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) : void {
        $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');
    }

}