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geometry_utils.go
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geometry_utils.go
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package polyfetcher
import (
"context"
"encoding/json"
"errors"
"fmt"
"github.com/jinagamvasubabu/polyfetcher/schema"
log "github.com/sirupsen/logrus"
"io/ioutil"
"net/http"
"runtime"
"time"
)
/**
// Program to fetch the polygon data of one or more areas
// Not only that, using this you can combine two or more polygons/multipolygon to a Multi polygon
//
// returns polygon if both areas are polygons
// returns Multipolygon if both areas are multi polygons
//
// validate the response using geojsonlint.com or geojson.io. Paste it directly in the textbox to validate it
//
// Note: If you get an error like Polygons and MultiPolygons should follow the right-hand rule then follow this below article to fix it.
//
// https://dev.to/jinagamvasubabu/solution-polygons-and-multipolygons-should-follow-the-right-hand-rule-2c8i
//
// Errors:
// * If one of the area is invalid area then it can fetch the other area if its valid
// * If both are invalid then it will fail using
//
// GoRoutines Support:
// * Instead of getting each and every polygon data synchronously, Time metrics has been logged at the end of the program
//
*/
//IGeometryUtils Program to fetch the polygon data of one or more areas
type IGeometryUtils interface {
FetchPolygons(ctx context.Context, areas []string) ([]schema.GeoJson, error)
CombinePolygons(ctx context.Context, areas []string) (schema.GeoJson, error)
}
//GeometryUtils struct to configure GeometryUtils
type GeometryUtils struct {
LogLevel log.Level
}
//FetchPolygons function gets the definitions from OSM
func (g *GeometryUtils) FetchPolygons(ctx context.Context, areas []string) ([]schema.GeoJson, error) {
log.SetLevel(g.LogLevel)
defer calculateTimeTaken(time.Now(), "Time Taken by Fetch Polygons")
logger := log.WithContext(ctx).WithFields(log.Fields{"Method": "FetchPolygons"})
logger.Infof("Fetching polygons for=%s", areas)
logger.Debugf("GoRoutines count at beginning: %d", runtime.NumGoroutine())
response := []schema.GeoJson{}
response = make([]schema.GeoJson, len(areas))
for a := range areas {
response[a].Coordinates = make([]interface{}, CoordinatesMaxLength) //Initialize with Max number of coordinates array
respList, err := getPolygonDataFromOSM(ctx, areas)
if err != nil {
logger.WithFields(log.Fields{"err": err.Error()}).Error("error while fetching the polygon")
return nil, err
}
for i, result := range respList {
if len(result) > 0 {
geoJSON := result["geojson"].(map[string]interface{})
coordinates := geoJSON["coordinates"].([]interface{})
response[a].Type = geoJSON["type"].(string)
//append based on the type of geojson
if len(areas) == 1 {
response[a].Coordinates = coordinates
} else if i == 0 && response[a].Type == Polygon {
response[a].Coordinates[0] = coordinates
} else if i > 0 && response[a].Type == Polygon {
count := lenOfCoOrdinatesArray(response[a].Coordinates)
response[a].Coordinates[count] = coordinates
} else if response[a].Type == Multipolygon {
count := lenOfCoOrdinatesArray(response[a].Coordinates)
for j := range coordinates {
response[a].Coordinates[count] = coordinates[j]
count++
}
}
}
}
if len(response) > 0 {
removeNilsFromArray(&response[0])
}
}
logger.Debugf("GoRoutines count at last:%d", runtime.NumGoroutine())
return response, nil
}
//CombinePolygons function to combine polygons or multipolygons
func (g *GeometryUtils) CombinePolygons(ctx context.Context, areas []string) (schema.GeoJson, error) {
log.SetLevel(g.LogLevel)
defer calculateTimeTaken(time.Now(), "Time Taken by Fetch Polygons")
logger := log.WithContext(ctx).WithFields(log.Fields{"Method": "CombinePolygons"})
logger.Infof("Combine polygons for=%s", areas)
logger.Debugf("GoRoutines count at beginning: %d", runtime.NumGoroutine())
response := schema.GeoJson{}
response.Coordinates = make([]interface{}, CoordinatesMaxLength) //Initialize with Max number of coordinates array
respList, err := getPolygonDataFromOSM(ctx, areas)
if err != nil {
logger.WithFields(log.Fields{"err": err.Error()}).Error("error while fetching the polygon")
return schema.GeoJson{}, err
}
for i, result := range respList {
geoJSON := result["geojson"].(map[string]interface{})
coordinates := geoJSON["coordinates"].([]interface{})
response.Type = geoJSON["type"].(string)
//append based on the type of geojson
if len(areas) == 1 {
response.Coordinates = coordinates
} else if i == 0 && response.Type == Polygon {
response.Coordinates[0] = coordinates
} else if i > 0 && response.Type == Polygon {
count := lenOfCoOrdinatesArray(response.Coordinates)
response.Coordinates[count] = coordinates
} else if response.Type == Multipolygon {
count := lenOfCoOrdinatesArray(response.Coordinates)
for j := range coordinates {
response.Coordinates[count] = coordinates[j]
count++
}
}
}
if len(areas) > 1 {
response.Type = Multipolygon
}
removeNilsFromArray(&response)
logger.Debugf("GoRoutines count at last:%d", runtime.NumGoroutine())
return response, nil
}
func getPolygonDataFromOSM(ctx context.Context, areas []string) ([]map[string]interface{}, error) {
logger := log.WithContext(ctx).WithFields(log.Fields{"Method": "getPolygonDataFromOSM"})
logger.Infof("getPolygonDataFromOSM for=%s", areas)
var OSMData []map[string]interface{}
c := make(chan schema.OSMStatus)
noOfGoroutines := 0
for _, v := range areas {
go fetchOSMDataFromExternalClient(v, c)
noOfGoroutines++
}
osmStatus := schema.OSMStatus{}
isThereAnyErrorInGoRoutines := false
for i := 0; i < noOfGoroutines; i++ {
osmStatus = <-c
if osmStatus.Error != nil {
isThereAnyErrorInGoRoutines = true
} else {
OSMData = append(OSMData, osmStatus.Result)
}
}
if isThereAnyErrorInGoRoutines && len(OSMData) == 0 {
logger.Error("error while fetching the polygon ")
return nil, errors.New("error while fetching the polygon")
}
return OSMData, nil
}
func fetchOSMDataFromExternalClient(area string, c chan schema.OSMStatus) {
resp, err := http.Get(fmt.Sprintf(OsmURL, area))
if err != nil {
c <- schema.OSMStatus{Error: errors.New("error while fetching the polygon from OSM")}
} else {
defer resp.Body.Close()
}
if resp != nil && resp.Body != nil {
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
c <- schema.OSMStatus{Error: errors.New("no data found in OSM")}
return
}
var results []map[string]interface{}
err = json.Unmarshal(body, &results)
if err != nil {
c <- schema.OSMStatus{Error: errors.New("no data found in OSM")}
return
}
if len(results) == 0 {
c <- schema.OSMStatus{Error: errors.New("no Data available in OSM")}
return
}
geoJSONData := map[string]interface{}{}
for _, r := range results {
geoJSON := r["geojson"].(map[string]interface{})
polygonType := geoJSON["type"].(string)
geoJSONType := r["type"].(string)
if (polygonType == Polygon || polygonType == Multipolygon) && geoJSONType == Administrative {
geoJSONData = r
}
}
c <- schema.OSMStatus{Result: geoJSONData}
}
}
func lenOfCoOrdinatesArray(coOrdinates []interface{}) int32 {
var coOrdinatesLen int32
for _, v := range coOrdinates {
if v == nil {
return coOrdinatesLen
}
coOrdinatesLen++
}
return coOrdinatesLen
}
func removeNilsFromArray(response *schema.GeoJson) {
numOfCoordinates := 0
for _, v := range response.Coordinates {
if v == nil {
break
}
numOfCoordinates++
}
coordinates := make([]interface{}, numOfCoordinates)
coordinates = response.Coordinates[:numOfCoordinates]
response.Coordinates = coordinates
}
func calculateTimeTaken(start time.Time, name string) {
elapsed := time.Since(start)
log.Printf("%s took %s", name, elapsed)
}