259 lines
6.9 KiB
JavaScript
259 lines
6.9 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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const arriveAtStop = (course, stop) =>
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{
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course.state = 'stopped';
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course.currentStop = stop;
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delete course.departureStop;
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delete course.arrivalStop;
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delete course.arrivalTime;
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delete course.traveledDistance;
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delete course.speed;
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};
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const moveToStop = (course, stop, arrivalTime) =>
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{
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course.state = 'moving';
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course.departureStop = course.currentStop;
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course.arrivalStop = stop;
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course.arrivalTime = arrivalTime;
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course.traveledDistance = 0;
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course.speed = 0;
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delete course.currentStop;
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const segment = `${course.departureStop}-${course.arrivalStop}`;
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if (!(segment in network.segments))
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{
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// There is no segment between the two requested stops, jump
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// directly to the arrival stop
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arriveAtStop(course, course.arrivalStop);
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}
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else
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{
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updateSpeed(course);
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}
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};
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const getCurrentSegment = course =>
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{
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if (course.state === 'stopped')
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{
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return null;
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}
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return network.segments[`${course.departureStop}-${course.arrivalStop}`];
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};
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const updateSpeed = course =>
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{
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const segment = getCurrentSegment(course);
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const length = segment.points[segment.points.length - 1].distance;
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const remainingTime = course.arrivalTime - Date.now();
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const remainingDistance = length - course.traveledDistance;
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if (remainingTime <= 0 || remainingDistance <= 0)
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{
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arriveAtStop(course, course.arrivalStop);
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return;
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}
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course.speed = remainingDistance / remainingTime;
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};
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const updateFromTam = async (courses) =>
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{
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const currentCourses = (await axios.get(`${server}/courses`)).data;
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for (let [id, course] of Object.entries(currentCourses))
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{
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// Find out the next stop, ignoring the ones that are in the past
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let nextStop = null;
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let arrivalTime = null;
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for (let {stopId, arrivalTime: time} of course.nextPassings)
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{
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if (time > Date.now())
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{
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nextStop = stopId;
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arrivalTime = time;
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break;
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}
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}
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if (nextStop === null)
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{
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continue;
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}
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// Update an existing course
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if (id in courses)
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{
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const prev = courses[id];
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if (prev.state === 'stopped')
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{
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if (prev.currentStop !== nextStop)
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{
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// Start traveling from the current stop to the next
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moveToStop(prev, nextStop, arrivalTime);
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}
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}
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else
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{
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// Update the ETA if we’re still headed to the same stop
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if (prev.arrivalStop === nextStop)
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{
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prev.arrivalTime = arrivalTime;
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updateSpeed(prev);
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}
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// Otherwise, we missed a stop, try to go directly to the
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// next segment
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else
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{
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arriveAtStop(prev, prev.arrivalStop);
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moveToStop(prev, nextStop, arrivalTime);
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}
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}
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}
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// Create a new course
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else
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{
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courses[id] = {
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id,
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line: course.line,
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finalStop: course.finalStop,
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position: [0, 0],
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angle: 0,
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};
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arriveAtStop(courses[id], nextStop);
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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 currentCourses))
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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 updatePositions = (courses, time) =>
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{
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for (let [id, course] of Object.entries(courses))
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{
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if (course.state === 'moving')
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{
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// Increase the travelled distance respective to the current speed
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const delta = course.speed * time;
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const segment = getCurrentSegment(course);
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const length = segment.points[segment.points.length - 1].distance;
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if (course.traveledDistance + delta >= length)
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{
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course.traveledDistance = length;
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}
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else
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{
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course.traveledDistance += delta;
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}
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// Recompute updated position
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const departureStop = network.stops[course.departureStop];
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const arrivalStop = network.stops[course.arrivalStop];
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const nextNodeIndex = segment.points.findIndex(
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({distance}) => distance >= course.traveledDistance);
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if (nextNodeIndex === 0)
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{
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course.position = {
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lat: departureStop.lat,
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lon: departureStop.lon
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};
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}
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else if (nextNodeIndex === -1)
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{
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course.position = {
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lat: arrivalStop.lat,
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lon: arrivalStop.lon
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};
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}
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else
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{
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const previousNode = segment.points[nextNodeIndex - 1];
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const nextNode = segment.points[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 = course.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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course.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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course.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
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{
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const currentNode = network.stops[course.currentStop];
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course.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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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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updateFromTam(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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updatePositions(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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