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

use gpui::{
    AnyWindowHandle, AppContext as _, Context, IntoElement, KeyDownEvent, KeyUpEvent, Keystroke,
    Modifiers, MouseButton, ParentElement as _, Render, Styled as _, TestAppContext,
    VisualTestContext, Window, div, point, px,
};
use gpui_native_core::button::ButtonVariant;
use gpui_native_core::dropdown_menu::DropdownMenu;
use gpui_native_core::menu::MenuItem;
use gpui_native_theme::Theme;

struct Harness {
    open: bool,
    split: bool,
    disabled: bool,
    changes: Rc<RefCell<Vec<bool>>>,
    clicks: Rc<RefCell<usize>>,
    activated: Rc<RefCell<Vec<&'static str>>>,
}

impl Render for Harness {
    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        let view = cx.entity();
        let changes = self.changes.clone();
        let clicks = self.clicks.clone();
        let activated = self.activated.clone();
        let mut trigger = DropdownMenu::new("test-dd")
            .label("Save")
            .variant(ButtonVariant::Secondary)
            .open(self.open)
            .on_open_change(move |next, _, cx| {
                changes.borrow_mut().push(next);
                view.update(cx, |harness, cx| {
                    harness.open = next;
                    cx.notify();
                });
            })
            .items(move |_, _| {
                vec![
                    export_item(activated.clone(), "png"),
                    export_item(activated.clone(), "pdf"),
                ]
            });

        if self.disabled {
            trigger = trigger.disabled(true);
        }
        if self.split {
            trigger = trigger.on_click(move |_, _, _| *clicks.borrow_mut() += 1);
        }

        div().size_full().child(trigger)
    }
}

fn export_item(activated: Rc<RefCell<Vec<&'static str>>>, format: &'static str) -> MenuItem {
    MenuItem::new(format).handler(move |_, _| activated.borrow_mut().push(format))
}

type Changes = Rc<RefCell<Vec<bool>>>;
type Clicks = Rc<RefCell<usize>>;
type Activated = Rc<RefCell<Vec<&'static str>>>;

/// A maximized window whose trigger starts in the top-left corner, so the
/// main zone is under the cursor at the button's usual tap position and the
/// chevron zone is found through its debug bounds.
fn dropdown_window(
    split: bool,
    disabled: bool,
) -> (
    TestAppContext,
    VisualTestContext,
    AnyWindowHandle,
    Changes,
    Clicks,
    Activated,
) {
    let mut cx = TestAppContext::single();
    cx.update(Theme::init);
    let changes = Rc::new(RefCell::new(Vec::new()));
    let clicks = Rc::new(RefCell::new(0));
    let activated = Rc::new(RefCell::new(Vec::new()));
    let harness_changes = changes.clone();
    let harness_clicks = clicks.clone();
    let harness_activated = activated.clone();
    let window = cx.add_window(move |_, _| Harness {
        open: false,
        split,
        disabled,
        changes: harness_changes,
        clicks: harness_clicks,
        activated: harness_activated,
    });
    let window = window.into();
    cx.update_window(window, |_, window, cx| {
        window.draw(cx).clear(cx);
    })
    .unwrap();
    let visual = VisualTestContext::from_window(window, &cx);
    (cx, visual, window, changes, clicks, activated)
}

fn draw(visual: &mut VisualTestContext, window: AnyWindowHandle) {
    visual
        .update_window(window, |_, window, cx| {
            window.draw(cx).clear(cx);
        })
        .unwrap();
}

fn click(visual: &mut VisualTestContext, position: gpui::Point<gpui::Pixels>) {
    visual.simulate_mouse_down(position, MouseButton::Left, Modifiers::default());
    visual.simulate_mouse_up(position, MouseButton::Left, Modifiers::default());
}

/// The painted center of an element found through its debug selector.
fn center(visual: &mut VisualTestContext, selector: &'static str) -> gpui::Point<gpui::Pixels> {
    let bounds = visual
        .debug_bounds(selector)
        .unwrap_or_else(|| panic!("{selector} should have been laid out"));
    point(
        bounds.origin.x + bounds.size.width / 2.,
        bounds.origin.y + bounds.size.height / 2.,
    )
}

/// Split form: clicking the main zone fires the action and the menu stays
/// closed — the button keeps its normal behavior under a child menu.
#[test]
fn action_button_fires_and_does_not_open() {
    let (_cx, mut visual, window, changes, clicks, _activated) = dropdown_window(true, false);

    click(&mut visual, point(px(30.), px(14.)));
    assert_eq!(*clicks.borrow(), 1, "the main zone fires on_click");
    assert!(
        changes.borrow().is_empty(),
        "the menu must stay closed: {:?}",
        changes.borrow()
    );

    draw(&mut visual, window);
    assert!(visual.debug_bounds("menu-panel").is_none());
}

/// Split form: only the chevron zone opens the menu, and an activated row
/// closes it.
#[test]
fn chevron_opens_and_row_activation_closes() {
    let (_cx, mut visual, window, changes, clicks, activated) = dropdown_window(true, false);

    let chevron = center(&mut visual, "test-dd-chevron");
    click(&mut visual, chevron);
    assert_eq!(*changes.borrow(), vec![true]);

    draw(&mut visual, window);
    let row = center(&mut visual, "menu-item-0");
    click(&mut visual, row);
    assert_eq!(*activated.borrow(), vec!["png"]);
    assert_eq!(*changes.borrow(), vec![true, false]);
    assert_eq!(*clicks.borrow(), 0, "row activation never fires on_click");
}

/// Menu-only form: the whole button opens the menu on click, like a menu
/// button.
#[test]
fn plain_button_activates_the_menu() {
    let (_cx, mut visual, _window, changes, clicks, _activated) = dropdown_window(false, false);

    click(&mut visual, point(px(30.), px(14.)));
    assert_eq!(*changes.borrow(), vec![true]);
    assert_eq!(*clicks.borrow(), 0);
}

/// Keyboard focus returns to the trigger when the menu closes, so the down
/// arrow opens it again.
#[test]
fn escape_returns_focus_to_the_trigger() {
    let (_cx, mut visual, window, changes, _clicks, _activated) = dropdown_window(true, false);

    let chevron = center(&mut visual, "test-dd-chevron");
    click(&mut visual, chevron);
    draw(&mut visual, window);
    visual.simulate_keystrokes("escape");
    assert_eq!(*changes.borrow(), vec![true, false]);

    draw(&mut visual, window);
    visual.simulate_keystrokes("down");
    assert_eq!(
        *changes.borrow(),
        vec![true, false, true],
        "the focused trigger reopened the menu"
    );
}

/// Enter and Space fire the split button's action while it is focused, like
/// any push button.
#[test]
fn enter_and_space_fire_the_action_while_focused() {
    let (_cx, mut visual, window, changes, clicks, _activated) = dropdown_window(true, false);

    click(&mut visual, point(px(30.), px(14.)));
    draw(&mut visual, window);

    for key in ["enter", "space"] {
        visual.simulate_event(KeyDownEvent {
            keystroke: Keystroke::parse(key).unwrap(),
            is_held: false,
            prefer_character_input: false,
        });
        visual.simulate_event(KeyUpEvent {
            keystroke: Keystroke::parse(key).unwrap(),
        });
    }

    assert_eq!(*clicks.borrow(), 3, "the pointer click, Enter, and Space");
    assert!(changes.borrow().is_empty());
}

/// Enter opens the menu while a menu-only trigger is focused.
#[test]
fn enter_opens_the_menu_only_trigger() {
    let (_cx, mut visual, window, changes, _clicks, _activated) = dropdown_window(false, false);

    // Opening hands focus to the panel; dismissing hands it back to the
    // trigger, whose Enter then reopens the menu.
    click(&mut visual, point(px(30.), px(14.)));
    draw(&mut visual, window);
    visual.simulate_keystrokes("escape");
    draw(&mut visual, window);

    {
        let key = "enter";
        visual.simulate_event(KeyDownEvent {
            keystroke: Keystroke::parse(key).unwrap(),
            is_held: false,
            prefer_character_input: false,
        });
        visual.simulate_event(KeyUpEvent {
            keystroke: Keystroke::parse(key).unwrap(),
        });
    }

    assert_eq!(*changes.borrow(), vec![true, false, true]);
}

/// Action rows sit a half-step apart so the rounded selection highlight
/// reads as its own chip instead of a continuous block.
#[test]
fn action_rows_sit_a_half_step_apart() {
    let (_cx, mut visual, window, _changes, _clicks, _activated) = dropdown_window(true, false);

    let chevron = center(&mut visual, "test-dd-chevron");
    click(&mut visual, chevron);
    draw(&mut visual, window);

    let first = visual
        .debug_bounds("menu-item-0")
        .expect("first row should have been laid out");
    let second = visual
        .debug_bounds("menu-item-1")
        .expect("second row should have been laid out");
    let gap = second.origin.y - (first.origin.y + first.size.height);
    // Painted bounds are snapped to device pixels; allow half a pixel.
    assert!(
        (gap - px(2.)).abs() <= px(0.5),
        "rows should sit 2px apart, got {gap:?}"
    );
}

/// A pointer-opened menu arms no row, so enter cannot fire one; the first
/// down arms a row and enter fires it.
#[test]
fn pointer_opens_arm_nothing() {
    let (_cx, mut visual, window, changes, _clicks, activated) = dropdown_window(true, false);

    let chevron = center(&mut visual, "test-dd-chevron");
    click(&mut visual, chevron);
    draw(&mut visual, window);

    visual.simulate_keystrokes("enter");
    assert!(
        activated.borrow().is_empty(),
        "no row is armed on pointer open"
    );
    assert_eq!(*changes.borrow(), vec![true], "the menu stays open");

    visual.simulate_keystrokes("down enter");
    assert_eq!(*activated.borrow(), vec!["png"]);
    assert_eq!(*changes.borrow(), vec![true, false]);
}

/// A keyboard-opened menu (down arrow from the focused trigger) arms the
/// first selectable row, so enter fires it right away.
#[test]
fn keyboard_opens_arm_the_first_row() {
    let (_cx, mut visual, window, changes, _clicks, activated) = dropdown_window(false, false);

    click(&mut visual, point(px(30.), px(14.)));
    draw(&mut visual, window);
    visual.simulate_keystrokes("escape");
    draw(&mut visual, window);

    visual.simulate_keystrokes("down");
    draw(&mut visual, window);
    visual.simulate_keystrokes("enter");
    assert_eq!(*activated.borrow(), vec!["png"]);
    assert_eq!(*changes.borrow(), vec![true, false, true, false]);
}

/// A disabled trigger ignores both zones.
#[test]
fn disabled_trigger_ignores_clicks() {
    let (_cx, mut visual, window, changes, clicks, _activated) = dropdown_window(true, true);

    click(&mut visual, point(px(30.), px(14.)));
    let chevron = center(&mut visual, "test-dd-chevron");
    click(&mut visual, chevron);
    draw(&mut visual, window);

    assert_eq!(*clicks.borrow(), 0);
    assert!(changes.borrow().is_empty());
    assert!(visual.debug_bounds("menu-panel").is_none());
}