parse-geojson.go

package main

import (
"encoding/json"
"fmt"
"io/ioutil"
"os"
)

// Property Geojson Property
typePropertystruct {
IDstring`json:"id"`
Typestring`json:"type"`
Highwaystring`json:"highway"`
Accessstring`json:"access"`
Litstring`json:"lit"`
Sidewalkstring`json:"sidewalk"`
}

// Coordinate pair of lng, lat
typeCoordinate [2]float64

// Geometry Geojson Geometry
typeGeometrystruct {
Typestring`json:"type"`
Coordinates []Coordinate`json:"coordinates"`
}

// Feature Geojson Feature
typeFeaturestruct {
Typestring`json:"type"`
IDstring`json:"id"`
PropertiesProperty`json:"properties"`
GeometryGeometry`json:"geometry"`
}

// GeoJSON data structure
typeGeoJSONstruct {
Typestring`json:"type"`
Features []Feature`json:"features"`
}

funccreateGraph(geojsonGeoJSON) Graph {
vargraphGraph
graph.Init()
fori:=0; i<len(geojson.Features); i++ {
varfeature=geojson.Features[i]
varprev*Node
forj:=0; j<len(feature.Geometry.Coordinates); j++ {
varcoords=feature.Geometry.Coordinates[j]
node:=Node{coords[0], coords[1]}
ifj!=0 {
graph.AddEdge(node, prev)
graph.AddEdge(*prev, &node)
 }
prev=&node
 }
 }
fmt.Println("geojson Graph created with", len(graph.edges), "nodes and", graph.numEdges, "edges")
returngraph
}

funcloadGeoJSON(filenamestring) Graph {
// GeoJSON for Greater London
// from http://download.geofabrik.de/europe/great-britain/england/greater-london.html
// geoJsonDownloadLink := "https://ucb7e1be7e59700bb615fc052d06.dl.dropboxusercontent.com/cd/0/get/ApeoomlSroMi4LLrd88j2O1YyfZcz-fnOcR-BMu7Ca3F-aclMpnyLmlzJPZtgze6QSfiGh_SZAcCl-TzGSrcNR14iFsaOBl-vs7CsUzWnL6UbsaH7V_CR-apDThjG8fUH78/file?dl=1DownloadLink"
// resp, err := http.Get(geoJsonDownloadLink)
// if err != nil {
// // handle error
// }
// defer resp.Body.Close()
// jsonFile := resp.Body
// GeoJSON for central london around highbury islington
// jsonFile, err := os.Open("./data/central.geojson")
// jsonFile, err := os.Open("./data/greater-london-latest.geojson")
// 2.73GB
jsonFile, err:=os.Open(filename)
iferr!=nil {
fmt.Println(err)
 }
fmt.Println("Successfully Opened geojson")
byteValue, _:=ioutil.ReadAll(jsonFile)
fmt.Println("Successfully ReadAll geojson")
vargeojsonGeoJSON
json.Unmarshal(byteValue, &geojson)
fmt.Println("Successfully Unmarshalled geojson with N features", len(geojson.Features))

deferjsonFile.Close()
returncreateGraph(geojson)
}