Sometimes we get a bug, but not consistently...

src/bin/flappy/main.rs

@@ -84,7 +84,7 @@ fn main() {
                 update_tooltip.run_if(in_state(DebuggingState::On)),
                 // TODO: Add run_if to this system
                 update_batch_position.run_if(any_component_changed::<Batch>),
-                hitbox_collision_handler,
+                move_batches.run_if(on_event::<CollisionStarted>),
                 manage_score.run_if(on_event::<CollisionStarted>.or(on_event::<CollisionEnded>)),
             ),
         )
@@ -810,14 +810,20 @@ fn manage_score(
     }
 }
 
-/// When the player moves forward while alive
-/// spawn more batches and despawn old batches
-fn hitbox_collision_handler(
+/// WARNING: This method is somewhat janky
+///
+/// We first figure out which collided entity was a hitbox
+///     and bial out early if neither is a hitbox
+/// Then we find the batch ID for the hitbox that was hit
+/// Next we figure out the old -> new batch IDs based on offsets from the current batch
+///     skipping the 0th batch intentionally as that is a special case
+/// Finally we iterate over all entities with the old batch ID and upsert the new batch ID
+///     This includes root batch entities as well as pipes and hitboxes
+fn move_batches(
     mut start: EventReader<CollisionStarted>,
     bird: Query<Entity, With<Bird>>,
     hitboxes: Query<Entity, With<Hitbox>>,
     batches: Query<(Entity, &Batch)>,
-    parents: Query<Entity, Without<ChildOf>>,
     state: Res<State<PlayerState>>,
     mut commands: Commands,
 ) {
@@ -836,24 +842,22 @@ fn hitbox_collision_handler(
 
         let (_, Batch(curr)) = batches.get(target).unwrap();
 
-        debug!("[batches] Current: {curr}");
-        if *curr > 0 {
-            let (old_batch, new_batch) = match state.get() {
-                PlayerState::Alive => (curr.saturating_sub(2), curr.saturating_add(2)),
-                PlayerState::Rewind => (curr.saturating_add(2), curr.saturating_sub(2)),
-                _ => (*curr, *curr),
-            };
-
-            if old_batch > 0 && new_batch != 0 {
-                batches
-                    .iter()
-                    // Filter to just entities with this batch ID
-                    .filter_map(|(e, Batch(id))| (*id == old_batch).then_some(e))
-                    .for_each(|old| {
-                        info!("Moving batch {old_batch}({old}) -> {new_batch}");
-                        commands.entity(old).insert(Batch(new_batch));
-                    })
-            }
+        info!("[batches] Current: {curr}");
+        let (old_batch, new_batch) = match state.get() {
+            PlayerState::Alive => (curr.saturating_sub(2), curr.saturating_add(2)),
+            PlayerState::Rewind => (curr.saturating_add(2), curr.saturating_sub(2)),
+            _ => (*curr, *curr),
+        };
+
+        if old_batch > 0 && new_batch != 0 {
+            batches
+                .iter()
+                // Filter to just entities with this batch ID
+                .filter_map(|(e, Batch(id))| (*id == old_batch).then_some(e))
+                .for_each(|old| {
+                    info!("Moving batch {old_batch}({old}) -> {new_batch}");
+                    commands.entity(old).insert(Batch(new_batch));
+                })
         }
     });
 }