Implement core "system" system

raidillon_core/src/lib.rs

@@ -1,5 +1,7 @@
 mod scene;
 mod engine;
+pub mod system;
 
 pub use scene::{Scene, SceneManager};
-pub use engine::Engine;
+pub use engine::Engine;
+pub use system::{System, SystemManager};

raidillon_core/src/system.rs

@@ -0,0 +1,35 @@
+use crate::Scene;
+use indexmap::IndexMap;
+
+pub struct SystemContext<'a> {
+    // TODO: time delta etc.
+    pub scene: &'a mut Scene,
+}
+
+pub trait System {
+    /// Initialize the system.
+    fn initialize(&mut self);
+    /// Spawn the first entities of the world.
+    fn load_world(&mut self, ctx: &mut SystemContext);
+    fn update(&mut self, ctx: &mut SystemContext);
+}
+
+pub type SystemID = String;
+pub struct SystemManager {
+    pub systems: IndexMap<SystemID, Box<dyn System>>,
+}
+
+impl SystemManager {
+    pub fn new() -> Self {
+        let systems = IndexMap::default();
+        Self { systems }
+    }
+
+    pub fn add_system(&mut self, id: SystemID, system: Box<dyn System>) {
+        self.systems.insert(id, system);
+    }
+
+    pub fn remove_system(&mut self, id: SystemID) {
+        self.systems.shift_remove(&id);
+    }
+}