helix-mods/helix-term/src/ui/picker.rs

use crate::{
    alt,
    compositor::{self, Component, Compositor, Context, Event, EventResult},
    ctrl,
    job::Callback,
    key, shift,
    ui::{
        self,
        document::{render_document, LineDecoration, LinePos, TextRenderer},
        fuzzy_match::FuzzyQuery,
        EditorView,
    },
};
use futures_util::{future::BoxFuture, FutureExt};
use tui::{
    buffer::Buffer as Surface,
    layout::Constraint,
    text::{Span, Spans},
    widgets::{Block, BorderType, Borders, Cell, Table},
};

use fuzzy_matcher::skim::SkimMatcherV2 as Matcher;
use tui::widgets::Widget;

use std::cmp::{self, Ordering};
use std::{collections::HashMap, io::Read, path::PathBuf};

use crate::ui::{Prompt, PromptEvent};
use helix_core::{
    movement::Direction, text_annotations::TextAnnotations,
    unicode::segmentation::UnicodeSegmentation, Position, Syntax,
};
use helix_view::{
    editor::Action,
    graphics::{CursorKind, Margin, Modifier, Rect},
    theme::Style,
    view::ViewPosition,
    Document, DocumentId, Editor,
};

use super::{menu::Item, overlay::Overlay};

pub const MIN_AREA_WIDTH_FOR_PREVIEW: u16 = 72;
/// Biggest file size to preview in bytes
pub const MAX_FILE_SIZE_FOR_PREVIEW: u64 = 10 * 1024 * 1024;

#[derive(PartialEq, Eq, Hash)]
pub enum PathOrId {
    Id(DocumentId),
    Path(PathBuf),
}

impl PathOrId {
    fn get_canonicalized(self) -> std::io::Result<Self> {
        use PathOrId::*;
        Ok(match self {
            Path(path) => Path(helix_core::path::get_canonicalized_path(&path)?),
            Id(id) => Id(id),
        })
    }
}

impl From<PathBuf> for PathOrId {
    fn from(v: PathBuf) -> Self {
        Self::Path(v)
    }
}

impl From<DocumentId> for PathOrId {
    fn from(v: DocumentId) -> Self {
        Self::Id(v)
    }
}

type FileCallback<T> = Box<dyn Fn(&Editor, &T) -> Option<FileLocation>>;

/// File path and range of lines (used to align and highlight lines)
pub type FileLocation = (PathOrId, Option<(usize, usize)>);

pub enum CachedPreview {
    Document(Box<Document>),
    Binary,
    LargeFile,
    NotFound,
}

// We don't store this enum in the cache so as to avoid lifetime constraints
// from borrowing a document already opened in the editor.
pub enum Preview<'picker, 'editor> {
    Cached(&'picker CachedPreview),
    EditorDocument(&'editor Document),
}

impl Preview<'_, '_> {
    fn document(&self) -> Option<&Document> {
        match self {
            Preview::EditorDocument(doc) => Some(doc),
            Preview::Cached(CachedPreview::Document(doc)) => Some(doc),
            _ => None,
        }
    }

    /// Alternate text to show for the preview.
    fn placeholder(&self) -> &str {
        match *self {
            Self::EditorDocument(_) => "<File preview>",
            Self::Cached(preview) => match preview {
                CachedPreview::Document(_) => "<File preview>",
                CachedPreview::Binary => "<Binary file>",
                CachedPreview::LargeFile => "<File too large to preview>",
                CachedPreview::NotFound => "<File not found>",
            },
        }
    }
}

pub struct FilePicker<T: Item> {
    options: Vec<T>,
    editor_data: T::Data,
    // filter: String,
    matcher: Box<Matcher>,
    matches: Vec<PickerMatch>,

    /// Current height of the completions box
    completion_height: u16,

    cursor: usize,
    // pattern: String,
    prompt: Prompt,
    previous_pattern: (String, FuzzyQuery),
    /// Whether to show the preview panel (default true)
    show_preview: bool,
    /// Constraints for tabular formatting
    widths: Vec<Constraint>,

    callback_fn: PickerCallback<T>,

    picker: Picker<T>,
    pub truncate_start: bool,
    /// Caches paths to documents
    preview_cache: HashMap<PathBuf, CachedPreview>,
    read_buffer: Vec<u8>,
    /// Given an item in the picker, return the file path and line number to display.
    file_fn: FileCallback<T>,
}

impl<T: Item + 'static> FilePicker<T> {
    pub fn new(
        options: Vec<T>,
        editor_data: T::Data,
        callback_fn: impl Fn(&mut Context, &T, Action) + 'static,
        preview_fn: impl Fn(&Editor, &T) -> Option<FileLocation> + 'static,
    ) -> Self {
        let prompt = Prompt::new(
            "".into(),
            None,
            ui::completers::none,
            |_editor: &mut Context, _pattern: &str, _event: PromptEvent| {},
        );

        let mut picker = Self {
            options,
            editor_data,
            matcher: Box::default(),
            matches: Vec::new(),
            cursor: 0,
            prompt,
            previous_pattern: (String::new(), FuzzyQuery::default()),
            truncate_start: true,
            show_preview: true,
            callback_fn: Box::new(callback_fn),
            completion_height: 0,
            widths: Vec::new(),
            preview_cache: HashMap::new(),
            read_buffer: Vec::with_capacity(1024),
            file_fn: Box::new(preview_fn),

            picker: unimplemented!(),
        };

        picker.calculate_column_widths();

        // scoring on empty input
        // TODO: just reuse score()
        picker
            .matches
            .extend(picker.options.iter().enumerate().map(|(index, option)| {
                let text = option.filter_text(&picker.editor_data);
                PickerMatch {
                    index,
                    score: 0,
                    len: text.chars().count(),
                }
            }));

        picker
    }

    pub fn truncate_start(mut self, truncate_start: bool) -> Self {
        self.truncate_start = truncate_start;
        self.picker.truncate_start = truncate_start;
        self
    }

    pub fn set_options(&mut self, new_options: Vec<T>) {
        self.options = new_options;
        self.cursor = 0;
        self.force_score();
        self.calculate_column_widths();
    }

    /// Calculate the width constraints using the maximum widths of each column
    /// for the current options.
    fn calculate_column_widths(&mut self) {
        let n = self
            .options
            .first()
            .map(|option| option.format(&self.editor_data).cells.len())
            .unwrap_or_default();
        let max_lens = self.options.iter().fold(vec![0; n], |mut acc, option| {
            let row = option.format(&self.editor_data);
            // maintain max for each column
            for (acc, cell) in acc.iter_mut().zip(row.cells.iter()) {
                let width = cell.content.width();
                if width > *acc {
                    *acc = width;
                }
            }
            acc
        });
        self.widths = max_lens
            .into_iter()
            .map(|len| Constraint::Length(len as u16))
            .collect();
    }

    pub fn score(&mut self) {
        let pattern = self.prompt.line();

        if pattern == &self.previous_pattern.0 {
            return;
        }

        let (query, is_refined) = self
            .previous_pattern
            .1
            .refine(pattern, &self.previous_pattern.0);

        if pattern.is_empty() {
            // Fast path for no pattern.
            self.matches.clear();
            self.matches
                .extend(self.options.iter().enumerate().map(|(index, option)| {
                    let text = option.filter_text(&self.editor_data);
                    PickerMatch {
                        index,
                        score: 0,
                        len: text.chars().count(),
                    }
                }));
        } else if is_refined {
            // optimization: if the pattern is a more specific version of the previous one
            // then we can score the filtered set.
            self.matches.retain_mut(|pmatch| {
                let option = &self.options[pmatch.index];
                let text = option.sort_text(&self.editor_data);

                match query.fuzzy_match(&text, &self.matcher) {
                    Some(s) => {
                        // Update the score
                        pmatch.score = s;
                        true
                    }
                    None => false,
                }
            });

            self.matches.sort_unstable();
        } else {
            self.force_score();
        }

        // reset cursor position
        self.cursor = 0;
        let pattern = self.prompt.line();
        self.previous_pattern.0.clone_from(pattern);
        self.previous_pattern.1 = query;
    }

    pub fn force_score(&mut self) {
        let pattern = self.prompt.line();

        let query = FuzzyQuery::new(pattern);
        self.matches.clear();
        self.matches.extend(
            self.options
                .iter()
                .enumerate()
                .filter_map(|(index, option)| {
                    let text = option.filter_text(&self.editor_data);

                    query
                        .fuzzy_match(&text, &self.matcher)
                        .map(|score| PickerMatch {
                            index,
                            score,
                            len: text.chars().count(),
                        })
                }),
        );

        self.matches.sort_unstable();
    }

    /// Move the cursor by a number of lines, either down (`Forward`) or up (`Backward`)
    pub fn move_by(&mut self, amount: usize, direction: Direction) {
        let len = self.matches.len();

        if len == 0 {
            // No results, can't move.
            return;
        }

        match direction {
            Direction::Forward => {
                self.cursor = self.cursor.saturating_add(amount) % len;
            }
            Direction::Backward => {
                self.cursor = self.cursor.saturating_add(len).saturating_sub(amount) % len;
            }
        }
    }

    /// Move the cursor down by exactly one page. After the last page comes the first page.
    pub fn page_up(&mut self) {
        self.move_by(self.completion_height as usize, Direction::Backward);
    }

    /// Move the cursor up by exactly one page. After the first page comes the last page.
    pub fn page_down(&mut self) {
        self.move_by(self.completion_height as usize, Direction::Forward);
    }

    /// Move the cursor to the first entry
    pub fn to_start(&mut self) {
        self.cursor = 0;
    }

    /// Move the cursor to the last entry
    pub fn to_end(&mut self) {
        self.cursor = self.matches.len().saturating_sub(1);
    }

    pub fn selection(&self) -> Option<&T> {
        self.matches
            .get(self.cursor)
            .map(|pmatch| &self.options[pmatch.index])
    }

    pub fn toggle_preview(&mut self) {
        self.show_preview = !self.show_preview;
    }

    fn prompt_handle_event(&mut self, event: &Event, cx: &mut Context) -> EventResult {
        if let EventResult::Consumed(_) = self.prompt.handle_event(event, cx) {
            // TODO: recalculate only if pattern changed
            self.score();
        }
        EventResult::Consumed(None)
    }

    fn current_file(&self, editor: &Editor) -> Option<FileLocation> {
        self.picker
            .selection()
            .and_then(|current| (self.file_fn)(editor, current))
            .and_then(|(path_or_id, line)| path_or_id.get_canonicalized().ok().zip(Some(line)))
    }

    /// Get (cached) preview for a given path. If a document corresponding
    /// to the path is already open in the editor, it is used instead.
    fn get_preview<'picker, 'editor>(
        &'picker mut self,
        path_or_id: PathOrId,
        editor: &'editor Editor,
    ) -> Preview<'picker, 'editor> {
        match path_or_id {
            PathOrId::Path(path) => {
                let path = &path;
                if let Some(doc) = editor.document_by_path(path) {
                    return Preview::EditorDocument(doc);
                }

                if self.preview_cache.contains_key(path) {
                    return Preview::Cached(&self.preview_cache[path]);
                }

                let data = std::fs::File::open(path).and_then(|file| {
                    let metadata = file.metadata()?;
                    // Read up to 1kb to detect the content type
                    let n = file.take(1024).read_to_end(&mut self.read_buffer)?;
                    let content_type = content_inspector::inspect(&self.read_buffer[..n]);
                    self.read_buffer.clear();
                    Ok((metadata, content_type))
                });
                let preview = data
                    .map(
                        |(metadata, content_type)| match (metadata.len(), content_type) {
                            (_, content_inspector::ContentType::BINARY) => CachedPreview::Binary,
                            (size, _) if size > MAX_FILE_SIZE_FOR_PREVIEW => {
                                CachedPreview::LargeFile
                            }
                            _ => {
                                // TODO: enable syntax highlighting; blocked by async rendering
                                Document::open(path, None, None, editor.config.clone())
                                    .map(|doc| CachedPreview::Document(Box::new(doc)))
                                    .unwrap_or(CachedPreview::NotFound)
                            }
                        },
                    )
                    .unwrap_or(CachedPreview::NotFound);
                self.preview_cache.insert(path.to_owned(), preview);
                Preview::Cached(&self.preview_cache[path])
            }
            PathOrId::Id(id) => {
                let doc = editor.documents.get(&id).unwrap();
                Preview::EditorDocument(doc)
            }
        }
    }

    fn handle_idle_timeout(&mut self, cx: &mut Context) -> EventResult {
        let Some((current_file, _)) = self.current_file(cx.editor) else {
            return EventResult::Consumed(None)
        };

        // Try to find a document in the cache
        let doc = match &current_file {
            PathOrId::Id(doc_id) => doc_mut!(cx.editor, doc_id),
            PathOrId::Path(path) => match self.preview_cache.get_mut(path) {
                Some(CachedPreview::Document(ref mut doc)) => doc,
                _ => return EventResult::Consumed(None),
            },
        };

        let mut callback: Option<compositor::Callback> = None;

        // Then attempt to highlight it if it has no language set
        if doc.language_config().is_none() {
            if let Some(language_config) = doc.detect_language_config(&cx.editor.syn_loader) {
                doc.language = Some(language_config.clone());
                let text = doc.text().clone();
                let loader = cx.editor.syn_loader.clone();
                let job = tokio::task::spawn_blocking(move || {
                    let syntax = language_config
                        .highlight_config(&loader.scopes())
                        .and_then(|highlight_config| Syntax::new(&text, highlight_config, loader));
                    let callback = move |editor: &mut Editor, compositor: &mut Compositor| {
                        let Some(syntax) = syntax else {
                            log::info!("highlighting picker item failed");
                            return
                        };
                        let Some(Overlay { content: picker, .. }) = compositor.find::<Overlay<Self>>() else {
                            log::info!("picker closed before syntax highlighting finished");
                            return
                        };
                        // Try to find a document in the cache
                        let doc = match current_file {
                            PathOrId::Id(doc_id) => doc_mut!(editor, &doc_id),
                            PathOrId::Path(path) => match picker.preview_cache.get_mut(&path) {
                                Some(CachedPreview::Document(ref mut doc)) => doc,
                                _ => return,
                            },
                        };
                        doc.syntax = Some(syntax);
                    };
                    Callback::EditorCompositor(Box::new(callback))
                });
                let tmp: compositor::Callback = Box::new(move |_, ctx| {
                    ctx.jobs
                        .callback(job.map(|res| res.map_err(anyhow::Error::from)))
                });
                callback = Some(Box::new(tmp))
            }
        }

        // QUESTION: do we want to compute inlay hints in pickers too ? Probably not for now
        // but it could be interesting in the future

        EventResult::Consumed(callback)
    }

    fn render_picker(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        let text_style = cx.editor.theme.get("ui.text");
        let selected = cx.editor.theme.get("ui.text.focus");
        let highlight_style = cx.editor.theme.get("special").add_modifier(Modifier::BOLD);

        // -- Render the frame:
        // clear area
        let background = cx.editor.theme.get("ui.background");
        surface.clear_with(area, background);

        // don't like this but the lifetime sucks
        let block = Block::default().borders(Borders::ALL);

        // calculate the inner area inside the box
        let inner = block.inner(area);

        block.render(area, surface);

        // -- Render the input bar:

        let area = inner.clip_left(1).with_height(1);

        let count = format!("{}/{}", self.matches.len(), self.options.len());
        surface.set_stringn(
            (area.x + area.width).saturating_sub(count.len() as u16 + 1),
            area.y,
            &count,
            (count.len()).min(area.width as usize),
            text_style,
        );

        self.prompt.render(area, surface, cx);

        // -- Separator
        let sep_style = cx.editor.theme.get("ui.background.separator");
        let borders = BorderType::line_symbols(BorderType::Plain);
        for x in inner.left()..inner.right() {
            if let Some(cell) = surface.get_mut(x, inner.y + 1) {
                cell.set_symbol(borders.horizontal).set_style(sep_style);
            }
        }

        // -- Render the contents:
        // subtract area of prompt from top
        let inner = inner.clip_top(2);

        let rows = inner.height;
        let offset = self.cursor - (self.cursor % std::cmp::max(1, rows as usize));
        let cursor = self.cursor.saturating_sub(offset);

        let options = self
            .matches
            .iter()
            .skip(offset)
            .take(rows as usize)
            .map(|pmatch| &self.options[pmatch.index])
            .map(|option| option.format(&self.editor_data))
            .map(|mut row| {
                const TEMP_CELL_SEP: &str = " ";

                let line = row.cell_text().fold(String::new(), |mut s, frag| {
                    s.push_str(&frag);
                    s.push_str(TEMP_CELL_SEP);
                    s
                });

                // Items are filtered by using the text returned by menu::Item::filter_text
                // but we do highlighting here using the text in Row and therefore there
                // might be inconsistencies. This is the best we can do since only the
                // text in Row is displayed to the end user.
                let (_score, highlights) = FuzzyQuery::new(self.prompt.line())
                    .fuzzy_indices(&line, &self.matcher)
                    .unwrap_or_default();

                let highlight_byte_ranges: Vec<_> = line
                    .char_indices()
                    .enumerate()
                    .filter_map(|(char_idx, (byte_offset, ch))| {
                        highlights
                            .contains(&char_idx)
                            .then(|| byte_offset..byte_offset + ch.len_utf8())
                    })
                    .collect();

                // The starting byte index of the current (iterating) cell
                let mut cell_start_byte_offset = 0;
                for cell in row.cells.iter_mut() {
                    let spans = match cell.content.lines.get(0) {
                        Some(s) => s,
                        None => {
                            cell_start_byte_offset += TEMP_CELL_SEP.len();
                            continue;
                        }
                    };

                    let mut cell_len = 0;

                    let graphemes_with_style: Vec<_> = spans
                        .0
                        .iter()
                        .flat_map(|span| {
                            span.content
                                .grapheme_indices(true)
                                .zip(std::iter::repeat(span.style))
                        })
                        .map(|((grapheme_byte_offset, grapheme), style)| {
                            cell_len += grapheme.len();
                            let start = cell_start_byte_offset;

                            let grapheme_byte_range =
                                grapheme_byte_offset..grapheme_byte_offset + grapheme.len();

                            if highlight_byte_ranges.iter().any(|hl_rng| {
                                hl_rng.start >= start + grapheme_byte_range.start
                                    && hl_rng.end <= start + grapheme_byte_range.end
                            }) {
                                (grapheme, style.patch(highlight_style))
                            } else {
                                (grapheme, style)
                            }
                        })
                        .collect();

                    let mut span_list: Vec<(String, Style)> = Vec::new();
                    for (grapheme, style) in graphemes_with_style {
                        if span_list.last().map(|(_, sty)| sty) == Some(&style) {
                            let (string, _) = span_list.last_mut().unwrap();
                            string.push_str(grapheme);
                        } else {
                            span_list.push((String::from(grapheme), style))
                        }
                    }

                    let spans: Vec<Span> = span_list
                        .into_iter()
                        .map(|(string, style)| Span::styled(string, style))
                        .collect();
                    let spans: Spans = spans.into();
                    *cell = Cell::from(spans);

                    cell_start_byte_offset += cell_len + TEMP_CELL_SEP.len();
                }

                row
            });

        let table = Table::new(options)
            .style(text_style)
            .highlight_style(selected)
            .highlight_symbol(" > ")
            .column_spacing(1)
            .widths(&self.widths);

        use tui::widgets::TableState;

        table.render_table(
            inner,
            surface,
            &mut TableState {
                offset: 0,
                selected: Some(cursor),
            },
            self.truncate_start,
        );
    }

    fn render_preview(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        // -- Render the frame:
        // clear area
        let background = cx.editor.theme.get("ui.background");
        let text = cx.editor.theme.get("ui.text");
        surface.clear_with(area, background);

        // don't like this but the lifetime sucks
        let block = Block::default().borders(Borders::ALL);

        // calculate the inner area inside the box
        let inner = block.inner(area);
        // 1 column gap on either side
        let margin = Margin::horizontal(1);
        let inner = inner.inner(&margin);
        block.render(area, surface);

        if let Some((path, range)) = self.current_file(cx.editor) {
            let preview = self.get_preview(path, cx.editor);
            let doc = match preview.document() {
                Some(doc) => doc,
                None => {
                    let alt_text = preview.placeholder();
                    let x = inner.x + inner.width.saturating_sub(alt_text.len() as u16) / 2;
                    let y = inner.y + inner.height / 2;
                    surface.set_stringn(x, y, alt_text, inner.width as usize, text);
                    return;
                }
            };

            // align to middle
            let first_line = range
                .map(|(start, end)| {
                    let height = end.saturating_sub(start) + 1;
                    let middle = start + (height.saturating_sub(1) / 2);
                    middle.saturating_sub(inner.height as usize / 2).min(start)
                })
                .unwrap_or(0);

            let offset = ViewPosition {
                anchor: doc.text().line_to_char(first_line),
                horizontal_offset: 0,
                vertical_offset: 0,
            };

            let mut highlights = EditorView::doc_syntax_highlights(
                doc,
                offset.anchor,
                area.height,
                &cx.editor.theme,
            );
            for spans in EditorView::doc_diagnostics_highlights(doc, &cx.editor.theme) {
                if spans.is_empty() {
                    continue;
                }
                highlights = Box::new(helix_core::syntax::merge(highlights, spans));
            }
            let mut decorations: Vec<Box<dyn LineDecoration>> = Vec::new();

            if let Some((start, end)) = range {
                let style = cx
                    .editor
                    .theme
                    .try_get("ui.highlight")
                    .unwrap_or_else(|| cx.editor.theme.get("ui.selection"));
                let draw_highlight = move |renderer: &mut TextRenderer, pos: LinePos| {
                    if (start..=end).contains(&pos.doc_line) {
                        let area = Rect::new(
                            renderer.viewport.x,
                            renderer.viewport.y + pos.visual_line,
                            renderer.viewport.width,
                            1,
                        );
                        renderer.surface.set_style(area, style)
                    }
                };
                decorations.push(Box::new(draw_highlight))
            }

            render_document(
                surface,
                inner,
                doc,
                offset,
                // TODO: compute text annotations asynchronously here (like inlay hints)
                &TextAnnotations::default(),
                highlights,
                &cx.editor.theme,
                &mut decorations,
                &mut [],
            );
        }
    }

    fn handle_event(&mut self, event: &Event, ctx: &mut Context) -> EventResult {
        if let Event::IdleTimeout = event {
            return self.handle_idle_timeout(ctx);
        }
        // TODO: keybinds for scrolling preview

        let key_event = match event {
            Event::Key(event) => *event,
            Event::Paste(..) => return self.prompt_handle_event(event, ctx),
            Event::Resize(..) => return EventResult::Consumed(None),
            _ => return EventResult::Ignored(None),
        };

        let close_fn =
            EventResult::Consumed(Some(Box::new(|compositor: &mut Compositor, _ctx| {
                // remove the layer
                compositor.last_picker = compositor.pop();
            })));

        // So that idle timeout retriggers
        ctx.editor.reset_idle_timer();

        match key_event {
            shift!(Tab) | key!(Up) | ctrl!('p') => {
                self.move_by(1, Direction::Backward);
            }
            key!(Tab) | key!(Down) | ctrl!('n') => {
                self.move_by(1, Direction::Forward);
            }
            key!(PageDown) | ctrl!('d') => {
                self.page_down();
            }
            key!(PageUp) | ctrl!('u') => {
                self.page_up();
            }
            key!(Home) => {
                self.to_start();
            }
            key!(End) => {
                self.to_end();
            }
            key!(Esc) | ctrl!('c') => {
                return close_fn;
            }
            alt!(Enter) => {
                if let Some(option) = self.selection() {
                    (self.callback_fn)(ctx, option, Action::Load);
                }
            }
            key!(Enter) => {
                if let Some(option) = self.selection() {
                    (self.callback_fn)(ctx, option, Action::Replace);
                }
                return close_fn;
            }
            ctrl!('s') => {
                if let Some(option) = self.selection() {
                    (self.callback_fn)(ctx, option, Action::HorizontalSplit);
                }
                return close_fn;
            }
            ctrl!('v') => {
                if let Some(option) = self.selection() {
                    (self.callback_fn)(ctx, option, Action::VerticalSplit);
                }
                return close_fn;
            }
            ctrl!('t') => {
                self.toggle_preview();
            }
            _ => {
                self.prompt_handle_event(event, ctx);
            }
        }

        EventResult::Consumed(None)
    }

    fn cursor(&self, area: Rect, editor: &Editor) -> (Option<Position>, CursorKind) {
        let block = Block::default().borders(Borders::ALL);
        // calculate the inner area inside the box
        let inner = block.inner(area);

        // prompt area
        let area = inner.clip_left(1).with_height(1);

        self.prompt.cursor(area, editor)
    }

    fn required_size(&mut self, (width, height): (u16, u16)) -> Option<(u16, u16)> {
        self.completion_height = height.saturating_sub(4);
        Some((width, height))
    }

    fn id(&self) -> Option<&'static str> {
        Some("file-picker")
    }
}

impl<T: Item + 'static> Component for FilePicker<T> {
    fn render(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        // +---------+ +---------+
        // |prompt   | |preview  |
        // +---------+ |         |
        // |picker   | |         |
        // |         | |         |
        // +---------+ +---------+

        let render_preview = self.picker.show_preview && area.width > MIN_AREA_WIDTH_FOR_PREVIEW;

        let picker_width = if render_preview {
            area.width / 2
        } else {
            area.width
        };

        let picker_area = area.with_width(picker_width);
        self.render_picker(picker_area, surface, cx);

        if render_preview {
            let preview_area = area.clip_left(picker_width);
            self.render_preview(preview_area, surface, cx);
        }
    }
}

#[derive(PartialEq, Eq, Debug)]
struct PickerMatch {
    score: i64,
    index: usize,
    len: usize,
}

impl PickerMatch {
    fn key(&self) -> impl Ord {
        (cmp::Reverse(self.score), self.len, self.index)
    }
}

impl PartialOrd for PickerMatch {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for PickerMatch {
    fn cmp(&self, other: &Self) -> Ordering {
        self.key().cmp(&other.key())
    }
}

type PickerCallback<T> = Box<dyn Fn(&mut Context, &T, Action)>;

pub struct Picker<T: Item> {
    options: Vec<T>,
    editor_data: T::Data,
    // filter: String,
    matcher: Box<Matcher>,
    matches: Vec<PickerMatch>,

    /// Current height of the completions box
    completion_height: u16,

    cursor: usize,
    // pattern: String,
    prompt: Prompt,
    previous_pattern: (String, FuzzyQuery),
    /// Whether to truncate the start (default true)
    pub truncate_start: bool,
    /// Whether to show the preview panel (default true)
    show_preview: bool,
    /// Constraints for tabular formatting
    widths: Vec<Constraint>,

    callback_fn: PickerCallback<T>,
}

impl<T: Item> Picker<T> {
    pub fn new(
        options: Vec<T>,
        editor_data: T::Data,
        callback_fn: impl Fn(&mut Context, &T, Action) + 'static,
    ) -> Self {
        unimplemented!()
    }

    pub fn set_options(&mut self, new_options: Vec<T>) {
        unimplemented!()
    }

    pub fn score(&mut self) {
        unimplemented!()
    }

    pub fn force_score(&mut self) {
        unimplemented!()
    }

    /// Move the cursor by a number of lines, either down (`Forward`) or up (`Backward`)
    pub fn move_by(&mut self, amount: usize, direction: Direction) {
        unimplemented!()
    }

    /// Move the cursor down by exactly one page. After the last page comes the first page.
    pub fn page_up(&mut self) {
        unimplemented!()
    }

    /// Move the cursor up by exactly one page. After the first page comes the last page.
    pub fn page_down(&mut self) {
        unimplemented!()
    }

    /// Move the cursor to the first entry
    pub fn to_start(&mut self) {
        unimplemented!()
    }

    /// Move the cursor to the last entry
    pub fn to_end(&mut self) {
        unimplemented!()
    }

    pub fn selection(&self) -> Option<&T> {
        unimplemented!()
    }

    pub fn toggle_preview(&mut self) {
        unimplemented!()
    }

    fn prompt_handle_event(&mut self, event: &Event, cx: &mut Context) -> EventResult {
        unimplemented!()
    }
}

// process:
// - read all the files into a list, maxed out at a large value
// - on input change:
//  - score all the names in relation to input

impl<T: Item + 'static> Component for Picker<T> {
    fn required_size(&mut self, viewport: (u16, u16)) -> Option<(u16, u16)> {
        unimplemented!()
    }

    fn handle_event(&mut self, event: &Event, cx: &mut Context) -> EventResult {
        unimplemented!()
    }

    fn render(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        unimplemented!()
    }

    fn cursor(&self, area: Rect, editor: &Editor) -> (Option<Position>, CursorKind) {
        unimplemented!()
    }
}

/// Returns a new list of options to replace the contents of the picker
/// when called with the current picker query,
pub type DynQueryCallback<T> =
    Box<dyn Fn(String, &mut Editor) -> BoxFuture<'static, anyhow::Result<Vec<T>>>>;

/// A picker that updates its contents via a callback whenever the
/// query string changes. Useful for live grep, workspace symbols, etc.
pub struct DynamicPicker<T: ui::menu::Item + Send> {
    file_picker: FilePicker<T>,
    query_callback: DynQueryCallback<T>,
    query: String,
}

impl<T: ui::menu::Item + Send> DynamicPicker<T> {
    pub const ID: &'static str = "dynamic-picker";

    pub fn new(file_picker: FilePicker<T>, query_callback: DynQueryCallback<T>) -> Self {
        Self {
            file_picker,
            query_callback,
            query: String::new(),
        }
    }
}

impl<T: Item + Send + 'static> Component for DynamicPicker<T> {
    fn render(&mut self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        self.file_picker.render(area, surface, cx);
    }

    fn handle_event(&mut self, event: &Event, cx: &mut Context) -> EventResult {
        let event_result = self.file_picker.handle_event(event, cx);
        let current_query = self.file_picker.picker.prompt.line();

        if !matches!(event, Event::IdleTimeout) || self.query == *current_query {
            return event_result;
        }

        self.query.clone_from(current_query);

        let new_options = (self.query_callback)(current_query.to_owned(), cx.editor);

        cx.jobs.callback(async move {
            let new_options = new_options.await?;
            let callback = Callback::EditorCompositor(Box::new(move |editor, compositor| {
                // Wrapping of pickers in overlay is done outside the picker code,
                // so this is fragile and will break if wrapped in some other widget.
                let picker = match compositor.find_id::<Overlay<DynamicPicker<T>>>(Self::ID) {
                    Some(overlay) => &mut overlay.content.file_picker.picker,
                    None => return,
                };
                picker.set_options(new_options);
                editor.reset_idle_timer();
            }));
            anyhow::Ok(callback)
        });
        EventResult::Consumed(None)
    }

    fn cursor(&self, area: Rect, ctx: &Editor) -> (Option<Position>, CursorKind) {
        self.file_picker.cursor(area, ctx)
    }

    fn required_size(&mut self, viewport: (u16, u16)) -> Option<(u16, u16)> {
        self.file_picker.required_size(viewport)
    }

    fn id(&self) -> Option<&'static str> {
        Some(Self::ID)
    }
}