Ambient Music Player for Classroom Teacher Relaxation

/// Global singleton — call AudioController.instance from anywhere.
class AudioController extends ChangeNotifier {
  static final AudioController instance = AudioController._();

  // Playback state (read-only from the outside)
  MusicTrack? get currentTrack => _currentTrack;
  bool get isPlaying => _isPlaying;
  Duration get position => _position;
  Duration get duration => _duration;
  String? get error => _error;

  // Playlist navigation helpers
  bool get hasPrevious => _currentIndex > 0;
  bool get hasNext =>
      _playlist.isNotEmpty && _currentIndex < _playlist.length - 1;

  // Progress as a 0.0–1.0 fraction (safe for LinearProgressIndicator)
  double get progress { ... }

  // Core actions
  Future<void> playTrack(MusicTrack track, {List<MusicTrack>? playlist});
  Future<void> togglePlayPause();
  Future<void> previous();
  Future<void> next();
  Future<void> stop();
  void seek(Duration position);

  // Formats a Duration as "MM:SS"
  String formatDuration(Duration d);
}

flutter:
  assets:
    - assets/audio/Sonido-del-bosque.mp3
    - assets/audio/Lluvia-Suave.mp3
    - assets/audio/Musica-energizante.mp3

class MusicTrack {
  const MusicTrack({
    required this.id,           // Unique identifier: 'forest' | 'rain' | 'energizing'
    required this.titleEs,      // Display title in Spanish
    required this.titleQu,      // Display title in Kichwa
    required this.descriptionEs, // Short description in Spanish
    required this.descriptionQu, // Short description in Kichwa
    required this.assetPath,    // Flutter asset path, e.g. 'assets/audio/...'
    required this.isAsset,      // true = load as asset; false = load from url
    this.url,                   // Optional remote URL (not used in current release)
  });

  final String id;
  final String titleEs;
  final String titleQu;
  final String descriptionEs;
  final String descriptionQu;
  final String assetPath;
  final bool isAsset;
  final String? url;

  // Language-aware accessors
  String title(bool isKichwa) => isKichwa ? titleQu : titleEs;
  String description(bool isKichwa) => isKichwa ? descriptionQu : descriptionEs;
}