81 lines
2.1 KiB
JavaScript
81 lines
2.1 KiB
JavaScript
const tam = require('./sources/tam');
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const util = require('../util');
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let nextUpdate = null;
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let currentCourses = null;
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/**
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* Fetch real-time information about active courses in the TaM network.
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*
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* New data will only be fetched from the TaM server once every minute,
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* otherwise pulling from the in-memory cache.
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*
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* The following information is provided for each active course:
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*
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* - `id`: Unique identifier for the course.
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* - `line`: Line number.
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* - `nextStop`: Identifier of the next stop of the course.
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* - `arrivalTime`: Timestamp at which the vehicle is predicted to arrive
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* to the next stop.
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* - `finalStop`: The final stop to which the course is headed.
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*
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* @return Mapping from active course IDs to information about each course.
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*/
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const getCourses = () => new Promise((res, rej) =>
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{
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if (nextUpdate !== null && Date.now() < nextUpdate)
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{
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res(currentCourses);
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return;
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}
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const courses = {};
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let lastUpdate = null;
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tam.fetchRealtime((err, entry) =>
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{
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if (err)
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{
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rej(err);
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return;
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}
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if (!util.isObject(entry))
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{
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currentCourses = courses;
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res(currentCourses);
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return;
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}
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if ('lastUpdate' in entry)
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{
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lastUpdate = entry.lastUpdate;
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nextUpdate = entry.nextUpdate;
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return;
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}
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const {
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course: id,
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routeShortName: line,
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stopId: nextStop,
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destArCode: finalStop,
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} = entry;
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const arrivalTime = lastUpdate + parseInt(entry.delaySec, 10) * 1000;
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if (!(id in courses))
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{
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courses[id] = {id, line, nextStop, arrivalTime, finalStop};
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}
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else if (arrivalTime < courses[id].arrivalTime)
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{
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// The stop where the next passing is soonest is assumed
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// to be the next stop
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courses[id].nextStop = nextStop;
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courses[id].arrivalTime = arrivalTime;
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}
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});
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});
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exports.getCourses = getCourses;
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