//! [Content] items that modify the inherent
//! dimensions of their inner [Render]ables.
//!
//! Transform may also react to the [Area] provided.
//! ```
//! use ::tengri::{output::*, tui::*};
//! let area: [u16;4] = [10, 10, 20, 20];
//! fn test (area: [u16;4], item: &impl Content<TuiOut>, expected: [u16;4]) {
//!     assert_eq!(Content::layout(item, area), expected);
//!     assert_eq!(Render::layout(item, area),  expected);
//! };
//! test(area, &(), [20, 20, 0, 0]);
//!
//! test(area, &Fill::xy(()), area);
//! test(area, &Fill::x(()),  [10, 20, 20, 0]);
//! test(area, &Fill::y(()),  [20, 10, 0, 20]);
//!
//! //FIXME:test(area, &Fixed::x(4, ()),     [18, 20, 4, 0]);
//! //FIXME:test(area, &Fixed::y(4, ()),     [20, 18, 0, 4]);
//! //FIXME:test(area, &Fixed::xy(4, 4, unit), [18, 18, 4, 4]);
//! ```

use crate::*;

/// Defines an enum that transforms its content
/// along either the X axis, the Y axis, or both.
macro_rules! transform_xy {
    ($x:literal $y:literal $xy:literal |$self:ident : $Enum:ident, $to:ident|$area:expr) => {
        pub enum $Enum<T> { X(T), Y(T), XY(T) }
        impl<T> $Enum<T> {
            #[inline] pub const fn x (item: T) -> Self { Self::X(item) }
            #[inline] pub const fn y (item: T) -> Self { Self::Y(item) }
            #[inline] pub const fn xy (item: T) -> Self { Self::XY(item) }
        }
        #[cfg(feature = "dsl")]
        impl<'a, E: Output + 'a, T: ViewContext<'a, E>> TryFromDsl<'a, T>
        for $Enum<RenderBox<'a, E>> {
            fn try_from_expr (state: &'a T, iter: TokenIter<'a>) -> Option<Self> {
                let mut iter = iter.clone();
                if let Some(Token { value: Value::Key(k), .. }) = iter.peek() {
                    if k == $x || k == $y || k == $xy {
                        let _ = iter.next().unwrap();
                        let token = iter.next().expect("no content specified");
                        let content = get_content!(state => token);
                        return Some(match k {
                            $x => Self::x(content),
                            $y => Self::y(content),
                            $xy => Self::xy(content),
                            _ => unreachable!()
                        })
                    }
                }
                None
            }
        }
        impl<E: Output, T: Content<E>> Content<E> for $Enum<T> {
            fn content (&self) -> impl Render<E> {
                match self {
                    Self::X(item)  => item,
                    Self::Y(item)  => item,
                    Self::XY(item) => item,
                }
            }
            fn layout (&$self, $to: <E as Output>::Area) -> <E as Output>::Area {
                use $Enum::*;
                $area
            }
        }
    }
}

/// Defines an enum that parametrically transforms its content
/// along either the X axis, the Y axis, or both.
macro_rules! transform_xy_unit {
    ($x:literal $y:literal $xy:literal |$self:ident : $Enum:ident, $to:ident|$layout:expr) => {
        pub enum $Enum<U, T> { X(U, T), Y(U, T), XY(U, U, T), }
        impl<U, T> $Enum<U, T> {
            #[inline] pub const fn x (x: U, item: T) -> Self { Self::X(x, item) }
            #[inline] pub const fn y (y: U, item: T) -> Self { Self::Y(y, item) }
            #[inline] pub const fn xy (x: U, y: U, item: T) -> Self { Self::XY(x, y, item) }
        }
        #[cfg(feature = "dsl")]
        impl<'a, E: Output + 'a, T: ViewContext<'a, E>> TryFromDsl<'a, T>
        for $Enum<E::Unit, RenderBox<'a, E>> {
            fn try_from_expr (state: &'a T, iter: TokenIter<'a>) -> Option<Self> {
                let mut iter = iter.clone();
                if let Some(Token { value: Value::Key(k), .. }) = iter.peek() {
                    if k == $x || k == $y {
                        let _ = iter.next().unwrap();
                        let u = iter.next().expect("no unit specified");
                        let u = get_value!(state => u);
                        let c = iter.next().expect("no content specified");
                        let c = get_content!(state => c);
                        return Some(match k {
                            $x => Self::x(u, c),
                            $y => Self::y(u, c),
                            _ => unreachable!(),
                        })
                    } else if k == $xy {
                        let _ = iter.next().unwrap();
                        let u = get_value!(state => iter.next().expect("no unit specified"));
                        let v = get_value!(state => iter.next().expect("no unit specified"));
                        let c = get_content!(state => iter.next().expect("no content specified"));
                        return Some(Self::xy(u, v, c))
                    }
                }
                None
            }
        }
        impl<E: Output, T: Content<E>> Content<E> for $Enum<E::Unit, T> {
            fn content (&self) -> impl Render<E> {
                Some(match self {
                    Self::X(_, content) => content,
                    Self::Y(_, content) => content,
                    Self::XY(_, _, content) => content,
                })
            }
            fn layout (&$self, $to: E::Area) -> E::Area {
                $layout.into()
            }
        }
        impl<U: Copy + Coordinate, T> $Enum<U, T> {
            #[inline] pub fn dx (&self) -> U {
                match self {
                    Self::X(x, _) => *x, Self::Y(_, _) => 0.into(), Self::XY(x, _, _) => *x,
                }
            }
            #[inline] pub fn dy (&self) -> U {
                match self {
                    Self::X(_, _) => 0.into(), Self::Y(y, _) => *y, Self::XY(_, y, _) => *y,
                }
            }
        }
    }
}

transform_xy!("fill/x" "fill/y" "fill/xy" |self: Fill, to|{
    let [x0, y0, wmax, hmax] = to.xywh();
    let [x, y, w, h] = self.content().layout(to).xywh();
    match self {
        X(_)  => [x0, y, wmax, h],
        Y(_)  => [x, y0, w, hmax],
        XY(_) => [x0, y0, wmax, hmax],
    }.into()
});

transform_xy_unit!("fixed/x" "fixed/y" "fixed/xy"|self: Fixed, area|{
    let [x, y, w, h] = area.xywh();
    let fixed_area = match self {
        Self::X(fw, _) => [x, y, *fw, h],
        Self::Y(fh, _) => [x, y, w, *fh],
        Self::XY(fw, fh, _) => [x, y, *fw, *fh],
    };
    let [x, y, w, h] = Render::layout(&self.content(), fixed_area.into()).xywh();
    let fixed_area = match self {
        Self::X(fw, _) => [x, y, *fw, h],
        Self::Y(fh, _) => [x, y, w, *fh],
        Self::XY(fw, fh, _) => [x, y, *fw, *fh],
    };
    fixed_area
});

transform_xy_unit!("min/x" "min/y" "min/xy"|self: Min, area|{
    let area = Render::layout(&self.content(), 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!("max/x" "max/y" "max/xy"|self: Max, area|{
    let [x, y, w, h] = area.xywh();
    Render::layout(&self.content(), match self {
        Self::X(fw, _) => [x, y, *fw, h],
        Self::Y(fh, _) => [x, y, w, *fh],
        Self::XY(fw, fh, _) => [x, y, *fw, *fh],
    }.into())
});

transform_xy_unit!("shrink/x" "shrink/y" "shrink/xy"|self: Shrink, area|Render::layout(
    &self.content(),
    [area.x(), area.y(), area.w().minus(self.dx()), area.h().minus(self.dy())].into()));

transform_xy_unit!("expand/x" "expand/y" "expand/xy"|self: Expand, area|Render::layout(
    &self.content(),
    [area.x(), area.y(), area.w().plus(self.dx()), area.h().plus(self.dy())].into()));

transform_xy_unit!("push/x" "push/y" "push/xy"|self: Push, area|{
    let area = Render::layout(&self.content(), area);
    [area.x().plus(self.dx()), area.y().plus(self.dy()), area.w(), area.h()]
});

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

transform_xy_unit!("margin/x" "margin/y" "margin/xy"|self: Margin, area|{
    let area = Render::layout(&self.content(), area);
    let dx = self.dx();
    let dy = self.dy();
    [area.x().minus(dx), area.y().minus(dy), area.w().plus(dy.plus(dy)), area.h().plus(dy.plus(dy))]
});

transform_xy_unit!("padding/x" "padding/y" "padding/xy"|self: Padding, area|{
    let area = Render::layout(&self.content(), area);
    let dx = self.dx();
    let dy = self.dy();
    [area.x().plus(dx), area.y().plus(dy), area.w().minus(dy.plus(dy)), area.h().minus(dy.plus(dy))]
});