helix/helix-term/src/ui/editor.rs

use crate::commands;
use crate::compositor::{Component, Compositor, Context, EventResult};
use crate::keymap::{self, Keymaps};
use crate::ui::text_color;

use helix_core::{
    indent::TAB_WIDTH,
    syntax::{self, HighlightEvent},
    Position, Range, State,
};
use helix_view::{document::Mode, Document, Editor, Theme, View};
use std::borrow::Cow;

use crossterm::{
    cursor,
    event::{read, Event, EventStream, KeyCode, KeyEvent, KeyModifiers},
};
use tui::{
    backend::CrosstermBackend,
    buffer::Buffer as Surface,
    layout::Rect,
    style::{Color, Modifier, Style},
};

pub struct EditorView {
    keymap: Keymaps,
    on_next_key: Option<Box<dyn FnOnce(&mut commands::Context, KeyEvent)>>,
}

const OFFSET: u16 = 7; // 1 diagnostic + 5 linenr + 1 gutter

impl EditorView {
    pub fn new() -> Self {
        Self {
            keymap: keymap::default(),
            on_next_key: None,
        }
    }
    pub fn render_view(
        &self,
        view: &View,
        viewport: Rect,
        surface: &mut Surface,
        theme: &Theme,
        is_focused: bool,
    ) {
        let area = Rect::new(
            viewport.x + OFFSET,
            viewport.y,
            viewport.width - OFFSET,
            viewport.height.saturating_sub(1),
        ); // - 1 for statusline
        self.render_buffer(view, area, surface, theme, is_focused);

        // clear with background color
        // TODO: this seems to prevent setting style later
        // surface.set_style(viewport, theme.get("ui.background"));

        let area = Rect::new(
            viewport.x,
            viewport.y + viewport.height.saturating_sub(1),
            viewport.width,
            1,
        );
        self.render_statusline(&view.doc, area, surface, theme, is_focused);
    }

    pub fn render_buffer(
        &self,
        view: &View,
        viewport: Rect,
        surface: &mut Surface,
        theme: &Theme,
        is_focused: bool,
    ) {
        // TODO: inefficient, should feed chunks.iter() to tree_sitter.parse_with(|offset, pos|)
        let text = view.doc.text();
        let source_code = text.to_string();

        let last_line = view.last_line();

        let range = {
            // calculate viewport byte ranges
            let start = text.line_to_byte(view.first_line);
            let end = text.line_to_byte(last_line + 1);

            start..end
        };

        // TODO: range doesn't actually restrict source, just highlight range
        // TODO: cache highlight results
        // TODO: only recalculate when state.doc is actually modified
        let highlights: Vec<_> = match &view.doc.syntax {
            Some(syntax) => {
                syntax
                    .highlight_iter(source_code.as_bytes(), Some(range), None, |_| None)
                    .unwrap()
                    .collect() // TODO: we collect here to avoid holding the lock, fix later
            }
            None => vec![Ok(HighlightEvent::Source {
                start: range.start,
                end: range.end,
            })],
        };
        let mut spans = Vec::new();
        let mut visual_x = 0;
        let mut line = 0u16;

        'outer: for event in highlights {
            match event.unwrap() {
                HighlightEvent::HighlightStart(span) => {
                    spans.push(span);
                }
                HighlightEvent::HighlightEnd => {
                    spans.pop();
                }
                HighlightEvent::Source { start, end } => {
                    // TODO: filter out spans out of viewport for now..

                    // TODO: do these before iterating
                    let start = text.byte_to_char(start);
                    let end = text.byte_to_char(end);

                    let text = text.slice(start..end);

                    use helix_core::graphemes::{grapheme_width, RopeGraphemes};

                    let style = match spans.first() {
                        Some(span) => theme.get(theme.scopes()[span.0].as_str()),
                        None => Style::default().fg(Color::Rgb(164, 160, 232)), // lavender
                    };

                    // TODO: we could render the text to a surface, then cache that, that
                    // way if only the selection/cursor changes we can copy from cache
                    // and paint the new cursor.
                    // We could keep a single resizable surface on the View for that.

                    let mut char_index = start;

                    // iterate over range char by char
                    for grapheme in RopeGraphemes::new(text) {
                        // TODO: track current char_index

                        if grapheme == "\n" {
                            visual_x = 0;
                            line += 1;

                            // TODO: with proper iter this shouldn't be necessary
                            if line >= viewport.height {
                                break 'outer;
                            }
                        } else if grapheme == "\t" {
                            visual_x += (TAB_WIDTH as u16);
                        } else {
                            if visual_x >= viewport.width {
                                // if we're offscreen just keep going until we hit a new line
                                // TODO: will need tweaking when we also take into account
                                // horizontal scrolling
                                continue;
                            }

                            // Cow will prevent allocations if span contained in a single slice
                            // which should really be the majority case
                            let grapheme = Cow::from(grapheme);
                            let width = grapheme_width(&grapheme) as u16;

                            // ugh,interleave highlight spans with diagnostic spans
                            let is_diagnostic = view.doc.diagnostics.iter().any(|diagnostic| {
                                diagnostic.range.0 <= char_index && diagnostic.range.1 > char_index
                            });

                            let style = if is_diagnostic {
                                style.clone().add_modifier(Modifier::UNDERLINED)
                            } else {
                                style
                            };

                            surface.set_string(
                                viewport.x + visual_x,
                                viewport.y + line,
                                grapheme,
                                style,
                            );

                            visual_x += width;
                        }

                        char_index += 1;
                    }
                }
            }
        }

        // render selections

        if is_focused {
            let screen = {
                let start = text.line_to_char(view.first_line);
                let end = text.line_to_char(last_line + 1);
                Range::new(start, end)
            };
            let text = text.slice(..);
            let cursor_style = Style::default()
                // .bg(Color::Rgb(255, 255, 255))
                .add_modifier(Modifier::REVERSED);

            // let selection_style = Style::default().bg(Color::Rgb(94, 0, 128));
            let selection_style = Style::default().bg(Color::Rgb(84, 0, 153));

            for selection in view
                .doc
                .selection()
                .ranges()
                .iter()
                .filter(|range| range.overlaps(&screen))
            {
                // TODO: render also if only one of the ranges is in viewport
                let mut start = view.screen_coords_at_pos(text, selection.anchor);
                let mut end = view.screen_coords_at_pos(text, selection.head);

                // cursor
                if let Some(end) = end {
                    surface.set_style(
                        Rect::new(
                            viewport.x + end.col as u16,
                            viewport.y + end.row as u16,
                            1,
                            1,
                        ),
                        cursor_style,
                    );
                }

                if selection.head < selection.anchor {
                    std::mem::swap(&mut start, &mut end);
                }
                let start = start.unwrap_or_else(|| Position::new(0, 0));
                let end = end.unwrap_or_else(|| {
                    Position::new(viewport.height as usize, viewport.width as usize)
                });

                if start.row == end.row {
                    surface.set_style(
                        Rect::new(
                            viewport.x + start.col as u16,
                            viewport.y + start.row as u16,
                            (end.col - start.col) as u16,
                            1,
                        ),
                        selection_style,
                    );
                } else {
                    surface.set_style(
                        Rect::new(
                            viewport.x + start.col as u16,
                            viewport.y + start.row as u16,
                            // text.line(view.first_line).len_chars() as u16 - start.col as u16,
                            viewport.width - start.col as u16,
                            1,
                        ),
                        selection_style,
                    );
                    for i in start.row + 1..end.row {
                        surface.set_style(
                            Rect::new(
                                viewport.x,
                                viewport.y + i as u16,
                                // text.line(view.first_line + i).len_chars() as u16,
                                viewport.width,
                                1,
                            ),
                            selection_style,
                        );
                    }
                    surface.set_style(
                        Rect::new(viewport.x, viewport.y + end.row as u16, end.col as u16, 1),
                        selection_style,
                    );
                }
            }
        }

        // render gutters

        let style: Style = theme.get("ui.linenr");
        let warning: Style = theme.get("warning");
        let error: Style = theme.get("error");
        let info: Style = theme.get("info");
        let hint: Style = theme.get("hint");

        let last_line = view.last_line();
        for (i, line) in (view.first_line..last_line).enumerate() {
            use helix_core::diagnostic::Severity;
            if let Some(diagnostic) = view.doc.diagnostics.iter().find(|d| d.line == line) {
                surface.set_stringn(
                    viewport.x - OFFSET,
                    viewport.y + i as u16,
                    "●",
                    1,
                    match diagnostic.severity {
                        Some(Severity::Error) => error,
                        Some(Severity::Warning) | None => warning,
                        Some(Severity::Info) => info,
                        Some(Severity::Hint) => hint,
                    },
                );
            }

            surface.set_stringn(
                viewport.x + 1 - OFFSET,
                viewport.y + i as u16,
                format!("{:>5}", line + 1),
                5,
                style,
            );
        }
    }

    pub fn render_statusline(
        &self,
        doc: &Document,
        viewport: Rect,
        surface: &mut Surface,
        theme: &Theme,
        is_focused: bool,
    ) {
        let mode = match doc.mode() {
            Mode::Insert => "INS",
            Mode::Select => "SEL",
            Mode::Normal => "NOR",
            Mode::Goto => "GOTO",
        };
        // TODO: share text_color styles inside theme
        let text_color = if is_focused {
            Style::default().fg(Color::Rgb(219, 191, 239)) // lilac
        } else {
            Style::default().fg(Color::Rgb(164, 160, 232)) // lavender
        };
        // statusline
        surface.set_style(
            Rect::new(viewport.x, viewport.y, viewport.width, 1),
            theme.get("ui.statusline"),
        );
        if is_focused {
            surface.set_string(viewport.x + 1, viewport.y, mode, text_color);
        }

        if let Some(path) = doc.relative_path() {
            let path = path.to_string_lossy();
            surface.set_stringn(
                viewport.x + 6,
                viewport.y,
                path,
                viewport.width.saturating_sub(6) as usize,
                text_color,
            );
            // TODO: append [+] if modified
        }

        surface.set_string(
            viewport.x + viewport.width.saturating_sub(10),
            viewport.y,
            format!("{}", doc.diagnostics.len()),
            text_color,
        );
    }
}

impl Component for EditorView {
    fn handle_event(&mut self, event: Event, cx: &mut Context) -> EventResult {
        match event {
            Event::Resize(width, height) => {
                // HAXX: offset the render area height by 1 to account for prompt/commandline
                cx.editor.tree.resize(Rect::new(0, 0, width, height - 1));
                EventResult::Consumed(None)
            }
            Event::Key(event) => {
                let view = cx.editor.view_mut();

                // TODO: sequences (`gg`)
                let mode = view.doc.mode();
                // TODO: handle count other than 1
                let mut cxt = commands::Context {
                    executor: cx.executor,
                    editor: &mut cx.editor,
                    count: 1,
                    callback: None,
                    on_next_key_callback: None,
                };

                if let Some(on_next_key) = self.on_next_key.take() {
                    // if there's a command waiting input, do that first
                    on_next_key(&mut cxt, event);
                } else {
                    match mode {
                        Mode::Insert => {
                            if let Some(command) = self.keymap[&Mode::Insert].get(&event) {
                                command(&mut cxt);
                            } else if let KeyEvent {
                                code: KeyCode::Char(c),
                                ..
                            } = event
                            {
                                commands::insert::insert_char(&mut cxt, c);
                            }
                        }
                        mode => {
                            match event {
                                KeyEvent {
                                    code: KeyCode::Char(i @ '0'..='9'),
                                    modifiers: KeyModifiers::NONE,
                                } => {
                                    let i = i.to_digit(10).unwrap() as usize;
                                    cxt.editor.count =
                                        Some(cxt.editor.count.map_or(i, |c| c * 10 + i));
                                }
                                _ => {
                                    // set the count
                                    cxt.count = cxt.editor.count.take().unwrap_or(1);
                                    // TODO: edge case: 0j -> reset to 1
                                    // if this fails, count was Some(0)
                                    // debug_assert!(cxt.count != 0);

                                    if let Some(command) = self.keymap[&mode].get(&event) {
                                        command(&mut cxt);

                                        // TODO: simplistic ensure cursor in view for now
                                    }
                                }
                            }
                        }
                    }
                }

                self.on_next_key = cxt.on_next_key_callback.take();

                // appease borrowck
                let callback = cxt.callback.take();
                drop(cxt);
                cx.editor.view_mut().ensure_cursor_in_view();

                EventResult::Consumed(callback)
            }
            Event::Mouse(_) => EventResult::Ignored,
        }
    }

    fn render(&self, mut area: Rect, surface: &mut Surface, cx: &mut Context) {
        for (view, is_focused) in cx.editor.tree.views() {
            // TODO: use parent area
            self.render_view(view, view.area, surface, &cx.editor.theme, is_focused);
        }
    }

    fn cursor_position(&self, area: Rect, editor: &Editor) -> Option<Position> {
        // match view.doc.mode() {
        //     Mode::Insert => write!(stdout, "\x1B[6 q"),
        //     mode => write!(stdout, "\x1B[2 q"),
        // };
        // return editor.cursor_position()

        // It's easier to just not render the cursor and use selection rendering instead.
        None
    }
}