use geometry::*;

pub enum Hitbox {
    Circle(CircleHitbox),
    Point(PointHitbox),
    Capsule(CapsuleHitbox)
}

pub struct CircleHitbox {
    pub pos: Vec2d,
    pub radius: f64
}

pub struct PointHitbox {
    pub pos: Vec2d
}

pub struct CapsuleHitbox {
    pub line: LineSegment,
    pub radius: f64        
}

impl Hitbox {
    pub fn intersect(a: &Hitbox, b: &Hitbox) -> bool {
        use self::Hitbox::*;

        match (a, b) {
            (Circle(x), Circle(y)) => circles_intersect(x, y),
            (Circle(x), Point(y)) => circle_point_intersect(x, y),
            (Point(x), Circle(y)) => circle_point_intersect(y, x),
            (Point(x), Point(y)) => points_intersect(x, y),
            (Capsule(x), Capsule(y)) => capsules_intersect(x, y),
            (Capsule(x), Circle(y)) => capsule_circle_intersect(x, y),
            (Circle(x), Capsule(y)) => capsule_circle_intersect(y, x),
            (Capsule(x), Point(y)) => capsule_point_intersect(x, y),
            (Point(x), Capsule(y)) => capsule_point_intersect(y, x),
        }
    }
}

fn circles_intersect(x: &CircleHitbox, y: &CircleHitbox) -> bool {
    x.pos.distance_squared(y.pos) <= (x.radius + y.radius).powi(2)
}

fn circle_point_intersect(x: &CircleHitbox, y: &PointHitbox) -> bool {
    x.pos.distance_squared(y.pos) <= x.radius.powi(2)
}

fn points_intersect(x: &PointHitbox, y: &PointHitbox) -> bool {
    x.pos == y.pos
}

fn capsules_intersect(x: &CapsuleHitbox, y: &CapsuleHitbox) -> bool {
    true //TODO
}

fn capsule_circle_intersect(x: &CapsuleHitbox, y: &CircleHitbox) -> bool {
    x.line.distance(y.pos) <= x.radius + y.radius
}

fn capsule_point_intersect(x: &CapsuleHitbox, y: &PointHitbox) -> bool {
    x.line.distance(y.pos) <= x.radius
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn circle_intersecting_circle_origin_example() {
        assert_eq!(Hitbox::intersect(
            &Hitbox::Circle(CircleHitbox {
                pos: Vec2d::new(0.,0.),
                radius: 0.
            }),
            &Hitbox::Circle(CircleHitbox {
                pos: Vec2d::new(0.,0.),
                radius: 0.
            })
        ), true);
    }

    #[test]
    fn circle_intersecting_circle_origin_elsewhere() {
        assert_eq!(Hitbox::intersect(
            &Hitbox::Circle(CircleHitbox {
                pos: Vec2d::new(0.,0.),
                radius: 0.5
            }),
            &Hitbox::Circle(CircleHitbox {
                pos: Vec2d::new(1.,0.),
                radius: 0.5
            })
        ), true);
    }

    #[test]
    fn circle_intersecting_circle_origin_outside() {
        assert_eq!(Hitbox::intersect(
            &Hitbox::Circle(CircleHitbox {
                pos: Vec2d::new(0.,0.),
                radius: 0.5
            }),
            &Hitbox::Circle(CircleHitbox {
                pos: Vec2d::new(1.,0.),
                radius: 0.4
            })
        ), false);
    }
}