use std::{fmt::Display, marker::Destruct};

use crate::{
    layout::{Align, Axis, UiNum, Vec2},
    util::{LerpUtil, impl_op},
};

#[repr(C)]
#[derive(Debug, Copy, Clone, PartialEq, bytemuck::Pod, bytemuck::Zeroable, Default)]
pub struct UiVec2 {
    pub rel: Vec2,
    pub abs: Vec2,
}

impl UiVec2 {
    pub const ZERO: Self = Self {
        rel: Vec2::ZERO,
        abs: Vec2::ZERO,
    };

    /// expands this position into a sized region centered at self
    pub fn expand(&self, size: impl Into<Vec2>) -> UiRegion {
        let size = size.into();
        UiRegion {
            top_left: self.offset(-size / 2.0),
            bot_right: self.offset(size / 2.0),
        }
    }

    pub const fn abs(abs: impl const Into<Vec2>) -> Self {
        Self {
            rel: Vec2::ZERO,
            abs: abs.into(),
        }
    }

    pub const fn rel(rel: impl const Into<Vec2>) -> Self {
        Self {
            rel: rel.into(),
            abs: Vec2::ZERO,
        }
    }

    pub const fn shift(&mut self, offset: impl const Into<UiVec2>) {
        let offset = offset.into();
        *self += offset;
    }

    pub const fn offset(mut self, offset: impl const Into<UiVec2>) -> Self {
        self.shift(offset);
        self
    }

    pub const fn within(&self, region: &UiRegion) -> UiVec2 {
        let rel = self.rel.lerp(region.top_left.rel, region.bot_right.rel);
        let abs = self.abs + self.rel.lerp(region.top_left.abs, region.bot_right.abs);
        UiVec2 { rel, abs }
    }

    pub const fn outside(&self, region: &UiRegion) -> UiVec2 {
        let rel = self.rel.lerp_inv(region.top_left.rel, region.bot_right.rel);
        let abs = self.abs - rel.lerp(region.top_left.abs, region.bot_right.abs);
        UiVec2 { rel, abs }
    }

    pub fn axis_mut(&mut self, axis: Axis) -> UiScalarView<'_> {
        match axis {
            Axis::X => UiScalarView {
                rel: &mut self.rel.x,
                abs: &mut self.abs.x,
            },
            Axis::Y => UiScalarView {
                rel: &mut self.rel.y,
                abs: &mut self.abs.y,
            },
        }
    }

    pub fn axis(&self, axis: Axis) -> UiScalar {
        match axis {
            Axis::X => UiScalar {
                rel: self.rel.x,
                abs: self.abs.x,
            },
            Axis::Y => UiScalar {
                rel: self.rel.y,
                abs: self.abs.y,
            },
        }
    }

    /// reflection about an axis
    pub fn flip(&mut self, axis: Axis) {
        *self.rel.axis_mut(axis) = 1.0 - self.rel.axis(axis);
        *self.abs.axis_mut(axis) = -self.abs.axis(axis);
    }

    pub fn flipped(mut self, axis: Axis) -> Self {
        self.flip(axis);
        self
    }

    pub fn to_size(&self, size: Vec2) -> Vec2 {
        self.rel * size + self.abs
    }

    pub const MAX_SIZE: Self = Self::rel(Vec2::ONE);

    pub const fn from_axis(axis: Axis, aligned: UiScalar, ortho: UiScalar) -> Self {
        Self {
            rel: Vec2::from_axis(axis, aligned.rel, ortho.rel),
            abs: Vec2::from_axis(axis, aligned.abs, ortho.abs),
        }
    }
}

impl Display for UiVec2 {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "rel {} / abs {}", self.rel, self.abs)
    }
}

impl_op!(UiVec2 Add add; rel abs);
impl_op!(UiVec2 Sub sub; rel abs);

impl const From<Align> for UiVec2 {
    fn from(align: Align) -> Self {
        Self::rel(align.rel())
    }
}

impl Align {
    pub fn pos(self) -> UiVec2 {
        UiVec2::from(self)
    }
}

impl const From<Vec2> for UiVec2 {
    fn from(abs: Vec2) -> Self {
        Self::abs(abs)
    }
}

impl<T: const UiNum, U: const UiNum> const From<(T, U)> for UiVec2
where
    (T, U): const Destruct,
{
    fn from(abs: (T, U)) -> Self {
        Self::abs(abs)
    }
}

#[derive(Clone, Copy, Debug, Default)]
pub struct UiScalar {
    pub rel: f32,
    pub abs: f32,
}

impl_op!(UiScalar Add add; rel abs);
impl_op!(UiScalar Sub sub; rel abs);

impl UiScalar {
    pub const ZERO: Self = Self { rel: 0.0, abs: 0.0 };

    pub fn new(rel: f32, abs: f32) -> Self {
        Self { rel, abs }
    }
    pub fn rel_min() -> Self {
        Self::new(0.0, 0.0)
    }

    pub fn rel_max() -> Self {
        Self::new(1.0, 0.0)
    }

    pub fn max(&self, other: Self) -> Self {
        Self {
            rel: self.rel.max(other.rel),
            abs: self.abs.max(other.abs),
        }
    }

    pub fn min(&self, other: Self) -> Self {
        Self {
            rel: self.rel.min(other.rel),
            abs: self.abs.min(other.abs),
        }
    }

    pub fn from_anchor(anchor: f32) -> Self {
        Self::new(anchor, 0.0)
    }

    pub fn offset(mut self, amt: f32) -> Self {
        self.abs += amt;
        self
    }

    pub fn within(&self, start: UiScalar, end: UiScalar) -> Self {
        let anchor = self.rel.lerp(start.rel, end.rel);
        let offset = self.abs + self.rel.lerp(start.abs, end.abs);
        Self {
            rel: anchor,
            abs: offset,
        }
    }
}

#[repr(C)]
#[derive(Debug, Copy, Clone, PartialEq, bytemuck::Pod, bytemuck::Zeroable)]
pub struct UiRegion {
    pub top_left: UiVec2,
    pub bot_right: UiVec2,
}

impl UiRegion {
    pub const fn full() -> Self {
        Self {
            top_left: Align::TopLeft.into(),
            bot_right: Align::BotRight.into(),
        }
    }
    pub fn rel(anchor: Vec2) -> Self {
        Self {
            top_left: UiVec2::rel(anchor),
            bot_right: UiVec2::rel(anchor),
        }
    }
    pub fn within(&self, parent: &Self) -> Self {
        Self {
            top_left: self.top_left.within(parent),
            bot_right: self.bot_right.within(parent),
        }
    }
    pub fn outside(&self, parent: &Self) -> Self {
        Self {
            top_left: self.top_left.outside(parent),
            bot_right: self.bot_right.outside(parent),
        }
    }
    pub fn axis_mut(&mut self, axis: Axis) -> UIRegionAxisView<'_> {
        UIRegionAxisView {
            top_left: self.top_left.axis_mut(axis),
            bot_right: self.bot_right.axis_mut(axis),
        }
    }

    pub fn flip(&mut self, axis: Axis) {
        self.top_left.flip(axis);
        self.bot_right.flip(axis);
        let tl = self.top_left.axis_mut(axis);
        let br = self.bot_right.axis_mut(axis);
        std::mem::swap(tl.rel, br.rel);
        std::mem::swap(tl.abs, br.abs);
    }

    pub fn shift(&mut self, offset: impl Into<UiVec2>) {
        let offset = offset.into();
        self.top_left.shift(offset);
        self.bot_right.shift(offset);
    }

    pub fn offset(mut self, offset: impl Into<UiVec2>) -> Self {
        self.shift(offset);
        self
    }

    pub fn to_screen(&self, size: Vec2) -> ScreenRegion {
        ScreenRegion {
            top_left: self.top_left.rel * size + self.top_left.abs,
            bot_right: self.bot_right.rel * size + self.bot_right.abs,
        }
    }

    pub fn center(&self) -> UiVec2 {
        Align::Center.pos().within(self)
    }

    pub fn in_size(&self, size: Vec2) -> Vec2 {
        self.bot_right.to_size(size) - self.top_left.to_size(size)
    }

    pub fn size(&self) -> UiVec2 {
        self.bot_right - self.top_left
    }

    pub fn select_aligned(&self, size: Vec2, align: Align) -> Self {
        Self::from_size_align(size, align).within(self)
    }

    pub fn from_size_align(size: Vec2, align: Align) -> Self {
        let mut top_left = UiVec2::from(align);
        top_left.abs -= size * align.rel();
        let mut bot_right = UiVec2::from(align);
        bot_right.abs += size * (Vec2::ONE - align.rel());
        Self {
            top_left,
            bot_right,
        }
    }

    pub fn from_ui_size_align(size: UiVec2, align: Align) -> Self {
        let mut top_left = UiVec2::from(align);
        top_left.abs -= size.abs * align.rel();
        top_left.rel -= size.rel * align.rel();
        let mut bot_right = UiVec2::from(align);
        bot_right.abs += size.abs * (Vec2::ONE - align.rel());
        bot_right.rel += size.rel * (Vec2::ONE - align.rel());
        Self {
            top_left,
            bot_right,
        }
    }
}

impl Display for UiRegion {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} -> {}", self.top_left, self.bot_right)
    }
}

#[derive(Debug)]
pub struct ScreenRegion {
    pub top_left: Vec2,
    pub bot_right: Vec2,
}
impl ScreenRegion {
    pub fn contains(&self, pos: Vec2) -> bool {
        pos.x >= self.top_left.x
            && pos.x <= self.bot_right.x
            && pos.y >= self.top_left.y
            && pos.y <= self.bot_right.y
    }
}

pub struct UIRegionAxisView<'a> {
    pub top_left: UiScalarView<'a>,
    pub bot_right: UiScalarView<'a>,
}

pub struct UiScalarView<'a> {
    pub rel: &'a mut f32,
    pub abs: &'a mut f32,
}

impl UiScalarView<'_> {
    pub fn set(&mut self, scalar: UiScalar) {
        *self.rel = scalar.rel;
        *self.abs = scalar.abs;
    }
    pub fn get(self) -> UiScalar {
        UiScalar {
            rel: *self.rel,
            abs: *self.abs,
        }
    }
}