//! Input across layers: what a widget takes, what passes through it, and
//! where hovering stops. These drive `run_sensors` directly, which needs no
//! GPU and no window.

use iris::prelude::*;
use std::{cell::RefCell, 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
    }
}

const WINDOW: f32 = 100.0;

/// Every sense that has fired on one widget since it was last read.
#[derive(Default, Clone)]
struct Fired(Rc<RefCell<Vec<CursorSense>>>);

impl Fired {
    fn take(&self) -> Vec<CursorSense> {
        std::mem::take(&mut self.0.borrow_mut())
    }
}

struct Ui {
    rsc: SenseRsc,
    render: UiRenderState,
    state: (),
}

impl Ui {
    fn new() -> Self {
        Self {
            rsc: SenseRsc {
                ui: UiData::default(),
                events: EventManager::default(),
            },
            render: UiRenderState::new(),
            state: (),
        }
    }

    fn listen<W: Widget + ?core::marker::Sized + 'static>(
        &mut self,
        widget: &StrongWidget<W>,
        senses: impl Into<CursorSenses>,
    ) -> Fired {
        let fired = Fired::default();
        let sink = fired.clone();
        self.rsc
            .register_event(widget.weak(), senses.into(), move |ctx, _rsc| {
                sink.0.borrow_mut().push(ctx.data.sense)
            });
        fired
    }

    /// Stacks the widgets bottom first, each on its own layer, and lays them
    /// out in a square window.
    fn stack(&mut self, children: Vec<StrongWidget>) {
        let root = self
            .rsc
            .ui
            .widgets
            .add_strong(Stack {
                children,
                size: StackSize::default(),
            })
            .any();
        self.render.resize((WINDOW, WINDOW));
        self.render.update(&root, &mut self.rsc);
    }

    fn cursor(&mut self, at: (f32, f32)) -> CursorState {
        CursorState {
            pos: at.into(),
            exists: true,
            buttons: Default::default(),
            scroll_delta: Vec2::ZERO,
        }
    }

    fn run(&mut self, cursor: CursorState) {
        self.render.run_sensors(
            &mut self.rsc,
            &mut self.state,
            cursor,
            (WINDOW, WINDOW).into(),
        );
    }
}

fn full(ui: &mut Ui) -> StrongWidget<Rect> {
    rect(UiColor::WHITE).add_strong(&mut ui.rsc)
}

#[test]
fn hover_stops_at_the_topmost_widget() {
    let mut ui = Ui::new();
    let (bottom, middle, top) = (full(&mut ui), full(&mut ui), full(&mut ui));
    let bottom_hover = ui.listen(&bottom, CursorSense::HoverStart);
    let middle_hover = ui.listen(&middle, CursorSense::HoverStart);
    let top_hover = ui.listen(&top, CursorSense::HoverStart);
    ui.stack(vec![bottom.any(), middle.any(), top.any()]);

    let cursor = ui.cursor((50.0, 50.0));
    ui.run(cursor);

    assert_eq!(top_hover.take(), [CursorSense::HoverStart]);
    assert_eq!(
        middle_hover.take(),
        [],
        "hover is not shared with a layer below"
    );
    assert_eq!(bottom_hover.take(), []);
}

#[test]
fn a_scroll_passes_through_every_widget_that_does_not_want_it() {
    let mut ui = Ui::new();
    let (list, button, overlay) = (full(&mut ui), full(&mut ui), full(&mut ui));
    let scrolled = ui.listen(&list, CursorSense::Scroll);
    let clicked = ui.listen(&button, CursorSense::click());
    let overlay_clicked = ui.listen(&overlay, CursorSense::click());
    ui.stack(vec![list.any(), button.any(), overlay.any()]);

    let mut cursor = ui.cursor((50.0, 50.0));
    cursor.scroll_delta = (0.0, 10.0).into();
    ui.run(cursor);

    assert_eq!(
        scrolled.take(),
        [CursorSense::Scroll],
        "two layers of click-only widgets do not stop a scroll"
    );
    assert_eq!(clicked.take(), []);
    assert_eq!(overlay_clicked.take(), []);
}

#[test]
fn a_click_and_a_scroll_in_one_frame_go_to_different_widgets() {
    let mut ui = Ui::new();
    let (list, button) = (full(&mut ui), full(&mut ui));
    let scrolled = ui.listen(&list, CursorSense::Scroll);
    let clicked = ui.listen(&button, CursorSense::click());
    ui.stack(vec![list.any(), button.any()]);

    let mut cursor = ui.cursor((50.0, 50.0));
    cursor.scroll_delta = (0.0, 10.0).into();
    cursor.buttons.left = ActivationState::Start;
    ui.run(cursor);

    assert_eq!(clicked.take(), [CursorSense::click()]);
    assert_eq!(
        scrolled.take(),
        [CursorSense::Scroll],
        "taking the click must not take the scroll with it"
    );
}

#[test]
fn only_the_topmost_listener_takes_a_press() {
    let mut ui = Ui::new();
    let (below, above) = (full(&mut ui), full(&mut ui));
    let below_clicked = ui.listen(&below, CursorSense::click());
    let above_clicked = ui.listen(&above, CursorSense::click());
    ui.stack(vec![below.any(), above.any()]);

    let mut cursor = ui.cursor((50.0, 50.0));
    cursor.buttons.left = ActivationState::Start;
    ui.run(cursor);

    assert_eq!(above_clicked.take(), [CursorSense::click()]);
    assert_eq!(below_clicked.take(), [], "one press goes to one widget");
}

#[test]
fn a_press_beside_the_button_reaches_the_layer_below() {
    let mut ui = Ui::new();
    let list = full(&mut ui);
    // The row above the list covers it, but only its left half is the button.
    let button = full(&mut ui);
    let gap = full(&mut ui);
    let list_clicked = ui.listen(&list, CursorSense::click());
    let button_clicked = ui.listen(&button, CursorSense::click());
    let row = ui.rsc.ui.widgets.add_strong(Span {
        children: vec![button.any(), gap.any()],
        dir: Dir::RIGHT,
        gap: 0.0,
    });
    ui.stack(vec![list.any(), row.any()]);

    let mut on_button = ui.cursor((20.0, 50.0));
    on_button.buttons.left = ActivationState::Start;
    ui.run(on_button);
    assert_eq!(button_clicked.take(), [CursorSense::click()]);
    assert_eq!(list_clicked.take(), []);

    let mut beside_it = ui.cursor((80.0, 50.0));
    beside_it.buttons.left = ActivationState::Start;
    ui.run(beside_it);
    assert_eq!(button_clicked.take(), [], "the cursor is not on the button");
    assert_eq!(
        list_clicked.take(),
        [CursorSense::click()],
        "a press beside the button belongs to what is under it"
    );
}

#[test]
fn leaving_a_widget_still_ends_its_hover() {
    let mut ui = Ui::new();
    let widget = full(&mut ui);
    let hover = ui.listen(&widget, CursorSense::HoverStart | CursorSense::HoverEnd);
    ui.stack(vec![widget.any()]);

    let cursor = ui.cursor((50.0, 50.0));
    ui.run(cursor);
    assert_eq!(hover.take(), [CursorSense::HoverStart]);

    let mut gone = ui.cursor((50.0, 50.0));
    gone.exists = false;
    ui.run(gone);
    assert_eq!(hover.take(), [CursorSense::HoverEnd]);
}