CommentStorage::getNewCommentPageNumber

public CommentStorage::getNewCommentPageNumber($total_comments, $new_comments, FieldableEntityInterface $entity, $field_name)

public function getNewCommentPageNumber($total_comments, $new_comments, FieldableEntityInterface $entity, $field_name) {
  $field = $entity->getFieldDefinition($field_name);
  $comments_per_page = $field->getSetting('per_page');

  if ($total_comments <= $comments_per_page) {
    // Only one page of comments.
    $count = 0;
  }
  elseif ($field->getSetting('default_mode') == CommentManagerInterface::COMMENT_MODE_FLAT) {
    // Flat comments.
    $count = $total_comments - $new_comments;
  }
  else {
    // Threaded comments.

    // 1. Find all the threads with a new comment.
    $unread_threads_query = $this->database->select('comment_field_data', 'comment')
      ->fields('comment', array('thread'))
      ->condition('entity_id', $entity->id())
      ->condition('entity_type', $entity->getEntityTypeId())
      ->condition('field_name', $field_name)
      ->condition('status', CommentInterface::PUBLISHED)
      ->condition('default_langcode', 1)
      ->orderBy('created', 'DESC')
      ->orderBy('cid', 'DESC')
      ->range(0, $new_comments);

    // 2. Find the first thread.
    $first_thread_query = $this->database->select($unread_threads_query, 'thread');
    $first_thread_query->addExpression('SUBSTRING(thread, 1, (LENGTH(thread) - 1))', 'torder');
    $first_thread = $first_thread_query
    ->fields('thread', array('thread'))
      ->orderBy('torder')
      ->range(0, 1)
      ->execute()
      ->fetchField();

    // Remove the final '/'.
    $first_thread = substr($first_thread, 0, -1);

    // Find the number of the first comment of the first unread thread.
    $count = $this->database->query('SELECT COUNT(*) FROM {comment_field_data} WHERE entity_id = :entity_id
                        AND entity_type = :entity_type
                        AND field_name = :field_name
                        AND status = :status
                        AND SUBSTRING(thread, 1, (LENGTH(thread) - 1)) < :thread
                        AND default_langcode = 1', array(
      ':status' => CommentInterface::PUBLISHED,
      ':entity_id' => $entity->id(),
      ':field_name' => $field_name,
      ':entity_type' => $entity->getEntityTypeId(),
      ':thread' => $first_thread,
    ))->fetchField();
  }

  return $comments_per_page > 0 ? (int) ($count / $comments_per_page) : 0;
}