feat(ecs): add extensions

1 files changed, 77 insertions, 0 deletions

diff --git a/ecs/examples/extension.rs b/ecs/examples/extension.rs
new file mode 100644
index 0000000..2022b05
--- /dev/null
+++ b/ecs/examples/extension.rs
@@ -0,0 +1,77 @@
+use ecs::actions::Actions;
+use ecs::event::Event;
+use ecs::extension::{Collector as ExtensionCollector, Extension};
+use ecs::{Component, Query, World};
+
+#[derive(Debug, Component)]
+struct Position
+{
+    x: u32,
+    y: u32,
+}
+
+#[derive(Debug, Component)]
+struct EnemySpawnSource;
+
+#[derive(Debug, Component)]
+enum EvilnessLevel
+{
+    Medium,
+}
+
+#[derive(Debug)]
+struct Update;
+
+impl Event for Update {}
+
+fn spawn_enemies(
+    spawner_query: Query<(EnemySpawnSource, Position)>,
+    enemies_query: Query<(EvilnessLevel,)>,
+    mut actions: Actions,
+)
+{
+    let Some((_, enemy_spawner_position)) = spawner_query.iter().next() else {
+        return;
+    };
+
+    let enemy_cnt = enemies_query.iter().count();
+
+    if enemy_cnt > 3 {
+        return;
+    }
+
+    actions.spawn((
+        EvilnessLevel::Medium,
+        Position {
+            x: enemy_spawner_position.x * enemy_cnt as u32,
+            y: enemy_spawner_position.y,
+        },
+    ));
+
+    println!("Spawned enemy with medium evilness and 45 strength");
+}
+
+struct EnemySpawningExtension;
+
+impl Extension for EnemySpawningExtension
+{
+    fn collect(self, mut collector: ExtensionCollector<'_>)
+    {
+        collector.add_system(Update, spawn_enemies);
+
+        collector.add_entity((Position { x: 187, y: 30 }, EnemySpawnSource));
+    }
+}
+
+fn main()
+{
+    let mut world = World::new();
+
+    world.add_extension(EnemySpawningExtension);
+
+    for _ in 0..7 {
+        world.emit(Update);
+
+        world.perform_queued_actions();
+    }
+}