src/tam/courses.js

@@ -37,11 +37,6 @@ const parseTime = (time, reference) => {
     return result;
 };
 
-/** List of OSM nodes that are stops. */
-const stopsSet = new Set(
-    Object.values(network.stops).map(stop => stop.properties.node)
-);
-
 /** Guess whether a stop comes directly before another one. */
 const isPenultimateStop = (stop, finalStop) => {
     // If there is a standard segment linking both stops, it’s certainly
@@ -58,8 +53,8 @@ const isPenultimateStop = (stop, finalStop) => {
     }
 
     // If there is another stop in the way, it can’t be either
-    for (const nodeId of route.slice(1, -1)) {
+    for (const node of route.slice(1, -1)) {
-        if (stopsSet.has(nodeId)) {
+        if (node in network.stops) {
             return false;
         }
     }

src/tam/network.js

@@ -340,7 +340,7 @@ different sequence of nodes in two or more lines.`);
  * Create a graph for navigating between stops.
  * @param {Array.<Object>} elementsList List of nodes retrieved from OSM.
  * @param {Object.<string,Object>} elementsById OSM nodes indexed by their ID.
- * @return {Object} Resulting graph and reverse arcs.
+ * @return {Object.<string,Object.<string,NavigationEdge>} Resulting graph.
  */
 const createNavigationGraph = (elementsList, elementsById) => {
     const navigation = {};
@@ -350,7 +350,7 @@ const createNavigationGraph = (elementsList, elementsById) => {
     for (const obj of elementsList) {
         if (obj.type === "node") {
             navigation[obj.id] = {};
-            navigationReverse[obj.id] = new Set();
+            navigationReverse[obj.id] = {};
         }
     }
 
@@ -360,27 +360,27 @@ const createNavigationGraph = (elementsList, elementsById) => {
             const oneWay = osm.isOneWay(obj);
 
             for (let i = 0; i + 1 < obj.nodes.length; ++i) {
-                const from = obj.nodes[i].toString();
+                const from = obj.nodes[i];
-                let to = obj.nodes[i + 1].toString();
+                let to = obj.nodes[i + 1];
-                let path = [from, to];
+                let path = [from.toString(), to.toString()];
 
                 // Make sure we can’t jump between rails at railway crossings
                 if (i + 2 < obj.nodes.length
                         && osm.isRailwayCrossing(elementsById[to])) {
-                    const next = obj.nodes[i + 2].toString();
+                    const next = obj.nodes[i + 2];
-                    path = [from, to, next];
+                    path = [from.toString(), to.toString(), next.toString()];
                     to = next;
                     i += 1;
                 }
 
                 navigation[from][to] = path;
-                navigationReverse[to].add(from);
+                navigationReverse[to][from] = true;
 
                 if (!oneWay) {
                     const reversePath = [...path];
                     reversePath.reverse();
                     navigation[to][from] = reversePath;
-                    navigationReverse[from].add(to);
+                    navigationReverse[from][to] = true;
                 }
             }
         }
@@ -390,22 +390,29 @@ const createNavigationGraph = (elementsList, elementsById) => {
 };
 
 /**
- * Identify intermediate nodes of the navigation graph that can be simplified.
+ * Remove and relink nodes that connect only two nodes or less.
- * @param {Set.<string>} stopsSet OSM IDs of stop nodes.
+ * @param {Object.<string,Stop>} stops List of stops.
  * @param {Navigation} navigation Input navigation graph.
- * @param {Object.<string,Set.<string>>} navigationReverse Reverse arcs.
+ * @param {Object.<string,Object.<string,boolean>>} navigationReverse
- * @return {Set.<string>} Set of compressible nodes.
+ * Backward edges of the navigation graph.
  */
-const findCompressibleNodes = (stopsSet, navigation, navigationReverse) => {
+const compressNavigationGraph = (stops, navigation, navigationReverse) => {
-    const compressible = new Set();
+    const stopsReverse = Object.fromEntries(
+        Object.entries(stops).map(([id, stop]) => [stop.properties.node, id])
+    );
 
+    let removedDeadEnds = true;
+    const nodesToCompress = {};
+
+    while (removedDeadEnds) {
+        // Identify nodes to be compressed
         for (const nodeId in navigation) {
-        if (stopsSet.has(nodeId)) {
+            if (nodeId in stopsReverse) {
                 // Keep stop nodes
                 continue;
             }
 
-        const entries = navigationReverse[nodeId];
+            const entries = new Set(Object.keys(navigationReverse[nodeId]));
             const exits = new Set(Object.keys(navigation[nodeId]));
 
             // Keep split nodes, i.e. nodes with at least two exit nodes
@@ -455,34 +462,26 @@ const findCompressibleNodes = (stopsSet, navigation, navigationReverse) => {
             }
 
             // Compress all other nodes
-        compressible.add(nodeId);
+            nodesToCompress[nodeId] = true;
         }
 
-    return compressible;
+        // Find nodes that cannot be used to directly link up two kept nodes
-};
+        const usedNodes = {};
 
-/**
- * Remove nodes that are not used to link up two kept nodes.
- * @param {Navigation} navigation Input navigation graph.
- * @param {Object.<string,Set.<string>>} navigationReverse Reverse arcs.
- * @param {Set.<string>} compressible Set of nodes that will not be kept.
- * @return {boolean} True if some dead-ends were removed.
- */
-const removeDeadEnds = (navigation, navigationReverse, compressible) => {
-    let didRemove = false;
-
-    // Find dead-ends starting from kept nodes
         for (const beginId in navigation) {
-        if (compressible.has(beginId)) {
+            if (beginId in nodesToCompress) {
                 continue;
             }
 
+            usedNodes[beginId] = true;
+
+            // Start a DFS from each node to be kept
             const begin = navigation[beginId];
             const stack = [];
             const parent = {[beginId]: beginId};
 
             for (const succId in begin) {
-            if (compressible.has(succId)) {
+                if (succId in nodesToCompress) {
                     stack.push(succId);
                     parent[succId] = beginId;
                 }
@@ -492,103 +491,57 @@ const removeDeadEnds = (navigation, navigationReverse, compressible) => {
                 const endId = stack.pop();
                 const end = navigation[endId];
 
-            if (compressible.has(endId)) {
+                if (!(endId in nodesToCompress)) {
-                let hasSuccessor = false;
+                    let trackback = parent[endId];
-
-                for (const succId in end) {
-                    if (succId !== parent[endId]) {
-                        parent[succId] = endId;
-                        stack.push(succId);
-                        hasSuccessor = true;
-                    }
-                }
-
-                if (!hasSuccessor) {
-                    // Remove the dead-end path
-                    let trackback = endId;
 
                     while (trackback !== beginId) {
-                        navigationReverse[trackback].delete(parent[trackback]);
+                        usedNodes[trackback] = true;
-                        delete navigation[parent[trackback]][trackback];
                         trackback = parent[trackback];
                     }
-
-                    didRemove = true;
-                }
-            }
-        }
-    }
-
-    // Find dead-ends starting from compressible source nodes
-    for (const beginId in navigation) {
-        if (!compressible.has(beginId)) {
-            continue;
-        }
-
-        if (navigationReverse[beginId].size > 0) {
-            continue;
-        }
-
-        const begin = navigation[beginId];
-        const stack = [];
-        const parent = {[beginId]: beginId};
-
-        for (const succId in begin) {
-            stack.push(succId);
-            parent[succId] = beginId;
-        }
-
-        while (stack.length > 0) {
-            const endId = stack.pop();
-            const end = navigation[endId];
-
-            if (compressible.has(endId)) {
-                for (const succId in end) {
-                    if (succId !== parent[endId]) {
-                        parent[succId] = endId;
-                        stack.push(succId);
-                    }
-                }
                 } else {
-                // Remove the dead-end path
+                    for (const succId in end) {
-                let trackback = endId;
+                        if (succId !== parent[endId]) {
-
+                            parent[succId] = endId;
-                while (trackback !== beginId) {
+                            stack.push(succId);
-                    navigationReverse[trackback].delete(parent[trackback]);
+                        }
-                    delete navigation[parent[trackback]][trackback];
-                    trackback = parent[trackback];
                     }
-
-                didRemove = true;
                 }
             }
         }
 
-    return didRemove;
+        // Remove dead-end nodes
-};
+        removedDeadEnds = false;
-
-/**
- * Compress the given set of nodes.
- * @param {Navigation} navigation Input navigation graph.
- * @param {Object.<string,Set.<string>>} navigationReverse Reverse arcs.
- * @param {Set.<string>} compressible Set of nodes to compress.
- * @return {boolean} True if some nodes were compressed.
- */
-const removeCompressibleNodes = (navigation, navigationReverse, compressible) => {
-    let didCompress = false;
 
         for (const beginId in navigation) {
-        if (compressible.has(beginId)) {
+            if (!(beginId in usedNodes)) {
+                for (const neighborId in navigation[beginId]) {
+                    delete navigationReverse[neighborId][beginId];
+                }
+
+                for (const neighborId in navigationReverse[beginId]) {
+                    delete navigation[neighborId][beginId];
+                }
+
+                delete navigation[beginId];
+                delete navigationReverse[beginId];
+                removedDeadEnds = true;
+            }
+        }
+    }
+
+    // Perform node compression
+    for (const beginId in navigation) {
+        if (beginId in nodesToCompress) {
             continue;
         }
 
-        // Start a DFS from each kept node
+        // Start a DFS from each node to be kept
         const begin = navigation[beginId];
         const stack = [];
         const parent = {[beginId]: beginId};
 
         for (const succId in begin) {
-            if (compressible.has(succId)) {
+            if (succId in nodesToCompress) {
                 stack.push(succId);
                 parent[succId] = beginId;
             }
@@ -598,35 +551,44 @@ const removeCompressibleNodes = (navigation, navigationReverse, compressible) =>
             const endId = stack.pop();
             const end = navigation[endId];
 
-            if (!compressible.has(endId)) {
+            if (!(endId in nodesToCompress)) {
                 // Found another kept node
-                // Collect and remove intermediate path
+                // Collect and remove intermediate nodes
-                let path = [];
+                const reversePath = [endId];
-                let trackback = endId;
+                let trackback = parent[endId];
+                let oneWay = !(trackback in end);
 
-                do {
+                while (trackback !== beginId) {
-                    const segment = [...navigation[parent[trackback]][trackback]];
+                    reversePath.push(trackback);
-                    segment.reverse();
+                    oneWay = oneWay || !(parent[trackback] in navigation[trackback]);
-                    path = path.concat(segment.slice(0, -1));
-
-                    navigationReverse[trackback].delete(parent[trackback]);
-                    delete navigation[parent[trackback]][trackback];
 
+                    delete navigation[trackback];
+                    delete navigationReverse[trackback];
                     trackback = parent[trackback];
-                } while (trackback !== beginId);
-
-                // Make sure not to add loops if we’re compressing a cycle
-                if (endId !== beginId) {
-                    path.push(beginId);
-                    path.reverse();
-
-                    begin[endId] = path;
-                    navigationReverse[endId].add(beginId);
                 }
 
-                didCompress = true;
+                reversePath.push(beginId);
+                const forwardPath = [...reversePath];
+                forwardPath.reverse();
+
+                // Create edges to link both nodes directly
+                delete begin[forwardPath[1]];
+                delete navigationReverse[endId][reversePath[1]];
+
+                delete end[reversePath[1]];
+                delete navigationReverse[beginId][forwardPath[1]];
+
+                if (!(endId in begin)) {
+                    begin[endId] = forwardPath;
+                    navigationReverse[endId][beginId] = true;
+                }
+
+                if (!oneWay && !(beginId in end)) {
+                    end[beginId] = reversePath;
+                    navigationReverse[beginId][endId] = true;
+                }
             } else {
-                // Continue the traversal down compressible nodes
+                // Continue the traversal down unused nodes
                 let isFirst = true;
 
                 for (const succId in end) {
@@ -644,57 +606,6 @@ non-junction node ${endId}`);
             }
         }
     }
-
-    return didCompress;
-};
-
-/**
- * Find nodes in the graph that have no exits nor entries and remove them.
- * @param {Navigation} navigation Input navigation graph.
- * @param {Object.<string,Set.<string>>} navigationReverse Reverse arcs.
- */
-const cleanUpIsolatedNodes = (navigation, navigationReverse) => {
-    for (const nodeId in navigation) {
-        if (
-            Object.keys(navigation[nodeId]).length === 0
-            && navigationReverse[nodeId].size === 0
-        ) {
-            delete navigation[nodeId];
-            delete navigationReverse[nodeId];
-        }
-    }
-};
-
-/**
- * Remove and relink nodes that connect only two nodes or less.
- * @param {Object.<string,Stop>} stops List of stops.
- * @param {Navigation} navigation Input navigation graph.
- * @param {Object.<string,Set.<string>>} navigationReverse Reverse arcs.
- */
-const compressNavigationGraph = (stops, navigation, navigationReverse) => {
-    const stopsSet = new Set(
-        Object.values(stops).map(stop => stop.properties.node)
-    );
-    let compressible = null;
-    let didCompress = true;
-
-    while (didCompress) {
-        let didRemove = true;
-
-        while (didRemove) {
-            compressible = findCompressibleNodes(
-                stopsSet, navigation, navigationReverse
-            );
-            didRemove = removeDeadEnds(
-                navigation, navigationReverse, compressible
-            );
-        }
-
-        didCompress = removeCompressibleNodes(
-            navigation, navigationReverse, compressible
-        );
-        cleanUpIsolatedNodes(navigation, navigationReverse);
-    }
 };
 
 /**

src/tam/routing.js

@@ -16,23 +16,14 @@ for (const [beginId, begin] of Object.entries(network.navigation)) {
 }
 
 /**
- * Get the OSM ID of a stop.
+ * Find the shortest path of nodes linking two nodes or stops.
- * @param {string} stopId Network ID of the stop.
+ * @param {string} from ID of the starting stop or node.
- * @return {string} OSM ID of the stop.
+ * @param {string} to ID of the ending stop or node.
+ * @return {Array.<string>} If possible, list of nodes joining `from` to `to`.
  */
-export const stopToOSM = stopId => network.stops[stopId].properties.node;
+export const findPath = (from, to) => {
-
-/**
- * Find the shortest path of nodes linking two stops.
- * @param {string} fromStop Network ID of the starting stop.
- * @param {string} toStop Network ID of the ending stop.
- * @return {Array.<string>} If it exists, a path of nodes joining the two stops.
- */
-export const findPath = (fromStop, toStop) => {
     try {
-        return dijkstra.find_path(
+        return dijkstra.find_path(graph, from, to);
-            graph, stopToOSM(fromStop), stopToOSM(toStop)
-        );
     } catch (err) {
         return null;
     }
@@ -40,12 +31,12 @@ export const findPath = (fromStop, toStop) => {
 
 /**
  * Find the shortest segment linking two nodes or stops.
- * @param {string} fromStop Network ID of the starting stop.
+ * @param {string} from ID of the starting stop or node.
- * @param {string} toStop Network ID of the ending stop.
+ * @param {string} to ID of the ending stop or node.
- * @return {LineString?} If it exists, a segment joining the two stops.
+ * @return {LineString?} If it exists, a segment linking the two nodes.
  */
-export const findSegment = (fromStop, toStop) => {
+export const findSegment = (from, to) => {
-    const path = findPath(fromStop, toStop);
+    const path = findPath(from, to);
 
     if (path === null) {
         return null;