nkbmusic/lib/data/user_library.dart

import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../audio/player_providers.dart';

/// Overridden in main() once SharedPreferences has loaded.
final sharedPrefsProvider = Provider<SharedPreferences>(
  (ref) => throw UnimplementedError('sharedPrefsProvider must be overridden in main()'),
);

/// Liked song ids, stored on the device. Synced to Supabase once sign-in is wired up.
class LikedSongs extends Notifier<Set<String>> {
  static const _key = 'liked_track_ids';

  @override
  Set<String> build() => {...?ref.watch(sharedPrefsProvider).getStringList(_key)};

  bool isLiked(String id) => state.contains(id);

  void toggle(String id) {
    state = state.contains(id) ? ({...state}..remove(id)) : {...state, id};
    ref.read(sharedPrefsProvider).setStringList(_key, state.toList());
  }
}

final likedSongsProvider = NotifierProvider<LikedSongs, Set<String>>(LikedSongs.new);

/// Most recent first, capped at 30.
class RecentlyPlayed extends Notifier<List<String>> {
  static const _key = 'recent_track_ids';
  static const _max = 30;

  @override
  List<String> build() {
    ref.listen(mediaItemProvider, (_, next) {
      final id = next.value?.id;
      if (id != null && (state.isEmpty || state.first != id)) _push(id);
    });
    return ref.watch(sharedPrefsProvider).getStringList(_key) ?? const [];
  }

  void _push(String id) {
    state = [id, ...state.where((e) => e != id)].take(_max).toList();
    ref.read(sharedPrefsProvider).setStringList(_key, state);
  }
}

final recentlyPlayedProvider = NotifierProvider<RecentlyPlayed, List<String>>(RecentlyPlayed.new);