ldc-groupe/app/Http/Middleware/ForceLocale.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\App;
use Illuminate\Support\Facades\Session;
use Illuminate\Support\Str;
use Illuminate\Validation\ValidationException;
use Mcamara\LaravelLocalization\Facades\LaravelLocalization;

class ForceLocale
{
    /**
     * This middleware forces the locale:
     * - when it is changed from the back office
     * - and when the form submitted in the request belongs to a different locale
     *
     * The issue occurred when two browser tabs were open in different locales:
     * the data being saved could end up using the other tab’s locale.
     *
     * @param \Illuminate\Http\Request $request
     * @param Closure                  $next
     * @return mixed
     * @throws ValidationException Not supported locale.
     */
    public function handle(Request $request, Closure $next): mixed
    {
        $routeName = $request->route()?->getName();
        if (! $routeName || ! Str::startsWith($routeName, 'back.')) {
            return $next($request);
        }

        $locale = (Session::has('lang')) ? Session::get('lang') : config('app.fallback_locale');
        App::setLocale($locale);

        // 1. Is Post method or Inertia request ?
        if (
            in_array($request->method(), ['POST', 'PUT', 'PATCH'], true) and
            ($request->headers->has('X-Inertia') && $request->headers->get('X-Inertia') === 'true')
        ) {
            // 1. Request Locale
            $requestLocale = $request->locale ?? config('app.fallback_locale');
            // 2. If prefix is not in supportedLocales
            if (!in_array($requestLocale, LaravelLocalization::getSupportedLanguagesKeys(), true)) {
                throw ValidationException::withMessages(["Langue" => "Not supported locale."]);
            }
            // 3. Set new locale if locale and prefix are not the same
            if ($requestLocale !== app()->getLocale()) {
                $this->changeLang($requestLocale);
            }
        }

        return $next($request);
    }

    /**
     * Change lang function
     *
     * @param string $lang
     * @return void
     */
    private function changeLang(string $lang): void
    {
        Session::put('lang', $lang);
        app()->setLocale($lang);
    }
}