use std::ops::{Add, AddAssign, Mul};

pub type Nanoseconds = u64;

#[macro_export]
macro_rules! point {
    ( $x:expr, $y:expr ) => {
        Point2D { x: $x, y: $y }
    };
}

#[derive(Debug, Default, Copy, Clone, PartialEq)]
pub struct Point2D<T> {
    pub x: T,
    pub y: T,
}

impl Point2D<f64> {
    pub fn length(self) -> f64 {
        ((self.x * self.x) + (self.y * self.y)).sqrt()
    }
}

impl<T: Add<Output = T>> Add for Point2D<T> {
    type Output = Point2D<T>;

    fn add(self, rhs: Point2D<T>) -> Self::Output {
        Point2D {
            x: self.x + rhs.x,
            y: self.y + rhs.y,
        }
    }
}

impl<T: AddAssign> AddAssign for Point2D<T> {
    fn add_assign(&mut self, rhs: Point2D<T>) {
        self.x += rhs.x;
        self.y += rhs.y;
    }
}

impl<T> From<(T, T)> for Point2D<T> {
    fn from(item: (T, T)) -> Self {
        Point2D {
            x: item.0,
            y: item.1,
        }
    }
}

#[macro_export]
macro_rules! rect {
    ( $x:expr, $y:expr ) => {
        Rect { x: $x, y: $y }
    };
}

#[derive(Default)]
pub struct Rect<T> {
    pub width: T,
    pub height: T,
}

impl<T: Mul<Output = T> + Copy> Rect<T> {
    #[allow(dead_code)]
    pub fn area(&self) -> T {
        self.width * self.height
    }
}

impl<T> From<(T, T)> for Rect<T> {
    fn from(item: (T, T)) -> Self {
        Rect {
            width: item.0,
            height: item.1,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn immutable_copy_of_point() {
        let a = point!(0, 0);
        let mut b = a; // Copy
        assert_eq!(a, b); // PartialEq
        b.x = 1;
        assert_ne!(a, b); // PartialEq
    }

    #[test]
    fn add_points() {
        let mut a = point!(1, 0);
        assert_eq!(a + point!(2, 2), point!(3, 2)); // Add
        a += point!(2, 2); // AddAssign
        assert_eq!(a, point!(3, 2));
    }

    #[test]
    fn area_for_rect_of_multipliable_type() {
        let r: Rect<_> = (30, 20).into(); // the Into trait uses the From trait
        assert_eq!(r.area(), 30 * 20);
        // let a = Rect::from(("a".to_string(), "b".to_string())).area(); // this doesn't work, because area() is not implemented for String
    }
}