bp_nouveau_activity_scope_newest_class( $classes = '' )

function bp_nouveau_activity_scope_newest_class( $classes = '' ) {
	if ( ! is_user_logged_in() ) {
		return $classes;
	}

	$user_id    = bp_loggedin_user_id();
	$my_classes = array();

	/*
	 * HeartBeat requests will transport the scope.
	 * See bp_nouveau_ajax_querystring().
	 */
	$scope = '';

	if ( ! empty( $_POST['data']['bp_heartbeat']['scope'] ) ) {
		$scope = sanitize_key( $_POST['data']['bp_heartbeat']['scope'] );
	}

	// Add specific classes to perform specific actions on the client side.
	if ( $scope && bp_is_activity_directory() ) {
		$component = bp_get_activity_object_name();

		/*
		 * These classes will be used to count the number of newest activities for
		 * the 'Mentions', 'My Groups' & 'My Connections' tabs
		 */
		if ( 'all' === $scope ) {
			if ( 'groups' === $component && bp_is_active( $component ) ) {
				// Is the current user a member of the group the activity is attached to?
				if ( groups_is_user_member( $user_id, bp_get_activity_item_id() ) ) {
					$my_classes[] = 'bp-my-groups';
				}
			}

			// Connections can post in groups the user is a member of
			if ( bp_is_active( 'friends' ) && (int) $user_id !== (int) bp_get_activity_user_id() ) {
				if ( friends_check_friendship( $user_id, bp_get_activity_user_id() ) ) {
					$my_classes[] = 'bp-my-friends';
				}
			}

			// A mention can be posted by a friend within a group
			if ( true === bp_activity_do_mentions() ) {
				$new_mentions = bp_get_user_meta( $user_id, 'bp_new_mentions', true );

				// The current activity is one of the new mentions
				if ( is_array( $new_mentions ) && in_array( bp_get_activity_id(), $new_mentions ) ) {
					$my_classes[] = 'bp-my-mentions';
				}
			}

		/*
		 * This class will be used to highlight the newest activities when
		 * viewing the 'Mentions', 'My Groups' or the 'My Connections' tabs
		 */
		} elseif ( 'friends' === $scope || 'groups' === $scope || 'mentions' === $scope ) {
			$my_classes[] = 'newest_' . $scope . '_activity';
		}

		// Leave other components do their specific stuff if needed.
		/**
		 * Filters the classes to be applied to the newest activity item.
		 *
		 * Leave other components do their specific stuff if needed.
		 *
		 * @since BuddyPress 3.0.0
		 *
		 * @param array  $my_classes Array of classes to output to class attribute.
		 * @param string $scope      Current scope for the activity type.
		 */
		$my_classes = (array) apply_filters( 'bp_nouveau_activity_scope_newest_class', $my_classes, $scope );

		if ( ! empty( $my_classes ) ) {
			$classes .= ' ' . join( ' ', $my_classes );
		}
	}

	return $classes;
}