bbp_close_topic( int $topic_id )

function bbp_close_topic( $topic_id = 0 ) {

	// Get topic
	$topic = bbp_get_topic( $topic_id );
	if ( empty( $topic ) )
		return $topic;

	// Bail if already closed
	if ( bbp_get_closed_status_id() === $topic->post_status )
		return false;

	// Execute pre close code
	do_action( 'bbp_close_topic', $topic_id );

	// Add pre close status
	add_post_meta( $topic_id, '_bbp_status', $topic->post_status );

	// Set closed status
	$topic->post_status = bbp_get_closed_status_id();

	// No revisions
	remove_action( 'pre_post_update', 'wp_save_post_revision' );

	// Update topic
	$topic_id = wp_update_post( $topic );

	// Execute post close code
	do_action( 'bbp_closed_topic', $topic_id );

	// Return topic_id
	return $topic_id;
}