Input::Char('/'));
        for ch in "word".chars() {
            editor.handle(Input::Char(ch));
        }
        editor.handle(Input::Enter);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(40, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let found = editor.search_match().unwrap();
        let y = found.start.row as u16;
        for x in 4..8 {
            assert_eq!(terminal.backend().buffer()[(x, y)].fg, Color::Black);
            assert_eq!(terminal.backend().buffer()[(x, y)].bg, Color::Yellow);
            assert!(
                terminal.backend().buffer()[(x, y)]
                    .modifier
                    .contains(Modifier::UNDERLINED)
            );
        }
        editor.handle(Input::Char('v'));
        editor.handle(Input::Char('e'));
        editor.handle(Input::Ctrl('a'));
        assert_eq!(editor.selection_count(), 3);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let buffer = terminal.backend().buffer();
        for selection in editor.selections() {
            let y = selection.start.row as u16;
            let start =
                display_column(&editor.lines()[selection.start.row], selection.start.column);
            let end = display_column(&editor.lines()[selection.end.row], selection.end.column);
            for column in start..end {
                let x = 2 + column as u16;
                if buffer[(x, y)].bg == Color::Magenta {
                    assert_eq!(buffer[(x, y)].fg, Color::Black);
                } else {
                    assert_eq!(buffer[(x, y)].fg, Color::White);
                    assert_eq!(buffer[(x, y)].bg, Color::Blue);
                }
                assert!(buffer[(x, y)].modifier.contains(Modifier::UNDERLINED));
            }
            assert_eq!(buffer[(2, y)].fg, Color::DarkGray);
        }
        for caret in editor
            .carets()
            .into_iter()
            .filter(|caret| *caret != editor.cursor())
        {
            let x = 2 + display_column(&editor.lines()[caret.row], caret.column) as u16;
            assert_eq!(buffer[(x, caret.row as u16)].fg, Color::Black);
            assert_eq!(buffer[(x, caret.row as u16)].bg, Color::Magenta);
            assert!(
                buffer[(x, caret.row as u16)]
                    .modifier
                    .contains(Modifier::UNDERLINED)
            );
        }
    }

    #[test]
    fn syntax_redetects_saved_paths_without_text_changes_and_plain_text_keeps_default_color() {
        let directory = Directory::new();
        let mut editor =
            Editor::open(Some(directory.file("source.rs", "let value = 42;")), vec![]).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(40, 5)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Magenta);
        let revision = editor.text_revision();
        for name in ["source.vampunknown", "source.txt", "again.rs"] {
            editor.execute(&format!("w {}", directory.0.join(name).display()));
            assert_eq!(editor.text_revision(), revision);
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            if name.ends_with(".rs") {
                assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Magenta);
                assert_eq!(
                    viewports.syntax[&editor.buffer_id()].language(),
                    Some("Rust")
                );
            } else {
                assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Reset);
                assert!(viewports.syntax[&editor.buffer_id()].line(0).is_empty());
                assert!(viewports.syntax[&editor.buffer_id()].language().is_none());
            }
            assert_eq!(editor.lines(), &["let value = 42;"]);
        }
    }

    #[test]
    fn syntax_caches_stay_independent_across_buffer_edits_and_retire_closed_ids() {
        let directory = Directory::new();
        let mut editor = Editor::open(Some(directory.file("a.rs", "42")), vec![]).unwrap();
        let a_id = editor.buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(40, 5)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Yellow);
        editor.execute(&format!(
            "edit {}",
            directory.file("b.py", "# note").display()
        ));
        let b_id = editor.buffer_id();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::DarkGray);
        editor
            .apply(vec![crate::editor::Effect::Replace("\"ok\"".into())])
            .unwrap();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Green);
        editor.execute(&format!("buffer {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Yellow);
        assert_eq!(viewports.syntax[&a_id].language(), Some("Rust"));
        assert_eq!(viewports.syntax[&b_id].language(), Some("Python"));
        editor.execute(&format!("buffer {b_id}"));
        editor.execute(&format!("bdelete {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(2, 0)].fg, Color::Green);
        assert!(!viewports.syntax.contains_key(&a_id));
        assert!(!viewports.offsets.contains_key(&a_id));
        assert_eq!(viewports.syntax.len(), 1);
    }

    #[test]
    fn translate_distinguishes_control_j_from_enter_and_normalizes_control_letters() {
        for (code, modifiers, expected) in [
            (
                KeyCode::Char('j'),
                KeyModifiers::CONTROL,
                Some(Input::Ctrl('j')),
            ),
            (
                KeyCode::Char('J'),
                KeyModifiers::CONTROL | KeyModifiers::SHIFT,
                Some(Input::Ctrl('j')),
            ),
            (
                KeyCode::Char('k'),
                KeyModifiers::CONTROL,
                Some(Input::Ctrl('k')),
            ),
            (
                KeyCode::Char('h'),
                KeyModifiers::CONTROL,
                Some(Input::Ctrl('h')),
            ),
            (
                KeyCode::Char('l'),
                KeyModifiers::CONTROL,
                Some(Input::Ctrl('l')),
            ),
            (
                KeyCode::Backspace,
                KeyModifiers::NONE,
                Some(Input::Backspace),
            ),
            (KeyCode::Enter, KeyModifiers::NONE, Some(Input::Enter)),
            (KeyCode::Enter, KeyModifiers::CONTROL, Some(Input::Enter)),
            (
                KeyCode::Char('J'),
                KeyModifiers::SHIFT,
                Some(Input::Char('J')),
            ),
            (KeyCode::Char('j'), KeyModifiers::ALT, Some(Input::Alt('j'))),
            (
                KeyCode::Char('H'),
                KeyModifiers::ALT | KeyModifiers::SHIFT,
                Some(Input::Alt('h')),
            ),
            (
                KeyCode::Char('j'),
                KeyModifiers::ALT | KeyModifiers::CONTROL,
                Some(Input::CtrlAlt('j')),
            ),
            (
                KeyCode::Char('H'),
                KeyModifiers::CONTROL | KeyModifiers::ALT | KeyModifiers::SHIFT,
                Some(Input::CtrlAlt('h')),
            ),
            (
                KeyCode::Char('L'),
                KeyModifiers::CONTROL | KeyModifiers::ALT | KeyModifiers::SHIFT,
                Some(Input::CtrlAlt('l')),
            ),
            (
                KeyCode::Char('j'),
                KeyModifiers::CONTROL | KeyModifiers::ALT | KeyModifiers::SUPER,
                None,
            ),
            (
                KeyCode::Left,
                KeyModifiers::CONTROL | KeyModifiers::ALT,
                None,
            ),
            (KeyCode::Char('j'), KeyModifiers::SUPER, None),
            (KeyCode::Left, KeyModifiers::ALT, None),
        ] {
            assert_eq!(translate(KeyEvent::new(code, modifiers)), expected);
        }
    }

    #[test]
    fn wheel_routes_to_floating_and_unfocused_docked_files_without_changing_selection() {
        let directory = Directory::new();
        let config = directory.file(
            "config.rb",
            "Vamp.configure do |config|\n  config.file_picker_view = 'list'\n  config.file_explorer_view = 'list'\nend\n",
        );
        for (key, focused) in [('o', true), ('e', true), ('e', false)] {
            let mut session = EditorSession::open(None, vec![], Some(&config)).unwrap();
            session.handle(Input::Char(' '));
            session.handle(Input::Char(key));
            if !focused {
                session.handle(Input::Char('\t'));
            }
            let picker = session.editor().file_picker().unwrap();
            assert!(picker.entries().len() > 5);
            let selected = picker.selected;
            let selected_path = picker.entries().nth(selected).unwrap().path.to_owned();
            let query = picker.query.clone();
            let carets = session.editor().carets();
            let revision = session.editor().text_revision();
            let mut panels = WheelPanels::default();
            let area = Rect::new(3, 2, 40, 6);
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(60, 12)).unwrap();
            terminal
                .draw(|frame| draw_file_list(frame, picker, area, "", &mut panels, None))
                .unwrap();
            let mouse = MouseEvent {
                kind: MouseEventKind::ScrollDown,
                column: area.x,
                row: area.y,
                modifiers: KeyModifiers::NONE,
            };
            assert!(!panels.scroll(
                &mut session,
                MouseEvent {
                    column: 0,
                    row: 0,
                    ..mouse
                }
            ));
            assert!(panels.scroll(&mut session, mouse));
            assert_eq!(panels.manual_files.as_ref().unwrap().top, 3);
            terminal
                .draw(|frame| {
                    panels.begin_frame();
                    draw_file_list(
                        frame,
                        session.editor().file_picker().unwrap(),
                        area,
                        "",
                        &mut panels,
                        None,
                    );
                })
                .unwrap();
            let picker = session.editor().file_picker().unwrap();
            let text = screen_text(&terminal);
            assert!(
                text.contains(picker.entries().nth(3).unwrap().label),
                "{text}"
            );
            assert!(
                !text.contains(&format!(
                    "> {}",
                    picker.entries().nth(selected).unwrap().label
                )),
                "{text}"
            );
            assert_eq!(picker.selected, selected);
            assert_eq!(picker.entries().nth(selected).unwrap().path, selected_path);
            assert_eq!(picker.query, query);
            assert_eq!(picker.focused, focused);
            assert_eq!(session.editor().carets(), carets);
            assert_eq!(session.editor().text_revision(), revision);
            let entry_count = picker.entries().len();
            assert!(!panels.scroll(
                &mut session,
                MouseEvent {
                    kind: MouseEventKind::Moved,
                    ..mouse
                }
            ));
            for _ in 0..entry_count {
                assert!(panels.scroll(&mut session, mouse));
            }
            let (_, height, _) = panels.files.unwrap();
            assert_eq!(
                panels.manual_files.as_ref().unwrap().top,
                session.editor().file_picker().unwrap().entries().len() - height
            );
            panels.follow_files();
            terminal
                .draw(|frame| {
                    draw_file_list(
                        frame,
                        session.editor().file_picker().unwrap(),
                        area,
                        "",
                        &mut panels,
                        None,
                    )
                })
                .unwrap();
            assert_eq!(panels.files.unwrap().2, 0);
            session.handle(Input::Ctrl('p'));
            assert!(session.editor().palette().is_some());
            assert!(panels.scroll(&mut session, mouse));
            assert!(panels.manual_files.is_none());
            session.handle(Input::Escape);
            session.handle(Input::Char(' '));
            session.handle(Input::Char(key));
            session.handle(Input::Ctrl('w'));
            assert!(session.editor().file_picker().is_none());
            assert!(!panels.scroll(&mut session, mouse));
        }
    }

    #[test]
    fn manually_scrolled_tree_does_not_place_cursor_or_highlight_offscreen_selection() {
        let directory = Directory::new();
        for index in 0..12 {
            directory.file(&format!("file-{index:02}"), "");
        }
        let mut picker = FilePicker::scan(
            directory.0.clone(),
            FilePresentation::Docked,
            FileView::Tree,
        )
        .unwrap();
        picker.selected = 11;
        let mut panels = WheelPanels {
            manual_files: Some(FileWheelOffset {
                top: 0,
                root: picker.root.clone(),
                query: picker.query.clone(),
                state: FileWheelOffset::state(&picker),
            }),
            ..WheelPanels::default()
        };
        let area = Rect::new(3, 2, 40, 6);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(60, 12)).unwrap();
        terminal
            .draw(|frame| {
                frame.set_cursor_position((59, 11));
                draw_file_list(frame, &picker, area, "", &mut panels, None);
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("file-00"), "{text}");
        assert!(!text.contains("file-11"), "{text}");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(59, 11)
        );
        for y in area.y..area.bottom() {
            for x in area.x..area.right() {
                assert_ne!(terminal.backend().buffer()[(x, y)].bg, Color::Blue);
            }
        }
        picker.navigate(false);
        terminal
            .draw(|frame| draw_file_list(frame, &picker, area, "", &mut panels, None))
            .unwrap();
        assert!(panels.manual_files.is_none());
        assert!(screen_text(&terminal).contains("> file-10"));
    }

    #[test]
    fn file_list_window_follows_control_j_k_selection() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.set_file_picker_view("list").unwrap();
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('o'));
        let count = editor.file_picker().unwrap().entries().len();
        assert!(count > 1);
        for _ in 0..count - 1 {
            editor.handle(
                translate(KeyEvent::new(KeyCode::Char('j'), KeyModifiers::CONTROL)).unwrap(),
            );
        }
        assert_eq!(editor.file_picker().unwrap().selected, count - 1);
        editor.handle(translate(KeyEvent::new(KeyCode::Char('k'), KeyModifiers::CONTROL)).unwrap());
        assert_eq!(editor.file_picker().unwrap().selected, count - 2);
        let picker = editor.file_picker().unwrap();
        let label = picker.entries().nth(picker.selected).unwrap().label;
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 9)).unwrap();
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    picker,
                    frame.area(),
                    editor.file_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains(&format!("> {label}")), "{text}");
        let buffer = terminal.backend().buffer();
        let selected_y = (3..8).find(|&y| buffer[(1, y)].symbol() == ">").unwrap();
        assert_eq!(buffer[(1, selected_y)].bg, Color::Blue);
    }

    #[test]
    fn explorer_wraps_only_root_path_and_reserves_file_rows_in_short_panes() {
        let root = "/a/very/long/path/to/project/root";
        let picker = FilePicker::from_paths(root.into(), [(0, "entry.txt".into())]);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(20, 12)).unwrap();
        let mut panels = WheelPanels::default();
        terminal
            .draw(|frame| draw_file_list(frame, &picker, frame.area(), "", &mut panels, None))
            .unwrap();
        let buffer = terminal.backend().buffer();
        let path = (2..4)
            .map(|y| (1..19).map(|x| buffer[(x, y)].symbol()).collect::<String>())
            .collect::<String>();
        assert_eq!(path.trim_end(), root);
        assert!(
            screen_text(&terminal)
                .lines()
                .nth(4)
                .unwrap()
                .contains("entry.txt")
        );
        terminal.backend_mut().resize(20, 6);
        terminal
            .draw(|frame| draw_file_list(frame, &picker, frame.area(), "", &mut panels, None))
            .unwrap();
        assert!(screen_text(&terminal).contains("entry.txt"));
    }

    #[test]
    fn list_footers_show_remapped_and_disabled_selection_keys() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.set_file_explorer_view("list").unwrap();
        editor.set_file_picker_view("list").unwrap();
        for key in ["ctrl+j", "ctrl+n", "down", "ctrl+k", "up"] {
            editor.bind("selection", key, None).unwrap();
        }
        editor
            .bind("selection", "x", Some("core.down".into()))
            .unwrap();
        let hint = editor.selection_navigation_hint().to_owned();
        assert_eq!(hint, "x next · unbound previous");
        editor.set_file_explorer_side("bottom").unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 24)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        for key in ['o', 'e'] {
            editor.handle(Input::Char(' '));
            editor.handle(Input::Char(key));
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let text = screen_text(&terminal);
            assert!(text.contains(&hint), "{text}");
            assert!(!text.contains("Ctrl+j"), "{text}");
            editor.handle(Input::Escape);
        }
        editor.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains(&hint), "{text}");
        assert!(!text.contains("Ctrl+j"), "{text}");
    }

    #[test]
    fn file_list_scrolls_selection_and_sanitizes_display_without_losing_paths() {
        let directory = Directory::new();
        for index in 0..18 {
            directory.file(&format!("file-{index:02}"), "text");
        }
        let special = directory.file("界e\u{301} space\nname", "text");
        let editor = Editor::open(None, vec![]).unwrap();
        let mut picker = FilePicker::scan(
            directory.0.clone(),
            FilePresentation::Floating,
            FileView::List,
        )
        .unwrap();
        assert!(
            picker
                .entries()
                .any(|entry| directory.0.join(entry.path) == special)
        );
        let count = picker.entries().len();
        picker.selected = count - 1;
        let label = picker.entries().last().unwrap().label;
        assert_eq!(label, "界e\u{301} space�name");
        picker.query = "long\t界e\u{301}z".into();
        let area = Rect::new(3, 2, 24, 9);
        let mut terminal = Terminal::with_options(
            ratatui::backend::TestBackend::new(40, 15),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(area),
            },
        )
        .unwrap();
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    &picker,
                    area,
                    editor.selection_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(!text.contains("file-00"), "{text}");
        let cursor = terminal.get_cursor_position().unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(area.x + 7, area.y + 1)].symbol(), "�");
        assert_eq!(buffer[(area.x + 8, area.y + 1)].symbol(), "界");
        assert_eq!(buffer[(area.x + 10, area.y + 1)].symbol(), "e\u{301}");
        let selected_y = (area.y + 2..area.bottom() - 1)
            .find(|&y| buffer[(area.x + 1, y)].symbol() == ">")
            .unwrap();
        assert_eq!(buffer[(area.x + 3, selected_y)].symbol(), "界");
        assert_eq!(buffer[(area.x + 5, selected_y)].symbol(), "e\u{301}");
        assert_eq!(buffer[(area.x + 1, selected_y)].bg, Color::Blue);
        assert!(
            buffer[(area.x + 1, selected_y)]
                .modifier
                .contains(Modifier::BOLD)
        );
        assert_eq!(cursor.y, area.y + 1);
        assert_eq!(buffer[(0, 0)].symbol(), " ");
    }

    #[test]
    fn file_list_renders_root_empty_filter_errors_and_idle_focus() {
        let directory = Directory::new();
        let editor = Editor::open(None, vec![]).unwrap();
        let mut picker = FilePicker::scan(
            directory.0.clone(),
            FilePresentation::Docked,
            FileView::List,
        )
        .unwrap();
        let area = Rect::new(0, 0, 100, 12);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    &picker,
                    area,
                    editor.selection_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("Explorer"), "{text}");
        assert!(
            text.contains(&directory.0.to_string_lossy().to_string()),
            "{text}"
        );
        assert!(text.contains("No project files"), "{text}");
        assert!(text.contains("Esc/Tab"), "{text}");
        picker.query = "missing".into();
        picker.error = Some("Unreadable\npath\u{1b}".into());
        picker.focused = false;
        terminal
            .draw(|frame| {
                frame.set_cursor_position((99, 11));
                draw_file_list(
                    frame,
                    &picker,
                    area,
                    editor.selection_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                );
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("No matching files"), "{text}");
        assert!(text.contains("Unreadable�path�"), "{text}");
        assert!(text.contains("Editor focus"), "{text}");
        assert_eq!(terminal.backend().buffer()[(1, 3)].fg, Color::Red);
        assert_eq!(terminal.backend().buffer()[(0, 0)].fg, Color::DarkGray);
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(99, 11)
        );
        picker.presentation = FilePresentation::Floating;
        picker.focused = true;
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    &picker,
                    area,
                    editor.selection_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("Files"));
        assert!(screen_text(&terminal).contains("Esc/^W"));
        assert_eq!(terminal.backend().buffer()[(0, 0)].fg, Color::Cyan);
        picker.set_view(FileView::Tree);
        picker.finish_search();
        terminal
            .draw(|frame| {
                draw_file_list(
                    frame,
                    &picker,
                    area,
                    editor.file_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("No matching files"), "{text}");
        assert!(text.contains("filter: missing"), "{text}");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(1, 1)
        );
        picker.focused = false;
        terminal
            .draw(|frame| {
                frame.set_cursor_position((99, 11));
                draw_file_list(
                    frame,
                    &picker,
                    area,
                    editor.file_navigation_hint(),
                    &mut WheelPanels::default(),
                    None,
                );
            })
            .unwrap();
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(99, 11)
        );
    }

    #[test]
    fn file_query_cursor_and_dock_layout_survive_tiny_offset_resizes() {
        let directory = Directory::new();
        let editor = Editor::open(None, vec![]).unwrap();
        let mut picker = FilePicker::scan(
            directory.0.clone(),
            FilePresentation::Docked,
            FileView::List,
        )
        .unwrap();
        picker.query = "long界e\u{301}z".into();
        for (width, height) in [(12, 6), (8, 2), (1, 1), (1, 2), (8, 1), (12, 6)] {
            let area = Rect::new(3, 2, width, height);
            let mut terminal = Terminal::with_options(
                ratatui::backend::TestBackend::new(24, 12),
                ratatui::TerminalOptions {
                    viewport: ratatui::Viewport::Fixed(area),
                },
            )
            .unwrap();
            terminal
                .draw(|frame| {
                    draw_file_list(
                        frame,
                        &picker,
                        area,
                        editor.selection_navigation_hint(),
                        &mut WheelPanels::default(),
                        None,
                    )
                })
                .unwrap();
            let cursor = terminal.get_cursor_position().unwrap();
            assert!(area.contains(cursor), "{area:?}: {cursor:?}");
            let bordered = width >= 4 && height >= 4;
            let query_x = area.x + u16::from(bordered);
            let query_y = area.y + u16::from(bordered);
            let query_width = width - 2 * u16::from(bordered);
            assert_eq!(cursor.x, query_x + query_width - 1);
            assert_eq!(cursor.y, query_y);
            let query = format!("> {}", picker.query);
            let offset =
                display_column(&query, usize::MAX).saturating_sub(usize::from(query_width) - 1);
            let mut expected =
                ratatui::buffer::Buffer::empty(Rect::new(query_x, query_y, query_width, 1));
            use ratatui::widgets::Widget;
            Paragraph::new(visible_line(&query, offset, usize::from(query_width)))
                .render(expected.area, &mut expected);
            for x in query_x..query_x + query_width {
                assert_eq!(
                    terminal.backend().buffer()[(x, query_y)].symbol(),
                    expected[(x, query_y)].symbol()
                );
            }
            assert_eq!(terminal.backend().buffer()[(0, 0)].symbol(), " ");
            for side in [
                DockSide::Left,
                DockSide::Right,
                DockSide::Top,
                DockSide::Bottom,
            ] {
                for focused in [false, true] {
                    let (editor, panel) = dock_layout(area, side, focused);
                    for rect in [Some(editor), panel].into_iter().flatten() {
                        assert!(rect.x >= area.x && rect.y >= area.y);
                        assert!(rect.right() <= area.right() && rect.bottom() <= area.bottom());
                    }
                    if focused {
                        assert!(panel.is_some());
                    } else {
                        assert!(panel.is_none());
                    }
                }
            }
        }
        for (width, height) in [(0, 1), (1, 0), (0, 0)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| {
                    draw_file_list(
                        frame,
                        &picker,
                        frame.area(),
                        editor.selection_navigation_hint(),
                        &mut WheelPanels::default(),
                        None,
                    )
                })
                .unwrap();
            assert!(
                dock_layout(Rect::new(3, 2, width, height), DockSide::Right, true)
                    .1
                    .is_none()
            );
        }
    }

    #[test]
    fn tree_rows_render_directory_chains_hierarchy_and_basename_files_in_both_presentations() {
        use std::path::Path;
        let directory = Directory::new();
        directory.file("chain/a/b/leaf.txt", "");
        directory.file("mixed/nested/inner.txt", "");
        directory.file("mixed/sibling.txt", "");
        directory.file("single/only.txt", "");
        directory.file("root.txt", "");
        fs::create_dir(directory.0.join("empty")).unwrap();
        let editor = Editor::open(None, vec![]).unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            let mut picker =
                FilePicker::scan(directory.0.clone(), presentation, FileView::Tree).unwrap();
            assert_eq!(picker.entries().next().unwrap().label, "chain/a/b");
            for path in ["chain/a/b", "mixed", "mixed/nested", "single"] {
                let selected = picker
                    .entries()
                    .position(|row| row.path == Path::new(path))
                    .unwrap();
                picker.selected = selected;
                picker.right();
            }
            let area = Rect::new(3, 2, 100, 22);
            let mut terminal = Terminal::with_options(
                ratatui::backend::TestBackend::new(110, 28),
                ratatui::TerminalOptions {
                    viewport: ratatui::Viewport::Fixed(area),
                },
            )
            .unwrap();
            terminal
                .draw(|frame| {
                    draw_file_list(
                        frame,
                        &picker,
                        area,
                        editor.file_navigation_hint(),
                        &mut WheelPanels::default(),
                        None,
                    )
                })
                .unwrap();
            let text = screen_text(&terminal);
            for label in [
                "  chain/a/b/",
                "    leaf.txt",
                "  empty/",
                "  mixed/",
                "    nested/",
                "      inner.txt",
                "    sibling.txt",
                "> single/",
                "    only.txt",
                "  root.txt",
            ] {
                assert!(text.contains(label), "{label}: {text}");
            }
            assert!(!text.contains('▸') && !text.contains('▾'), "{text}");
            let buffer = terminal.backend().buffer();
            for (index, entry) in picker.entries().enumerate() {
                let y = area.y + 3 + index as u16;
                assert_eq!(
                    buffer[(area.x + 1, y)].fg,
                    if entry.is_dir {
                        Color::Cyan
                    } else {
                        Color::Reset
                    },
                );
            }
            assert!(!text.contains("single/only.txt"), "{text}");
            assert!(!text.contains("mixed/nested/inner.txt"), "{text}");
            let cursor = terminal.get_cursor_position().unwrap();
            assert_eq!(
                terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
                ">"
            );
            assert_eq!(
                terminal.backend().buffer()[(cursor.x, cursor.y)].bg,
                Color::Blue
            );
            picker.set_view(FileView::List);
            terminal
                .draw(|frame| {
                    draw_file_list(
                        frame,
                        &picker,
                        area,
                        editor.file_navigation_hint(),
                        &mut WheelPanels::default(),
                        None,
                    )
                })
                .unwrap();
            let text = screen_text(&terminal);
            assert!(text.contains("chain/a/b/leaf.txt"), "{text}");
            assert!(text.contains("single/only.txt"), "{text}");
            assert!(!text.contains("▸"), "{text}");
            assert_eq!(terminal.get_cursor_position().unwrap().y, area.y + 1);
        }
    }

    #[test]
    fn tree_browse_cursor_tracks_window_and_bounds_empty_search_and_tiny_offset_panels() {
        let directory = Directory::new();
        for index in 0..18 {
            directory.file(&format!("dir-{index:02}/file.txt"), "");
        }
        let editor = Editor::open(None, vec![]).unwrap();
        let mut picker = FilePicker::scan(
            directory.0.clone(),
            FilePresentation::Docked,
            FileView::Tree,
        )
        .unwrap();
        for _ in 0..17 {
            picker.navigate(true);
        }
        picker.right();
        picker.right();
        let long_query = "long界e\u{301}z".repeat(20);
        for (width, height) in [(100, 9), (12, 6), (8, 2), (1, 1), (1, 2), (8, 1), (100, 9)] {
            let area = Rect::new(3, 2, width, height);
            let mut terminal = Terminal::with_options(
                ratatui::backend::TestBackend::new(110, 16),
                ratatui::TerminalOptions {
                    viewport: ratatui::Viewport::Fixed(area),
                },
            )
            .unwrap();
            terminal
                .draw(|frame| {
                    draw_file_list(
                        frame,
                        &picker,
                        area,
                        editor.file_navigation_hint(),
                        &mut WheelPanels::default(),
                        None,
                    )
                })
                .unwrap();
            let cursor = terminal.get_cursor_position().unwrap();
            assert!(area.contains(cursor), "{area:?}: {cursor:?}");
            let has_results = height > if width >= 4 && height >= 4 { 3 } else { 1 };
            if has_results {
                assert_eq!(
                    terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
                    ">"
                );
            } else {
                assert_eq!(cursor, ratatui::layout::Position::new(area.x, area.y));
            }
            if width == 100 {
                let text = screen_text(&terminal);
                assert!(text.contains(">   file.txt"), "{text}");
                assert!(!text.contains("dir-00"), "{text}");
            }
            for query in ["missing", long_query.as_str()] {
                picker.start_search();
                picker.query = query.into();
                picker.refilter();
                terminal
                    .draw(|frame| {
                        draw_file_list(
                            frame,
                            &picker,
                            area,
                            editor.file_navigation_hint(),
                            &mut WheelPanels::default(),
                            None,
                        )
                    })
                    .unwrap();
                let cursor = terminal.get_cursor_position().unwrap();
                assert!(area.contains(cursor), "{area:?}: {cursor:?}");
                assert_eq!(cursor.y, area.y + u16::from(width >= 4 && height >= 4));
                picker.finish_search();
                assert_eq!(picker.query, query);
                assert_eq!(picker.entries().len(), 0);
                terminal
                    .draw(|frame| {
                        draw_file_list(
                            frame,
                            &picker,
                            area,
                            editor.file_navigation_hint(),
                            &mut WheelPanels::default(),
                            None,
                        )
                    })
                    .unwrap();
                let cursor = terminal.get_cursor_position().unwrap();
                assert!(area.contains(cursor), "{area:?}: {cursor:?}");
                let query_x = area.x + u16::from(width >= 4 && height >= 4);
                assert_eq!(cursor.x, query_x);
                let query_y = area.y + u16::from(width >= 4 && height >= 4);
                let query_width = width - 2 * u16::from(width >= 4 && height >= 4);
                let header = format!("filter: {query} · ^U clear");
                let mut expected =
                    ratatui::buffer::Buffer::empty(Rect::new(query_x, query_y, query_width, 1));
                use ratatui::widgets::Widget;
                Paragraph::new(visible_line(&header, 0, usize::from(query_width)))
                    .render(expected.area, &mut expected);
                let mut continuation = 0;
                for x in query_x..query_x + query_width {
                    if continuation > 0 {
                        continuation -= 1;
                        continue;
                    }
                    continuation = expected[(x, query_y)].symbol().width().saturating_sub(1);
                    assert_eq!(
                        terminal.backend().buffer()[(x, query_y)].symbol(),
                        expected[(x, query_y)].symbol()
                    );
                }
                if width == 100 {
                    assert!(screen_text(&terminal).contains("filter: "), "{query}");
                    assert!(
                        screen_text(&terminal).contains("No matching files"),
                        "{query}"
                    );
                }
                picker.clear_filter();
                assert!(!picker.searching);
                assert_eq!(
                    picker.entries().nth(picker.selected).unwrap().path,
                    std::path::Path::new("dir-17/file.txt")
                );
            }
        }
    }

    #[test]
    fn tree_filter_escape_resume_and_clear_keep_selection_and_cursor_ownership() {
        use std::path::Path;
        let directory = Directory::new();
        directory.file("src/inner/needle.txt", "");
        directory.file("src/other.txt", "");
        directory.file("root.txt", "");
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            let mut editor = Editor::open(None, vec![]).unwrap();
            editor.set_project_root(directory.0.clone());
            editor.set_file_picker_view("tree").unwrap();
            editor
                .apply(vec![crate::editor::Effect::Replace("unchanged".into())])
                .unwrap();
            editor.handle(Input::Char('v'));
            let mode = editor.mode();
            let selections = editor.selections();
            editor.handle(Input::Char(' '));
            editor.handle(Input::Char(if presentation == FilePresentation::Floating {
                'o'
            } else {
                'e'
            }));
            if !editor.file_picker().unwrap().searching {
                editor.handle(Input::Char('i'));
            }
            let query = "src/inner/needle.txt";
            for ch in query.chars() {
                editor.handle(Input::Char(ch));
            }
            editor.handle(Input::Ctrl('h'));
            let picker = editor.file_picker().unwrap();
            assert_eq!(picker.query, query);
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new("src/inner")
            );
            editor.handle(Input::Ctrl('l'));
            let picker = editor.file_picker().unwrap();
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new(query)
            );
            let filtered: Vec<_> = picker
                .entries()
                .map(|row| (row.path.to_owned(), row.expanded))
                .collect();
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 24)).unwrap();
            let (mut top, mut left) = (0, 0);
            let mut syntax = SyntaxCache::new();
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let query_cursor = terminal.get_cursor_position().unwrap();
            assert!(screen_text(&terminal).contains(&format!("> {query}")));
            assert!(screen_text(&terminal).contains("^U clear"));
            editor.handle(Input::Escape);
            let picker = editor.file_picker().unwrap();
            assert!(picker.focused && !picker.searching);
            assert_eq!(picker.query, query);
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new(query)
            );
            assert_eq!(
                picker
                    .entries()
                    .map(|row| (row.path.to_owned(), row.expanded))
                    .collect::<Vec<_>>(),
                filtered
            );
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let text = screen_text(&terminal);
            assert!(text.contains(&format!("filter: {query}")), "{text}");
            assert!(
                text.contains("needle.txt") && !text.contains("other.txt"),
                "{text}"
            );
            let selected_cursor = terminal.get_cursor_position().unwrap();
            assert_ne!(selected_cursor.y, query_cursor.y);
            assert_eq!(
                terminal.backend().buffer()[(selected_cursor.x, selected_cursor.y)].symbol(),
                ">"
            );
            assert_eq!(
                terminal.backend().buffer()[(selected_cursor.x, selected_cursor.y)].bg,
                Color::Blue
            );
            editor.handle(Input::Char('i'));
            assert_eq!(editor.file_picker().unwrap().query, query);
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap(), query_cursor);
            editor.handle(Input::Escape);
            editor.handle(Input::Ctrl('u'));
            let picker = editor.file_picker().unwrap();
            assert!(picker.focused && !picker.searching && picker.query.is_empty());
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new(query)
            );
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let cursor = terminal.get_cursor_position().unwrap();
            assert_eq!(
                terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
                ">"
            );
            assert!(screen_text(&terminal).contains("other.txt"));
            editor.handle(Input::Char('i'));
            for ch in query.chars() {
                editor.handle(Input::Char(ch));
            }
            editor.handle(Input::Ctrl('u'));
            let picker = editor.file_picker().unwrap();
            assert!(picker.focused && picker.searching && picker.query.is_empty());
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new(query)
            );
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let cursor = terminal.get_cursor_position().unwrap();
            assert_eq!(cursor.y, query_cursor.y);
            assert_eq!(cursor.x, query_cursor.x - query.len() as u16);
            editor.handle(Input::Ctrl('t'));
            for ch in query.chars() {
                editor.handle(Input::Char(ch));
            }
            editor.handle(Input::Ctrl('u'));
            let picker = editor.file_picker().unwrap();
            assert_eq!(picker.view, FileView::List);
            assert!(picker.focused && picker.query.is_empty());
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new(query)
            );
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            assert_eq!(terminal.get_cursor_position().unwrap(), cursor);
            editor.handle(Input::Ctrl('t'));
            editor.handle(Input::Escape);
            editor.handle(Input::Escape);
            if presentation == FilePresentation::Floating {
                assert!(editor.file_picker().is_none());
            } else {
                assert!(!editor.file_picker().unwrap().focused);
            }
            assert_eq!(editor.mode(), mode);
            assert_eq!(editor.selections(), selections);
            assert_eq!(editor.lines(), ["unchanged"]);
        }
    }

    #[test]
    fn explorer_retains_insert_filter_through_focus_and_view_switches() {
        let directory = Directory::new();
        directory.file("src/inner/needle.txt", "");
        directory.file("src/other.txt", "");
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.set_project_root(directory.0.clone());
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 24)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('e'));
        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('n'));
        editor.handle(Input::Char('\t'));
        assert!(!editor.file_picker().unwrap().focused);
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('e'));
        assert!(editor.file_picker().unwrap().searching);
        assert_eq!(editor.file_picker().unwrap().query, "n");
        editor.handle(Input::Ctrl('t'));
        assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        assert_eq!(editor.file_picker().unwrap().query, "n");
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("List"));
        assert_eq!(terminal.get_cursor_position().unwrap().y, 1);
        editor.handle(Input::Ctrl('t'));
        assert_eq!(editor.file_picker().unwrap().view, FileView::Tree);
        assert!(editor.file_picker().unwrap().searching);
        assert_eq!(editor.file_picker().unwrap().query, "n");
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!(terminal.get_cursor_position().unwrap().y, 1);
        editor.handle(Input::Escape);
        assert!(editor.file_picker().unwrap().focused);
        assert!(!editor.file_picker().unwrap().searching);
        assert_eq!(editor.file_picker().unwrap().query, "n");
        editor.handle(Input::Ctrl('t'));
        editor.handle(Input::Ctrl('t'));
        assert!(!editor.file_picker().unwrap().searching);
        assert_eq!(editor.file_picker().unwrap().query, "n");
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("filter: n"));
        let cursor = terminal.get_cursor_position().unwrap();
        assert_eq!(
            terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
            ">"
        );
    }

    #[test]
    fn configured_views_and_view_toggle_render_in_both_presentations_with_scoped_hints() {
        let directory = Directory::new();
        directory.file("folder/file.txt", "");
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.set_project_root(directory.0.clone());
        editor.set_file_picker_view("tree").unwrap();
        editor.set_file_explorer_view("list").unwrap();
        editor.set_file_explorer_side("bottom").unwrap();
        editor.bind("tree", "ctrl+l", None).unwrap();
        editor.bind("tree", "right", None).unwrap();
        editor.bind("tree", "x", Some("core.right".into())).unwrap();
        for key in ["ctrl+j", "ctrl+n", "down", "ctrl+k", "up"] {
            editor.bind("selection", key, None).unwrap();
        }
        editor
            .bind("selection", "j", Some("core.down".into()))
            .unwrap();
        editor
            .bind("selection", "k", Some("core.up".into()))
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(200, 30)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        for (key, expected) in [('o', FileView::Tree), ('e', FileView::List)] {
            editor.handle(Input::Char(' '));
            editor.handle(Input::Char(key));
            assert_eq!(editor.file_picker().unwrap().view, expected);
            if expected == FileView::Tree {
                assert!(editor.file_picker().unwrap().searching);
                editor.handle(Input::Escape);
            }
            for view in [
                expected,
                if expected == FileView::Tree {
                    FileView::List
                } else {
                    FileView::Tree
                },
            ] {
                assert_eq!(editor.file_picker().unwrap().view, view);
                terminal
                    .draw(|frame| {
                        draw(
                            frame,
                            &editor,
                            &mut top,
                            &mut left,
                            &mut syntax,
                            &mut DocumentViewport::default(),
                            &mut WheelPanels::default(),
                        )
                    })
                    .unwrap();
                let text = screen_text(&terminal);
                assert!(text.contains(editor.file_navigation_hint()), "{text}");
                if view == FileView::Tree {
                    assert_ne!(
                        editor.file_navigation_hint(),
                        editor.selection_navigation_hint()
                    );
                    let cursor = terminal.get_cursor_position().unwrap();
                    assert_eq!(
                        terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
                        ">"
                    );
                    editor.handle(Input::Char('x'));
                    assert_eq!(editor.file_picker().unwrap().query, "");
                    assert!(
                        editor
                            .file_picker()
                            .unwrap()
                            .entries()
                            .next()
                            .unwrap()
                            .expanded
                    );
                    let picker = editor.file_picker().unwrap();
                    let was_file = !picker.entries().nth(picker.selected).unwrap().is_dir;
                    editor.handle(Input::Ctrl('h'));
                    if was_file {
                        let picker = editor.file_picker().unwrap();
                        assert!(picker.entries().nth(picker.selected).unwrap().is_dir);
                        assert!(picker.entries().next().unwrap().expanded);
                        editor.handle(Input::Ctrl('h'));
                    }
                    assert!(
                        !editor
                            .file_picker()
                            .unwrap()
                            .entries()
                            .next()
                            .unwrap()
                            .expanded
                    );
                } else {
                    assert_eq!(
                        editor.file_navigation_hint(),
                        editor.selection_navigation_hint()
                    );
                    assert!(text.contains("folder/file.txt"), "{text}");
                }
                editor.handle(Input::Ctrl('t'));
            }
            editor.handle(Input::Escape);
        }
        editor.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains(editor.selection_navigation_hint()));
    }

    #[test]
    fn all_dock_sides_clip_editor_gutter_selection_carets_and_cursor() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                vec!["word ".repeat(40); 20].join("\n"),
            )])
            .unwrap();
        editor.handle(Input::Char('v'));
        editor.handle(Input::Ctrl('a'));
        assert!(editor.selection_count() > 1);
        let area = Rect::new(3, 2, 90, 26);
        let mut terminal = Terminal::with_options(
            ratatui::backend::TestBackend::new(100, 32),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(area),
            },
        )
        .unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('e'));
        assert!(editor.file_picker().unwrap().focused);
        for (name, side) in [
            ("left", DockSide::Left),
            ("right", DockSide::Right),
            ("top", DockSide::Top),
            ("bottom", DockSide::Bottom),
        ] {
            editor.set_file_explorer_side(name).unwrap();
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let workspace = Rect::new(area.x, area.y, area.width, area.height - 2);
            let (editor_area, panel) = dock_layout(workspace, side, true);
            let panel = panel.unwrap();
            assert_eq!(editor_area.area() + panel.area(), workspace.area());
            assert_eq!(editor_area.intersection(panel).area(), 0);
            match side {
                DockSide::Left => assert_eq!(panel.right(), editor_area.x),
                DockSide::Right => assert_eq!(editor_area.right(), panel.x),
                DockSide::Top => assert_eq!(panel.bottom(), editor_area.y),
                DockSide::Bottom => assert_eq!(editor_area.bottom(), panel.y),
            }
            assert!(panel.contains(terminal.get_cursor_position().unwrap()));
            editor.handle(Input::Escape);
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            assert!(editor_area.contains(terminal.get_cursor_position().unwrap()));
            let buffer = terminal.backend().buffer();
            for y in panel.y..panel.bottom() {
                for x in panel.x..panel.right() {
                    assert!(
                        !matches!(
                            buffer[(x, y)].bg,
                            Color::Blue | Color::Magenta | Color::Yellow
                        ),
                        "{side:?}: {x},{y}"
                    );
                }
            }
            assert_eq!(buffer[(editor_area.x + 3, editor_area.y)].symbol(), "w");
            assert!(matches!(
                buffer[(editor_area.x + 3, editor_area.y)].bg,
                Color::Blue | Color::Magenta
            ));
            for y in editor_area.y..editor_area.bottom() {
                for x in editor_area.x..editor_area.x + 3 {
                    assert_eq!(buffer[(x, y)].bg, Color::Reset);
                }
            }
            assert_eq!(buffer[(0, 0)].symbol(), " ");
            editor.handle(Input::Char(' '));
            editor.handle(Input::Char('e'));
            assert!(editor.file_picker().unwrap().focused);
        }
    }

    #[test]
    fn floating_picker_clears_a_centered_overlay_without_moving_editor_regions() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                vec!["x".repeat(120); 30].join("\n"),
            )])
            .unwrap();
        let area = Rect::new(3, 2, 110, 26);
        let mut terminal = Terminal::with_options(
            ratatui::backend::TestBackend::new(120, 32),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(area),
            },
        )
        .unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let before = (top, left);
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('o'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let panel = Rect::new(area.x + 5, area.y + 1, 100, 24);
        assert_eq!((top, left), before);
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(panel.x + 3, panel.y + 1)
        );
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(panel.x, panel.y)].fg, Color::Cyan);
        assert_eq!(buffer[(panel.right() - 2, panel.y + 1)].symbol(), " ");
        assert_eq!(buffer[(area.x + 3, area.y)].symbol(), "x");
        assert_eq!(buffer[(area.x, area.bottom() - 2)].bg, Color::Cyan);
        assert_eq!(buffer[(0, 0)].symbol(), " ");
    }

    #[test]
    fn startup_diagnostic_scrolls_long_unicode_reasons_and_dismisses_without_editing() {
        let directory = Directory::new();
        let source = directory.file("buffer.txt", "keep");
        let config = directory.file("config.rb", "raise \"#{'x' * 160}界END\\nlast reason\"");
        let mut session =
            EditorSession::open(Some(source), vec!["text".into()], Some(&config)).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(110, 26)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("Configuration error"));
        assert!(text.contains("config.rb"));
        assert!(text.contains("default settings and bindings"));
        assert!(text.contains("last reason"));
        assert!(!text.contains("界END"));
        for _ in 0..100 {
            session.handle(Input::Right);
        }
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        let scrolled = screen_text(&terminal);
        assert!(
            scrolled.contains("界") && scrolled.contains("END"),
            "{scrolled}"
        );
        for (width, height) in [(4, 4), (1, 1)] {
            let mut tiny =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            tiny.draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
        }
        session.handle(Input::Enter);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(!screen_text(&terminal).contains("Configuration error"));
        assert_eq!(session.editor().lines(), &["keep"]);
        assert_eq!(session.editor().cursor(), crate::editor::Cursor::default());
    }

    #[test]
    fn picker_conversion_focus_palette_and_closure_preserve_buffer_viewport_cache() {
        let directory = Directory::new();
        let a = directory.file("a", &vec!["a".repeat(80); 30].join("\n"));
        let b = directory.file("b", "other");
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        let a_id = editor.buffer_id();
        for _ in 0..20 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(50, 10)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let before = viewports.offsets[&a_id];
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('o'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], before);
        assert!(screen_text(&terminal).contains("Files"));
        editor.handle(Input::Escape);
        assert!(editor.file_picker().unwrap().focused);
        editor.handle(Input::Escape);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], before);
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('e'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("Explorer"));
        editor.handle(Input::Escape);
        let docked = editor.file_picker().unwrap();
        assert!(!docked.focused);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let dock_offsets = viewports.offsets[&a_id];
        editor.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("Commands"));
        assert_eq!(terminal.get_cursor_position().unwrap().y, 1);
        assert_eq!(viewports.offsets[&a_id], dock_offsets);
        editor.handle(Input::Escape);
        editor.execute(&format!("edit {}", b.display()));
        let b_id = editor.buffer_id();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(editor.file_picker().is_some());
        assert_eq!(viewports.offsets[&b_id], (0, 0));
        editor.execute(&format!("buffer {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], dock_offsets);
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('o'));
        assert_eq!(
            editor.file_picker().unwrap().presentation,
            FilePresentation::Floating
        );
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(screen_text(&terminal).contains("Files"));
        editor.handle(Input::Ctrl('w'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(editor.file_picker().is_none());
        assert_eq!(viewports.offsets[&b_id], (0, 0));
        assert!(screen_text(&terminal).contains("a"));
    }

    #[test]
    fn docked_search_highlight_and_cursor_survive_focus_and_offset_resizes() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "0123456789界e\u{301}z\nsecond".into(),
            )])
            .unwrap();
        editor.handle(Input::Char('/'));
        editor.handle(Input::Char('界'));
        editor.handle(Input::Enter);
        assert!(editor.search_match().is_some());
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('e'));
        let mut terminal = Terminal::with_options(
            ratatui::backend::TestBackend::new(100, 32),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(Rect::new(3, 2, 90, 26)),
            },
        )
        .unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        for (name, side) in [
            ("left", DockSide::Left),
            ("right", DockSide::Right),
            ("top", DockSide::Top),
            ("bottom", DockSide::Bottom),
        ] {
            editor.set_file_explorer_side(name).unwrap();
            for (width, height) in [
                (90, 26),
                (12, 6),
                (8, 2),
                (1, 1),
                (1, 2),
                (0, 1),
                (1, 0),
                (90, 26),
            ] {
                let area = Rect::new(3, 2, width, height);
                terminal.resize(area).unwrap();
                let area = terminal.get_frame().area();
                terminal
                    .draw(|frame| {
                        draw(
                            frame,
                            &editor,
                            &mut top,
                            &mut left,
                            &mut syntax,
                            &mut DocumentViewport::default(),
                            &mut WheelPanels::default(),
                        )
                    })
                    .unwrap();
                if width > 0 && height > 0 {
                    let workspace = Rect::new(
                        area.x,
                        area.y,
                        width,
                        height - u16::from(height >= 3) - u16::from(height >= 2),
                    );
                    let (_, panel) = dock_layout(workspace, side, true);
                    let cursor = terminal.get_cursor_position().unwrap();
                    assert!(
                        panel.unwrap().contains(cursor),
                        "{side:?} {area:?} {panel:?}: {cursor:?}"
                    );
                }
                editor.handle(Input::Escape);
                terminal
                    .draw(|frame| {
                        draw(
                            frame,
                            &editor,
                            &mut top,
                            &mut left,
                            &mut syntax,
                            &mut DocumentViewport::default(),
                            &mut WheelPanels::default(),
                        )
                    })
                    .unwrap();
                if width > 0 && height > 0 {
                    let cursor = terminal.get_cursor_position().unwrap();
                    assert!(area.contains(cursor), "{side:?} {area:?}: {cursor:?}");
                    let workspace = Rect::new(
                        area.x,
                        area.y,
                        width,
                        height - u16::from(height >= 3) - u16::from(height >= 2),
                    );
                    let (editor_area, panel) = dock_layout(workspace, side, false);
                    assert!(editor_area.contains(cursor), "{side:?}: {cursor:?}");
                    let buffer = terminal.backend().buffer();
                    if width == 90 {
                        let mut yellow = 0;
                        for y in editor_area.y..editor_area.bottom() {
                            for x in editor_area.x..editor_area.right() {
                                yellow += usize::from(buffer[(x, y)].bg == Color::Yellow);
                            }
                        }
                        assert!(yellow > 0);
                    }
                    if let Some(panel) = panel {
                        for y in panel.y..panel.bottom() {
                            for x in panel.x..panel.right() {
                                assert_ne!(buffer[(x, y)].bg, Color::Yellow);
                            }
                        }
                    }
                    assert_eq!(buffer[(0, 0)].symbol(), " ");
                }
                editor.handle(Input::Char(' '));
                editor.handle(Input::Char('e'));
                assert!(editor.file_picker().unwrap().focused);
            }
        }
    }

    #[test]
    fn palette_advertises_effective_leader_sequences_after_remapping() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.set_leader(",").unwrap();
        editor.handle(Input::Ctrl('p'));
        for ch in "bnext".chars() {
            editor.handle(Input::Char(ch));
        }
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 10)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains(", b n"));
        assert!(!screen_text(&terminal).contains("Space b n"));
        editor
            .bind("normal", ",", Some("core.command".into()))
            .unwrap();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("unbound"));
        assert!(!screen_text(&terminal).contains(", b n"));
    }

    fn document_wheel(kind: MouseEventKind, column: u16, row: u16) -> MouseEvent {
        MouseEvent {
            kind,
            column,
            row,
            modifiers: KeyModifiers::NONE,
        }
    }

    #[test]
    fn horizontal_wheel_preserves_selection_bounds_display_cells_and_survives_redraw() {
        let directory = Directory::new();
        let text = format!("abc\t界e\u{301}{}", "xyz".repeat(20));
        let path = directory.file("wide.txt", &text);
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        session.handle(Input::Char('v'));
        session.handle(Input::Char('l'));
        let cursor = session.editor().cursor();
        let selections = session.editor().selections();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(16, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollRight, 0, 0)
        ));
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(terminal.backend().buffer()[(3, 0)].symbol(), "界");
        assert_eq!(terminal.backend().buffer()[(5, 0)].symbol(), "e\u{301}");
        let mut shift = document_wheel(MouseEventKind::ScrollDown, 0, 0);
        shift.modifiers = KeyModifiers::SHIFT;
        assert!(viewports.scroll(&mut session, shift));
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(viewports.offsets[&session.editor().buffer_id()], (0, 6));
        for _ in 0..100 {
            viewports.scroll(&mut session, shift);
        }
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(
            viewports.offsets[&session.editor().buffer_id()].1,
            display_column(&text, usize::MAX) + 1 - viewports.document.text_width
        );
        assert_eq!(session.editor().cursor(), cursor);
        assert_eq!(session.editor().selections(), selections);
        assert_eq!(session.editor().lines(), std::slice::from_ref(&text));
        terminal.backend_mut().resize(100, 6);
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert_eq!(viewports.offsets[&session.editor().buffer_id()], (0, 0));
        assert!(screen_text(&terminal).contains("abc"));
        session.handle(Input::Escape);
        session.handle(Input::Char('l'));
        terminal
            .draw(|frame| viewports.draw_session(frame, &mut session))
            .unwrap();
        assert!(terminal.backend().cursor_visible());
    }

    #[test]
    fn wheel_scrolls_rendered_document_three_rows_without_changing_any_selection() {
        let directory = Directory::new();
        let path = directory.file(
            "rows.txt",
            &(0..12)
                .map(|row| format!("abc row-{row:02}"))
                .collect::<Vec<_>>()
                .join("\n"),
        );
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        session.handle(Input::Char('v'));
        session.handle(Input::Char('e'));
        session.handle(Input::Ctrl('a'));
        assert_eq!(session.editor().selection_count(), 12);
        let carets = session.editor().carets();
        let selections = session.editor().selections();
        let cursor = session.editor().cursor();
        let revision = session.editor().text_revision();
        let text = session.editor().lines().to_vec();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(24, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(terminal.backend().cursor_visible());
        for (kind, top) in [
            (MouseEventKind::ScrollDown, 3),
            (MouseEventKind::ScrollDown, 6),
            (MouseEventKind::ScrollDown, 8),
            (MouseEventKind::ScrollDown, 8),
            (MouseEventKind::ScrollUp, 5),
            (MouseEventKind::ScrollUp, 2),
            (MouseEventKind::ScrollUp, 0),
            (MouseEventKind::ScrollUp, 0),
        ] {
            // The gutter belongs to the rendered document hit region too.
            assert!(viewports.scroll(&mut session, document_wheel(kind, 0, 0)));
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert!(
                screen_text(&terminal)
                    .lines()
                    .next()
                    .unwrap()
                    .contains(&format!("row-{top:02}"))
            );
            assert_eq!(
                terminal.backend().cursor_visible(),
                cursor.row >= top && cursor.row < top + 4
            );
            assert_eq!(session.editor().cursor(), cursor);
            assert_eq!(session.editor().carets(), carets);
            assert_eq!(session.editor().selections(), selections);
            assert_eq!(session.editor().text_revision(), revision);
            assert_eq!(session.editor().lines(), text);
        }
        assert!(!viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 0, 5)
        ));
        assert!(!viewports.scroll(&mut session, document_wheel(MouseEventKind::Moved, 0, 0)));
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 0, 0)
        ));
        session.handle(Input::Escape);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(
            screen_text(&terminal)
                .lines()
                .next()
                .unwrap()
                .contains("row-00")
        );
        assert!(terminal.backend().cursor_visible());
    }

    #[test]
    fn queued_typing_preserves_graphemes_history_and_mode_barriers() {
        let directory = Directory::new();
        let path = directory.file("input.txt", "seed");
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        session.handle(Input::Char('i'));
        let mut events = [
            Event::Key(KeyEvent::new(KeyCode::Char('界'), KeyModifiers::NONE)),
            Event::Key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE)),
            Event::Key(KeyEvent::new(KeyCode::Char('x'), KeyModifiers::NONE)),
        ]
        .into_iter();
        let pending = typing_ready(
            &mut session,
            KeyEvent::new(KeyCode::Char('a'), KeyModifiers::NONE),
            || Ok(events.next()),
        )
        .unwrap();
        assert_eq!(session.editor().lines(), ["a界seed"]);
        assert_eq!(session.editor().mode(), Mode::Insert);
        assert!(matches!(pending, Some(Event::Key(key)) if key.code == KeyCode::Esc));
        session.handle(Input::Escape);
        let Some(Event::Key(key)) = events.next() else {
            panic!("remaining command")
        };
        session.handle(translate(key).unwrap());
        assert_eq!(session.editor().lines(), ["aseed"]);
        session.handle(Input::Char('u'));
        assert_eq!(session.editor().lines(), ["a界seed"]);
        session.handle(Input::Char('u'));
        assert_eq!(session.editor().lines(), ["seed"]);
    }

    #[test]
    fn queued_wheel_input_renders_latest_view_without_crossing_key_or_resize_barriers() {
        let directory = Directory::new();
        let text = (0..24)
            .map(|row| format!("row-{row:03}\n"))
            .collect::<String>();
        let path = directory.file("rows.txt", &text);
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(20, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        let down = Event::Mouse(document_wheel(MouseEventKind::ScrollDown, 1, 1));
        let up = Event::Mouse(document_wheel(MouseEventKind::ScrollUp, 1, 1));
        for barrier in [
            Event::Key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE)),
            Event::Resize(40, 12),
        ] {
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            let mut queued = [
                down.clone(),
                up.clone(),
                down.clone(),
                barrier.clone(),
                down.clone(),
            ]
            .into_iter();
            let (redraw, pending) = viewports
                .scroll_ready(
                    &mut session,
                    document_wheel(MouseEventKind::ScrollDown, 1, 1),
                    || Ok(queued.next()),
                )
                .unwrap();
            assert!(redraw);
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert!(
                screen_text(&terminal)
                    .lines()
                    .next()
                    .unwrap()
                    .contains("row-006")
            );
            assert_eq!(pending, Some(barrier));
            assert_eq!(queued.next(), Some(down.clone()));
            assert_eq!(session.editor().cursor(), Cursor::default());
            assert_eq!(session.editor().mode(), Mode::Normal);
            assert!(!terminal.backend().cursor_visible());
            session.handle(Input::Up);
        }

        assert_eq!(session.editor().lines().join("\n"), text);
    }

    #[test]
    fn no_op_navigation_restores_caret_following_through_core_dispatch() {
        let directory = Directory::new();
        let path = directory.file("rows.txt", &["row"; 12].join("\n"));
        let mut session = EditorSession::open(Some(path.clone()), vec![], None).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(20, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        for motion in [Input::Char('k'), Input::Up, Input::Home] {
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert!(viewports.scroll(
                &mut session,
                document_wheel(MouseEventKind::ScrollDown, 2, 0)
            ));
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert!(!terminal.backend().cursor_visible());
            session.handle(motion);
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert_eq!(session.editor().cursor(), Cursor::default());
            assert_eq!(viewports.offsets[&session.editor().buffer_id()].0, 0);
            assert!(terminal.backend().cursor_visible());
        }
        let mut editor = Editor::open(Some(path.clone()), vec![]).unwrap();
        // A remapped motion and a disabled default demonstrate that intent is
        // emitted by the resolved core action, not frontend key spelling.
        editor.bind("normal", "x", Some("core.up".into())).unwrap();
        editor.bind("normal", "k", None).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(20, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        for navigation in 0..3 {
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            let buffer_id = editor.buffer_id();
            viewports.offsets.get_mut(&buffer_id).unwrap().0 = 3;
            viewports.document.manual = Some(ManualViewport {
                buffer_id,
                revision: editor.text_revision(),
                caret_reveal_revision: editor.caret_reveal_revision(),
                mode: editor.mode(),
                cursor: editor.cursor(),
                carets: editor.carets(),
                selections: editor.selections(),
            });
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            assert!(!terminal.backend().cursor_visible());
            editor.handle(Input::Char('k'));
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            assert!(!terminal.backend().cursor_visible());
            match navigation {
                0 => {
                    editor.handle(Input::Char('x'));
                }
                1 => editor
                    .navigate_to(
                        path.clone(),
                        crate::plugin::TextPosition { row: 0, column: 0 },
                    )
                    .unwrap(),
                2 => {
                    editor.execute(&format!("buffer {buffer_id}"));
                }
                _ => unreachable!(),
            }
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            assert_eq!(editor.cursor(), Cursor::default());
            assert_eq!(viewports.offsets[&buffer_id].0, 0);
            assert!(terminal.backend().cursor_visible());
            assert!(
                screen_text(&terminal)
                    .lines()
                    .next()
                    .unwrap()
                    .contains("row")
            );
        }
    }

    #[test]
    fn manual_document_view_survives_idle_resize_and_palette_then_follows_navigation_and_edits() {
        let directory = Directory::new();
        let path = directory.file(
            "rows.txt",
            &(0..20)
                .map(|row| format!("row-{row:02}"))
                .collect::<Vec<_>>()
                .join("\n"),
        );
        let other = directory.file("other.txt", "other");
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let buffer_id = session.editor().buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(30, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        for _ in 0..2 {
            assert!(viewports.scroll(
                &mut session,
                document_wheel(MouseEventKind::ScrollDown, 4, 0)
            ));
        }
        session.poll();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(
            screen_text(&terminal)
                .lines()
                .next()
                .unwrap()
                .contains("row-06")
        );
        assert!(!terminal.backend().cursor_visible());
        terminal.backend_mut().resize(30, 8);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(
            screen_text(&terminal)
                .lines()
                .next()
                .unwrap()
                .contains("row-06")
        );
        session.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 4, 0)
        ));
        session.handle(Input::Escape);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(
            screen_text(&terminal)
                .lines()
                .next()
                .unwrap()
                .contains("row-06")
        );
        assert_eq!(session.editor().cursor(), Cursor::default());
        session.handle(Input::Down);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(
            screen_text(&terminal)
                .lines()
                .next()
                .unwrap()
                .contains("row-01")
        );
        assert!(terminal.backend().cursor_visible());

        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 4, 0)
        ));
        session.handle(Input::Char('i'));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(terminal.backend().cursor_visible());
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 4, 0)
        ));
        session.handle(Input::Char('z'));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(terminal.backend().cursor_visible());
        session.handle(Input::Escape);
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 4, 0)
        ));
        session.execute(&format!("edit {}", other.display()));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(screen_text(&terminal).starts_with("1 other"));
        session.execute(&format!("buffer {buffer_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(terminal.backend().cursor_visible());
        assert!(
            screen_text(&terminal)
                .lines()
                .next()
                .unwrap()
                .contains("zrow-01")
        );
    }

    #[test]
    fn manual_document_view_hides_horizontal_offscreen_caret_and_clamps_tiny_viewports() {
        let directory = Directory::new();
        let path = directory.file("long.txt", "abcdefghijk");
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        for _ in 0..8 {
            session.handle(Input::Right);
        }
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(20, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 2, 0)
        ));
        terminal.backend_mut().resize(8, 6);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(!terminal.backend().cursor_visible());
        assert!(screen_text(&terminal).starts_with("1 abcdef"));
        assert_eq!(session.editor().cursor(), Cursor { row: 0, column: 8 });
        session.handle(Input::Left);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(terminal.backend().cursor_visible());
        assert_eq!(terminal.backend().cursor_position().x, 7);
        for (width, height) in [(1, 1), (2, 2), (0, 0)] {
            terminal.backend_mut().resize(width, height);
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert_eq!(
                viewports.scroll(
                    &mut session,
                    document_wheel(MouseEventKind::ScrollDown, 0, 0)
                ),
                width > 0 && height > 0,
            );
            terminal
                .draw(|frame| viewports.draw(frame, session.editor_mut()))
                .unwrap();
            assert_eq!(viewports.offsets[&session.editor().buffer_id()].0, 0);
        }
    }

    #[test]
    fn wrapped_document_renders_continuations_selection_and_insertion_caret() {
        let directory = Directory::new();
        let source = "abcdefghijklmnop\ntail";
        let path = directory.file("wrapped.txt", source);
        let mut editor = Editor::open(Some(path), vec![]).unwrap();
        editor.execute("word_wrap.toggle");
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(10, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let screen = screen_text(&terminal);
        let rows: Vec<_> = screen.lines().collect();
        assert_eq!(rows[0], "1 abcdefgh");
        assert_eq!(rows[1], "  ijklmnop");
        assert_eq!(rows[2], "          ");
        assert_eq!(rows[3], "1 tail    ");
        editor.handle(Input::Char('v'));
        for _ in 0..10 {
            editor.handle(Input::Right);
        }
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.get_cursor_position().unwrap(), Position::new(4, 1));
        assert_eq!(terminal.backend().buffer()[(2, 1)].bg, Color::Blue);
        assert_eq!(terminal.backend().buffer()[(3, 1)].bg, Color::Blue);
        editor.handle(Input::Escape);
        editor.handle(Input::End);
        editor.handle(Input::Char('a'));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(terminal.get_cursor_position().unwrap(), Position::new(2, 2));
        assert_eq!(editor.lines().join("\n"), source);
        assert!(!editor.dirty());
    }

    #[test]
    fn wrapped_wheel_moves_visual_rows_and_resize_and_toggle_restore_following() {
        let directory = Directory::new();
        let source = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        let path = directory.file("wrapped.txt", source);
        let mut session = EditorSession::open(Some(path), vec![], None).unwrap();
        let id = session.editor().buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(10, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        for _ in 0..12 {
            session.handle(Input::Right);
        }
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        let original_left = viewports.offsets[&id].1;
        assert!(original_left > 0);
        session.execute("word_wrap.toggle");
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollRight, 4, 0)
        ));
        assert_eq!(viewports.offsets[&id].1, original_left);
        assert!(viewports.document.manual.is_none());
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 4, 0)
        ));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(!terminal.backend().cursor_visible());
        assert!(viewports.scroll(
            &mut session,
            document_wheel(MouseEventKind::ScrollDown, 4, 0)
        ));
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        terminal.backend_mut().resize(14, 6);
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert!(viewports.document.manual.is_none());
        assert!(terminal.backend().cursor_visible());
        assert_eq!(session.editor().cursor(), Cursor { row: 0, column: 12 });
        session.execute("word_wrap.toggle");
        terminal
            .draw(|frame| viewports.draw(frame, session.editor_mut()))
            .unwrap();
        assert_eq!(viewports.offsets[&id].1, original_left);
        assert_eq!(session.editor().lines().join("\n"), source);
    }

    #[test]
    fn wrapped_unicode_uses_original_tab_stops_and_queries_visible_source_rows() {
        let directory = Directory::new();
        let source = format!("#a\t界e\u{301} z\n{}", vec!["# unseen"; 100].join("\n"));
        let path = directory.file("wrapped.py", &source);
        let mut editor = Editor::open(Some(path), vec![]).unwrap();
        editor
            .replace_semantic_tokens(
                editor.buffer_id(),
                editor.text_revision(),
                Some(Arc::from([semantic_token(
                    0,
                    3,
                    5,
                    SemanticTokenKind::Property,
                    0,
                )])),
            )
            .unwrap();
        editor
            .replace_diagnostics(
                "fixture",
                editor.buffer_id(),
                editor.text_revision(),
                vec![annotation(
                    (0, 2),
                    (0, 5),
                    DiagnosticSeverity::Warning,
                    "wrapped range",
                )],
            )
            .unwrap();
        editor.execute("word_wrap.toggle");
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(8, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.document.text_width, 4);
        assert_eq!(
            viewports
                .document
                .visible
                .iter()
                .map(|&(row, part, _)| (row, part))
                .collect::<Vec<_>>(),
            [(0, 0), (0, 1), (0, 2), (1, 0)]
        );
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(4, 0)].symbol(), "#");
        assert_eq!(buffer[(6, 0)].symbol(), " ");
        assert_eq!(buffer[(4, 1)].symbol(), "界");
        assert_eq!(buffer[(6, 1)].symbol(), "e\u{301}");
        for x in [4, 6] {
            assert_eq!(buffer[(x, 1)].fg, Color::Blue);
            assert!(buffer[(x, 1)].modifier.contains(Modifier::UNDERLINED));
            assert_eq!(buffer[(x, 1)].underline_color, Color::Yellow);
        }
        assert_eq!(buffer[(4, 2)].fg, Color::DarkGray);
        assert!(viewports.syntax[&editor.buffer_id()].line(2).is_empty());
        assert_eq!(buffer[(4, 2)].symbol(), "z");
        assert_eq!(editor.lines().join("\n"), source);
        editor.handle(Input::Down);
        assert_eq!(editor.cursor().row, 1);
    }

    #[test]
    fn buffer_switches_restore_independent_vertical_and_horizontal_viewports() {
        let directory = Directory::new();
        let a = directory.file("a", &vec!["a".repeat(50); 20].join("\n"));
        let b = directory.file("b", &vec!["b".repeat(40); 20].join("\n"));
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        let a_id = editor.buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(16, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        for _ in 0..14 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], (11, 37));
        for _ in 0..2 {
            editor.handle(Input::Up);
        }
        for _ in 0..3 {
            editor.handle(Input::Left);
        }
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let a_viewport = viewports.offsets[&a_id];
        let a_cursor = terminal.get_cursor_position().unwrap();
        assert_eq!(a_viewport, (11, 37));

        editor.execute(&format!("edit {}", b.display()));
        let b_id = editor.buffer_id();
        assert_ne!(a_id, b_id);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&b_id], (0, 0));
        for _ in 0..8 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        editor.handle(Input::Up);
        editor.handle(Input::Left);
        editor.handle(Input::Left);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let b_viewport = viewports.offsets[&b_id];
        let b_cursor = terminal.get_cursor_position().unwrap();
        assert_eq!(b_viewport, (5, 27));

        editor.execute(&format!("buffer {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], a_viewport);
        assert_eq!(terminal.get_cursor_position().unwrap(), a_cursor);
        assert_eq!(
            terminal.backend().buffer()[(a_cursor.x, a_cursor.y)].symbol(),
            "a"
        );
        editor.execute("bnext");
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(editor.buffer_id(), b_id);
        assert_eq!(viewports.offsets[&b_id], b_viewport);
        assert_eq!(terminal.get_cursor_position().unwrap(), b_cursor);
    }

    #[test]
    fn closing_inactive_buffer_retires_its_viewport_without_moving_active_buffer() {
        let directory = Directory::new();
        let a = directory.file("a", &vec!["a".repeat(50); 20].join("\n"));
        let b = directory.file("b", &vec!["b".repeat(40); 20].join("\n"));
        let c = directory.file("c", "new buffer");
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        let a_id = editor.buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(16, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        for _ in 0..14 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        editor.execute(&format!("edit {}", b.display()));
        let b_id = editor.buffer_id();
        for _ in 0..8 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let b_viewport = viewports.offsets[&b_id];
        let b_cursor = terminal.get_cursor_position().unwrap();
        assert_eq!(viewports.offsets.len(), 2);

        editor.execute(&format!("bdelete {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(editor.buffer_id(), b_id);
        assert!(!editor.has_buffer(a_id));
        assert!(!viewports.offsets.contains_key(&a_id));
        assert_eq!(viewports.offsets.len(), 1);
        assert_eq!(viewports.offsets[&b_id], b_viewport);
        assert_eq!(terminal.get_cursor_position().unwrap(), b_cursor);
        editor.execute(&format!("edit {}", c.display()));
        let c_id = editor.buffer_id();
        assert!(c_id > b_id);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&c_id], (0, 0));
        assert!(!viewports.offsets.contains_key(&a_id));
    }

    #[test]
    fn restoring_buffer_after_narrow_resize_clamps_caret_inside_text_region() {
        let directory = Directory::new();
        let a = directory.file("a", &vec!["a".repeat(50); 20].join("\n"));
        let b = directory.file("b", "other");
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        let a_id = editor.buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(24, 8)).unwrap();
        let mut viewports = BufferViewports::default();
        for _ in 0..14 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], (9, 29));
        editor.execute(&format!("edit {}", b.display()));
        let b_id = editor.buffer_id();
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        terminal.backend_mut().resize(4, 4);
        terminal
            .resize(ratatui::layout::Rect::new(0, 0, 4, 4))
            .unwrap();
        editor.execute(&format!("buffer {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert_eq!(viewports.offsets[&a_id], (13, 49));
        assert_eq!(viewports.offsets[&b_id], (0, 0));
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(3, 1)
        );

        for (width, height) in [(1, 1), (24, 8)] {
            let area = ratatui::layout::Rect::new(0, 0, width, height);
            terminal.backend_mut().resize(width, height);
            terminal.resize(area).unwrap();
            terminal
                .draw(|frame| viewports.draw(frame, &mut editor))
                .unwrap();
            let cursor = terminal.get_cursor_position().unwrap();
            assert!(area.contains(cursor), "{area:?}: {cursor:?}");
            assert_eq!(
                terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
                "a"
            );
            assert_eq!(viewports.offsets[&b_id], (0, 0));
        }
    }

    #[test]
    fn status_identifies_active_buffer_and_restored_visual_selection_count() {
        let directory = Directory::new();
        let a = directory.file("a", "word\nword\nword");
        let b = directory.file("b", "other");
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        let a_id = editor.buffer_id();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(240, 6)).unwrap();
        let mut viewports = BufferViewports::default();
        editor.handle(Input::Char('v'));
        editor.handle(Input::Ctrl('a'));
        assert_eq!(editor.selection_count(), 3);
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        assert!(!screen_text(&terminal).contains("[buffer"));
        editor.execute(&format!("edit {}", b.display()));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let text = screen_text(&terminal);
        assert!(!text.contains("3 selections"), "{text}");
        editor.execute(&format!("buffer {a_id}"));
        terminal
            .draw(|frame| viewports.draw(frame, &mut editor))
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("3 selections"), "{text}");
        let (top, left) = viewports.offsets[&a_id];
        for selection in editor.selections() {
            let x = 2 + (selection.start.column - left) as u16;
            let y = (selection.start.row - top) as u16;
            assert!(matches!(
                terminal.backend().buffer()[(x, y)].bg,
                Color::Blue | Color::Magenta
            ));
        }
    }

    #[test]
    fn pending_motion_count_is_visible_and_escape_cancels_without_moving() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(["row"; 12].join("\n"))])
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(60, 6)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        editor.handle(Input::Char('1'));
        editor.handle(Input::Char('0'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("count: 10"));
        editor.handle(Input::Escape);
        editor.handle(Input::Down);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(!screen_text(&terminal).contains("count:"));
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(3, 1)
        );
    }

    #[test]
    fn gutter_tracks_scrolled_rows_without_scrolling_with_text() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "0123456789界z\n".repeat(11),
            )])
            .unwrap();
        for _ in 0..10 {
            editor.handle(Input::Down);
        }
        editor.handle(Input::End);
        let area = ratatui::layout::Rect::new(3, 2, 8, 5);
        let mut terminal = Terminal::with_options(
            ratatui::backend::TestBackend::new(20, 10),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(area),
            },
        )
        .unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!((top, left), (8, 8));
        let buffer = terminal.backend().buffer();
        for (y, expected) in [(2, " 2 "), (3, " 1 "), (4, "11 ")] {
            let number: String = (3..6).map(|x| buffer[(x, y)].symbol()).collect();
            assert_eq!(number, expected);
            assert_eq!(buffer[(6, y)].symbol(), "8");
            assert_eq!(buffer[(3, y)].bg, Color::Reset);
        }
        assert!(buffer[(3, 4)].modifier.contains(Modifier::BOLD));
        assert!(!buffer[(3, 3)].modifier.contains(Modifier::BOLD));
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(10, 4)
        );
        editor.handle(Input::Down);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        let last_number: String = (3..6).map(|x| buffer[(x, 4)].symbol()).collect();
        assert_eq!(last_number, "12 ");
        assert_eq!(buffer[(6, 4)].symbol(), " ");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(6, 4)
        );
        editor.handle(Input::Up);
        editor.handle(Input::Up);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        for (y, expected) in [(2, "10 "), (3, " 1 "), (4, " 2 ")] {
            let number: String = (3..6).map(|x| buffer[(x, y)].symbol()).collect();
            assert_eq!(number, expected);
        }
        editor.handle(Input::Ctrl('e'));
        assert_eq!(editor.selection_count(), 2);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        for (y, expected) in [(2, " 1 "), (3, "11 "), (4, " 1 ")] {
            let number: String = (3..6).map(|x| buffer[(x, y)].symbol()).collect();
            assert_eq!(number, expected);
        }
    }

    #[test]
    fn gutter_resizes_at_digit_boundaries_and_yields_to_narrow_text() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        for count in [9usize, 10, 100] {
            editor
                .apply(vec![crate::editor::Effect::Replace(
                    vec!["x"; count].join("\n"),
                )])
                .unwrap();
            let digits = count.ilog10() as u16 + 1;
            let gutter_width = digits + 1;
            for width in [12, gutter_width, gutter_width + 1, 1] {
                let mut terminal =
                    Terminal::new(ratatui::backend::TestBackend::new(width, 4)).unwrap();
                terminal
                    .draw(|frame| {
                        draw(
                            frame,
                            &editor,
                            &mut top,
                            &mut left,
                            &mut syntax,
                            &mut DocumentViewport::default(),
                            &mut WheelPanels::default(),
                        )
                    })
                    .unwrap();
                let cursor = terminal.get_cursor_position().unwrap();
                let buffer = terminal.backend().buffer();
                let text_x = if width > gutter_width {
                    gutter_width
                } else {
                    0
                };
                assert_eq!(buffer[(text_x, 0)].symbol(), "x");
                assert_eq!(cursor, ratatui::layout::Position::new(text_x, 0));
                if text_x > 0 {
                    let number: String = (0..text_x).map(|x| buffer[(x, 0)].symbol()).collect();
                    assert_eq!(
                        number,
                        format!("{:>digits$} ", 1, digits = usize::from(digits))
                    );
                }
            }
        }
        editor
            .apply(vec![crate::editor::Effect::Replace(String::new())])
            .unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(8, 5)).unwrap();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(0, 0)].symbol(), "1");
        assert_eq!(buffer[(0, 1)].symbol(), " ");
        assert_eq!(buffer[(0, 2)].symbol(), " ");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(2, 0)
        );
    }

    #[test]
    fn palette_renders_query_no_matches_and_restores_underlying_prompt() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.handle(Input::Char('/'));
        for ch in "saved search".chars() {
            editor.handle(Input::Char(ch));
        }
        editor.handle(Input::Ctrl('p'));
        for ch in "no-such-command".chars() {
            editor.handle(Input::Char(ch));
        }
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 16)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("> no-such-command"), "{text}");
        assert!(text.contains("No matching commands"), "{text}");
        assert!(text.contains("SEARCH"), "{text}");
        assert_eq!(terminal.get_cursor_position().unwrap().y, 1);
        editor.handle(Input::Enter);
        assert!(editor.palette().is_some());
        editor.handle(Input::Escape);
        assert_eq!(editor.mode(), Mode::Search);
        assert_eq!(editor.command_line(), "saved search");
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("/saved search"));
    }

    #[test]
    fn palette_window_follows_keyboard_selection() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.handle(Input::Ctrl('p'));
        for _ in 0..20 {
            editor.handle(Input::Ctrl('j'));
        }
        editor.handle(Input::Ctrl('k'));
        editor.handle(Input::Ctrl('n'));
        let palette = editor.palette().unwrap();
        assert_eq!(palette.selected, 20);
        let selected = &palette.entries[palette.selected];
        let first_name = palette.entries[0].name.clone();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 10)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains(&selected.name), "{text}");
        assert!(!text.contains(&format!("({first_name})")), "{text}");
        let buffer = terminal.backend().buffer();
        let selected_y = (2..10).find(|&y| buffer[(1, y)].symbol() == ">").unwrap();
        assert_eq!(buffer[(1, selected_y)].bg, Color::Blue);
        assert!(buffer[(1, selected_y)].modifier.contains(Modifier::BOLD));
        assert_eq!(terminal.get_cursor_position().unwrap().y, 1);
    }

    #[test]
    fn palette_shows_effective_bindings_and_dimmed_mode_ineligible_commands() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .register(crate::editor::Feature {
                name: "sample".into(),
                required_capabilities: vec![],
                commands: vec!["greet".into()],
                core: false,
            })
            .unwrap();
        editor.bind("normal", "g", Some("greet".into())).unwrap();
        editor.bind("normal", "g", None).unwrap();
        editor
            .bind("normal", "ctrl+x", Some("greet".into()))
            .unwrap();
        editor.handle(Input::Ctrl('p'));
        for ch in "greet".chars() {
            editor.handle(Input::Char(ch));
        }
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 10)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("sample | Ctrl+x | NORMAL"), "{text}");
        assert!(!text.contains("unbound"), "{text}");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('i'));
        editor.handle(Input::Ctrl('p'));
        for ch in "greet".chars() {
            editor.handle(Input::Char(ch));
        }
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("sample | unbound | NORMAL"), "{text}");
        assert!(text.contains("INSERT"), "{text}");
        let cell = &terminal.backend().buffer()[(1, 2)];
        assert!(cell.modifier.contains(Modifier::DIM));
        assert_eq!(cell.bg, Color::Blue);
        editor.handle(Input::Enter);
        assert!(editor.palette().is_some());
        assert_eq!(editor.mode(), Mode::Insert);
    }

    #[test]
    fn palette_query_scrolls_graphemes_tabs_and_wide_cells_on_tiny_offset_areas() {
        let editor = Editor::open(None, vec![]).unwrap();
        let palette = Palette {
            query: "long\t界e\u{301}z".into(),
            entries: vec![],
            selected: 0,
        };
        for (width, height) in [(12, 6), (8, 2), (1, 1), (1, 2), (8, 1), (12, 6)] {
            let area = ratatui::layout::Rect::new(3, 2, width, height);
            let mut terminal = Terminal::with_options(
                ratatui::backend::TestBackend::new(24, 12),
                ratatui::TerminalOptions {
                    viewport: ratatui::Viewport::Fixed(area),
                },
            )
            .unwrap();
            terminal
                .draw(|frame| {
                    draw_palette(
                        frame,
                        &palette,
                        area,
                        Mode::Visual,
                        editor.selection_navigation_hint(),
                    )
                })
                .unwrap();
            let cursor = terminal.get_cursor_position().unwrap();
            assert!(area.contains(cursor), "{area:?}: {cursor:?}");
            let bordered = height >= 4 && width >= 4;
            let query_x = area.x + u16::from(bordered);
            let query_y = area.y + u16::from(bordered);
            let query_width = width - 2 * u16::from(bordered);
            assert_eq!(cursor.x, query_x + query_width - 1);
            assert_eq!(cursor.y, query_y);
            let query = format!("> {}", palette.query);
            let offset =
                display_column(&query, usize::MAX).saturating_sub(usize::from(query_width) - 1);
            let mut expected = ratatui::buffer::Buffer::empty(ratatui::layout::Rect::new(
                query_x,
                query_y,
                query_width,
                1,
            ));
            use ratatui::widgets::Widget;
            Paragraph::new(visible_line(&query, offset, usize::from(query_width)))
                .render(expected.area, &mut expected);
            for x in query_x..query_x + query_width {
                assert_eq!(
                    terminal.backend().buffer()[(x, query_y)].symbol(),
                    expected[(x, query_y)].symbol()
                );
            }
            assert_eq!(terminal.backend().buffer()[(0, 0)].symbol(), " ");
        }
        for (width, height) in [(0, 1), (1, 0), (0, 0)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| {
                    let area = frame.area();
                    draw_palette(
                        frame,
                        &palette,
                        area,
                        Mode::Normal,
                        editor.selection_navigation_hint(),
                    )
                })
                .unwrap();
        }
    }

    #[test]
    fn opening_palette_does_not_scroll_underlying_editor_viewport() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "first\nsecond\n0123456789界z".into(),
            )])
            .unwrap();
        editor.handle(Input::Down);
        editor.handle(Input::Down);
        editor.handle(Input::End);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(8, 4)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let viewport = (top, left);
        editor.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!((top, left), viewport);
        editor.handle(Input::Ctrl('p'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!((top, left), viewport);
        let cursor = terminal.get_cursor_position().unwrap();
        assert_eq!(
            terminal.backend().buffer()[(cursor.x, cursor.y)].symbol(),
            "z"
        );
    }

    #[test]
    fn layout_keeps_scrolled_content_and_prompts_inside_offset_regions() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "first\nsecond\n0123456789界z".into(),
            )])
            .unwrap();
        editor.handle(Input::Down);
        editor.handle(Input::Down);
        editor.handle(Input::End);
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        for prompting in [false, true] {
            if prompting {
                editor.handle(Input::Char('/'));
                for ch in "long query".chars() {
                    editor.handle(Input::Char(ch));
                }
            }
            for height in [4, 2, 1, 4] {
                let area = ratatui::layout::Rect::new(3, 2, 8, height);
                let mut terminal = Terminal::with_options(
                    ratatui::backend::TestBackend::new(20, 10),
                    ratatui::TerminalOptions {
                        viewport: ratatui::Viewport::Fixed(area),
                    },
                )
                .unwrap();
                terminal
                    .draw(|frame| {
                        draw(
                            frame,
                            &editor,
                            &mut top,
                            &mut left,
                            &mut syntax,
                            &mut DocumentViewport::default(),
                            &mut WheelPanels::default(),
                        )
                    })
                    .unwrap();
                let cursor = terminal.get_cursor_position().unwrap();
                assert!(area.contains(cursor), "{area:?}: {cursor:?}");
                let buffer = terminal.backend().buffer();
                if prompting {
                    assert_eq!(cursor.y, area.bottom() - 1);
                    assert_eq!(buffer[(area.x, cursor.y)].symbol(), "g");
                } else {
                    assert_eq!(buffer[(cursor.x, cursor.y)].symbol(), "z");
                }
                if height >= 3 {
                    assert_eq!(buffer[(area.x, area.bottom() - 2)].bg, Color::Cyan);
                } else {
                    for y in area.y..area.bottom() {
                        assert_ne!(buffer[(area.x, y)].bg, Color::Cyan);
                    }
                }
                assert_eq!(buffer[(0, 0)].symbol(), " ");
            }
        }
    }

    #[test]
    fn tabs_and_wide_graphemes_scroll_in_terminal_cells() {
        let text = "a\t界e\u{301}z";
        assert_eq!(display_column(text, 4), 7);
        assert_eq!(visible_line(text, 2, 5), "  界e\u{301}");
        assert_eq!(visible_line(text, 5, 2), " e\u{301}");
    }

    #[test]
    fn selection_set_renders_all_ranges_and_counts_offscreen_targets() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "界\n界\n界\n界\n界".into(),
            )])
            .unwrap();
        editor.handle(Input::Home);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Ctrl('a'));
        assert_eq!(editor.selection_count(), 5);
        assert_eq!(editor.selections().len(), 5);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(48, 4)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        for selection in editor.selections() {
            if selection.start.row >= top && selection.start.row < top + 2 {
                let y = (selection.start.row - top) as u16;
                assert!(matches!(buffer[(2, y)].bg, Color::Blue | Color::Magenta));
            }
        }
        let status: String = (0..48).map(|x| buffer[(x, 2)].symbol()).collect();
        assert!(status.contains("5 selections"), "{status}");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(2, (editor.cursor().row - top) as u16)
        );
    }

    #[test]
    fn secondary_carets_render_on_empty_lines_and_at_line_end() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace("a\n\n界".into())])
            .unwrap();
        editor.handle(Input::Home);
        editor.handle(Input::Ctrl('e'));
        editor.handle(Input::Ctrl('e'));
        assert_eq!(editor.selection_count(), 3);
        editor.handle(Input::Char('A'));
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(48, 5)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        for caret in editor.carets() {
            let x = 2 + display_column(&editor.lines()[caret.row], caret.column) as u16;
            assert_eq!(buffer[(x, caret.row as u16)].symbol(), " ");
            if caret != editor.cursor() {
                assert_eq!(buffer[(x, caret.row as u16)].bg, Color::Magenta);
            }
        }
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(
                2 + display_column(&editor.lines()[editor.cursor().row], editor.cursor().column)
                    as u16,
                editor.cursor().row as u16
            )
        );
    }

    #[test]
    fn linewise_selection_highlights_copied_text_and_newlines_without_filling_rows() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "\t界e\u{301}  \n\n".into(),
            )])
            .unwrap();
        editor.handle(Input::Char('V'));
        editor.handle(Input::Down);
        editor.handle(Input::Down);
        let before = (editor.lines().to_vec(), editor.cursor(), editor.carets());
        for width in [16, 3, 1] {
            let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(width, 6)).unwrap();
            let (mut top, mut left) = (0, 0);
            let frame = terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut SyntaxCache::new(),
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
            let buffer = frame.buffer;
            if width == 16 {
                let status: String = (0..width).map(|x| buffer[(x, 4)].symbol()).collect();
                assert!(status.contains("VISUAL LINE"), "{status}");
            }
            let gutter = if width > 2 { 2 } else { 0 };
            for row in 0..3 {
                for x in 0..gutter {
                    assert_ne!(buffer[(x, row)].bg, Color::Blue);
                }
                let selected_width = if row == 0 { 10 } else { 1 };
                for x in gutter..width {
                    if x - gutter < selected_width {
                        assert_eq!(
                            buffer[(x, row)].bg,
                            Color::Blue,
                            "width {width}, row {row}, x {x}"
                        );
                    } else {
                        assert_ne!(buffer[(x, row)].bg, Color::Blue);
                    }
                }
            }
            for x in 0..width {
                assert_ne!(buffer[(x, 3)].bg, Color::Blue);
            }
        }
        assert_eq!(
            before,
            (editor.lines().to_vec(), editor.cursor(), editor.carets())
        );
        editor.handle(Input::Up);
        editor.handle(Input::Up);
        editor.handle(Input::End);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(5, 3)).unwrap();
        let (mut top, mut left) = (0, 0);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut SyntaxCache::new(),
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(left > 0);
        let buffer = terminal.backend().buffer();
        for x in 0..2 {
            assert_ne!(buffer[(x, 0)].bg, Color::Blue);
        }
        for x in 2..5 {
            assert_eq!(buffer[(x, 0)].bg, Color::Blue);
        }
    }

    #[test]
    fn visual_selection_highlights_graphemes_newlines_and_clipped_ranges_over_search() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "a\t界e\u{301}z\n\nxy".into(),
            )])
            .unwrap();
        editor.handle(Input::Char('/'));
        for ch in "界e\u{301}".chars() {
            editor.handle(Input::Char(ch));
        }
        editor.handle(Input::Enter);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Left);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(12, 6)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        for x in [1, 2, 3, 4] {
            assert_eq!(buffer[(2 + x, 0)].bg, Color::Blue);
        }
        assert_eq!(buffer[(6, 0)].symbol(), "界");
        assert_eq!(buffer[(8, 0)].bg, Color::Yellow);
        editor.handle(Input::Down);
        editor.handle(Input::Down);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(10, 0)].symbol(), " ");
        assert_eq!(buffer[(10, 0)].bg, Color::Blue);
        assert_eq!(buffer[(2, 1)].bg, Color::Blue);
        assert_eq!(buffer[(2, 2)].bg, Color::Blue);
        assert_ne!(buffer[(3, 2)].bg, Color::Blue);

        editor.handle(Input::Up);
        editor.handle(Input::Up);
        editor.handle(Input::End);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(7, 6)).unwrap();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(left, 4);
        assert_eq!(buffer[(2, 0)].symbol(), "界");
        assert_eq!(buffer[(4, 0)].symbol(), "e\u{301}");
        assert_eq!(buffer[(6, 0)].symbol(), " ");
        for x in [0, 2, 3, 4] {
            assert_eq!(buffer[(2 + x, 0)].bg, Color::Blue);
        }
        assert_ne!(buffer[(2, 1)].bg, Color::Blue);
        editor.handle(Input::Escape);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(2, 0)].bg, Color::Yellow);
        assert_eq!(buffer[(4, 0)].bg, Color::Yellow);
        assert_ne!(buffer[(5, 0)].bg, Color::Blue);
        assert_ne!(buffer[(6, 0)].bg, Color::Blue);
    }

    #[test]
    fn active_search_highlight_uses_display_cells_and_clips_with_horizontal_scroll() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                "a\t界e\u{301}zz".into(),
            )])
            .unwrap();
        editor.handle(Input::Char('/'));
        for ch in "\t界e\u{301}".chars() {
            editor.handle(Input::Char(ch));
        }
        editor.handle(Input::Enter);
        editor.handle(Input::End);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(7, 5)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(left, 4);
        assert_eq!(buffer[(2, 0)].symbol(), "界");
        assert_eq!(buffer[(4, 0)].symbol(), "e\u{301}");
        for x in [0, 2] {
            assert_eq!(buffer[(2 + x, 0)].bg, Color::Yellow);
        }
        for x in 3..5 {
            assert_ne!(buffer[(2 + x, 0)].bg, Color::Yellow);
        }
        editor.handle(Input::Char('/'));
        for ch in "界界".chars() {
            editor.handle(Input::Char(ch));
        }
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        let buffer = terminal.backend().buffer();
        assert_eq!(buffer[(1, 4)].symbol(), "界");
        assert_eq!(buffer[(3, 4)].symbol(), "界");
        editor.handle(Input::Backspace);
        editor.handle(Input::Backspace);
        editor.handle(Input::Char('\t'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(4, 4)
        );
    }

    #[test]
    fn terminal_can_present_previous_frame_while_next_frame_is_computed() {
        use std::{cell::Cell, rc::Rc};

        struct Output {
            bytes: Vec<u8>,
            synchronized: Rc<Cell<bool>>,
        }
        impl io::Write for Output {
            fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
                self.bytes.extend_from_slice(bytes);
                Ok(bytes.len())
            }
            fn flush(&mut self) -> io::Result<()> {
                for command in self.bytes.split(|byte| *byte == b'\x1b') {
                    if command.starts_with(b"[?2026h") {
                        self.synchronized.set(true);
                    } else if command.starts_with(b"[?2026l") {
                        self.synchronized.set(false);
                    }
                }
                self.bytes.clear();
                Ok(())
            }
        }
        let synchronized = Rc::new(Cell::new(false));
        let mut output = Output {
            bytes: Vec::new(),
            synchronized: Rc::clone(&synchronized),
        };
        let mut terminal = Terminal::with_options(
            CrosstermBackend::new(Vec::new()),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(Rect::new(0, 0, 20, 5)),
            },
        )
        .unwrap();
        for text in ["first frame", "second frame", "third frame"] {
            draw_frame(&mut terminal, &mut output, |frame| {
                assert!(
                    !synchronized.get(),
                    "terminal presentation suspended during frame computation"
                );
                frame.render_widget(Paragraph::new(text), frame.area());
            })
            .unwrap();
            assert!(!synchronized.get());
        }
    }

    #[test]
    fn scrolling_never_paints_with_an_exposed_cursor_even_without_synchronized_updates() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor
            .apply(vec![crate::editor::Effect::Replace(
                (0..40).map(|row| format!("row {row}\n")).collect(),
            )])
            .unwrap();
        let mut output = Vec::new();
        let mut terminal = Terminal::with_options(
            CrosstermBackend::new(Vec::new()),
            ratatui::TerminalOptions {
                viewport: ratatui::Viewport::Fixed(Rect::new(0, 0, 20, 5)),
            },
        )
        .unwrap();
        let mut viewports = BufferViewports::default();
        for key in std::iter::repeat_n('j', 20).chain(std::iter::repeat_n('k', 20)) {
            editor.handle(Input::Char(key));
            draw_frame(&mut terminal, &mut output, |frame| {
                viewports.draw(frame, &mut editor)
            })
            .unwrap();
        }
        drop(terminal);
        let output = std::str::from_utf8(&output).unwrap();
        for supports_sync in [false, true] {
            let (mut visible, mut synchronized) = (true, false);
            let mut screen = [[b' '; 20]; 5];
            let (mut x, mut y) = (0, 0);
            for escape in output.split('\x1b').skip(1) {
                let rest = escape.strip_prefix('[').unwrap();
                let end = rest.find(|ch| ('@'..='~').contains(&ch)).unwrap();
                let (command, text) = rest.split_at(end + 1);
                match command {
                    "?25h" => visible = true,
                    "?25l" => visible = false,
                    "?2026h" => synchronized = supports_sync,
                    "?2026l" => synchronized = false,
                    _ if command.ends_with('H') => {
                        let (row, column) = command[..command.len() - 1].split_once(';').unwrap();
                        y = row.parse::<usize>().unwrap() - 1;
                        x = column.parse::<usize>().unwrap() - 1;
                    }
                    _ => {}
                }
                for byte in text.bytes().filter(|&byte| byte >= b' ' && byte != 127) {
                    assert!(
                        if supports_sync {
                            synchronized
                        } else {
                            !visible
                        },
                        "partial frame exposed during redraw (sync={supports_sync}): {text:?}",
                    );
                    if y < screen.len() && x < screen[y].len() {
                        screen[y][x] = byte;
                    }
                    x += 1;
                }
            }
            assert!(visible);
            assert!(!synchronized);
            for (row, expected) in [(0, "row 0"), (1, "row 1"), (2, "row 2")] {
                let line = std::str::from_utf8(&screen[row]).unwrap().trim_end();
                assert!(line.ends_with(expected), "{line:?}");
            }
            assert_eq!(screen[y][x], b'r', "caret was not restored to the source");
        }
    }

    #[cfg(unix)]
    #[test]
    fn terminal_session_scopes_the_callers_panic_hook() {
        use std::io::Write;
        const CHILD: &str = "VAMP_TERMINAL_HOOK_PROBE";
        if let Ok(mode) = std::env::var(CHILD) {
            std::panic::set_hook(Box::new(|info| {
                assert!(!crossterm::terminal::is_raw_mode_enabled().unwrap());
                println!("CALLER_HOOK");
                eprintln!("{info}");
            }));
            if mode == "entry" {
                let mut editor = EditorSession::open(None, vec![], None).unwrap();
                assert!(run(&mut editor).is_err());
            } else {
                let result = panic::catch_unwind(AssertUnwindSafe(|| {
                    TerminalSession::run(|| {
                        assert!(crossterm::terminal::is_raw_mode_enabled().unwrap());
                        match mode.as_str() {
                            "normal" => Ok(()),
                            "error" => Err(io::Error::from(io::ErrorKind::BrokenPipe)),
                            "panic" => {
                                let mut terminal = Terminal::with_options(
                                    CrosstermBackend::new(Vec::new()),
                                    ratatui::TerminalOptions {
                                        viewport: ratatui::Viewport::Fixed(Rect::new(0, 0, 20, 5)),
                                    },
                                )?;
                                draw_frame(&mut terminal, &mut io::stdout(), |_| {
                                    panic::panic_any(73_u64)
                                })
                            }
                            "keys" => {
                                let mut editor = Editor::open(None, vec![]).unwrap();
                                editor.handle(Input::Ctrl('p'));
                                let original = editor.lines().to_vec();
                                println!("READING_KEYS");
                                io::stdout().flush()?;
                                for (index, expected) in [
                                    Input::Ctrl('j'),
                                    Input::Ctrl('k'),
                                    Input::Ctrl('j'),
                                    Input::Ctrl('k'),
                                    Input::Ctrl('h'),
                                    Input::Ctrl('l'),
                                    Input::Backspace,
                                    Input::Backspace,
                                    Input::Enter,
                                    Input::Enter,
                                ]
                                .into_iter()
                                .enumerate()
                                {
                                    let Event::Key(key) = event::read()? else {
                                        panic!("expected a keyboard event");
                                    };
                                    let input = translate(key).unwrap();
                                    assert_eq!(input, expected);
                                    if index == 4 {
                                        for ch in "ab".chars() {
                                            editor.handle(Input::Char(ch));
                                        }
                                    } else if index == 8 {
                                        for ch in "q!".chars() {
                                            editor.handle(Input::Char(ch));
                                        }
                                    }
                                    editor.handle(input);
                                    match index {
                                        0 | 2 => assert_eq!(editor.palette().unwrap().selected, 1),
                                        1 | 3 => assert_eq!(editor.palette().unwrap().selected, 0),
                                        4 | 5 => assert_eq!(editor.palette().unwrap().query, "ab"),
                                        6 => assert_eq!(editor.palette().unwrap().query, "a"),
                                        7 => assert_eq!(editor.palette().unwrap().query, ""),
                                        8 => {
                                            assert!(editor.palette().is_none());
                                            assert_eq!(editor.mode(), Mode::Command);
                                            assert!(!editor.should_quit());
                                        }
                                        9 => assert!(editor.should_quit()),
                                        _ => unreachable!(),
                                    }
                                    assert_eq!(editor.lines(), original);
                                }
                                Ok(())
                            }
                            _ => unreachable!(),
                        }
                    })
                }));
                match mode.as_str() {
                    "normal" | "keys" => result.unwrap().unwrap(),
                    "error" => assert_eq!(
                        result.unwrap().unwrap_err().kind(),
                        io::ErrorKind::BrokenPipe
                    ),
                    "panic" => assert_eq!(result.unwrap_err().downcast_ref::<u64>(), Some(&73)),
                    _ => unreachable!(),
                }
            }
            assert!(!crossterm::terminal::is_raw_mode_enabled().unwrap());
            println!("AFTER_TERMINAL_RETURN");
            let _ = panic::catch_unwind(|| panic!("outside the terminal session"));
            return;
        }

        use std::os::unix::process::CommandExt;
        use std::process::{Command, Stdio};
        unsafe extern "C" {
            fn setsid() -> i32;
        }
        let mut command = Command::new(std::env::current_exe().unwrap());
        command
            .args([
                "--exact",
                "tui::tests::terminal_session_scopes_the_callers_panic_hook",
                "--nocapture",
                "--color",
                "never",
            ])
            .env(CHILD, "entry")
            .stdin(Stdio::null());
        // SAFETY: setsid is async-signal-safe and detaches the child from any
        // controlling terminal without touching inherited Rust state.
        unsafe {
            command.pre_exec(|| {
                if setsid() == -1 {
                    Err(io::Error::last_os_error())
                } else {
                    Ok(())
                }
            });
        }
        let check = |output: std::process::Output, mode: &str| {
            assert!(output.status.success(), "{mode}: {output:?}");
            let stdout = String::from_utf8(output.stdout).unwrap();
            let (before, after) = stdout.split_once("AFTER_TERMINAL_RETURN").unwrap();
            let entered = usize::from(mode != "entry");
            assert_eq!(
                before.matches("\x1b[?1049h").count(),
                entered,
                "{mode}: {before:?}"
            );
            assert_eq!(
                before.matches("\x1b[?1049l").count(),
                entered,
                "{mode}: {before:?}"
            );
            for protocol in [1000, 1002, 1003, 1015, 1006] {
                assert_eq!(
                    before.matches(&format!("\x1b[?{protocol}h")).count(),
                    entered,
                    "{mode}: mouse capture was not enabled: {before:?}",
                );
                assert_eq!(
                    before.matches(&format!("\x1b[?{protocol}l")).count(),
                    entered,
                    "{mode}: mouse capture was not restored: {before:?}",
                );
            }
            if mode == "panic" {
                let end = before.find("\x1b[?2026l").unwrap();
                assert!(end < before.find("CALLER_HOOK").unwrap());
                assert!(
                    before.find("\x1b[?1049l").unwrap() < before.find("CALLER_HOOK").unwrap(),
                    "{before:?}",
                );
                assert!(
                    before.find("\x1b[?1006l").unwrap() < before.find("CALLER_HOOK").unwrap(),
                    "{before:?}",
                );
            }
            assert!(after.contains("CALLER_HOOK"), "{after:?}");
            assert!(
                !after.contains('\u{1b}'),
                "terminal hook outlived its session: {after:?}"
            );
        };
        check(command.output().unwrap(), "entry");

        // Ruby's standard-library PTY gives each positive-entry scenario a real
        // terminal, keeping process-global hooks isolated from the test runner.
        for mode in ["normal", "error", "panic", "keys"] {
            let output =
                Command::new(std::env::var_os("VAMP_RUBY").unwrap_or_else(|| "ruby".into()))
                    .args([
                        "-rpty",
                        "-rtimeout",
                        "-e",
                        r#"
PTY.spawn(*ARGV) do |output, input, pid|
  sent_keys = false
  captured = +""
  begin
    Timeout.timeout(10) do
      loop do
        chunk = output.readpartial(4096)
        STDOUT.write(chunk)
        captured << chunk
        if !sent_keys && captured.include?("READING_KEYS")
          input.write("\e[106;5u\e[107;5u\n\v\b\f\x7f\x7f\e[13u\r")
          input.flush
          sent_keys = true
        end
      end
    end
  rescue EOFError, Errno::EIO
  rescue Timeout::Error
    Process.kill("TERM", pid)
    Process.wait(pid)
    abort "terminal lifecycle probe timed out"
  ensure
    input.close
  end
  Process.wait(pid)
  exit($?.exitstatus || 1)
end
"#,
                        "--",
                    ])
                    .arg(std::env::current_exe().unwrap())
                    .args([
                        "--exact",
                        "tui::tests::terminal_session_scopes_the_callers_panic_hook",
                        "--nocapture",
                        "--color",
                        "never",
                    ])
                    .env(CHILD, mode)
                    .output()
                    .unwrap();
            check(output, mode);
        }
    }
}