minotor/src/gtfs/routes.ts

A lightweight client-side transit routing library.

import log from 'loglevel';

import {
  RouteType,
  ServiceRoute,
  ServiceRouteId,
} from '../timetable/timetable.js';
import { GtfsProfile } from './parser.js';
import { standardGtfsProfile } from './profiles/standard.js';
import { parseCsv } from './utils.js';

// Can be a standard gtfs route type or an extended route type
// the profile converter handles the conversion to a route type.
export type GtfsRouteType = number;
export type GtfsRouteId = string;

export type GtfsRoutesMap = Map<
  GtfsRouteId,
  {
    name: string;
    type: RouteType;
  }
>;

type RouteEntry = {
  route_id: GtfsRouteId;
  agency_id: string;
  route_short_name: string;
  route_long_name: string;
  route_desc: string;
  route_type: number;
};

/**
 * Parses a GTFS routes.txt file and returns a map of all the valid routes.
 *
 * @param routesStream A readable stream for the GTFS routes.txt file.
 * @param profile A configuration object defining the specificities of the GTFS feed.
 * @returns A map of all the valid routes.
 */
export const parseRoutes = async (
  routesStream: NodeJS.ReadableStream,
  profile: GtfsProfile = standardGtfsProfile,
): Promise<GtfsRoutesMap> => {
  const routes: GtfsRoutesMap = new Map();
  for await (const rawLine of parseCsv(routesStream, ['route_type'])) {
    const line = rawLine as RouteEntry;
    const routeType = profile.routeTypeParser(line.route_type);
    if (routeType === undefined) {
      log.info(
        `Unsupported route type ${line.route_type} for route ${line.route_id}.`,
      );
      continue;
    }
    routes.set(line.route_id, {
      name: line.route_short_name,
      type: routeType,
    });
  }
  return routes;
};

/**
 * Creates an array of ServiceRoute objects by combining GTFS route data with service route mappings.
 *
 * @param gtfsRoutesMap A map containing GTFS route information indexed by route ID
 * @param serviceRoutesMap A map linking GTFS route IDs to service route IDs
 * @returns An array of ServiceRoute objects with route information
 */
export const indexRoutes = (
  gtfsRoutesMap: GtfsRoutesMap,
  serviceRoutesMap: Map<GtfsRouteId, ServiceRouteId>,
): ServiceRoute[] => {
  const serviceRoutes: ServiceRoute[] = new Array<ServiceRoute>(
    serviceRoutesMap.size,
  );
  for (const [gtfsRouteId, serviceRouteId] of serviceRoutesMap) {
    const route = gtfsRoutesMap.get(gtfsRouteId);
    if (route === undefined) {
      log.warn(`Route ${gtfsRouteId} not found.`);
      continue;
    }
    serviceRoutes[serviceRouteId] = {
      name: route.name,
      type: route.type,
      routes: [],
    };
  }
  return serviceRoutes;
};