strop-editor 0.2.1

//! Pane rendering — one text renderer for every pane (0010 §3).
//! Active panes read live editor state with overlays; inactive panes
//! read their saved snapshot without. Same gutter, same guides, same
//! diff rows — the duplicated inactive-pane loop is gone, so panes
//! cannot drift apart again.

use ratatui::layout::Rect;
use ratatui::style::{Color, Modifier, Style};
use ratatui::text::{Line, Span};
use ratatui::widgets::Paragraph;
use ratatui::Frame;

use crate::editor::{Editor, LayoutDir};

use super::diff;
use super::{class_color, in_range, ACCENT, BASE, FLASH_BG, MUTED, PREVIEW_BG, SELECT_BG, TEXT};

/// Width of the standard gutter: sign column + 3-digit number + space.
pub(crate) const GUTTER: u16 = 5;

/// One pane's view of a buffer. `overlays` is false for inactive panes:
/// preview/search/selection/flash belong to the pane being driven.
struct PaneView {
    buffer: usize,
    cursor: usize,
    view_top: usize,
    overlays: bool,
}

/// Render all panes and return the active pane's rect (the native
/// cursor lives there — offsets included, which the full-area version
/// got wrong in splits).
pub(crate) fn render_panes(editor: &mut Editor, frame: &mut Frame, area: Rect) -> Rect {
    let n = editor.panes.len();
    let is_row = editor.layout == LayoutDir::Row;
    let total_w = area.width as usize;
    let total_h = area.height as usize - 1; // statusline
    let dividers = n - 1;
    let (mut x, mut y) = (area.x, area.y);
    let mut active_rect = Rect {
        x,
        y,
        width: total_w as u16,
        height: total_h as u16,
    };
    for i in 0..n {
        let (w, h): (u16, u16) = if is_row {
            let w = ((total_w - dividers) / n) as u16;
            let w = if i == n - 1 {
                (total_w - dividers) as u16 - w * (n as u16 - 1)
            } else {
                w
            };
            (w, total_h as u16)
        } else {
            let h = ((total_h - dividers) / n) as u16;
            let h = if i == n - 1 {
                (total_h - dividers) as u16 - h * (n as u16 - 1)
            } else {
                h
            };
            (total_w as u16, h)
        };
        let rect = Rect {
            x,
            y,
            width: w,
            height: h,
        };
        let view = if i == editor.active_pane {
            PaneView {
                buffer: editor.current,
                cursor: editor.cursor,
                view_top: editor.view_top,
                overlays: true,
            }
        } else {
            let pane = &editor.panes[i];
            PaneView {
                buffer: pane.buffer.min(editor.buffers.len() - 1),
                cursor: pane.cursor,
                view_top: pane.view_top,
                overlays: false,
            }
        };
        render_pane(editor, frame, rect, &view);
        if i == editor.active_pane {
            active_rect = rect;
        } else {
            render_static_caret(editor, frame, rect, &view);
        }
        if i < n - 1 {
            // divider column/row
            if is_row {
                let dx = x + w;
                for dy in y..y + h {
                    let cell = &mut frame.buffer_mut()[(dx, dy)];
                    cell.set_symbol("│");
                    cell.set_fg(Color::Rgb(0x3a, 0x3d, 0x4d));
                }
                x = dx + 1;
            } else {
                let dy = y + h;
                for dx in x..x + w {
                    let cell = &mut frame.buffer_mut()[(dx, dy)];
                    cell.set_symbol("─");
                    cell.set_fg(Color::Rgb(0x3a, 0x3d, 0x4d));
                }
                y = dy + 1;
            }
        }
    }
    active_rect
}

/// The inactive pane's position, unfocused: a muted block on the saved
/// cursor cell, offsets pane-local (unlike the native cursor).
fn render_static_caret(editor: &Editor, frame: &mut Frame, area: Rect, view: &PaneView) {
    let buf = &editor.buffers[view.buffer];
    let line = buf.line_of(view.cursor);
    let row = line.saturating_sub(view.view_top) as u16;
    let surface = editor.surfaces.get(view.buffer).and_then(|s| s.as_ref());
    let gutter = diff::gutter_width(surface) as u16;
    let col = gutter + buf.col_of(view.cursor) as u16;
    if row < area.height && col < area.width {
        let cell = &mut frame.buffer_mut()[(area.x + col, area.y + row)];
        cell.set_bg(Color::Rgb(0x3a, 0x3d, 0x4d));
    }
}

/// Render one pane's rows: gutter, syntax/decoration, overlays, guides.
fn render_pane(editor: &mut Editor, frame: &mut Frame, area: Rect, view: &PaneView) {
    let text_rows = area.height as usize;
    let buf = &editor.buffers[view.buffer];
    let cur_line = buf.line_of(view.cursor);
    let surface = editor.surfaces.get(view.buffer).and_then(|s| s.as_ref());

    // tree-sitter spans for the visible window (base layer, 0001 §5.8)
    let first_byte = buf.line_start(view.view_top);
    let last_line = (view.view_top + text_rows).min(buf.len_lines());
    let last_byte = buf.line_end(last_line.saturating_sub(1));
    let rope = editor.buffers[view.buffer].rope.clone();
    let syn_spans: Vec<strop_syntax::Span> = match editor.highlighters.get_mut(view.buffer) {
        Some(h) => h
            .as_mut()
            .map(|h| h.highlight(&rope, first_byte, last_byte))
            .unwrap_or_default(),
        None => Vec::new(),
    };

    // overlays read live editor state; only the active pane shows them
    let mut row_style = RowStyle {
        syn_spans: &syn_spans,
        preview: view
            .overlays
            .then(|| editor.preview())
            .flatten()
            .map(|r| r.range),
        flash: view.overlays.then(|| editor.flash_range()).flatten(),
        selection: view.overlays.then(|| editor.visual_range()).flatten(),
        search_hits: &[],
        find: view.overlays.then(|| editor.find_candidates()).flatten(),
        diff_line: None,
    };
    let search_hits: Vec<usize> = if view.overlays {
        editor
            .search_pattern()
            .map(|p| strop_grammar::search_all(editor.buf(), p))
            .unwrap_or_default()
    } else {
        Vec::new()
    };
    row_style.search_hits = &search_hits;

    let mut lines: Vec<Line> = Vec::with_capacity(text_rows);
    let diff_digits = diff_digits(surface);
    for row in 0..text_rows {
        let line_idx = view.view_top + row;
        if line_idx > buf.last_content_line() {
            lines.push(Line::from(Span::styled("~", Style::default().fg(MUTED))));
            continue;
        }
        let start = buf.line_start(line_idx);
        let text = buf.line_text(line_idx);

        // git memory surfaces decorate their rows from typed data
        // (0010 §4/§5): diff rows re-gutter, log/files rows re-color
        match diff::diff_row(surface, line_idx) {
            Some(diff::DiffRow::Stats | diff::DiffRow::HunkHeader) => {
                lines.push(diff::structural_row(surface.unwrap(), line_idx, area.width));
                continue;
            }
            Some(diff::DiffRow::Line(dl)) => {
                let mut spans = diff::diff_gutter(dl, line_idx == cur_line, diff_digits);
                row_style.diff_line = Some(dl);
                spans.extend(content_spans(
                    editor, view, start, &text, &row_style, area.width,
                ));
                lines.push(Line::from(spans));
                continue;
            }
            None => {}
        }

        let num_style = if line_idx == cur_line {
            Style::default().fg(ACCENT)
        } else {
            Style::default().fg(MUTED)
        };
        // Helix-grade gutter: a colored ▎ bar in the leftmost column —
        // diagnostics first, then git signs (green/amber/red)
        let (bar, bar_color) = gutter_mark(editor, view, line_idx);
        let mut spans = vec![
            Span::styled(
                bar,
                Style::default().fg(bar_color).add_modifier(Modifier::BOLD),
            ),
            Span::styled(format!("{:>3} ", line_idx + 1), num_style),
        ];
        row_style.diff_line = None;
        if let Some(content) = diff::surface_content_spans(surface, line_idx, area.width) {
            spans.extend(content);
        } else {
            spans.extend(content_spans(
                editor, view, start, &text, &row_style, area.width,
            ));
        }
        lines.push(Line::from(spans));
    }
    frame.render_widget(
        Paragraph::new(lines).style(Style::default().bg(BASE)),
        Rect {
            height: text_rows as u16,
            ..area
        },
    );
}

/// Digits per side for a Diff surface's number columns.
fn diff_digits(surface: Option<&crate::editor::Surface>) -> usize {
    let width = diff::gutter_width(surface);
    if width == super::buffer::GUTTER as usize {
        3
    } else {
        (width - 3) / 2
    }
}

/// The sign column: diagnostics win over git signs (merged gutter,
/// 0009), and only the pane's own buffer shows them.
fn gutter_mark(editor: &Editor, view: &PaneView, line_idx: usize) -> (&'static str, Color) {
    if let Some(sev) = editor.diag_severity_at(view.buffer, line_idx + 1) {
        return match sev {
            1 => ("E", Color::Rgb(0xe8, 0x67, 0x7a)),
            2 => ("W", ACCENT),
            _ => ("▎", Color::Rgb(0x7f, 0xb4, 0xca)),
        };
    }
    // git signs: + add, ~ change, - deletion below (only for the
    // working buffer — surfaces have no path, so no leak)
    if view.buffer == editor.current {
        match editor.sign_at(line_idx + 1) {
            Some('+') => return ("▎", Color::Rgb(0xa9, 0xc4, 0x7c)),
            Some('~') => return ("▎", ACCENT),
            Some('-') => return ("▎", Color::Rgb(0xe8, 0x67, 0x7a)),
            _ => {}
        }
    }
    (" ", MUTED)
}

/// The per-pane, per-frame style inputs one content row composes:
/// base layers (syntax spans or a diff line) plus the active pane's
/// overlays. Inactive panes get the default (no overlays).
#[derive(Default)]
struct RowStyle<'a> {
    syn_spans: &'a [strop_syntax::Span],
    preview: Option<strop_core::Range>,
    flash: Option<strop_core::Range>,
    selection: Option<strop_core::Range>,
    search_hits: &'a [usize],
    find: Option<(u8, bool)>,
    /// Set on diff-surface rows: typed origin drives colors (0010 §4).
    diff_line: Option<&'a strop_git::DiffLine>,
}

/// Content spans for one row: syntax or diff decoration, then overlays
/// composed on top (search < preview < flash, 0001 §5.8). Diff rows get
/// a full-width background pad.
fn content_spans(
    editor: &Editor,
    view: &PaneView,
    start: usize,
    text: &str,
    style: &RowStyle,
    width: u16,
) -> Vec<Span<'static>> {
    let buf = &editor.buffers[view.buffer];
    let cur_line = buf.line_of(view.cursor);
    // indent guides: dim │ at each indent level within leading
    // whitespace (spaces only, v1)
    let lead_ws = if editor.config.indent_guides {
        text.chars().take_while(|c| *c == ' ').count()
    } else {
        0
    };
    let tab = editor.config.tab_size.max(1);
    let syn_spans = style.syn_spans;
    let mut syn_idx = syn_spans.partition_point(|s| s.end <= start);
    let mut spans = Vec::with_capacity(text.len() / 2 + 4);
    let mut chars = 0usize;
    for (i, ch) in text.chars().enumerate() {
        let pos = start + i; // prototype is ASCII-honest (0001 §5.9 later)
        while syn_idx < syn_spans.len() && syn_spans[syn_idx].end <= pos {
            syn_idx += 1;
        }
        let mut cell = Style::default().fg(TEXT);
        if let Some(dl) = style.diff_line {
            cell = cell.fg(diff::origin_fg(dl.origin));
            if let Some(bg) = diff::origin_bg(dl.origin) {
                cell = cell.bg(bg);
            }
        } else if syn_idx < syn_spans.len() && syn_spans[syn_idx].start <= pos {
            let class = syn_spans[syn_idx].class;
            cell = cell.fg(class_color(class));
            if class == strop_syntax::Class::Comment {
                cell = cell.add_modifier(Modifier::ITALIC);
            }
        }
        if style.selection.is_some_and(|r| in_range(r, pos)) {
            cell = cell.bg(SELECT_BG);
        }
        if style
            .search_hits
            .iter()
            .any(|&h| pos >= h && pos < h + editor.search_pattern().map_or(0, str::len))
        {
            cell = cell.fg(ACCENT).add_modifier(Modifier::BOLD);
        }
        if let Some((_, backward)) = style.find {
            // leap-style: candidates bold-accent on the pending side
            let on_line = buf.line_of(pos) == cur_line;
            let ahead = if backward {
                pos < view.cursor
            } else {
                pos > view.cursor
            };
            if on_line && ahead && !ch.is_whitespace() {
                cell = cell.fg(ACCENT).add_modifier(Modifier::BOLD);
            }
        }
        if style.preview.is_some_and(|r| in_range(r, pos)) {
            cell = cell.fg(ACCENT).bg(PREVIEW_BG);
        }
        if style.flash.is_some_and(|r| in_range(r, pos)) {
            cell = cell.bg(FLASH_BG);
        }
        let is_guide = i < lead_ws && (i + 1) % tab == 0;
        if is_guide {
            spans.push(Span::styled("│", cell.fg(Color::Rgb(0x2e, 0x30, 0x42))));
        } else {
            spans.push(Span::styled(ch.to_string(), cell));
        }
        chars += 1;
    }
    // full-row backgrounds for add/del rows run past the text (0010 §4)
    if let Some(dl) = style.diff_line {
        if let Some(bg) = diff::origin_bg(dl.origin) {
            let used =
                diff::gutter_width(editor.surfaces.get(view.buffer).and_then(|s| s.as_ref()))
                    + chars;
            let pad = (width as usize).saturating_sub(used);
            if pad > 0 {
                spans.push(Span::styled(
                    " ".repeat(pad),
                    Style::default().fg(bg).bg(bg),
                ));
            }
        }
    }
    spans
}