use crate::*;

/// Defines an enum that parametrically transforms its content
/// along either the X axis, the Y axis, or both.
macro_rules! transform_xy_unit {
    (|$self:ident : $Enum:ident, $to:ident|$layout:expr) => {
        pub enum $Enum<E: Engine, T: Content<E>> {
            X(E::Unit, T), Y(E::Unit, T), XY(E::Unit, E::Unit, T),
        }
        impl<E: Engine, T: Content<E>> $Enum<E, T> {
            pub fn x (x: E::Unit, item: T) -> Self { Self::X(x, item) }
            pub fn y (y: E::Unit, item: T) -> Self { Self::Y(y, item) }
            pub fn xy (x: E::Unit, y: E::Unit, item: T) -> Self { Self::XY(x, y, item) }
            pub fn dx (&self) -> E::Unit {
                match self {
                    Self::X(x, _)     => *x,
                    Self::Y(_, _)     => E::Unit::zero(),
                    Self::XY(x, _, _) => *x,
                }
            }
            pub fn dy (&self) -> E::Unit {
                match self {
                    Self::X(_, _)     => E::Unit::zero(),
                    Self::Y(y, _)     => *y,
                    Self::XY(_, y, _) => *y,
                }
            }
        }
        impl<E: Engine, T: Content<E>> Content<E> for $Enum<E, T> {
            fn content (&self) -> impl Content<E> {
                Some(match self {
                    Self::X(_, content)     => content,
                    Self::Y(_, content)     => content,
                    Self::XY(_, _, content) => content,
                })
            }
            fn layout (&$self, $to: E::Area) -> E::Area {
                $layout.into()
            }
        }
    }
}

transform_xy_unit!(|self: Fixed, area|{
    let area = self.content().layout(area);
    match self {
        Self::X(fw, _) => [area.x(), area.y(), *fw, area.h()],
        Self::Y(fh, _) => [area.x(), area.y(), area.w(), *fh],
        Self::XY(fw, fh, _) => [area.x(), area.y(), *fw, *fh], // tagn
    }
});

transform_xy_unit!(|self: Shrink, area|{
    let area = self.content().layout(area);
    [area.x(), area.y(), area.w().minus(self.dx()), area.h().minus(self.dy())]
});

transform_xy_unit!(|self: Expand, area|{
    let area = self.content().layout(area);
    [area.x(), area.y(), area.w() + self.dx(), area.h() + self.dy()]
});

transform_xy_unit!(|self: Min, area|{
    let area = self.content().layout(area);
    match self {
        Self::X(mw, _)      => [area.x(), area.y(), area.w().max(*mw), area.h()],
        Self::Y(mh, _)      => [area.x(), area.y(), area.w(),          area.h().max(*mh)],
        Self::XY(mw, mh, _) => [area.x(), area.y(), area.w().max(*mw), area.h().max(*mh)]
    }});

transform_xy_unit!(|self: Max, area|{
    let area = self.content().layout(area);
    match self {
        Self::X(mw, _)      => [area.x(), area.y(), area.w().min(*mw), area.h()],
        Self::Y(mh, _)      => [area.x(), area.y(), area.w(),          area.h().min(*mh)],
        Self::XY(mw, mh, _) => [area.x(), area.y(), area.w().min(*mw), area.h().min(*mh)],
    }});

transform_xy_unit!(|self: Push, area|{
    let area = self.content().layout(area);
    [area.x() + self.dx(), area.y() + self.dy(), area.w(), area.h()]
});

transform_xy_unit!(|self: Pull, area|{
    let area = self.content().layout(area);
    [area.x().minus(self.dx()), area.y().minus(self.dy()), area.w(), area.h()]
});

transform_xy_unit!(|self: Margin, area|{
    let area = self.content().layout(area);
    let dx = self.dx();
    let dy = self.dy();
    [area.x().minus(dx), area.y().minus(dy), area.w() + dy + dy, area.h() + dy + dy]
});

transform_xy_unit!(|self: Padding, area|{
    let area = self.content().layout(area);
    let dx = self.dx();
    let dy = self.dy();
    [area.x() + dx, area.y() + dy, area.w().minus(dy + dy), area.h().minus(dy + dy), ]
});