Fix direction and game over systems

src/fruit.rs

@@ -20,7 +20,7 @@ impl Plugin for FruitPlugin {
             )
             .add_system(debug_eaten_event_system)
             .add_system(despawn_fruit_system)
-            .add_system(spawn_fruit_system.run_on_event::<EatenEvent>());
+            .add_system(spawn_fruit_system.run_if(eaten_event_sent));
     }
 }
 
@@ -29,6 +29,10 @@ pub struct EatenEvent(Option<Entity>);
 #[derive(Component)]
 pub struct Fruit;
 
+fn eaten_event_sent(mut eaten_event_reader: EventReader<EatenEvent>) -> bool {
+    eaten_event_reader.iter().count() != 0
+}
+
 fn spawn_fruit_system(mut commands: Commands) {
     // TODO: not spawn in snake
     let mut rng = rand::thread_rng();

src/snake.rs

@@ -3,12 +3,10 @@ use bevy::prelude::*;
 use itertools::Itertools;
 use iyes_loopless::prelude::*;
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-#[derive(StageLabel)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, StageLabel)]
 struct MovementStage;
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-#[derive(SystemLabel)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, SystemLabel)]
 pub enum SystemLabel {
     SegmentMovement,
 }
@@ -37,11 +35,16 @@ impl Plugin for SnakePlugin {
                     .run_if(tick_triggered)
                     .after(SystemLabel::SegmentMovement),
             )
+            .add_system(
+                update_direction_system
+                    .run_in_state(AppState::InGame)
+                    .run_if(tick_triggered),
+            )
             .add_system(
                 game_over_system
                     .run_in_state(AppState::InGame)
-                    .run_if(about_to_lose)
-                    .run_if(tick_triggered),
+                    .run_if(tick_triggered)
+                    .run_if(about_to_lose),
             )
             .add_system(add_direction_system.run_in_state(AppState::Begin))
             .add_system(change_direction_system.run_in_state(AppState::InGame))
@@ -66,6 +69,9 @@ enum Direction {
     Right,
 }
 
+#[derive(Component)]
+struct DirectionBuffer(Option<Direction>);
+
 #[derive(Component)]
 struct Snake;
 
@@ -116,7 +122,8 @@ fn setup_snake_system(mut commands: Commands) {
     commands
         .entity(snake_head)
         .insert(Name::new("SnakeHead"))
-        .insert(SnakeHead);
+        .insert(SnakeHead)
+        .insert(DirectionBuffer(None));
 
     commands
         .spawn()
@@ -160,22 +167,33 @@ fn add_tail_system(
     }
 }
 
+fn update_direction_system(
+    mut query: Query<(&mut Direction, &mut DirectionBuffer), With<SnakeHead>>,
+) {
+    for (mut direction, mut direction_buffer) in query.iter_mut() {
+        if let Some(new_direction) = direction_buffer.0 {
+            *direction = new_direction;
+            direction_buffer.0 = None;
+        }
+    }
+}
+
 fn change_direction_system(
     keypress: Res<Input<KeyCode>>,
-    mut query: Query<&mut Direction, With<SnakeHead>>,
+    mut query: Query<(&Direction, &mut DirectionBuffer), With<SnakeHead>>,
 ) {
     if let Some(new_direction) = Direction::from_keypress(keypress) {
-        let mut direction = query.single_mut();
+        let (direction, mut direction_buffer) = query.single_mut();
 
-        match (direction.as_ref(), &new_direction) {
-            (Direction::Up, Direction::Down)
-            | (Direction::Down, Direction::Up)
-            | (Direction::Left, Direction::Right)
-            | (Direction::Right, Direction::Left) => return,
-            _ => {}
+        if let (Direction::Up, Direction::Down)
+        | (Direction::Down, Direction::Up)
+        | (Direction::Left, Direction::Right)
+        | (Direction::Right, Direction::Left) = (direction, &new_direction)
+        {
+            return;
         }
 
-        *direction = new_direction;
+        direction_buffer.0 = Some(new_direction);
     }
 }
 

src/tick.rs

@@ -5,8 +5,7 @@ use std::time::Duration;
 
 const TICK_PERIOD: u64 = 125;
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-#[derive(StageLabel)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, StageLabel)]
 struct FixedTimeStage;
 
 pub struct TickPlugin;
@@ -16,14 +15,12 @@ impl Plugin for TickPlugin {
         let mut fixed_time_system_stage = SystemStage::parallel();
         fixed_time_system_stage.add_system(tick_event_system.run_in_state(AppState::InGame));
 
-        app.add_event::<TickEvent>()
-            .add_stage_before(
-                CoreStage::Update,
-                FixedTimeStage,
-                FixedTimestepStage::new(Duration::from_millis(TICK_PERIOD))
-                    .with_stage(fixed_time_system_stage),
-            );
-            // .add_system(print_tick_system);
+        app.add_event::<TickEvent>().add_stage_before(
+            CoreStage::Update,
+            FixedTimeStage,
+            FixedTimestepStage::new(Duration::from_millis(TICK_PERIOD))
+                .with_stage(fixed_time_system_stage),
+        );
     }
 }
 
@@ -36,9 +33,3 @@ fn tick_event_system(mut event_writer: EventWriter<TickEvent>) {
 pub fn tick_triggered(mut event_reader: EventReader<TickEvent>) -> bool {
     event_reader.iter().count() != 0
 }
-
-// fn print_tick_system(mut event_reader: EventReader<TickEvent>) {
-//     for _ in event_reader.iter() {
-//         println!("Tick");
-//     }
-// }