slow-zone/dist/index.js

A client & wrapper for CTA 'L' arrival data

import { readFileSync } from "node:fs";
import { request } from "node:https";
import { parseTrain } from "./parsers/train.js";
const API_BASE_URL = "lapi.transitchicago.com";
const API_BASE_PATH = "/api/1.0";
export const VERSION = JSON.parse(readFileSync(new URL("../package.json", import.meta.url), "utf-8")).version;
export default class SlowZone {
    constructor(options) {
        this.apiKey = options.apiKey;
    }
    getArrivalsForStation(stationId, options = {}) {
        return this.getArrivals({ ...options, mapid: stationId });
    }
    getArrivalsForStop(stopId, options = {}) {
        return this.getArrivals({ ...options, stpid: stopId });
    }
    followTrain(runId) {
        return this.fetch("ttfollow.aspx", { runnumber: runId });
    }
    getArrivals(options = {}) {
        return this.fetch("ttarrivals.aspx", options);
    }
    async fetch(endpoint, queryParams = {}) {
        const resp = await this.makeRequest(endpoint, queryParams);
        if (!resp) {
            throw new Error("invalid response");
        }
        if (resp.ctatt.errCd != "0") {
            throw new Error(`[${resp.ctatt.errCd}] ${resp.ctatt.errNm}`);
        }
        return resp.ctatt.eta.map((trainData) => parseTrain(trainData));
    }
    async makeRequest(endpoint, queryParams = {}) {
        const query = new URLSearchParams({
            ...queryParams,
            key: this.apiKey,
            outputType: "json",
        });
        const options = {
            hostname: API_BASE_URL,
            port: 443,
            path: `${API_BASE_PATH}/${endpoint}?${query.toString()}`,
            method: "GET",
            headers: {
                Accept: "application/json",
                "User-Agent": `slow-zone/${VERSION}`,
            },
        };
        return new Promise(function (resolve, reject) {
            const req = request(options, (res) => {
                if (res.statusCode && (res.statusCode < 200 || res.statusCode >= 300)) {
                    return reject(new Error(res.statusCode.toString()));
                }
                const body = [];
                let json;
                res.on("data", (chunk) => {
                    body.push(chunk);
                });
                res.on("end", () => {
                    try {
                        json = JSON.parse(Buffer.concat(body).toString());
                    }
                    catch (e) {
                        return reject(e);
                    }
                    return resolve(json);
                });
            });
            req.on("error", (err) => {
                return reject(err);
            });
            req.end();
        });
    }
}