//! Support function for 2D geometry
//!

/// Position on the map
#[derive(Default, PartialEq, Copy, Clone, Debug, Eq, Hash)]
pub struct Point {
    pub x: usize,
    pub y: usize,
}

impl Point {
    /// Create new point
    pub fn new(x: usize, y: usize) -> Point {
        Point { x, y }
    }

    /// Create new point from i32 coords
    pub fn new_i32(x: i32, y: i32) -> Point {
        Point::new(x as usize, y as usize)
    }

    /// Euclidean distance to a given point
    pub fn distance_to(self, point: &Point) -> f32 {
        let a = (self.x as f32 - point.x as f32).powf(2.0);
        let b = (self.y as f32 - point.y as f32).powf(2.0);
        (a + b).sqrt()
    }
}

/// Rectangle region on the map
#[derive(Hash, PartialEq, Eq, Copy, Clone, Debug)]
pub struct Rect {
    pub x1: usize,
    pub x2: usize,
    pub y1: usize,
    pub y2: usize,
}

impl Rect {
    pub fn new(x: usize, y: usize, width: usize, height: usize) -> Rect {
        Rect {
            x1: x,
            y1: y,
            x2: x + width,
            y2: y + height,
        }
    }

    pub fn new_i32(x: i32, y: i32, width: i32, height: i32) -> Rect {
        Rect::new(x as usize, y as usize, width as usize, height as usize)
    }

    /// Returns `true` if this overlaps with `other`
    pub fn intersect(&self, other: &Rect) -> bool {
        self.x1 <= other.x2 && self.x2 >= other.x1 && self.y1 <= other.y2 && self.y2 >= other.y1
    }

    /// Returns `true` if this contains `point`
    pub fn contains(self, point: &Point) -> bool {
        point.x > self.x1 && point.x < self.x2 && point.y > self.y1 && point.y < self.y2
    }

    pub fn center(&self) -> Point {
        Point::new((self.x1 + self.x2) / 2, (self.y1 + self.y2) / 2)
    }

    pub fn width(&self) -> usize {
        if self.x2 >= self.x1 {
            self.x2 - self.x1
        } else {
            self.x1 - self.x2
        }
    }

    pub fn height(&self) -> usize {
        if self.y2 >= self.y1 {
            self.y2 - self.y1
        } else {
            self.y1 - self.y2
        }
    }
}

/// Calculate abs value between 2 usize values
/// Example:
/// ```
/// use here_be_dragons::geometry::usize_abs;
///
/// assert_eq!(usize_abs(5, 3), 2);
/// assert_eq!(usize_abs(3, 5), 2);
/// ```
pub fn usize_abs(x: usize, y: usize) -> usize {
    if x >= y {
        x - y
    } else {
        y - x
    }
}

/// ------------------------------------------------------------------------------------------------
/// Module unit tests
/// ------------------------------------------------------------------------------------------------
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_distance() {
        let p1 = Point::new(10, 10);
        let p2 = Point::new(14, 7);
        let distance = p1.distance_to(&p2);
        assert_eq!(distance, 5.0);
    }

    #[test]
    fn test_intersect() {
        let rect1 = Rect::new(10, 10, 40, 40);
        let rect2 = Rect::new(30, 30, 60, 60);
        assert!(rect1.intersect(&rect2));
    }

    #[test]
    fn test_contains() {
        let rect = Rect::new(10, 10, 5, 5);
        assert!(rect.contains(&rect.center()));
        let p = Point::new(5, 5);
        assert!(!rect.contains(&p));
        let p = Point::new(10, 10);
        assert!(!rect.contains(&p));
        let p = Point::new(11, 11);
        assert!(rect.contains(&p));
    }

    #[test]
    fn test_size() {
        let rect1 = Rect::new(10, 10, 40, 30);
        assert_eq!(rect1.width(), 40);
        assert_eq!(rect1.height(), 30);
    }
}
