//! Sketch dimensions drawn as dimensions: extension lines from the measured geometry, a
//! dimension line (or arc) with arrowheads, and the value centred on it; radius and diameter
//! leaders with R / Ø, angles as an arc between the two lines, arc lengths with the arc mark,
//! driven (reference) dimensions in parentheses in a muted colour. The geometry comes from
//! `solvecraft_sketch::dim_layout`.
//!
//! A click selects a dimension (Delete removes it), a drag moves its text (and so the offset of
//! its dimension line), a double-click edits its value in place with parameter completion.
//! Everything acts through commands: `sketch.dimension_text`, `sketch.delete`,
//! `ChangeParameterCommand`.

use std::cell::RefCell;

use egui::{FontId, Pos2, Rect, Shape, Stroke, vec2};
use serde_json::json;
use solvecraft_engine::Sel;
use solvecraft_engine::geom::Vec2;
use solvecraft_engine::sketch::{ConstraintKind, DimFrame, chain_centres, default_text, dim_frame, dim_layout};

use crate::SolveApp;
use crate::theme::Tokens;
use crate::viewport::Proj;

/// A dimension as drawn this frame (screen space), for hit testing.
#[derive(Clone, Debug)]
struct Drawn {
    id: String,
    param: Option<String>,
    text: Rect,
    segs: Vec<[Pos2; 2]>,
    /// Text centre in sketch coordinates.
    at: Vec2,
}

/// The inline value editor: parameter, expression, where it sits, first frame.
#[derive(Clone, Debug)]
struct Edit {
    param: String,
    expr: String,
    /// Where it sits (None until the dimension has been drawn).
    at: Option<Pos2>,
    /// Frames left in which the box (re)takes the keyboard: the rest of the double-click
    /// that opened it must not close it.
    fresh: u8,
    /// Frames left to wait for the dimension to be drawn.
    wait: u8,
}

thread_local! {
    static DRAWN: RefCell<Vec<Drawn>> = const { RefCell::new(Vec::new()) };
    /// A text being dragged: dimension id, undo depth at the start, grab offset (sketch).
    static DRAG: RefCell<Option<(String, usize, Vec2)>> = const { RefCell::new(None) };
    static EDIT: RefCell<Option<Edit>> = const { RefCell::new(None) };
}

/// Frames the inline editor holds on to the keyboard after opening.
const FRESH: u8 = 3;

/// Pixels from a dimension line or the text box that still count as on it.
const HIT_PX: f32 = 4.0;

fn seg_dist(p: Pos2, a: Pos2, b: Pos2) -> f32 {
    let ab = b - a;
    let t = if ab.length_sq() > 0.0 { ((p - a).dot(ab) / ab.length_sq()).clamp(0.0, 1.0) } else { 0.0 };
    p.distance(a + ab * t)
}

/// The dimension whose value text is under a screen position (its id).
pub fn hit_text(pos: Pos2) -> Option<String> {
    DRAWN.with(|d| d.borrow().iter().find(|x| x.text.expand(2.0).contains(pos)).map(|x| x.id.clone()))
}

/// The dimension under a screen position (its id).
pub fn hit(pos: Pos2) -> Option<String> {
    DRAWN.with(|d| {
        let d = d.borrow();
        // Text boxes first (they sit on top of the lines), then the lines.
        d.iter()
            .find(|x| x.text.expand(2.0).contains(pos))
            .or_else(|| d.iter().find(|x| x.segs.iter().any(|s| seg_dist(pos, s[0], s[1]) <= HIT_PX)))
            .map(|x| x.id.clone())
    })
}

/// The selected dimensions (constraint ids; they are in the session's selection).
pub fn selected(app: &SolveApp) -> Vec<String> {
    let dims: Vec<String> = DRAWN.with(|d| d.borrow().iter().map(|x| x.id.clone()).collect());
    app.session
        .selection
        .iter()
        .filter_map(|s| if let Sel::SketchConstraint { id } = s { Some(id.clone()) } else { None })
        .filter(|id| dims.contains(id))
        .collect()
}

/// Where the dimension driven by parameter `param` (or with constraint id `param`) shows its
/// value (screen), as drawn last frame.
pub fn text_at(param: &str) -> Option<Pos2> {
    DRAWN.with(|d| d.borrow().iter().find(|x| x.param.as_deref() == Some(param) || x.id == param).map(|x| x.text.center()))
}

/// Dimension text boxes drawn last frame (for box selection).
pub fn text_rects() -> Vec<(String, Rect)> {
    DRAWN.with(|d| d.borrow().iter().map(|x| (x.id.clone(), x.text)).collect())
}

/// A double-click on a dimension opens its value for editing (true: it was on one).
pub fn double_click(app: &mut SolveApp, pos: Pos2) -> bool {
    let Some(d) = DRAWN.with(|d| {
        let id = hit(pos)?;
        d.borrow().iter().find(|x| x.id == id).cloned()
    }) else {
        return false;
    };
    let Some(param) = d.param else {
        app.set_status("A driven dimension measures the sketch; it has no value to edit", false);
        return true;
    };
    let expr = app.session.doc.param(&param).map(|p| p.expr.clone()).unwrap_or_default();
    EDIT.with(|e| *e.borrow_mut() = Some(Edit { param, expr, at: Some(d.text.center()), fresh: FRESH, wait: 0 }));
    true
}

/// Start dragging the text of the dimension under `press` (true: a dimension took the drag).
pub fn drag_start(app: &SolveApp, press: Pos2, press_sketch: Vec2) -> bool {
    let Some(d) = DRAWN.with(|d| {
        let id = hit(press)?;
        d.borrow().iter().find(|x| x.id == id).cloned()
    }) else {
        return false;
    };
    DRAG.with(|g| *g.borrow_mut() = Some((d.id, app.session.undo.len(), d.at - press_sketch)));
    true
}

/// Is a dimension text being dragged?
pub fn dragging() -> bool {
    DRAG.with(|g| g.borrow().is_some())
}

/// Move the dragged text so it follows the pointer (at `to`, sketch coordinates); one undo
/// step for the whole drag.
pub fn drag_to(app: &mut SolveApp, to: Vec2) {
    let Some((id, depth, off)) = DRAG.with(|g| g.borrow().clone()) else { return };
    let at = to + off;
    if app.session.execute("sketch.dimension_text", &json!({"dimension": id, "at": [at.x, at.y]})).is_ok() {
        app.session.undo.truncate(depth + 1);
    }
}

pub fn drag_end() {
    DRAG.with(|g| *g.borrow_mut() = None);
}

/// The text shown for a dimension: the value (R / Ø for radius and diameter, degrees for
/// angles), "fx: value" when an expression drives it, in parentheses when driven.
pub fn label(k: &ConstraintKind, expr: Option<&str>, driven: bool) -> String {
    let v = k.value().unwrap_or(0.0);
    let num = if k.is_angle() { format!("{:.1}°", v.to_degrees()) } else { format!("{v:.2}") };
    let num = match k {
        ConstraintKind::Radius { .. } => format!("R{num}"),
        ConstraintKind::Diameter { .. } | ConstraintKind::LinearDiameter { .. } => format!("Ø{num}"),
        _ => num,
    };
    let plain = expr.is_none_or(|e| {
        let e = e.trim();
        let e = e.strip_suffix("mm").or_else(|| e.strip_suffix("deg")).or_else(|| e.strip_suffix('°')).unwrap_or(e);
        e.trim().parse::<f64>().is_ok()
    });
    let text = if plain { num } else { format!("fx: {num}") };
    if driven { format!("({text})") } else { text }
}

/// Draw the active sketch's dimensions and remember where they are for picking.
pub fn show(app: &mut SolveApp, ui: &egui::Ui, painter: &egui::Painter, proj: &Proj) {
    let mut drawn = Vec::new();
    let st = app.session.world_state();
    let Some(ss) = app.session.active_sketch.and_then(|s| st.sketch(s)) else {
        DRAWN.with(|d| d.borrow_mut().clear());
        EDIT.with(|e| *e.borrow_mut() = None);
        return;
    };
    let sk = &ss.sketch;
    if sk.view.hide_dimensions {
        DRAWN.with(|d| d.borrow_mut().clear());
        return;
    }
    let tk = Tokens::get();
    let is_sel = |id: &str| app.session.selection.iter().any(|s| matches!(s, Sel::SketchConstraint { id: x } if x == id));
    let hover = ui.input(|i| i.pointer.hover_pos()).filter(|p| proj.rect.contains(*p)).and_then(hit);
    let to = |p: Vec2| proj.to_screen(ss.plane.to_world(p));
    let font = FontId::proportional(12.0);
    let centres = chain_centres(sk);
    for c in &sk.constraints {
        let Some(frame) = dim_frame(sk, &c.kind) else { continue };
        let anchor = match frame {
            DimFrame::Linear { p0, p1, .. } => (p0 + p1) * 0.5,
            DimFrame::Radial { center, .. } | DimFrame::ArcLength { center, .. } => center,
            DimFrame::Angular { vertex, .. } => vertex,
        };
        // Millimetres per pixel at the dimension.
        let (Some(a), Some(b)) = (to(anchor), to(anchor + Vec2::X)) else { continue };
        let px = 1.0 / f64::from(a.distance(b)).max(1e-9);
        if !px.is_finite() {
            continue;
        }
        let expr = c.param.as_ref().and_then(|p| app.session.doc.param(p)).map(|p| p.expr.as_str());
        let failing = ss.report.failing.contains(&c.id);
        let col = if failing {
            tk.error
        } else if is_sel(&c.id) || hover.as_deref() == Some(c.id.as_str()) {
            tk.accent
        } else if c.driven {
            tk.dimension_driven
        } else {
            tk.dimension
        };
        let galley = painter.layout_no_wrap(label(&c.kind, expr, c.driven), font.clone(), col);
        let size = galley.size() + vec2(6.0, 2.0);
        let half = Vec2::new(f64::from(size.x) * 0.5 * px, f64::from(size.y) * 0.5 * px);
        // Unplaced linear dimensions sit outside the shape they measure.
        let away = first_point(sk, &c.kind).and_then(|p| centres.get(p).copied()).unwrap_or(anchor);
        let lay = dim_layout(&frame, c.text.or_else(|| default_text(&frame, away, px)), px, half);
        let stroke = Stroke::new(1.0, col);
        let mut segs = Vec::new();
        for line in &lay.lines {
            let pts: Vec<Pos2> = line.iter().filter_map(|q| to(*q)).collect();
            for w in pts.windows(2) {
                segs.push([w[0], w[1]]);
            }
            painter.add(Shape::line(pts, stroke));
        }
        for (tip, dir) in &lay.arrows {
            if let (Some(t), Some(back)) = (to(*tip), to(*tip - *dir * px)) {
                let d = (t - back).normalized();
                let n = vec2(-d.y, d.x);
                painter.add(Shape::convex_polygon(vec![t, t - d * 9.0 + n * 3.0, t - d * 9.0 - n * 3.0], col, Stroke::NONE));
            }
        }
        let Some(tc) = to(lay.text) else { continue };
        let r = Rect::from_center_size(tc, size);
        painter.rect_filled(r, 2.0, tk.viewport_top.gamma_multiply(0.85));
        painter.galley(r.min + vec2(3.0, 1.0), galley, col);
        if matches!(frame, DimFrame::ArcLength { .. }) {
            // The arc-length mark over the value.
            let c0 = pos2_mid_top(r);
            let pts: Vec<Pos2> = (0..=12)
                .map(|i| c0 + vec2(5.0 * (std::f32::consts::PI * i as f32 / 12.0).cos(), -3.0 * (std::f32::consts::PI * i as f32 / 12.0).sin()))
                .collect();
            painter.add(Shape::line(pts, stroke));
        }
        drawn.push(Drawn { id: c.id.clone(), param: c.param.clone(), text: r, segs, at: lay.text });
    }
    DRAWN.with(|d| *d.borrow_mut() = drawn);
    edit_box(app, ui.ctx());
}

/// A point a dimension measures (for the shape it belongs to).
fn first_point(sk: &solvecraft_engine::sketch::Sketch, k: &ConstraintKind) -> Option<usize> {
    use ConstraintKind::*;
    match *k {
        Length { l, .. } => sk.curves.get(l).and_then(|c| c.kind.point_ids().first().copied()),
        Distance { p, .. } | DistanceX { p, .. } | DistanceY { p, .. } | PointLineDistance { p, .. } | LinearDiameter { p, .. } => Some(p),
        _ => None,
    }
}

fn pos2_mid_top(r: Rect) -> Pos2 {
    Pos2::new(r.center().x, r.top() - 1.0)
}

/// The inline value editor: Enter applies, Esc (or a click elsewhere) cancels.
/// Edit a dimension's value in place by its parameter (a new dimension from the Dimension tool:
/// its value is selected, so typing replaces it).
pub fn edit_param(app: &SolveApp, param: &str) {
    let expr = app.session.doc.param(param).map(|p| p.expr.clone()).unwrap_or_default();
    EDIT.with(|e| *e.borrow_mut() = Some(Edit { param: param.to_string(), expr, at: None, fresh: FRESH, wait: 10 }));
}

fn edit_box(app: &mut SolveApp, ctx: &egui::Context) {
    let Some(mut e) = EDIT.with(|x| x.borrow_mut().take()) else { return };
    if e.at.is_none() {
        e.at = DRAWN.with(|d| d.borrow().iter().find(|x| x.param.as_deref() == Some(e.param.as_str())).map(|x| x.text.center()));
    }
    let Some(at) = e.at else {
        // Not drawn yet (this frame's solve): try again next frame, for a few frames.
        if e.wait > 0 {
            e.wait -= 1;
            EDIT.with(|x| *x.borrow_mut() = Some(e));
        }
        return;
    };
    let id = egui::Id::new("sc_dim_edit");
    let mut done: Option<bool> = None;
    egui::Area::new(egui::Id::new("sc_dim_edit_area")).fixed_pos(at - vec2(45.0, 11.0)).order(egui::Order::Foreground).show(ctx, |ui| {
        egui::Frame::popup(ui.style()).inner_margin(egui::Margin::symmetric(3, 1)).show(ui, |ui| {
            let r = ui.add(egui::TextEdit::singleline(&mut e.expr).id(id).desired_width(90.0));
            crate::params_dialog::complete(ui, &r, &mut e.expr);
            if e.fresh == FRESH {
                // The whole value is selected, so typing replaces it.
                let n = e.expr.chars().count();
                let mut s = egui::text_edit::TextEditState::load(ui.ctx(), id).unwrap_or_default();
                s.cursor.set_char_range(Some(egui::text_selection::CCursorRange::two(egui::text::CCursor::new(0), egui::text::CCursor::new(n))));
                s.store(ui.ctx(), id);
            }
            let enter = ui.input(|i| i.key_pressed(egui::Key::Enter));
            if r.lost_focus() && enter {
                done = Some(true);
            } else if e.fresh > 0 {
                if !r.has_focus() {
                    r.request_focus();
                }
            } else if r.lost_focus() {
                done = Some(false);
            }
            if ui.input(|i| i.key_pressed(egui::Key::Escape)) {
                done = Some(false);
            }
        });
    });
    e.fresh = e.fresh.saturating_sub(1);
    match done {
        Some(true) => {
            if let Err(err) = app.run("ChangeParameterCommand", json!({"name": e.param, "expression": e.expr})) {
                app.set_status(err, true);
                EDIT.with(|x| *x.borrow_mut() = Some(Edit { fresh: FRESH, ..e }));
            }
        }
        Some(false) => {}
        None => EDIT.with(|x| *x.borrow_mut() = Some(e)),
    }
}

/// Is the inline editor open (it has the keyboard)?
pub fn editing() -> bool {
    EDIT.with(|e| e.borrow().is_some())
}

/// Dimensions drawn last frame: (id, text centre on screen), for tests and the control channel.
pub fn drawn() -> Vec<(String, Pos2)> {
    DRAWN.with(|d| d.borrow().iter().map(|x| (x.id.clone(), x.text.center())).collect())
}

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

    #[test]
    fn labels_show_the_value_or_fx() {
        let k = ConstraintKind::Length { l: 0, value: 25.0 };
        assert_eq!(label(&k, Some("25 mm"), false), "25.00");
        assert_eq!(label(&k, Some("width * 2"), false), "fx: 25.00");
        assert_eq!(label(&k, None, true), "(25.00)");
        assert_eq!(label(&ConstraintKind::Radius { c: 0, value: 5.0 }, Some("5 mm"), false), "R5.00");
        assert_eq!(label(&ConstraintKind::Diameter { c: 0, value: 10.0 }, Some("10"), false), "Ø10.00");
        let a = ConstraintKind::Angle { a: 0, b: 1, value: std::f64::consts::FRAC_PI_4, flip: false };
        assert_eq!(label(&a, Some("45 deg"), false), "45.0°");
    }
}