prototypes/life: refactor: message based cell lifecycle

engine/src/lib.rs

@@ -1 +1,4 @@
-pub use bevy::{color::palettes::basic::*, input::common_conditions::*, prelude::*, platform::collections::HashSet};
+pub use bevy::{
+    color::palettes::basic::*, input::common_conditions::*, platform::collections::HashSet,
+    prelude::*,
+};

prototypes/src/bin/life.rs

@@ -24,6 +24,7 @@ fn main() {
         }))
         .init_resource::<Coordinates>()
         .init_state::<SimulationState>()
+        .add_message::<Lifecycle>()
         .add_systems(Startup, setup)
         .add_systems(
             Update,
@@ -42,6 +43,7 @@ fn main() {
             Update,
             simulation_step.run_if(input_just_pressed(KeyCode::Space)),
         )
+        .add_systems(Update, cell_lifecycle.run_if(on_message::<Lifecycle>))
         .add_observer(on_add_ui_button)
         .add_observer(on_add_coordinates)
         .run();
@@ -71,7 +73,6 @@ impl UiButton {
             Self::ZoomIn => "zoomIn.png",
         }
     }
-
 }
 
 fn on_add_ui_button(
@@ -118,13 +119,16 @@ fn setup(mut commands: Commands) {
     ));
 
     commands
-        .spawn((Node {
+        .spawn((
+            Node {
                 top: Val::Px(0.0),
                 left: Val::Px(0.0),
                 height: Val::Px(40.0),
                 width: Val::Percent(100.0),
                 ..default()
-        }, Transform::default()))
+            },
+            Transform::default(),
+        ))
         .with_children(|parent| {
             parent.spawn(UiButton::Power);
             parent.spawn(UiButton::Pause);
@@ -192,18 +196,14 @@ impl Coordinates {
         .into_iter()
     }
 
-    fn is_neighbor_of(&self, other: &Coordinates) -> bool {
-        let (a1, b1) = (self.x, self.y);
-        let (a2, b2) = (other.x, other.y);
-        (a1 == a2 + 1 || a1 == a2 - 1) && (b1 == b2 + 1 || b1 == b2 - 1)
-    }
-
     fn as_translation(&self) -> Vec3 {
         (Vec2::new(self.x as f32, self.y as f32) * SCALE).extend(0.0)
     }
 }
 
-fn on_add_coordinates(trigger: On<Add, Coordinates>, coordinates: Query<&Coordinates>,
+fn on_add_coordinates(
+    trigger: On<Add, Coordinates>,
+    coordinates: Query<&Coordinates>,
     cells: Query<&Cell>,
     mut commands: Commands,
     mut meshes: ResMut<Assets<Mesh>>,
@@ -307,24 +307,34 @@ enum SimulationState {
 /// 4. Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.
 ///
 /// TODO: There is a lot of optimizations to be had here
-fn simulation_step(q: Query<(Entity, &Coordinates), With<Cell>>, mut commands: Commands) {
-    fn is_cell_alive(coordinates: &Coordinates, query: &Query<(Entity, &Coordinates), With<Cell>>) -> bool {
-        query
-            .iter()
-            .any(|(_e, c)| *c == *coordinates)
+fn simulation_step(
+    q: Query<(Entity, &Coordinates), With<Cell>>,
+    mut writer: MessageWriter<Lifecycle>,
+) {
+    fn is_cell_alive(
+        coordinates: &Coordinates,
+        query: &Query<(Entity, &Coordinates), With<Cell>>,
+    ) -> bool {
+        query.iter().any(|(_e, c)| *c == *coordinates)
     }
 
-    fn living_neighbors(c: &Coordinates, query: &Query<(Entity, &Coordinates), With<Cell>>) -> usize {
+    fn living_neighbors(
+        c: &Coordinates,
+        query: &Query<(Entity, &Coordinates), With<Cell>>,
+    ) -> usize {
         c.neighbors()
             .filter(|neighbor| {
-                query.iter().any(
-                    |(_e, coordinates)| { *neighbor == *coordinates },
-                )
+                query
+                    .iter()
+                    .any(|(_e, coordinates)| *neighbor == *coordinates)
             })
             .count()
     }
 
-    fn cell_entity(coordinates: &Coordinates, query: Query<(Entity, &Coordinates), With<Cell>>) -> Option<Entity> {
+    fn cell_entity(
+        coordinates: &Coordinates,
+        query: Query<(Entity, &Coordinates), With<Cell>>,
+    ) -> Option<Entity> {
         query
             .iter()
             .find_map(|(e, c)| (*c == *coordinates).then_some(e))
@@ -353,18 +363,14 @@ fn simulation_step(q: Query<(Entity, &Coordinates), With<Cell>>, mut commands: C
 
         match num_living_neighbors {
             ..2 | 4.. => {
-                if let Some(e) = cell_entity(c, q) {
-                    debug!("killing {:?}", c);
-                    commands.entity(e).despawn();
-                } else {
-                    debug!("failed to kill {:?}", c);
+                if is_living {
+                    writer.write(Lifecycle::Dead(cell_entity(c, q).unwrap()));
                 }
             }
             2 => debug!("continue"),
             3 => {
                 if !is_living {
-                    debug!("creating {:?}", c);
-                    commands.spawn((c.clone(), Cell));
+                    writer.write(Lifecycle::Alive(c.clone()));
                 } else {
                     debug!("continue")
                 }
@@ -382,3 +388,27 @@ fn responsive_button_out(trigger: On<Pointer<Out>>, mut bg: Query<&mut Backgroun
     let mut background_color = bg.get_mut(trigger.entity).unwrap();
     background_color.0 = GRAY.into();
 }
+
+/// Bring a cell to life, or kill it
+#[derive(Message)]
+enum Lifecycle {
+    Alive(Coordinates),
+    Dead(Entity),
+}
+
+fn cell_lifecycle(
+    mut reader: MessageReader<Lifecycle>,
+    mut commands: Commands,
+) {
+    reader.read().for_each(|msg| match msg {
+        Lifecycle::Alive(c) => {
+            debug!("creating {:?}", c);
+            // TODO: Safeguard: ensure no other cell there?
+            commands.spawn((c.clone(), Cell));
+        }
+        Lifecycle::Dead(e) => {
+            // TODO: Maybe include the entity instead of the coordinates for Dead
+            commands.entity(*e).despawn();
+        }
+    })
+}