Use PTv2 standard instead of DFS for finding segments

back/data/network.js

@@ -124,6 +124,17 @@ const matchStopNames = (fullName, abbrName) =>
     ).length;
 };
 
+/**
+ * Determine if an OSM way is oneway or not.
+ *
+ * @param tags Set of tags of the way.
+ * @return True iff. the way is oneway.
+ */
+const isOneWay = tags =>
+    ('oneway' in tags && tags.oneway === 'yes')
+    || ('junction' in tags && tags.junction === 'roundabout')
+    || ('highway' in tags && tags.highway === 'motorway');
+
 /**
  * Fetch stops, segments and lines in the network.
  *
@@ -162,13 +173,10 @@ out body qt;
         return prev;
     }, {});
 
-    // Result object containing all stops
+    // All stops in the network
     const stops = {};
 
-    // Result object containing all segments between stops
+    // All transport lines of the network
-    const segments = {};
-
-    // Result object containing all lines
     const lines = {};
 
     for (let routeMaster of routeMasters)
@@ -234,7 +242,7 @@ URI: ${osmViewNode}/${stop.id}
 
                         if (candidates.length === 0)
                         {
-                            console.warn('No candidate found in TaM data.');
+                            console.warn('No candidate found in TaM data.');
                         }
                         else
                         {
@@ -272,171 +280,142 @@ ${joinSentence(Array.from(candidate.directions), ', ', ' or ')}
             }
         }
 
-        // Add missing segments between stops
+        // Reconstruct the line’s route from stop to stop
+        const routes = [];
+
         for (let route of rawRoutes)
         {
             const {from, to} = route.tags;
 
-            const stops = route.members
+            // Human-readable description of the route for errors
-                .filter(({role}) => role === 'stop')
+            const routeDescription = `line ${lineRef}’s route from \
-                .map(({ref}) => elements[ref])
+“${route.tags.from}” to “${route.tags.to}”`;
-                .filter(stop => 'ref' in stop.tags)
-                .map(stop => ({
-                    id: stop.id,
-                    lat: stop.lat,
-                    lon: stop.lon,
-                    ref: stop.tags.ref,
-                    name: stop.tags.name,
-                }));
 
-            const ways = route.members
+            // Check that the route consists of a block of stops and platforms
-                .filter(({role}) => role === '')
+            // followed by a block of routes as dictated by PTv2
-                .map(({ref}) => ref);
+            const relationPivot = route.members.findIndex(
+                ({role}) => role === ''
+            );
 
-            // Construct a graph with all connected nodes
+            if (!route.members.slice(0, relationPivot).every(
-            const nodeNeighbors = new Map();
+                ({role}) => role === 'stop' || role === 'platform'
-
+            ))
-            for (let id of ways)
             {
-                const {type, nodes, tags} = elements[id];
+                throw new Error(`Members with invalid roles in between stops
-
+of ${routeDescription}`);
-                const isOneWay = (
-                    tags.oneway === 'yes'
-                    || tags.junction === 'roundabout'
-                );
-
-                const canGoBackward = (
-                    !isOneWay
-                    || parseInt(tags['lanes:psv:backward'], 10) > 0
-                );
-
-                if (type === 'way' && nodes.length >= 1)
-                {
-                    let previousNode = nodes[0];
-
-                    if (!nodeNeighbors.has(previousNode))
-                    {
-                        nodeNeighbors.set(previousNode, new Set());
-                    }
-
-                    for (let node of nodes.slice(1))
-                    {
-                        if (!nodeNeighbors.has(node))
-                        {
-                            nodeNeighbors.set(node, new Set());
-                        }
-
-                        nodeNeighbors.get(previousNode).add(node);
-
-                        if (canGoBackward)
-                        {
-                            nodeNeighbors.get(node).add(previousNode);
-                        }
-
-                        previousNode = node;
-                    }
-                }
             }
 
-            // Find way from first stop through the end using DFS
+            if (!route.members.slice(relationPivot).every(
-            const numberOfStops = stops.length;
+                ({role}) => role === ''
-            let currentStopIndex = 0;
+            ))
-
-            while (currentStopIndex + 1 < numberOfStops)
             {
-                const currentStop = stops[currentStopIndex];
+                throw new Error(`Members with invalid roles inside the path
-                const nextStop = stops[currentStopIndex + 1];
+of ${routeDescription}`);
-                const segmentId = `${currentStop.ref}-${nextStop.ref}`;
+            }
 
-                if (!(segmentId in segments))
+            // List of stops in the route, expected to be in the timetable
+            // order as per PTv2 and to be traversed in order by the sequence
+            // of ways extracted below
+            const stops = route.members.slice(0, relationPivot)
+                .filter(({role}) => role === 'stop')
+                .map(({ref}) => ref);
+
+            // List of ways making up the route’s path through its stops
+            // with each way connected to the next through a single point
+            const ways = route.members.slice(relationPivot)
+                .map(({ref}) => ref);
+
+            // Merge all used ways in a single path
+            let path = [];
+            let currentNode = stops[0];
+
+            for (let wayIndex = 0; wayIndex < ways.length; wayIndex += 1)
+            {
+                const {nodes: wayNodes, tags: wayTags}
+                    = elements[ways[wayIndex]];
+                const wayNodesSet = new Set(wayNodes);
+
+                const curNodeIndex = wayNodes.indexOf(currentNode);
+
+                // If not the last way, find a connection point to the next way
+                // (there should be exactly one)
+                let nextNode = null;
+                let nextNodeIndex = null;
+
+                if (wayIndex + 1 < ways.length)
                 {
-                    const visitedEdges = new Set();
+                    const nextNodeCandidates = elements[ways[wayIndex + 1]]
-                    const stack = [{
+                        .nodes.filter(node => wayNodesSet.has(node));
-                        currentNode: currentStop.id,
-                        segment: [currentStop.id],
-                    }];
 
-                    let found = false;
+                    if (nextNodeCandidates.length !== 1)
-
-                    while (stack.length !== 0)
                     {
-                        const {currentNode, segment} = stack.pop();
+                        throw new Error(`There should be exactly one point
-
+connecting way n°${wayIndex} and way n°${wayIndex + 1} in ${routeDescription},
-                        if (currentNode === nextStop.id)
+but there are ${nextNodeCandidates.length}`);
-                        {
-                            // Arrived at next stop
-                            segments[segmentId] = {
-                                nodes: segment.map(id =>
-                                {
-                                    const {lat, lon} = elements[id];
-                                    return {lat, lon};
-                                }),
-                                length: geolib.getPathLength(segment.map(id =>
-                                {
-                                    const {lat, lon} = elements[id];
-                                    return {latitude: lat, longitude: lon};
-                                })),
-                                lines: new Set([lineRef]),
-                            };
-
-                            found = true;
-                            break;
-                        }
-
-                        const neighbors = nodeNeighbors.get(currentNode) || [];
-
-                        for (let nextNode of neighbors)
-                        {
-                            const edge = `${currentNode}-${nextNode}`;
-
-                            if (!visitedEdges.has(edge))
-                            {
-                                visitedEdges.add(edge);
-                                stack.push({
-                                    currentNode: nextNode,
-                                    segment: segment.concat([nextNode]),
-                                });
-                            }
-                        }
                     }
 
-                    if (!found)
+                    nextNode = nextNodeCandidates[0];
-                    {
+                    nextNodeIndex = wayNodes.indexOf(nextNode);
-                        throw new Error(`No way between stop \
-“${currentStop.name}” (${currentStop.id}) and stop “${nextStop.name}” \
-(${nextStop.id}) on line ${lineRef}’s route from “${from}” to “${to}”`);
-                    }
                 }
                 else
                 {
-                    segments[segmentId].lines.add(lineRef);
+                    nextNodeIndex = wayNodes.length;
                 }
 
-                ++currentStopIndex;
+                if (curNodeIndex < nextNodeIndex)
+                {
+                    // Use the way in its normal direction
+                    path = path.concat(
+                        wayNodes.slice(curNodeIndex, nextNodeIndex)
+                    );
+                }
+                else
+                {
+                    // Use the way in the reverse direction
+                    if (isOneWay(wayTags))
+                    {
+                        throw new Error(`Way n°${wayIndex} in
+${routeDescription} is one-way and cannot be used in reverse.`);
+                    }
+
+                    path = path.concat(
+                        wayNodes.slice(nextNodeIndex + 1, curNodeIndex + 1)
+                                .reverse()
+                    );
+                }
+
+                currentNode = nextNode;
             }
+
+            // Split the path into segments between stops
+            const segments = [];
+
+            for (let stopIndex = 0; stopIndex + 1 < stops.length; ++stopIndex)
+            {
+                segments.push(path.slice(
+                    path.indexOf(stops[stopIndex]),
+                    path.indexOf(stops[stopIndex + 1] + 1),
+                ).map(id => ({
+                    lat: elements[id].lat,
+                    lon: elements[id].lon,
+                })));
+            }
+
+            routes.push({
+                from, to,
+                name: route.tags.name,
+                segments,
+                stops: stops.map(id => elements[id].tags.ref),
+            });
         }
 
-        // Construct line objects
-        const routes = rawRoutes.map(route => ({
-            from: route.tags.from,
-            to: route.tags.to,
-
-            // Retrieve each stop’s information (stop order in the relation is
-            // assumed to reflect reality)
-            stops: route.members
-                .filter(({role}) => role === 'stop')
-                .map(({ref}) => elements[ref])
-                .filter(stop => 'ref' in stop.tags)
-                .map(stop => stop.tags.ref),
-        }));
-
         lines[lineRef] = {
             color,
             routes,
         };
     }
 
-    return {stops, segments, lines};
+    return {stops, lines};
 };
 
 exports.fetch = fetch;

script/update-network.js

@@ -23,7 +23,7 @@ const fs = require('fs');
 
                 return value;
             },
-            '    '
+            4
         )
     );
 })();