Add fruit spawning

src/fruit.rs

@@ -0,0 +1,85 @@
+use crate::{
+    grid,
+    snake::{self, SnakeHead, Z_HEIGHT},
+    tick::tick_triggered,
+};
+use bevy::prelude::*;
+use iyes_loopless::prelude::*;
+use rand::prelude::*;
+
+pub struct FruitPlugin;
+
+impl Plugin for FruitPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_event::<EatenEvent>()
+            .add_startup_system(spawn_fruit_system)
+            .add_system(
+                eat_fruit_system
+                    .run_if(tick_triggered)
+                    .before(snake::SystemLabel::SegmentMovement),
+            )
+            .add_system(debug_eaten_event_system)
+            .add_system(despawn_fruit_system)
+            .add_system(spawn_fruit_system.run_on_event::<EatenEvent>());
+    }
+}
+
+pub struct EatenEvent(Option<Entity>);
+
+#[derive(Component)]
+pub struct Fruit;
+
+fn spawn_fruit_system(mut commands: Commands) {
+    // TODO: not spawn in snake
+    let mut rng = rand::thread_rng();
+    let coordinate_range = 0..grid::SIZE;
+    let fruit_coordinate = grid::Coordinate(
+        rng.gen_range(coordinate_range.clone()),
+        rng.gen_range(coordinate_range),
+    );
+
+    commands
+        .spawn_bundle(SpriteBundle {
+            sprite: Sprite {
+                color: Color::GREEN,
+                custom_size: Some(Vec2::splat(grid::SEGMENT_SIZE) * 0.6),
+                ..Default::default()
+            },
+            transform: Transform::from_translation(Vec2::from(fruit_coordinate).extend(Z_HEIGHT)),
+            ..Default::default()
+        })
+        .insert(fruit_coordinate)
+        .insert(Fruit)
+        .insert(Name::new("Fruit"));
+}
+
+fn eat_fruit_system(
+    snake_head_query: Query<&grid::Coordinate, With<SnakeHead>>,
+    fruit_query: Query<(Entity, &grid::Coordinate), With<Fruit>>,
+    mut eaten_event_writer: EventWriter<EatenEvent>,
+) {
+    let &snake_head_coordinate = snake_head_query.single();
+
+    for (fruit, &fruit_coordinate) in fruit_query.iter() {
+        if snake_head_coordinate == fruit_coordinate {
+            eaten_event_writer.send(EatenEvent(Some(fruit)));
+        }
+    }
+}
+
+fn despawn_fruit_system(mut commands: Commands, mut event_reader: EventReader<EatenEvent>) {
+    for &EatenEvent(fruit) in event_reader.iter() {
+        if let Some(fruit) = fruit {
+            commands.entity(fruit).despawn();
+        }
+    }
+}
+
+fn debug_eaten_event_system(
+    mut event_writer: EventWriter<EatenEvent>,
+    keypress: Res<Input<KeyCode>>,
+) {
+    if keypress.just_pressed(KeyCode::Space) {
+        event_writer.send(EatenEvent(None));
+    }
+}