ldc-doux/app/Http/Middleware/LangCheck.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Cookie;
use Illuminate\Support\Facades\View;

class LangCheck
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request $request
     * @param  \Closure                 $next
     * @return mixed
     */
    public function handle(Request $request, Closure $next)
    {

        $routName = $request->route()->getName();
        if (preg_match('/^bo\./', $routName)) {
            // Back office.
            if ($request->lang) {
                // Within bo we set lang with querystring param.
                $this->saveUserLocale($request->lang, $request);
                // Bonus remove lang parameter from query.
                return redirect()->to($request->fullUrlWithoutQuery('lang'));
            } else {
                $this->checkFirstAccess($request);
            }
        } else {
            // FRONT.
            if (preg_match('/^(' . \implode("|", config('app.other_locales')) . ')\./', $routName)) {
                // From front use named routes.
                $langset = $request->segment(1);
                $this->saveUserLocale($langset, $request);
            } else {
                // Not specified in route.
                if ($this->checkFirstAccess($request)) {
                    $sess_lang = $request->session()->get('lang', config('app.locale'));
                    if ($sess_lang === config('app.locale')) {
                        return to_route($routName, $request->route()->parameters());
                    }
                    return to_route($sess_lang . '.' . $routName, $request->route()->parameters());
                }
                $this->saveUserLocale(
                    config('app.locale'),
                    $request
                );
            } //end if
        } //end if

        $sess_lang     = $request->session()->get('lang', config('app.locale'));
        $routePrefixer = "";
        if ($sess_lang != config('app.locale')) {
            $routePrefixer = $sess_lang . '.';
        }
        app()->setLocale($sess_lang);
        View::share('routeprefixer', $routePrefixer);
        return $next($request);
    }


    /**
     * Register Current user choice for language
     *
     * @param string                   $lang
     * @param \Illuminate\Http\Request $request
     *
     * @return void
     */
    private function saveUserLocale(string $lang, Request $request)
    {
        // Set cookie.
        Cookie::queue(Cookie::forever('language', strtolower($lang)));
        // Set session.
        $request->session()->put('lang', strtolower($lang));
    }

    /**
     * checks if we have saved locale info for current user
     * if not find then save that locale
     * @param \Illuminate\Http\Request $request
     *
     * @return boolean
     */
    private function checkFirstAccess(Request $request)
    {
        if (str_contains($request->header('User-Agent'), "Uptime-Kuma")) {
            return false;
        }
        // Do we have session ?
        if (!$request->session()->has('lang')) {
            $fromC = Cookie::get('language');
            if (is_null($fromC) || empty($fromC)) {
                // Pas de cookie, recherche sur le navigateur.
                $fromC = substr($request->server('HTTP_ACCEPT_LANGUAGE'), 0, 2);
                if (!in_array($fromC, config('app.other_locales'))) {
                    // Default other languages to config('app.locale').
                    $fromC = config('app.locale');
                }
            }
            $this->saveUserLocale($fromC, $request);
            return true;
        }
        // We have lang session.
        return false;
    }
}