refactor: simplify/improve is_adjacent, add tests & docs

src/helper.rs

@@ -1,15 +1,110 @@
+/// Checks if two grid positions are adjacent to each other
+///
+/// # Arguments
+/// * `a` - First position as (x, y) coordinates
+/// * `b` - Second position as (x, y) coordinates  
+/// * `diagonal` - Whether to consider diagonal adjacency (true) or only orthogonal (false)
+///
+/// # Returns
+/// * `true` if positions are adjacent according to the diagonal parameter
+/// * `false` otherwise
 pub fn is_adjacent(a: (u32, u32), b: (u32, u32), diagonal: bool) -> bool {
     let (ax, ay) = a;
     let (bx, by) = b;
+
+    // Calculate absolute differences between coordinates
+    let dx = if ax > bx { ax - bx } else { bx - ax };
+    let dy = if ay > by { ay - by } else { by - ay };
+
     if diagonal {
-        (ax == bx && (ay == by + 1 || ay == by - 1))
-            || (ay == by && (ax == bx + 1 || ax == bx - 1))
-            || (ax == bx + 1 && ay == by + 1)
-            || (ax == bx + 1 && ay == by - 1)
-            || (ax == bx - 1 && ay == by + 1)
-            || (ax == bx - 1 && ay == by - 1)
+        // For diagonal adjacency: both differences must be ≤ 1 and at least one > 0
+        dx <= 1 && dy <= 1 && (dx + dy) > 0
     } else {
-        (ax == bx && (ay == by + 1 || ay == by - 1))
-            || (ay == by && (ax == bx + 1 || ax == bx - 1))
+        // For orthogonal adjacency: exactly one difference must be 1, the other 0
+        (dx == 1 && dy == 0) || (dx == 0 && dy == 1)
     }
-}
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_orthogonal_adjacency() {
+        // Test orthogonal adjacency (diagonal = false)
+
+        // Same position should not be adjacent
+        assert!(!is_adjacent((0, 0), (0, 0), false));
+
+        // Adjacent positions should be true
+        assert!(is_adjacent((0, 0), (1, 0), false)); // Right
+        assert!(is_adjacent((0, 0), (0, 1), false)); // Down
+        assert!(is_adjacent((1, 1), (0, 1), false)); // Left
+        assert!(is_adjacent((1, 1), (1, 0), false)); // Up
+
+        // Diagonal positions should be false
+        assert!(!is_adjacent((0, 0), (1, 1), false));
+        assert!(!is_adjacent((0, 1), (1, 0), false));
+
+        // Positions more than 1 step away should be false
+        assert!(!is_adjacent((0, 0), (2, 0), false));
+        assert!(!is_adjacent((0, 0), (0, 2), false));
+        assert!(!is_adjacent((0, 0), (2, 2), false));
+    }
+
+    #[test]
+    fn test_diagonal_adjacency() {
+        // Test diagonal adjacency (diagonal = true)
+
+        // Same position should not be adjacent
+        assert!(!is_adjacent((0, 0), (0, 0), true));
+
+        // Orthogonal adjacent positions should be true
+        assert!(is_adjacent((0, 0), (1, 0), true)); // Right
+        assert!(is_adjacent((0, 0), (0, 1), true)); // Down
+        assert!(is_adjacent((1, 1), (0, 1), true)); // Left
+        assert!(is_adjacent((1, 1), (1, 0), true)); // Up
+
+        // Diagonal adjacent positions should be true
+        assert!(is_adjacent((0, 0), (1, 1), true)); // Down-right
+        assert!(is_adjacent((1, 0), (0, 1), true)); // Down-left
+        assert!(is_adjacent((0, 1), (1, 0), true)); // Up-right
+        assert!(is_adjacent((1, 1), (0, 0), true)); // Up-left
+
+        // Positions more than 1 step away should be false
+        assert!(!is_adjacent((0, 0), (2, 0), true));
+        assert!(!is_adjacent((0, 0), (0, 2), true));
+        assert!(!is_adjacent((0, 0), (2, 2), true));
+        assert!(!is_adjacent((0, 0), (1, 2), true));
+    }
+
+    #[test]
+    fn test_edge_cases() {
+        // Test with larger coordinates
+        assert!(is_adjacent((100, 100), (101, 100), false));
+        assert!(is_adjacent((100, 100), (100, 101), false));
+        assert!(!is_adjacent((100, 100), (102, 100), false));
+
+        assert!(is_adjacent((100, 100), (101, 101), true));
+        assert!(!is_adjacent((100, 100), (102, 102), true));
+
+        // Test with zero coordinates
+        assert!(is_adjacent((0, 0), (1, 0), false));
+        assert!(is_adjacent((0, 0), (0, 1), false));
+        assert!(is_adjacent((0, 0), (1, 1), true));
+    }
+
+    #[test]
+    fn test_commutative_property() {
+        // The function should work the same regardless of parameter order
+        assert_eq!(
+            is_adjacent((1, 2), (2, 2), false),
+            is_adjacent((2, 2), (1, 2), false)
+        );
+
+        assert_eq!(
+            is_adjacent((1, 2), (2, 3), true),
+            is_adjacent((2, 3), (1, 2), true)
+        );
+    }
+}

src/main.rs

@@ -12,6 +12,7 @@ mod constants;
 mod direction;
 mod entity;
 mod game;
+mod helper;
 mod map;
 mod modulation;
 mod pacman;