class CommentType

class CommentType extends DrupalSqlBase {
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        return $this->select('node_type', 't')
            ->fields('t', [
            'type',
            'name',
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareRow(Row $row) {
        $node_type = $row->getSourceProperty('type');
        foreach (array_keys($this->getCommentFields()) as $field) {
            $row->setSourceProperty($field, $this->variableGet($field . '_' . $node_type, NULL));
        }
        return parent::prepareRow($row);
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        return [
            'name' => $this->t('Human name of the parent node type.'),
            'type' => $this->t('Machine name of the parent node type.'),
        ] + $this->getCommentFields();
    }
    
    /**
     * Returns the fields containing comment settings for each node type.
     *
     * @return string[]
     *   An associative array of field descriptions, keyed by field.
     */
    protected function getCommentFields() {
        return [
            'comment' => $this->t('Default comment setting'),
            'comment_default_mode' => $this->t('Default display mode'),
            'comment_default_per_page' => $this->t('Default comments per page'),
            'comment_anonymous' => $this->t('Anonymous commenting'),
            'comment_subject_field' => $this->t('Comment subject field'),
            'comment_preview' => $this->t('Preview comment'),
            'comment_form_location' => $this->t('Location of comment submission form'),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['type']['type'] = 'string';
        return $ids;
    }
    
    /**
     * {@inheritdoc}
     */
    public function checkRequirements() {
        parent::checkRequirements();
        if (!$this->moduleExists('node')) {
            // Drupal 6 and Drupal 7 comment configuration migrations migrate comment
            // types and comment fields for node comments only.
            throw new RequirementsException('The node module is not enabled in the source site.', [
                'source_module_additional' => 'node',
            ]);
        }
    }

}