minotor/src/gtfs/stops.ts

A lightweight client-side transit routing library.

import {
  Latitude,
  LocationType,
  Longitude,
  Platform,
  SourceStopId,
  Stop,
} from '../stops/stops.js';
import { parseCsv } from './utils.js';

export type GtfsLocationType =
  | 0 // simple stop or platform (can also be empty)
  | 1 // station
  | 2 // entrance / exit
  | 3 // generic node
  | 4; // boarding area

export type StopEntry = {
  stop_id: SourceStopId;
  stop_name: string;
  stop_lat?: Latitude;
  stop_lon?: Longitude;
  location_type?: GtfsLocationType;
  parent_station?: SourceStopId;
  platform_code?: Platform;
};

type ParsedStop = Stop & {
  parentSourceId?: SourceStopId;
};

export type GtfsStopsMap = Map<SourceStopId, ParsedStop>;
/**
 * Parses the stops.txt file from a GTFS feed.
 *
 * @param stopsStream The readable stream containing the stops data.
 * @return A mapping of stop IDs to corresponding stop details.
 */
export const parseStops = async (
  stopsStream: NodeJS.ReadableStream,
): Promise<GtfsStopsMap> => {
  const parsedStops = new Map<SourceStopId, ParsedStop>();
  let i = 0;
  for await (const rawLine of parseCsv(stopsStream, [
    'stop_lat',
    'stop_lon',
    'location_type',
  ])) {
    const line = rawLine as StopEntry;
    const stop: ParsedStop = {
      id: i,
      sourceStopId: line.stop_id,
      name: line.stop_name,
      lat: line.stop_lat,
      lon: line.stop_lon,
      locationType: line.location_type
        ? parseGtfsLocationType(line.location_type)
        : 'SIMPLE_STOP_OR_PLATFORM',
      ...(line.platform_code && { platform: line.platform_code }),
      children: [],
      ...(line.parent_station && { parentSourceId: line.parent_station }),
    };
    parsedStops.set(line.stop_id, stop);
    i = i + 1;
  }

  for (const [sourceStopId, stop] of parsedStops) {
    if (stop.parentSourceId) {
      const parentStop = parsedStops.get(stop.parentSourceId);
      if (!parentStop) {
        console.warn(
          `Cannot find parent stop ${stop.parentSourceId} of ${sourceStopId}`,
        );
        continue;
      }
      stop.parent = parentStop.id;
      parentStop.children.push(stop.id);
    }
  }
  return parsedStops;
};

const parseGtfsLocationType = (
  gtfsLocationType: GtfsLocationType,
): LocationType => {
  switch (gtfsLocationType) {
    case 0:
    default:
      return 'SIMPLE_STOP_OR_PLATFORM';
    case 1:
      return 'STATION';
    case 2:
      return 'ENTRANCE_EXIT';
    case 3:
      return 'GENERIC_NODE';
    case 4:
      return 'BOARDING_AREA';
  }
};