// engine.js — 场景引擎
//
// 场景数据结构：
//   narrate      : string | fn(state)→string   旁白文本（TTS 兜底）
//   narrateAudio : string | fn(state)→string   旁白预录 MP3 路径（优先于 TTS）
//   audio        : string[]                     角色语音（播放完后才显示选项）
//   bgm          : string | null | undefined    undefined=不变 null=停止 string=切换
//   delay        : number                       自动跳转前的等待毫秒
//   tap       : { label, narrate, narrateAudio, audio, state, next }   单击操作
//   doubleTap : { label, narrate, narrateAudio, audio, state, next }   双击操作
//   next      : string | fn(state) | null    无选项时自动跳转（null=结局）
//
// state/next 可以是函数 fn(currentState)=>值

class SceneEngine {
  constructor() {
    this._game    = null;
    this._state   = {};
    this._scene   = null;
    this._waiting = false;
    this._input   = null;
    this._onEnd   = null;
  }

  // ── 运行游戏 ──
  async run(game, input, onEnd) {
    this._game  = game;
    this._state = JSON.parse(JSON.stringify(game.initialState || {}));
    this._scene = null;
    this._waiting = false;
    this._input = input;
    this._onEnd = onEnd;

    // 接管输入
    input.onTap      = () => this._tap();
    input.onDoubleTap = () => this._dt();

    // 清场
    Narrator.stop();
    Snd.stopVoice();
    Snd.stopBGM(0);
    Snd.stopAmbience();

    dbg(`[engine] start ${game.id}`);

    if (game.bgm)      Snd.startBGM(game.bgm, { vol: 0.18 });
    if (game.ambience) Snd.startAmbience(game.ambience, { vol: 0.15 });

    await Narrator.sayAndWait(game.intro);
    await this._goto(game.first);
  }

  // ── 跳转到场景 ──
  async _goto(id) {
    if (id === null || id === undefined) {
      this._ending();
      return;
    }

    const scene = this._game.scenes[id];
    if (!scene) { console.error('[engine] missing scene:', id); return; }

    this._scene   = scene;
    this._waiting = false;
    Narrator.clearOptions();

    dbg(`[scene] ${id}`);

    // BGM 切换
    if (scene.bgm !== undefined) {
      if (scene.bgm) Snd.startBGM(scene.bgm, { vol: 0.18 });
      else           Snd.stopBGM(1500);
    }

    // 播放音频（等完）
    const sceneAudio = this._r(scene.audio);
    if (sceneAudio && sceneAudio.length > 0) {
      await this._playAudio(sceneAudio);
    }

    // 旁白描述（等完）— 优先播放预录音频，否则 TTS
    if (scene.narrateAudio || scene.narrate) {
      await this._sayNarrate(scene);
    }

    // 有选项 → 等待输入
    if (scene.tap || scene.doubleTap) {
      this._waiting = true;
      Narrator.options(
        scene.tap       ? scene.tap.label       : null,
        scene.doubleTap ? scene.doubleTap.label : null,
      );
      return;
    }

    // 无选项 → 自动跳转
    if (scene.delay) await new Promise(r => setTimeout(r, scene.delay));
    await this._goto(this._r(scene.next));
  }

  // ── 执行一个操作 ──
  async _exec(action) {
    this._waiting = false;
    Narrator.clearOptions();
    Narrator.stop();     // 打断正在播报的选项提示

    Haptic.select();

    // 更新状态
    if (action.state) {
      const updates = this._r(action.state);
      Object.assign(this._state, updates);
    }

    // 反应音频（支持函数型）
    const actionAudio = this._r(action.audio);
    if (actionAudio && actionAudio.length > 0) {
      await this._playAudio(actionAudio);
    }

    // 反应旁白
    if (action.narrateAudio || action.narrate) {
      await this._sayNarrate(action);
    }

    await this._goto(this._r(action.next));
  }

  _tap() {
    if (!this._waiting || !this._scene?.tap) return;
    this._exec(this._scene.tap);
  }

  _dt() {
    if (!this._waiting || !this._scene?.doubleTap) return;
    this._exec(this._scene.doubleTap);
  }

  // ── 结局 ──
  async _ending() {
    Snd.stopBGM(3000);
    Snd.stopAmbience();
    const id = this._game.getEnding(this._state);
    const e  = this._game.endings?.[id];
    dbg(`[ending] ${id}`);
    SFX_UI.ending();
    if (e) {
      await this._sayNarrate(e);
    } else {
      await Narrator.sayAndWait('游戏结束。');
    }
    await new Promise(r => setTimeout(r, 2000));
    await Narrator.sayAndWait('感谢体验。');
    await new Promise(r => setTimeout(r, 3000));
    if (this._onEnd) this._onEnd();
  }

  // ── 旁白：优先预录 MP3，兜底 TTS ──
  _sayNarrate(node) {
    const audioPath = this._r(node.narrateAudio);
    if (audioPath) {
      return this._playAudio([audioPath]);
    }
    const text = this._r(node.narrate);
    if (text) return Narrator.sayAndWait(text);
    return Promise.resolve();
  }

  // ── 播放多段音频（顺序，等完）──
  _playAudio(urls) {
    return new Promise(resolve => {
      Snd.playVoice(urls, { onEnd: resolve });
    });
  }

  // ── 解析 string | fn(state) ──
  _r(val) {
    return typeof val === 'function' ? val(this._state) : val;
  }
}