//! The window's own title bar on Windows and Linux, where the window has no OS decorations
//! ([`SolveApp::custom_titlebar`]): empty space in the application bar drags the window and a
//! double-click there maximizes or restores it, caption buttons at the far right minimize,
//! maximize/restore and close, and thin invisible zones along the window's edges resize it.
//! Dragging uses the OS's own move loop, so Windows snapping (to the screen edges and corners)
//! works as with a native title bar.
//!
//! The resize zones are as wide as Windows' own resize border at the window's scale
//! ([`resize_border_px`]), corners win where they overlap the edges ([`resize_hit`]). On Windows
//! the desktop app answers the system's hit test with them (`apps/solidcraft/src/native_frame.rs`),
//! so the OS shows its resize cursors and resizes from the first frame; elsewhere egui zones above
//! everything else start an OS resize ([`resize_zones`]). macOS keeps its traffic lights over the bar
//! ([`SolveApp::integrated_titlebar`]); the web build has neither.
//!
//! Adapted from VectorCraft's `crates/ui-egui/src/titlebar.rs` (MIT OR Apache-2.0).

use crate::icons::glyphs::paint_glyph;
use egui::{Color32, CursorIcon, Id, LayerId, Order, PointerButton, Pos2, Rect, ResizeDirection, Sense, Stroke, Ui, ViewportCommand, pos2, vec2};

use crate::SolveApp;
use crate::theme::Tokens;

/// One caption button: as wide as the native Windows ones.
pub const BUTTON_WIDTH: f32 = 46.0;
/// The three caption buttons together.
pub const WIDTH: f32 = 3.0 * BUTTON_WIDTH;
/// Room for the macOS traffic lights at the bar's left end.
pub const TRAFFIC_LIGHTS: f32 = 76.0;
/// Windows' resize border at 100 % (96 DPI): `SM_CXSIZEFRAME` + `SM_CXPADDEDBORDER`, 4 + 4 px.
pub const RESIZE_BORDER_AT_96_DPI: f32 = 8.0;
/// The Close button's hover colour (as on Windows).
const CLOSE_HOVER: Color32 = Color32::from_rgb(196, 43, 28);

#[derive(Clone, Copy, PartialEq, Debug)]
pub enum Caption {
    Minimize,
    Maximize,
    Close,
}

/// Left to right.
pub const CAPTIONS: [Caption; 3] = [Caption::Minimize, Caption::Maximize, Caption::Close];

/// Caption button ids (stable, so tests and agents can find them).
pub fn caption_id(c: Caption) -> Id {
    Id::new(("titlebar-caption", c as u8))
}

fn maximized(ctx: &egui::Context) -> bool {
    ctx.input(|i| i.viewport().maximized.unwrap_or(false))
}

pub fn toggle_maximize(ctx: &egui::Context) {
    ctx.send_viewport_cmd(ViewportCommand::Maximized(!maximized(ctx)));
}

/// Window actions for the control channel (`ui.window`): minimize, maximize, restore, toggle
/// (maximize or restore), close.
pub fn window_action(app: &mut SolveApp, ctx: &egui::Context, action: &str) -> Result<(), String> {
    match action {
        "minimize" => ctx.send_viewport_cmd(ViewportCommand::Minimized(true)),
        "maximize" => ctx.send_viewport_cmd(ViewportCommand::Maximized(true)),
        "restore" => ctx.send_viewport_cmd(ViewportCommand::Maximized(false)),
        "toggle" => toggle_maximize(ctx),
        "close" => {
            // Unsaved designs are asked about first; the window closes once they are answered.
            crate::documents::request_quit(app);
            if app.quit_requested {
                ctx.send_viewport_cmd(ViewportCommand::Close);
            }
        }
        other => return Err(format!("unknown window action `{other}` (minimize, maximize, restore, toggle, close)")),
    }
    Ok(())
}

/// The bar's background: a press-and-drag on empty space moves the window, a double-click
/// toggles maximize. Call it before laying out the bar so its buttons, registered later, take
/// their clicks.
pub fn drag_area(ui: &Ui, rect: Rect) {
    let ctx = ui.ctx();
    let resp = ui.interact(rect, Id::new("titlebar-drag"), Sense::click_and_drag());
    // egui hands a drag that starts on a click-only widget to the drag-sensing background below
    // it, so remember whether the press itself landed on bare background.
    if ctx.input(|i| i.pointer.any_pressed()) {
        let bare = ctx.viewport(|v| v.hits.click.is_some_and(|w| w.id == resp.id));
        ctx.data_mut(|d| d.insert_temp(resp.id, bare));
    }
    if resp.double_clicked() {
        toggle_maximize(ctx);
    } else if resp.drag_started_by(PointerButton::Primary) && ctx.data(|d| d.get_temp(resp.id).unwrap_or(false)) {
        ctx.send_viewport_cmd(ViewportCommand::StartDrag);
    }
}

/// Minimize, Maximize/Restore and Close at the right end of `bar` (the application bar's
/// rect), full bar height, flush with the window's edge so a maximized window's corner hits
/// Close.
pub fn caption_buttons(app: &mut SolveApp, ui: &mut Ui, bar: Rect) {
    let t = Tokens::get();
    let max = maximized(ui.ctx());
    let mut clicked = None;
    for (i, c) in CAPTIONS.into_iter().enumerate() {
        let r = Rect::from_min_size(pos2(bar.right() - WIDTH + i as f32 * BUTTON_WIDTH, bar.top()), vec2(BUTTON_WIDTH, bar.height()));
        let resp = ui.interact(r, caption_id(c), Sense::click());
        let close = c == Caption::Close;
        let fill = match (resp.is_pointer_button_down_on(), resp.hovered()) {
            (true, _) if close => CLOSE_HOVER.gamma_multiply(0.8),
            (_, true) if close => CLOSE_HOVER,
            (true, _) => Color32::from_white_alpha(18),
            (_, true) => Color32::from_white_alpha(30),
            _ => Color32::TRANSPARENT,
        };
        ui.painter().rect_filled(r, 0.0, fill);
        let ink = if close && resp.hovered() { Color32::WHITE } else { t.app_bar_text };
        paint_glyph(ui, c, max, r.center(), Stroke::new(1.0, ink));
        let tip = match c {
            Caption::Minimize => "Minimize",
            Caption::Maximize if max => "Restore",
            Caption::Maximize => "Maximize",
            Caption::Close => "Close",
        };
        if resp.on_hover_text(tip).clicked() {
            clicked = Some(c);
        }
    }
    let action = match clicked {
        Some(Caption::Minimize) => "minimize",
        Some(Caption::Maximize) => "toggle",
        Some(Caption::Close) => "close",
        None => return,
    };
    let _ = window_action(app, &ui.ctx().clone(), action);
}

/// The resize border in physical pixels at `scale` (1.0 = 96 DPI): Windows' default, scaled and
/// rounded, never less than a pixel.
pub fn resize_border_px(scale: f32) -> f32 {
    let s = if scale.is_finite() && scale > 0.0 { scale } else { 1.0 };
    (RESIZE_BORDER_AT_96_DPI * s).round().max(1.0)
}

/// The side of a corner zone for an edge `edge` wide: twice the edge, so a corner is easy to hit.
pub fn corner_size(edge: f32) -> f32 {
    2.0 * edge
}

/// The edge and corner zones of a window with rect `w`, edges `edge` wide: (zone, direction,
/// cursor). Corners come last so they win where they overlap the edges.
pub fn zones(w: Rect, edge: f32) -> [(Rect, ResizeDirection, CursorIcon); 8] {
    use ResizeDirection::*;
    let (e, c) = (edge, corner_size(edge));
    [
        (Rect::from_min_max(w.left_top(), pos2(w.right(), w.top() + e)), North, CursorIcon::ResizeVertical),
        (Rect::from_min_max(pos2(w.left(), w.bottom() - e), w.right_bottom()), South, CursorIcon::ResizeVertical),
        (Rect::from_min_max(w.left_top(), pos2(w.left() + e, w.bottom())), West, CursorIcon::ResizeHorizontal),
        (Rect::from_min_max(pos2(w.right() - e, w.top()), w.right_bottom()), East, CursorIcon::ResizeHorizontal),
        (Rect::from_min_size(w.left_top(), vec2(c, c)), NorthWest, CursorIcon::ResizeNwSe),
        (Rect::from_min_size(w.right_top() - vec2(c, 0.0), vec2(c, c)), NorthEast, CursorIcon::ResizeNeSw),
        (Rect::from_min_size(w.left_bottom() - vec2(0.0, c), vec2(c, c)), SouthWest, CursorIcon::ResizeNeSw),
        (Rect::from_min_size(w.right_bottom() - vec2(c, c), vec2(c, c)), SouthEast, CursorIcon::ResizeNwSe),
    ]
}

/// The resize direction at `p` in a window with rect `w` and edges `edge` wide, `None` away
/// from the edges and outside the window. A point is in the window when `min <= p < max` (pixel
/// rects: the right and bottom pixels are at `max - 1`). Corners win over edges.
pub fn resize_hit(w: Rect, p: Pos2, edge: f32) -> Option<ResizeDirection> {
    if !(w.is_positive() && edge > 0.0 && p.x >= w.left() && p.x < w.right() && p.y >= w.top() && p.y < w.bottom()) {
        return None;
    }
    zones(w, edge).into_iter().rev().find(|(r, ..)| p.x >= r.left() && p.x < r.right() && p.y >= r.top() && p.y < r.bottom()).map(|(_, d, _)| d)
}

/// The window's new physical size when it moves from `old_dpi` to `new_dpi` (Windows'
/// `WM_GETDPISCALEDSIZE`): the same logical size, rounded as winit rounds the size it then
/// applies, so the rect the OS suggests mid-move is exactly the rect the window gets.
pub fn dpi_scaled_size(size: (i32, i32), old_dpi: u32, new_dpi: u32) -> Option<(i32, i32)> {
    if old_dpi == 0 || new_dpi == 0 || size.0 <= 0 || size.1 <= 0 {
        return None;
    }
    let (old, new) = (f64::from(old_dpi) / 96.0, f64::from(new_dpi) / 96.0);
    let scale = |v: i32| (f64::from(v) / old * new).round().clamp(1.0, f64::from(i32::MAX)) as i32;
    Some((scale(size.0), scale(size.1)))
}

/// Invisible resize zones along the window's edges, above everything else; a press in one
/// starts an OS resize in that direction. None while the window is maximized or fullscreen.
pub fn resize_zones(ui: &mut Ui) {
    let ctx = ui.ctx().clone();
    if maximized(&ctx) || ctx.input(|i| i.viewport().fullscreen.unwrap_or(false)) {
        return;
    }
    let w = ctx.content_rect();
    let ppp = ctx.pixels_per_point();
    let edge = resize_border_px(ctx.input(|i| i.viewport().native_pixels_per_point).unwrap_or(ppp)) / ppp;
    let layer = LayerId::new(Order::Foreground, Id::new("titlebar-resize"));
    let zui = ui.new_child(egui::UiBuilder::new().layer_id(layer).max_rect(w));
    for (i, (r, dir, cursor)) in zones(w, edge).into_iter().enumerate() {
        let resp = zui.interact(r, Id::new(("titlebar-resize", i)), Sense::drag()).on_hover_cursor(cursor);
        if resp.drag_started_by(PointerButton::Primary) {
            ctx.send_viewport_cmd(ViewportCommand::BeginResize(dir));
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use egui::{Event, Pos2, RawInput, ViewportId};
    use solidcraft_engine::Session;

    /// A headless window `width` pt wide showing the application bar (as the title bar) and the
    /// resize zones.
    struct Win {
        ctx: egui::Context,
        app: SolveApp,
        width: f32,
        time: f64,
        maximized: bool,
        /// Lay out the whole window (`SolveApp::ui`) rather than only the bar and the zones.
        full: bool,
    }

    impl Win {
        fn new(width: f32) -> Self {
            let ctx = egui::Context::default();
            let mut app = SolveApp::new(Session::default(), Default::default());
            app.custom_titlebar = true;
            Self { ctx, app, width, time: 0.0, maximized: false, full: false }
        }

        fn frame(&mut self, events: Vec<Event>) -> egui::FullOutput {
            self.time += 0.05;
            let mut input = RawInput {
                screen_rect: Some(Rect::from_min_size(Pos2::ZERO, vec2(self.width, 700.0))),
                time: Some(self.time),
                events,
                ..Default::default()
            };
            if let Some(v) = input.viewports.get_mut(&ViewportId::ROOT) {
                v.maximized = Some(self.maximized);
            }
            let (app, full) = (&mut self.app, self.full);
            let mut out = self.ctx.run_ui(input, |ui| {
                if full {
                    app.ui(ui);
                    return;
                }
                crate::toolbar::app_bar(app, ui);
                if app.custom_titlebar {
                    resize_zones(ui);
                }
            });
            out.textures_delta.clear();
            out
        }

        /// Frames for a pointer gesture: move to `path[0]`, press, move along `path`, release.
        /// The viewport commands the frames sent.
        fn gesture(&mut self, path: &[Pos2]) -> Vec<ViewportCommand> {
            let button = |p: Pos2, pressed| Event::PointerButton { pos: p, button: PointerButton::Primary, pressed, modifiers: Default::default() };
            let mut events = vec![vec![Event::PointerMoved(path[0])], vec![button(path[0], true)]];
            events.extend(path[1..].iter().map(|p| vec![Event::PointerMoved(*p)]));
            events.push(vec![button(*path.last().unwrap_or(&path[0]), false)]);
            events.into_iter().flat_map(|e| self.frame(e).viewport_output.remove(&ViewportId::ROOT).map(|v| v.commands).unwrap_or_default()).collect()
        }

        fn click(&mut self, p: Pos2) -> Vec<ViewportCommand> {
            self.gesture(&[p])
        }

        fn caption(&self, c: Caption) -> Rect {
            self.ctx.read_response(caption_id(c)).map(|r| r.rect).unwrap_or(Rect::NOTHING)
        }
    }

    fn texts(out: &egui::FullOutput) -> Vec<(String, Rect)> {
        fn walk(s: &egui::Shape, v: &mut Vec<(String, Rect)>) {
            match s {
                egui::Shape::Text(t) => v.push((t.galley.text().to_string(), Rect::from_min_size(t.pos, t.galley.size()))),
                egui::Shape::Vec(s) => s.iter().for_each(|s| walk(s, v)),
                _ => {}
            }
        }
        let mut v = vec![];
        out.shapes.iter().for_each(|c| walk(&c.shape, &mut v));
        v
    }

    #[test]
    fn caption_buttons_sit_in_the_corner_and_nothing_runs_under_them() {
        for width in [960.0, 1600.0] {
            let mut w = Win::new(width);
            w.frame(vec![]);
            let out = w.frame(vec![]);
            let [min, max, close] = CAPTIONS.map(|c| w.caption(c));
            assert_eq!((close.right(), close.top()), (width, 0.0), "Close sits in the window's corner at {width}");
            assert!([min, max, close].iter().all(|r| r.width() == BUTTON_WIDTH));
            assert_eq!((min.right(), max.right()), (max.left(), close.left()));
            let texts = texts(&out);
            let version = texts.iter().find(|(t, _)| t.starts_with('v')).map(|(_, r)| *r);
            assert!(version.is_some_and(|r| r.right() <= min.left() - 4.0), "the version stays left of the buttons: {version:?}");
            for (t, r) in &texts {
                assert!(r.right() <= min.left() || r.top() >= min.bottom(), "`{t}` runs under the caption buttons at {width}");
            }
        }
    }

    #[test]
    fn no_caption_buttons_without_a_custom_title_bar() {
        let mut w = Win::new(1200.0);
        w.app.custom_titlebar = false;
        w.frame(vec![]);
        w.frame(vec![]);
        assert_eq!(w.caption(Caption::Close), Rect::NOTHING);
    }

    #[test]
    fn minimize_maximize_and_close() {
        let mut w = Win::new(1200.0);
        w.frame(vec![]);
        let (min, max, close) = (w.caption(Caption::Minimize).center(), w.caption(Caption::Maximize).center(), w.caption(Caption::Close).center());
        assert!(w.click(min).contains(&ViewportCommand::Minimized(true)));
        assert!(w.click(max).contains(&ViewportCommand::Maximized(true)));
        w.maximized = true;
        assert!(w.click(max).contains(&ViewportCommand::Maximized(false)), "Restore");
        assert!(w.click(close).contains(&ViewportCommand::Close));
        assert!(w.app.quit_requested);
    }

    #[test]
    fn empty_bar_space_drags_and_double_click_maximizes() {
        let mut w = Win::new(1600.0);
        w.frame(vec![]);
        let empty = pos2(900.0, 17.0);
        let cmds = w.gesture(&[empty, empty + vec2(12.0, 4.0), empty + vec2(30.0, 8.0)]);
        assert_eq!(cmds.iter().filter(|c| matches!(c, ViewportCommand::StartDrag)).count(), 1, "{cmds:?}");
        let mut cmds = w.click(empty);
        cmds.extend(w.click(empty));
        assert!(cmds.contains(&ViewportCommand::Maximized(true)), "{cmds:?}");
        w.maximized = true;
        w.time += 1.0;
        let mut cmds = w.click(empty);
        cmds.extend(w.click(empty));
        assert!(cmds.contains(&ViewportCommand::Maximized(false)), "{cmds:?}");
        // The bar's buttons keep their clicks: dragging from Undo doesn't move the window.
        w.time += 1.0;
        let undo = crate::scenario::handle_at("appbar:undo").unwrap();
        let cmds = w.gesture(&[undo, undo + vec2(12.0, 4.0), undo + vec2(30.0, 8.0)]);
        assert!(!cmds.iter().any(|c| matches!(c, ViewportCommand::StartDrag)), "{cmds:?}");
    }

    #[test]
    fn edge_zones_resize_unless_maximized() {
        use ResizeDirection::*;
        let mut w = Win::new(1000.0);
        w.frame(vec![]);
        for (p, dir) in [
            (pos2(1.0, 300.0), West),
            (pos2(998.0, 300.0), East),
            (pos2(500.0, 1.0), North),
            (pos2(500.0, 698.0), South),
            (pos2(2.0, 2.0), NorthWest),
            (pos2(997.0, 3.0), NorthEast),
            (pos2(3.0, 697.0), SouthWest),
            (pos2(998.0, 698.0), SouthEast),
        ] {
            let cmds = w.gesture(&[p, p + vec2(6.0, 6.0)]);
            assert_eq!(cmds, vec![ViewportCommand::BeginResize(dir)], "at {p:?}");
        }
        w.maximized = true;
        let cmds = w.gesture(&[pos2(1.0, 300.0), pos2(8.0, 300.0)]);
        assert!(!cmds.iter().any(|c| matches!(c, ViewportCommand::BeginResize(_))), "{cmds:?}");
    }

    #[test]
    fn resize_border_is_windows_default_for_the_scale() {
        for (dpi, px) in [(96.0, 8.0), (120.0, 10.0), (144.0, 12.0), (168.0, 14.0), (192.0, 16.0), (288.0, 24.0)] {
            assert_eq!(resize_border_px(dpi / 96.0), px, "at {dpi} DPI");
        }
        // Never 0 px, whatever the scale says.
        for bad in [0.0, -1.0, f32::NAN, f32::INFINITY] {
            assert_eq!(resize_border_px(bad), 8.0, "{bad}");
        }
        assert_eq!(resize_border_px(0.01), 1.0);
        assert_eq!(corner_size(resize_border_px(1.5)), 24.0);
    }

    #[test]
    fn hit_test_edges_corners_and_inside() {
        use ResizeDirection::*;
        // A window at (100, 50), 1000 x 700 px, at 150 %: 12 px edges, 24 px corners.
        let w = Rect::from_min_size(pos2(100.0, 50.0), vec2(1000.0, 700.0));
        let e = resize_border_px(1.5);
        let (l, t, r, b) = (100.0, 50.0, 1099.0, 749.0); // the outermost pixels
        for (p, want) in [
            ((l, 400.0), Some(West)),
            ((l + 11.0, 400.0), Some(West)),
            ((l + 12.0, 400.0), None),
            ((r, 400.0), Some(East)),
            ((r - 11.0, 400.0), Some(East)),
            ((r - 12.0, 400.0), None),
            ((600.0, t), Some(North)),
            ((600.0, t + 12.0), None),
            ((600.0, b), Some(South)),
            ((600.0, b - 11.0), Some(South)),
            ((l, t), Some(NorthWest)),
            ((r, t), Some(NorthEast)),
            ((l, b), Some(SouthWest)),
            ((r, b), Some(SouthEast)),
            // Corners win over the edges, along both edges for the corner's length.
            ((l + 23.0, t), Some(NorthWest)),
            ((l, t + 23.0), Some(NorthWest)),
            ((l + 24.0, t), Some(North)),
            ((l, t + 24.0), Some(West)),
            ((r - 23.0, b), Some(SouthEast)),
            ((r, b - 23.0), Some(SouthEast)),
            ((r - 23.0, t), Some(NorthEast)),
            ((l, b - 23.0), Some(SouthWest)),
            ((600.0, 400.0), None),
            // Outside the window: not ours.
            ((l - 1.0, 400.0), None),
            ((r + 1.0, 400.0), None),
            ((600.0, t - 1.0), None),
            ((600.0, b + 1.0), None),
        ] {
            assert_eq!(resize_hit(w, pos2(p.0, p.1), e), want, "at {p:?}");
        }
        assert_eq!(resize_hit(w, pos2(l, 400.0), 0.0), None);
        assert_eq!(resize_hit(Rect::NOTHING, pos2(l, 400.0), e), None);
        // Every DPI has a zone on every edge.
        for dpi in [96.0, 120.0, 144.0, 192.0] {
            let e = resize_border_px(dpi / 96.0);
            for (p, d) in [((l, 400.0), West), ((r, 400.0), East), ((600.0, t), North), ((600.0, b), South)] {
                assert_eq!(resize_hit(w, pos2(p.0, p.1), e), Some(d), "{d:?} at {dpi} DPI");
            }
        }
    }

    #[test]
    fn dpi_change_keeps_the_logical_size() {
        assert_eq!(dpi_scaled_size((1600, 1000), 96, 144), Some((2400, 1500)));
        assert_eq!(dpi_scaled_size((2400, 1500), 144, 96), Some((1600, 1000)));
        assert_eq!(dpi_scaled_size((1001, 777), 120, 192), Some((1602, 1243)));
        assert_eq!(dpi_scaled_size((1001, 777), 96, 96), Some((1001, 777)));
        assert_eq!(dpi_scaled_size((1001, 777), 0, 96), None);
        assert_eq!(dpi_scaled_size((0, 777), 96, 144), None);
    }

    #[test]
    fn edges_resize_on_the_start_page() {
        // At launch without a design the start page shows; its layout returned before the
        // resize zones were laid out, so the edges did nothing until a design opened (#1381).
        let mut w = Win::new(1200.0);
        w.full = true;
        let rev = w.app.session.revision;
        w.app.home.show(rev);
        w.frame(vec![]);
        assert!(w.app.home.open);
        let p = pos2(1199.0, 350.0);
        let cmds = w.gesture(&[p, p + vec2(6.0, 0.0)]);
        assert_eq!(cmds, vec![ViewportCommand::BeginResize(ResizeDirection::East)]);
        let p = pos2(1.0, 699.0);
        let cmds = w.gesture(&[p, p + vec2(-6.0, 6.0)]);
        assert_eq!(cmds, vec![ViewportCommand::BeginResize(ResizeDirection::SouthWest)]);
        // Where the OS hit test offers the border, egui lays out no zones of its own.
        w.app.native_resize_border = true;
        let p = pos2(1199.0, 350.0);
        let cmds = w.gesture(&[p, p + vec2(6.0, 0.0)]);
        assert!(!cmds.iter().any(|c| matches!(c, ViewportCommand::BeginResize(_))), "{cmds:?}");
    }
}