<?php

namespace App\EventSubscriber;

use App\Ops\Updater;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Event\RequestEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Twig\Environment;

/**
 * While an update runs, the website answers with 503 and the administration stays open.
 *
 * 503 and not 200 with a notice: a search engine reads 503 with Retry-After as "come back later"
 * and keeps the page in its index, while a 200 would teach it that the page now contains an
 * excuse. The administration has to stay reachable, because otherwise nobody could finish or
 * undo the update.
 */
final class MaintenanceSubscriber implements EventSubscriberInterface
{
    public function __construct(private Environment $twig, private string $projectDir, private string $adminPath)
    {
    }

    public static function getSubscribedEvents(): array
    {
        // Before the router: during maintenance no controller should run at all.
        return [KernelEvents::REQUEST => ['onRequest', 40]];
    }

    public function onRequest(RequestEvent $event): void
    {
        if (!$event->isMainRequest() || !is_file($this->projectDir.'/'.Updater::MAINTENANCE_FILE)) {
            return;
        }
        $path = $event->getRequest()->getPathInfo();
        if (preg_match('#^/('.preg_quote($this->adminPath, '#').'|assets/|media/|favicon)#', $path)) {
            return;
        }
        $since = @file_get_contents($this->projectDir.'/'.Updater::MAINTENANCE_FILE);
        $response = new Response(
            $this->twig->render('maintenance.html.twig', ['since' => trim((string) $since)]),
            Response::HTTP_SERVICE_UNAVAILABLE,
            [
                'Retry-After' => '600',
                'Cache-Control' => 'no-store',
                'Content-Type' => 'text/html; charset=UTF-8',
                'Content-Security-Policy' => "default-src 'self'; script-src 'none'; style-src 'self'; img-src 'self'; object-src 'none'; base-uri 'none'; frame-ancestors 'none'",
            ],
        );
        $event->setResponse($response);
    }
}