feat(localization): Improve locale resolution and add Chinese script variants

lib/core/providers/app_providers.dart

@@ -105,14 +105,40 @@ class AppLocale extends _$AppLocale {
     _storage = ref.watch(optimizedStorageServiceProvider);
     final code = _storage.getLocaleCode();
     if (code != null && code.isNotEmpty) {
-      return Locale(code);
+      final parsed = _parseLocaleCode(code);
+      if (parsed != null) return parsed;
     }
     return null; // system default
   }
 
   Future<void> setLocale(Locale? locale) async {
     state = locale;
-    await _storage.setLocaleCode(locale?.languageCode);
+    await _storage.setLocaleCode(locale?.toLanguageTag());
+  }
+
+  Locale? _parseLocaleCode(String code) {
+    final normalized = code.replaceAll('_', '-');
+    final parts = normalized.split('-');
+    if (parts.isEmpty || parts.first.isEmpty) return null;
+
+    final language = parts.first;
+    String? script;
+    String? country;
+
+    for (var i = 1; i < parts.length; i++) {
+      final part = parts[i];
+      if (part.length == 4) {
+        script = '${part[0].toUpperCase()}${part.substring(1).toLowerCase()}';
+      } else if (part.length == 2 || part.length == 3) {
+        country = part.toUpperCase();
+      }
+    }
+
+    return Locale.fromSubtags(
+      languageCode: language,
+      scriptCode: script,
+      countryCode: country,
+    );
   }
 }
 

lib/features/profile/views/app_customization_page.dart

@@ -38,7 +38,7 @@ class AppCustomizationPage extends ConsumerWidget {
       return l10n.currentlyUsingLightTheme;
     }();
     final locale = ref.watch(appLocaleProvider);
-    final currentLanguageCode = locale?.languageCode ?? 'system';
+    final currentLanguageCode = locale?.toLanguageTag() ?? 'system';
     final languageLabel = _resolveLanguageLabel(context, currentLanguageCode);
     final activeTheme = ref.watch(appThemePaletteProvider);
 
@@ -198,7 +198,7 @@ class AppCustomizationPage extends ConsumerWidget {
   Widget _buildLanguageSection(
     BuildContext context,
     WidgetRef ref,
-    String currentLanguageCode,
+    String currentLanguageTag,
     String languageLabel,
   ) {
     final theme = context.conduitTheme;
@@ -220,15 +220,16 @@ class AppCustomizationPage extends ConsumerWidget {
           onTap: () async {
             final selected = await _showLanguageSelector(
               context,
-              currentLanguageCode,
+              currentLanguageTag,
             );
             if (selected == null) return;
             if (selected == 'system') {
               await ref.read(appLocaleProvider.notifier).setLocale(null);
             } else {
+              final parsed = _parseLocaleTag(selected);
               await ref
                   .read(appLocaleProvider.notifier)
-                  .setLocale(Locale(selected));
+                  .setLocale(parsed ?? Locale(selected));
             }
           },
         ),
@@ -1741,6 +1742,8 @@ class AppCustomizationPage extends ConsumerWidget {
   }
 
   String _resolveLanguageLabel(BuildContext context, String code) {
+    final normalizedCode = code.replaceAll('_', '-');
+
     switch (code) {
       case 'en':
         return AppLocalizations.of(context)!.english;
@@ -1757,10 +1760,21 @@ class AppCustomizationPage extends ConsumerWidget {
       case 'ru':
         return AppLocalizations.of(context)!.russian;
       case 'zh':
-        return AppLocalizations.of(context)!.chinese;
+        return AppLocalizations.of(context)!.chineseSimplified;
       case 'ko':
         return AppLocalizations.of(context)!.korean;
+      case 'zh-Hant':
+        return AppLocalizations.of(context)!.chineseTraditional;
       default:
+        if (normalizedCode == 'zh-hant') {
+          return AppLocalizations.of(context)!.chineseTraditional;
+        }
+        if (normalizedCode == 'zh') {
+          return AppLocalizations.of(context)!.chineseSimplified;
+        }
+        if (normalizedCode == 'ko') {
+          return AppLocalizations.of(context)!.korean;
+        }
         return AppLocalizations.of(context)!.system;
     }
   }
@@ -1929,6 +1943,8 @@ class AppCustomizationPage extends ConsumerWidget {
   }
 
   Future<String?> _showLanguageSelector(BuildContext context, String current) {
+    final normalizedCurrent = current.replaceAll('_', '-');
+
     return showModalBottomSheet<String>(
       context: context,
       backgroundColor: Colors.transparent,
@@ -1949,52 +1965,79 @@ class AppCustomizationPage extends ConsumerWidget {
               const SizedBox(height: Spacing.sm),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.system),
-                trailing: current == 'system' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'system'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'system'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.english),
-                trailing: current == 'en' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'en'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'en'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.deutsch),
-                trailing: current == 'de' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'de'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'de'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.espanol),
-                trailing: current == 'es' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'es'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'es'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.francais),
-                trailing: current == 'fr' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'fr'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'fr'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.italiano),
-                trailing: current == 'it' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'it'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'it'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.nederlands),
-                trailing: current == 'nl' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'nl'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'nl'),
               ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.russian),
-                trailing: current == 'ru' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'ru'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'ru'),
               ),
               ListTile(
-                title: Text(AppLocalizations.of(context)!.chinese),
+                title: Text(AppLocalizations.of(context)!.chineseSimplified),
-                trailing: current == 'zh' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'zh'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'zh'),
               ),
+              ListTile(
+                title: Text(AppLocalizations.of(context)!.chineseTraditional),
+                trailing: normalizedCurrent == 'zh-Hant'
+                    ? const Icon(Icons.check)
+                    : null,
+                onTap: () => Navigator.pop(context, 'zh-Hant'),
+              ),
               ListTile(
                 title: Text(AppLocalizations.of(context)!.korean),
-                trailing: current == 'ko' ? const Icon(Icons.check) : null,
+                trailing: normalizedCurrent == 'ko'
+                    ? const Icon(Icons.check)
+                    : null,
                 onTap: () => Navigator.pop(context, 'ko'),
               ),
               const SizedBox(height: Spacing.sm),
@@ -2006,6 +2049,31 @@ class AppCustomizationPage extends ConsumerWidget {
   }
 }
 
+Locale? _parseLocaleTag(String code) {
+  final normalized = code.replaceAll('_', '-');
+  final parts = normalized.split('-');
+  if (parts.isEmpty || parts.first.isEmpty) return null;
+
+  final language = parts.first;
+  String? script;
+  String? country;
+
+  for (var i = 1; i < parts.length; i++) {
+    final part = parts[i];
+    if (part.length == 4) {
+      script = '${part[0].toUpperCase()}${part.substring(1).toLowerCase()}';
+    } else if (part.length == 2 || part.length == 3) {
+      country = part.toUpperCase();
+    }
+  }
+
+  return Locale.fromSubtags(
+    languageCode: language,
+    scriptCode: script,
+    countryCode: country,
+  );
+}
+
 class _PaletteOption extends StatelessWidget {
   const _PaletteOption({
     required this.themeDefinition,

lib/l10n/app_de.arb

@@ -178,6 +178,8 @@
   "nederlands": "Niederländisch",
   "russian": "Russisch",
   "chinese": "Chinesisch",
+  "chineseSimplified": "Chinesisch (Vereinfacht)",
+  "chineseTraditional": "Chinesisch (Traditionell)",
   "korean": "Koreanisch",
   "deleteMessagesTitle": "Nachrichten löschen",
   "deleteMessagesMessage": "{count} Nachrichten löschen?",

lib/l10n/app_en.arb

@@ -862,6 +862,14 @@
   "@chinese": {
     "description": "Language name: Chinese."
   },
+  "chineseSimplified": "Chinese (Simplified)",
+  "@chineseSimplified": {
+    "description": "Language name: Chinese (Simplified)."
+  },
+  "chineseTraditional": "Chinese (Traditional)",
+  "@chineseTraditional": {
+    "description": "Language name: Chinese (Traditional)."
+  },
   "korean": "한국어",
   "@korean": {
     "description": "Language name: Korean."

lib/l10n/app_es.arb

@@ -178,6 +178,8 @@
   "nederlands": "Nederlands",
   "russian": "Русский",
   "chinese": "中文",
+  "chineseSimplified": "Chino (simplificado)",
+  "chineseTraditional": "Chino (tradicional)",
   "korean": "한국어",
   "deleteMessagesTitle": "Eliminar mensajes",
   "deleteMessagesMessage": "¿Eliminar {count} mensajes?",

lib/l10n/app_fr.arb

@@ -178,6 +178,8 @@
   "nederlands": "Néerlandais",
   "russian": "Russe",
   "chinese": "Chinois",
+  "chineseSimplified": "Chinois (simplifié)",
+  "chineseTraditional": "Chinois (traditionnel)",
   "korean": "Coréen",
   "deleteMessagesTitle": "Supprimer les messages",
   "deleteMessagesMessage": "Supprimer {count} messages ?",

lib/l10n/app_it.arb

@@ -178,6 +178,8 @@
   "nederlands": "Olandese",
   "russian": "Russo",
   "chinese": "Cinese",
+  "chineseSimplified": "Cinese (semplificato)",
+  "chineseTraditional": "Cinese (tradizionale)",
   "korean": "Coreano",
   "deleteMessagesTitle": "Elimina messaggi",
   "deleteMessagesMessage": "Eliminare {count} messaggi?",

lib/l10n/app_ko.arb

@@ -286,6 +286,8 @@
   "nederlands": "Nederlands",
   "russian": "Русский",
   "chinese": "中文",
+  "chineseSimplified": "중국어(간체)",
+  "chineseTraditional": "중국어(번체)",
   "korean": "한국어",
   "deleteMessagesTitle": "메시지 삭제",
   "deleteMessagesMessage": "{count}개의 메시지를 삭제하시겠습니까?",

lib/l10n/app_nl.arb

@@ -178,6 +178,8 @@
   "nederlands": "Nederlands",
   "russian": "Русский",
   "chinese": "中文",
+  "chineseSimplified": "Chinees (vereenvoudigd)",
+  "chineseTraditional": "Chinees (traditioneel)",
   "korean": "한국어",
   "deleteMessagesTitle": "Berichten verwijderen",
   "deleteMessagesMessage": "{count} berichten verwijderen?",

lib/l10n/app_ru.arb

@@ -178,6 +178,8 @@
   "nederlands": "Nederlands",
   "russian": "Русский",
   "chinese": "中文",
+  "chineseSimplified": "Китайский (упрощённый)",
+  "chineseTraditional": "Китайский (традиционный)",
   "korean": "한국어",
   "deleteMessagesTitle": "Удалить сообщения",
   "deleteMessagesMessage": "Удалить {count, plural, one{{count} сообщение} few{{count} сообщения} other{{count} сообщений}}?",

lib/l10n/app_zh.arb

@@ -178,6 +178,8 @@
   "nederlands": "Nederlands",
   "russian": "Русский",
   "chinese": "中文",
+  "chineseSimplified": "简体中文",
+  "chineseTraditional": "繁體中文",
   "korean": "한국어",
   "deleteMessagesTitle": "删除消息",
   "deleteMessagesMessage": "删除 {count} 条消息？",

lib/l10n/app_zh_Hant.arb

@@ -178,6 +178,8 @@
   "nederlands": "Nederlands",
   "russian": "Русский",
   "chinese": "中文",
+  "chineseSimplified": "簡體中文",
+  "chineseTraditional": "繁體中文",
   "korean": "한국어",
   "deleteMessagesTitle": "刪除消息",
   "deleteMessagesMessage": "刪除 {count} 條消息？",

lib/main.dart

@@ -189,12 +189,8 @@ class _ConduitAppState extends ConsumerState<ConduitApp> {
           if (deviceLocales == null || deviceLocales.isEmpty) {
             return supported.first;
           }
-          for (final device in deviceLocales) {
+          final resolved = _resolveSupportedLocale(deviceLocales, supported);
-            for (final loc in supported) {
+          return resolved ?? supported.first;
-              if (loc.languageCode == device.languageCode) return loc;
-            }
-          }
-          return supported.first;
         },
         builder: (context, child) {
           final brightness = Theme.of(context).brightness;
@@ -221,6 +217,73 @@ class _ConduitAppState extends ConsumerState<ConduitApp> {
       ),
     );
   }
+
+  bool _prefersTraditionalChinese(Locale deviceLocale) {
+    final script = deviceLocale.scriptCode?.toLowerCase();
+    if (script == 'hant') return true;
+
+    final country = deviceLocale.countryCode?.toUpperCase();
+    return country == 'TW' || country == 'HK' || country == 'MO';
+  }
+
+  Locale? _resolveSupportedLocale(
+    List<Locale>? deviceLocales,
+    Iterable<Locale> supported,
+  ) {
+    if (deviceLocales == null || deviceLocales.isEmpty) return null;
+
+    for (final device in deviceLocales) {
+      final prefersTraditional = _prefersTraditionalChinese(device);
+      final deviceLanguage = device.languageCode.toLowerCase();
+      final deviceScript = device.scriptCode?.toLowerCase();
+      final deviceCountry = device.countryCode?.toUpperCase();
+
+      // Pass 1: match language with script (or preferred Traditional)
+      for (final loc in supported) {
+        final languageMatches =
+            loc.languageCode.toLowerCase() == deviceLanguage;
+        if (!languageMatches) continue;
+
+        final locScript = loc.scriptCode?.toLowerCase();
+        final scriptMatches =
+            locScript != null &&
+            locScript.isNotEmpty &&
+            (locScript == deviceScript ||
+                (loc.languageCode == 'zh' &&
+                    locScript == 'hant' &&
+                    prefersTraditional));
+        if (!scriptMatches) continue;
+
+        final locCountry = loc.countryCode?.toUpperCase();
+        final countryMatches =
+            locCountry == null ||
+            locCountry.isEmpty ||
+            locCountry == deviceCountry;
+
+        if (countryMatches) {
+          return loc;
+        }
+      }
+
+      // Pass 2: prefer Traditional Chinese when applicable
+      if (prefersTraditional) {
+        for (final loc in supported) {
+          if (loc.languageCode == 'zh' && loc.scriptCode == 'Hant') {
+            return loc;
+          }
+        }
+      }
+
+      // Pass 3: language-only match
+      for (final loc in supported) {
+        if (loc.languageCode.toLowerCase() == deviceLanguage) {
+          return loc;
+        }
+      }
+    }
+
+    return null;
+  }
 }
 
 /// Dismisses the soft keyboard whenever the user scrolls.