WIP: Wall intersection

[kaka/rust-sdl-test.git] / src / common / geometry.rs

use std::ops::{Add, AddAssign, Sub, SubAssign, Mul, MulAssign, Div, DivAssign, Neg};

////////// POINT ///////////////////////////////////////////////////////////////

#[macro_export]
macro_rules! point {
    ( $x:expr, $y:expr ) => {
        Point { x: $x, y: $y }
    };
}

#[derive(Debug, Default, Copy, Clone, PartialEq)]
pub struct Point<T> {
    pub x: T,
    pub y: T,
}

impl Point<f64> {
    pub fn length(&self) -> f64 {
        ((self.x * self.x) + (self.y * self.y)).sqrt()
    }

    pub fn normalized(&self) -> Self {
	let l = self.length();
	Self {
	    x: self.x / l,
	    y: self.y / l,
	}
    }

    pub fn to_radians(&self) -> Radians {
	Radians(self.y.atan2(self.x))
    }

    pub fn to_degrees(&self) -> Degrees {
	self.to_radians().to_degrees()
    }

    pub fn to_i32(self) -> Point<i32> {
	Point {
	    x: self.x as i32,
	    y: self.y as i32,
	}
    }
}

macro_rules! point_op {
    ($op:tt, $trait:ident($fn:ident), $trait_assign:ident($fn_assign:ident), $rhs:ident = $Rhs:ty => $x:expr, $y:expr) => {
        impl<T: $trait<Output = T>> $trait<$Rhs> for Point<T> {
            type Output = Self;

            fn $fn(self, $rhs: $Rhs) -> Self {
                Self {
                    x: self.x $op $x,
                    y: self.y $op $y,
                }
            }
        }

        impl<T: $trait<Output = T> + Copy> $trait_assign<$Rhs> for Point<T> {
            fn $fn_assign(&mut self, $rhs: $Rhs) {
                *self = Self {
                    x: self.x $op $x,
                    y: self.y $op $y,
                }
            }
        }
    }
}

point_op!(+, Add(add), AddAssign(add_assign), rhs = Point<T> => rhs.x, rhs.y);
point_op!(-, Sub(sub), SubAssign(sub_assign), rhs = Point<T> => rhs.x, rhs.y);
point_op!(*, Mul(mul), MulAssign(mul_assign), rhs = Point<T> => rhs.x, rhs.y);
point_op!(/, Div(div), DivAssign(div_assign), rhs = Point<T> => rhs.x, rhs.y);
point_op!(+, Add(add), AddAssign(add_assign), rhs = (T, T) => rhs.0, rhs.1);
point_op!(-, Sub(sub), SubAssign(sub_assign), rhs = (T, T) => rhs.0, rhs.1);
point_op!(*, Mul(mul), MulAssign(mul_assign), rhs = (T, T) => rhs.0, rhs.1);
point_op!(/, Div(div), DivAssign(div_assign), rhs = (T, T) => rhs.0, rhs.1);

////////// multiply point with scalar //////////////////////////////////////////
impl<T: Mul<Output = T> + Copy> Mul<T> for Point<T> {
    type Output = Self;

    fn mul(self, rhs: T) -> Self {
	Self {
	    x: self.x * rhs,
	    y: self.y * rhs,
	}
    }
}

impl<T: Mul<Output = T> + Copy> MulAssign<T> for Point<T> {
    fn mul_assign(&mut self, rhs: T) {
	*self = Self {
	    x: self.x * rhs,
	    y: self.y * rhs,
	}
    }
}

////////// divide point with scalar ////////////////////////////////////////////
impl<T: Div<Output = T> + Copy> Div<T> for Point<T> {
    type Output = Self;

    fn div(self, rhs: T) -> Self {
	Self {
	    x: self.x / rhs,
	    y: self.y / rhs,
	}
    }
}

impl<T: Div<Output = T> + Copy> DivAssign<T> for Point<T> {
    fn div_assign(&mut self, rhs: T) {
	*self = Self {
	    x: self.x / rhs,
	    y: self.y / rhs,
	}
    }
}

impl<T: Neg<Output = T>> Neg for Point<T> {
    type Output = Self;

    fn neg(self) -> Self {
	Self {
	    x: -self.x,
	    y: -self.y,
	}
    }
}

impl<T> From<(T, T)> for Point<T> {
    fn from(item: (T, T)) -> Self {
        Point {
            x: item.0,
            y: item.1,
        }
    }
}

impl<T> From<Point<T>> for (T, T) {
    fn from(item: Point<T>) -> Self {
        (item.x, item.y)
    }
}

impl From<Degrees> for Point<f64> {
    fn from(item: Degrees) -> Self {
	let r = item.0.to_radians();
        Point {
            x: r.cos(),
            y: r.sin(),
        }
    }
}

impl From<Radians> for Point<f64> {
    fn from(item: Radians) -> Self {
        Point {
            x: item.0.cos(),
            y: item.0.sin(),
        }
    }
}

#[derive(Debug, Default, PartialEq, Clone, Copy)]
pub struct Degrees(pub f64);
#[derive(Debug, Default, PartialEq, Clone, Copy)]
pub struct Radians(pub f64);

impl Degrees {
    #[allow(dead_code)]
    fn to_radians(&self) -> Radians {
	Radians(self.0.to_radians())
    }
}

impl Radians {
    #[allow(dead_code)]
    fn to_degrees(&self) -> Degrees {
	Degrees(self.0.to_degrees())
    }
}

////////// INTERSECTION ////////////////////////////////////////////////////////

#[derive(Debug)]
pub enum Intersection {
    Point(Point<f64>),
    //Line(Point<f64>, Point<f64>), // TODO: overlapping collinear
    None,
}

impl Intersection {
    pub fn lines(p1: Point<f64>, p2: Point<f64>, p3: Point<f64>, p4: Point<f64>) -> Intersection {
	let s1 = p2 - p1;
	let s2 = p4 - p3;

	let denomimator = -s2.x * s1.y + s1.x * s2.y;
	if denomimator != 0.0 {
	    let s = (-s1.y * (p1.x - p3.x) + s1.x * (p1.y - p3.y)) / denomimator;
	    let t = ( s2.x * (p1.y - p3.y) - s2.y * (p1.x - p3.x)) / denomimator;

	    if s >= 0.0 && s <= 1.0 && t >= 0.0 && t <= 1.0 {
		return Intersection::Point(p1 + (s1 * t))
	    }
	}

	Intersection::None
    }
}

////////// DIMENSION ///////////////////////////////////////////////////////////

#[macro_export]
macro_rules! dimen {
    ( $w:expr, $h:expr ) => {
        Dimension { width: $w, height: $h }
    };
}

#[derive(Debug, Default)]
pub struct Dimension<T> {
    pub width: T,
    pub height: T,
}

impl<T: Mul<Output = T> + Copy> Dimension<T> {
    #[allow(dead_code)]
    pub fn area(&self) -> T {
        self.width * self.height
    }
}

impl<T> From<(T, T)> for Dimension<T> {
    fn from(item: (T, T)) -> Self {
        Dimension {
            width: item.0,
            height: item.1,
        }
    }
}

////////// TESTS ///////////////////////////////////////////////////////////////

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn immutable_copy_of_point() {
        let a = point!(0, 0);
        let mut b = a; // Copy
        assert_eq!(a, b); // PartialEq
        b.x = 1;
        assert_ne!(a, b); // PartialEq
    }

    #[test]
    fn add_points() {
        let mut a = point!(1, 0);
        assert_eq!(a + point!(2, 2), point!(3, 2)); // Add
        a += point!(2, 2); // AddAssign
        assert_eq!(a, point!(3, 2));
        assert_eq!(point!(1, 0) + (2, 3), point!(3, 3));
    }

    #[test]
    fn sub_points() {
        let mut a = point!(1, 0);
        assert_eq!(a - point!(2, 2), point!(-1, -2));
        a -= point!(2, 2);
        assert_eq!(a, point!(-1, -2));
        assert_eq!(point!(1, 0) - (2, 3), point!(-1, -3));
    }

    #[test]
    fn mul_points() {
        let mut a = point!(1, 2);
        assert_eq!(a * 2, point!(2, 4));
        assert_eq!(a * point!(2, 3), point!(2, 6));
        a *= 2;
        assert_eq!(a, point!(2, 4));
        a *= point!(3, 1);
        assert_eq!(a, point!(6, 4));
        assert_eq!(point!(1, 0) * (2, 3), point!(2, 0));
    }

    #[test]
    fn div_points() {
        let mut a = point!(4, 8);
        assert_eq!(a / 2, point!(2, 4));
        assert_eq!(a / point!(2, 4), point!(2, 2));
        a /= 2;
        assert_eq!(a, point!(2, 4));
        a /= point!(2, 4);
        assert_eq!(a, point!(1, 1));
        assert_eq!(point!(6, 3) / (2, 3), point!(3, 1));
    }

    #[test]
    fn neg_point() {
        assert_eq!(point!(1, 1), -point!(-1, -1));
    }

    #[test]
    fn angles() {
	assert_eq!(Radians(0.0).to_degrees(), Degrees(0.0));
	assert_eq!(Radians(std::f64::consts::PI).to_degrees(), Degrees(180.0));
	assert_eq!(Degrees(180.0).to_radians(), Radians(std::f64::consts::PI));
	assert!((Point::from(Degrees(90.0)) - point!(0.0, 1.0)).length() < 0.001);
	assert!((Point::from(Radians(std::f64::consts::FRAC_PI_2)) - point!(0.0, 1.0)).length() < 0.001);
    }

    #[test]
    fn area_for_dimension_of_multipliable_type() {
        let r: Dimension<_> = (30, 20).into(); // the Into trait uses the From trait
        assert_eq!(r.area(), 30 * 20);
        // let a = Dimension::from(("a".to_string(), "b".to_string())).area(); // this doesn't work, because area() is not implemented for String
    }

    #[test]
    fn intersection_of_lines() {
        let p1 = point!(0.0, 0.0);
        let p2 = point!(2.0, 2.0);
        let p3 = point!(0.0, 2.0);
        let p4 = point!(2.0, 0.0);
	let r = Intersection::lines(p1, p2, p3, p4);
	if let Intersection::Point(p) = r {
            assert_eq!(p, point!(1.0, 1.0));
	} else {
	    panic!();
	}
    }
}