fix edge case where a routes first way was upside down

main.go

@@ -122,6 +122,12 @@ func main() {
 	}
 	log.Println("XML unmarshal finished")
 
+	// Create a map of IDs to Nodes
+	nodesMap := make(map[int64]*OsmNode)
+	for _, node := range osmDocument.Nodes {
+		nodesMap[node.Id] = &node
+	}
+
 	// Get the relation with id 17642638,
 	// that relation hosts the SIT data
 	var sitId int64 = 17642638
@@ -181,7 +187,7 @@ func main() {
 
 	// Convert each CombiData into a CombiRoute and store it
 	for idx, combi := range combis {
-		if idx > 0 {
+		if idx > 10 {
 			break
 		}
 
@@ -189,7 +195,7 @@ func main() {
 		returnCoord := make([][]float64, 0)
 		combiRoute := CombiRoute{
 			Name:      combi.Ref,
-			Departure: getCoordinates(&osmDocument.Ways, &osmDocument.Nodes, combi.Members),
+			Departure: getCoordinates(&osmDocument.Ways, nodesMap, combi.Members),
 			Return:    &returnCoord,
 		}
 		combiLineSlice := combiRoutesMap[combi.Id]
@@ -199,7 +205,7 @@ func main() {
 	writeOutput(combiLineMap, combiRoutesMap)
 }
 
-func getCoordinates(ways *[]OsmWay, nodes *[]OsmNode, membersSlice *[]OsmMember) *[][]float64 {
+func getCoordinates(ways *[]OsmWay, nodes map[int64]*OsmNode, membersSlice *[]OsmMember) *[][]float64 {
 	coordinates := make([][]float64, 0)
 
 	// The coordinate list may be reversed
@@ -210,6 +216,7 @@ func getCoordinates(ways *[]OsmWay, nodes *[]OsmNode, membersSlice *[]OsmMember)
 	// without duplicates
 	orderedCoordinates := make([]*OsmNode, 0)
 	var previousNodeId int64 = -1
+	var previousWayId int64 = -1
 
 	// get all coordinates from each
 	for _, member := range *membersSlice {
@@ -227,11 +234,15 @@ func getCoordinates(ways *[]OsmWay, nodes *[]OsmNode, membersSlice *[]OsmMember)
 
 		if previousNodeId == -1 {
 			// just add all
+			secondWay := findOsmway((*membersSlice)[1].Ref, ways)
+			coords = findFirstCoord(way, secondWay, nodes)
 			for _, c := range coords {
 				orderedCoordinates = append(orderedCoordinates, c)
 			}
+
 			// keep track of the last id
 			previousNodeId = coords[coordsLen-1].Id
+			previousWayId = way.Id
 		} else if coords[0].Id == previousNodeId {
 			// check if the first coordinate is the same as the previous stored
 			// if so, add them except the first one,
@@ -242,6 +253,7 @@ func getCoordinates(ways *[]OsmWay, nodes *[]OsmNode, membersSlice *[]OsmMember)
 
 			// keep track of the last id
 			previousNodeId = coords[coordsLen-1].Id
+			previousWayId = way.Id
 		} else if coords[coordsLen-1].Id == previousNodeId {
 			// if not, they are reversed
 			// add all except the last
@@ -251,8 +263,9 @@ func getCoordinates(ways *[]OsmWay, nodes *[]OsmNode, membersSlice *[]OsmMember)
 
 			// keep track of the last id
 			previousNodeId = coords[0].Id
+			previousWayId = way.Id
 		} else {
-			log.Fatalf("Found a way whose ends didn't connect to the previous way. Expected to find %d in way with id %d", previousNodeId, way.Id)
+			log.Fatalf("Found a way that didn't connect to the previous way. Expected to find node(%d) in way(%d), the previous way id is (%d)", previousNodeId, way.Id, previousWayId)
 		}
 	}
 
@@ -267,18 +280,43 @@ func getCoordinates(ways *[]OsmWay, nodes *[]OsmNode, membersSlice *[]OsmMember)
 	return &coordinates
 }
 
-func findNode(id int64, nodes *[]OsmNode) *OsmNode {
-	var coordinateNode *OsmNode
-	for _, newNode := range *nodes {
-		if newNode.Id == id {
-			coordinateNode = &newNode
+func findFirstCoord(firstWay, secondWay *OsmWay, nodes map[int64]*OsmNode) []*OsmNode {
+	// find the common point
+	first := make([]*OsmNode, 0)
+	for _, node := range firstWay.Nds {
+		coordinate := findNode(node.Ref, nodes)
+		first = append(first, coordinate)
 	}
+	firstLast := len(first) - 1
+	second := make([]*OsmNode, 0)
+	for _, node := range secondWay.Nds {
+		coordinate := findNode(node.Ref, nodes)
+		second = append(second, coordinate)
 	}
-	if coordinateNode == nil {
-		log.Fatalf("Node with id %s not found", id)
+	secondLast := len(second) - 1
+
+	if first[firstLast].Id == second[0].Id || first[firstLast].Id == second[secondLast].Id {
+		return first
+	} else if first[0].Id == second[0].Id || first[0].Id == second[secondLast].Id {
+		// reverse the slice
+		newFirst := make([]*OsmNode, len(first))
+		for i := 0; i < len(first); i += 1 {
+			newFirst[i] = first[firstLast-i]
 		}
 
-	return coordinateNode
+		return newFirst
+	} else {
+		log.Fatalf("Could not find 2 points in common between 2 ways with ids %d & %d", firstWay.Id, secondWay.Id)
+		panic("")
+	}
+}
+
+func findNode(id int64, nodes map[int64]*OsmNode) *OsmNode {
+	node := nodes[id]
+	if node == nil {
+		log.Fatalf("Node with id %s not found", id)
+	}
+	return node
 }
 
 func findOsmway(id int64, ways *[]OsmWay) *OsmWay {