<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpKernel\Event\RequestEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
use function Symfony\Component\String\u;

/**
 * When visiting the homepage, this listener redirects the user to the most
 * appropriate localized version according to the browser settings.
 *
 * See https://symfony.com/doc/current/components/http_kernel.html#the-kernel-request-event
 *
 * @author Oleg Voronkovich <oleg-voronkovich@yandex.ru>
 */
class RedirectToPreferredLocaleSubscriber implements EventSubscriberInterface
{
    private $urlGenerator;
    private $locales;
    private $defaultLocale;

    public function __construct(UrlGeneratorInterface $urlGenerator, string $locales, string $defaultLocale = null)
    {
        $this->urlGenerator = $urlGenerator;

        $this->locales = explode('|', trim($locales));
        if (empty($this->locales)) {
            throw new \UnexpectedValueException('The list of supported locales must not be empty.');
        }

        $this->defaultLocale = $defaultLocale ?: $this->locales[0];

        if (!\in_array($this->defaultLocale, $this->locales, true)) {
            throw new \UnexpectedValueException(sprintf('The default locale ("%s") must be one of "%s".', $this->defaultLocale, $locales));
        }

        // Add the default locale at the first position of the array,
        // because Symfony\HttpFoundation\Request::getPreferredLanguage
        // returns the first element when no an appropriate language is found
        array_unshift($this->locales, $this->defaultLocale);
        $this->locales = array_unique($this->locales);
    }

    public static function getSubscribedEvents(): array
    {
        return [
            KernelEvents::REQUEST => 'onKernelRequest',
        ];
    }

    public function onKernelRequest(RequestEvent $event): void
    {
        $request = $event->getRequest();

        // Ignore sub-requests and all URLs but the homepage
        if (!$event->isMainRequest() || '/' !== $request->getPathInfo()) {
            return;
        }
        // Ignore requests from referrers with the same HTTP host in order to prevent
        // changing language for users who possibly already selected it for this application.
        $referrer = $request->headers->get('referer');
        if (null !== $referrer && u($referrer)->ignoreCase()->startsWith($request->getSchemeAndHttpHost())) {
            return;
        }

        $preferredLanguage = $request->getPreferredLanguage($this->locales);

        if ($preferredLanguage !== $this->defaultLocale) {
            $response = new RedirectResponse($this->urlGenerator->generate('homepage', ['_locale' => $preferredLanguage]));
            $event->setResponse($response);
        }
    }
}