function bp_activity_generate_action_string( $activity ) {

	// Check for valid input.
	if ( empty( $activity->component ) || empty( $activity->type ) ) {
		return false;
	}

	// Check for registered format callback.
	$actions = bp_activity_get_actions();
	if ( empty( $actions->{$activity->component}->{$activity->type}['format_callback'] ) ) {
		return false;
	}

	// We apply the format_callback as a filter.
	add_filter( 'bp_activity_generate_action_string', $actions->{$activity->component}->{$activity->type}['format_callback'], 10, 2 );

	/**
	 * Filters the string for the activity action being returned.
	 *
	 * @since 2.0.0
	 *
	 * @param BP_Activity_Activity $action   Action string being requested.
	 * @param BP_Activity_Activity $activity Activity item object.
	 */
	$action = apply_filters( 'bp_activity_generate_action_string', $activity->action, $activity );

	// Remove the filter for future activity items.
	remove_filter( 'bp_activity_generate_action_string', $actions->{$activity->component}->{$activity->type}['format_callback'], 10 );

	return $action;
}