bbp_buddypress_add_topic_notification( int $topic_id, int $forum_id )

function bbp_buddypress_add_topic_notification( $topic_id, $forum_id ) {
	// If our temporary variable doesn't exist, stop now.
	if ( empty( buddypress()->forums->mentioned_users ) ) {
		return;
	}

	// Get some topic information
	$args = array(
		'item_id'           => $topic_id,
		'secondary_item_id' => get_current_user_id(),
		'component_name'    => bbp_get_component_name(),
		'component_action'  => 'bbp_new_at_mention',
	);

	// Grab our temporary variable from bbp_convert_mentions().
	$usernames = buddypress()->forums->mentioned_users;

	// Get rid of temporary variable.
	unset( buddypress()->forums->mentioned_users );

	// We have mentions!
	if ( ! empty( $usernames ) ) {
		// Send @mentions and setup BP notifications.
		foreach ( (array) $usernames as $user_id => $username ) {

			// Current user is the same user then do not send notification.
			if ( $user_id === get_current_user_id() ) {
				continue;
			}

			$args['user_id']          = $user_id;

			// If forum is not accesible to user, do not send notification.
			$can_access = bbp_user_can_view_forum( array( 'user_id' => $user_id, 'forum_id' => $forum_id, 'check_ancestors' => true ) );

			/**
			 * Filters bbPress' ability to send notifications for @mentions.
			 *
			 * @param bool $value Whether or not BuddyPress should send a notification to the mentioned users.
			 * @param array $usernames Array of users potentially notified.
			 * @param int $user_id ID of the current user being notified.
			 * @param int $forum_id ID of forum.
			 *
			 * @since BuddyBoss 1.2.9
			 *
			 */
			if ( ! apply_filters( 'bbp_forums_at_name_do_notifications', $can_access, $usernames, $user_id, $forum_id ) ) {
				continue;
			}

			bp_notifications_add_notification( $args );
		}
	}
}