use crate::*;
pub use Direction::*;
/// A split or layer.
pub struct Bsp<X, Y>(Direction, X, Y);
impl<E: Output, A: Content<E>, B: Content<E>> Content<E> for Bsp<A, B> {
    fn layout (&self, outer: E::Area) -> E::Area {
        let [_, _, c] = self.areas(outer);
        c
    }
    fn render (&self, to: &mut E) {
        let [area_a, area_b, _] = self.areas(to.area());
        let (a, b) = self.contents();
        match self.0 {
            Below => { to.place(area_a, a); to.place(area_b, b); },
            _     => { to.place(area_b, b); to.place(area_a, a); }
        }
    }
}
#[cfg(feature = "dsl")]
try_from_expr!(<'a, E>: Bsp<RenderBox<'a, E>, RenderBox<'a, E>>: |state, iter| {
    if let Some(Token { value: Value::Key(key), .. }) = iter.peek() {
        match key {
            "bsp/n"|"bsp/s"|"bsp/e"|"bsp/w"|"bsp/a"|"bsp/b" => {
                let _ = iter.next().unwrap();
                let c1 = iter.next().expect("no content1 specified");
                let c2 = iter.next().expect("no content2 specified");
                let c1 = state.get_content(&c1.value).expect("no content1 provided");
                let c2 = state.get_content(&c2.value).expect("no content2 provided");
                return Some(match key {
                    "bsp/n" => Self::n(c1, c2),
                    "bsp/s" => Self::s(c1, c2),
                    "bsp/e" => Self::e(c1, c2),
                    "bsp/w" => Self::w(c1, c2),
                    "bsp/a" => Self::a(c1, c2),
                    "bsp/b" => Self::b(c1, c2),
                    _ => unreachable!(),
                })
            },
            _ => return None
        }
    }
});
impl<A, B> Bsp<A, B> {
    #[inline] pub fn n (a: A, b: B) -> Self { Self(North, a, b) }
    #[inline] pub fn s (a: A, b: B) -> Self { Self(South, a, b) }
    #[inline] pub fn e (a: A, b: B) -> Self { Self(East,  a, b) }
    #[inline] pub fn w (a: A, b: B) -> Self { Self(West,  a, b) }
    #[inline] pub fn a (a: A, b: B) -> Self { Self(Above, a, b) }
    #[inline] pub fn b (a: A, b: B) -> Self { Self(Below, a, b) }
}
pub trait BspAreas<E: Output, A: Content<E>, B: Content<E>> {
    fn direction (&self) -> Direction;
    fn contents (&self) -> (&A, &B);
    fn areas (&self, outer: E::Area) -> [E::Area;3] {
        let direction = self.direction();
        let [x, y, w, h] = outer.xywh();
        let (a, b) = self.contents();
        let [aw, ah] = a.layout(outer).wh();
        let [bw, bh] = b.layout(match direction {
            Above | Below => outer,
            South => [x, y + ah, w, h.minus(ah)].into(),
            North => [x, y, w, h.minus(ah)].into(),
            East  => [x + aw, y, w.minus(aw), h].into(),
            West  => [x, y, w.minus(aw), h].into(),
        }).wh();
        match direction {
            Above | Below => {
                let [x, y, w, h] = outer.center_xy([aw.max(bw), ah.max(bh)]);
                let a = [(x + w/2.into()).minus(aw/2.into()), (y + h/2.into()).minus(ah/2.into()), aw, ah];
                let b = [(x + w/2.into()).minus(bw/2.into()), (y + h/2.into()).minus(bh/2.into()), bw, bh];
                [a.into(), b.into(), [x, y, w, h].into()]
            },
            South => {
                let [x, y, w, h] = outer.center_xy([aw.max(bw), ah + bh]);
                let a = [(x + w/2.into()).minus(aw/2.into()), y, aw, ah];
                let b = [(x + w/2.into()).minus(bw/2.into()), y + ah, bw, bh];
                [a.into(), b.into(), [x, y, w, h].into()]
            },
            North => {
                let [x, y, w, h] = outer.center_xy([aw.max(bw), ah + bh]);
                let a = [(x + (w/2.into())).minus(aw/2.into()), y + bh, aw, ah];
                let b = [(x + (w/2.into())).minus(bw/2.into()), y, bw, bh];
                [a.into(), b.into(), [x, y, w, h].into()]
            },
            East => {
                let [x, y, w, h] = outer.center_xy([aw + bw, ah.max(bh)]);
                let a = [x,      (y + h/2.into()).minus(ah/2.into()), aw, ah];
                let b = [x + aw, (y + h/2.into()).minus(bh/2.into()), bw, bh];
                [a.into(), b.into(), [x, y, w, h].into()]
            },
            West => {
                let [x, y, w, h] = outer.center_xy([aw + bw, ah.max(bh)]);
                let a = [x + bw, (y + h/2.into()).minus(ah/2.into()), aw, ah];
                let b = [x,      (y + h/2.into()).minus(bh/2.into()), bw, bh];
                [a.into(), b.into(), [x, y, w, h].into()]
            },
        }
    }
}
impl<E: Output, A: Content<E>, B: Content<E>> BspAreas<E, A, B> for Bsp<A, B> {
    fn direction (&self) -> Direction { self.0 }
    fn contents (&self) -> (&A, &B) { (&self.1, &self.2) }
}
/// Renders multiple things on top of each other,
#[macro_export] macro_rules! lay {
    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::b(bsp, $expr);)*; bsp }}
}
/// Stack southward.
#[macro_export] macro_rules! col {
    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::s(bsp, $expr);)*; bsp }};
}
/// Stack northward.
#[macro_export] macro_rules! col_up {
    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::n(bsp, $expr);)*; bsp }}
}
/// Stack eastward.
#[macro_export] macro_rules! row {
    ($($expr:expr),* $(,)?) => {{ let bsp = (); $(let bsp = Bsp::e(bsp, $expr);)*; bsp }};
}
#[cfg(test)] mod test {
    use super::*;
    use proptest::prelude::*;
    proptest! {
        #[test] fn proptest_op_bsp (
            d in prop_oneof![
                Just(North), Just(South),
                Just(East),  Just(West),
                Just(Above), Just(Below)
            ],
            a in "\\PC*",
            b in "\\PC*",
            x in u16::MIN..u16::MAX,
            y in u16::MIN..u16::MAX,
            w in u16::MIN..u16::MAX,
            h in u16::MIN..u16::MAX,
        ) {
            let bsp = Bsp(d, a, b);
            assert_eq!(
                Content::layout(&bsp, [x, y, w, h]),
                Render::layout(&bsp, [x, y, w, h]),
            );
        }
    }
}