class Comment

class Comment extends DrupalSqlBase {
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        $query = $this->select('comments', 'c')
            ->fields('c', [
            'cid',
            'pid',
            'nid',
            'uid',
            'subject',
            'comment',
            'hostname',
            'timestamp',
            'status',
            'thread',
            'name',
            'mail',
            'homepage',
            'format',
        ]);
        $query->innerJoin('node', 'n', 'c.nid = n.nid');
        $query->fields('n', [
            'type',
            'language',
        ]);
        $query->orderBy('c.timestamp');
        return $query;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareRow(Row $row) {
        // @todo Remove the call to ->prepareComment() in
        // https://www.drupal.org/project/drupal/issues/3069260 when the Drupal 9
        // branch opens.
        return parent::prepareRow($this->prepareComment($row));
    }
    
    /**
     * Provides a BC layer for deprecated sources.
     *
     * This is a backward compatibility layer for the deprecated migrate source
     * plugins d6_comment_variable and d6_comment_variable_per_comment_type.
     *
     * @param \Drupal\migrate\Row $row
     *   The row from the source to process.
     *
     * @return \Drupal\migrate\Row
     *   The row object.
     *
     * @throws \Exception
     *   Passing a Row with a frozen source to this method will trigger an
     *   \Exception when attempting to set the source properties.
     *
     * @todo Remove usages of this method and deprecate for removal in
     *   https://www.drupal.org/project/drupal/issues/3069260 when the Drupal 9
     *   branch opens.
     */
    protected function prepareComment(Row $row) {
        if ($this->variableGet('comment_subject_field_' . $row->getSourceProperty('type'), 1)) {
            // Comment subject visible.
            $row->setSourceProperty('field_name', 'comment');
            $row->setSourceProperty('comment_type', 'comment');
        }
        else {
            $row->setSourceProperty('field_name', 'comment_no_subject');
            $row->setSourceProperty('comment_type', 'comment_no_subject');
        }
        // In D6, status=0 means published, while in D8 means the opposite.
        // See https://www.drupal.org/node/237636.
        $row->setSourceProperty('status', !$row->getSourceProperty('status'));
        // If node did not have a language, use site default language as a fallback.
        if (!$row->getSourceProperty('language')) {
            $language_default = $this->variableGet('language_default', NULL);
            $language = $language_default ? $language_default->language : 'en';
            $row->setSourceProperty('language', $language);
        }
        return $row;
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        return [
            'cid' => $this->t('Comment ID.'),
            'pid' => $this->t('Parent comment ID. If set to 0, this comment is not a reply to an existing comment.'),
            'nid' => $this->t('The {node}.nid to which this comment is a reply.'),
            'uid' => $this->t('The {users}.uid who authored the comment. If set to 0, this comment was created by an anonymous user.'),
            'subject' => $this->t('The comment title.'),
            'comment' => $this->t('The comment body.'),
            'hostname' => $this->t("The author's host name."),
            'timestamp' => $this->t('The time that the comment was created, or last edited by its author, as a Unix timestamp.'),
            'status' => $this->t('The published status of a comment. (0 = Published, 1 = Not Published)'),
            'format' => $this->t('The {filter_formats}.format of the comment body.'),
            'thread' => $this->t("The vancode representation of the comment's place in a thread."),
            'name' => $this->t("The comment author's name. Uses {users}.name if the user is logged in, otherwise uses the value typed into the comment form."),
            'mail' => $this->t("The comment author's email address from the comment form, if user is anonymous, and the 'Anonymous users may/must leave their contact information' setting is turned on."),
            'homepage' => $this->t("The comment author's home page address from the comment form, if user is anonymous, and the 'Anonymous users may/must leave their contact information' setting is turned on."),
            'type' => $this->t("The {node}.type to which this comment is a reply."),
            'language' => $this->t("The {node}.language to which this comment is a reply. Site default language is used as a fallback if node does not have a language."),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['cid']['type'] = 'integer';
        return $ids;
    }

}