use crate::prelude::*;
use std::time::{Duration, Instant};

/// What focusing a text field takes from whichever backend is running --
/// tracked here rather than duplicated per backend, since `Selector` and
/// `Selectable` (below) are the *only* thing that decides which `TextEdit`
/// is the IME's target, and both platforms need the same double-click
/// timing and the same "remember which one" bookkeeping. What differs is
/// what happens *after* the focus record is set: winit tells the
/// compositor an IME area (`focus_gained`, in `default/attr.rs`); on
/// android-view a keyboard has to be asked for explicitly, and only from a
/// JNI call this crate cannot make outside a view callback -- so
/// `focus_gained` there (`android/attr.rs`) just raises a flag the next
/// touch callback consumes. See RUST.md's I2.
pub trait FocusHost {
    /// True on a click close enough in time to the previous one to grow a
    /// selection instead of starting a new one, updating the clock as a
    /// side effect the way a real double-click timer does.
    fn recent_click(&mut self) -> bool;
    fn set_focus(&mut self, id: Option<WeakWidget<TextEdit>>);
    /// Called on every tap that should put the IME on `id`: the tap that
    /// *makes* a `TextEdit` the focus target, and any later tap on one that
    /// already is. `region` is where it was hit (`None` when the widget
    /// could not be located, which happens for one it was just deselected
    /// from). Implementations must be idempotent -- both backends' calls
    /// (`showSoftInput`, `set_ime_cursor_area`) already are, which is what
    /// lets the repeat tap be handled by the same call rather than by a
    /// second "re-show" entry point beside it.
    fn focus_gained(&mut self, region: Option<PixelRegion>);
    /// Whether `id` is the current focus target -- what [`select`] uses to
    /// tell a fresh press (which must wait to see whether it becomes a tap
    /// or a drag before focusing/showing the IME, Iris 2026-09-06: "if I
    /// swipe over the input bar it brings up the keyboard") from a drag
    /// continuing inside a field that was already focused (an ordinary
    /// drag-to-select, unaffected).
    fn is_focused(&self, id: WeakWidget<TextEdit>) -> bool;
}

/// Helper shared by every `FocusHost` impl, so the double-click window is
/// one constant rather than one per backend.
pub fn recent_click(last_click: &mut Instant) -> bool {
    let now = Instant::now();
    let recent = (now - *last_click) < Duration::from_millis(300);
    *last_click = now;
    recent
}

/// `PressStart`/`Pressing`/`PressEnd`, all for the left button -- what
/// [`Selector`]/[`Selectable`] register instead of [`CursorSense::
/// click_or_drag`], so their shared handler (`on_press`, below) sees every
/// frame of a gesture and can tell a completed tap from a drag itself,
/// rather than reacting to `PressStart` alone the way `click_or_drag`'s
/// consumer used to (Iris, 2026-09-06: "if I swipe over the input bar it
/// brings up the keyboard").
/// `CursorSense::Cancel` is in the set for the same reason `DragGesture`
/// registers it: if a scroll area or a list takes the pointer mid-gesture,
/// this field sees no `PressEnd`, and a `press_origin` left set is then
/// compared against the *next* press -- a stray selection, or a keyboard
/// summoned by a tap somewhere else entirely.
fn press_track() -> CursorSenses {
    CursorSense::click()
        | CursorSense::Pressing(CursorButton::Left)
        | CursorSense::unclick()
        | CursorSense::Cancel
}

pub struct Selector;

impl<Rsc: HasEvents, W: Widget + 'static> WidgetAttr<Rsc, W> for Selector
where
    Rsc::State: FocusHost,
{
    type Input = WeakWidget<TextEdit>;

    fn run(rsc: &mut Rsc, container: WeakWidget<W>, id: Self::Input) {
        rsc.register_event(container, press_track(), move |ctx, rsc| {
            let region = ctx.data.render.window_region(&id, &*rsc).unwrap();
            let id_pos = region.top_left;
            let container_pos = ctx
                .data
                .render
                .window_region(&container, &*rsc)
                .unwrap()
                .top_left;
            let pos = ctx.data.pos + container_pos - id_pos;
            let size = region.size();
            on_press(
                rsc,
                ctx.data.render,
                ctx.state,
                id,
                pos,
                size,
                ctx.data.sense,
            );
        });
    }
}

pub struct Selectable;

impl<Rsc: HasEvents> WidgetAttr<Rsc, TextEdit> for Selectable
where
    Rsc::State: FocusHost,
{
    type Input = ();

    fn run(rsc: &mut Rsc, id: WeakWidget<TextEdit>, _: Self::Input) {
        rsc.register_event(id, press_track(), move |ctx, rsc| {
            on_press(
                rsc,
                ctx.data.render,
                ctx.state,
                id,
                ctx.data.pos,
                ctx.data.size,
                ctx.data.sense,
            );
        });
    }
}

/// One press-track frame (`PressStart`, `Pressing` or `PressEnd`) over a
/// selectable field. A field that is *already* focused behaves exactly as
/// `click_or_drag` always did -- every frame updates the selection, which
/// is what lets a finger already inside a focused field drag out a
/// selection. A field that is **not** focused withholds `select`'s
/// focus-granting side effects (and so the platform-specific `focus_gained`
/// that shows the keyboard) until the press resolves as a tap: `PressEnd`
/// with no frame in between having moved past [`DRAG_SLOP`] from where the
/// press began. A drag recognised before release simply cancels the
/// pending tap and does nothing further here -- it is not consumed, so
/// whatever is behind the field (a list to pan) still sees every frame of
/// it, the same as a drag that never touched a selectable field at all.
fn on_press(
    rsc: &mut impl UiRsc,
    render: &UiRenderState,
    state: &mut impl FocusHost,
    id: WeakWidget<TextEdit>,
    pos: Vec2,
    size: Vec2,
    sense: CursorSense,
) {
    if state.is_focused(id) {
        // Already focused, so there is no keyboard to withhold -- but a
        // vertical drag still is not a selection. Android's own `EditText`
        // scrolls its overflowed text on a vertical drag and starts a
        // selection only from a long press; a scroll area wrapping this
        // field (`ScrollController::drag`) is what actually pans, and it needs the
        // first frames of the gesture not to have selected anything behind
        // it before it crosses `DRAG_SLOP` and takes pointer capture.
        // `press_origin` carries the same meaning here as in the unfocused
        // branch below -- "this gesture is still eligible", cleared the
        // moment it becomes a drag -- so there is one flag, not two.
        match sense {
            CursorSense::PressStart(_) => {
                let recent = state.recent_click();
                id.edit(rsc).text.press_origin = Some(pos);
                id.edit(rsc).select(pos, size, false, recent);
            }
            CursorSense::Pressing(_) | CursorSense::PressEnd(_) => {
                let mut ctx = id.edit(rsc);
                let Some(origin) = ctx.text.press_origin else {
                    return;
                };
                let (dx, dy) = (pos.x - origin.x, pos.y - origin.y);
                if dy.abs() > DRAG_SLOP && dy.abs() >= dx.abs() {
                    ctx.text.press_origin = None;
                    return;
                }
                let ended = matches!(sense, CursorSense::PressEnd(_));
                if ended {
                    ctx.text.press_origin = None;
                }
                ctx.select(pos, size, true, false);
                // A tap on a field that is *already* focused asks for the
                // keyboard again (Iris's phone, 2026-09-06: "I can't reopen
                // keyboard by tapping on message box after it already
                // happened once"). Dismissing the IME -- back gesture, or
                // its own hide button -- takes the keyboard away but leaves
                // the field focused, so without this the one branch that
                // requests it (the unfocused one below) never runs again
                // and the field is permanently unable to summon it.
                // Android's own `EditText` does exactly this: every tap on
                // a focused field calls `showSoftInput`, which is a no-op
                // when the keyboard is already up.
                //
                // Gated on the same tap-vs-drag test the unfocused branch
                // uses, not on `PressEnd` alone, so a drag-to-select that
                // happens to finish inside the field does not summon a
                // keyboard the reader was not asking for.
                if ended && dx.abs() <= DRAG_SLOP && dy.abs() <= DRAG_SLOP {
                    state.focus_gained(render.window_region(&id, &*rsc));
                }
            }
            CursorSense::Cancel => id.edit(rsc).text.press_origin = None,
            _ => {}
        }
        return;
    }

    match sense {
        CursorSense::PressStart(_) => {
            id.edit(rsc).text.press_origin = Some(pos);
        }
        CursorSense::Pressing(_) => {
            let ctx = id.edit(rsc);
            if let Some(origin) = ctx.text.press_origin
                && ((pos.x - origin.x).abs() > DRAG_SLOP || (pos.y - origin.y).abs() > DRAG_SLOP)
            {
                // Past the slop before release: this is a drag, not a tap
                // -- give up the pending focus rather than granting it once
                // the finger lifts wherever it happens to be by then.
                ctx.text.press_origin = None;
            }
        }
        // The gesture was taken by somebody else, so it is not a tap and
        // must not grant focus when it ends out of this widget's sight.
        CursorSense::Cancel => id.edit(rsc).text.press_origin = None,
        CursorSense::PressEnd(_) => {
            let was_tap = id.edit(rsc).text.press_origin.take().is_some();
            if was_tap {
                let recent = state.recent_click();
                id.edit(rsc).select(pos, size, false, recent);
                state.set_focus(Some(id));
                state.focus_gained(render.window_region(&id, &*rsc));
            }
        }
        _ => {}
    }
}