class AccessDeniedSubscriber

class AccessDeniedSubscriber extends HttpExceptionSubscriberBase {
  
  /**
   * The current user.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $account;
  
  /**
   * Constructs a new redirect subscriber.
   *
   * @param \Drupal\Core\Session\AccountInterface $account
   *   The current user.
   */
  public function __construct(AccountInterface $account) {
    $this->account = $account;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getHandledFormats() : array {
    return [
      'html',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  protected static function getPriority() : int {
    // Use a higher priority than ExceptionLoggingSubscriber, because there's
    // no need to log the exception if we can redirect.
    // @see Drupal\Core\EventSubscriber\ExceptionLoggingSubscriber
    return 75;
  }
  
  /**
   * Redirects users when access is denied.
   *
   * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $event
   *   The event to process.
   */
  public function on403(ExceptionEvent $event) : void {
    $route_name = RouteMatch::createFromRequest($event->getRequest())
      ->getRouteName();
    $redirect_url = NULL;
    if ($this->account
      ->isAuthenticated()) {
      switch ($route_name) {
        case 'user.login':
          // Redirect an authenticated user to the profile page.
          $redirect_url = Url::fromRoute('entity.user.canonical', [
            'user' => $this->account
              ->id(),
          ], [
            'absolute' => TRUE,
          ]);
          break;

        case 'user.register':
          // Redirect an authenticated user to the profile form.
          $redirect_url = Url::fromRoute('entity.user.edit_form', [
            'user' => $this->account
              ->id(),
          ], [
            'absolute' => TRUE,
          ]);
          break;

      }
    }
    elseif ($route_name === 'user.page') {
      $redirect_url = Url::fromRoute('user.login', [], [
        'absolute' => TRUE,
      ]);
    }
    elseif (in_array($route_name, [
      'user.logout',
      'user.logout.confirm',
    ], TRUE)) {
      $redirect_url = Url::fromRoute('<front>', [], [
        'absolute' => TRUE,
      ]);
    }
    if ($redirect_url) {
      $event->setResponse(new RedirectResponse($redirect_url->toString()));
    }
  }

}