buzz/mobile/lib/shared/l10n/locale_provider.dart

import 'package:flutter/material.dart';
import 'package:hooks_riverpod/hooks_riverpod.dart';

import '../theme/theme_provider.dart';

const _localeKey = 'buzz_locale';

/// A null locale follows the operating system. Explicit choices are persisted
/// locally because language is a device preference, not relay protocol state.
class AppLocaleNotifier extends Notifier<Locale?> {
  @override
  Locale? build() {
    return switch (ref.read(savedPrefsProvider).getString(_localeKey)) {
      'en' => const Locale('en'),
      'zh_CN' => const Locale('zh', 'CN'),
      _ => null,
    };
  }

  void setLocale(Locale? locale) {
    state = locale;
    final prefs = ref.read(savedPrefsProvider);
    if (locale == null) {
      prefs.setString(_localeKey, 'system');
    } else if (locale.languageCode == 'zh') {
      prefs.setString(_localeKey, 'zh_CN');
    } else {
      prefs.setString(_localeKey, 'en');
    }
  }
}

final appLocaleProvider = NotifierProvider<AppLocaleNotifier, Locale?>(
  AppLocaleNotifier.new,
);