// lib/services/audio_service.dart
import 'dart:async';
import 'package:flutter/material.dart';
import 'playback_service.dart';

class Song {
  final String id;
  final String title;
  final String artist;
  final String? url;

  Song({
    required this.id,
    required this.title,
    required this.artist,
    this.url,
  });
}

class AudioService extends ChangeNotifier {
  Song? _currentSong;
  bool _isPlaying = false;
  Duration _position = Duration.zero;
  Duration _duration = Duration.zero;
  Duration _bufferedPosition = Duration.zero; // ✅ 新增：缓冲位置

  bool _listening = false;
  final List<StreamSubscription> _subscriptions = [];

  Song? get currentSong => _currentSong;
  bool get isPlaying => _isPlaying;
  Duration get position => _position;
  Duration get duration => _duration;
  Duration get bufferedPosition => _bufferedPosition; // ✅ 新增 getter

  Future<void> playSong(Song song) async {
    _currentSong = song;
    _position = Duration.zero;
    _duration = Duration.zero;
    _bufferedPosition = Duration.zero;

    _startListening();
    notifyListeners();

    if (song.url == null || song.url!.isEmpty) {
      return;
    }

    await PlaybackService().play(song.url!);
  }

  void togglePlay() {
    if (_currentSong == null) return;

    if (_isPlaying) {
      PlaybackService().pause();
    } else {
      PlaybackService().resume();
    }
  }

  void stopPlay() {
    _currentSong = null;
    _isPlaying = false;
    _position = Duration.zero;
    _duration = Duration.zero;
    _bufferedPosition = Duration.zero;
    _stopListening();
    notifyListeners();
  }

  void seekTo(Duration position) {
    PlaybackService().seek(position);
    _position = position;
    notifyListeners();
  }

  void _startListening() {
    if (_listening) return;
    _listening = true;

    final player = PlaybackService().player;

    _subscriptions.add(
      player.stream.playing.listen((playing) {
        if (_isPlaying != playing) {
          _isPlaying = playing;
          notifyListeners();
        }
      }),
    );

    _subscriptions.add(
      player.stream.position.listen((position) {
        if (_position != position) {
          _position = position;
          notifyListeners();
        }
      }),
    );

    _subscriptions.add(
      player.stream.duration.listen((duration) {
        if (_duration != duration) {
          _duration = duration;
          notifyListeners();
        }
      }),
    );

    // ✅ 新增：监听缓冲位置
    _subscriptions.add(
      player.stream.buffer.listen((buffer) {
        if (_bufferedPosition != buffer) {
          _bufferedPosition = buffer;
          notifyListeners();
        }
      }),
    );
  }

  void _stopListening() {
    _listening = false;
    for (final subscription in _subscriptions) {
      subscription.cancel();
    }
    _subscriptions.clear();
  }
}