riverpod_theme_app: Service class for reading and writing theme settings from local storage.

theming_service_1.dart

class ThemingService {
  final SharedPreferences _prefs;
  ThemingService(this._prefs);

  static const _themeKey = 'theme';

  /// Loads the preferred theme from local storage with shared_preferences.
  /// Returns system theme initially if no theme is saved.
  ThemeMode themeMode() {
    final themeValue = _prefs.getInt(_themeKey);
    if (themeValue == null) return ThemeMode.system;

    return ThemeMode.values[themeValue];
  }

  /// Use the shared_preferences package to persist theme settings locally.
  Future<void> updateThemeMode(ThemeMode theme) async {
    await _prefs.setInt(_themeKey, theme.index);
  }
}