facett-graph 0.1.0

//! **Dependency-graph** component — a layered DAG. Ported + generalised from
//! nornir's `src/viz/graph.rs` (phase 1: copied here, nornir still owns its
//! copy). Nodes toposorted into columns (deps left → dependents right), drawn as
//! **boxes** with a status-coloured border + optional sub-label; edges as
//! **arrows** with a `via` label; click a node to select → a drill-down panel of
//! its deps/dependents.
//!
//! Generic: the consumer supplies `(nodes, edges)` (indices + colours), not a
//! nornir `Timeline`. nornir keeps the *data*; facett draws the *shape*.

use std::collections::{BTreeMap, VecDeque};

use egui::{Align2, Color32, FontId, Pos2, Rect, CornerRadius, Sense, Stroke, Ui, Vec2};
use facett_core::{Facet, FacetCaps, theme};

const NODE_W: f32 = 160.0;
const NODE_H: f32 = 56.0;
const COL_GAP: f32 = 220.0;
const ROW_GAP: f32 = 90.0;
const LEFT_PAD: f32 = 30.0;
const TOP_PAD: f32 = 40.0;

/// One node: a label, an optional sub-label (a sha, a version…), and a border
/// colour (the consumer's status policy).
#[derive(Clone)]
pub struct DepNode {
    pub label: String,
    pub sublabel: Option<String>,
    pub color: Color32,
}

/// A directed edge `from → to`, with the connecting items shown on the arrow.
#[derive(Clone)]
pub struct DepEdge {
    pub from: usize,
    pub to: usize,
    pub via: Vec<String>,
}

/// The layered dep-graph viewer. Implements [`Facet`].
pub struct DepGraphView {
    pub title: String,
    pub nodes: Vec<DepNode>,
    pub edges: Vec<DepEdge>,
    pub selected: Option<usize>,
}

impl DepGraphView {
    pub fn new(nodes: Vec<DepNode>, edges: Vec<DepEdge>) -> Self {
        Self { title: "deps".into(), nodes, edges, selected: None }
    }
    pub fn with_title(mut self, t: impl Into<String>) -> Self {
        self.title = t.into();
        self
    }

    /// Column index per node — toposort, deps first (left). Longest-path layering
    /// so a dependent sits right of all its deps. Cycle → best effort.
    pub fn columns(&self) -> Vec<usize> {
        let n = self.nodes.len();
        let mut indeg = vec![0usize; n];
        let mut adj: Vec<Vec<usize>> = vec![Vec::new(); n];
        for e in &self.edges {
            if e.from < n && e.to < n {
                // `from` consumes `to` → place `to` first.
                adj[e.to].push(e.from);
                indeg[e.from] += 1;
            }
        }
        let mut col = vec![0usize; n];
        let mut q: VecDeque<usize> = (0..n).filter(|&i| indeg[i] == 0).collect();
        while let Some(r) = q.pop_front() {
            for &c in &adj[r] {
                col[c] = col[c].max(col[r] + 1);
                indeg[c] -= 1;
                if indeg[c] == 0 {
                    q.push_back(c);
                }
            }
        }
        col
    }

    pub fn show(&mut self, ui: &mut Ui) {
        if self.nodes.is_empty() {
            ui.label("no nodes");
            return;
        }
        let col = self.columns();
        let mut row_of = vec![0usize; self.nodes.len()];
        let mut per_col: BTreeMap<usize, usize> = BTreeMap::new();
        for (i, &c) in col.iter().enumerate() {
            let r = per_col.entry(c).or_insert(0);
            row_of[i] = *r;
            *r += 1;
        }
        let ncols = col.iter().copied().max().unwrap_or(0) + 1;
        let nrows = per_col.values().copied().max().unwrap_or(1);
        let needed_w = LEFT_PAD + ncols as f32 * COL_GAP + NODE_W;
        let needed_h = TOP_PAD + nrows as f32 * ROW_GAP + NODE_H;
        let avail = ui.available_size();
        let canvas = Vec2::new(avail.x.max(needed_w), avail.y.max(needed_h.max(360.0)));
        let (rect, resp) = ui.allocate_exact_size(canvas, Sense::click());
        let th = theme(ui);
        let painter = ui.painter_at(rect);
        painter.rect_filled(rect, CornerRadius::ZERO, th.bg);

        let pos_for = |i: usize| {
            Pos2::new(
                rect.left() + LEFT_PAD + col[i] as f32 * COL_GAP,
                rect.top() + TOP_PAD + row_of[i] as f32 * ROW_GAP,
            )
        };

        // edges (under nodes)
        for e in &self.edges {
            if e.from >= self.nodes.len() || e.to >= self.nodes.len() {
                continue;
            }
            let from = pos_for(e.from) + Vec2::new(NODE_W / 2.0, NODE_H / 2.0);
            let to = pos_for(e.to) + Vec2::new(NODE_W / 2.0, NODE_H / 2.0);
            draw_arrow(&painter, from, to, th.edge);
            if !e.via.is_empty() {
                let via = e.via.iter().take(2).cloned().collect::<Vec<_>>().join(", ");
                let label = if e.via.len() > 2 { format!("{via} +{}", e.via.len() - 2) } else { via };
                let mid = Pos2::new((from.x + to.x) / 2.0, (from.y + to.y) / 2.0 - 8.0);
                painter.text(mid, Align2::CENTER_BOTTOM, &label, FontId::monospace(10.0), th.text_dim);
            }
        }

        // nodes
        for (i, node) in self.nodes.iter().enumerate() {
            let p = pos_for(i);
            let nrect = Rect::from_min_size(p, Vec2::new(NODE_W, NODE_H));
            let is_sel = self.selected == Some(i);
            let fill = if is_sel { th.accent.linear_multiply(0.2) } else { th.node_fill };
            painter.rect_filled(nrect, CornerRadius::same(6), fill);
            let (bw, bc) = if is_sel { (3.0, th.accent) } else { (2.0, node.color) };
            painter.rect_stroke(nrect, CornerRadius::same(6), Stroke::new(bw, bc), egui::StrokeKind::Inside);
            painter.text(p + Vec2::new(NODE_W / 2.0, 14.0), Align2::CENTER_TOP, &node.label, FontId::proportional(15.0), th.text);
            if let Some(sub) = &node.sublabel {
                let short: String = sub.chars().take(12).collect();
                painter.text(p + Vec2::new(NODE_W / 2.0, 34.0), Align2::CENTER_TOP, short, FontId::monospace(11.0), th.text_dim);
            }
        }

        // click-select
        if resp.clicked() {
            if let Some(pos) = resp.interact_pointer_pos() {
                let hit = (0..self.nodes.len()).find(|&i| Rect::from_min_size(pos_for(i), Vec2::new(NODE_W, NODE_H)).contains(pos));
                if let Some(i) = hit {
                    self.selected = if self.selected == Some(i) { None } else { Some(i) };
                }
            }
        }

        // drill-down panel
        if let Some(sel) = self.selected {
            let deps: Vec<String> = self
                .edges
                .iter()
                .filter(|e| e.from == sel)
                .map(|e| format!("  → {}   [{}]", self.nodes[e.to].label, e.via.join(", ")))
                .collect();
            let users: Vec<String> = self
                .edges
                .iter()
                .filter(|e| e.to == sel)
                .map(|e| format!("  ← {}   [{}]", self.nodes[e.from].label, e.via.join(", ")))
                .collect();
            let rows = 3 + deps.len() + users.len();
            let panel = Rect::from_min_size(rect.left_top() + Vec2::new(8.0, 8.0), Vec2::new(380.0, rows as f32 * 16.0 + 16.0));
            painter.rect_filled(panel, CornerRadius::same(6), th.panel_bg);
            painter.rect_stroke(panel, CornerRadius::same(6), Stroke::new(1.0, th.panel_stroke), egui::StrokeKind::Inside);
            let mut y = panel.top() + 8.0;
            let mut put = |s: &str, c: Color32| {
                painter.text(Pos2::new(panel.left() + 10.0, y), Align2::LEFT_TOP, s, FontId::proportional(12.0), c);
                y += 16.0;
            };
            put(&format!("◆ {}  (click again to deselect)", self.nodes[sel].label), th.accent);
            put(&format!("depends on ({}):", deps.len()), th.text_dim);
            for d in &deps {
                put(d, th.text);
            }
            put(&format!("used by ({}):", users.len()), th.text_dim);
            for u in &users {
                put(u, th.text);
            }
        }
    }
}

/// Line + arrowhead from `from` to `to` (head pulled back by half a node width).
pub fn draw_arrow(painter: &egui::Painter, from: Pos2, to: Pos2, color: Color32) {
    painter.line_segment([from, to], Stroke::new(2.0, color));
    let dir = (to - from).normalized();
    let perp = Vec2::new(-dir.y, dir.x);
    let tip = to - dir * (NODE_W / 2.0 + 4.0);
    let base = tip - dir * 10.0;
    painter.add(egui::Shape::convex_polygon(vec![tip, base + perp * 5.0, base - perp * 5.0], color, Stroke::NONE));
}

impl Facet for DepGraphView {
    fn title(&self) -> &str {
        &self.title
    }
    fn ui(&mut self, ui: &mut Ui) {
        self.show(ui);
    }
    fn state_json(&self) -> serde_json::Value {
        serde_json::json!({
            "nodes": self.nodes.len(),
            "edges": self.edges.len(),
            "columns": self.columns().iter().copied().max().map(|m| m + 1).unwrap_or(0),
            "selected": self.selected.map(|i| self.nodes[i].label.clone()),
        })
    }
    /// Boxes/arrows/labels are painted from the active [`Theme`]; a node can be
    /// click-selected (drives the drill-down panel); the layered canvas takes the
    /// host's `available_size`.
    fn caps(&self) -> FacetCaps {
        FacetCaps::NONE.themeable().selectable().resizable()
    }
    fn selection_json(&self) -> serde_json::Value {
        match self.selected {
            Some(i) => serde_json::json!({ "node": self.nodes[i].label }),
            None => serde_json::Value::Null,
        }
    }
}

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

    fn node(l: &str) -> DepNode {
        DepNode { label: l.into(), sublabel: None, color: Color32::GRAY }
    }

    #[test]
    fn toposort_columns_and_state() {
        // a → b → c  (a depends on b depends on c): c leftmost, a rightmost.
        let nodes = vec![node("a"), node("b"), node("c")];
        let edges = vec![
            DepEdge { from: 0, to: 1, via: vec!["x".into()] },
            DepEdge { from: 1, to: 2, via: vec![] },
        ];
        let view = DepGraphView::new(nodes, edges);
        let cols = view.columns();
        assert!(cols[2] < cols[1] && cols[1] < cols[0], "deps to the left: {cols:?}");
        let j = view.state_json();
        assert_eq!(j["nodes"], 3);
        assert_eq!(j["edges"], 2);
        assert_eq!(j["columns"], 3);
        assert!(j["selected"].is_null());
    }
}