gemath 0.1.0

Type-safe game math with type-level units/spaces, typed angles, and explicit fallible ops (plus optional geometry/collision).
Documentation 
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use crate::vec2::*;
use crate::math;
use core::marker::PhantomData;

#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub struct Rect2<Unit: Copy = (), Space: Copy = ()> {
    pub pos: Vec2<Unit, Space>,
    pub dim: Vec2<Unit, Space>,
    #[cfg_attr(feature = "serde", serde(skip))]
    _unit: PhantomData<Unit>,
    #[cfg_attr(feature = "serde", serde(skip))]
    _space: PhantomData<Space>,
}

// Type aliases for common units and spaces
pub type Rect2f32 = Rect2<(),()>;
pub type Rect2Meters = Rect2<Meters,()>;
pub type Rect2Pixels = Rect2<Pixels,()>;
pub type Rect2World = Rect2<(),World>;
pub type Rect2Local = Rect2<(),Local>;
pub type Rect2Screen = Rect2<(),Screen>;
pub type Rect2MetersWorld = Rect2<Meters,World>;
pub type Rect2PixelsScreen = Rect2<Pixels,Screen>;

impl<Unit: Copy, Space: Copy> Rect2<Unit, Space> {
    #[inline]
    pub const fn new(pos: Vec2<Unit, Space>, dim: Vec2<Unit, Space>) -> Self {
        Self { pos, dim, _unit: PhantomData, _space: PhantomData }
    }

    /// Creates a Rect2 from an array of 4 floats: [pos.x, pos.y, dim.x, dim.y].
    #[inline]
    pub const fn from_array(v: [f32; 4]) -> Self {
        Self {
            pos: Vec2::new(v[0], v[1]),
            dim: Vec2::new(v[2], v[3]),
            _unit: PhantomData,
            _space: PhantomData,
        }
    }

    /// Creates a Rect2 from a slice of 4 floats: [pos.x, pos.y, dim.x, dim.y].
    #[inline]
    pub fn from_slice(v: &[f32; 4]) -> Self {
        Self {
            pos: Vec2::new(v[0], v[1]),
            dim: Vec2::new(v[2], v[3]),
            _unit: PhantomData,
            _space: PhantomData,
        }
    }

    /// Checks if a point (x, y) is contained within the rectangle.
    /// The rectangle's position is its minimum corner, and its dimensions are positive.
    /// Points on the minimum edges are considered inside, points on the maximum edges are not.
    #[inline]
    pub fn contains_point_coords(&self, x: f32, y: f32) -> bool {
        let min_x = self.pos.x.min(self.pos.x + self.dim.x);
        let max_x = self.pos.x.max(self.pos.x + self.dim.x);
        let min_y = self.pos.y.min(self.pos.y + self.dim.y);
        let max_y = self.pos.y.max(self.pos.y + self.dim.y);
        x >= min_x && x < max_x && y >= min_y && y < max_y
    }

    /// Checks if a Vec2 point is contained within the rectangle.
    #[inline]
    pub fn contains_point(&self, p: Vec2<Unit, Space>) -> bool {
        self.contains_point_coords(p.x, p.y)
    }

    /// Checks if this rectangle intersects with another rectangle.
    #[inline]
    pub fn intersects(&self, other: &Self) -> bool {
        self.intersection(other).is_some()
    }

    /// Calculates the intersection of this rectangle with another.
    /// Returns Some(Rect2) if they intersect, None otherwise.
    /// The resulting rectangle will have its position as the minimum corner
    /// and positive dimensions.
    #[inline]
    pub fn intersection(&self, other: &Self) -> Option<Self> {
        let a_min_x = self.pos.x.min(self.pos.x + self.dim.x);
        let a_max_x = self.pos.x.max(self.pos.x + self.dim.x);
        let a_min_y = self.pos.y.min(self.pos.y + self.dim.y);
        let a_max_y = self.pos.y.max(self.pos.y + self.dim.y);

        let b_min_x = other.pos.x.min(other.pos.x + other.dim.x);
        let b_max_x = other.pos.x.max(other.pos.x + other.dim.x);
        let b_min_y = other.pos.y.min(other.pos.y + other.dim.y);
        let b_max_y = other.pos.y.max(other.pos.y + other.dim.y);

        let x0 = a_min_x.max(b_min_x);
        let y0 = a_min_y.max(b_min_y);
        let x1 = a_max_x.min(b_max_x);
        let y1 = a_max_y.min(b_max_y);

        if x0 < x1 && y0 < y1 {
            Some(Self::new(Vec2::new(x0, y0), Vec2::new(x1 - x0, y1 - y0)))
        } else {
            None
        }
    }

    /// Returns the minimum corner of the rectangle.
    pub const fn min(&self) -> Vec2<Unit, Space> {
        Vec2::new(
            self.pos.x.min(self.pos.x + self.dim.x),
            self.pos.y.min(self.pos.y + self.dim.y),
        )
    }

    /// Returns the maximum corner of the rectangle.
    pub const fn max(&self) -> Vec2<Unit, Space> {
        Vec2::new(
            self.pos.x.max(self.pos.x + self.dim.x),
            self.pos.y.max(self.pos.y + self.dim.y),
        )
    }

    /// Returns the size (width, height) of the rectangle (always positive).
    pub fn size(&self) -> Vec2<Unit, Space> {
        Vec2::new(self.dim.x.abs(), self.dim.y.abs())
    }

    /// Returns the area of the rectangle.
    pub fn area(&self) -> f32 {
        let s = self.size();
        s.x * s.y
    }

    /// Returns true if the rectangle is empty (any size <= 0).
    pub fn is_empty(&self) -> bool {
        self.dim.x == 0.0 || self.dim.y == 0.0
    }

    /// Constructs a Rect2 from min and max corners.
    pub fn from_min_max(min: Vec2<Unit, Space>, max: Vec2<Unit, Space>) -> Self {
        Self {
            pos: min,
            dim: max - min,
            _unit: PhantomData,
            _space: PhantomData,
        }
    }

    /// Returns a new Rect2 expanded to include the given point.
    pub fn expand_to_include(&self, point: Vec2<Unit, Space>) -> Self {
        let min = self.min();
        let max = self.max();
        let new_min = Vec2::new(min.x.min(point.x), min.y.min(point.y));
        let new_max = Vec2::new(max.x.max(point.x), max.y.max(point.y));
        Self::from_min_max(new_min, new_max)
    }

    /// Returns the union (smallest Rect containing both) of self and other.
    pub fn union(&self, other: &Self) -> Self {
        let min = self.min().min(other.min());
        let max = self.max().max(other.max());
        Self::from_min_max(min, max)
    }

    /// Transforms the rectangle by a Mat4. Returns the smallest Rect2 containing the transformed corners.
    /// Only the 2D part of the matrix is used (x, y, translation). Ignores z/w.
    #[cfg(feature = "mat4")]
    pub fn transform(&self, mat: &crate::mat4::Mat4) -> Self {
        let min = self.min();
        let max = self.max();
        let corners: [Vec2; 4] = [
            Vec2::new(min.x, min.y),
            Vec2::new(min.x, max.y),
            Vec2::new(max.x, min.y),
            Vec2::new(max.x, max.y),
        ];
        let mut tmin = Vec2::new(f32::INFINITY, f32::INFINITY);
        let mut tmax = Vec2::new(f32::NEG_INFINITY, f32::NEG_INFINITY);
        for &c in &corners {
            let v = mat.transform_point(crate::vec3::Vec3::new(c.x, c.y, 0.0));
            tmin = tmin.min(Vec2::new(v.x, v.y));
            tmax = tmax.max(Vec2::new(v.x, v.y));
        }
        Self::from_min_max(tmin, tmax)
    }

    /// Returns the closest point in the rectangle to the given point.
    pub fn closest_point(&self, point: Vec2<Unit, Space>) -> Vec2<Unit, Space> {
        let min = self.min();
        let max = self.max();
        point.clamp(min, max)
    }

    /// Returns the distance from the rectangle to the given point (0 if inside).
    pub fn distance(&self, point: Vec2<Unit, Space>) -> f32 {
        let min = self.min();
        let max = self.max();
        let dx = if point.x < min.x {
            min.x - point.x
        } else if point.x > max.x {
            point.x - max.x
        } else {
            0.0
        };
        let dy = if point.y < min.y {
            min.y - point.y
        } else if point.y > max.y {
            point.y - max.y
        } else {
            0.0
        };
        math::sqrt(dx * dx + dy * dy)
    }

    /// Ray-Rect intersection (slab method). Returns Some(t) for the first intersection, or None if no hit.
    /// Ray: origin + t * dir, t >= 0. Returns smallest t >= 0.
    pub fn intersect_ray(&self, origin: Vec2<Unit, Space>, dir: Vec2<Unit, Space>) -> Option<f32> {
        let min = self.min();
        let max = self.max();
        let mut tmin = (min.x - origin.x) / dir.x;
        let mut tmax = (max.x - origin.x) / dir.x;
        if tmin > tmax {
            core::mem::swap(&mut tmin, &mut tmax);
        }
        let mut tymin = (min.y - origin.y) / dir.y;
        let mut tymax = (max.y - origin.y) / dir.y;
        if tymin > tymax {
            core::mem::swap(&mut tymin, &mut tymax);
        }
        if (tmin > tymax) || (tymin > tmax) {
            return None;
        }
        tmin = tmin.max(tymin);
        tmax = tmax.min(tymax);
        if tmax < 0.0 {
            return None;
        }
        Some(if tmin >= 0.0 { tmin } else { tmax })
    }
}

// Example: conversion from Rect2<Meters> to Rect2<Pixels>
impl<Space: Copy> Rect2<Meters, Space> {
    pub fn to_pixels(self, scale: f32) -> Rect2<Pixels, Space> {
        Rect2 {
            pos: self.pos.to_pixels(scale),
            dim: self.dim.to_pixels(scale),
            _unit: PhantomData,
            _space: PhantomData,
        }
    }
}