// Author: fruit.com.cn

import 'package:flutter/widgets.dart';
import 'package:shared_preferences/shared_preferences.dart';

/// Resolves the selected or system language to one of the supported app locales.
///
/// Indonesian is the launch-market fallback when a device uses an unsupported
/// language. The legacy `in` code is treated as Indonesian as well.
Locale resolveAppLocale(Locale? selected, Locale? deviceLocale) {
  final code = (selected ?? deviceLocale)?.languageCode;
  return switch (code) {
    'zh' => const Locale('zh'),
    'en' => const Locale('en'),
    _ => const Locale('id'),
  };
}

class LocaleController extends ChangeNotifier {
  LocaleController({SharedPreferencesAsync? preferences})
    : _preferences = preferences ?? SharedPreferencesAsync();

  final SharedPreferencesAsync _preferences;
  Locale? _locale;
  Locale? get locale => _locale;

  Future<void> load() async {
    try {
      final code = await _preferences.getString('ui.locale');
      _locale = switch (code) {
        'en' => const Locale('en'),
        'zh' => const Locale('zh'),
        'id' => const Locale('id'),
        _ => null,
      };
      notifyListeners();
    } catch (_) {
      // The system locale remains usable if preferences are unavailable.
    }
  }

  Future<void> select(String code) async {
    _locale = switch (code) {
      'en' => const Locale('en'),
      'zh' => const Locale('zh'),
      'id' => const Locale('id'),
      _ => null,
    };
    notifyListeners();
    try {
      await _preferences.setString('ui.locale', code);
    } catch (_) {
      // Preference persistence is best effort for this prototype.
    }
  }
}