mmdflux 2.2.0

//! Subgraph border drawing for graph text output.

use std::collections::HashMap;

use crate::graph::grid::SubgraphBounds;
use crate::render::text::canvas::Canvas;
use crate::render::text::chars::CharSet;

/// Render subgraph border rectangles and concurrent region dividers on the canvas.
///
/// Draws borders BEFORE nodes and edges so they appear in the background.
/// Cells are marked as `is_subgraph_border` (not protected from overwrite).
/// Title is placed above the top-left corner of the border.
pub fn render_subgraph_borders(
    canvas: &mut Canvas,
    subgraph_bounds: &HashMap<String, SubgraphBounds>,
    charset: &CharSet,
) {
    // Sort by depth: outer borders first (background), inner last (foreground)
    let mut sorted_bounds: Vec<_> = subgraph_bounds.values().collect();
    sorted_bounds.sort_by(|a, b| a.depth.cmp(&b.depth).then_with(|| a.title.cmp(&b.title)));

    for bounds in sorted_bounds {
        // Invisible subgraphs participate in layout but render no border.
        if bounds.invisible {
            continue;
        }

        let x = bounds.x;
        let y = bounds.y;
        let w = bounds.width;
        let h = bounds.height;

        // Need at least 2×2 to draw a border box (corners only)
        if w < 2 || h < 2 {
            continue;
        }

        // Top edge with embedded title: ┌─ Title ─┐
        canvas.set_subgraph_border(x, y, charset.corner_tl);
        canvas.set_subgraph_border(x + w - 1, y, charset.corner_tr);

        let inner_width = w.saturating_sub(2); // space between corners
        let has_visible_title = !bounds.title.is_empty() && !bounds.title.trim().is_empty();
        if has_visible_title && inner_width >= 5 {
            // Title section: "─ Title ─" = title.len() + 4 chars overhead
            let max_title_len = inner_width.saturating_sub(4);
            let title: String = bounds.title.chars().take(max_title_len).collect();
            let title_section_len = title.len() + 4; // "─ " + title + " ─"
            let left_fill = (inner_width.saturating_sub(title_section_len)) / 2;

            // Left horizontal fill
            for i in 0..left_fill {
                canvas.set_subgraph_border(x + 1 + i, y, charset.horizontal);
            }
            // "─ " prefix
            canvas.set_subgraph_border(x + 1 + left_fill, y, charset.horizontal);
            canvas.set_subgraph_border(x + 1 + left_fill + 1, y, ' ');
            // Centered title
            let title_start = x + 1 + left_fill + 2;
            for (i, ch) in title.chars().enumerate() {
                canvas.set_subgraph_title_char(title_start + i, y, ch);
            }
            // " " suffix
            let title_end = title_start + title.len();
            canvas.set_subgraph_border(title_end, y, ' ');

            // Right horizontal fill
            for dx in (title_end + 1)..(x + w - 1) {
                canvas.set_subgraph_border(dx, y, charset.horizontal);
            }

            // Protect the entire top border row so edges cannot corrupt
            // the embedded title segment.
            for dx in 1..(w - 1) {
                if let Some(cell) = canvas.get(x + dx, y) {
                    let _ = canvas.set_subgraph_title_char(x + dx, y, cell.ch);
                }
            }
        } else {
            // No title or too narrow: plain horizontal
            for dx in 1..(w - 1) {
                canvas.set_subgraph_border(x + dx, y, charset.horizontal);
            }
        }

        // Sides
        for dy in 1..h - 1 {
            canvas.set_subgraph_border(x, y + dy, charset.vertical);
            canvas.set_subgraph_border(x + w - 1, y + dy, charset.vertical);
        }

        // Bottom edge
        canvas.set_subgraph_border(x, y + h - 1, charset.corner_bl);
        for dx in 1..w - 1 {
            canvas.set_subgraph_border(x + dx, y + h - 1, charset.horizontal);
        }
        canvas.set_subgraph_border(x + w - 1, y + h - 1, charset.corner_br);
    }

    // Draw dashed divider lines between concurrent regions.
    render_region_dividers(canvas, subgraph_bounds, charset);
}

/// Draw dashed vertical dividers between concurrent region subgraphs.
///
/// Concurrent regions are always arranged LR (side-by-side), matching UML
/// convention. For each parent subgraph with `concurrent_regions`, draws a
/// vertical dashed line between each pair of adjacent regions.
fn render_region_dividers(
    canvas: &mut Canvas,
    subgraph_bounds: &HashMap<String, SubgraphBounds>,
    charset: &CharSet,
) {
    for parent in subgraph_bounds.values() {
        if parent.concurrent_regions.len() < 2 {
            continue;
        }

        // Collect region bounds in order, skipping any that are missing.
        let region_bounds: Vec<&SubgraphBounds> = parent
            .concurrent_regions
            .iter()
            .filter_map(|id| subgraph_bounds.get(id))
            .collect();

        // Draw a vertical divider between each pair of adjacent (LR) regions.
        for pair in region_bounds.windows(2) {
            let left_region = pair[0];
            let right_region = pair[1];

            // Divider x: midpoint between right edge of left region and left edge of right.
            let left_right_edge = left_region.x + left_region.width;
            let right_left_edge = right_region.x;
            if right_left_edge <= left_right_edge {
                continue;
            }
            let divider_x = left_right_edge + (right_left_edge - left_right_edge) / 2;

            // Divider spans the parent's inner height (between top/bottom borders).
            let top = parent.y + 1;
            let bottom = parent.y + parent.height - 1;
            // Top junction: ┬ (connects to parent's top border).
            // Skip if the cell contains a title character to avoid overwriting.
            let top_is_title = canvas
                .get(divider_x, parent.y)
                .is_some_and(|c| c.is_subgraph_title);
            if !top_is_title {
                canvas.set_subgraph_border(divider_x, parent.y, charset.tee_down);
            }
            for dy in top..bottom {
                canvas.set_subgraph_border(divider_x, dy, charset.dotted_vertical);
            }
            // Bottom junction: ┴ (connects to parent's bottom border)
            canvas.set_subgraph_border(divider_x, parent.y + parent.height - 1, charset.tee_up);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_render_subgraph_border_characters() {
        let mut canvas = Canvas::new(20, 10);
        let bounds = SubgraphBounds {
            x: 2,
            y: 3,
            width: 13,
            height: 5,
            title: "Group".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);
        let charset = CharSet::unicode();

        render_subgraph_borders(&mut canvas, &map, &charset);

        // Verify corners
        assert_eq!(canvas.get(2, 3).unwrap().ch, charset.corner_tl);
        assert_eq!(canvas.get(14, 3).unwrap().ch, charset.corner_tr);
        assert_eq!(canvas.get(2, 7).unwrap().ch, charset.corner_bl);
        assert_eq!(canvas.get(14, 7).unwrap().ch, charset.corner_br);

        // Verify centered title in top border: ┌── Group ──┐
        // left_fill=1: x+1=3 → '─', x+2=4 → '─' (prefix), x+3=5 → ' ',
        // x+4..x+8=6..10 → "Group", x+9=11 → ' ', x+10..x+11=12..13 → '─'
        assert_eq!(canvas.get(3, 3).unwrap().ch, charset.horizontal);
        assert_eq!(canvas.get(4, 3).unwrap().ch, charset.horizontal);
        assert_eq!(canvas.get(5, 3).unwrap().ch, ' ');
        assert_eq!(canvas.get(6, 3).unwrap().ch, 'G');
        assert_eq!(canvas.get(10, 3).unwrap().ch, 'p');
        assert_eq!(canvas.get(11, 3).unwrap().ch, ' ');

        // Verify vertical edges
        assert_eq!(canvas.get(2, 5).unwrap().ch, charset.vertical);

        // Verify is_subgraph_border flag
        assert!(canvas.get(2, 3).unwrap().is_subgraph_border);
    }

    #[test]
    fn test_render_subgraph_title_embedded_in_border() {
        let mut canvas = Canvas::new(20, 10);
        let bounds = SubgraphBounds {
            x: 2,
            y: 3,
            width: 13,
            height: 5,
            title: "Group".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);

        render_subgraph_borders(&mut canvas, &map, &CharSet::unicode());

        // Title centered in top border row (y=3), not above it
        assert_eq!(canvas.get(6, 3).unwrap().ch, 'G');
        assert_eq!(canvas.get(7, 3).unwrap().ch, 'r');
        assert_eq!(canvas.get(8, 3).unwrap().ch, 'o');
        assert_eq!(canvas.get(9, 3).unwrap().ch, 'u');
        assert_eq!(canvas.get(10, 3).unwrap().ch, 'p');

        // Row above border should NOT have the title
        assert_ne!(canvas.get(5, 2).unwrap().ch, 'G');
    }

    #[test]
    fn test_render_subgraph_ascii_mode() {
        let mut canvas = Canvas::new(20, 10);
        let bounds = SubgraphBounds {
            x: 2,
            y: 3,
            width: 10,
            height: 5,
            title: "Test".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);

        render_subgraph_borders(&mut canvas, &map, &CharSet::ascii());

        assert_eq!(canvas.get(2, 3).unwrap().ch, '+');
        // ASCII mode: embedded title in top border
        assert_eq!(canvas.get(3, 3).unwrap().ch, '-'); // prefix dash
        assert_eq!(canvas.get(5, 3).unwrap().ch, 'T'); // title start
        assert_eq!(canvas.get(2, 5).unwrap().ch, '|');
    }

    // =========================================================================
    // Embedded Title Tests (Plan 0026, Task 2.1)
    // =========================================================================

    #[test]
    fn test_render_subgraph_embedded_title() {
        let charset = CharSet::unicode();
        let mut canvas = Canvas::new(20, 7);
        let bounds = SubgraphBounds {
            x: 2,
            y: 2,
            width: 14,
            height: 5,
            title: "Group".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);

        render_subgraph_borders(&mut canvas, &map, &charset);

        let output = canvas.to_string();
        let lines: Vec<&str> = output.lines().collect();

        // First line (after empty row trimming) is the top border with embedded title
        assert!(
            lines[0].contains("─ Group ─"),
            "Expected embedded title in top border, got: {}",
            lines[0]
        );

        // Side rows should NOT contain title text
        assert!(
            !lines[1].contains("Group"),
            "Title should not appear in side row, got: {}",
            lines[1]
        );
    }

    #[test]
    fn test_render_subgraph_title_at_y0() {
        let charset = CharSet::unicode();
        let mut canvas = Canvas::new(20, 7);
        let bounds = SubgraphBounds {
            x: 0,
            y: 0,
            width: 16,
            height: 5,
            title: "TopGroup".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);

        render_subgraph_borders(&mut canvas, &map, &charset);

        let output = canvas.to_string();
        let lines: Vec<&str> = output.lines().collect();

        // Title should be visible even at y=0 (embedded in border)
        assert!(
            lines[0].contains("TopGroup"),
            "Title should render at y=0, got: {}",
            lines[0]
        );
    }

    #[test]
    fn test_render_subgraph_narrow_border_truncates_title() {
        let charset = CharSet::unicode();
        let mut canvas = Canvas::new(15, 5);
        let bounds = SubgraphBounds {
            x: 0,
            y: 0,
            width: 8,
            height: 5,
            title: "Very Long Title".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);

        render_subgraph_borders(&mut canvas, &map, &charset);

        let output = canvas.to_string();
        // Title should be truncated to fit within border
        assert!(
            !output.contains("Very Long Title"),
            "Full title should not appear in narrow border"
        );
        // Border corners should still be intact
        assert!(output.contains("┌"), "Top-left corner should exist");
        assert!(output.contains("┐"), "Top-right corner should exist");
    }

    #[test]
    fn test_render_subgraph_whitespace_title_renders_no_title() {
        let charset = CharSet::unicode();
        let mut canvas = Canvas::new(20, 7);
        let bounds = SubgraphBounds {
            x: 2,
            y: 2,
            width: 14,
            height: 5,
            title: " ".to_string(),
            depth: 0,
            invisible: false,
            concurrent_regions: Vec::new(),
        };
        let mut map = HashMap::new();
        map.insert("sg1".to_string(), bounds);

        render_subgraph_borders(&mut canvas, &map, &charset);

        // Top border should be plain horizontal line, no title text
        let output = canvas.to_string();
        let lines: Vec<&str> = output.lines().collect();
        assert!(
            !lines[0].contains("─  ─"),
            "Should not have title gaps in border, got: {}",
            lines[0]
        );
        // Should just be corner + horizontal fill + corner
        assert!(
            lines[0].contains("┌────────────┐"),
            "Expected plain top border, got: {}",
            lines[0]
        );
    }
}