import '../i18n/strings.g.dart';
import '../security/secret_store.dart';

/// Remembers the language the user picked in Settings so it survives restarts.
/// An empty/absent value means "follow the device language". Backed by the OS
/// keystore (via [SecretStore]), like the rest of the app's small preferences —
/// honouring "no plaintext at rest".
///
/// Why persist at all: the device language picker is an unreliable way to reach
/// minority languages (Android often doesn't offer Asturian, and slang would
/// fall back to the device default on every launch), so the choice made in-app
/// must be remembered explicitly. Asturian itself is modelled as the `es-AST`
/// locale (Spanish language + `AST` region), not `ast`, so Flutter's
/// Material/Cupertino localizations — which don't ship `ast` — resolve it
/// through Spanish instead of throwing. See [SettingsScreen] for the picker.
class LocaleStore {
  LocaleStore(this._store);

  final SecretStore _store;

  static const _key = 'tane.locale';

  /// The saved locale, or null when the user follows the device language.
  /// Unknown tags (e.g. a locale removed in a later build) also read as null.
  Future<AppLocale?> saved() async {
    final raw = await _store.read(_key);
    if (raw == null || raw.isEmpty) return null;
    for (final locale in AppLocale.values) {
      if (locale.name == raw) return locale;
    }
    return null;
  }

  /// Persists [locale] and applies it immediately.
  Future<void> setLocale(AppLocale locale) async {
    await _store.write(_key, locale.name);
    await LocaleSettings.setLocale(locale);
  }

  /// Forgets the explicit choice and follows the device language from now on.
  Future<void> useDeviceLocale() async {
    await _store.write(_key, '');
    await LocaleSettings.useDeviceLocale();
  }
}