<?php

namespace Drupal\Core\EventSubscriber;

use Drupal\Component\Render\FormattableMarkup;
use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Core\Render\BareHtmlPageRendererInterface;
use Drupal\Core\Messenger\MessengerInterface;
use Drupal\Core\Routing\RouteMatch;
use Drupal\Core\Routing\UrlGeneratorInterface;
use Drupal\Core\Session\AccountInterface;
use Drupal\Core\Site\MaintenanceModeInterface;
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Drupal\Core\StringTranslation\TranslationInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Maintenance mode subscriber for controller requests.
 */
class MaintenanceModeSubscriber implements EventSubscriberInterface {

  use StringTranslationTrait;

  /**
   * The maintenance mode.
   *
   * @var \Drupal\Core\Site\MaintenanceModeInterface
   */
  protected $maintenanceMode;

  /**
   * The current account.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $account;

  /**
   * The config factory.
   *
   * @var \Drupal\Core\Config\ConfigFactoryInterface
   */
  protected $config;

  /**
   * The url generator.
   *
   * @var \Drupal\Core\Routing\UrlGeneratorInterface
   */
  protected $urlGenerator;

  /**
   * The bare HTML page renderer.
   *
   * @var \Drupal\Core\Render\BareHtmlPageRendererInterface
   */
  protected $bareHtmlPageRenderer;

  /**
   * The messenger.
   *
   * @var \Drupal\Core\Messenger\MessengerInterface
   */
  protected $messenger;

  /**
   * Constructs a new MaintenanceModeSubscriber.
   *
   * @param \Drupal\Core\Site\MaintenanceModeInterface $maintenance_mode
   *   The maintenance mode.
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory.
   * @param \Drupal\Core\StringTranslation\TranslationInterface $translation
   *   The string translation.
   * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
   *   The url generator.
   * @param \Drupal\Core\Session\AccountInterface $account
   *   The current user.
   * @param \Drupal\Core\Render\BareHtmlPageRendererInterface $bare_html_page_renderer
   *   The bare HTML page renderer.
   * @param \Drupal\Core\Messenger\MessengerInterface $messenger
   *   The messenger.
   */
  public function __construct(MaintenanceModeInterface $maintenance_mode, ConfigFactoryInterface $config_factory, TranslationInterface $translation, UrlGeneratorInterface $url_generator, AccountInterface $account, BareHtmlPageRendererInterface $bare_html_page_renderer, MessengerInterface $messenger) {
    $this->maintenanceMode = $maintenance_mode;
    $this->config = $config_factory;
    $this->stringTranslation = $translation;
    $this->urlGenerator = $url_generator;
    $this->account = $account;
    $this->bareHtmlPageRenderer = $bare_html_page_renderer;
    $this->messenger = $messenger;
  }

  /**
   * Returns the site maintenance page if the site is offline.
   *
   * @param \Symfony\Component\HttpKernel\Event\GetResponseEvent $event
   *   The event to process.
   */
  public function onKernelRequestMaintenance(GetResponseEvent $event) {
    $request = $event->getRequest();
    $route_match = RouteMatch::createFromRequest($request);
    if ($this->maintenanceMode->applies($route_match)) {
      // Don't cache maintenance mode pages.
      \Drupal::service('page_cache_kill_switch')->trigger();

      if (!$this->maintenanceMode->exempt($this->account)) {
        // Deliver the 503 page if the site is in maintenance mode and the
        // logged in user is not allowed to bypass it.

        // If the request format is not 'html' then show default maintenance
        // mode page else show a text/plain page with maintenance message.
        if ($request->getRequestFormat() !== 'html') {
          $response = new Response($this->getSiteMaintenanceMessage(), 503, ['Content-Type' => 'text/plain']);
          $event->setResponse($response);
          return;
        }
        drupal_maintenance_theme();
        $response = $this->bareHtmlPageRenderer->renderBarePage(['#markup' => $this->getSiteMaintenanceMessage()], $this->t('Site under maintenance'), 'maintenance_page');
        $response->setStatusCode(503);
        $event->setResponse($response);
      }
      else {
        // Display a message if the logged in user has access to the site in
        // maintenance mode. However, suppress it on the maintenance mode
        // settings page.
        if ($route_match->getRouteName() != 'system.site_maintenance_mode') {
          if ($this->account->hasPermission('administer site configuration')) {
            $this->messenger->addMessage($this->t('Operating in maintenance mode. <a href=":url">Go online.</a>', [':url' => $this->urlGenerator->generate('system.site_maintenance_mode')]), 'status', FALSE);
          }
          else {
            $this->messenger->addMessage($this->t('Operating in maintenance mode.'), 'status', FALSE);
          }
        }
      }
    }
  }

  /**
   * Gets the site maintenance message.
   *
   * @return \Drupal\Component\Render\MarkupInterface
   *   The formatted site maintenance message.
   */
  protected function getSiteMaintenanceMessage() {
    return new FormattableMarkup($this->config->get('system.maintenance')->get('message'), [
      '@site' => $this->config->get('system.site')->get('name'),
    ]);
  }

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {
    $events[KernelEvents::REQUEST][] = ['onKernelRequestMaintenance', 30];
    $events[KernelEvents::EXCEPTION][] = ['onKernelRequestMaintenance'];
    return $events;
  }

}
