use std::f64;

const _EPS: f64 = 0.00001;
const _MIN: f64 = f64::MIN_POSITIVE;
const _MAX: f64 = f64::MAX;

#[derive(Clone)]
struct Point {
    x: f64,
    y: f64,
}

#[derive(Clone)]
struct Edge {
    pt1: Point,
    pt2: Point,
}

impl Edge {
    fn new(pt1: (f64, f64), pt2: (f64, f64)) -> Edge {
        Edge {
            pt1: Point { x: pt1.0, y: pt1.1 },
            pt2: Point { x: pt2.0, y: pt2.1 },
        }
    }
}

struct Polygon {
    edges: Vec<Edge>, // Polygon has to be created with counter-clockwise coordinates
}

fn pt_in_polygon(pt: &Point, poly: &Polygon) -> bool {
    let count = poly.edges
        .iter()
        .filter(|edge| ray_intersect_seg(pt, edge))
        .count();

    count % 2 == 1
}

fn ray_intersect_seg(p: &Point, edge: &Edge) -> bool {
    let mut pt = p.clone();
    let (mut a, mut b): (&Point, &Point) = (&edge.pt1, &edge.pt2);
    if a.y > b.y {
        std::mem::swap(&mut a, &mut b);
    }
    if pt.y == a.y || pt.y == b.y {
        pt.y += _EPS;
    }

    if (pt.y > b.y || pt.y < a.y) || pt.x > a.x.max(b.x) {
        false
    } else if pt.x < a.x.min(b.x) {
        true
    } else {
        let m_red = if (a.x - b.x).abs() > _MIN {
            (b.y - a.y) / (b.x - a.x)
        } else {
            _MAX
        };
        let m_blue = if (a.x - pt.x).abs() > _MIN {
            (pt.y - a.y) / (pt.x - a.x)
        } else {
            _MAX
        };
        m_blue >= m_red
    }
}

fn main() {
    let p = |x, y| Point { x, y };
    let testpoints = [p(5.0, 5.0), p(5.0, 8.0), p(-10.0, 5.0), p(0.0, 5.0), p(10.0, 5.0), p(8.0, 5.0), p(10.0, 10.0)];
    let poly_square = Polygon {
        edges: vec![
            Edge::new((0.0, 0.0), (10.0, 0.0)),
            Edge::new((10.0, 0.0), (10.0, 10.0)),
            Edge::new((10.0, 10.0), (0.0, 10.0)),
            Edge::new((0.0, 10.0), (0.0, 0.0)),
        ],
    };
    let poly_square_hole = Polygon {
        edges: vec![
            Edge::new((0.0, 0.0), (10.0, 0.0)),
            Edge::new((10.0, 0.0), (10.0, 10.0)),
            Edge::new((10.0, 10.0), (0.0, 10.0)),
            Edge::new((0.0, 10.0), (0.0, 0.0)),
            Edge::new((2.5, 2.5), (7.5, 2.5)),
            Edge::new((7.5, 2.5), (7.5, 7.5)),
            Edge::new((7.5, 7.5), (2.5, 7.5)),
            Edge::new((2.5, 7.5), (2.5, 2.5)),
        ],
    };
    let poly_strange = Polygon {
        edges: vec![
            Edge::new((0.0, 0.0), (2.5, 2.5)),
            Edge::new((2.5, 2.5), (0.0, 10.0)),
            Edge::new((0.0, 10.0), (2.5, 7.5)),
            Edge::new((2.5, 7.5), (7.5, 7.5)),
            Edge::new((7.5, 7.5), (10.0, 10.0)),
            Edge::new((10.0, 10.0), (10.0, 0.0)),
            Edge::new((10.0, 0.0), (2.5, 2.5)),
        ],
    };
    let poly_hexagon = Polygon {
        edges: vec![
            Edge::new((3.0, 0.0), (7.0, 0.0)),
            Edge::new((7.0, 0.0), (10.0, 5.0)),
            Edge::new((10.0, 5.0), (7.0, 10.0)),
            Edge::new((7.0, 10.0), (3.0, 10.0)),
            Edge::new((3.0, 10.0), (0.0, 5.0)),
            Edge::new((0.0, 5.0), (3.0, 0.0)),
        ],
    };
    print!("\nSquare :");
    for pt in &testpoints {
        print!(" {:?}", pt_in_polygon(pt, &poly_square));
    }
    print!("\nSquare with hole:");
    for pt in &testpoints {
        print!(" {:?}", pt_in_polygon(pt, &poly_square_hole));
    }
    print!("\nStrange polygon :");
    for pt in &testpoints {
        print!(" {:?}", pt_in_polygon(pt, &poly_strange));
    }
    print!("\nHexagon :");
    for pt in &testpoints {
        print!(" {:?}", pt_in_polygon(pt, &poly_hexagon));
    }
    println!();
}