use crate::vec2;

use super::*;

#[derive(Clone, Copy, PartialEq)]
pub struct Align {
    pub x: Option<AxisAlign>,
    pub y: Option<AxisAlign>,
}

impl Align {
    pub const TOP_LEFT: RegionAlign = RegionAlign::TOP_LEFT;
    pub const TOP_CENTER: RegionAlign = RegionAlign::TOP_CENTER;
    pub const TOP_RIGHT: RegionAlign = RegionAlign::TOP_RIGHT;
    pub const CENTER_LEFT: RegionAlign = RegionAlign::CENTER_LEFT;
    pub const CENTER: RegionAlign = RegionAlign::CENTER;
    pub const CENTER_RIGHT: RegionAlign = RegionAlign::CENTER_RIGHT;
    pub const BOT_LEFT: RegionAlign = RegionAlign::BOT_LEFT;
    pub const BOT_CENTER: RegionAlign = RegionAlign::BOT_CENTER;
    pub const BOT_RIGHT: RegionAlign = RegionAlign::BOT_RIGHT;
    pub const LEFT: CardinalAlign = CardinalAlign::LEFT;
    pub const H_CENTER: CardinalAlign = CardinalAlign::H_CENTER;
    pub const RIGHT: CardinalAlign = CardinalAlign::RIGHT;
    pub const TOP: CardinalAlign = CardinalAlign::TOP;
    pub const V_CENTER: CardinalAlign = CardinalAlign::V_CENTER;
    pub const BOT: CardinalAlign = CardinalAlign::BOT;

    pub fn tuple(&self) -> (Option<AxisAlign>, Option<AxisAlign>) {
        (self.x, self.y)
    }
}

/// Where a widget sits in a box longer than it is. The default is the middle,
/// because the two edges are the ones that assume a direction: which of them
/// is the near one depends on the writing system and on which way a container
/// runs, and the middle is the same either way.
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct AxisAlign(f32);

impl AxisAlign {
    pub const NEG: Self = Self::new(0.0);
    pub const CENTER: Self = Self::new(0.5);
    pub const POS: Self = Self::new(1.0);

    pub const fn new(rel: f32) -> Self {
        Self(rel)
    }

    pub const fn rel(&self) -> f32 {
        self.0
    }
}

impl Default for AxisAlign {
    fn default() -> Self {
        Self::CENTER
    }
}

pub struct CardinalAlign {
    axis: Axis,
    align: AxisAlign,
}

impl CardinalAlign {
    pub const LEFT: Self = Self::new(Axis::X, AxisAlign::NEG);
    pub const H_CENTER: Self = Self::new(Axis::X, AxisAlign::CENTER);
    pub const RIGHT: Self = Self::new(Axis::X, AxisAlign::POS);
    pub const TOP: Self = Self::new(Axis::Y, AxisAlign::NEG);
    pub const V_CENTER: Self = Self::new(Axis::Y, AxisAlign::CENTER);
    pub const BOT: Self = Self::new(Axis::Y, AxisAlign::POS);

    pub const fn new(axis: Axis, align: AxisAlign) -> Self {
        Self { axis, align }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub struct RegionAlign {
    pub x: AxisAlign,
    pub y: AxisAlign,
}

impl RegionAlign {
    /// Both axes at the near edge. What a container passes as an override for
    /// a child it is going to position itself.
    pub const NEAR: Self = Self {
        x: AxisAlign::NEG,
        y: AxisAlign::NEG,
    };

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

    pub fn axis_mut(&mut self, axis: Axis) -> &mut AxisAlign {
        match axis {
            Axis::X => &mut self.x,
            Axis::Y => &mut self.y,
        }
    }
}

impl RegionAlign {
    pub const TOP_LEFT: Self = Self::new(AxisAlign::NEG, AxisAlign::NEG);
    pub const TOP_CENTER: Self = Self::new(AxisAlign::CENTER, AxisAlign::NEG);
    pub const TOP_RIGHT: Self = Self::new(AxisAlign::POS, AxisAlign::NEG);
    pub const CENTER_LEFT: Self = Self::new(AxisAlign::NEG, AxisAlign::CENTER);
    pub const CENTER: Self = Self::new(AxisAlign::CENTER, AxisAlign::CENTER);
    pub const CENTER_RIGHT: Self = Self::new(AxisAlign::POS, AxisAlign::CENTER);
    pub const BOT_LEFT: Self = Self::new(AxisAlign::NEG, AxisAlign::POS);
    pub const BOT_CENTER: Self = Self::new(AxisAlign::CENTER, AxisAlign::POS);
    pub const BOT_RIGHT: Self = Self::new(AxisAlign::POS, AxisAlign::POS);

    pub const fn new(x: AxisAlign, y: AxisAlign) -> Self {
        Self { x, y }
    }
    pub const fn rel(&self) -> Vec2 {
        vec2(self.x.rel(), self.y.rel())
    }
}

impl UiVec2 {
    pub fn partial_align(&self, align: Align) -> UiRegion {
        UiRegion {
            x: if let Some(align) = align.x {
                self.x.align(align)
            } else {
                UiSpan::FULL
            },
            y: if let Some(align) = align.y {
                self.y.align(align)
            } else {
                UiSpan::FULL
            },
        }
    }

    pub fn align(&self, align: RegionAlign) -> UiRegion {
        UiRegion {
            x: self.x.align(align.x),
            y: self.y.align(align.y),
        }
    }
}

impl Vec2 {
    pub fn partial_align(&self, align: Align) -> UiRegion {
        let s = UiVec2::from(*self);
        UiRegion {
            x: if let Some(align) = align.x {
                s.x.align(align)
            } else {
                UiSpan::FULL
            },
            y: if let Some(align) = align.y {
                s.y.align(align)
            } else {
                UiSpan::FULL
            },
        }
    }

    pub fn align(&self, align: RegionAlign) -> UiRegion {
        let s = UiVec2::from(*self);
        UiRegion {
            x: s.x.align(align.x),
            y: s.y.align(align.y),
        }
    }
}

impl UiScalar {
    pub const fn align(&self, align: AxisAlign) -> UiSpan {
        let rel = align.rel();
        let mut start = UiScalar::rel(rel);
        start.px -= self.px * rel;
        start.rel -= self.rel * rel;
        let mut end = UiScalar::rel(rel);
        end.px += self.px * (1.0 - rel);
        end.rel += self.rel * (1.0 - rel);
        UiSpan { start, end }
    }
}

impl From<RegionAlign> for Align {
    fn from(region: RegionAlign) -> Self {
        Self {
            x: Some(region.x),
            y: Some(region.y),
        }
    }
}

impl From<Align> for RegionAlign {
    fn from(align: Align) -> Self {
        Self {
            x: align.x.unwrap_or(AxisAlign::CENTER),
            y: align.y.unwrap_or(AxisAlign::CENTER),
        }
    }
}

impl From<CardinalAlign> for RegionAlign {
    fn from(align: CardinalAlign) -> Self {
        Align::from(align).into()
    }
}

impl From<CardinalAlign> for Align {
    fn from(cardinal: CardinalAlign) -> Self {
        let align = Some(cardinal.align);
        match cardinal.axis {
            Axis::X => Self { x: align, y: None },
            Axis::Y => Self { x: None, y: align },
        }
    }
}

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

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