use std::{cell::RefCell, rc::Rc};

use gpui::{
    Context, InteractiveElement as _, IntoElement, Modifiers, MouseMoveEvent, ParentElement as _,
    Render, StatefulInteractiveElement as _, Styled as _, TestAppContext, VisualTestContext,
    Window, WindowHandle, canvas, div, point, px,
};
use gpui_native_core::button::Button;
use gpui_native_core::tooltip::Tooltip;
use gpui_native_theme::Theme;
use gpui_native_utils::record_anchor_bounds;

/// Hover target at the top-left with a tooltip whose builder records every
/// invocation. The tooltip anchors to the target itself, so it hangs below
/// the target's bottom edge instead of at the cursor.
struct Harness {
    calls: Rc<RefCell<Vec<&'static str>>>,
}

impl Render for Harness {
    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
        let calls = self.calls.clone();
        let target = div()
            .id("hover-target")
            .debug_selector(|| "hover-target".to_string())
            .w(px(100.))
            .h(px(40.))
            .bg(gpui::black())
            .child(
                canvas(record_anchor_bounds("hover-target".into()), |_, _, _, _| {})
                    .absolute()
                    .inset_0(),
            )
            .tooltip(move |window, cx| {
                calls.borrow_mut().push("target");
                Tooltip::anchored("Target tooltip", "hover-target")(window, cx)
            });

        let button_calls = self.calls.clone();
        let button = Button::new("hover-button")
            .label("Hover me")
            .tooltip(move |window, cx| {
                button_calls.borrow_mut().push("button");
                Tooltip::anchored("Button tooltip", "hover-button")(window, cx)
            });

        div()
            .size_full()
            .child(target)
            .child(div().mt_12().child(button))
    }
}

fn tooltip_window() -> (
    TestAppContext,
    VisualTestContext,
    Rc<RefCell<Vec<&'static str>>>,
) {
    let mut cx = TestAppContext::single();
    cx.update(Theme::init);
    let calls = Rc::new(RefCell::new(Vec::new()));
    let harness_calls = calls.clone();
    let window = cx.add_window(move |_, _| Harness {
        calls: harness_calls,
    });
    let mut visual = VisualTestContext::from_window(window.into(), &cx);
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });
    (cx, visual, calls)
}

fn hover(visual: &mut VisualTestContext, position: gpui::Point<gpui::Pixels>) {
    visual.simulate_event(MouseMoveEvent {
        position,
        pressed_button: None,
        modifiers: Modifiers::default(),
    });
}

/// gpui's hover delay before deploying a tooltip.
const SHOW_DELAY: std::time::Duration = std::time::Duration::from_millis(500);

fn draw(visual: &mut VisualTestContext) {
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });
}

struct LowHarness;

impl Render for LowHarness {
    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
        // The target is pinned to the window's bottom edge: the space below it
        // is nil, so the tooltip must flip above the parent.
        div().size_full().flex().flex_col().justify_end().child(
            div()
                .id("low-target")
                .debug_selector(|| "low-target".to_string())
                .w(px(100.))
                .h(px(40.))
                .bg(gpui::black())
                .child(
                    canvas(record_anchor_bounds("low-target".into()), |_, _, _, _| {})
                        .absolute()
                        .inset_0(),
                )
                .tooltip(Tooltip::anchored("Low tooltip", "low-target")),
        )
    }
}

fn low_tooltip_window() -> (TestAppContext, VisualTestContext, WindowHandle<LowHarness>) {
    let mut cx = TestAppContext::single();
    cx.update(Theme::init);
    let window = cx.add_window(move |_, _| LowHarness);
    let mut visual = VisualTestContext::from_window(window.into(), &cx);
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });
    (cx, visual, window)
}

#[test]
fn hovering_the_target_deploys_the_tooltip_after_the_delay() {
    let (cx, mut visual, calls) = tooltip_window();
    hover(&mut visual, point(px(50.), px(20.)));
    assert!(
        calls.borrow().is_empty(),
        "builder runs only after the delay"
    );
    assert!(
        calls.borrow().is_empty(),
        "builder runs only after the delay"
    );

    cx.executor().advance_clock(SHOW_DELAY);
    visual.run_until_parked();
    draw(&mut visual);
    assert_eq!(*calls.borrow(), vec!["target"]);
}

#[test]
fn hovering_elsewhere_deploys_nothing() {
    let (cx, mut visual, calls) = tooltip_window();
    hover(&mut visual, point(px(800.), px(600.)));
    cx.executor().advance_clock(SHOW_DELAY);
    visual.run_until_parked();
    draw(&mut visual);
    assert!(calls.borrow().is_empty());
}

#[test]
fn the_button_passthrough_deploys_the_tooltip() {
    let (cx, mut visual, calls) = tooltip_window();
    hover(&mut visual, point(px(50.), px(100.)));
    cx.executor().advance_clock(SHOW_DELAY);
    visual.run_until_parked();
    draw(&mut visual);
    assert_eq!(*calls.borrow(), vec!["button"]);
}

/// An anchored tooltip hangs below the hovered parent's bottom edge with the
/// spacing gap: it never covers the parent, wherever the cursor is inside it.
#[test]
fn the_anchored_panel_hangs_below_the_parent_without_overlapping() {
    let (cx, mut visual, _calls) = tooltip_window();
    hover(&mut visual, point(px(50.), px(20.)));
    cx.executor().advance_clock(SHOW_DELAY);
    visual.run_until_parked();
    draw(&mut visual);

    let target = visual
        .debug_bounds("hover-target")
        .expect("target laid out");
    let panel = visual
        .debug_bounds("tooltip-panel")
        .expect("panel rendered");

    let unit = cx.update(|cx| Theme::global(cx).spacing.unit);
    assert!(
        (panel.top() - target.bottom() - unit).abs() <= px(0.5),
        "the panel hangs {gap:?} below the target",
        gap = panel.top() - target.bottom()
    );
    assert!((panel.left() - target.left()).abs() <= px(0.5));
    assert!(
        panel.top() >= target.bottom(),
        "the panel must never overlap the hovered parent"
    );
}

/// A parent pinned to the window's bottom edge leaves no room below: the
/// panel flips above the parent's top edge instead.
#[test]
fn an_anchored_tooltip_flips_above_a_low_parent() {
    let (mut cx, mut visual, window) = low_tooltip_window();

    let window_height = window
        .update(&mut cx, |_, window, _cx| window.viewport_size().height)
        .expect("window alive");
    hover(&mut visual, point(px(50.), window_height - px(20.)));
    cx.executor().advance_clock(SHOW_DELAY);
    visual.run_until_parked();
    draw(&mut visual);

    let target = visual.debug_bounds("low-target").expect("target laid out");
    let panel = visual
        .debug_bounds("tooltip-panel")
        .expect("panel rendered");

    // The flip hangs the panel above the parent's top edge.
    assert!(
        panel.bottom() <= target.top(),
        "the panel must not cover the parent: panel bottom {:?}, parent top {:?}",
        panel.bottom(),
        target.top()
    );
    assert!(
        panel.top() >= px(0.),
        "the flipped panel must stay inside the window"
    );
}