bbp_update_topic_last_reply_id( int $topic_id, int $reply_id )

function bbp_update_topic_last_reply_id( $topic_id = 0, $reply_id = 0 ) {

	// If it's a reply, then get the parent (topic id)
	if ( empty( $reply_id ) && bbp_is_reply( $topic_id ) ) {
		$reply_id = bbp_get_reply_id( $topic_id );
		$topic_id = bbp_get_reply_topic_id( $reply_id );
	} else {
		$reply_id = bbp_get_reply_id( $reply_id );
		$topic_id = bbp_get_topic_id( $topic_id );
	}

	if ( empty( $reply_id ) ) {
		$reply_id = bbp_get_public_child_last_id( $topic_id, bbp_get_reply_post_type() );
	}

	// Adjust last_id's based on last_reply post_type
	if ( empty( $reply_id ) || !bbp_is_reply( $reply_id ) ) {
		$reply_id = 0;
	}

	// Update if reply is published
	if ( bbp_is_reply_published( $reply_id ) ) {
		update_post_meta( $topic_id, '_bbp_last_reply_id', (int) $reply_id );
	}

	return apply_filters( 'bbp_update_topic_last_reply_id', (int) $reply_id, $topic_id );
}