update: add a physic scenne

src/stateManager/InteractionManager.ts

@@ -0,0 +1,87 @@
+export type InteractableKind = "grab" | "trigger";
+
+export interface InteractableHandle {
+  kind: InteractableKind;
+  label: string;
+  onPress: () => void;
+  onRelease: () => void;
+}
+
+export interface InteractionSnapshot {
+  focused: InteractableHandle | null;
+  holding: boolean;
+}
+
+export class InteractionManager {
+  private static _instance: InteractionManager | null = null;
+
+  private _focused: InteractableHandle | null = null;
+  private _holding = false;
+  private _holdingHandle: InteractableHandle | null = null;
+  private readonly _listeners = new Set<() => void>();
+
+  static getInstance(): InteractionManager {
+    if (!InteractionManager._instance) {
+      InteractionManager._instance = new InteractionManager();
+    }
+
+    return InteractionManager._instance;
+  }
+
+  private constructor() {}
+
+  getState(): InteractionSnapshot {
+    return {
+      focused: this._focused,
+      holding: this._holding,
+    };
+  }
+
+  setFocused(handle: InteractableHandle | null): void {
+    if (this._focused === handle) return;
+    // Never interrupt an active grab via focus change
+    if (this._holding) {
+      this._focused = handle;
+      this._emit();
+      return;
+    }
+    this._focused = handle;
+    this._emit();
+  }
+
+  pressInteract(): void {
+    if (!this._focused) return;
+
+    this._holding = this._focused.kind === "grab";
+    if (this._holding) this._holdingHandle = this._focused;
+    this._focused.onPress();
+    this._emit();
+  }
+
+  releaseInteract(): void {
+    const handle = this._holdingHandle ?? this._focused;
+    if (!handle) return;
+
+    handle.onRelease();
+    this._holding = false;
+    this._holdingHandle = null;
+    this._emit();
+  }
+
+  subscribe(listener: () => void): () => void {
+    this._listeners.add(listener);
+
+    return () => {
+      this._listeners.delete(listener);
+    };
+  }
+
+  destroy(): void {
+    this._listeners.clear();
+    InteractionManager._instance = null;
+  }
+
+  private _emit(): void {
+    this._listeners.forEach((cb) => cb());
+  }
+}