rust-java-functional-programming/src/geometry.rs

use std::ops::Add;

#[derive(Debug, Copy, Clone)]
pub struct Point {
    x: u32,
    y: u32,
}

#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct Rectangle {
    top_left: Point,
    width: u32,
    height: u32,
}

impl Point {
    pub fn new(x: u32, y: u32) -> Self {
        Self { x, y }
    }

    pub fn origin() -> Self {
        Self { x: 0, y: 0 }
    }

    pub fn with_x(&self, x: u32) -> Self {
        Self { x, y: self.y }
    }

    pub fn with_y(&self, y: u32) -> Self {
        Self { x: self.x, y }
    }

    pub fn x(&self) -> u32 {
        self.x
    }

    pub fn y(&self) -> u32 {
        self.y
    }

    pub fn left_of(&self, other: &Self) -> bool {
        self.x < other.x
    }

    pub fn right_of(&self, other: &Self) -> bool {
        self.x > other.x
    }

    pub fn above(&self, other: &Self) -> bool {
        self.y < other.y
    }

    pub fn below(&self, other: &Self) -> bool {
        self.y > other.y
    }
}

impl Add for Point {
    type Output = Point;

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

// These can be derived too, but implement them for demonstration.
impl PartialEq for Point {
    fn eq(&self, other: &Self) -> bool {
        self.x == other.x && self.y == other.y
    }
}

// Marker trait to indicate reflexivity of equality (not just transitivity & symmetry)
impl Eq for Point {}

impl Rectangle {
    fn from_corner_width_height(top_left: Point, width: u32, height: u32) -> Rectangle {
        Rectangle {
            top_left,
            width,
            height,
        }
    }

    fn from_corners(corner_a: Point, corner_b: Point) -> Rectangle {
        let left = corner_a.x().min(corner_b.x());
        let top = corner_a.y().min(corner_b.y());

        let width = (corner_a.x() as i64 - corner_b.x() as i64).abs() as u32;
        let height = (corner_a.y() as i64 - corner_b.y() as i64).abs() as u32;

        Rectangle {
            top_left: Point::new(left, top),
            width,
            height,
        }
    }

    fn at_origin_with_size(width: u32, height: u32) -> Rectangle {
        Rectangle {
            top_left: Point::origin(),
            width,
            height,
        }
    }

    fn width(&self) -> u32 {
        self.width
    }

    fn height(&self) -> u32 {
        self.height
    }

    fn with_width(&self, width: u32) -> Rectangle {
        Rectangle {
            top_left: self.top_left,
            width,
            height: self.height,
        }
    }

    fn with_height(&self, height: u32) -> Rectangle {
        Rectangle {
            top_left: self.top_left,
            width: self.width,
            height,
        }
    }

    fn top_left(&self) -> Point {
        self.top_left
    }

    fn top_right(&self) -> Point {
        Point::new(self.top_left.x() + self.width, self.top_left.y())
    }

    fn bottom_right(&self) -> Point {
        Point::new(
            self.top_left.x() + self.width,
            self.top_left.y() + self.height,
        )
    }

    fn bottom_left(&self) -> Point {
        Point::new(self.top_left.x(), self.top_left.y() + self.height)
    }

    fn area(&self) -> u32 {
        self.width * self.height
    }

    fn intersects(&self, other: &Rectangle) -> bool {
        !(self.top_left().right_of(&other.top_right())
            || self.top_left().below(&other.bottom_left())
            || self.top_right().left_of(&other.top_left())
            || self.bottom_left().above(&other.top_left()))
    }
}

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

    #[test]
    fn test_point_get_x() {
        assert_eq!(Point::new(42, 52).x(), 42);
    }

    #[test]
    fn test_point_get_y() {
        assert_eq!(Point::new(42, 52).y(), 52);
    }

    #[test]
    fn test_point_set_x() {
        assert_eq!(Point::new(42, 52).with_x(12), Point::new(12, 52));
    }

    #[test]
    fn test_point_set_y() {
        assert_eq!(Point::new(42, 52).with_y(12), Point::new(42, 12));
    }

    #[test]
    fn test_point_left_of() {
        assert!(Point::new(10, 20).left_of(&Point::new(20, 20)));
        assert!(!Point::new(10, 11).left_of(&Point::new(10, 11)));
        assert!(!Point::new(10, 11).left_of(&Point::new(8, 11)));
    }

    #[test]
    fn test_point_right_of() {
        assert!(Point::new(10, 20).right_of(&Point::new(0, 20)));
        assert!(!Point::new(10, 11).right_of(&Point::new(10, 11)));
        assert!(!Point::new(10, 11).right_of(&Point::new(12, 11)));
    }

    #[test]
    fn test_point_above() {
        assert!(Point::new(1, 1).above(&Point::new(1, 2)));
        assert!(!Point::new(10, 11).above(&Point::origin()));
    }

    #[test]
    fn test_point_below() {
        assert!(Point::new(1, 1).below(&Point::new(1, 0)));
        assert!(!Point::new(10, 11).below(&Point::new(12, 11)));
    }

    #[test]
    fn test_point_add() {
        assert_eq!(Point::new(1, 1) + Point::new(10, 10), Point::new(11, 11));
        assert_eq!(
            Point::new(10, 0) + Point::new(0, 10),
            Point::new(0, 10) + Point::new(10, 0)
        );
    }
}