class SessionExistsCacheContext

class SessionExistsCacheContext implements CacheContextInterface {
  
  /**
   * The session configuration.
   *
   * @var \Drupal\Core\Session\SessionConfigurationInterface
   */
  protected $sessionConfiguration;
  
  /**
   * The request stack.
   *
   * @var \Symfony\Component\HttpFoundation\RequestStack
   */
  protected $requestStack;
  
  /**
   * Constructs a new SessionExistsCacheContext class.
   *
   * @param \Drupal\Core\Session\SessionConfigurationInterface $session_configuration
   *   The session configuration.
   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
   *   The request stack.
   */
  public function __construct(SessionConfigurationInterface $session_configuration, RequestStack $request_stack) {
    $this->sessionConfiguration = $session_configuration;
    $this->requestStack = $request_stack;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function getLabel() {
    return t('Session exists');
  }
  
  /**
   * {@inheritdoc}
   */
  public function getContext() {
    return $this->sessionConfiguration
      ->hasSession($this->requestStack
      ->getCurrentRequest()) ? '1' : '0';
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCacheableMetadata() {
    return new CacheableMetadata();
  }

}