Add rotation functions to DirectedPos

Author: intrepidcoder

src/grid/directed_pos.rs

@@ -6,19 +6,6 @@ pub struct DirectedPos {
     dir: Direction,
 }
 
-#[repr(u8)]
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Direction {
-    North = 0,
-    NorthEast = 1,
-    East = 2,
-    SouthEast = 3,
-    South = 4,
-    SouthWest = 5,
-    West = 6,
-    NorthWest = 7,
-}
-
 impl DirectedPos {
     pub fn new(pos: Pos, dir: Direction) -> Self {
         Self { pos, dir }
@@ -48,6 +35,46 @@ impl DirectedPos {
         self.pos.col()
     }
 
+    /// Rotate direction by 90 degrees clockwise
+    pub fn cw(self) -> Self {
+        Self {
+            pos: self.pos,
+            dir: self.dir.cw(),
+        }
+    }
+
+    /// Rotate direction by 90 degrees counter-clockwise
+    pub fn ccw(self) -> Self {
+        Self {
+            pos: self.pos,
+            dir: self.dir.ccw(),
+        }
+    }
+
+    /// Rotate direction by 45 degrees clockwise
+    pub fn cw45(self) -> Self {
+        Self {
+            pos: self.pos,
+            dir: self.dir.cw45(),
+        }
+    }
+
+    /// Rotate direction by 45 degrees counter-clockwise
+    pub fn ccw45(self) -> Self {
+        Self {
+            pos: self.pos,
+            dir: self.dir.ccw45(),
+        }
+    }
+
+    /// Rotate direction by 180 degrees
+    pub fn reverse(self) -> Self {
+        Self {
+            pos: self.pos,
+            dir: self.dir.reverse(),
+        }
+    }
+
     pub fn north(&self, grid: &Grid) -> Option<DirectedPos> {
         self.pos.north(grid).map(|p| Self::new(p, self.dir))
     }
@@ -81,9 +108,66 @@ impl DirectedPos {
     }
 }
 
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Direction {
+    North = 0,
+    NorthEast = 1,
+    East = 2,
+    SouthEast = 3,
+    South = 4,
+    SouthWest = 5,
+    West = 6,
+    NorthWest = 7,
+}
+
+impl Direction {
+    /// Rotate by 90 degrees clockwise
+    pub fn cw(self) -> Self {
+        Self::cast((self as u8) + 2)
+    }
+
+    /// Rotate by 90 degrees counter-clockwise
+    pub fn ccw(self) -> Self {
+        Self::cast((self as u8) + 6)
+    }
+
+    /// Rotate by 45 degrees clockwise
+    pub fn cw45(self) -> Self {
+        Self::cast((self as u8) + 1)
+    }
+
+    /// Rotate by 45 degrees counter-clockwise
+    pub fn ccw45(self) -> Self {
+        Self::cast((self as u8) + 7)
+    }
+
+    /// Rotate by 180 degrees
+    pub fn reverse(self) -> Self {
+        Self::cast((self as u8) + 4)
+    }
+
+    fn cast(val: u8) -> Self {
+        let mask = 7;
+
+        match val & mask {
+            0 => Self::North,
+            1 => Self::NorthEast,
+            2 => Self::East,
+            3 => Self::SouthEast,
+            4 => Self::South,
+            5 => Self::SouthWest,
+            6 => Self::West,
+            7 => Self::NorthWest,
+            _ => unreachable!(),
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
+    use std::iter;
 
     #[test]
     fn test_pos() {
@@ -97,4 +181,17 @@ mod test {
             DirectedPos::new(grid.pos(1), Direction::North)
         );
     }
+
+    #[test]
+    fn test_rotations() {
+        let grid = Grid::new("012\n345\n678".to_string());
+        let first_pos = DirectedPos::new(grid.pos(4), Direction::North);
+
+        for pos in iter::successors(Some(first_pos), |p| Some(p.cw45())).take(8) {
+            assert_eq!(pos, pos.cw().ccw());
+            assert_eq!(pos, pos.cw().ccw45().ccw45());
+            assert_eq!(pos, pos.ccw().cw45().cw45());
+            assert_eq!(pos.cw().cw(), pos.reverse());
+        }
+    }
 }