import * as THREE from "three";
import { BaseScene } from "./scenes/BaseScene";
import type { SceneKey } from "./SceneKeys";

/**
 * 场景生命周期管理器。
 *
 * 管理多个 BaseScene 实例的注册、切换和更新。
 * 同一时刻只有一个活跃场景，切换时自动调用 exit/enter。
 */
export class SceneManager {
  private scenes = new Map<SceneKey, BaseScene>();
  private _activeScene: BaseScene | null = null;
  private _camera: THREE.PerspectiveCamera;

  constructor(camera: THREE.PerspectiveCamera) {
    this._camera = camera;
  }

  get activeScene(): BaseScene | null {
    return this._activeScene;
  }

  get activeThreeScene(): THREE.Scene | null {
    return this._activeScene?.scene ?? null;
  }

  register(...scenes: BaseScene[]): void {
    for (const s of scenes) {
      s._bind((key) => this.switchTo(key));
      this.scenes.set(s.key, s);
    }
  }

  switchTo(key: SceneKey): void {
    const next = this.scenes.get(key);
    if (!next) {
      console.warn(`[SceneManager] Scene "${key}" not registered`);
      return;
    }

    if (this._activeScene) {
      this._activeScene.exit();
    }

    if (!next["_initialized"]) {
      next.init(this._camera);
    }

    next.enter();
    this._activeScene = next;

    if (typeof __DEV__ !== "undefined" && __DEV__) {
      console.log(`[SceneManager] → ${key}`);
    }
  }

  update(dt: number, elapsed: number): void {
    this._activeScene?.update(dt, elapsed);
  }

  dispose(): void {
    for (const s of this.scenes.values()) {
      s.dispose();
    }
    this.scenes.clear();
    this._activeScene = null;
  }
}