WebAPP/app/Http/Middleware/SetLocaleMiddleware.php

<?php

namespace App\Http\Middleware;

use Carbon\Carbon;
use Closure;
use Illuminate\Http\Request;
use Symfony\Component\HttpFoundation\Response;

class SetLocaleMiddleware
{
    private const SUPPORTED_LOCALES = ['de', 'en', 'pl', 'ru', 'ar', 'tr'];

    public function handle(Request $request, Closure $next): Response
    {
        $locale = $this->resolveLocale($request);

        app()->setLocale($locale);
        Carbon::setLocale($locale);

        return $next($request);
    }

    private function resolveLocale(Request $request): string
    {
        // 1. Eingeloggter User → DB-Präferenz
        if ($request->user() && in_array($request->user()->locale, self::SUPPORTED_LOCALES)) {
            return $request->user()->locale;
        }

        // 2. Session (für Gastseiten)
        if (session()->has('locale') && in_array(session('locale'), self::SUPPORTED_LOCALES)) {
            return session('locale');
        }

        // 3. Fallback
        return 'de';
    }

    public static function supportedLocales(): array
    {
        return self::SUPPORTED_LOCALES;
    }
}