bp_activity_at_name_filter_updates( BP_Activity_Activity $activity )

function bp_activity_at_name_filter_updates( $activity ) {
	// Are mentions disabled?
	if ( ! bp_activity_do_mentions() ) {
		return;
	}

	// If activity was marked as spam, stop the rest of this function.
	if ( ! empty( $activity->is_spam ) )
		return;

	// Try to find mentions.
	$usernames = bp_activity_find_mentions( $activity->content );

	// We have mentions!
	if ( ! empty( $usernames ) ) {
		// Replace @mention text with userlinks.
		foreach( (array) $usernames as $user_id => $username ) {
			$activity->content = preg_replace( '/(@' . $username . '\b)/', "<a class='bp-suggestions-mention' href='" . bp_core_get_user_domain( $user_id ) . "' rel='nofollow'>@$username</a>", $activity->content );
		}

		// Add our hook to send @mention emails after the activity item is saved.
		add_action( 'bp_activity_after_save', 'bp_activity_at_name_send_emails' );

		// Temporary variable to avoid having to run bp_activity_find_mentions() again.
		buddypress()->activity->mentioned_users = $usernames;
	}
}