vectorcraft/crates/tools/src/xform/measure.rs

//! Measure tool: drag between two points to read distance, angle, dX and dY (Shift constrains to
//! 45°). The result stays on screen (and in the tool options, for agents) until the next drag; the
//! document is never changed.

use serde_json::{Value, json};
use vectorcraft_geom::{Point, Vec2};

use super::CYAN;
use crate::{Action, Cursor, Mods, Overlay, PointerEvent, PointerKind, Tool, ToolContext};

#[derive(Default)]
pub struct MeasureTool {
    line: Option<(Point, Point)>,
    dragging: bool,
}

/// (distance, angle in degrees counter-clockwise, dx, dy)
pub fn measure(a: Point, b: Point) -> (f64, f64, f64, f64) {
    let d = b - a;
    (d.hypot(), (-d.y).atan2(d.x).to_degrees(), d.x, d.y)
}

impl Tool for MeasureTool {
    fn id(&self) -> &'static str {
        "measure"
    }

    fn busy(&self) -> bool {
        self.dragging
    }

    fn pointer(&mut self, cx: &ToolContext, ev: &PointerEvent) -> Vec<Action> {
        match ev.kind {
            PointerKind::Down => {
                let (p, _) = crate::guides::snap_draw(cx, ev.pos, &[]);
                self.line = Some((p, p));
                self.dragging = true;
            }
            PointerKind::Drag | PointerKind::Up if self.dragging => {
                if let Some((a, _)) = self.line {
                    let b = if ev.mods.shift {
                        a + vectorcraft_geom::constrain_angle(ev.pos - a, 45.0)
                    } else {
                        crate::guides::snap_draw(cx, ev.pos, &[]).0
                    };
                    self.line = Some((a, b));
                }
                self.dragging = ev.kind == PointerKind::Drag;
            }
            _ => {}
        }
        vec![]
    }

    fn overlays(&self, cx: &ToolContext) -> Vec<Overlay> {
        let Some((a, b)) = self.line else { return vec![] };
        if a == b {
            return vec![];
        }
        let (dist, ang, dx, dy) = measure(a, b);
        vec![
            Overlay::Line { a, b, color: CYAN, dashed: false },
            Overlay::Measure {
                p: b + Vec2::new(cx.tol(12.0), cx.tol(12.0)),
                text: format!("D: {}\nAngle: {ang:.1}°\n{}", cx.len(dist), cx.offset_label(dx, dy)),
            },
        ]
    }

    fn cursor(&self, _cx: &ToolContext, _p: Point, _m: Mods) -> Cursor {
        Cursor::Crosshair
    }

    fn options(&self) -> Value {
        match self.line {
            Some((a, b)) => {
                let (d, ang, dx, dy) = measure(a, b);
                json!({ "x": a.x, "y": a.y, "distance": d, "angle": ang, "dx": dx, "dy": dy })
            }
            None => Value::Null,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::testutil::*;
    use vectorcraft_doc::Selection;

    #[test]
    fn drag_reports_distance_and_angle() {
        let (d, _) = doc_with_rect();
        let s = Selection::default();
        let p = paint();
        let mut cx = cx(&d, &s, &p);
        cx.smart_guides = false;
        let mut t = MeasureTool::default();
        assert!(t.pointer(&cx, &PointerEvent::new(PointerKind::Down, 10.0, 10.0)).is_empty());
        assert!(t.pointer(&cx, &PointerEvent::new(PointerKind::Drag, 40.0, -30.0)).is_empty());
        assert!(t.pointer(&cx, &PointerEvent::new(PointerKind::Up, 40.0, -30.0)).is_empty());
        let o = t.options();
        assert!((o["distance"].as_f64().unwrap() - 50.0).abs() < 1e-9);
        assert!((o["angle"].as_f64().unwrap() - 53.130102).abs() < 1e-4);
        let ov = t.overlays(&cx);
        assert!(matches!(&ov[1], Overlay::Measure { text, .. } if text.starts_with("D: 50.00 pt")));
    }
}