hk-bus-eta/esm/journeyTime.js

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

import { formatInTimeZone } from "date-fns-tz";
const __HK_BUS_ETA_JT_CACHE__ = {};
async function fetchEstJourneyTimeBasedOnHistoricalData({ route, startSeq, endSeq, }) {
    const requests = [];
    const stops = Object.values(route.stops)[0];
    for (let i = startSeq; i < endSeq; ++i) {
        const start = stops[i];
        const end = stops[i + 1];
        const day = parseInt(formatInTimeZone(new Date(), "Asia/Hong_Kong", "i"), 10) - 1;
        const hour = formatInTimeZone(new Date(), "Asia/Hong_Kong", "HH");
        requests.push(fetch(`https://raw.githubusercontent.com/HK-Bus-ETA/hk-bus-time-between-stops/refs/heads/pages/times_hourly/${day}/${hour}/${start.slice(0, 2)}.json`)
            .then((r) => r.json())
            .then((r) => {
            if (r[start][end]) {
                return r[start][end];
            }
            throw new Error("not found");
        }));
    }
    return Promise.all(requests).then((seconds) => Math.ceil(seconds.reduce((acc, cur) => acc + cur, 0) / 60));
}
async function fetchEstJourneyTimeBasedOnHistoricalAvgData({ route, startSeq, endSeq, }) {
    const requests = [];
    const stops = Object.values(route.stops)[0];
    for (let i = startSeq; i < endSeq; ++i) {
        const start = stops[i];
        const end = stops[i + 1];
        requests.push(fetch(`https://raw.githubusercontent.com/HK-Bus-ETA/hk-bus-time-between-stops/refs/heads/pages/times/${start.slice(0, 2)}.json`)
            .then((r) => r.json())
            .then((r) => {
            if (r[start][end]) {
                return r[start][end];
            }
            throw new Error("not found");
        }));
    }
    return Promise.all(requests).then((seconds) => Math.ceil(seconds.reduce((acc, cur) => acc + cur, 0) / 60));
}
/**
 * Fetch Journey time in minute for a route
 * @param {Object}
 * @returns {number} journey time in minute
 */
export async function fetchEstJourneyTime({ route, stopList, startSeq, endSeq, batchSize = 4, signal, }) {
    const stops = Object.values(route.stops)[0];
    if (!["kmb", "nlb", "ctb", "lrtfeeder", "gmb"].includes(Object.keys(route.stops)[0]))
        throw new Error("Support vehicle transport only");
    if (startSeq < 0)
        throw new Error("startSeq should be ≥ 0");
    if (endSeq >= stops.length)
        throw new Error("endSeq should be < number of stops");
    if (startSeq >= endSeq)
        throw new Error("startSeq should be < endSeq");
    let ts = Date.now();
    let ret = 0;
    let payloads = [];
    for (let i = startSeq; i < endSeq; ++i) {
        payloads.push([
            `${stops[i]}-${stops[i + 1]}`,
            JSON.stringify({
                start: {
                    lat: stopList[stops[i]].location.lat,
                    long: stopList[stops[i]].location.lng,
                },
                end: {
                    lat: stopList[stops[i + 1]].location.lat,
                    long: stopList[stops[i + 1]].location.lng,
                },
                departIn: Math.round(ret / 15) * 15,
            }),
            {
                startSeq: i,
                endSeq: i + 1,
            },
        ]);
        if (payloads.length < batchSize && i !== endSeq - 1) {
            // skip fetching until whole batch filled
            continue;
        }
        const seconds = await Promise.all(payloads.map(([key, payload, { startSeq, endSeq }]) => {
            // load from cache if it is query within 15 minutes
            if (key in __HK_BUS_ETA_JT_CACHE__ &&
                __HK_BUS_ETA_JT_CACHE__[key].ts + 15 * 60 * 1000 >= ts) {
                return Promise.resolve(__HK_BUS_ETA_JT_CACHE__[key].s);
            }
            return fetchEstJourneyTimeBasedOnHistoricalData({
                route,
                startSeq,
                endSeq,
            })
                .catch(() => fetchEstJourneyTimeBasedOnHistoricalAvgData({
                route,
                startSeq,
                endSeq,
            }))
                .catch(() => fetch("https://tdas-api.hkemobility.gov.hk/tdas/api/route", {
                method: "POST",
                headers: {
                    "Content-Type": "application/json",
                },
                body: payload,
                signal,
            })
                .then((r) => r.json())
                .then(({ eta, distM, jSpeed }) => {
                var _a;
                const speedStr = (_a = /(\d+)公里\/小時/g.exec(jSpeed)) === null || _a === void 0 ? void 0 : _a[1];
                if (speedStr !== null &&
                    speedStr !== undefined &&
                    !isNaN(parseInt(speedStr, 10))) {
                    // Set the speed limit as 70 km/h
                    return ((distM / Math.min(parseInt(speedStr, 10), 70) / 1000) * 60);
                }
                console.warn("Unable to parse TDAS response for more precise journey time. Falling back.");
                const [hh, mm] = eta
                    .split(":")
                    .map((v) => parseInt(v, 10));
                return hh * 60 + mm;
            })
                .catch(() => {
                //  for any error, assume 4 minutes journey time blindly
                return 4;
            })
                .then((s) => {
                __HK_BUS_ETA_JT_CACHE__[key] = { s: s * 1.1, ts };
                // margin for car accelerating, decelerating, and passenger picking up and dropping off
                return s * 1.1;
            }));
        }));
        seconds.forEach((s) => {
            ret += s;
        });
        payloads.length = 0;
    }
    for (const k in __HK_BUS_ETA_JT_CACHE__) {
        // clean up cache
        if (__HK_BUS_ETA_JT_CACHE__[k].ts + 15 * 60 * 1000 < ts) {
            delete __HK_BUS_ETA_JT_CACHE__[k];
        }
    }
    return ret;
}
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