Add automatic falling

src/bin/tetris/main.rs

@@ -8,6 +8,7 @@ fn main() {
             game_type: GameType::Two,
             ..default()
         })
+        .init_state::<Falling>()
         .add_systems(Startup, init_pieces)
         .add_systems(
             Update,
@@ -15,6 +16,8 @@ fn main() {
                 kb_movement.run_if(on_event::<KeyboardInput>),
                 update_position,
                 update_orientation,
+                toggle_falling.run_if(on_event::<KeyboardInput>),
+                falling.run_if(in_state(Falling::On)).run_if(clock_cycle(1.0))
             ),
         )
         .add_systems(Update, draw_grid)
@@ -23,7 +26,7 @@ fn main() {
 
 const SCALE: f32 = 30.0;
 
-#[derive(Component, Default, Debug, Clone, Copy)]
+#[derive(Component, Default, Debug, Clone, Copy, PartialEq)]
 #[require(Transform, Visibility)]
 struct GridPosition {
     x: usize,
@@ -32,23 +35,31 @@ struct GridPosition {
 
 // TODO: Restirct movement to within the grid
 impl GridPosition {
-    fn move_up(&mut self) {
-        if self.y + 1 < 20 {
-            self.y = self.y.saturating_add(1);
+    fn move_up(&self) -> Self {
+        Self {
+            y: if self.y + 1 < 20 { self.y.saturating_add(1) } else { self.y },
+            x: self.x
         }
     }
 
-    fn move_down(&mut self) {
-        self.y = self.y.saturating_sub(1);
+    fn move_down(&mut self) -> Self {
+        Self {
+            y: self.y.saturating_sub(1),
+            x: self.x
+        }
     }
 
-    fn move_left(&mut self) {
-        self.x = self.x.saturating_sub(1);
+    fn move_left(&mut self) -> Self {
+        Self {
+            x: self.x.saturating_sub(1),
+            y: self.y
+        }
     }
 
-    fn move_right(&mut self) {
-        if self.x + 1 < 10 {
-            self.x = self.x.saturating_add(1);
+    fn move_right(&mut self) -> Self {
+        Self {
+            x: if self.x + 1 < 10 { self.x.saturating_add(1) } else { self.x },
+            y: self.y
         }
     }
 }
@@ -131,6 +142,13 @@ impl From<&Orientation> for Quat {
     }
 }
 
+#[derive(States, Clone, Eq, PartialEq, Debug, Hash, Default, Component)]
+enum Falling {
+    #[default]
+    On,
+    Off
+}
+
 fn init_pieces(
     mut commands: Commands,
     mut meshes: ResMut<Assets<Mesh>>,
@@ -191,10 +209,10 @@ fn kb_movement(mut events: EventReader<KeyboardInput>, mut query: Query<(&mut Gr
                 // Check if children would be outside play area...
                 query.iter_mut().for_each(|(mut gp, mut o)| {
                     match key_code {
-                        KeyCode::ArrowUp => gp.move_up(),
-                        KeyCode::ArrowDown => gp.move_down(),
-                        KeyCode::ArrowLeft => gp.move_left(),
-                        KeyCode::ArrowRight => gp.move_right(),
+                        KeyCode::ArrowUp => *gp = gp.move_up(),
+                        KeyCode::ArrowDown => *gp = gp.move_down(),
+                        KeyCode::ArrowLeft => *gp = gp.move_left(),
+                        KeyCode::ArrowRight => *gp = gp.move_right(),
                         KeyCode::Enter => *o = o.next(),
                         _ => ()
                     }
@@ -214,3 +232,44 @@ fn draw_grid(mut gizmos: Gizmos) {
         )
         .outer_edges();
 }
+
+fn toggle_falling(
+    mut events: EventReader<KeyboardInput>,
+    curr: Res<State<Falling>>,
+    mut next: ResMut<NextState<Falling>>,
+) {
+    events.read().for_each(|KeyboardInput { state, key_code, .. }| {
+        if let ButtonState::Pressed = state && *key_code == KeyCode::Space {
+            next.set(match curr.get() {
+                Falling::On => Falling::Off,
+                Falling::Off => Falling::On,
+            });
+        }
+    })
+}
+
+fn falling(
+    mut query: Query<&mut GridPosition>
+) {
+    query.iter_mut ().for_each(|mut gp| {
+        let next = gp.move_down();
+        if next != *gp {
+            *gp = next;
+        } else {
+            // Remove the falling component from this entity
+        }
+    });
+}
+
+// Run condition that returns `true` every `n` seconds
+fn clock_cycle(n: f32) -> impl FnMut (Res<Time>, Local<f32>) -> bool {
+    move |t: Res<Time>, mut buf: Local<f32>| -> bool {
+        *buf += t.delta_secs();
+        if *buf > n {
+            *buf = 0.0;
+            true
+        } else {
+            false
+        }
+    }
+}