369 lines
9.7 KiB
JavaScript
369 lines
9.7 KiB
JavaScript
const axios = require('axios');
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const turf = require('@turf/turf');
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const network = require('./network.json');
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const server = 'http://localhost:4321';
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class Course
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{
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constructor(data)
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{
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this.id = data.id;
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this.passings = {};
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this.state = null;
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// Attributes for the `stopped` state
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this.currentStop = null;
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// Attributes for the `moving` state
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this.departureStop = null;
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this.arrivalStop = null;
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this.arrivalTime = 0;
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this.traveledDistance = 0;
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this.speed = 0;
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this.position = [0, 0];
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this.angle = 0;
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this.history = [];
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}
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get currentSegment()
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{
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if (this.state !== 'moving')
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{
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return undefined;
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}
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return network.segments[`${this.departureStop}-${this.arrivalStop}`];
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}
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updateData(data)
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{
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this.line = data.line;
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this.finalStop = data.finalStop;
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Object.assign(this.passings, data.nextPassings);
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const now = Date.now();
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// Make sure we’re on the right `stopped`/`moving` state
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if (this.state === null)
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{
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let previousStop = null;
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let departureTime = 0;
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let nextStop = null;
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let arrivalTime = Infinity;
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for (let [stopId, time] of Object.entries(this.passings))
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{
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if (time > now && time < arrivalTime)
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{
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nextStop = stopId;
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arrivalTime = time;
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}
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if (time < now && time > departureTime)
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{
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previousStop = stopId;
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departureTime = time;
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}
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}
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if (nextStop === null)
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{
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return false;
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}
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if (previousStop === null)
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{
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// Teleport to the first known stop
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this.arriveToStop(nextStop);
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}
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else
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{
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// Teleport to the first known segment
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this.arriveToStop(previousStop);
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this.moveToStop(nextStop, arrivalTime);
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}
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}
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else if (this.state === 'moving')
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{
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// Should already be at the next stop
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if (this.passings[this.arrivalStop] <= now)
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{
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this.arriveToStop(this.arrivalStop);
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}
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// On the right track, update the arrival time
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else
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{
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this.arrivalTime = this.passings[this.arrivalStop];
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}
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}
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else // this.state === 'stopped'
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{
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// Try moving to the next stop
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let nextStop = null;
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let arrivalTime = Infinity;
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for (let [stopId, time] of Object.entries(this.passings))
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{
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if (time > now && time < arrivalTime)
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{
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nextStop = stopId;
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arrivalTime = time;
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}
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}
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if (nextStop === null)
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{
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// This course is finished
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return false;
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}
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if (nextStop !== this.currentStop)
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{
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this.moveToStop(nextStop, arrivalTime);
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}
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}
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if (this.state === 'moving')
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{
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this.speed = this.computeTheoreticalSpeed();
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}
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return true;
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}
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tick(time)
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{
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if (this.state === null)
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{
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// Ignore uninitalized courses
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}
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else if (this.state === 'moving')
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{
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// Integrate current speed in travelled distance
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const delta = this.speed * time;
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const segment = this.currentSegment;
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const length = segment.nodes[segment.nodes.length - 1].distance;
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this.traveledDistance += delta;
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if (this.traveledDistance >= length)
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{
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this.arriveToStop(this.arrivalStop);
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return;
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}
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// Recompute updated position
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const departureStop = network.stops[this.departureStop];
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const arrivalStop = network.stops[this.arrivalStop];
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const nextNodeIndex = segment.nodes.findIndex(
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({distance}) => distance >= this.traveledDistance);
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if (nextNodeIndex === 0)
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{
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this.position = turf.toMercator([
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departureStop.lon,
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departureStop.lat
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]);
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}
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else
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{
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const previousNode = segment.nodes[nextNodeIndex - 1];
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const nextNode = segment.nodes[nextNodeIndex];
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const previousPoint = turf.toMercator([
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previousNode.lon,
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previousNode.lat
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]);
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const nextPoint = turf.toMercator([
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nextNode.lon,
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nextNode.lat
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]);
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const curLength = this.traveledDistance
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- previousNode.distance;
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const totalLength = nextNode.distance
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- previousNode.distance;
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const t = curLength / totalLength;
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this.position = [
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t * nextPoint[0] + (1 - t) * previousPoint[0],
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t * nextPoint[1] + (1 - t) * previousPoint[1],
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];
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this.angle = Math.atan2(
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previousPoint[1] - nextPoint[1],
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nextPoint[0] - previousPoint[0],
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);
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}
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}
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else // this.state === 'stopped'
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{
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const currentNode = network.stops[this.currentStop];
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this.position = turf.toMercator([
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currentNode.lon,
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currentNode.lat
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]);
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}
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}
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/**
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* Transition this course to a state where it has arrived to a stop.
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*
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* @param stop Identifier for the stop to which the course arrives.
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*/
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arriveToStop(stop)
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{
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this.state = 'stopped';
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this.currentStop = stop;
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this.position = turf.toMercator([
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network.stops[this.currentStop].lon,
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network.stops[this.currentStop].lat,
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]);
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this.history.push(['arriveToStop', stop]);
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}
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/**
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* Transition this course to a state where it is moving to a stop.
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*
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* @param stop Next stop for this course.
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* @param arrivalTime Planned arrival time to that stop.
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*/
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moveToStop(stop, arrivalTime)
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{
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if (!(`${this.currentStop}-${stop}` in network.segments))
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{
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console.warn(`Course ${this.id} is cannot go from stop
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${this.currentStop} to stop ${stop}. Teleporting to ${stop}`);
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this.arriveToStop(stop);
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return;
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}
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this.state = 'moving';
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this.departureStop = this.currentStop;
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this.arrivalStop = stop;
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this.arrivalTime = arrivalTime;
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this.traveledDistance = 0;
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this.speed = 0;
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this.position = turf.toMercator([
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network.stops[this.departureStop].lon,
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network.stops[this.departureStop].lat,
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]);
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this.history.push(['moveToStop', stop, arrivalTime]);
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console.info(`Course ${this.id} leaving stop ${this.currentStop} \
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with initial speed ${this.computeTheoreticalSpeed() * 3600} km/h`);
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}
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/**
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* Compute the speed that needs to be maintained to arrive on time.
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*/
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computeTheoreticalSpeed()
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{
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if (this.state !== 'moving')
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{
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return 0;
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}
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const segment = this.currentSegment;
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const length = segment.nodes[segment.nodes.length - 1].distance;
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const remainingTime = this.arrivalTime - Date.now();
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const remainingDistance = length - this.traveledDistance;
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if (remainingDistance <= 0)
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{
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return 0;
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}
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else if (remainingTime <= 0)
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{
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// We’re late, go to maximum speed
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return 50 / 3600; // 50 km/h
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}
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else
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{
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return remainingDistance / remainingTime;
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}
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}
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}
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const updateData = async (courses) =>
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{
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const dataset = (await axios.get(`${server}/courses`)).data;
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// Update or create new courses
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for (let [id, data] of Object.entries(dataset))
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{
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if (id in courses)
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{
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if (!courses[id].updateData(data))
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{
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console.info(`Course ${id} is finished.`);
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delete courses[id];
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}
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}
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else
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{
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const newCourse = new Course(data);
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if (!newCourse.updateData(data))
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{
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console.info(`Ignoring course ${id} which is outdated.`);
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}
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else
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{
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console.info(`Course ${id} starting.`);
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courses[id] = newCourse;
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}
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}
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}
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// Remove stale courses
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for (let id of Object.keys(courses))
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{
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if (!(id in dataset))
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{
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delete courses[id];
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}
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}
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};
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const tick = (courses, time) =>
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{
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for (let course of Object.values(courses))
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{
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course.tick(time);
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}
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};
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const start = () =>
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{
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const courses = {};
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let lastFrame = null;
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let lastUpdate = null;
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const update = () =>
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{
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const now = Date.now();
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if (lastUpdate === null || lastUpdate + 5000 <= now)
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{
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lastUpdate = now;
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updateData(courses);
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}
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const time = lastFrame === null ? 0 : now - lastFrame;
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lastFrame = now;
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tick(courses, time);
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};
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return {courses, update};
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};
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exports.start = start;
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