fix: implement function of appendIntoSortedSlice

issue: #338

integration/service/oasis/stationconnquerier/station_conn_querier.go

@@ -1,6 +1,7 @@
 package stationconnquerier
 
 import (
+	"sort"
 	"strconv"
 
 	"github.com/Telenav/osrm-backend/integration/api/nav"
@@ -36,6 +37,7 @@ func New(stationFinder spatialindexer.Finder, stationRanker spatialindexer.Ranke
 	querier.connectStartIntoStationGraph(stationFinder, stationRanker, start, currEnergyLevel)
 	querier.connectEndIntoStationGraph(stationFinder, stationRanker, end, maxEnergyLevel)
 
+	glog.Info("Generate StationConnectivityQuerier.\n")
 	return querier
 }
 
@@ -57,6 +59,7 @@ func (querier *StationConnectivityQuerier) connectStartIntoStationGraph(stationF
 	}
 
 	querier.reachableStationsByStart = reachableStationsByStart
+	glog.Infof("Add %d stations connects Start.\n", len(querier.reachableStationsByStart))
 }
 
 func (querier *StationConnectivityQuerier) connectEndIntoStationGraph(stationFinder spatialindexer.Finder, stationRanker spatialindexer.Ranker,
@@ -76,6 +79,7 @@ func (querier *StationConnectivityQuerier) connectEndIntoStationGraph(stationFin
 	}
 
 	querier.reachableStationToEnd = reachableStationToEnd
+	glog.Infof("Add %d stations connects End node.\n", len(querier.reachableStationToEnd))
 }
 
 // NearByStationQuery finds near by stations by given stationID and return them in recorded sequence
@@ -147,8 +151,17 @@ func (querier *StationConnectivityQuerier) isStationConnectsToEnd(stationID stri
 
 func (querier *StationConnectivityQuerier) connectEndIntoGraph(stationID string, results []*connectivitymap.QueryResult) []*connectivitymap.QueryResult {
 	if queryResult4End, ok := querier.reachableStationToEnd[stationID]; ok {
-		results = append(results, queryResult4End)
+		return appendIntoSortedSlice(queryResult4End, results)
 	}
+	return results
+}
 
+func appendIntoSortedSlice(item *connectivitymap.QueryResult, results []*connectivitymap.QueryResult) []*connectivitymap.QueryResult {
+	insertIndex := sort.Search(len(results), func(i int) bool {
+		return results[i].Distance > item.Distance
+	})
+	results = append(results, nil)
+	copy(results[insertIndex+1:], results[insertIndex:])
+	results[insertIndex] = item
 	return results
 }

integration/service/oasis/stationconnquerier/station_conn_querier_test.go

@@ -11,6 +11,152 @@ import (
 	"github.com/Telenav/osrm-backend/integration/service/oasis/stationfinder/stationfindertype"
 )
 
+func TestAppendIntoSortedSlice(t *testing.T) {
+	cases := []struct {
+		sortedArray      []*connectivitymap.QueryResult
+		itemToBeInserted *connectivitymap.QueryResult
+		expectedArray    []*connectivitymap.QueryResult
+	}{
+		// case: insert into empty array
+		{
+			nil,
+			&connectivitymap.QueryResult{
+				StationID:       "3",
+				StationLocation: mockStation3Location,
+				Distance:        4622.08948420977,
+				Duration:        208.2022290184581,
+			},
+			[]*connectivitymap.QueryResult{
+				{
+					StationID:       "3",
+					StationLocation: mockStation3Location,
+					Distance:        4622.08948420977,
+					Duration:        208.2022290184581,
+				},
+			},
+		},
+
+		// case: insert to the head of sorted array
+		{
+			[]*connectivitymap.QueryResult{
+				{
+					StationID:       "3",
+					StationLocation: mockStation3Location,
+					Distance:        4622.08948420977,
+					Duration:        208.2022290184581,
+				},
+				{
+					StationID:       "2",
+					StationLocation: mockStation2Location,
+					Distance:        4999.134247893073,
+					Duration:        225.18622738257085,
+				},
+				{
+					StationID:       "1",
+					StationLocation: mockStation1Location,
+					Distance:        6310.598332634715,
+					Duration:        284.2611861547169,
+				},
+			},
+			&connectivitymap.QueryResult{
+				StationID:       "4",
+				StationLocation: mockStation4Location,
+				Distance:        222.0,
+				Duration:        1.0,
+			},
+			[]*connectivitymap.QueryResult{
+				{
+					StationID:       "4",
+					StationLocation: mockStation4Location,
+					Distance:        222.0,
+					Duration:        1.0,
+				},
+				{
+					StationID:       "3",
+					StationLocation: mockStation3Location,
+					Distance:        4622.08948420977,
+					Duration:        208.2022290184581,
+				},
+				{
+					StationID:       "2",
+					StationLocation: mockStation2Location,
+					Distance:        4999.134247893073,
+					Duration:        225.18622738257085,
+				},
+				{
+					StationID:       "1",
+					StationLocation: mockStation1Location,
+					Distance:        6310.598332634715,
+					Duration:        284.2611861547169,
+				},
+			},
+		},
+		// case: insert into sorted array
+		{
+			[]*connectivitymap.QueryResult{
+				{
+					StationID:       "3",
+					StationLocation: mockStation3Location,
+					Distance:        4622.08948420977,
+					Duration:        208.2022290184581,
+				},
+				{
+					StationID:       "2",
+					StationLocation: mockStation2Location,
+					Distance:        4999.134247893073,
+					Duration:        225.18622738257085,
+				},
+				{
+					StationID:       "1",
+					StationLocation: mockStation1Location,
+					Distance:        6310.598332634715,
+					Duration:        284.2611861547169,
+				},
+			},
+			&connectivitymap.QueryResult{
+				StationID:       "4",
+				StationLocation: mockStation4Location,
+				Distance:        4623.0,
+				Duration:        1.0,
+			},
+			[]*connectivitymap.QueryResult{
+				{
+					StationID:       "3",
+					StationLocation: mockStation3Location,
+					Distance:        4622.08948420977,
+					Duration:        208.2022290184581,
+				},
+				{
+					StationID:       "4",
+					StationLocation: mockStation4Location,
+					Distance:        4623.0,
+					Duration:        1.0,
+				},
+				{
+					StationID:       "2",
+					StationLocation: mockStation2Location,
+					Distance:        4999.134247893073,
+					Duration:        225.18622738257085,
+				},
+				{
+					StationID:       "1",
+					StationLocation: mockStation1Location,
+					Distance:        6310.598332634715,
+					Duration:        284.2611861547169,
+				},
+			},
+		},
+	}
+
+	for _, c := range cases {
+		actualResult := appendIntoSortedSlice(c.itemToBeInserted, c.sortedArray)
+		if !reflect.DeepEqual(actualResult, c.expectedArray) {
+			t.Errorf("Incorrect result expect %+v but got %+v\n", c.expectedArray, actualResult)
+		}
+	}
+
+}
+
 /*
 Construct graph as follows
 
@@ -226,6 +372,11 @@ var mockStation3Location = &nav.Location{
 	Lon: -121.977384,
 }
 
+var mockStation4Location = &nav.Location{
+	Lat: 11.11,
+	Lon: -22.22,
+}
+
 func (querier *mockPlaceLocationQuerier) GetLocation(placeID string) *nav.Location {
 	switch placeID {
 	case "1":