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extern crate rand;
extern crate pythagoras;

use std::cmp::Ordering;
use std::f64;
use super::super::tools::roll;
use super::super::Coordinate;
use std::ops::Add;

// Constructs a vector of generic structs from a given list convered to Coordinates.
pub fn from_list<T>(list: &[(i16, i16)], get: &Fn(Coordinate, usize) -> T) -> Vec<T> {
        let mut result: Vec<T> = Vec::new();
        for (i, &(x,y)) in list.iter().enumerate() {
            result.push(get(Coordinate::new(x, y), i));
        }
        result
}

// Constructs a randomly positioned coordinate.
pub fn gen() -> Coordinate {
    Coordinate {
        x: rand::random::<i16>(),
        y: rand::random::<i16>(),
    }
}

/// Get difference in distance.
/// # Examples
/// ```
/// use pathfinder::Coordinate;
/// use pathfinder::node::coordinates::*;
/// let c1 = Coordinate::new(0,0);
/// let c2 = Coordinate::new(100,100);
/// let difference = c1.diff(c2);
/// assert_eq!(difference, (100, 100));
/// ```
pub fn diff(c1: Coordinate, c2: Coordinate) -> (i16, i16) {
    ((c1.x - c2.x).abs(), (c1.y - c2.y).abs())
}

/// Get the distance between two Coordinates'.
/// # Examples
/// ```
/// use pathfinder::Coordinate;
/// use pathfinder::node::coordinates::distance;
/// let a = Coordinate::new(0, 0);
/// let b = Coordinate::new(3,4);
/// let distance = distance(a, b);
/// assert_eq!(distance, 5);
/// ```
pub fn distance(a: Coordinate, b: Coordinate) -> u32 {
    let diff = diff(a, b);
    pythagoras::theorem(diff.0, diff.1) as u32
}

/// Generate a Coordinate from a given Coordinate and randomly places it within a radius.
/// # Examples
/// ```
/// use pathfinder::Coordinate;
/// use pathfinder::node::coordinates::*;
/// let c1 = Coordinate::new(0,0);
/// let c2 = gen_within_radius(c1, 100);
/// ```
pub fn gen_within_radius(coord: Coordinate, radius: u32) -> Coordinate {
    gen_radius(coord, 0, radius)
}

/// Generate a Coordinate from a given Coordinate and randomly places it within a min and max radius.
/// # Examples
/// ```
/// use pathfinder::Coordinate;
/// use pathfinder::node::coordinates::*;
/// let c1 = Coordinate::new(0,0);
/// let c2 = gen_radius(c1, 50, 100);
/// ```
pub fn gen_radius(coord: Coordinate, min: u32, max: u32) -> Coordinate {
    // Randomly gets the radius of the circle.
    let r = f64::from(roll(min, max));

    // gets a point on the circle's circumference.
    let circle = |a: f64, b: f64| a + r * b;

    // Gets a random angle.
    let angle = roll(0, 3600);
    let a: f64 = f64::consts::PI * 0.001 * f64::from(angle);

    // x = cx + r * cos(a)
    let x = circle(f64::from(coord.x), a.cos()) as i16;
    // y = cy + r * sin(a)
    let y = circle(f64::from(coord.y), a.sin()) as i16;

    Coordinate {
        x,
        y
    }
}

impl Ord for Coordinate {
    fn cmp(&self, other: &Coordinate) -> Ordering {
        (self.x + self.y).cmp(&(other.x + other.y))
    }
}

impl PartialOrd for Coordinate {
    fn partial_cmp(&self, other: &Coordinate) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl PartialEq for Coordinate {
    fn eq(&self, other: &Coordinate) -> bool {
        (self.x == other.x) && (self.y == other.y)
    }
}

impl Add for Coordinate {
    type Output = Coordinate;
    fn add(self, other: Coordinate) -> Coordinate {
        Coordinate::new(self.x + other.x, self.y + other.y)
    }
}