// ============================================================
// TTS Player — 语音播放器
// 职责：收集后端流式 tts_audio 片段，拼接后播放
// 格式：MVP 仅支持 audio/mp3，pcm 为 TODO
// ============================================================

type OnEndCallback = () => void;

export class TTSPlayer {
  private chunks: string[] = [];
  private audio: HTMLAudioElement | null = null;
  private _isPlaying = false;
  private onEndCallback: OnEndCallback | null = null;

  /** 注册播放完成回调 */
  onEnd(cb: OnEndCallback): void {
    this.onEndCallback = cb;
  }

  /** 当前是否正在播放 */
  get isPlaying(): boolean {
    return this._isPlaying;
  }

  /**
   * 入队一个 TTS 音频片段
   * @param base64 Base64 编码的音频数据
   * @param mimeType 音频格式（"audio/mp3" 或 "audio/pcm"）
   * @param isLast 是否为最后一个片段
   */
  enqueue(base64: string, mimeType: string, isLast: boolean): void {
    this.chunks.push(base64);

    if (isLast) {
      this.play(mimeType);
    }
  }

  /** 停止播放并清空缓冲区 */
  stop(): void {
    if (this.audio) {
      this.audio.pause();
      this.audio.removeAttribute("src");
      this.audio = null;
    }
    this.chunks = [];
    this._isPlaying = false;
  }

  /** 暂停播放 */
  pause(): void {
    this.audio?.pause();
  }

  /** 恢复播放 */
  resume(): void {
    this.audio?.play();
  }

  /** 拼接所有片段并播放 */
  private play(mimeType: string): void {
    if (this.chunks.length === 0) return;

    // 拼接所有 Base64 片段
    const combined = this.chunks.join("");
    this.chunks = [];

    // Base64 → Uint8Array → Blob
    const binary = atob(combined);
    const bytes = new Uint8Array(binary.length);
    for (let i = 0; i < binary.length; i++) {
      bytes[i] = binary.charCodeAt(i);
    }
    const blob = new Blob([bytes], { type: mimeType });
    const url = URL.createObjectURL(blob);

    // 播放
    const audio = new Audio(url);
    this.audio = audio;
    this._isPlaying = true;

    audio.onended = () => {
      URL.revokeObjectURL(url);
      this._isPlaying = false;
      this.audio = null;
      this.onEndCallback?.();
    };

    audio.onerror = () => {
      console.error("[TTS] 播放失败");
      URL.revokeObjectURL(url);
      this._isPlaying = false;
      this.audio = null;
      this.onEndCallback?.();
    };

    audio.play().catch((err) => {
      console.error("[TTS] play() 被拒绝:", err);
      this._isPlaying = false;
      this.audio = null;
      this.onEndCallback?.();
    });
  }
}