common/rust: add manhattan distance methods to Line

common/rust/src/vec2.rs

@@ -28,6 +28,48 @@ impl Vec2 {
     pub fn len(self) -> f64 {
         (f64::from(self.x).powi(2) + f64::from(self.y).powi(2)).sqrt()
     }
+
+    #[must_use]
+    pub fn manhattan_dist(self, other: Vec2) -> usize {
+        let Vec2 { x, y } = (other - self).map(i32::abs);
+        let x = usize::try_from(x).unwrap();
+        let y = usize::try_from(y).unwrap();
+        x + y
+    }
+
+    #[must_use]
+    pub fn on_x_with_manhattan_dist(self, x: i32, dist: usize) -> Option<(Vec2, Vec2)> {
+        let dx = usize::try_from((x - self.x).abs()).ok()?;
+
+        let dy = dist.checked_sub(dx)?;
+        let dy = i32::try_from(dy).ok()?;
+
+        let p1 = Vec2::new(x, self.y - dy);
+        let p2 = Vec2::new(x, self.y + dy);
+
+        debug_assert!(p1 <= p2);
+        debug_assert_eq!(self.manhattan_dist(p1), dist);
+        debug_assert_eq!(self.manhattan_dist(p2), dist);
+
+        Some((p1, p2))
+    }
+
+    #[must_use]
+    pub fn on_y_with_manhattan_dist(self, y: i32, dist: usize) -> Option<(Vec2, Vec2)> {
+        let dy = usize::try_from((y - self.y).abs()).ok()?;
+
+        let dx = dist.checked_sub(dy)?;
+        let dx = i32::try_from(dx).ok()?;
+
+        let p1 = Vec2::new(self.x - dx, y);
+        let p2 = Vec2::new(self.x + dx, y);
+
+        debug_assert!(p1 <= p2);
+        debug_assert_eq!(self.manhattan_dist(p1), dist);
+        debug_assert_eq!(self.manhattan_dist(p2), dist);
+
+        Some((p1, p2))
+    }
 }
 
 impl fmt::Display for Vec2 {