107 lines
2.8 KiB
JavaScript
107 lines
2.8 KiB
JavaScript
const tam = require('./sources/tam');
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const util = require('../util');
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const network = require('./network.json');
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// Time at which the course data needs to be updated next
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let nextUpdate = null;
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// Current information about courses
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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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* - `finalStop`: The final stop to which the course is headed.
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* - `nextPassings`: Next passings of the vehicle, as a dictionary associating
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* each next stop to the passing timestamp.
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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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// Filter courses to only keep those referring to known data
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for (let courseId of Object.keys(courses))
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{
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const course = courses[courseId];
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if (!(course.line in network.lines))
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{
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delete courses[courseId];
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}
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else
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{
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for (let stopId of Object.keys(course.nextPassings))
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{
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if (!(stopId in network.stops))
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{
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delete courses[courseId];
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break;
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}
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}
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}
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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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// Metadata header
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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,
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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] = {
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id, line, finalStop,
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nextPassings: {[stopId]: arrivalTime},
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};
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}
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else
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{
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courses[id].nextPassings[stopId] = arrivalTime;
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}
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});
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});
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exports.getCourses = getCourses;
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