hk-bus-eta/src/lightRail.ts

Query the ETA (Estimated Time of Arrival) of HK Bus/Minibus/MTR/Lightrail

import type { Eta, RouteListEntry } from "./type";
import { isSafari } from "./utils";

interface fetchEtasProps {
  route: RouteListEntry["route"];
  dest: RouteListEntry["dest"];
  stopId: string;
}

export default function fetchEtas({
  stopId,
  route,
  dest,
}: fetchEtasProps): Promise<Eta[]> {
  return fetch(
    `https://rt.data.gov.hk/v1/transport/mtr/lrt/getSchedule?station_id=${stopId.slice(
      2,
    )}`,
    {
      cache: isSafari ? "default" : "no-store",
    },
  )
    .then((response) => response.json())
    .then(({ platform_list }) => {
      if (
        platform_list.every(({ end_service_status }: any) => end_service_status)
      ) {
        return [
          {
            eta: null,
            remark: {
              zh: "此站今日服務已經終止",
              en: "This stop's service for today has ended",
            },
            dest: {
              zh: "",
              en: "",
            },
            co: "lightRail",
          },
        ];
      }
      // How should `end_service_status` for only some platforms be handled? Would a light rail line stop at different platforms?
      return platform_list.reduce(
        (acc: Eta[], { route_list, platform_id }: any) => {
          return [
            ...acc,
            // route_list is null when there are no ETAs available
            ...(route_list ?? [])
              .filter(
                ({ route_no, dest_ch, dest_en, stop }: any) =>
                  route === route_no &&
                  (dest_ch === dest.zh || dest_en.includes("Circular")) &&
                  stop === 0,
              )
              .map(({ time_en, train_length }: any) => {
                let waitTime = 0;
                switch (time_en.toLowerCase()) {
                  case "arriving":
                  case "departing":
                  case "-":
                    waitTime = 0;
                    break;
                  default:
                    waitTime = parseInt(time_en, 10);
                    break;
                }
                const etaDate = new Date(
                  Date.now() + waitTime * 60 * 1000 + 8 * 3600000,
                );
                return {
                  eta:
                    `${etaDate.getUTCFullYear()}-${`0${
                      etaDate.getUTCMonth() + 1
                    }`.slice(-2)}-${`0${etaDate.getUTCDate()}`.slice(-2)}` +
                    `T${`0${etaDate.getUTCHours()}`.slice(
                      -2,
                    )}:${`0${etaDate.getMinutes()}`.slice(
                      -2,
                    )}:${`0${etaDate.getSeconds()}`.slice(-2)}+08:00`,
                  remark: {
                    zh: `${platform_id}號月台 - ${Array(train_length)
                      .fill("▭")
                      .join("")}`,
                    en: `Platform ${platform_id} - ${Array(train_length)
                      .fill("▭")
                      .join("")}`,
                  },
                  dest: {
                    zh: "",
                    en: "",
                  },
                  co: "lightRail",
                };
              }, []),
          ];
        },
        []
      );
    })
    .catch((e) => {
      console.error(e);
      return [];
    });
}