day(22): factor out wrapping to a trait

Signed-off-by: Matej Focko <me@mfocko.xyz>

src/bin/day22.rs

@@ -23,11 +23,31 @@ struct MonkeyMap {
     instructions: Vec<Instruction>,
 }
 
-fn step_with_wrap(position: usize, diff: isize, lower: usize, upper: usize) -> usize {
+trait Wrap {
+    fn next(&self, state: &State<'_>) -> (usize, usize);
+}
+
+struct Wrap2D;
+impl Wrap2D {
+    fn step(position: usize, diff: isize, lower: usize, upper: usize) -> usize {
         let range_size = (upper - lower) as isize;
         (lower as isize + (position as isize + diff - lower as isize + range_size) % range_size)
             as usize
     }
+}
+impl Wrap for Wrap2D {
+    fn next(&self, state: &State<'_>) -> (usize, usize) {
+        let h_bound = state.input.boundaries[&Orientation::Horizontal(state.y)];
+        let v_bound = state.input.boundaries[&Orientation::Vertical(state.x)];
+
+        let (dx, dy) = state.direction;
+
+        (
+            Self::step(state.x, dx, h_bound.0, h_bound.1),
+            Self::step(state.y, dy, v_bound.0, v_bound.1),
+        )
+    }
+}
 
 struct State<'a> {
     input: &'a Input,
@@ -46,29 +66,17 @@ impl<'a> State<'a> {
         }
     }
 
-    fn next(&self) -> (usize, usize) {
+    fn is_blocked(&self, wrapper: &impl Wrap) -> bool {
-        let h_bound = self.input.boundaries[&Orientation::Horizontal(self.y)];
+        let (x, y) = wrapper.next(self);
-        let v_bound = self.input.boundaries[&Orientation::Vertical(self.x)];
-
-        let (dx, dy) = self.direction;
-
-        (
-            step_with_wrap(self.x, dx, h_bound.0, h_bound.1),
-            step_with_wrap(self.y, dy, v_bound.0, v_bound.1),
-        )
-    }
-
-    fn is_blocked(&self) -> bool {
-        let (x, y) = self.next();
         self.input.map[y][x] == '#'
     }
 
-    fn step(&mut self, steps: usize) {
+    fn step(&mut self, wrapper: &impl Wrap, steps: usize) {
         for _ in 0..steps {
-            if self.is_blocked() {
+            if self.is_blocked(wrapper) {
                 return;
             }
-            (self.x, self.y) = self.next();
+            (self.x, self.y) = wrapper.next(self);
         }
     }
 
@@ -155,12 +163,14 @@ impl Solution<Input, Output> for Day22 {
     }
 
     fn part_1(input: &Input) -> Output {
+        let wrapper = Wrap2D;
+
         let final_state = input
             .instructions
             .iter()
             .fold(State::new(input), |mut state, y| {
                 match &y {
-                    Instruction::Move(steps) => state.step(*steps),
+                    Instruction::Move(steps) => state.step(&wrapper, *steps),
                     Instruction::TurnLeft => state.turn_left(),
                     Instruction::TurnRight => state.turn_right(),
                 }