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use crate::geometry::{F64Ext, Transform, Transformation, Vector};
use std::ops::{Add, AddAssign, Sub, SubAssign};

/// A point in 2-dimensional Euclidian space.
///
/// A point represents a position, whereas a vector represents a displacement. That is, the result
/// of subtracting two points is a vector. Moreover, the result of adding/subtracting a vector
/// to/from a point is another point. However, adding two points is not defined. Similarly, whereas
/// a point can be scaled, rotated, and translated, a vector can only be scaled and rotated.
#[derive(Clone, Copy, Debug, Default, PartialEq, PartialOrd)]
pub struct Point {
    pub x: f64,
    pub y: f64,
}

impl Point {
    /// Creates a new point with the given coordinates.
    pub fn new(x: f64, y: f64) -> Point {
        Point { x, y }
    }

    /// Returns the point at the origin.
    pub fn origin() -> Point {
        Point::new(0.0, 0.0)
    }

    /// Converts `self` to a vector.
    ///
    /// This is equivalent to subtracting `self` from the origin.
    pub fn to_vector(self) -> Vector {
        Vector::new(self.x, self.y)
    }

    /// Linearly interpolate between `self` and `other` with parameter `t`.
    pub fn lerp(self, other: Point, t: f64) -> Point {
        Point::new(self.x.ext_lerp(other.x, t), self.y.ext_lerp(other.y, t))
    }
}

impl AddAssign<Vector> for Point {
    fn add_assign(&mut self, vector: Vector) {
        *self = *self + vector;
    }
}

impl SubAssign<Vector> for Point {
    fn sub_assign(&mut self, vector: Vector) {
        *self = *self - vector;
    }
}

impl Add<Vector> for Point {
    type Output = Point;

    fn add(self, v: Vector) -> Point {
        Point::new(self.x + v.x, self.y + v.y)
    }
}

impl Sub for Point {
    type Output = Vector;

    fn sub(self, other: Point) -> Vector {
        Vector::new(self.x - other.x, self.y - other.y)
    }
}

impl Sub<Vector> for Point {
    type Output = Point;

    fn sub(self, v: Vector) -> Point {
        Point::new(self.x - v.x, self.y - v.y)
    }
}

impl Transform for Point {
    fn transform<T>(self, t: &T) -> Point
    where
        T: Transformation,
    {
        t.transform_point(self)
    }

    fn transform_mut<T>(&mut self, t: &T)
    where
        T: Transformation,
    {
        *self = self.transform(t);
    }
}