pushers

kiln-core/src/board.rs

@@ -254,6 +254,33 @@ impl Board {
         }
     }
 
+    /// Advances a [`Archetype::Pusher`] cell at `(x, y)` one step in its facing
+    /// direction. Reads the direction from the cell itself.
+    ///
+    /// - If the target is passable: slides the pusher in.
+    /// - If the target has a pushable chain: pushes it first, then slides in.
+    /// - If blocked or out of bounds: no-op, returns `false`.
+    pub(crate) fn advance_pusher(&mut self, x: usize, y: usize) -> bool {
+        let Archetype::Pusher(dir) = self.get(x, y).1 else { return false; };
+        let (dx, dy): (i32, i32) = dir.into();
+        let tx = x as i32 + dx;
+        let ty = y as i32 + dy;
+        if !self.in_bounds((tx, ty)) {
+            return false;
+        }
+        let (tx, ty) = (tx as usize, ty as usize);
+        if self.is_passable(tx, ty) {
+            self.shift_solid(x, y, dx, dy);
+            true
+        } else if self.can_push(tx, ty, dir) {
+            self.push(tx, ty, dir); // clear the chain first
+            self.shift_solid(x, y, dx, dy);
+            true
+        } else {
+            false
+        }
+    }
+
     /// Moves the single solid occupant of `(x, y)` one step by `(dx, dy)`.
     ///
     /// A solid object is relocated; otherwise the grid archetype (a crate) is