class MaintenanceModeSubscriber

class MaintenanceModeSubscriber implements EventSubscriberInterface {
  
  /**
   * The maintenance mode.
   *
   * @var \Drupal\Core\Site\MaintenanceMode
   */
  protected $maintenanceMode;
  
  /**
   * The current account.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $account;
  
  /**
   * The logout finalizer closure.
   */
  protected \Closure $logoutFinalizer;
  public function __construct(MaintenanceModeInterface $maintenance_mode, AccountInterface $account, #[AutowireServiceClosure(LogoutFinalizer::class)] ?\Closure $logoutFinalizer = NULL) {
    $this->maintenanceMode = $maintenance_mode;
    $this->account = $account;
    if ($logoutFinalizer === NULL) {
      @trigger_error('Calling ' . __METHOD__ . '() without the $logoutFinalizer argument is deprecated in drupal:11.5.0 and is removed from drupal:12.0.0. See https://www.drupal.org/node/3379194', E_USER_DEPRECATED);
      $logoutFinalizer = fn() => \Drupal::service(LogoutFinalizer::class);
    }
    $this->logoutFinalizer = $logoutFinalizer;
  }
  
  /**
   * Logout users if site is in maintenance mode and user is not exempt.
   *
   * @param \Symfony\Component\HttpKernel\Event\RequestEvent $event
   *   The event to process.
   */
  public function onMaintenanceModeRequest(RequestEvent $event) {
    // If the site is offline, log out unprivileged users.
    if ($this->account
      ->isAuthenticated()) {
      ($this->logoutFinalizer)()
        ->finalizeLogout();
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() : array {
    $events[MaintenanceModeEvents::MAINTENANCE_MODE_REQUEST][] = [
      'onMaintenanceModeRequest',
      -900,
    ];
    return $events;
  }

}