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

#[cfg(unix)]
use crossterm::event::{
    KeyboardEnhancementFlags, PopKeyboardEnhancementFlags, PushKeyboardEnhancementFlags,
};
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 tree_sitter::Point;
use unicode_segmentation::UnicodeSegmentation;
use unicode_width::UnicodeWidthStr;

use crate::{
    chrome::{ChromeLine, PopupAnchor, SegmentConfig},
    diff::{
        ChangedFile, ColumnEmpty, ColumnRow, ColumnView, DiffState, DisplayRow, FileStatus, Focus,
        HistoryComparison, PaneLayout, Phase, ViewMode,
    },
    editor::{
        Completion, Cursor, Editor, Hover, Input, Mode, Palette, ResolverLayout, ResolverStatus,
        ResolverView, ResolverWorkspace, Selection, StartupDiagnostic, WhitespaceScope,
    },
    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,
}

/// Owns terminal modes and panic cleanup through application startup and shutdown.
pub 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();
    #[cfg(unix)]
    let _ = execute!(io::stdout(), PopKeyboardEnhancementFlags);
    let _ = execute!(
        io::stdout(),
        EndSynchronizedUpdate,
        DisableBracketedPaste,
        DisableMouseCapture,
        DisableFocusChange,
        ColorSchemeNotifications(false),
        LeaveAlternateScreen,
        Show
    );
}

impl TerminalSession {
    pub fn run(inherited_screen: bool, body: impl FnOnce() -> io::Result<()>) -> io::Result<()> {
        let hook = Arc::new(Mutex::new(HookState {
            previous: Some(panic::take_hook()),
            active: inherited_screen,
        }));
        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;
            if !inherited_screen {
                execute!(io::stdout(), EnterAlternateScreen)?;
                // Restart inherits this screen and its keyboard stack entry.
                #[cfg(unix)]
                execute!(
                    io::stdout(),
                    PushKeyboardEnhancementFlags(
                        KeyboardEnhancementFlags::DISAMBIGUATE_ESCAPE_CODES
                    )
                )?;
            }
            execute!(
                io::stdout(),
                EnableBracketedPaste,
                EnableMouseCapture,
                EnableFocusChange,
                ColorSchemeNotifications(true)
            )?;
            body()
        }));
        drop(session);
        match result {
            Ok(result) => result,
            Err(payload) => panic::resume_unwind(payload),
        }
    }

    /// Restores process-local raw/input state without exposing the normal screen.
    /// The guard remains armed if launching the replacement process fails.
    pub fn prepare_restart() -> io::Result<()> {
        disable_raw_mode()?;
        execute!(
            io::stdout(),
            EndSynchronizedUpdate,
            DisableBracketedPaste,
            DisableMouseCapture,
            DisableFocusChange,
            ColorSchemeNotifications(false)
        )
    }
}

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
}

fn scroll_margin(size: usize, distance: Option<usize>) -> usize {
    distance.unwrap_or(size / 2).min(size / 2)
}

fn scroll_offset(top: usize, cursor: usize, size: usize, distance: Option<usize>) -> usize {
    if size == 0 {
        return top;
    }
    let margin = scroll_margin(size, distance);
    if margin == size / 2 {
        return cursor.saturating_sub(margin);
    }
    if cursor < top.saturating_add(margin) {
        cursor.saturating_sub(margin)
    } else if cursor >= top.saturating_add(size - margin) {
        cursor.saturating_sub(size - margin - 1)
    } else {
        top
    }
}

#[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,
    history: BTreeMap<HistoryKey, HistoryDiff>,
    history_key: Option<HistoryKey>,
}

#[derive(Default)]
struct PaneViewport {
    offsets: BTreeMap<usize, (usize, usize)>,
    document: DocumentViewport,
    document_buffer: Option<usize>,
    documents: BTreeMap<usize, DocumentViewport>,
    panels: WheelPanels,
}
type HistoryKey = (usize, [usize; 2], Option<usize>);

fn history_key(resolver: &ResolverWorkspace) -> Option<HistoryKey> {
    Some((
        resolver.files.get(resolver.current_file)?.draft_buffer,
        resolver.history_sources,
        resolver.selected_base,
    ))
}

struct HistoryDiff {
    comparison: HistoryComparison,
    top: DiffWrapPosition,
    left: [usize; 3],
    widths: [usize; 3],
    wrapping: [bool; 3],
    wrap: [WrapCache; 3],
    visible: [Vec<WrappedDiffRow>; 3],
    caret: Option<(usize, Cursor, u64, bool)>,
}

impl HistoryDiff {
    fn new(resolver: &ResolverWorkspace) -> Self {
        let file = &resolver.files[resolver.current_file];
        let text = |index: Option<usize>| {
            index
                .and_then(|index| file.sources.get(index))
                .map_or("", |source| source.text.as_str())
        };
        let comparison = HistoryComparison::new([
            text(Some(resolver.history_sources[0])),
            text(resolver.selected_base),
            text(Some(resolver.history_sources[1])),
        ]);
        Self {
            comparison,
            top: DiffWrapPosition::default(),
            left: [0; 3],
            widths: [0; 3],
            wrapping: [false; 3],
            wrap: std::array::from_fn(|_| WrapCache::default()),
            visible: std::array::from_fn(|_| Vec::new()),
            caret: None,
        }
    }

    fn row_height(&mut self, row: usize) -> usize {
        let mut height = 1;
        for column in 0..3 {
            if self.wrapping[column]
                && self.widths[column] > 0
                && let Some(source) = self.comparison.column(column).source_row(row)
            {
                let lines = self.comparison.column(column).lines;
                height = height.max(
                    self.wrap[column]
                        .segments(source, lines.get(source).map_or("", String::as_str))
                        .len(),
                );
            }
        }
        height
    }

    fn step(&mut self, down: bool) {
        if down {
            if self.top.continuation + 1 < self.row_height(self.top.display) {
                self.top.continuation += 1;
            } else if self.top.display + 1 < self.comparison.row_count() {
                self.top.display += 1;
                self.top.continuation = 0;
            }
        } else if self.top.continuation > 0 {
            self.top.continuation -= 1;
        } else if self.top.display > 0 {
            self.top.display -= 1;
            self.top.continuation = self.row_height(self.top.display) - 1;
        }
    }

    fn fill(&mut self, height: usize) {
        for rows in &mut self.visible {
            rows.clear();
        }
        let top = self.top;
        for _ in 0..height {
            for column in 0..3 {
                let mut segments = [None; 2];
                let mut final_segments = [false; 2];
                let projection = self.comparison.column(column);
                let side = usize::from(projection.focus == Focus::After);
                if let Some(source) = projection.source_row(self.top.display) {
                    let text = projection.lines.get(source).map_or("", String::as_str);
                    if self.wrapping[column] {
                        let parts = self.wrap[column].segments(source, text);
                        segments[side] = parts.get(self.top.continuation).copied();
                        final_segments[side] = self.top.continuation + 1 == parts.len();
                    } else if self.top.continuation == 0 {
                        segments[side] = Some(Segment {
                            start: self.left[column],
                            end: self.left[column].saturating_add(self.widths[column]),
                        });
                        final_segments[side] = true;
                    }
                }
                self.visible[column].push(WrappedDiffRow {
                    position: self.top,
                    segments,
                    final_segments,
                    scope: [false; 2],
                    unwrapped: false,
                });
            }
            let previous = self.top;
            self.step(true);
            if self.top == previous {
                break;
            }
        }
        self.top = top;
    }
}

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();
        let viewport_pane = editor
            .resolver()
            .filter(|resolver| resolver.view == ResolverView::Resolution)
            .map_or(focused, |resolver| resolver.draft_pane);
        self.activate(viewport_pane, editor);
        self.parked
            .retain(|id, _| editor.pane_buffer_id(*id).is_some());
        self.syntax.retain(|id, _| editor.has_buffer(*id));
        let syntax = self.syntax.entry(editor.buffer_id()).or_default();
        let full_workspace = draw_bars(frame, editor, frame.area(), syntax);
        let resolver_resolution = editor
            .resolver()
            .is_some_and(|resolver| resolver.view == ResolverView::Resolution);
        let resolver_history = editor
            .resolver()
            .is_some_and(|resolver| resolver.view == ResolverView::History);
        let multiple = !resolver_resolution && editor.pane_layout().len() > 1;
        let layout_pane = editor
            .review_panel()
            .and_then(|pane| editor.pane_origin(pane))
            .unwrap_or(focused);
        let (workspace, dock) =
            editor.with_render_pane(layout_pane, |view| match view.file_picker() {
                Some(picker) if picker.presentation == FilePresentation::Docked => dock_layout(
                    full_workspace,
                    if view.picker_diff().is_some() {
                        DockSide::Right
                    } else {
                        view.file_explorer_side()
                    },
                    picker.focused,
                ),
                _ => (full_workspace, None),
            });
        editor.set_pane_bounds(pane_rect(workspace));
        self.rects.clear();
        if resolver_history {
            let layout = resolver_history_layout(
                workspace,
                editor.resolver().unwrap(),
                focused,
                editor.resolve_history_layout,
            );
            draw_resolver_heading(frame, editor.resolver().unwrap(), layout.heading);
            self.draw_resolver_history(frame, editor, &layout);
        } else if resolver_resolution {
            self.rects.push((viewport_pane, workspace));
        } else {
            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].into_iter().filter(|_| !resolver_history) {
            for index in 0..self.rects.len() {
                let (id, mut leaf) = self.rects[index];
                if ((id == focused) || resolver_resolution) != 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 render_pane = if resolver_resolution { focused } else { id };
                editor.with_render_pane(render_pane, |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,
                        full_workspace,
                        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(viewport_pane, editor);
        self.panels.workspace_managed = false;
        if self.rects.is_empty() {
            self.panels.begin_frame();
            self.document.geometry = None;
        }
        if let Some(panel) = dock {
            self.activate(layout_pane, editor);
            editor.with_render_pane(layout_pane, |view| {
                if let Some(picker) = view.file_picker() {
                    self.panels.picker_scroll.distance = view.scroll_distance();
                    draw_file_list(
                        frame,
                        picker,
                        panel,
                        view.file_navigation_hint(),
                        &mut self.panels,
                        view.picker_diff().and_then(|diff| {
                            diff.comparison.as_ref().map(|comparison| {
                                (comparison.files.as_slice(), &diff.reviewed_files)
                            })
                        }),
                    );
                }
            });
            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 resolver_history {
            editor.set_resolver_history_bounds(
                self.rects.iter().map(|(id, area)| (*id, pane_rect(*area))),
                dock.map(pane_rect),
            );
            if let Some(diff) = editor.picker_diff() {
                self.panels.diff = Some(DiffGeometry {
                    regions: [
                        (dock.unwrap_or_default(), Focus::Files),
                        (Rect::default(), Focus::Before),
                        (Rect::default(), Focus::After),
                    ],
                    viewport: None,
                    text_widths: [0; 2],
                    wrapping: diff.word_wrap,
                    view_mode: diff.view_mode,
                    split_axis: diff.split_axis,
                    caret_row: None,
                });
            }
        }
        if resolver_resolution {
            self.rects.clear();
            if let Some(geometry) = &self.panels.diff {
                let resolver = editor.resolver().unwrap();
                for (pane, region) in [
                    (Some(resolver.draft_pane), geometry.regions[1].0),
                    (resolver.alternative_pane, geometry.regions[2].0),
                ] {
                    if let Some(pane) = pane.filter(|_| !region.is_empty()) {
                        self.rects.push((pane, region));
                    }
                }
            }
        }
        if let Some(panel) = editor.review_panel() {
            let source = editor.pane_origin(panel);
            let area = self
                .rects
                .iter()
                .find(|(id, _)| Some(*id) == source)
                .map_or(full_workspace, |(_, area)| *area);
            let area = floating_panel(area);
            self.rects.insert(0, (panel, area));
            self.activate(panel, editor);
            self.panels.workspace_managed = true;
            editor.with_render_pane(panel, |view| {
                frame.render_widget(Clear, area);
                let block = Block::default()
                    .borders(Borders::ALL)
                    .border_style(Style::default().fg(Color::Cyan))
                    .title(display_text(
                        view.review_panel_title().unwrap_or("Local review"),
                    ));
                let content = block.inner(area);
                frame.render_widget(block, area);
                self.activate_document(view.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,
                    content,
                    full_workspace,
                    top,
                    left,
                    syntax,
                    &mut self.document,
                    &mut self.panels,
                );
            });
            self.panels.workspace_managed = false;
        }
        if let Some(diff) = editor.diff().filter(|diff| diff.phase != Phase::View) {
            draw_diff(
                frame,
                diff,
                full_workspace,
                editor.selection_navigation_hint(),
                editor.file_navigation_hint(),
                &mut self.panels,
                Some(editor),
            );
        } else {
            draw_overlays(
                frame,
                editor,
                full_workspace,
                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_resolver_history(
        &mut self,
        frame: &mut Frame,
        editor: &mut Editor,
        layout: &ResolverHistoryLayout,
    ) {
        self.panels.begin_frame();
        self.document.geometry = None;
        let resolver = editor.resolver().unwrap();
        let Some(key) = history_key(resolver) else {
            return;
        };
        self.history_key = Some(key);
        self.history
            .retain(|(buffer, _, _), _| editor.has_buffer(*buffer));
        let history = self
            .history
            .entry(key)
            .or_insert_with(|| HistoryDiff::new(resolver));
        let mut panes = [None; 3];
        for (slot, &(index, panel)) in layout.history.iter().enumerate() {
            let column = if resolver.selected_base == Some(index) {
                1
            } else if resolver.history_sources[0] == index {
                0
            } else {
                2
            };
            let pane = resolver.history_panes[index];
            let source = &resolver.files[resolver.current_file].sources[index];
            let content = resolver_document_panel(
                frame,
                panel,
                &format!("{} · readonly", source.label),
                !editor.file_picker().is_some_and(|picker| picker.focused)
                    && pane == editor.pane_id(),
            );
            panes[slot] = Some((column, pane, content));
            self.rects.push((pane, content));
        }
        let previous_widths = history.widths;
        history.widths = [0; 3];
        for &(column, pane, content) in panes.iter().flatten() {
            editor.with_render_pane(pane, |view| {
                let projection = history.comparison.column(column);
                let width = usize::from(content.width);
                history.widths[column] = width.saturating_sub(diff_gutter(
                    projection.diff,
                    projection.file,
                    width,
                    projection.focus,
                ));
                history.wrapping[column] = view.word_wrap();
                history.wrap[column].prepare((view.buffer_id(), 0), history.widths[column]);
            });
        }
        let height = panes
            .iter()
            .flatten()
            .map(|(_, _, area)| usize::from(area.height))
            .min()
            .unwrap_or(0);
        history.top.continuation = history
            .top
            .continuation
            .min(history.row_height(history.top.display) - 1);
        history.fill(height);
        if let Some(&(column, pane, content)) = panes
            .iter()
            .flatten()
            .find(|(_, pane, _)| *pane == editor.pane_id())
        {
            let cursor = editor.cursor();
            let identity = (
                pane,
                cursor,
                editor.caret_reveal_revision(),
                history.wrapping[column],
            );
            if !editor.file_picker().is_some_and(|picker| picker.focused)
                && (history.caret != Some(identity) || previous_widths != history.widths)
                && let Some(display) = history
                    .comparison
                    .column(column)
                    .view()
                    .display_row(cursor.row)
            {
                let column_offset = display_column(&editor.lines()[cursor.row], cursor.column);
                let continuation = if history.wrapping[column] {
                    caret_segment(
                        history.wrap[column].segments(cursor.row, &editor.lines()[cursor.row]),
                        column_offset,
                    )
                } else {
                    history.left[column] = scroll_offset(
                        history.left[column],
                        column_offset,
                        history.widths[column],
                        editor.scroll_distance(),
                    );
                    0
                };
                let caret = DiffWrapPosition {
                    display,
                    continuation,
                };
                let screen = history.visible[column]
                    .iter()
                    .position(|row| row.position == caret);
                let height = usize::from(content.height);
                let margin = scroll_margin(height, editor.scroll_distance());
                let anchor = if height == 0 {
                    None
                } else if caret < history.top || screen.is_some_and(|row| row < margin) {
                    Some(margin)
                } else if screen.is_none_or(|row| row >= height.saturating_sub(margin)) {
                    Some(height.saturating_sub(margin + 1))
                } else {
                    None
                };
                if let Some(anchor) = anchor {
                    history.top = caret;
                    for _ in 0..anchor {
                        history.step(false);
                    }
                }
                history.fill(height);
            }
            history.caret = Some(identity);
        }
        let scroll = editor.take_viewport_scroll(height);
        for _ in 0..scroll.unsigned_abs() {
            let previous = history.top;
            history.step(scroll > 0);
            if history.top == previous {
                break;
            }
        }
        if scroll != 0 {
            history.fill(height);
        }
        for (column, pane, content) in panes.into_iter().flatten() {
            editor.with_render_pane(pane, |view| {
                let projection = history.comparison.column(column);
                let syntax = self.syntax.entry(view.buffer_id()).or_default();
                let source_rows = history.visible[column]
                    .iter()
                    .filter_map(|row| projection.source_row(row.position.display));
                let first = source_rows
                    .clone()
                    .min()
                    .unwrap_or(0)
                    .min(view.lines().len() - 1);
                let last = source_rows
                    .max()
                    .unwrap_or(first)
                    .min(view.lines().len() - 1);
                syntax.update_visible(
                    view.lines(),
                    view.path(),
                    view.text_revision(),
                    std::slice::from_ref(&(first..last + 1)),
                );
                let text_area = draw_diff_pane(
                    frame,
                    projection.diff,
                    projection.file,
                    content,
                    projection.focus == Focus::Before,
                    [&*syntax, &*syntax],
                    [view.semantic_tokens(), view.semantic_tokens()],
                    (history.top.display, &mut history.left[column], None),
                    Some(&history.visible[column]),
                    self.panels.diff_colors,
                    view.highlight_trailing_whitespace(),
                    Some(view.whitespace_characters()),
                    view.whitespace_scope(),
                    view.resolver(),
                    true,
                );
                if view.render_pane_focused()
                    && !view.file_picker().is_some_and(|picker| picker.focused)
                {
                    self.panels.caret = paint_diff_editor(
                        frame,
                        view,
                        projection.view(),
                        text_area,
                        (history.top.display, history.left[column]),
                        Some(&history.visible[column]),
                    )
                    .map(|caret| (text_area, caret));
                }
            });
        }
    }

    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);
        }
        if session.editor().resolver().is_some() {
            return;
        }
        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 target = self.rects.iter().find_map(|(id, area)| {
            area.contains(Position::new(mouse.column, mouse.row))
                .then_some(*id)
        });
        let target = if let Some(panel) = session.editor().review_panel() {
            if target != Some(panel) {
                return true;
            }
            panel
        } else if let Some(target) = target {
            target
        } else {
            return false;
        };
        if let Some(resolver) = session
            .editor()
            .resolver()
            .filter(|resolver| resolver.view == ResolverView::History)
            && let Some(key) = self.history_key
            && let Some(history) = self.history.get_mut(&key)
        {
            let source = resolver
                .history_panes
                .iter()
                .position(|pane| *pane == target)
                .unwrap();
            let column = if resolver.selected_base == Some(source) {
                1
            } else if resolver.history_sources[0] == source {
                0
            } else {
                2
            };
            match wheel_kind(&mouse).unwrap() {
                MouseEventKind::ScrollDown | MouseEventKind::ScrollUp => {
                    let down = wheel_kind(&mouse) == Some(MouseEventKind::ScrollDown);
                    for _ in 0..3 {
                        history.step(down);
                    }
                }
                MouseEventKind::ScrollLeft | MouseEventKind::ScrollRight
                    if !history.wrapping[column] =>
                {
                    let right = wheel_kind(&mouse) == Some(MouseEventKind::ScrollRight);
                    let left = if right {
                        history.left[column].saturating_add(3)
                    } else {
                        history.left[column].saturating_sub(3)
                    };
                    let projection = history.comparison.column(column);
                    history.left[column] = projection.diff.bound_horizontal(
                        projection.focus,
                        left,
                        history.widths[column],
                    );
                }
                _ => {}
            }
            return true;
        }
        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()
            || editor.command_output().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,
    clear_screen: bool,
    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(|()| {
        if clear_screen {
            // Fresh Ratatui buffers are already empty; avoid its blocking cursor query.
            crossterm::queue!(
                terminal.backend_mut(),
                crossterm::terminal::Clear(crossterm::terminal::ClearType::All)
            )?;
        }
        terminal.draw(render).map(|_| ())
    });
    let finish = execute!(terminal.backend_mut(), EndSynchronizedUpdate);
    result.and(finish)?;
    output.write_all(terminal.backend().writer())?;
    output.flush()
}

/// Renders inside an active `TerminalSession`; inherited contents are cleared
/// inside the first synchronized frame rather than exposing a blank screen.
pub fn run(session: &mut EditorSession, mut clear_screen: bool) -> io::Result<()> {
    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, clear_screen, |frame| {
                viewports.draw_session(frame, session)
            })?;
            redraw = false;
            clear_screen = 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 let Some(input) = translate(key) {
                    viewports.panels.follow_files();
                    if batch_key(session.editor(), &key, &input) {
                        pending = keys_ready(session, input, || {
                            next_terminal_event(&mut colors, Duration::ZERO)
                        })?;
                    } else {
                        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 => {
                redraw |= session.refresh_blame();
                redraw |= session.refresh_gutter();
                query_theme = true;
            }
            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,
        )
}
fn batch_key(editor: &Editor, key: &KeyEvent, input: &Input) -> bool {
    if editor.mode() == Mode::Insert {
        typing_key(key)
    } else {
        key.kind != KeyEventKind::Release && editor.can_batch_navigation(input)
    }
}

// Coalesce frames, not actions: bindings, selections and history still see each key.
fn keys_ready(
    session: &mut EditorSession,
    mut input: Input,
    mut next: impl FnMut() -> io::Result<Option<Event>>,
) -> io::Result<Option<Event>> {
    let mode = session.editor().mode();
    // Render before reversing/clamping a scroll or revealing a moved caret.
    let scroll = session.editor().viewport_scroll_action(&input);
    for handled in 1..=64 {
        session.handle(input);
        if handled == 64 || session.editor().mode() != mode || session.editor().should_quit() {
            return Ok(None);
        }
        let pending = next()?;
        if let Some(Event::Key(key)) = &pending
            && let Some(next) = translate(*key)
            && batch_key(session.editor(), key, &next)
            && session.editor().viewport_scroll_action(&next) == scroll
        {
            input = next;
        } else {
            return Ok(pending);
        }
    }
    unreachable!()
}

fn translate(key: KeyEvent) -> Option<Input> {
    #[cfg(target_os = "macos")]
    if key.code == KeyCode::Backspace {
        match key.modifiers {
            KeyModifiers::ALT => return Some(Input::AltBackspace),
            KeyModifiers::SUPER => return Some(Input::SuperBackspace),
            _ => {}
        }
    }
    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 if key.modifiers.contains(KeyModifiers::CONTROL) => Input::Ctrl('i'),
        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 {
    visible_text(line, left, width, false)
}

fn visible_text(line: &str, left: usize, width: usize, sanitize_controls: bool) -> String {
    let mut visible = String::new();
    let mut column = 0;
    let right = left.saturating_add(width);
    for grapheme in line.graphemes(true) {
        let control = sanitize_controls && grapheme.chars().any(|ch| ch.is_control() && ch != '\t');
        let cells = if control {
            grapheme.chars().count()
        } else 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 if control {
                for _ in 0..cells {
                    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)
}

struct ChromeItem<'a> {
    text: Cow<'a, str>,
    config: &'a SegmentConfig,
    tab: Option<usize>,
    accent: bool,
    bold: bool,
    first: bool,
    mandatory: bool,
    width: usize,
    compact: bool,
}

impl ChromeItem<'_> {
    fn leading_edge(&self) -> &str {
        if self.first {
            self.config
                .first_leading_edge
                .as_deref()
                .unwrap_or(&self.config.leading_edge)
        } else {
            &self.config.leading_edge
        }
    }
}

fn display_path(path: &std::path::Path) -> Cow<'_, str> {
    static HOME: LazyLock<Option<std::path::PathBuf>> = LazyLock::new(|| {
        std::env::var_os("HOME")
            .filter(|home| !home.is_empty())
            .or_else(|| std::env::var_os("USERPROFILE"))
            .map(std::path::PathBuf::from)
            .filter(|home| {
                home.is_absolute()
                    && home
                        .to_str()
                        .is_some_and(|home| !home.chars().any(char::is_control))
            })
    });
    abbreviate_home(path, HOME.as_deref())
}

fn abbreviate_home<'a>(path: &'a std::path::Path, home: Option<&std::path::Path>) -> Cow<'a, str> {
    if let Some(suffix) = home.and_then(|home| path.strip_prefix(home).ok()) {
        return if suffix.as_os_str().is_empty() {
            Cow::Borrowed("~")
        } else {
            Cow::Owned(format!("~/{}", suffix.display()))
        };
    }
    path.to_string_lossy()
}

fn chrome_title(
    template: &str,
    index: usize,
    path: Option<&std::path::Path>,
    dirty: bool,
    diff: Option<&DiffState>,
) -> String {
    let name = path
        .map(|path| {
            path.file_name()
                .unwrap_or(path.as_os_str())
                .to_string_lossy()
        })
        .unwrap_or(Cow::Borrowed("[No Name]"));
    let path = path.map(display_path).unwrap_or(Cow::Borrowed("[No Name]"));
    let mut title = String::with_capacity(template.len() + name.len());
    let mut rest = template;
    while let Some((literal, placeholder)) = rest.split_once('{') {
        title.push_str(literal);
        let Some((field, after)) = placeholder.split_once('}') else {
            break;
        };
        match field {
            "index" => write!(title, "{index}").unwrap(),
            "view" if diff.is_some() => {
                title.push_str("Diff · ");
                if let Some(diff) = diff
                    && diff.phase == Phase::View
                    && let Some(file) = diff
                        .comparison
                        .as_ref()
                        .and_then(|comparison| comparison.files.get(diff.file))
                    && file.loaded
                {
                    let (added, removed) =
                        file.hunks.iter().fold((0, 0), |(added, removed), hunk| {
                            (added + hunk.after_len, removed + hunk.before_len)
                        });
                    write!(title, "+{added} -{removed} · ").unwrap();
                }
            }
            "name" => title.push_str(&name),
            "path" => title.push_str(&path),
            "modified" if dirty => title.push_str(" [+]"),
            _ => {}
        }
        rest = after;
    }
    title.push_str(rest);
    if title.chars().any(char::is_control) {
        display_text(&title)
    } else {
        title
    }
}

fn chrome_items<'a>(
    editor: &'a Editor,
    line: &'a ChromeLine,
    names: &[String],
    syntax: &SyntaxCache,
) -> Vec<ChromeItem<'a>> {
    let mut items = Vec::new();
    for name in names {
        let config = line.segment(name);
        if name == "tabs" {
            for index in 0..editor.tab_count() {
                let buffer = editor.tab_buffer(index);
                let active = index == editor.tab_index();
                items.push(ChromeItem {
                    text: Cow::Owned(chrome_title(
                        &config.title,
                        index + 1,
                        buffer.as_ref().and_then(|buffer| buffer.path),
                        buffer.is_some_and(|buffer| buffer.dirty),
                        editor.tab_diff_at(index),
                    )),
                    config,
                    tab: Some(index),
                    accent: active,
                    bold: active,
                    first: index == 0,
                    mandatory: active,
                    width: 0,
                    compact: false,
                });
            }
            continue;
        }
        let mut text = match name.as_str() {
            "mode" => Cow::Owned(
                if editor.mode() == Mode::Visual && editor.visual_linewise() {
                    "VISUAL LINE".into()
                } else {
                    editor.mode().to_string()
                },
            ),
            "path" => Cow::Owned(chrome_title(
                "{path}{modified}",
                editor.tab_index() + 1,
                editor.path(),
                editor.dirty(),
                editor.tab_diff_at(editor.tab_index()),
            )),
            "position" => Cow::Owned(format!(
                "{}:{}",
                editor.cursor().row + 1,
                editor.cursor().column + 1
            )),
            "language" => Cow::Owned(if let Some(error) = syntax.error() {
                format!("syntax: {error}")
            } else {
                syntax.language().unwrap_or_default().to_owned()
            }),
            "lsp" => Cow::Borrowed(editor.lsp_label()),
            "diagnostics" => {
                let mut counts = [0; 4];
                for diagnostic in editor.diagnostics() {
                    counts[diagnostic_severity(diagnostic.severity).0] += 1;
                }
                let mut text = String::new();
                for (label, count) in ["E", "W", "I", "H"].into_iter().zip(counts) {
                    if count > 0 {
                        if !text.is_empty() {
                            text.push_str("  ");
                        }
                        write!(text, "{label}:{count}").unwrap();
                    }
                }
                Cow::Owned(text)
            }
            "selections" => Cow::Owned(if editor.selection_count() > 1 {
                format!("{} selections", editor.selection_count())
            } else {
                String::new()
            }),
            "count" => Cow::Owned(
                editor
                    .count()
                    .map(|count| format!("count: {count}"))
                    .unwrap_or_default(),
            ),
            "pending" => {
                let mut text = editor.sequence_pending().unwrap_or_default().to_owned();
                for pending in [
                    editor.g_pending().then_some('g'),
                    editor.line_operator_pending(),
                    editor.seek_pending(),
                ]
                .into_iter()
                .flatten()
                {
                    if !text.is_empty() {
                        text.push_str("  ");
                    }
                    text.push(pending);
                }
                Cow::Owned(text)
            }
            "buffer" => Cow::Owned(if editor.buffer_count() > 1 {
                format!("[buffer {}/{}]", editor.buffer_id(), editor.buffer_count())
            } else {
                String::new()
            }),
            "battery" if editor.label(name).is_empty() => Cow::Borrowed(editor.battery_label()),
            "shell" if editor.label(name).is_empty() => Cow::Borrowed(editor.shell_label()),
            _ => Cow::Borrowed(editor.label(name)),
        };
        // Empty values remain hidden even when a title or decoration is configured.
        if text.is_empty() {
            continue;
        }
        if !config.title.is_empty() {
            text = Cow::Owned(chrome_title(
                &config.title,
                editor.tab_index() + 1,
                editor.path(),
                editor.dirty(),
                editor.tab_diff_at(editor.tab_index()),
            ));
        } else if text.chars().any(char::is_control) {
            text = Cow::Owned(display_text(&text));
        }
        items.push(ChromeItem {
            text,
            config,
            tab: None,
            accent: !matches!(
                name.as_str(),
                "path" | "language" | "diagnostics" | "selections" | "count" | "pending" | "buffer"
            ),
            bold: false,
            first: true,
            mandatory: false,
            width: 0,
            compact: false,
        });
    }
    for item in &mut items {
        item.width = item.text.width()
            + item.config.padding * 2
            + item.config.margin[0]
            + item.config.margin[1]
            + if item.tab.is_none() || item.accent {
                item.leading_edge().width() + item.config.trailing_edge.width()
            } else {
                0
            };
    }
    items.retain(|item| item.width > 0);
    items
}

fn chrome_group_width(items: &[ChromeItem<'_>]) -> usize {
    items.iter().map(|item| item.width).sum::<usize>() + items.len().saturating_sub(1)
}

fn chrome_fits([left, center, right]: [usize; 3], width: usize) -> bool {
    if left > width || center > width || right > width {
        return false;
    }
    let center_start = (width - center) / 2;
    let right_start = width - right;
    if center > 0 {
        (left == 0 || left < center_start) && (right == 0 || center_start + center < right_start)
    } else {
        left == 0 || right == 0 || left < right_start
    }
}

fn draw_chrome(frame: &mut Frame, mut groups: [Vec<ChromeItem<'_>>; 3], area: Rect) {
    if area.width == 0 || area.height == 0 {
        return;
    }
    let mut active_seen = false;
    for item in groups.iter_mut().flatten().filter(|item| item.mandatory) {
        item.mandatory = !active_seen;
        active_seen = true;
    }
    if !groups.iter().flatten().any(|item| item.mandatory)
        && let Some(item) = groups.iter_mut().flatten().next()
    {
        item.mandatory = true;
    }
    let active = groups
        .iter()
        .flatten()
        .find(|item| item.mandatory)
        .and_then(|item| item.tab);
    let mut widths = groups.each_ref().map(|group| chrome_group_width(group));
    let width = usize::from(area.width);
    while !chrome_fits(widths, width) {
        // Inactive tabs yield before configured values, farthest from the active tab first.
        let inactive = groups
            .iter()
            .enumerate()
            .flat_map(|(group, items)| {
                items.iter().enumerate().filter_map(move |(index, item)| {
                    item.tab
                        .filter(|_| !item.mandatory)
                        .map(|tab| (tab.abs_diff(active.unwrap_or(tab)), group, index))
                })
            })
            .max();
        let removable = inactive
            .map(|(_, group, index)| (group, index))
            .or_else(|| {
                [1, 2, 0].into_iter().find_map(|group| {
                    groups[group]
                        .iter()
                        .rposition(|item| !item.mandatory)
                        .map(|index| (group, index))
                })
            });
        let Some((group, index)) = removable else {
            for (group, items) in groups.iter_mut().enumerate() {
                for item in items {
                    let content_width = item.text.width().min(width);
                    widths[group] = widths[group] - item.width + content_width;
                    item.width = content_width;
                    item.compact = true;
                }
            }
            break;
        };
        groups[group].remove(index);
        widths[group] = chrome_group_width(&groups[group]);
    }
    let widths = widths.map(|cells| cells.min(width));
    let starts = [0, (width - widths[1]) / 2, width - widths[2]];
    for (items, start) in groups.iter().zip(starts) {
        let mut x = start;
        for (index, item) in items.iter().enumerate() {
            x += usize::from(index > 0);
            if x >= width {
                break;
            }
            let available = width - x;
            let highlight = Style::default().fg(Color::Black).bg(Color::Cyan);
            let highlight = if item.bold {
                highlight.add_modifier(Modifier::BOLD)
            } else {
                highlight
            };
            let style = if item.accent {
                highlight
            } else if item.tab.is_some() {
                Style::default().fg(Color::Gray)
            } else {
                Style::default()
            };
            let item_width = item.width;
            let line = if item.compact || item_width > available {
                // Content wins over margins, padding, and fades on tiny terminals.
                Line::from(Span::styled(visible_line(&item.text, 0, available), style))
            } else {
                const PADDING: &str =
                    "                                                                ";
                let padding = &PADDING[..item.config.padding];
                let leading_margin = &PADDING[..item.config.margin[0]];
                let trailing_margin = &PADDING[..item.config.margin[1]];
                let edges = item.tab.is_none() || item.accent;
                let edge = Style::default().fg(Color::Cyan);
                Line::from(vec![
                    Span::styled(leading_margin, Style::reset()),
                    Span::styled(if edges { item.leading_edge() } else { "" }, edge),
                    Span::styled(padding, style),
                    Span::styled(item.text.as_ref(), style),
                    Span::styled(padding, style),
                    Span::styled(
                        if edges {
                            &item.config.trailing_edge
                        } else {
                            ""
                        },
                        edge,
                    ),
                    Span::styled(trailing_margin, Style::reset()),
                ])
            };
            let cells = item_width.min(available);
            frame.render_widget(
                Paragraph::new(line),
                Rect::new(area.x.saturating_add(x as u16), area.y, cells as u16, 1),
            );
            x += cells;
        }
    }
}

fn chrome_groups<'a>(
    editor: &'a Editor,
    line: &'a ChromeLine,
    syntax: &SyntaxCache,
) -> [Vec<ChromeItem<'a>>; 3] {
    [&line.left, &line.center, &line.right].map(|names| chrome_items(editor, line, names, syntax))
}

fn chrome_visible(editor: &Editor, groups: &[Vec<ChromeItem<'_>>; 3]) -> bool {
    groups.iter().flatten().any(|item| item.tab.is_none())
        || (editor.tab_count() > 1 && groups.iter().any(|group| !group.is_empty()))
}

fn document_layout(area: Rect, visible: [bool; 2]) -> [Rect; 3] {
    // Bars yield to the last document row, identically at either edge.
    let available = area.height.saturating_sub(1);
    let top = u16::from(visible[0]).min(available);
    let bottom = u16::from(visible[1]).min(available - top);
    let workspace = Rect::new(
        area.x,
        area.y.saturating_add(top),
        area.width,
        area.height - top - bottom,
    );
    [
        Rect::new(area.x, area.y, area.width, top),
        workspace,
        Rect::new(area.x, workspace.bottom(), area.width, bottom),
    ]
}

fn draw_bars(frame: &mut Frame, editor: &Editor, area: Rect, syntax: &mut SyntaxCache) -> Rect {
    if area.width == 0 || area.height == 0 {
        return area;
    }
    // Resolve the active buffer's language before computing either bar's visibility.
    syntax.update_visible(editor.lines(), editor.path(), editor.text_revision(), &[]);
    let groups = [
        chrome_groups(editor, editor.top_bar_config(), syntax),
        chrome_groups(editor, editor.bottom_bar_config(), syntax),
    ];
    let visible = groups
        .each_ref()
        .map(|groups| chrome_visible(editor, groups));
    let [top, workspace, bottom] = document_layout(area, visible);
    for (groups, area) in groups.into_iter().zip([top, bottom]) {
        draw_chrome(frame, groups, area);
    }
    workspace
}

struct ResolverHistoryLayout {
    heading: Rect,
    history: Vec<(usize, Rect)>,
}

fn resolver_history_layout(
    area: Rect,
    resolver: &ResolverWorkspace,
    focused: usize,
    mode: ResolverLayout,
) -> ResolverHistoryLayout {
    let [heading, documents] = Layout::vertical([
        Constraint::Length(u16::from(area.height >= 4)),
        Constraint::Fill(1),
    ])
    .areas(area);
    let mut layout = ResolverHistoryLayout {
        heading,
        history: Vec::with_capacity(3),
    };
    if documents.is_empty() {
        return layout;
    }
    let Some(file) = resolver.files.get(resolver.current_file) else {
        return layout;
    };
    let mut sources = Vec::with_capacity(3);
    for index in [
        Some(resolver.history_sources[0]),
        resolver.selected_base,
        Some(resolver.history_sources[1]),
    ]
    .into_iter()
    .flatten()
    {
        if index < file.sources.len() && !sources.contains(&index) {
            sources.push(index);
        }
    }
    let base_below = mode == ResolverLayout::BaseBelow && sources.len() == 3;
    if documents.width < 60 || (base_below && documents.height < 4) {
        let selected = sources
            .iter()
            .copied()
            .find(|index| resolver.history_panes.get(*index) == Some(&focused))
            .or_else(|| sources.first().copied());
        if let Some(selected) = selected {
            layout.history.push((selected, documents));
        }
    } else if base_below {
        let [inputs, base] = Layout::vertical([Constraint::Fill(1); 2]).areas(documents);
        let [left, right] = Layout::horizontal([Constraint::Fill(1); 2]).areas(inputs);
        layout
            .history
            .extend([(sources[0], left), (sources[2], right), (sources[1], base)]);
    } else {
        let columns = Layout::horizontal(vec![Constraint::Fill(1); sources.len()]).split(documents);
        layout
            .history
            .extend(sources.into_iter().zip(columns.iter().copied()));
    }
    layout
}

fn resolver_status(status: &ResolverStatus) -> (&'static str, Color) {
    match status {
        ResolverStatus::Unresolved => ("unresolved", Color::Yellow),
        ResolverStatus::Unsaved => ("edited · unsaved", Color::Yellow),
        ResolverStatus::Checking => ("saved · checking jj", Color::Cyan),
        ResolverStatus::Resolved => ("resolved", Color::Green),
        ResolverStatus::Unconfirmed => ("unconfirmed · jj check failed", Color::Red),
    }
}

fn draw_resolver_heading(frame: &mut Frame, resolver: &ResolverWorkspace, heading: Rect) {
    let file = resolver.files.get(resolver.current_file);
    let status = if resolver.loading {
        ("loading", Color::Cyan)
    } else {
        file.map_or(("no conflicted files", Color::Green), |file| {
            resolver_status(&file.status)
        })
    };
    let mut spans = vec![
        Span::styled(
            format!(
                "{} · {} ",
                if resolver.view == ResolverView::History {
                    "History"
                } else {
                    "Resolution"
                },
                status.0
            ),
            Style::default().fg(status.1),
        ),
        Span::raw(file.map_or_else(|| Cow::Borrowed(""), |file| display_path(&file.path))),
    ];
    if let Some(error) = resolver
        .error
        .as_deref()
        .or_else(|| file.and_then(|file| file.error.as_deref()))
    {
        spans.push(Span::styled(
            format!(" · {}", display_text(error)),
            Style::default().fg(Color::Red),
        ));
    }
    frame.render_widget(Paragraph::new(Line::from(spans)), heading);
}

fn resolver_document_panel(frame: &mut Frame, panel: Rect, title: &str, focused: bool) -> Rect {
    let [heading, document] = Layout::vertical([
        Constraint::Length(u16::from(panel.height >= 2)),
        Constraint::Fill(1),
    ])
    .areas(panel);
    frame.render_widget(
        Paragraph::new(display_text(title)).style(
            Style::default()
                .fg(if focused {
                    Color::Cyan
                } else {
                    Color::DarkGray
                })
                .add_modifier(Modifier::BOLD),
        ),
        heading,
    );
    document
}

fn draw_resolver_choices(frame: &mut Frame, resolver: &ResolverWorkspace, area: Rect) {
    let Some(file) = resolver.files.get(resolver.current_file) else {
        return;
    };
    let (status, color) = resolver_status(&file.status);
    let mut lines = vec![
        Line::from(format!(
            "Whole-file conflict · {status} · text editing is unavailable"
        ))
        .style(Style::default().fg(color)),
        Line::from(
            file.whole_file_choice
                .and_then(|index| file.sources.get(index))
                .map_or_else(
                    || "No whole-file choice selected.".to_owned(),
                    |source| format!("Selected: {}", display_text(&source.label)),
                ),
        ),
        Line::from("Choose an explicit input, then :w to save and check jj."),
    ];
    lines.extend(
        file.sources
            .iter()
            .enumerate()
            .filter(|(_, source)| !source.base)
            .map(|(index, source)| {
                Line::from(format!(
                    "{} :resolve.use_source {} · {}",
                    if file.whole_file_choice == Some(index) {
                        ">"
                    } else {
                        " "
                    },
                    index + 1,
                    display_text(&source.label),
                ))
            }),
    );
    frame.render_widget(Paragraph::new(lines).wrap(Wrap { trim: false }), area);
}

#[allow(clippy::too_many_arguments)]
fn draw_document(
    frame: &mut Frame,
    editor: &Editor,
    workspace: Rect,
    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() {
        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.cached_diff_error(None);
    if overlay_area.width == 0 || overlay_area.height == 0 {
        return;
    }
    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 marker_gutter = matches!(
        editor.gutter_style(),
        crate::gutter::GutterStyle::Bar | crate::gutter::GutterStyle::Symbols
    );
    let gutter_width = (digits + 1 + 2 * usize::from(marker_gutter)) 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)));
    let center_row = (height > 0 && width > 0 && editor.take_lsp_center()).then_some(height / 2);
    let toggle_row = center_row.or(toggle_row);
    if center_row.is_some() {
        document.manual = None;
    }
    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.scroll_distance() != Some(0) {
            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 {
        let scroll = editor.take_viewport_scroll(height);
        if scroll != 0 {
            document.anchor = None;
            document.manual = Some(ManualViewport {
                buffer_id: editor.buffer_id(),
                revision: editor.text_revision(),
                caret_reveal_revision: editor.caret_reveal_revision(),
                mode: editor.mode(),
                cursor,
                carets: carets.clone(),
                selections: selections.clone(),
            });
        }
        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,
            };
            for _ in 0..scroll.unsigned_abs() {
                let next = if scroll > 0 {
                    next_visual(&mut document.wrap, editor.lines(), start)
                } else {
                    previous_visual(&mut document.wrap, editor.lines(), start)
                };
                let Some(next) = next else { break };
                start = next;
            }
            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,
                    ),
                };
                let margin = scroll_margin(height, editor.scroll_distance());
                let anchor = toggle_row.or_else(|| {
                    if margin == height / 2 {
                        return Some(margin);
                    }
                    let (first, count) =
                        visual_page(&mut document.wrap, editor.lines(), start, margin + 1);
                    let last =
                        visual_page(&mut document.wrap, editor.lines(), start, height - margin).0;
                    if caret < first || count <= margin {
                        Some(margin)
                    } else if caret > last {
                        Some(height - margin - 1)
                    } else {
                        None
                    }
                });
                if let Some(row) = anchor {
                    start = caret;
                    for _ in 0..row {
                        let Some(previous) =
                            previous_visual(&mut document.wrap, editor.lines(), start)
                        else {
                            break;
                        };
                        start = previous;
                    }
                }
            }
            if document.anchor.is_none() && editor.scroll_distance() == Some(0) {
                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 scroll != 0 {
                *top = top
                    .saturating_add_signed(scroll)
                    .min(editor.lines().len().saturating_sub(height));
            }
            if document.manual.is_none() {
                if toggle_row.is_none() {
                    *top = scroll_offset(*top, cursor.row, height, editor.scroll_distance());
                }
                let column = display_column(&editor.lines()[cursor.row], cursor.column);
                *left = scroll_offset(*left, column, width, editor.scroll_distance());
            }
            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 diagnostic = editor
                        .diagnostics()
                        .filter(|diagnostic| diagnostic_on_row(diagnostic, row))
                        .map(|diagnostic| diagnostic_severity(diagnostic.severity))
                        .min_by_key(|(severity, _, _)| *severity);
                    let style = match diagnostic {
                        Some((_, color, _)) => style.fg(color),
                        None => style,
                    };
                    let number = if row == cursor.row {
                        row + 1
                    } else {
                        row.abs_diff(cursor.row)
                    };
                    let change = editor.gutter_change(row);
                    let color = change.map(|change| match change {
                        crate::gutter::Change::Added => Color::Green,
                        crate::gutter::Change::Removed => Color::Red,
                        crate::gutter::Change::Modified => Color::Yellow,
                    });
                    let style = if editor.gutter_style() == crate::gutter::GutterStyle::LineNumbers
                    {
                        if row == cursor.row {
                            Style::default()
                                .fg(Color::Cyan)
                                .add_modifier(Modifier::BOLD)
                        } else {
                            color
                                .filter(|_| diagnostic.is_none())
                                .map_or(style, |color| style.fg(color))
                        }
                    } else {
                        style
                    };
                    let mut spans = vec![Span::styled(format!("{number:>digits$}"), style)];
                    if marker_gutter {
                        spans.push(Span::raw(" "));
                        let marker = match (editor.gutter_style(), change) {
                            (crate::gutter::GutterStyle::Bar, Some(_)) => "▌",
                            (_, Some(crate::gutter::Change::Added)) => "+",
                            (_, Some(crate::gutter::Change::Removed)) => "-",
                            (_, Some(crate::gutter::Change::Modified)) => "~",
                            (_, None) => " ",
                        };
                        spans.push(Span::styled(
                            marker,
                            Style::default().fg(color.unwrap_or(Color::DarkGray)),
                        ));
                    }
                    spans.push(Span::raw(" "));
                    Line::from(spans)
                })
                .collect();
            frame.render_widget(Paragraph::new(numbers), gutter);
        }
        let lines: Vec<Line> = document
            .visible
            .iter()
            .map(|&(row, _, segment)| {
                Line::from(visible_text(
                    &editor.lines()[row],
                    segment.start,
                    segment.end.saturating_sub(segment.start).min(width),
                    false,
                ))
            })
            .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_whitespace(
                frame,
                line,
                area,
                segment.start,
                editor.whitespace_characters(),
                editor.whitespace_scope(),
                syntax.string_spans(row),
                row + 1 < editor.lines().len(),
                false,
            );
            if editor.highlight_trailing_whitespace() {
                paint_trailing_whitespace(frame, line, area, segment.start);
            }
            paint_editor_line(
                frame,
                editor,
                row,
                area,
                segment.start,
                &carets,
                &selections,
            );
        }
    }
    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,
            );
            document_caret = Some(position);
        }
    }
    if focused
        && document_caret.is_some()
        && let Some(label) = editor.line_blame()
        && let Some((screen_row, &(_, continuation, segment))) = document
            .visible
            .iter()
            .enumerate()
            .rev()
            .find(|(_, (row, _, _))| *row == cursor.row)
    {
        let line = &editor.lines()[cursor.row];
        let end = display_column(line, usize::MAX);
        let start = end.saturating_sub(segment.start).saturating_add(2);
        let label_width = UnicodeWidthStr::width(label);
        if end >= segment.start
            && end <= segment.end
            && (!wrapped || continuation + 1 == document.wrap.segments(cursor.row, line).len())
            && start.saturating_add(label_width) <= width
        {
            frame.render_widget(
                Paragraph::new(label).style(Style::default().fg(Color::DarkGray)),
                Rect::new(
                    viewport.x + start as u16,
                    viewport.y + screen_row as u16,
                    label_width as u16,
                    1,
                ),
            );
        }
    }
    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()
        {
            panels.picker_scroll.distance = editor.scroll_distance();
            draw_file_list(
                frame,
                picker,
                panel,
                editor.file_navigation_hint(),
                panels,
                None,
            );
        }
        draw_overlays(frame, editor, overlay_area, panels.caret, panels);
    }
}

fn draw_floating_input(frame: &mut Frame, editor: &Editor, area: Rect) -> Option<Rect> {
    if area.width == 0 || area.height == 0 {
        return None;
    }
    let width = area.width.min(72);
    let height = area.height.min(3);
    let anchor = if editor.mode() == Mode::Search {
        editor.popup_config().search.anchor
    } else {
        editor.popup_config().command.anchor
    };
    let x = area.x
        + match anchor {
            PopupAnchor::TopLeft | PopupAnchor::CenterLeft | PopupAnchor::BottomLeft => 0,
            PopupAnchor::TopCenter | PopupAnchor::Center | PopupAnchor::BottomCenter => {
                (area.width - width) / 2
            }
            PopupAnchor::TopRight | PopupAnchor::CenterRight | PopupAnchor::BottomRight => {
                area.width - width
            }
        };
    let y = area.y
        + match anchor {
            PopupAnchor::TopLeft | PopupAnchor::TopCenter | PopupAnchor::TopRight => 0,
            PopupAnchor::CenterLeft | PopupAnchor::Center | PopupAnchor::CenterRight => {
                (area.height - height) / 2
            }
            PopupAnchor::BottomLeft | PopupAnchor::BottomCenter | PopupAnchor::BottomRight => {
                area.height - height
            }
        };
    let panel = Rect::new(x, y, width, height);
    let bordered = panel.width >= 4 && panel.height >= 3;
    let padding = u16::from(panel.width.saturating_sub(2 * u16::from(bordered)) >= 3);
    let mut block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .border_style(Style::default().fg(Color::Cyan))
        .padding(ratatui::widgets::Padding::horizontal(padding));
    if bordered {
        block = block.title(if editor.mode() == Mode::Search {
            " Search "
        } else {
            " Command "
        });
    }
    let content = block.inner(panel);
    frame.render_widget(Clear, panel);
    frame.render_widget(block, panel);
    let command = editor.command_line();
    let column = display_column(command, usize::MAX);
    let width = usize::from(content.width);
    let offset = column.saturating_sub(width.saturating_sub(1));
    frame.render_widget(
        Paragraph::new(visible_line(command, offset, width)),
        content,
    );
    frame.set_cursor_position((content.x + (column - offset) as u16, content.y));
    Some(panel)
}

fn draw_notification(frame: &mut Frame, editor: &Editor, area: Rect) -> Option<Rect> {
    if !editor.notification_visible() || area.width == 0 || area.height == 0 {
        return None;
    }
    let message = if let Some(diagnostic) = editor.diagnostic_at_cursor() {
        let (_, _, label) = diagnostic_severity(diagnostic.severity);
        let diagnostic = &diagnostic.message;
        Cow::Owned(if editor.message().is_empty() {
            format!("{label}: {diagnostic}")
        } else {
            format!("{} | {label}: {diagnostic}", editor.message())
        })
    } else {
        Cow::Borrowed(editor.message())
    };
    if message.is_empty() {
        return None;
    }
    let message = if message.chars().any(char::is_control) {
        Cow::Owned(display_text(&message))
    } else {
        message
    };
    let width = (UnicodeWidthStr::width(message.as_ref()).saturating_add(if area.height >= 3 {
        4
    } else {
        2
    }))
    .min(60)
    .min(usize::from(area.width)) as u16;
    let bordered = width >= 4 && area.height >= 3;
    let border = 2 * u16::from(bordered);
    let padding = u16::from(width.saturating_sub(border) >= 3);
    let paragraph = Paragraph::new(message).wrap(Wrap { trim: false });
    let height = (paragraph.line_count(width - border - 2 * padding).min(6) as u16 + border)
        .min(area.height);
    let panel = Rect::new(area.right() - width, area.bottom() - height, width, height);
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .border_style(Style::default().fg(Color::DarkGray))
        .padding(ratatui::widgets::Padding::horizontal(padding));
    let content = block.inner(panel);
    frame.render_widget(Clear, panel);
    frame.render_widget(block, panel);
    frame.render_widget(paragraph, content);
    Some(panel)
}

fn draw_overlays(
    frame: &mut Frame,
    editor: &Editor,
    area: Rect,
    caret: Option<(Rect, Position)>,
    panels: &mut WheelPanels,
) {
    panels.picker_scroll.distance = editor.scroll_distance();
    if editor.completion().is_none() {
        panels.picker_scroll.completion = None;
    }
    if editor.palette().is_none() {
        panels.picker_scroll.palette = None;
    }
    if editor.diff().is_none_or(|diff| diff.phase == Phase::View) {
        panels.picker_scroll.revisions = None;
    }
    panels.input = None;
    panels.notification = None;
    let covered = editor.completion().is_some()
        || editor.palette().is_some()
        || editor.hover().is_some()
        || editor.startup_diagnostic().is_some()
        || editor.command_output().is_some()
        || editor
            .file_picker()
            .is_some_and(|picker| picker.presentation == FilePresentation::Floating);
    if !covered {
        if matches!(editor.mode(), Mode::Command | Mode::Search) {
            panels.input = draw_floating_input(frame, editor, area);
        } else if editor.diff().is_none_or(|diff| diff.phase == Phase::View)
            && !editor.file_picker().is_some_and(|picker| picker.focused)
        {
            panels.notification = draw_notification(frame, editor, area);
        }
    }
    if !matches!(editor.mode(), Mode::Command | Mode::Search)
        && editor.command_output().is_none()
        && !editor.file_picker().is_some_and(|picker| picker.focused)
        && let Some((_, position)) = caret
        && !panels
            .notification
            .is_some_and(|panel| panel.contains(position))
    {
        frame.set_cursor_position(position);
    }
    if let Some(completion) = editor.completion()
        && let Some((_, caret)) = caret
    {
        panels.completion = draw_completion(frame, completion, area, caret, panels);
    }
    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.picker_diff().and_then(|diff| {
                diff.comparison
                    .as_ref()
                    .map(|comparison| (comparison.files.as_slice(), &diff.reviewed_files))
            }),
        );
    }
    if let Some(palette) = editor.palette() {
        draw_palette(
            frame,
            palette,
            area,
            editor.mode(),
            editor.selection_navigation_hint(),
            panels,
        );
    }
    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);
    }
    if let Some(output) = editor.command_output() {
        draw_diagnostic_panel(frame, &output.content, area, &output.title, Some(output));
    }
}

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

fn diff_panel(
    frame: &mut Frame,
    area: Rect,
    title: &str,
    state: &str,
    revision: &str,
    focused: bool,
) -> Rect {
    if area.width < 4 || area.height < 4 {
        return area;
    }
    let title_width = usize::from(area.width - 2)
        .saturating_sub(UnicodeWidthStr::width(state) + usize::from(!state.is_empty()));
    let title = if UnicodeWidthStr::width(title) > title_width {
        Cow::Owned(visible_line(title, 0, title_width))
    } else {
        Cow::Borrowed(title)
    };
    let block = Block::default()
        .borders(Borders::ALL)
        .border_style(Style::default().fg(if focused {
            Color::Cyan
        } else {
            Color::DarkGray
        }))
        .title_top(Line::from(title).left_aligned())
        .title_top(Line::from(state).right_aligned())
        .title_bottom(Line::from(revision).left_aligned());
    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);
    }
}

#[allow(clippy::too_many_arguments)]
fn paint_whitespace(
    frame: &mut Frame,
    line: &str,
    area: Rect,
    left: usize,
    characters: &BTreeMap<char, char>,
    scope: WhitespaceScope,
    strings: &[SyntaxSpan],
    newline: bool,
    sanitize_controls: bool,
) {
    if characters.is_empty() || area.width == 0 || area.height == 0 {
        return;
    }
    let leading_end = match scope {
        WhitespaceScope::All => line.len(),
        WhitespaceScope::Leading => line.len() - line.trim_start_matches(char::is_whitespace).len(),
    };
    let right = left.saturating_add(usize::from(area.width));
    let style = Style::default()
        .fg(Color::Reset)
        .add_modifier(Modifier::DIM);
    let mut strings = strings.iter().peekable();
    let mut column = 0;
    for (byte, grapheme) in line.grapheme_indices(true) {
        if column >= right {
            return;
        }
        let control = sanitize_controls && grapheme.chars().any(|ch| ch.is_control() && ch != '\t');
        let cells = if control {
            grapheme.chars().count()
        } else if grapheme == "\t" {
            TAB_WIDTH - column % TAB_WIDTH
        } else {
            UnicodeWidthStr::width(grapheme)
        };
        let end = column + cells;
        while strings.peek().is_some_and(|span| span.end_byte <= byte) {
            strings.next();
        }
        let protected = strings
            .peek()
            .is_some_and(|span| span.start_byte < byte + grapheme.len());
        if byte < leading_end && !protected && cells > 0 {
            let ch = grapheme.chars().next().unwrap();
            if grapheme.len() == ch.len_utf8()
                && let Some(&marker) = characters.get(&ch)
            {
                // Ratatui resets covered wide-glyph cells; restore their source style when exposed.
                let wide_style = (cells > 1 && grapheme != "\t" && column >= left)
                    .then(|| frame.buffer_mut()[(area.x + (column - left) as u16, area.y)].style());
                for cell in column.max(left)..end.min(right) {
                    let cell = &mut frame.buffer_mut()[(area.x + (cell - left) as u16, area.y)];
                    cell.set_symbol(" ");
                    if let Some(style) = wide_style {
                        cell.set_style(style);
                    }
                }
                if column >= left {
                    frame.buffer_mut()[(area.x + (column - left) as u16, area.y)]
                        .set_char(marker)
                        .set_style(style);
                }
            }
        }
        column = end;
    }
    while strings
        .peek()
        .is_some_and(|span| span.end_byte <= line.len())
    {
        strings.next();
    }
    if newline
        && column >= left
        && column < right
        && strings
            .peek()
            .is_none_or(|span| span.start_byte > line.len())
        && let Some(&marker) = characters.get(&'\n')
    {
        frame.buffer_mut()[(area.x + (column - left) as u16, area.y)]
            .set_char(marker)
            .set_style(style);
    }
}

fn paint_trailing_whitespace(frame: &mut Frame, line: &str, area: Rect, left: usize) {
    let prefix = line.trim_end_matches(char::is_whitespace);
    if prefix.len() == line.len() {
        return;
    }
    paint_cells(
        frame,
        area,
        left,
        display_column(prefix, usize::MAX),
        display_column(line, usize::MAX),
        Style::default().bg(Color::Red),
    );
}

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);
        }
    }
    for found in editor.search_matches_on_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,
    view: ColumnView<'_>,
    area: Rect,
    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;
    let focus = view.info.focus;
    for (screen, display, segments) in
        diff_screen_rows(view.info.display_len, top, area.height, wrapped)
    {
        let Some(source) = view.native_row(display) 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.render_pane_focused()
            && (editor.diff_interacting()
                || editor
                    .resolver()
                    .is_some_and(|resolver| resolver.view == ResolverView::History))
        {
            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));
            }
        }
    }
    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;
    }
    panels.caret = caret;
    if !panels.workspace_managed {
        draw_overlays(frame, editor, area, caret, panels);
    }
}

fn draw_diff(
    frame: &mut Frame,
    diff: &DiffState,
    area: Rect,
    navigation_hint: &str,
    file_navigation_hint: &str,
    panels: &mut WheelPanels,
    editor: Option<&Editor>,
) {
    if let Some(editor) = editor {
        panels.picker_scroll.distance = editor.scroll_distance();
    }
    if diff.phase == Phase::View {
        panels.picker_scroll.revisions = None;
    }
    let comparison = diff.comparison.as_ref();
    let selected = comparison.and_then(|comparison| comparison.files.get(diff.file));
    let syntax_error = panels.cached_diff_error(Some(diff));
    if area.width == 0 || area.height == 0 {
        return;
    }
    if diff.phase != Phase::View {
        let pull_requests = diff.pull_request_remote.is_some();
        let panel = floating_panel(area);
        frame.render_widget(Clear, panel);
        let stage = if diff.phase == Phase::Before {
            "Before"
        } else {
            "After"
        };
        let title = if pull_requests {
            " Pull requests ".into()
        } else {
            format!(" Diff · Choose {stage} · {} ", diff.comparison_mode.label())
        };
        let content = diff_panel(frame, panel, &title, "", "", true);
        let pull_request_notice = (pull_requests && diff.phase == Phase::Before)
            .then(|| diff.pull_request_notice())
            .flatten();
        let notice = diff
            .error
            .as_deref()
            .or(pull_request_notice.as_deref())
            .or_else(|| {
                if diff.loading {
                    Some(
                        if diff.after.is_some() || (pull_requests && diff.phase == Phase::After) {
                            "Loading comparison…"
                        } else if pull_requests {
                            "Loading pull requests…"
                        } 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(!pull_requests && 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());
        let stage_text = if pull_requests {
            if diff.pull_request_partial() {
                "Partial search · Select a loaded pull request".into()
            } else {
                "Select a pull request to compare its branch changes".into()
            }
        } else {
            format!(
                "{} · Ctrl+b toggle · Before: {}",
                diff.comparison_mode.label(),
                display_text(before)
            )
        };
        frame.render_widget(Paragraph::new(stage_text), stage_area);
        if pull_requests || diff.catalog.is_some() {
            let tabs: Vec<Span> = diff
                .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!(
            "> {}{}",
            if pull_requests && diff.pull_request_partial() {
                "[partial] "
            } else {
                ""
            },
            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 !pull_requests && 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 pinned = usize::from(!pull_requests);
        let mut key = std::collections::hash_map::DefaultHasher::new();
        (
            diff.phase as u8,
            diff.category,
            &diff.query,
            diff.comparison_mode as u8,
            diff.catalog
                .as_ref()
                .map(|catalog| (catalog.entries.as_ptr(), catalog.entries.len())),
        )
            .hash(&mut key);
        let first = PickerViewport::follow(
            &mut panels.picker_scroll.revisions,
            key.finish(),
            diff.selected.saturating_sub(pinned),
            usize::from(results.height),
            row_height,
            panels.picker_scroll.distance,
        );
        let mut lines = Vec::with_capacity(count * row_height);
        for (index, revision) in entries
            .enumerate()
            .skip(first)
            .map(|(index, revision)| (index + pinned, revision))
            .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()
            && !(if pull_requests {
                diff.pull_request_partial()
            } else {
                diff.loading
            })
            && diff.error.is_none()
        {
            let empty = if pull_requests {
                "No matching pull requests"
            } else {
                "No matching revisions"
            };
            frame.render_widget(Paragraph::new(empty), results);
        } else {
            frame.render_widget(Paragraph::new(lines), results);
        }
        let accept = if diff.error.is_some() {
            "retry"
        } else {
            "select"
        };
        let retry = if pull_requests {
            " · Ctrl+r retry category"
        } else {
            ""
        };
        frame.render_widget(
            Paragraph::new(format!(
                "{navigation_hint} · Tab categories · type search · Enter {accept}{retry} · Esc close · Ctrl+p actions"
            ))
            .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,
            view_mode: diff.view_mode,
            split_axis: diff.split_axis,
            caret_row: None,
        });
        if let Some(editor) = editor {
            draw_diff_popups(frame, editor, area, None, panels);
        }
        return;
    }
    frame.render_widget(Clear, area);

    let resolver = editor
        .and_then(Editor::resolver)
        .filter(|resolver| resolver.view == ResolverView::Resolution);
    let resolver_error = resolver.and_then(|resolver| {
        resolver.error.as_deref().or_else(|| {
            resolver
                .files
                .get(resolver.current_file)
                .and_then(|file| file.error.as_deref())
        })
    });
    let notice = diff.error.as_deref().or(resolver_error).or_else(|| {
        if diff.loading || resolver.is_some_and(|resolver| resolver.loading) {
            Some("Loading file…")
        } else {
            syntax_error.or_else(|| selected.and_then(|file| file.notice.as_deref()))
        }
    });
    let [notice_area, workspace] = Layout::vertical([
        Constraint::Length(u16::from(notice.is_some() && area.height >= 3)),
        Constraint::Fill(1),
    ])
    .areas(area);
    if let Some(notice) = notice {
        frame.render_widget(
            Paragraph::new(display_text(notice)).style(Style::default().fg(
                if diff.error.is_some() || resolver_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)
    };
    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(), &diff.reviewed_files)),
        );
    }
    let document_caret = panels.draw_documents(frame, diff, panes, navigator, editor);
    if let Some(editor) = editor {
        draw_diff_popups(frame, editor, area, document_caret, panels);
    }
}

impl WheelPanels {
    /// Read the previous draw's error without changing notice-layout timing.
    fn cached_diff_error(&mut self, diff: Option<&DiffState>) -> Option<&str> {
        if diff.is_none_or(|diff| diff.phase != Phase::View || !diff.selected_file_loaded()) {
            self.diff_syntax = None;
        }
        self.diff_syntax
            .as_ref()
            .and_then(|syntax| syntax.before.error().or_else(|| syntax.after.error()))
    }

    /// Publish geometry and return the caret only after all document overlays.
    fn draw_documents(
        &mut self,
        frame: &mut Frame,
        diff: &DiffState,
        panes: Rect,
        navigator: Option<Rect>,
        editor: Option<&Editor>,
    ) -> Option<(Rect, Position)> {
        self.cached_diff_error(Some(diff));
        let selected = diff
            .comparison
            .as_ref()
            .and_then(|comparison| comparison.files.get(diff.file));
        let resolver = editor
            .and_then(Editor::resolver)
            .filter(|resolver| resolver.view == ResolverView::Resolution);
        if let Some(resolver) = resolver.filter(|resolver| {
            resolver
                .files
                .get(resolver.current_file)
                .is_some_and(|file| !file.text)
        }) {
            draw_resolver_choices(frame, resolver, panes);
            self.diff = Some(DiffGeometry {
                regions: [
                    (navigator.unwrap_or_default(), Focus::Files),
                    (Rect::default(), Focus::Before),
                    (Rect::default(), Focus::After),
                ],
                viewport: None,
                text_widths: [0; 2],
                wrapping: diff.word_wrap,
                view_mode: diff.view_mode,
                split_axis: diff.split_axis,
                caret_row: None,
            });
            return None;
        }
        let pane_layout = diff.pane_layout();
        let unified = diff.view_mode == ViewMode::Unified;
        let [before_area, after_area] = if unified {
            [panes, panes]
        } else {
            match pane_layout {
                PaneLayout::Split => {
                    split_rect(pane_rect(panes), diff.split_axis).map(terminal_rect)
                }
                PaneLayout::Before | PaneLayout::Empty => [panes, Rect::default()],
                PaneLayout::After => [Rect::default(), panes],
            }
        };
        // Parse complete trees before projecting context; color only visible source rows below.
        if let Some(id) = diff.comparison_id
            && let Some(file) = selected.filter(|file| file.loaded)
        {
            self.diff_syntax
                .get_or_insert_with(DiffSyntaxCache::default)
                .update(
                    id,
                    diff.file,
                    file,
                    diff.after_source_lines(file),
                    diff.live_revision,
                    Some(DiffSyntaxViewport {
                        diff,
                        top: diff.top,
                        areas: [Rect::default(); 2],
                        wrapped: None,
                    }),
                );
        }
        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 = self
            .previous_diff
            .as_ref()
            .filter(|previous| {
                (previous.wrapping != wrapping
                    || previous.view_mode != diff.view_mode
                    || previous.split_axis != diff.split_axis)
                    && previous.viewport.is_some_and(|(id, file, _, _, _)| {
                        Some(id) == diff.comparison_id && file == diff.file
                    })
            })
            .and_then(|previous| {
                editor?.diff_buffer_focus()?;
                previous.caret_row
            });
        let center_row = editor.and_then(|editor| {
            let focus = editor.diff_buffer_focus()?;
            let pane = if focus == Focus::Before {
                before_area
            } else {
                after_area
            };
            let height = usize::from(diff_inner(pane).height);
            let file = selected.filter(|file| file.loaded)?;
            (editor.diff_interacting()
                && diff.follow_caret
                && height > 0
                && diff_pane_text_width(diff, file, pane, focus) > 0
                && diff
                    .source_display_row(focus, editor.cursor().row)
                    .is_some()
                && editor.take_lsp_center())
            .then_some(height / 2)
        });
        let toggle_row = center_row.or(toggle_row);
        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 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 width = selected.map_or_else(
                || diff_text_width(pane, source_len),
                |file| diff_pane_text_width(diff, file, pane, focus),
            );
            let column =
                display_column(&editor.lines()[editor.cursor().row], editor.cursor().column);
            *left = scroll_offset(*left, column, width, editor.scroll_distance());
        }
        if let Some(file) = selected.filter(|file| file.loaded)
            && let Some(syntax) = &self.diff_syntax
        {
            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 = self.diff_wrap.get_or_insert_with(DiffWrapViewport::default);
            viewport.lefts = [before_left, after_left];
            viewport.update(
                diff,
                file,
                [before_area, after_area],
                caret,
                toggle_row,
                editor.map_or(Some(0), Editor::scroll_distance),
                syntax,
            );
            let height = editor
                .and_then(|editor| editor.diff_buffer_focus())
                .map_or(0, |focus| {
                    usize::from(
                        diff_inner(if focus == Focus::Before {
                            before_area
                        } else {
                            after_area
                        })
                        .height,
                    )
                });
            if height > 0 {
                let scroll = editor.map_or(0, |editor| editor.take_viewport_scroll(height));
                for _ in 0..scroll.unsigned_abs() {
                    let next = viewport.step(diff, file, viewport.top, scroll > 0);
                    if next == viewport.top {
                        break;
                    }
                    viewport.top = next;
                }
                if scroll != 0 {
                    viewport.fill(
                        diff,
                        file,
                        viewport.heights[0].max(viewport.heights[1]),
                        syntax,
                    );
                }
            }
            top = viewport.top.display;
        } else {
            self.diff_wrap = None;
        }
        if let Some(id) = diff.comparison_id
            && let Some(file) = selected.filter(|file| file.loaded)
        {
            let wrapped = self
                .diff_wrap
                .as_ref()
                .map(|viewport| viewport.rows.as_slice());
            self.diff_syntax
                .get_or_insert_with(DiffSyntaxCache::default)
                .update(
                    id,
                    diff.file,
                    file,
                    diff.after_source_lines(file),
                    diff.live_revision,
                    Some(DiffSyntaxViewport {
                        diff,
                        top,
                        areas: [before_area, after_area],
                        wrapped,
                    }),
                );
        }
        let mut text_widths = [0; 2];
        let previous_text_widths = self
            .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 = self
            .diff_wrap
            .as_ref()
            .map(|viewport| viewport.rows.as_slice());
        if let Some(file) = selected.filter(|file| file.loaded)
            && let Some(syntax) = &self.diff_syntax
        {
            if pane_layout == PaneLayout::Empty {
                diff_pane_panel(frame, diff, Some(file), before_area, true, resolver);
            } else {
                if before_area != Rect::default() && (!unified || diff.focus == Focus::Before) {
                    let text_area = draw_diff_pane(
                        frame,
                        diff,
                        file,
                        before_area,
                        true,
                        [&syntax.before, &syntax.after],
                        [
                            editor.map_or(&[], |editor| editor.diff_semantic_tokens(Focus::Before)),
                            editor.map_or(&[], |editor| editor.diff_semantic_tokens(Focus::After)),
                        ],
                        (
                            top,
                            &mut before_left,
                            previous_text_widths.map(|widths| widths[0]),
                        ),
                        wrapped,
                        self.diff_colors,
                        editor.is_some_and(Editor::highlight_trailing_whitespace),
                        editor.map(Editor::whitespace_characters),
                        editor.map_or(WhitespaceScope::All, Editor::whitespace_scope),
                        resolver,
                        false,
                    );
                    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.column_view(Focus::Before).unwrap(),
                            text_area,
                            (top, before_left),
                            wrapped,
                        )
                        .map(|position| (text_area, position));
                    }
                }
                if after_area != Rect::default() && (!unified || diff.focus != Focus::Before) {
                    let text_area = draw_diff_pane(
                        frame,
                        diff,
                        file,
                        after_area,
                        false,
                        [&syntax.before, &syntax.after],
                        [
                            editor.map_or(&[], |editor| editor.diff_semantic_tokens(Focus::Before)),
                            editor.map_or(&[], |editor| editor.diff_semantic_tokens(Focus::After)),
                        ],
                        (
                            top,
                            &mut after_left,
                            previous_text_widths.map(|widths| widths[1]),
                        ),
                        wrapped,
                        self.diff_colors,
                        editor.is_some_and(Editor::highlight_trailing_whitespace),
                        editor.map(Editor::whitespace_characters),
                        editor.map_or(WhitespaceScope::All, Editor::whitespace_scope),
                        resolver,
                        false,
                    );
                    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.column_view(Focus::After).unwrap(),
                            text_area,
                            (top, after_left),
                            wrapped,
                        )
                        .map(|position| (text_area, position));
                    }
                }
            }
        } else {
            let content = diff_pane_panel(frame, diff, selected, panes, true, resolver);
            frame.render_widget(
                Paragraph::new(display_text(if diff.loading {
                    "Loading file…"
                } else if let Some(error) = diff.error.as_deref() {
                    error
                } else if selected.is_some() {
                    "File details unavailable · select the file to retry"
                } else {
                    "No changed files"
                }))
                .wrap(Wrap { trim: false })
                .style(Style::default().fg(if diff.error.is_some() {
                    Color::Red
                } else {
                    Color::Reset
                })),
                content,
            );
        }
        if let (Some(file), Some(syntax), Some(viewport)) = (
            selected.filter(|file| file.loaded),
            self.diff_syntax.as_ref(),
            self.diff_wrap.as_ref(),
        ) {
            draw_diff_scope_labels(
                frame,
                diff,
                file,
                syntax,
                viewport,
                [before_area, after_area],
                [before_left, after_left],
                &mut document_caret,
            );
        }
        self.diff = Some(DiffGeometry {
            regions: [
                (navigator.unwrap_or_default(), Focus::Files),
                (
                    if unified && diff.focus != Focus::Before {
                        Rect::default()
                    } else {
                        before_area
                    },
                    Focus::Before,
                ),
                (
                    if unified && diff.focus == Focus::Before {
                        Rect::default()
                    } else {
                        after_area
                    },
                    Focus::After,
                ),
            ],
            viewport: diff
                .comparison_id
                .map(|id| (id, diff.file, top, before_left, after_left)),
            text_widths,
            wrapping,
            view_mode: diff.view_mode,
            split_axis: diff.split_axis,
            caret_row: document_caret
                .map(|(text_area, caret)| usize::from(caret.y.saturating_sub(text_area.y))),
        });
        document_caret
    }
}

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

fn diff_pane_panel(
    frame: &mut Frame,
    diff: &DiffState,
    file: Option<&ChangedFile>,
    area: Rect,
    before: bool,
    resolver: Option<&ResolverWorkspace>,
) -> Rect {
    if area.width < 4 || area.height < 4 {
        return area;
    }
    let focus = if before { Focus::Before } else { Focus::After };
    if let Some(resolver) = resolver {
        let file = resolver.files.get(resolver.current_file);
        let title = if before {
            " Resolution "
        } else {
            " Other version "
        };
        let state = if before {
            format!(
                " editable · {} ",
                file.map_or("loading", |file| resolver_status(&file.status).0)
            )
        } else {
            " read-only ".to_owned()
        };
        let source = if before {
            String::new()
        } else {
            file.and_then(|file| file.sources.get(resolver.selected_source))
                .map_or_else(String::new, |source| {
                    format!(" {} ", display_text(&source.label))
                })
        };
        return diff_panel(frame, area, title, &state, &source, diff.focus == focus);
    }
    let label = diff.side_label(focus);
    let title = file.map_or_else(
        || format!(" Diff · {} ", diff.comparison_mode.label()),
        |file| {
            let label = if diff.view_mode == ViewMode::Unified {
                Cow::Owned(format!("Unified · {label}"))
            } else {
                Cow::Borrowed(label)
            };
            let path = if before {
                file.old_path.as_ref().unwrap_or(&file.path)
            } else {
                &file.path
            };
            format!(
                " {label} · {} · {} · {} ",
                diff_status(file.status),
                display_text(&path.to_string_lossy()),
                diff.comparison_mode.label()
            )
        },
    );
    let revision = diff
        .comparison
        .as_ref()
        .map_or_else(String::new, |comparison| {
            if diff.view_mode == ViewMode::Split && diff.pane_layout() == PaneLayout::Split {
                format!(
                    " {} ",
                    display_text(if before {
                        &comparison.before
                    } else {
                        &comparison.after
                    })
                )
            } else {
                format!(
                    " {} → {} ",
                    display_text(&comparison.before),
                    display_text(&comparison.after)
                )
            }
        });
    let access = if diff.side_editable(focus) {
        " editable "
    } else {
        " read-only "
    };
    diff_panel(frame, area, &title, access, &revision, diff.focus == focus)
}

#[allow(clippy::too_many_arguments)]
fn draw_diff_scope_labels(
    frame: &mut Frame,
    diff: &DiffState,
    file: &ChangedFile,
    syntax: &DiffSyntaxCache,
    viewport: &DiffWrapViewport,
    areas: [Rect; 2],
    lefts: [usize; 2],
    caret: &mut Option<(Rect, Position)>,
) {
    let unified = diff.view_mode == ViewMode::Unified;
    for (pane, focus) in [Focus::Before, Focus::After].into_iter().enumerate() {
        if areas[pane].is_empty() || (unified && (diff.focus == Focus::Before) != (pane == 0)) {
            continue;
        }
        let content = diff_inner(areas[pane]);
        let gutter = diff_gutter(diff, file, usize::from(content.width), focus);
        let width = usize::from(content.width).saturating_sub(gutter);
        for (screen, row) in viewport
            .rows
            .iter()
            .take(usize::from(content.height))
            .enumerate()
        {
            let overlay = row.scope == [false; 2];
            if overlay && !row.unwrapped {
                continue;
            }
            let contexts = syntax.scopes(diff, row.position.display);
            let side = if !unified {
                pane
            } else if overlay {
                usize::from(diff.display_focus(row.position.display) != Some(Focus::Before))
            } else {
                usize::from(!row.scope[0])
            };
            let Some(scope) = contexts[side] else {
                continue;
            };
            let y = content.y + screen as u16;
            let y = if overlay {
                let source_focus = if side == 0 {
                    Focus::Before
                } else {
                    Focus::After
                };
                if diff.display_source_row(source_focus, row.position.display)
                    != Some(scope.name.row)
                {
                    continue;
                }
                let source = if side == 0 { &file.before } else { &file.after };
                let prefix = &source[scope.name.row][..scope.name.column];
                let column = display_column(prefix, usize::MAX);
                if lefts[pane] <= column && column < lefts[pane].saturating_add(width) {
                    continue;
                }
                let Some(y) = y.checked_sub(1).filter(|&y| y >= content.y) else {
                    continue;
                };
                let previous = &viewport.rows[screen - 1];
                let previous_focus = if unified {
                    diff.display_focus(previous.position.display)
                        .unwrap_or(focus)
                } else {
                    focus
                };
                let previous_side = usize::from(previous_focus == Focus::After);
                if previous.scope == [false; 2]
                    && let Some(previous_scope) =
                        syntax.scopes(diff, previous.position.display)[previous_side]
                    && diff.display_source_row(previous_focus, previous.position.display)
                        == Some(previous_scope.name.row)
                {
                    let source = if previous_side == 0 {
                        &file.before
                    } else {
                        &file.after
                    };
                    let prefix = &source[previous_scope.name.row][..previous_scope.name.column];
                    let column = display_column(prefix, usize::MAX);
                    if lefts[pane] <= column && column < lefts[pane].saturating_add(width) {
                        continue;
                    }
                }
                y
            } else {
                if !row.scope[side] {
                    continue;
                }
                y
            };
            let shared = if overlay {
                contexts[0].map(|scope| scope.label) == contexts[1].map(|scope| scope.label)
            } else {
                row.scope == [true; 2]
            };
            let prefix = if width < 4 {
                ""
            } else if !unified {
                "› "
            } else if shared {
                "± "
            } else if side == 0 {
                "− "
            } else {
                "+ "
            };
            let prefix_width = UnicodeWidthStr::width(prefix);
            let available = width.saturating_sub(prefix_width);
            let label = if UnicodeWidthStr::width(scope.label) > available {
                scope.label.rsplit(" › ").next().unwrap_or(scope.label)
            } else {
                scope.label
            };
            let style = Style::default()
                .fg(Color::DarkGray)
                .add_modifier(Modifier::ITALIC);
            let x = content.x + gutter as u16;
            let buffer = frame.buffer_mut();
            for x in content.x..content.right() {
                buffer[(x, y)].reset();
            }
            buffer.set_stringn(x, y, prefix, width, style);
            buffer.set_stringn(x + prefix_width as u16, y, label, available, style);
            if caret.is_some_and(|(_, position)| {
                position.y == y && content.x <= position.x && position.x < content.right()
            }) {
                *caret = None;
            }
        }
    }
}

#[allow(clippy::too_many_arguments)]
fn draw_diff_pane(
    frame: &mut Frame,
    diff: &DiffState,
    file: &ChangedFile,
    area: Rect,
    before: bool,
    syntax: [&SyntaxCache; 2],
    semantic: [&[SemanticToken]; 2],
    viewport: (usize, &mut usize, Option<u16>),
    wrapped: Option<&[WrappedDiffRow]>,
    colors: DiffColors,
    highlight_trailing_whitespace: bool,
    whitespace_characters: Option<&BTreeMap<char, char>>,
    whitespace_scope: WhitespaceScope,
    resolver: Option<&ResolverWorkspace>,
    content_only: bool,
) -> Rect {
    if area.width == 0 || area.height == 0 {
        return area;
    }
    let focus = if before { Focus::Before } else { Focus::After };
    let content = if content_only {
        area
    } else {
        diff_pane_panel(frame, diff, Some(file), area, before, resolver)
    };
    let view = diff.column_view(focus).expect("prepared comparison column");
    let unified = diff.view_mode == ViewMode::Unified;
    let (top, left, previous_width) = viewport;
    let gutter = diff_gutter(diff, file, usize::from(content.width), focus);
    let width = usize::from(content.width).saturating_sub(gutter);
    if view.info.display_len > 0
        && !diff.word_wrap
        && !content_only
        && previous_width.is_some_and(|previous| usize::from(previous) != width)
    {
        *left = diff.bound_horizontal(focus, *left, width);
    }
    let left = *left;
    let review_comments = diff
        .local_review
        .document
        .comments
        .iter()
        .filter(|comment| {
            let before = comment.anchor.side == crate::review::Side::Before;
            let path = if before {
                file.old_path.as_ref().unwrap_or(&file.path)
            } else {
                &file.path
            };
            (unified || before == (focus == Focus::Before))
                && comment.anchor.path == *path
                && diff.review_anchor_current(&comment.anchor)
        });
    paint_diff_content(
        frame,
        view,
        content,
        syntax,
        semantic,
        (top, left),
        wrapped,
        colors,
        highlight_trailing_whitespace,
        whitespace_characters,
        whitespace_scope,
        review_comments,
        diff.local_review.selected,
    )
}

#[allow(clippy::too_many_arguments)]
fn paint_diff_content<'a>(
    frame: &mut Frame,
    view: ColumnView<'a>,
    content: Rect,
    syntax: [&SyntaxCache; 2],
    semantic: [&[SemanticToken]; 2],
    viewport: (usize, usize),
    wrapped: Option<&[WrappedDiffRow]>,
    colors: DiffColors,
    highlight_trailing_whitespace: bool,
    whitespace_characters: Option<&BTreeMap<char, char>>,
    whitespace_scope: WhitespaceScope,
    review_comments: impl Iterator<Item = &'a crate::review::Comment> + Clone,
    selected_review: Option<u64>,
) -> Rect {
    if view.info.display_len == 0 {
        let notice = match view.info.empty {
            ColumnEmpty::Notice(text) => display_text(text),
            ColumnEmpty::EmptyFile => "Empty file".into(),
            ColumnEmpty::NoChanges => "No text changes".into(),
        };
        frame.render_widget(Paragraph::new(notice), content);
        return content;
    }
    let unified = view.info.unified;
    let (top, left) = viewport;
    let gutter = column_gutter(
        unified,
        view.info.source_extents,
        usize::from(content.width),
        view.info.focus,
    );
    let width = usize::from(content.width).saturating_sub(gutter);
    let selected_anchor = review_comments
        .clone()
        .find(|comment| selected_review == Some(comment.id))
        .map(|comment| &comment.anchor);
    for (screen, display_row, segments) in
        diff_screen_rows(view.info.display_len, top, content.height, wrapped)
    {
        let row_area = Rect::new(content.x, content.y + screen as u16, content.width, 1);
        let line = match view.row(display_row) {
            Some(ColumnRow::Fold { hidden }) => {
                frame.render_widget(
                    Paragraph::new(format!(
                        "… {} unchanged lines hidden · [/] expand context",
                        hidden
                    ))
                    .style(Style::default().fg(Color::DarkGray)),
                    row_area,
                );
                continue;
            }
            Some(ColumnRow::Text(line)) => line,
            Some(ColumnRow::Gap) => {
                let style = Style::default().fg(Color::DarkGray).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;
            }
            None => continue,
        };
        let Some(source_text) = line.text else {
            continue;
        };
        let before = line.side == Focus::Before;
        let index = line.source_row;
        let segment = segments.and_then(|segments| segments[usize::from(!before)]);
        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 = line.changed;
        let background = if changed && line.emphasize {
            colors.row[usize::from(!before)]
        } else {
            Color::Reset
        };
        frame
            .buffer_mut()
            .set_style(row_area, Style::default().bg(background));
        if segments.is_some() && segment.is_none() {
            continue;
        }
        frame.render_widget(
            Paragraph::new(visible_text(source_text, left, text_width.min(width), true))
                .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
            };
            let label = if unified {
                let [old, new] = line.numbers.map(|row| row.map(|row| row + 1));
                let [old_digits, new_digits] = view
                    .info
                    .stored_lengths
                    .map(|len| len.max(1).ilog10() as usize + 1);
                match (old, new) {
                    (Some(old), Some(new)) => {
                        format!("{old:>old_digits$} {new:>new_digits$}{marker} ")
                    }
                    (Some(old), None) => format!("{old:>old_digits$} {:>new_digits$}{marker} ", ""),
                    (None, Some(new)) => format!("{:>old_digits$} {new:>new_digits$}{marker} ", ""),
                    (None, None) => unreachable!("displayed diff line has a source"),
                }
            } else {
                let digits = view.info.source_extents[usize::from(!before)]
                    .max(1)
                    .ilog10() as usize
                    + 1;
                format!("{:>digits$}{marker} ", index + 1)
            };
            frame.render_widget(
                Paragraph::new(label).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[usize::from(!before)].line(index),
            text_area,
            left,
        );
        paint_semantic_line(
            frame,
            source_text,
            semantic[usize::from(!before)],
            index,
            text_area,
            left,
        );
        if let Some(characters) = whitespace_characters {
            paint_whitespace(
                frame,
                source_text,
                text_area,
                left,
                characters,
                whitespace_scope,
                syntax[usize::from(!before)].string_spans(index),
                line.newline,
                true,
            );
        }
        if line.emphasize {
            let style = Style::default().bg(colors.character[usize::from(!before)]);
            for range in line.changes() {
                if !range.is_empty() {
                    paint_grapheme_range(frame, text_area, left, source_text, range.clone(), style);
                }
            }
        }
        if highlight_trailing_whitespace {
            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)
            };
            paint_trailing_whitespace(frame, &text, text_area, left);
        }
        if let Some(anchor) = selected_anchor {
            let side = match anchor.side {
                crate::review::Side::Before => Focus::Before,
                crate::review::Side::After => Focus::After,
            };
            if let Some(source_row) = view
                .review_row(side, display_row)
                .filter(|source_row| anchor.rows().contains(source_row))
            {
                let start = if source_row == anchor.start.row {
                    anchor.start.column
                } else {
                    0
                };
                let end = if source_row == anchor.end.row {
                    anchor.end.column
                } else {
                    usize::MAX
                };
                paint_grapheme_range(
                    frame,
                    text_area,
                    left,
                    source_text,
                    start..end,
                    Style::default().bg(Color::Magenta),
                );
            }
        }
    }
    if gutter > 0 {
        for comment in review_comments {
            let side = match comment.anchor.side {
                crate::review::Side::Before => Focus::Before,
                crate::review::Side::After => Focus::After,
            };
            let selected = selected_review == Some(comment.id);
            for (screen, display, _) in
                diff_screen_rows(view.info.display_len, top, content.height, wrapped)
            {
                let source = view.review_row(side, display);
                if wrapped.is_some_and(|rows| rows[screen].position.continuation != 0)
                    || !source.is_some_and(|row| comment.anchor.rows().contains(&row))
                {
                    continue;
                }
                let cell = &mut frame.buffer_mut()
                    [(content.x + gutter as u16 - 1, content.y + screen as u16)];
                if selected || cell.symbol() != "●" {
                    cell.set_symbol(if selected { "●" } else { "○" })
                        .set_fg(Color::Magenta);
                    if selected {
                        cell.modifier.insert(Modifier::BOLD);
                    }
                }
            }
        }
    }
    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) {
    draw_diagnostic_panel(frame, diagnostic, area, "Configuration error", None);
}

fn draw_diagnostic_panel(
    frame: &mut Frame,
    diagnostic: &StartupDiagnostic,
    area: Rect,
    title: &str,
    output: Option<&crate::editor::ShellOutput>,
) {
    let startup = output.is_none();
    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(if startup { Color::Red } else { Color::DarkGray }))
        .title(format!(" {} ", display_text(title)));
    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> = if let Some(output) = output.filter(|output| output.wrapping) {
        let width = usize::from(text_area.width).max(1);
        let mut cached = output.wrapped_lines.borrow_mut();
        if cached.0 != width {
            let mut cache = crate::wrap::WrapCache::default();
            cache.prepare((0, 0), width);
            cached.1.clear();
            for (row, line) in diagnostic.lines.iter().enumerate() {
                let segments = cache.segments(row, line);
                for (index, segment) in segments.iter().enumerate() {
                    // Output has no insertion caret: omit its extra empty continuation.
                    if index == 0 || segment.start != segment.end {
                        cached.1.push((row, *segment));
                    }
                }
            }
            cached.0 = width;
        }
        output.wrapped_rows.set(cached.1.len());
        cached
            .1
            .iter()
            .skip(diagnostic.top.min(cached.1.len().saturating_sub(1)))
            .take(usize::from(text_area.height))
            .map(|(row, segment)| {
                Line::from(visible_line(
                    &diagnostic.lines[*row],
                    segment.start,
                    (segment.end - segment.start).min(width),
                ))
            })
            .collect()
    } else {
        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(if startup {
            "Arrows scroll · Home reset · Enter/Esc continue"
        } else {
            "Arrows scroll · Home reset · Enter/Esc close"
        })
        .style(Style::default().fg(Color::DarkGray)),
        help_area,
    );
    if startup && 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],
    scope: [bool; 2],
    unwrapped: bool,
}

#[derive(Default)]
struct DiffWrapViewport {
    key: Option<(u64, usize, Option<u64>)>,
    view_mode: Option<ViewMode>,
    revision: u64,
    before: crate::wrap::WrapCache,
    after: crate::wrap::WrapCache,
    widths: [usize; 2],
    lefts: [usize; 2],
    heights: [usize; 2],
    visible_names: [Vec<Point>; 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 })
}

fn diff_source_len(diff: &DiffState, file: &ChangedFile, before: bool) -> usize {
    let stored = if before {
        file.before.len()
    } else {
        file.after.len()
    };
    let last = diff
        .rows
        .last()
        .and_then(|row| if before { row.before } else { row.after });
    stored.max(last.map_or(0, |row| row + 1))
}

fn diff_gutter(diff: &DiffState, file: &ChangedFile, width: usize, focus: Focus) -> usize {
    column_gutter(
        diff.view_mode == ViewMode::Unified,
        [
            diff_source_len(diff, file, true),
            diff_source_len(diff, file, false),
        ],
        width,
        focus,
    )
}

fn column_gutter(unified: bool, extents: [usize; 2], width: usize, focus: Focus) -> usize {
    let [old, new] = extents.map(|len| len.max(1).ilog10() as usize + 1);
    let gutter = if unified {
        old + new + 3
    } else {
        (if focus == Focus::Before { old } else { new }) + 2
    };
    if width > gutter { gutter } else { 0 }
}

fn diff_pane_text_width(diff: &DiffState, file: &ChangedFile, area: Rect, focus: Focus) -> usize {
    let width = usize::from(diff_inner(area).width);
    width.saturating_sub(diff_gutter(diff, file, width, focus))
}

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 !diff.word_wrap {
            return WrappedDiffRow {
                position,
                segments,
                final_segments,
                scope: [false; 2],
                unwrapped: true,
            };
        }
        if matches!(
            diff.display_rows.get(position.display),
            Some(DisplayRow::Line(_))
        ) {
            for (side, focus) in [Focus::Before, Focus::After].into_iter().enumerate() {
                let source = diff.display_source_row(focus, position.display);
                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,
            scope: [false; 2],
            unwrapped: false,
        }
    }

    fn height(&mut self, diff: &DiffState, file: &ChangedFile, display: usize) -> usize {
        if !diff.word_wrap {
            return 1;
        }
        if !matches!(diff.display_rows.get(display), Some(DisplayRow::Line(_))) {
            return 1;
        }
        let mut height = 1;
        for (side, focus) in [Focus::Before, Focus::After].into_iter().enumerate() {
            let source = diff.display_source_row(focus, display);
            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 declaration_visible(
        &self,
        diff: &DiffState,
        file: &ChangedFile,
        side: usize,
        name: Point,
    ) -> bool {
        let focus = if side == 0 {
            Focus::Before
        } else {
            Focus::After
        };
        let source = if side == 0 { &file.before } else { &file.after };
        let column = display_column(source.get(name.row).map_or("", String::as_str), name.column);
        self.rows.iter().take(self.heights[side]).any(|row| {
            if row.scope != [false; 2]
                || diff.display_source_row(focus, row.position.display) != Some(name.row)
            {
                return false;
            }
            if row.unwrapped {
                return true;
            }
            let Some(segment) = row.segments[side] else {
                return false;
            };
            let (left, right) = (segment.start, segment.end);
            left <= column && column < right
        })
    }

    fn fill(
        &mut self,
        diff: &DiffState,
        file: &ChangedFile,
        height: usize,
        syntax: &DiffSyntaxCache,
    ) {
        for names in &mut self.visible_names {
            names.clear();
        }
        // ponytail: reflow only this viewport; index visual rows if tall terminals make it hot.
        loop {
            self.rows.clear();
            if diff.display_rows.is_empty() {
                return;
            }
            let mut position = self.top;
            let mut sticky = [true; 2];
            while self.rows.len() < height {
                let contexts = syntax.scopes(diff, position.display);
                for mut scope in syntax.labels(diff, position, contexts, sticky) {
                    for side in 0..2 {
                        scope[side] &= !contexts[side].is_some_and(|context| {
                            self.visible_names[side].contains(&context.name)
                        });
                    }
                    if scope.iter().any(|side| *side) && self.rows.len() + 1 < height {
                        if self.rows.is_empty() {
                            // The sticky slot can still show the adjacent declaration as source.
                            let previous = self.step(diff, file, position, false);
                            let declaration = self.row(diff, file, previous);
                            let visible = |side: usize| {
                                let focus = if side == 0 {
                                    Focus::Before
                                } else {
                                    Focus::After
                                };
                                let Some(context) = contexts[side] else {
                                    return false;
                                };
                                if diff.display_source_row(focus, previous.display)
                                    != Some(context.name.row)
                                {
                                    return false;
                                }
                                let source = if side == 0 { &file.before } else { &file.after };
                                let prefix = &source[context.name.row][..context.name.column];
                                let column = display_column(prefix, usize::MAX);
                                if declaration.unwrapped {
                                    let pane = if diff.view_mode == ViewMode::Unified {
                                        usize::from(diff.focus != Focus::Before)
                                    } else {
                                        side
                                    };
                                    self.lefts[pane] <= column
                                        && column
                                            < self.lefts[pane].saturating_add(self.widths[pane])
                                } else {
                                    declaration.segments[side].is_some_and(|segment| {
                                        segment.start <= column && column < segment.end
                                    })
                                }
                            };
                            let restore = if diff.view_mode == ViewMode::Unified {
                                let side = usize::from(
                                    diff.display_focus(previous.display) != Some(Focus::Before),
                                );
                                scope[side] && visible(side)
                            } else {
                                (0..2).all(|side| !scope[side] || visible(side))
                            };
                            if previous != position && restore {
                                self.rows.push(declaration);
                                continue;
                            }
                        }
                        self.rows.push(WrappedDiffRow {
                            position,
                            segments: [None; 2],
                            final_segments: [false; 2],
                            scope,
                            unwrapped: false,
                        });
                    }
                }
                for (side, focus) in [Focus::Before, Focus::After].into_iter().enumerate() {
                    if diff.display_source_row(focus, position.display).is_some() {
                        sticky[side] = false;
                    }
                }
                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;
            }
            let mut changed = false;
            for index in 0..self.rows.len() {
                let row = self.rows[index];
                if row.scope == [false; 2] {
                    continue;
                }
                let contexts = syntax.scopes(diff, row.position.display);
                for side in 0..2 {
                    if let Some(context) = contexts[side]
                        && row.scope[side]
                        && !self.visible_names[side].contains(&context.name)
                        && self.declaration_visible(diff, file, side, context.name)
                    {
                        self.visible_names[side].push(context.name);
                        changed = true;
                    }
                }
            }
            if !changed {
                break;
            }
        }
    }

    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 = if diff.word_wrap {
            caret_segment(cache.segments(cursor.row, text), column)
        } else {
            0
        };
        Some(DiffWrapPosition {
            display,
            continuation,
        })
    }

    fn screen_row(&self, position: DiffWrapPosition) -> Option<usize> {
        self.rows
            .iter()
            .position(|row| row.scope == [false; 2] && row.position == position)
    }

    fn update(
        &mut self,
        diff: &DiffState,
        file: &ChangedFile,
        areas: [Rect; 2],
        caret: Option<(Focus, Cursor)>,
        anchor_row: Option<usize>,
        distance: Option<usize>,
        syntax: &DiffSyntaxCache,
    ) {
        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.view_mode != Some(diff.view_mode)
        {
            self.top = DiffWrapPosition {
                display: diff.top,
                continuation: 0,
            };
        }
        self.view_mode = Some(diff.view_mode);
        if self.key != key {
            self.key = key;
            self.revision = self
                .revision
                .checked_add(1)
                .expect("wrap revisions exhausted");
        }
        self.widths = [
            diff_pane_text_width(diff, file, areas[0], Focus::Before),
            diff_pane_text_width(diff, file, areas[1], Focus::After),
        ];
        self.heights = areas.map(|area| usize::from(diff_inner(area).height));
        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 active = usize::from(diff.focus == Focus::After || areas[0].height == 0);
        let height = usize::from(diff_inner(areas[active]).height);
        let paint_height =
            usize::from(diff_inner(areas[0]).height.max(diff_inner(areas[1]).height));
        self.fill(diff, file, paint_height, syntax);
        if let Some((focus, cursor)) = caret
            && let Some(position) = self.caret_position(diff, file, focus, cursor)
        {
            let margin = scroll_margin(height, distance);
            let row = self.screen_row(position).filter(|&row| row < height);
            let anchor = anchor_row.or_else(|| {
                if height == 0 {
                    None
                } else if margin == height / 2
                    || position < self.top
                    || row.is_some_and(|row| row < margin)
                {
                    Some(margin)
                } else if row.is_none_or(|row| row >= height - margin) {
                    Some(height - margin - 1)
                } else {
                    None
                }
            });
            if let Some(row) = anchor {
                self.top = position;
                let target = row.min(height.saturating_sub(1));
                // Skip only positions guaranteed to precede the target, even if every
                // potential label is shown. Each side can also add one sticky label.
                let mut upper_bound = 2;
                let mut candidate = position;
                loop {
                    let contexts = syntax.scopes(diff, candidate.display);
                    upper_bound += syntax
                        .labels(diff, candidate, contexts, [false; 2])
                        .into_iter()
                        .filter(|scope| scope[0] || scope[1])
                        .count();
                    if upper_bound >= target {
                        break;
                    }
                    self.top = candidate;
                    let previous = self.step(diff, file, candidate, false);
                    if previous == candidate {
                        break;
                    }
                    candidate = previous;
                    upper_bound += 1;
                }
                self.fill(diff, file, paint_height, syntax);
                while self
                    .screen_row(position)
                    .is_some_and(|screen| screen < target)
                {
                    let previous = self.step(diff, file, self.top, false);
                    if previous == self.top {
                        break;
                    }
                    let top = self.top;
                    self.top = previous;
                    self.fill(diff, file, paint_height, syntax);
                    if self
                        .screen_row(position)
                        .is_none_or(|screen| screen > target)
                    {
                        self.top = top;
                        self.fill(diff, file, paint_height, syntax);
                        break;
                    }
                }
            }
        }
    }
}

fn diff_screen_rows<'a>(
    display_len: usize,
    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)
                .filter(|row| row.scope == [false; 2])
                .map(|row| {
                    (
                        screen,
                        row.position.display,
                        (!row.unwrapped).then_some(row.segments),
                    )
                })
        } else {
            (top + screen < display_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 scopes<'a>(
        &'a self,
        diff: &DiffState,
        display: usize,
    ) -> [Option<crate::syntax::ScopeContext<'a>>; 2] {
        [Focus::Before, Focus::After].map(|focus| {
            let source = diff.display_source_row(focus, display)?;
            let syntax = if focus == Focus::Before {
                &self.before
            } else {
                &self.after
            };
            syntax.scope_at(source)
        })
    }

    fn labels(
        &self,
        diff: &DiffState,
        position: DiffWrapPosition,
        scopes: [Option<crate::syntax::ScopeContext<'_>>; 2],
        sticky: [bool; 2],
    ) -> [[bool; 2]; 2] {
        let show = [Focus::Before, Focus::After].map(|focus| {
            let side = usize::from(focus == Focus::After);
            if scopes[side].is_none() || (!sticky[side] && position.continuation > 0) {
                return false;
            }
            if sticky[side] {
                return true;
            }
            // Alignment holes do not end a scope; only an omitted excerpt resets it.
            let previous = (0..position.display)
                .rev()
                .take_while(|&display| {
                    !matches!(diff.display_rows[display], DisplayRow::Fold { .. })
                })
                .find_map(|display| diff.display_source_row(focus, display));
            let syntax = if side == 0 { &self.before } else { &self.after };
            scopes[side] != previous.and_then(|source| syntax.scope_at(source))
        });
        if diff.view_mode == ViewMode::Unified
            && scopes[0].map(|scope| scope.label) != scopes[1].map(|scope| scope.label)
        {
            [[show[0], false], [false, show[1]]]
        } else {
            [show, [false; 2]]
        }
    }

    fn update(
        &mut self,
        comparison_id: u64,
        file_index: usize,
        file: &ChangedFile,
        after: &[String],
        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_diff(
                &file.before,
                Some(file.old_path.as_deref().unwrap_or(&file.path)),
                self.before_revision,
                file.before_eof,
                Some(&self.before_rows),
            );
            self.after.update_diff(
                after,
                Some(&file.path),
                self.revision,
                file.after_eof,
                Some(&self.after_rows),
            );
        } else {
            self.before.update_diff(
                &file.before,
                Some(file.old_path.as_deref().unwrap_or(&file.path)),
                self.before_revision,
                file.before_eof,
                None,
            );
            self.after
                .update_diff(after, Some(&file.path), self.revision, file.after_eof, None);
        }
    }
}

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
    };
    for (_, display, _) in diff_screen_rows(diff.display_rows.len(), top, height, wrapped) {
        let source =
            diff.display_source_row(if before { Focus::Before } else { Focus::After }, display);
        if ranges
            .last()
            .is_some_and(|range| source.is_some_and(|source| range.contains(&source)))
        {
            continue;
        }
        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)>,
    input: Option<Rect>,
    notification: Option<Rect>,
    completion: Option<Rect>,
    hover: Option<(Rect, usize)>,
    hover_syntax: SyntaxCache,
    files: Option<(Rect, usize, usize)>,
    manual_files: Option<FileWheelOffset>,
    picker_scroll: PickerScroll,
    diff: Option<DiffGeometry>,
    diff_colors: DiffColors,
    diff_syntax: Option<DiffSyntaxCache>,
    previous_diff: Option<DiffGeometry>,
    diff_wrap: Option<DiffWrapViewport>,
}

struct PickerScroll {
    distance: Option<usize>,
    files: Option<PickerViewport>,
    completion: Option<PickerViewport>,
    palette: Option<PickerViewport>,
    revisions: Option<PickerViewport>,
}

impl Default for PickerScroll {
    fn default() -> Self {
        Self {
            distance: Some(0),
            files: None,
            completion: None,
            palette: None,
            revisions: None,
        }
    }
}

#[derive(Default)]
struct PickerViewport {
    key: u64,
    top: usize,
}

impl PickerViewport {
    fn follow(
        viewport: &mut Option<Self>,
        key: u64,
        selected: usize,
        height: usize,
        row_height: usize,
        distance: Option<usize>,
    ) -> usize {
        let viewport = viewport.get_or_insert_with(Self::default);
        if viewport.key != key {
            viewport.key = key;
            viewport.top = 0;
        }
        if height < row_height {
            return viewport.top;
        }
        let margin = scroll_margin(height, distance);
        let top = scroll_offset(
            viewport.top.saturating_mul(row_height),
            selected.saturating_mul(row_height),
            height,
            distance,
        );
        let first = selected.saturating_sub(margin.div_ceil(row_height));
        let last = selected
            .saturating_add(1)
            .saturating_sub((height - margin) / row_height);
        viewport.top = if margin == height / 2 || last > first {
            selected.saturating_sub((height / 2) / row_height)
        } else {
            top.div_ceil(row_height).clamp(last, first)
        };
        viewport.top
    }
}

fn file_picker_key(picker: &FilePicker) -> u64 {
    let mut key = std::collections::hash_map::DefaultHasher::new();
    (
        &picker.root,
        &picker.query,
        picker.presentation as u8,
        picker.view as u8,
        picker.viewport_revision(),
    )
        .hash(&mut key);
    key.finish()
}

struct FileWheelOffset {
    top: usize,
    root: std::path::PathBuf,
    query: String,
    state: (usize, u64),
}

impl FileWheelOffset {
    fn state(picker: &FilePicker) -> (usize, u64) {
        (picker.selected, file_picker_key(picker))
    }

    fn matches(&self, picker: &FilePicker, key: u64) -> bool {
        self.state == (picker.selected, key)
            && 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.picker_scroll.files = None;
        }
        self.hover = None;
        self.caret = None;
        self.input = None;
        self.notification = None;
        self.completion = None;
        self.files = None;
        self.previous_diff = self.diff.take();
    }

    fn follow_files(&mut self) {
        self.manual_files = None;
    }

    fn file_top(&mut self, picker: &FilePicker, panel: Rect, height: usize) -> usize {
        let key = FileWheelOffset::state(picker).1;
        if self
            .manual_files
            .as_ref()
            .is_some_and(|offset| !offset.matches(picker, key))
        {
            self.manual_files = None;
        }
        let count = picker.entries().len();
        let following = PickerViewport::follow(
            &mut self.picker_scroll.files,
            key,
            picker.selected.min(count.saturating_sub(1)),
            height,
            1,
            self.picker_scroll.distance,
        );
        let top = self.manual_files.as_mut().map_or(following, |offset| {
            offset.top = offset.top.min(count.saturating_sub(height.max(1)));
            offset.top
        });
        if let Some(viewport) = &mut self.picker_scroll.files {
            viewport.top = 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;
        };
        if session.editor().command_output().is_some() {
            let input = match kind {
                MouseEventKind::ScrollUp => Input::Up,
                MouseEventKind::ScrollDown => Input::Down,
                MouseEventKind::ScrollLeft => Input::Left,
                MouseEventKind::ScrollRight => Input::Right,
                _ => unreachable!(),
            };
            for _ in 0..3 {
                session.handle(input.clone());
            }
            return true;
        }
        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 self.input.is_some_and(|area| area.contains(position))
            || self
                .notification
                .is_some_and(|area| area.contains(position))
        {
            return true;
        }
        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 {
                let key = file_picker_key(picker);
                if self
                    .manual_files
                    .as_ref()
                    .is_some_and(|offset| !offset.matches(picker, key))
                {
                    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: (picker.selected, key),
                });
                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,
    panels: &mut WheelPanels,
) -> 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 mut key = std::collections::hash_map::DefaultHasher::new();
    (completion.items.as_ptr(), completion.items.len()).hash(&mut key);
    let first = PickerViewport::follow(
        &mut panels.picker_scroll.completion,
        key.finish(),
        selected,
        usize::from(height),
        1,
        panels.picker_scroll.distance,
    );
    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(40) 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], &BTreeSet<usize>)>,
) {
    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 status = changed.map(|file| file.status).or(entry.status);
                let old_path = changed
                    .and_then(|file| file.old_path.as_deref())
                    .or(entry.old_path);
                let mut spans = Vec::with_capacity(8);
                let reviewed = changed_files.is_some_and(|(_, reviewed)| {
                    if entry.is_dir {
                        if entry.expanded {
                            return false;
                        }
                        let mut descendants =
                            picker.descendant_catalog_indices(entry.path).peekable();
                        descendants.peek().is_some()
                            && descendants.all(|index| reviewed.contains(&index))
                    } else {
                        changed.is_some()
                            && entry
                                .catalog_index
                                .is_some_and(|index| reviewed.contains(&index))
                    }
                });
                if changed_files.is_none() {
                    spans.push(Span::raw(if selected { ">" } else { " " }));
                    spans.push(Span::raw(" "));
                }
                spans.push(Span::raw(if picker.view == FileView::Tree {
                    " ".repeat(entry.depth * 2)
                } else {
                    String::new()
                }));
                if changed_files.is_some() {
                    spans.push(Span::styled(
                        if reviewed { "✓" } else { " " },
                        Style::default().fg(Color::Green),
                    ));
                    spans.push(Span::raw(" "));
                }
                if picker.is_conflicted(entry.path) {
                    spans.push(Span::styled("C", Style::default().fg(Color::Yellow)));
                    spans.push(Span::raw(" "));
                } else if let Some(status) = status {
                    let color = match status {
                        FileStatus::Added => Color::Green,
                        FileStatus::Removed => Color::Red,
                        FileStatus::Modified => Color::Yellow,
                        FileStatus::Renamed => Color::Cyan,
                    };
                    spans.push(Span::styled(
                        diff_status(status),
                        Style::default().fg(color),
                    ));
                    spans.push(Span::raw(" "));
                } else if changed_files.is_none() {
                    spans.push(Span::raw("  "));
                }
                if status == Some(FileStatus::Renamed)
                    && let Some(old_path) = old_path
                {
                    spans.push(Span::raw(display_text(&old_path.to_string_lossy())));
                    spans.push(Span::raw(" -> "));
                    spans.push(Span::raw(display_text(
                        &changed
                            .map_or(entry.path, |file| file.path.as_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,
    panels: &mut WheelPanels,
) {
    if area.width == 0 || area.height == 0 {
        return;
    }
    let panel = if palette.buffers {
        floating_panel(area)
    } else {
        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);
        panel
    };
    frame.render_widget(Clear, panel);
    let bordered = panel.height >= 4 && panel.width >= 4;
    let padding =
        u16::from(palette.buffers && panel.width.saturating_sub(2 * u16::from(bordered)) >= 3);
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .border_style(if palette.buffers {
            Style::default().fg(Color::Cyan)
        } else {
            Style::default()
        })
        .padding(ratatui::widgets::Padding::horizontal(padding))
        .title(if palette.buffers {
            " Buffers ".into()
        } else {
            format!(" Commands · {mode} ")
        });
    let content = if bordered {
        block.inner(panel)
    } else {
        panel.inner(ratatui::layout::Margin::new(padding, 0))
    };
    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.saturating_sub(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() {
        panels.picker_scroll.palette = None;
        frame.render_widget(
            Paragraph::new(if palette.buffers {
                "No matching buffers"
            } else {
                "No matching commands"
            }),
            results_area,
        );
    } else if results_area.height > 0 {
        let row_height = if palette.buffers {
            1
        } else {
            usize::from(results_area.height >= 2) + 1
        };
        let count = usize::from(results_area.height) / row_height;
        let mut key = std::collections::hash_map::DefaultHasher::new();
        (&palette.query, palette.buffers).hash(&mut key);
        (palette.entries.as_ptr(), palette.entries.len()).hash(&mut key);
        let first = PickerViewport::follow(
            &mut panels.picker_scroll.palette,
            key.finish(),
            palette.selected.min(palette.entries.len() - 1),
            usize::from(results_area.height),
            row_height,
            panels.picker_scroll.distance,
        );
        let id_width = palette
            .entries
            .last()
            .and_then(|entry| entry.buffer.as_ref())
            .map_or(1, |buffer| buffer.id.ilog10() as usize + 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);
            }
            if let Some(buffer) = &entry.buffer {
                lines.push(
                    Line::from(vec![
                        Span::raw(if index == palette.selected {
                            "> "
                        } else {
                            "  "
                        }),
                        Span::styled(
                            if buffer.active { "* " } else { "  " },
                            Style::default().fg(Color::Cyan),
                        ),
                        Span::raw(format!("{:>id_width$}", buffer.id)),
                        Span::styled(
                            if buffer.dirty { "+ " } else { "  " },
                            Style::default().fg(Color::Yellow),
                        ),
                        Span::raw(display_path(std::path::Path::new(&entry.label))),
                    ])
                    .style(style),
                );
                continue;
            }
            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(if palette.buffers {
            format!("{navigation_hint} · Enter open · Esc/^P cancel · ^U clear")
        } else {
            format!("{mode} · {navigation_hint} · Enter accept · Esc/Ctrl+p cancel")
        })
        .style(if palette.buffers {
            Style::default().fg(Color::DarkGray)
        } else {
            Style::default()
        }),
        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)]
#[path = "../tests/unit/tui.rs"]
mod tests;