use crate::*;
pub use self::Direction::*;
/// A cardinal direction.
#[derive(Copy, Clone, PartialEq)]
pub enum Direction { North, South, East, West, Above, Below }
impl Direction {
    pub fn split_fixed <N: Coordinate> (self, area: impl Area<N>, a: N) -> ([N;4],[N;4]) {
        let [x, y, w, h] = area.xywh();
        match self {
            North => ([x, (y+h).minus(a), w, a], [x, y, w, h.minus(a)]),
            South => ([x, y, w, a], [x, y + a, w, h.minus(a)]),
            East  => ([x, y, a, h], [x + a, y, w.minus(a), h]),
            West  => ([(x+w).minus(a), y, a, h], [x, y, w - a, h]),
            Above | Below => (area.xywh(), area.xywh())
        }
    }
}
pub struct Bsp<E, X, Y>(PhantomData<E>, Direction, X, Y);
impl<E: Output, A: Content<E>, B: Content<E>> Content<E> for Bsp<E, 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.1 {
            Below => { to.place(area_a, a); to.place(area_b, b); },
            _     => { to.place(area_b, b); to.place(area_a, a); }
        }
    }
}
impl<E, A, B> Bsp<E, A, B> {
    pub fn n (a: A, b: B) -> Self { Self(Default::default(), North, a, b) }
    pub fn s (a: A, b: B) -> Self { Self(Default::default(), South, a, b) }
    pub fn e (a: A, b: B) -> Self { Self(Default::default(), East,  a, b) }
    pub fn w (a: A, b: B) -> Self { Self(Default::default(), West,  a, b) }
    pub fn a (a: A, b: B) -> Self { Self(Default::default(), Above, a, b) }
    pub fn b (a: A, b: B) -> Self { Self(Default::default(), 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<E, A, B> {
    fn direction (&self) -> Direction { self.1 }
    fn contents (&self) -> (&A, &B) { (&self.2, &self.3) }
}
impl<'a, E: Output + 'a, T: EdnViewData<'a, E>> TryFromEdn<'a, T> for Bsp<E, RenderBox<'a, E>, RenderBox<'a, E>> {
    fn try_from_edn (s: &'a T, head: &EdnItem, tail: &'a [EdnItem]) -> Option<Self> {
        use EdnItem::*;
        Some(match (head, tail) {
            (Key("bsp/n"), [a, b]) => Self::n(
                s.get_content(a).expect("no a"),
                s.get_content(b).expect("no b")),
            (Key("bsp/s"), [a, b]) => Self::s(
                s.get_content(a).expect("no a"),
                s.get_content(b).expect("no b")),
            (Key("bsp/e"), [a, b]) => Self::e(
                s.get_content(a).expect("no a"),
                s.get_content(b).expect("no b")),
            (Key("bsp/w"), [a, b]) => Self::w(
                s.get_content(a).expect("no a"),
                s.get_content(b).expect("no b")),
            (Key("bsp/a"), [a, b]) => Self::a(
                s.get_content(a).expect("no a"),
                s.get_content(b).expect("no b")),
            (Key("bsp/b"), [a, b]) => Self::b(
                s.get_content(a).expect("no a"),
                s.get_content(b).expect("no b")),
            _ => return None
        })
    }
}

/// 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 }};
}