Tail following

Author: marcusbuffett

src/main.rs

@@ -102,6 +102,40 @@ fn spawn_segment(mut commands: Commands, position: Position) -> Entity {
         .id()
 }
 
+fn snake_movement(
+    segments: ResMut<SnakeSegments>,
+    mut heads: Query<(Entity, &SnakeHead)>,
+    mut positions: Query<&mut Position>,
+) {
+    if let Some((head_entity, head)) = heads.iter_mut().next() {
+        let segment_positions = segments
+            .iter()
+            .map(|e| *positions.get_mut(*e).unwrap())
+            .collect::<Vec<Position>>();
+        let mut head_pos = positions.get_mut(head_entity).unwrap();
+        match &head.direction {
+            Direction::Left => {
+                head_pos.x -= 1;
+            }
+            Direction::Right => {
+                head_pos.x += 1;
+            }
+            Direction::Up => {
+                head_pos.y += 1;
+            }
+            Direction::Down => {
+                head_pos.y -= 1;
+            }
+        };
+        segment_positions
+            .iter()
+            .zip(segments.iter().skip(1))
+            .for_each(|(pos, segment)| {
+                *positions.get_mut(*segment).unwrap() = *pos;
+            });
+    }
+}
+
 fn snake_movement_input(keyboard_input: Res<Input<KeyCode>>, mut heads: Query<&mut SnakeHead>) {
     if let Some(mut head) = heads.iter_mut().next() {
         let dir: Direction = if keyboard_input.pressed(KeyCode::Left) {
@@ -121,25 +155,6 @@ fn snake_movement_input(keyboard_input: Res<Input<KeyCode>>, mut heads: Query<&m
     }
 }
 
-fn snake_movement(mut heads: Query<(&mut Position, &SnakeHead)>) {
-    if let Some((mut head_pos, head)) = heads.iter_mut().next() {
-        match &head.direction {
-            Direction::Left => {
-                head_pos.x -= 1;
-            }
-            Direction::Right => {
-                head_pos.x += 1;
-            }
-            Direction::Up => {
-                head_pos.y += 1;
-            }
-            Direction::Down => {
-                head_pos.y -= 1;
-            }
-        };
-    }
-}
-
 fn size_scaling(windows: Res<Windows>, mut q: Query<(&Size, &mut Transform)>) {
     let window = windows.get_primary().unwrap();
     for (sprite_size, mut transform) in q.iter_mut() {