class CommentNameConstraintValidator

class CommentNameConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
  
  /**
   * User storage handler.
   *
   * @var \Drupal\user\UserStorageInterface
   */
  protected $userStorage;
  
  /**
   * Constructs a new CommentNameConstraintValidator.
   *
   * @param \Drupal\user\UserStorageInterface $user_storage
   *   The user storage handler.
   */
  public function __construct(UserStorageInterface $user_storage) {
    $this->userStorage = $user_storage;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('entity_type.manager')
      ->getStorage('user'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function validate($entity, Constraint $constraint) {
    $author_name = $entity->name->value;
    $owner_id = (int) $entity->uid->target_id;
    // Do not allow unauthenticated comment authors to use a name that is
    // taken by a registered user.
    if (isset($author_name) && $author_name !== '' && $owner_id === 0) {
      $users = $this->userStorage
        ->loadByProperties([
        'name' => $author_name,
      ]);
      if (!empty($users)) {
        $this->context
          ->buildViolation($constraint->messageNameTaken, [
          '%name' => $author_name,
        ])
          ->atPath('name')
          ->addViolation();
      }
    }
    elseif (isset($author_name) && $author_name !== '' && $owner_id) {
      $owner = $this->userStorage
        ->load($owner_id);
      if ($owner->getAccountName() != $author_name) {
        $this->context
          ->buildViolation($constraint->messageMatch)
          ->atPath('name')
          ->addViolation();
      }
    }
    // Anonymous account might be required - depending on field settings. We
    // can't validate this without a valid commented entity, which will fail
    // the validation elsewhere.
    if ($owner_id === 0 && empty($author_name) && $entity->getCommentedEntity() && $entity->getFieldName() && $this->getAnonymousContactDetailsSetting($entity) === CommentInterface::ANONYMOUS_MUST_CONTACT) {
      $this->context
        ->buildViolation($constraint->messageRequired)
        ->atPath('name')
        ->addViolation();
    }
  }
  
  /**
   * Gets the anonymous contact details setting from the comment.
   *
   * @param \Drupal\comment\CommentInterface $comment
   *   The entity.
   *
   * @return int
   *   The anonymous contact setting.
   */
  protected function getAnonymousContactDetailsSetting(CommentInterface $comment) {
    return $comment->getCommentedEntity()
      ->get($comment->getFieldName())
      ->getFieldDefinition()
      ->getSetting('anonymous');
  }

}