Improve Scene & SceneManager system

- Implement AsRef and AsMut for Scene
- Add "new" method to SceneManager

raidillon_core/src/scene.rs

@@ -1,30 +1,63 @@
+use std::collections::HashMap;
+
 pub struct Scene {
     title: String,
     world: hecs::World,
     skybox_texture_path: String,
 }
 
+impl AsRef<Scene> for Scene {
+    fn as_ref(&self) -> &Scene {
+        &self
+    }
+}
+
+impl AsMut<Scene> for Scene {
+    fn as_mut(&mut self) -> &mut Scene {
+        self
+    }
+}
+
+type SceneID = String;
+
 pub struct SceneManager {
-    scenes: Vec<Option<Scene>>,
-    active_index: usize,
+    scenes: HashMap<SceneID, Scene>,
+    active_scene: Option<SceneID>,
 }
 
 impl SceneManager {
+    pub fn new() -> Self {
+        let scenes = HashMap::new();
+        Self {
+            scenes,
+            active_scene: None,
+        }
+    }
+
     pub fn current(&self) -> &Scene {
-        self.scenes[self.active_index].as_ref().unwrap()
+        match &self.active_scene {
+            Some(id) => self.scenes[id].as_ref(),
+            None => panic!("No active scene"),
+        }
+
     }
 
     pub fn current_mut(&mut self) -> &mut Scene {
-        self.scenes[self.active_index].as_mut().unwrap()
+        match &mut self.active_scene {
+            Some(id) => self.scenes.get_mut(id.as_mut()).unwrap().as_mut(),
+            None => panic!("No active scene"),
+        }
     }
 
-    pub fn add_scene(&mut self, scene: Scene) -> usize {
-        let idx = self.scenes.len();
-        self.scenes.push(Some(scene));
-        idx
+    pub fn set_active_scene(&mut self, scene: SceneID) {
+        self.active_scene = Some(scene);
     }
 
-    pub fn remove_scene(&mut self, idx: usize) {
-        self.scenes[idx] = None;
+    pub fn add_scene(&mut self, id: SceneID, scene: Scene) {
+        self.scenes.insert(id, scene);
     }
-}
+
+    pub fn remove_scene(&mut self, id: SceneID) {
+        self.scenes.remove(&id);
+    }
+}