//! A widget takes only what it answers to: a button over a list takes the
//! click and leaves the scroll. These drive `run_sensors` directly, which
//! needs no GPU and no window.

use iris::prelude::*;
use std::{cell::Cell, rc::Rc};

struct SenseRsc {
    ui: UiData,
    events: EventManager<SenseRsc>,
}

impl UiRsc for SenseRsc {
    fn ui(&self) -> &UiData {
        &self.ui
    }
    fn ui_mut(&mut self) -> &mut UiData {
        &mut self.ui
    }
    fn on_draw(&mut self, active: &ActiveData) {
        self.events.draw(active);
    }
    fn on_undraw(&mut self, active: &ActiveData) {
        self.events.undraw(active);
    }
    fn on_remove(&mut self, id: WidgetId) {
        self.events.remove(id);
    }
}

impl HasState for SenseRsc {
    type State = ();
}

impl HasEvents for SenseRsc {
    fn events(&self) -> &EventManager<Self> {
        &self.events
    }
    fn events_mut(&mut self) -> &mut EventManager<Self> {
        &mut self.events
    }
}

fn cursor_at(pos: Vec2) -> CursorState {
    CursorState {
        pos,
        exists: true,
        buttons: Default::default(),
        scroll_delta: Vec2::ZERO,
    }
}

/// A button covering a list, on the layer above it: the list scrolls, the
/// button clicks, and the returned flags say which fired.
fn button_over_list() -> (UiRenderState, SenseRsc, Rc<Cell<bool>>, Rc<Cell<bool>>) {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };

    // Both cover the whole window: the button "sitting over" the list.
    let list = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let list_weak = list.weak();
    let button = rsc.ui.widgets.add_strong(Rect::new(UiColor::RED));
    let button_weak = button.weak();

    let scrolled = Rc::new(Cell::new(false));
    let clicked = Rc::new(Cell::new(false));
    {
        let scrolled = scrolled.clone();
        rsc.register_event(list_weak, CursorSense::Scroll, move |_ctx, _rsc| {
            scrolled.set(true);
        });
    }
    {
        let clicked = clicked.clone();
        rsc.register_event(button_weak, CursorSense::click(), move |_ctx, _rsc| {
            clicked.set(true);
        });
    }

    // A Stack draws each child on its own layer, in order.
    let root = rsc
        .ui
        .widgets
        .add_strong(Stack {
            children: vec![list.any(), button.any()],
            size: StackSize::default(),
        })
        .any();

    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&root, &mut rsc);

    (render, rsc, scrolled, clicked)
}

#[test]
fn a_button_over_a_list_scrolls_the_list_and_still_clicks() {
    let (render, mut rsc, scrolled, clicked) = button_over_list();
    let mut state = ();

    let mut scroll = cursor_at((50.0, 50.0).into());
    scroll.scroll_delta = (0.0, 10.0).into();
    render.run_sensors(&mut rsc, &mut state, scroll, (100.0, 100.0).into());

    assert!(
        scrolled.get(),
        "a scroll over the button must still reach the list underneath it"
    );
    assert!(
        !clicked.get(),
        "a scroll is not a click; the button must not have fired"
    );

    let mut click = cursor_at((50.0, 50.0).into());
    click.buttons.left = ActivationState::Start;
    render.run_sensors(&mut rsc, &mut state, click, (100.0, 100.0).into());

    assert!(
        clicked.get(),
        "the button on top must still receive an actual click"
    );
}

#[test]
fn a_click_and_a_scroll_in_one_frame_go_to_different_widgets() {
    let (render, mut rsc, scrolled, clicked) = button_over_list();
    let mut state = ();

    let mut both = cursor_at((50.0, 50.0).into());
    both.scroll_delta = (0.0, 10.0).into();
    both.buttons.left = ActivationState::Start;
    render.run_sensors(&mut rsc, &mut state, both, (100.0, 100.0).into());

    assert!(
        clicked.get(),
        "the button takes the click it registered for"
    );
    assert!(
        scrolled.get(),
        "taking the click must not take the scroll with it"
    );
}

#[test]
fn leaving_a_widget_still_ends_its_hover() {
    let mut rsc = SenseRsc {
        ui: UiData::default(),
        events: EventManager::default(),
    };
    let widget = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
    let ended = Rc::new(Cell::new(false));
    {
        let ended = ended.clone();
        rsc.register_event(widget.weak(), CursorSense::HoverEnd, move |_ctx, _rsc| {
            ended.set(true);
        });
    }

    let root = widget.any();
    let mut render = UiRenderState::new();
    render.resize((100.0, 100.0));
    render.update(&root, &mut rsc);

    let mut state = ();
    render.run_sensors(
        &mut rsc,
        &mut state,
        cursor_at((50.0, 50.0).into()),
        (100.0, 100.0).into(),
    );
    assert!(!ended.get(), "the cursor is still on it");

    let mut gone = cursor_at((50.0, 50.0).into());
    gone.exists = false;
    render.run_sensors(&mut rsc, &mut state, gone, (100.0, 100.0).into());
    assert!(ended.get(), "leaving a widget ends its hover");
}