vamp/src/tui.rs

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

use crossterm::{
    cursor::Show,
    event::{
        self, DisableBracketedPaste, DisableMouseCapture, EnableBracketedPaste, 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, Rect},
    style::{Color, Modifier, Style},
    text::Line,
    widgets::{Block, Borders, Clear, Paragraph},
};
use unicode_segmentation::UnicodeSegmentation;
use unicode_width::UnicodeWidthStr;

use crate::{
    editor::{Cursor, Editor, Hover, Input, Mode, Palette, Selection, StartupDiagnostic},
    files::{DockSide, FilePicker, FilePresentation, FileView},
    plugin::{
        Diagnostic, DiagnosticSeverity, SemanticToken, SemanticTokenKind, SemanticTokenModifier,
    },
    session::EditorSession,
    syntax::{SyntaxCache, SyntaxKind},
};

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

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

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

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

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

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

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

#[derive(Default)]
struct DocumentViewport {
    geometry: Option<(usize, Rect)>,
    manual: Option<ManualViewport>,
}

struct ManualViewport {
    buffer_id: usize,
    revision: u64,
    caret_reveal_revision: u64,
    mode: Mode,
    cursor: Cursor,
    carets: Vec<Cursor>,
    selections: Vec<Selection>,
}

#[derive(Default)]
struct BufferViewports {
    offsets: BTreeMap<usize, (usize, usize)>,
    syntax: BTreeMap<usize, SyntaxCache>,
    document: DocumentViewport,
    panels: WheelPanels,
}

impl BufferViewports {
    fn draw(&mut self, frame: &mut Frame, editor: &Editor) {
        self.offsets.retain(|id, _| editor.has_buffer(*id));
        self.syntax.retain(|id, _| editor.has_buffer(*id));
        let (top, left) = self.offsets.entry(editor.buffer_id()).or_default();
        let syntax = self.syntax.entry(editor.buffer_id()).or_default();
        draw(
            frame,
            editor,
            top,
            left,
            syntax,
            &mut self.document,
            &mut self.panels,
        );
    }

    fn scroll(&mut self, session: &mut EditorSession, mouse: MouseEvent) -> bool {
        if !matches!(
            mouse.kind,
            MouseEventKind::ScrollUp | MouseEventKind::ScrollDown
        ) {
            return false;
        }
        if self.panels.scroll(session, mouse) {
            return true;
        }
        let editor = session.editor();
        if editor.palette().is_some() || editor.startup_diagnostic().is_some() {
            return true;
        }
        let Some((buffer_id, viewport)) = self.document.geometry else {
            return false;
        };
        if buffer_id != editor.buffer_id()
            || viewport.width == 0
            || viewport.height == 0
            || !viewport.contains((mouse.column, mouse.row).into())
        {
            return false;
        }
        let (top, _) = self.offsets.entry(buffer_id).or_default();
        let last_page = editor
            .lines()
            .len()
            .saturating_sub(usize::from(viewport.height));
        *top = match mouse.kind {
            MouseEventKind::ScrollUp => top.saturating_sub(3),
            MouseEventKind::ScrollDown => top.saturating_add(3),
            _ => unreachable!(),
        }
        .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 draw_frame<W: io::Write>(
    terminal: &mut Terminal<CrosstermBackend<Vec<u8>>>,
    output: &mut W,
    render: impl FnOnce(&mut Frame),
) -> io::Result<()> {
    // Do not suspend the terminal's presentation while computing the next frame.
    terminal.backend_mut().writer_mut().clear();
    crossterm::queue!(terminal.backend_mut(), BeginSynchronizedUpdate)?;
    // Terminals without synchronized updates still hide the painting cursor.
    let result = terminal
        .hide_cursor()
        .and_then(|()| terminal.draw(render).map(|_| ()));
    let finish = execute!(terminal.backend_mut(), EndSynchronizedUpdate);
    result.and(finish)?;
    output.write_all(terminal.backend().writer())?;
    output.flush()
}

/// Renders session state and translates terminal input; the session owns plugin
/// execution and retirement, so the adapter needs no lifecycle callback.
pub fn run(session: &mut EditorSession) -> io::Result<()> {
    TerminalSession::run(|| {
        let mut output: Stdout = io::stdout();
        let mut terminal = Terminal::new(CrosstermBackend::new(Vec::new()))?;
        let mut viewports = BufferViewports::default();
        let mut redraw = true;
        let mut pending = None;
        while !session.editor().should_quit() {
            redraw |= session.poll();
            if redraw {
                draw_frame(&mut terminal, &mut output, |frame| {
                    viewports.draw(frame, session.editor())
                })?;
                redraw = false;
            }
            let input = if let Some(input) = pending.take() {
                input
            } else {
                if !event::poll(Duration::from_millis(25))? {
                    continue;
                }
                event::read()?
            };
            match input {
                Event::Key(key) if key.kind != KeyEventKind::Release => {
                    if let Some(input) = translate(key) {
                        viewports.panels.follow_files();
                        session.handle(input);
                        redraw = true;
                    }
                }
                Event::Paste(text) => {
                    viewports.panels.follow_files();
                    session.handle(Input::Paste(text));
                    redraw = true;
                }
                Event::Mouse(mouse) => {
                    let (changed, following) = viewports.scroll_ready(session, mouse, || {
                        if event::poll(Duration::ZERO)? {
                            event::read().map(Some)
                        } else {
                            Ok(None)
                        }
                    })?;
                    redraw |= changed;
                    pending = following;
                }
                Event::Resize(_, _) => redraw = true,
                _ => {}
            }
        }
        Ok(())
    })
}

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

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

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

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

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

fn draw(
    frame: &mut Frame,
    editor: &Editor,
    top: &mut usize,
    left: &mut usize,
    syntax: &mut SyntaxCache,
    document: &mut DocumentViewport,
    panels: &mut WheelPanels,
) {
    panels.begin_frame();
    document.geometry = None;
    syntax.update(editor.lines(), editor.path(), editor.text_revision());
    let area = frame.area();
    if area.width == 0 || area.height == 0 {
        return;
    }
    let prompting = matches!(editor.mode(), Mode::Command | Mode::Search);
    let dock_focused = editor
        .file_picker()
        .is_some_and(|picker| picker.focused && picker.presentation == FilePresentation::Docked);
    let [workspace, status_area, prompt_area] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(u16::from(area.height >= 3)),
        Constraint::Length(u16::from(area.height >= 2 || (prompting && !dock_focused))),
    ])
    .areas(area);
    let (viewport, dock) = match editor.file_picker() {
        Some(picker) if picker.presentation == FilePresentation::Docked => {
            dock_layout(workspace, editor.file_explorer_side(), picker.focused)
        }
        _ => (workspace, None),
    };
    let digits = editor.lines().len().ilog10() as usize + 1;
    let gutter_width = (digits + 1) as u16;
    let [gutter, viewport] = Layout::horizontal([
        Constraint::Length(if viewport.width > gutter_width {
            gutter_width
        } else {
            0
        }),
        Constraint::Fill(1),
    ])
    .areas(viewport);
    let height = usize::from(viewport.height);
    let width = usize::from(viewport.width);
    let cursor = editor.cursor();
    let carets = editor.carets();
    let selections = editor.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,
        ),
    ));
    *top = (*top).min(editor.lines().len().saturating_sub(height));
    if height > 0 && width > 0 {
        if document.manual.is_none() {
            if cursor.row < *top {
                *top = cursor.row;
            } else if cursor.row >= top.saturating_add(height) {
                *top = cursor.row + 1 - height;
            }
            let column = display_column(&editor.lines()[cursor.row], cursor.column);
            if column < *left {
                *left = column;
            } else if column >= left.saturating_add(width) {
                *left = column + 1 - width;
            }
        }
        if gutter.width > 0 {
            let numbers: Vec<Line> = (*top..top.saturating_add(height).min(editor.lines().len()))
                .map(|row| {
                    let style = if row == cursor.row {
                        Style::default()
                            .fg(Color::Cyan)
                            .add_modifier(Modifier::BOLD)
                    } else {
                        Style::default().fg(Color::DarkGray)
                    };
                    let style = match editor
                        .diagnostics()
                        .filter(|diagnostic| diagnostic_on_row(diagnostic, row))
                        .map(|diagnostic| diagnostic_severity(diagnostic.severity))
                        .min_by_key(|(severity, _, _)| *severity)
                    {
                        Some((_, color, _)) => style.fg(color),
                        None => style,
                    };
                    let number = if row == cursor.row {
                        row + 1
                    } else {
                        row.abs_diff(cursor.row)
                    };
                    Line::styled(format!("{number:>digits$} "), style)
                })
                .collect();
            frame.render_widget(Paragraph::new(numbers), gutter);
        }
        let lines: Vec<Line> = editor
            .lines()
            .iter()
            .skip(*top)
            .take(height)
            .map(|line| Line::from(visible_line(line, *left, width)))
            .collect();
        frame.render_widget(Paragraph::new(lines), viewport);
        let buffer = frame.buffer_mut();
        let semantic = editor.semantic_tokens();
        let mut semantic_index = semantic.partition_point(|token| token.start.row < *top);
        for (row, line) in editor.lines().iter().enumerate().skip(*top).take(height) {
            let spans = syntax.line(row);
            while semantic_index < semantic.len() && semantic[semantic_index].start.row < row {
                semantic_index += 1;
            }
            if spans.is_empty()
                && semantic
                    .get(semantic_index)
                    .is_none_or(|token| token.start.row != row)
            {
                continue;
            }
            let mut span_index = 0;
            let mut token_style = None;
            let mut column = 0;
            let right = left.saturating_add(width);
            for (index, (byte, grapheme)) in line.grapheme_indices(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 span_index < spans.len() && spans[span_index].end_byte <= byte {
                    span_index += 1;
                }
                while semantic_index < semantic.len()
                    && semantic[semantic_index].start.row == row
                    && semantic[semantic_index].end.column <= index
                {
                    semantic_index += 1;
                    token_style = None;
                }
                let style = semantic
                    .get(semantic_index)
                    .filter(|token| token.start.row == row && token.start.column <= index)
                    .map(|token| *token_style.get_or_insert_with(|| semantic_style(token)))
                    .or_else(|| {
                        spans
                            .get(span_index)
                            .filter(|span| span.start_byte <= byte)
                            .map(|span| syntax_style(span.kind))
                    });
                if let Some(style) = style
                    && end > *left
                    && (grapheme == "\t" || (column >= *left && end <= right))
                {
                    let y = viewport.y + (row - *top) as u16;
                    for cell in column.max(*left)..end.min(right) {
                        buffer[(viewport.x + (cell - *left) as u16, y)].set_style(style);
                    }
                }
                column = end;
            }
        }
        for severity in [
            DiagnosticSeverity::Hint,
            DiagnosticSeverity::Information,
            DiagnosticSeverity::Warning,
            DiagnosticSeverity::Error,
        ] {
            let style = Style::default()
                .underline_color(diagnostic_severity(severity).1)
                .add_modifier(Modifier::UNDERLINED);
            for diagnostic in editor
                .diagnostics()
                .filter(|item| item.severity == severity)
            {
                let first = diagnostic.start.row.max(*top);
                let last = diagnostic.end.row.min(top.saturating_add(height - 1));
                for row in first..=last {
                    if !diagnostic_on_row(diagnostic, row) {
                        continue;
                    }
                    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 line = &editor.lines()[row];
                    let y = viewport.y + (row - *top) as u16;
                    let right = left.saturating_add(width);
                    let mut column = 0;
                    let mut grapheme_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 index >= start
                            && index < end
                            && (grapheme == "\t" || (column >= *left && next <= right))
                        {
                            for cell in column.max(*left)..next.min(right) {
                                frame.buffer_mut()[(viewport.x + (cell - *left) as u16, y)]
                                    .set_style(style);
                            }
                        }
                        column = next;
                        grapheme_count = index + 1;
                        if column >= right {
                            break;
                        }
                    }
                    if start <= grapheme_count
                        && end > grapheme_count
                        && column >= *left
                        && column < right
                    {
                        frame.buffer_mut()[(viewport.x + (column - *left) as u16, y)]
                            .set_style(style);
                    }
                }
            }
        }
        if let Some(found) = editor.search_match()
            && found.start.row >= *top
            && found.start.row < top.saturating_add(height)
        {
            let line = &editor.lines()[found.start.row];
            let start = display_column(line, found.start.column).max(*left);
            let end = display_column(line, found.end_column).min(left.saturating_add(width));
            let y = viewport.y + (found.start.row - *top) as u16;
            let style = Style::default().fg(Color::Black).bg(Color::Yellow);
            let buffer = frame.buffer_mut();
            for column in start..end {
                buffer[(viewport.x + (column - *left) as u16, y)].set_style(style);
            }
        }
        let selection_style = Style::default().fg(Color::White).bg(Color::Blue);
        for rows in editor.linewise_rows() {
            let first = (*rows.start()).max(*top);
            let last = (*rows.end()).min(top.saturating_add(height - 1));
            for row in first..=last {
                let end = display_column(&editor.lines()[row], usize::MAX)
                    .saturating_add(1)
                    .min(left.saturating_add(width));
                let y = viewport.y + (row - *top) as u16;
                for column in *left..end {
                    frame.buffer_mut()[(viewport.x + (column - *left) as u16, y)]
                        .set_style(selection_style);
                }
            }
        }
        for selection in selections.iter().filter(|_| !editor.visual_linewise()) {
            let first = selection.start.row.max(*top);
            let last = selection.end.row.min(top.saturating_add(height - 1));
            let style = Style::default().fg(Color::White).bg(Color::Blue);
            for row in first..=last {
                let line = &editor.lines()[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) + 1
                };
                let start = start.max(*left);
                let end = end.min(left.saturating_add(width));
                let y = viewport.y + (row - *top) as u16;
                let buffer = frame.buffer_mut();
                for column in start..end {
                    buffer[(viewport.x + (column - *left) as u16, y)].set_style(style);
                }
            }
        }
        for caret in carets.iter().filter(|caret| **caret != cursor) {
            if caret.row < *top || caret.row >= top.saturating_add(height) {
                continue;
            }
            let column = display_column(&editor.lines()[caret.row], caret.column);
            if column >= *left && column < left.saturating_add(width) {
                frame.buffer_mut()[(
                    viewport.x + (column - *left) as u16,
                    viewport.y + (caret.row - *top) as u16,
                )]
                    .set_style(Style::default().fg(Color::Black).bg(Color::Magenta));
            }
        }
    }
    let path = editor
        .path()
        .map(|p| p.to_string_lossy().into_owned())
        .unwrap_or_else(|| "[No Name]".into());
    let path: String = path
        .chars()
        .map(|c| if c.is_control() { '�' } else { c })
        .collect();
    let mut status = if editor.visual_linewise() {
        " VISUAL LINE".into()
    } else {
        format!(" {}", editor.mode())
    };
    if let Some(sequence) = editor.leader_pending() {
        write!(status, "  leader: {sequence}").unwrap();
    }
    if editor.g_pending() {
        status.push_str("  g");
    }
    if editor.buffer_count() > 1 {
        write!(
            status,
            "  [buffer {}/{}]",
            editor.buffer_id(),
            editor.buffer_count()
        )
        .unwrap();
    }
    let mut diagnostic_counts = [0; 4];
    for diagnostic in editor.diagnostics() {
        diagnostic_counts[diagnostic_severity(diagnostic.severity).0] += 1;
    }
    for (label, count) in ["E", "W", "I", "H"].into_iter().zip(diagnostic_counts) {
        if count > 0 {
            write!(status, "  {label}:{count}").unwrap();
        }
    }
    write!(
        status,
        "  {}{}  {}:{}",
        path,
        if editor.dirty() { " [+]" } else { "" },
        cursor.row + 1,
        cursor.column + 1,
    )
    .unwrap();
    if editor.selection_count() > 1 {
        write!(status, "  {} selections", editor.selection_count()).unwrap();
    }
    if let Some(count) = editor.count() {
        write!(status, "  count: {count}").unwrap();
    }
    if let Some(error) = syntax.error() {
        write!(status, "  syntax: {error}").unwrap();
    } else if let Some(language) = syntax.language() {
        write!(status, "  {language}").unwrap();
    }
    frame.render_widget(
        Paragraph::new(status).style(Style::default().fg(Color::Black).bg(Color::Cyan)),
        status_area,
    );
    if prompting && prompt_area.height > 0 && prompt_area.width > 0 {
        let prefix = if editor.mode() == Mode::Search {
            '/'
        } else {
            ':'
        };
        let command = format!("{prefix}{}", editor.command_line());
        let command_width = display_column(&command, usize::MAX);
        let prompt_width = usize::from(prompt_area.width);
        let offset = command_width.saturating_sub(prompt_width.saturating_sub(1));
        frame.render_widget(
            Paragraph::new(visible_line(&command, offset, prompt_width)),
            prompt_area,
        );
        if !editor.file_picker().is_some_and(|picker| picker.focused) {
            frame.set_cursor_position((
                prompt_area.x + (command_width - offset) as u16,
                prompt_area.y,
            ));
        }
    } else {
        let message = if let Some(diagnostic) = editor.diagnostic_at_cursor() {
            let (_, _, label) = diagnostic_severity(diagnostic.severity);
            let diagnostic = display_text(&diagnostic.message);
            Cow::Owned(if editor.message().is_empty() {
                format!("{label}: {diagnostic}")
            } else {
                format!("{} | {label}: {diagnostic}", editor.message())
            })
        } else {
            Cow::Borrowed(editor.message())
        };
        frame.render_widget(Paragraph::new(message), prompt_area);
        if height > 0 && width > 0 && !editor.file_picker().is_some_and(|picker| picker.focused) {
            let column = display_column(&editor.lines()[cursor.row], cursor.column);
            if cursor.row >= *top
                && cursor.row < top.saturating_add(height)
                && column >= *left
                && column < left.saturating_add(width)
            {
                frame.set_cursor_position((
                    viewport.x + (column - *left) as u16,
                    viewport.y + (cursor.row - *top) as u16,
                ));
            }
        }
    }
    if let Some(picker) = editor.file_picker() {
        if 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);
        } else if let Some(panel) = dock {
            draw_file_list(frame, picker, panel, editor.file_navigation_hint(), panels);
        }
    }
    if let Some(palette) = editor.palette() {
        draw_palette(
            frame,
            palette,
            editor.mode(),
            editor.selection_navigation_hint(),
        );
    }
    if let Some(hover) = editor.hover() {
        draw_hover(frame, hover, viewport, panels);
    }
    if let Some(diagnostic) = editor.startup_diagnostic() {
        draw_startup_diagnostic(frame, diagnostic, area);
    }
}

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

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

#[derive(Default)]
struct WheelPanels {
    hover: Option<(Rect, usize)>,
    hover_syntax: SyntaxCache,
    files: Option<(Rect, usize, usize)>,
    manual_files: Option<FileWheelOffset>,
}

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

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

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

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

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

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

    fn scroll(&mut self, session: &mut EditorSession, mouse: MouseEvent) -> bool {
        let down = match mouse.kind {
            MouseEventKind::ScrollDown => true,
            MouseEventKind::ScrollUp => false,
            _ => return false,
        };
        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 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;
        }
        if let Some(picker) = editor.file_picker()
            && let Some((panel, height, drawn_top)) = self.files
            && panel.contains(position)
        {
            if height > 0 {
                if self
                    .manual_files
                    .as_ref()
                    .is_some_and(|offset| !offset.matches(picker))
                {
                    self.manual_files = None;
                }
                let offset = self.manual_files.get_or_insert_with(|| FileWheelOffset {
                    top: drawn_top,
                    root: picker.root.clone(),
                    query: picker.query.clone(),
                    state: FileWheelOffset::state(picker),
                });
                offset.top = if down {
                    offset.top.saturating_add(3)
                } else {
                    offset.top.saturating_sub(3)
                }
                .min(picker.entries().len().saturating_sub(height));
            }
            return true;
        }
        false
    }
}

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

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

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

fn draw_file_list(
    frame: &mut Frame,
    picker: &FilePicker,
    panel: Rect,
    navigation_hint: &str,
    panels: &mut WheelPanels,
) {
    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;
    let show_error = picker.error.is_some() && content.height >= 2;
    let show_help = content.height >= 5 + u16::from(show_error);
    let [query_area, root_area, error_area, results_area, help_area] = Layout::vertical([
        Constraint::Length(1),
        Constraint::Length(u16::from(show_root)),
        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 show_root {
        frame.render_widget(
            Paragraph::new(display_text(&picker.root.to_string_lossy()))
                .style(Style::default().fg(Color::DarkGray)),
            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 label = match picker.view {
                    FileView::List => {
                        format!("{} {}", if selected { ">" } else { " " }, entry.label)
                    }
                    FileView::Tree => format!(
                        "{} {:indent$}{}{}",
                        if selected { ">" } else { " " },
                        "",
                        entry.label,
                        if entry.is_dir { "/" } else { "" },
                        indent = entry.depth * 2,
                    ),
                };
                Line::styled(label, 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,
            ));
        }
    }
    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, mode: Mode, navigation_hint: &str) {
    let area = frame.area();
    if area.width == 0 || area.height == 0 {
        return;
    }
    let [_, column, _] = Layout::horizontal([
        Constraint::Fill(1),
        Constraint::Length(area.width.min(100)),
        Constraint::Fill(1),
    ])
    .areas(area);
    let [_, panel, _] = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(area.height.min(16)),
        Constraint::Fill(1),
    ])
    .areas(column);
    frame.render_widget(Clear, panel);
    let bordered = panel.height >= 4 && panel.width >= 4;
    let block = Block::default()
        .borders(if bordered {
            Borders::ALL
        } else {
            Borders::NONE
        })
        .title(format!(" Commands · {mode} "));
    let content = if bordered { block.inner(panel) } else { panel };
    if bordered {
        frame.render_widget(block, panel);
    }
    let [query_area, results_area, help_area] = Layout::vertical([
        Constraint::Length(1),
        Constraint::Fill(1),
        Constraint::Length(u16::from(content.height >= 4)),
    ])
    .areas(content);
    let query = format!("> {}", palette.query);
    let query_width = display_column(&query, usize::MAX);
    let width = usize::from(query_area.width);
    let offset = query_width.saturating_sub(width - 1);
    frame.render_widget(
        Paragraph::new(visible_line(&query, offset, width))
            .style(Style::default().fg(Color::Yellow)),
        query_area,
    );
    frame.set_cursor_position((query_area.x + (query_width - offset) as u16, query_area.y));
    if palette.entries.is_empty() {
        frame.render_widget(Paragraph::new("No matching commands"), results_area);
    } else if results_area.height > 0 {
        let row_height = usize::from(results_area.height >= 2) + 1;
        let count = usize::from(results_area.height) / row_height;
        let first = palette.selected.saturating_sub(count - 1);
        let mut lines = Vec::with_capacity(count * row_height);
        for (index, entry) in palette.entries.iter().enumerate().skip(first).take(count) {
            let mut style = Style::default();
            if !entry.enabled {
                style = style.add_modifier(Modifier::DIM);
            }
            if index == palette.selected {
                style = style.bg(Color::Blue).add_modifier(Modifier::BOLD);
            }
            let bindings = if entry.bindings.is_empty() {
                "unbound".into()
            } else {
                entry.bindings.join(", ")
            };
            let modes = entry
                .modes
                .iter()
                .map(ToString::to_string)
                .collect::<Vec<_>>()
                .join("/");
            let metadata = format!("{} | {bindings} | {modes}", entry.owner);
            let label = format!(
                "{} {} ({})",
                if index == palette.selected { ">" } else { " " },
                entry.label,
                entry.name
            );
            if row_height == 2 {
                lines.push(Line::from(label).style(style));
                lines.push(Line::from(format!("  {metadata}")).style(style));
            } else {
                lines.push(Line::from(format!("{label} | {metadata}")).style(style));
            }
        }
        frame.render_widget(Paragraph::new(lines), results_area);
    }
    frame.render_widget(
        Paragraph::new(format!(
            "{mode} · {navigation_hint} · Enter accept · Esc/Ctrl+p cancel"
        )),
        help_area,
    );
}

fn 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)]
mod tests {
    use super::*;
    use std::{
        fs,
        path::PathBuf,
        sync::atomic::{AtomicUsize, Ordering},
    };

    struct Directory(PathBuf);

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

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

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

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

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

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

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

    #[test]
    fn hover_scroll_renders_whole_graphemes_in_tiny_workspace() {
        let mut editor = Editor::open(None, vec![]).unwrap();
        editor.show_hover("x界e\u{301}👩‍🚀z\nlast".into()).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(6, 1)).unwrap();
        let mut syntax = SyntaxCache::new();
        let (mut top, mut left) = (0, 0);
        for _ in 0..2 {
            editor.handle(Input::Right);
        }
        let rendered = terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert_eq!(rendered.buffer[(2, 0)].symbol(), "e\u{301}");
        assert_eq!(rendered.buffer[(3, 0)].symbol(), "👩‍🚀");
        assert_eq!(rendered.buffer[(5, 0)].symbol(), "z");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(2, 0)
        );
        assert_eq!((top, left), (0, 0));
        editor.handle(Input::Down);
        editor.handle(Input::Home);
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).ends_with("last"));
        for (width, height) in [(1, 1), (2, 2), (3, 3), (4, 4)] {
            let mut terminal =
                Terminal::new(ratatui::backend::TestBackend::new(width, height)).unwrap();
            terminal
                .draw(|frame| {
                    draw(
                        frame,
                        &editor,
                        &mut top,
                        &mut left,
                        &mut syntax,
                        &mut DocumentViewport::default(),
                        &mut WheelPanels::default(),
                    )
                })
                .unwrap();
        }
        assert_eq!(editor.cursor(), crate::editor::Cursor::default());
        assert_eq!(editor.lines(), &[""]);
    }

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

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

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

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

        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('!'));
        assert_eq!(editor.mode(), Mode::Insert);
        terminal
            .draw(|frame| viewports.draw(frame, &editor))
            .unwrap();
        assert_eq!(editor.diagnostics().count(), 0);
        assert!(!screen_text(&terminal).contains("E:1"));
        assert!(
            !terminal.backend().buffer()[(4, 0)]
                .modifier
                .contains(Modifier::UNDERLINED)
        );
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    #[test]
    fn manually_scrolled_tree_does_not_place_cursor_or_highlight_offscreen_selection() {
        let directory = Directory::new();
        for index in 0..12 {
            directory.file(&format!("file-{index:02}"), "");
        }
        let mut picker = FilePicker::scan(
            directory.0.clone(),
            FilePresentation::Docked,
            FileView::Tree,
        )
        .unwrap();
        picker.selected = 11;
        let mut panels = WheelPanels {
            manual_files: Some(FileWheelOffset {
                top: 0,
                root: picker.root.clone(),
                query: picker.query.clone(),
                state: FileWheelOffset::state(&picker),
            }),
            ..WheelPanels::default()
        };
        let area = Rect::new(3, 2, 40, 6);
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(60, 12)).unwrap();
        terminal
            .draw(|frame| {
                frame.set_cursor_position((59, 11));
                draw_file_list(frame, &picker, area, "", &mut panels);
            })
            .unwrap();
        let text = screen_text(&terminal);
        assert!(text.contains("file-00"), "{text}");
        assert!(!text.contains("file-11"), "{text}");
        assert_eq!(
            terminal.get_cursor_position().unwrap(),
            ratatui::layout::Position::new(59, 11)
        );
        for y in area.y..area.bottom() {
            for x in area.x..area.right() {
                assert_ne!(terminal.backend().buffer()[(x, y)].bg, Color::Blue);
            }
        }
        picker.navigate(false);
        terminal
            .draw(|frame| draw_file_list(frame, &picker, area, "", &mut panels))
            .unwrap();
        assert!(panels.manual_files.is_none());
        assert!(screen_text(&terminal).contains("> file-10"));
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    #[test]
    fn pending_leader_is_visible_before_long_paths_and_unknown_keys_do_not_edit() {
        let directory = Directory::new();
        let path = directory.file(&"long-path-".repeat(12), "keep");
        let mut editor = Editor::open(Some(path), vec![]).unwrap();
        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(40, 6)).unwrap();
        let (mut top, mut left) = (0, 0);
        let mut syntax = SyntaxCache::new();
        editor.handle(Input::Char(' '));
        editor.handle(Input::Char('b'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(screen_text(&terminal).contains("leader: Space b"));
        editor.handle(Input::Char('x'));
        terminal
            .draw(|frame| {
                draw(
                    frame,
                    &editor,
                    &mut top,
                    &mut left,
                    &mut syntax,
                    &mut DocumentViewport::default(),
                    &mut WheelPanels::default(),
                )
            })
            .unwrap();
        assert!(!screen_text(&terminal).contains("leader:"));
        assert_eq!(editor.lines(), &["keep"]);
        assert_eq!(editor.cursor(), crate::editor::Cursor::default());
        assert_eq!(editor.mode(), Mode::Normal);
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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