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

use gpui::{
    Context, IntoElement, Modifiers, MouseButton, ParentElement as _, Render, Styled as _,
    TestAppContext, VisualTestContext, Window, WindowHandle, div, point, px,
};
use gpui_native_data::tree::{Tree, TreeItem};
use gpui_native_theme::Theme;

type Changes = Rc<RefCell<Vec<Option<usize>>>>;
type Disclosures = Rc<RefCell<Vec<usize>>>;

struct Harness {
    selected: Option<usize>,
    changes: Changes,
    disclosures: Disclosures,
}

impl Render for Harness {
    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        let changes = self.changes.clone();
        let disclosures = self.disclosures.clone();
        let view = cx.entity();
        let change_view = view.clone();
        div().size_full().child(
            Tree::new("test-tree")
                .selected(self.selected)
                .on_change(move |next, _, cx| {
                    changes.borrow_mut().push(next);
                    change_view.update(cx, |harness, cx| {
                        harness.selected = next;
                        cx.notify();
                    });
                })
                .on_disclosure(move |index, _, cx| {
                    disclosures.borrow_mut().push(index);
                    view.update(cx, |_, cx| cx.notify());
                })
                .items(|_, _| {
                    vec![
                        TreeItem::new("Root")
                            .depth(0)
                            .expandable(true)
                            .expanded(true),
                        TreeItem::new("Child").depth(1),
                        TreeItem::new("Collapsed").depth(0).expandable(true),
                        TreeItem::new("Untouchable").depth(1).disabled(true),
                        TreeItem::new("Last").depth(0),
                    ]
                }),
        )
    }
}

/// Rows paint at the top-left, one per ~34 px band (same rhythm as the
/// list), so clicks at `(50, 16/48/80/112/144)` land on Root / Child /
/// Collapsed / the disabled Untouchable / Last. Each expandable row leads
/// with a 16 px disclosure slot at its indent — a click at `(24, y)` hits
/// row 0's chevron.
fn tree_window() -> (
    TestAppContext,
    VisualTestContext,
    WindowHandle<Harness>,
    Changes,
    Disclosures,
) {
    let mut cx = TestAppContext::single();
    cx.update(Theme::init);
    let changes = Rc::new(RefCell::new(Vec::new()));
    let disclosures = Rc::new(RefCell::new(Vec::new()));
    let harness_changes = changes.clone();
    let harness_disclosures = disclosures.clone();
    let window = cx.add_window(move |_, _| Harness {
        selected: None,
        changes: harness_changes,
        disclosures: harness_disclosures,
    });
    let mut visual = VisualTestContext::from_window(window.into(), &cx);
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });
    (cx, visual, window, changes, disclosures)
}

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

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());
}

#[test]
fn clicking_a_row_selects_it_and_hands_the_tree_the_keyboard() {
    let (_cx, mut visual, _window, changes, disclosures) = tree_window();

    click(&mut visual, point(px(50.), px(16.)));
    assert_eq!(*changes.borrow(), vec![Some(0)]);
    assert!(disclosures.borrow().is_empty());

    // The click focused the tree; arrows move within the visible rows.
    visual.simulate_keystrokes("down");
    draw(&mut visual);
    assert_eq!(*changes.borrow(), vec![Some(0), Some(1)]);
}

#[test]
fn clicking_the_disclosure_toggles_without_selecting() {
    let (_cx, mut visual, _window, changes, disclosures) = tree_window();

    // Row 0's chevron, not its label.
    click(&mut visual, point(px(24.), px(16.)));
    draw(&mut visual);
    assert_eq!(*disclosures.borrow(), vec![0]);
    assert!(
        changes.borrow().is_empty(),
        "a disclosure is not a selection"
    );
}

#[test]
fn arrow_right_expands_and_left_collapses_the_selected_row() {
    let (_cx, mut visual, _window, changes, disclosures) = tree_window();

    click(&mut visual, point(px(50.), px(16.))); // Root: expanded expandable
    visual.simulate_keystrokes("left"); // collapse → reports
    visual.simulate_keystrokes("right"); // still collapsed per the caller → nothing yet
    visual.simulate_keystrokes("down"); // Child: a leaf → arrows are inert
    visual.simulate_keystrokes("right");
    visual.simulate_keystrokes("left");
    draw(&mut visual);
    assert_eq!(*disclosures.borrow(), vec![0]);
    assert_eq!(
        *changes.borrow(),
        vec![Some(0), Some(1)],
        "disclosure keys never change the selection"
    );

    // Select the collapsed expandable row and expand it.
    click(&mut visual, point(px(50.), px(80.)));
    visual.simulate_keystrokes("right");
    draw(&mut visual);
    assert_eq!(*disclosures.borrow(), vec![0, 2]);
}

#[test]
fn keyboard_navigation_skips_disabled_rows_and_never_wraps() {
    let (_cx, mut visual, _window, changes, _disclosures) = tree_window();

    click(&mut visual, point(px(50.), px(16.)));
    visual.simulate_keystrokes("down"); // Two
    visual.simulate_keystrokes("down"); // Collapsed — selectable, not disabled
    visual.simulate_keystrokes("down"); // over the disabled row → Last
    visual.simulate_keystrokes("down"); // last selectable; no wrap
    draw(&mut visual);
    assert_eq!(*changes.borrow(), vec![Some(0), Some(1), Some(2), Some(4)]);

    visual.simulate_keystrokes("home");
    visual.simulate_keystrokes("end");
    visual.simulate_keystrokes("up"); // over the disabled row
    draw(&mut visual);
    assert_eq!(
        *changes.borrow(),
        vec![
            Some(0),
            Some(1),
            Some(2),
            Some(4),
            Some(0),
            Some(4),
            Some(2)
        ]
    );
}

#[test]
fn disclosure_keys_skip_disabled_and_unselected_rows() {
    let (_cx, mut visual, _window, changes, disclosures) = tree_window();

    // Focus through the first row, then park the selection on the leaf.
    click(&mut visual, point(px(50.), px(16.)));
    visual.simulate_keystrokes("down"); // Child (leaf), focused tree
    visual.simulate_keystrokes("left"); // leaf: no disclosure
    visual.simulate_keystrokes("right"); // leaf: no disclosure
    draw(&mut visual);
    assert!(disclosures.borrow().is_empty());
    assert_eq!(*changes.borrow(), vec![Some(0), Some(1)]);
}