255 lines
8.1 KiB
JavaScript
255 lines
8.1 KiB
JavaScript
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const requestp = require('request-promise-native');
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const geolib = require('geolib');
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const {makeCached} = require('../util');
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const OVERPASS_ENDPOINT = 'https://lz4.overpass-api.de/api/interpreter';
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const fetch = makeCached(async (lineRefs) =>
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{
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// Retrieve routes, ways and stops from OpenStreetMap
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const rawData = await requestp.post(OVERPASS_ENDPOINT, {form: `\
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data=[out:json];
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// Find the public transport line bearing the requested reference
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relation[network="TaM"][type="route_master"][ref~"^(${lineRefs.join('|')})$"];
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// Recursively fetch routes, ways and stops inside the line
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(._; >>;);
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out body qt;
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`});
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// List of retrieved objects
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const elementsList = JSON.parse(rawData).elements;
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// List of retrieved lines
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const routeMasters = elementsList.filter(elt =>
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elt.tags && elt.tags.type === 'route_master'
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);
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// Retrieved objects indexed by ID
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const elements = elementsList.reduce((prev, elt) =>
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{
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prev[elt.id] = elt;
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return prev;
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}, {});
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// Result object containing all stops
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const stops = {};
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// Result object containing all segments between stops
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const segments = {};
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// Result object containing all lines
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const lines = {};
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for (let routeMaster of routeMasters)
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{
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const lineRef = routeMaster.tags.ref;
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const color = routeMaster.tags.colour || '#000000';
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// Extract all routes for the given line
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const rawRoutes = routeMaster.members.map(({ref}) => elements[ref]);
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// Add missing stops to the result object
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for (let route of rawRoutes)
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{
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for (let {ref, role} of route.members)
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{
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if (role === 'stop')
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{
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const stop = elements[ref];
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if (!('ref' in stop.tags))
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{
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console.warn(`Stop ${stop.id} is missing a “ref” tag`);
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continue;
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}
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if (!(stop.tags.ref in stops))
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{
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stops[stop.tags.ref] = {
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lat: stop.lat,
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lon: stop.lon,
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name: stop.tags.name,
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lines: [lineRef],
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};
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}
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else
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{
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stops[stop.tags.ref].lines.push(lineRef);
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}
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}
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}
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}
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// Add missing segments between stops
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for (let route of rawRoutes)
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{
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const {from, to} = route.tags;
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const stops = route.members
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.filter(({role}) => role === 'stop')
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.map(({ref}) => elements[ref])
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.filter(stop => 'ref' in stop.tags)
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.map(stop => ({
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id: stop.id,
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lat: stop.lat,
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lon: stop.lon,
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ref: stop.tags.ref,
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name: stop.tags.name,
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}));
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const ways = route.members
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.filter(({role}) => role === '')
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.map(({ref}) => ref);
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// Construct a graph with all connected nodes
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const nodeNeighbors = new Map();
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for (let id of ways)
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{
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const {type, nodes, tags} = elements[id];
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const isOneWay = (
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tags.oneway === 'yes'
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|| tags.junction === 'roundabout'
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);
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const canGoBackward = (
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!isOneWay
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|| parseInt(tags['lanes:psv:backward'], 10) > 0
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);
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if (type === 'way' && nodes.length >= 1)
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{
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let previousNode = nodes[0];
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if (!nodeNeighbors.has(previousNode))
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{
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nodeNeighbors.set(previousNode, new Set());
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}
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for (let node of nodes.slice(1))
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{
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if (!nodeNeighbors.has(node))
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{
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nodeNeighbors.set(node, new Set());
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}
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nodeNeighbors.get(previousNode).add(node);
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if (canGoBackward)
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{
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nodeNeighbors.get(node).add(previousNode);
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}
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previousNode = node;
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}
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}
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}
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// Find way from first stop through the end using DFS
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const numberOfStops = stops.length;
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let currentStopIndex = 0;
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while (currentStopIndex + 1 < numberOfStops)
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{
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const currentStop = stops[currentStopIndex];
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const nextStop = stops[currentStopIndex + 1];
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const segmentId = `${currentStop.ref}-${nextStop.ref}`;
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if (!(segmentId in segments))
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{
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const visitedEdges = new Set();
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const stack = [{
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currentNode: currentStop.id,
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segment: [currentStop.id],
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}];
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let found = false;
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while (stack.length !== 0)
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{
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const {currentNode, segment} = stack.pop();
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if (currentNode === nextStop.id)
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{
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// Arrived at next stop
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segments[segmentId] = {
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nodes: segment.map(id =>
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{
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const {lat, lon} = elements[id];
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return {lat, lon};
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}),
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length: geolib.getPathLength(segment.map(id =>
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{
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const {lat, lon} = elements[id];
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return {latitude: lat, longitude: lon};
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})),
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lines: [lineRef],
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};
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found = true;
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break;
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}
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const neighbors = nodeNeighbors.get(currentNode) || [];
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for (let nextNode of neighbors)
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{
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const edge = `${currentNode}-${nextNode}`;
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if (!visitedEdges.has(edge))
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{
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visitedEdges.add(edge);
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stack.push({
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currentNode: nextNode,
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segment: segment.concat([nextNode]),
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});
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}
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}
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}
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if (!found)
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{
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throw new Error(`No way between stop \
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“${currentStop.name}” (${currentStop.id}) and stop “${nextStop.name}” \
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(${nextStop.id}) on line ${lineRef}’s route from “${from}” to “${to}”`);
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}
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}
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else
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{
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segments[segmentId].lines.push(lineRef);
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}
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++currentStopIndex;
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}
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}
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// Construct line objects
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const routes = rawRoutes.map(route => ({
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from: route.tags.from,
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to: route.tags.to,
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// Retrieve each stop’s information (stop order in the relation is
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// assumed to reflect reality)
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stops: route.members
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.filter(({role}) => role === 'stop')
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.map(({ref}) => elements[ref])
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.filter(stop => 'ref' in stop.tags)
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.map(stop => stop.tags.ref)
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}));
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lines[lineRef] = {
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color,
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routes
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};
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}
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return {stops, segments, lines};
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});
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exports.fetch = fetch;
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