fixed language switching in the frontend

app/Http/Middleware/HandleInertiaRequests.php

@@ -5,6 +5,7 @@ namespace App\Http\Middleware;
 use Illuminate\Foundation\Inspiring;
 use Illuminate\Http\Request;
 use Inertia\Middleware;
+use App\Support\LocaleConfig;
 
 class HandleInertiaRequests extends Middleware
 {
@@ -38,19 +39,10 @@ class HandleInertiaRequests extends Middleware
     {
         [$message, $author] = str(Inspiring::quotes()->random())->explode('-');
 
-        $supportedLocales = collect(explode(',', (string) env('APP_SUPPORTED_LOCALES', 'de,en')))
-            ->map(fn ($l) => trim((string) $l))
-            ->filter()
-            ->unique()
-            ->values()
-            ->all();
+        $supportedLocales = LocaleConfig::normalized();
+        $defaultLocale = LocaleConfig::canonicalize($supportedLocales[0] ?? null);
 
-        if (empty($supportedLocales)) {
-            $supportedLocales = array_values(array_unique(array_filter([
-                config('app.locale'),
-                config('app.fallback_locale'),
-            ])));
-        }
+        $currentLocale = LocaleConfig::canonicalize($request->route('locale') ?? $request->segment(1) ?? app()->getLocale());
 
         return [
             ...parent::share($request),
@@ -60,9 +52,10 @@ class HandleInertiaRequests extends Middleware
                 'user' => $request->user(),
             ],
             'supportedLocales' => $supportedLocales,
+            'defaultLocale' => $defaultLocale,
             'appUrl' => rtrim(config('app.url'), '/'),
             'sidebarOpen' => $request->cookie('sidebar_state', 'false') === 'true',
-            'locale' => app()->getLocale(),
+            'locale' => $currentLocale,
             'translations' => [
                 'marketing' => __('marketing'),
                 'auth' => __('auth'),