mapquest_geocoder.go

package geo

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"strconv"
)

// This struct contains all the funcitonality
// of interacting with the MapQuest Geocoding Service
type MapQuestGeocoder struct{}

type mapQuestGeocodeResponse struct {
	BoundingBox []string `json:"boundingbox"`
	Lat         string
	Lng         string `json:"lon"`
	DisplayName string `json:"display_name"`
}

type mapQuestReverseGeocodeResponse struct {
	Address struct {
		Road        string
		City        string
		State       string
		PostCode    string `json:"postcode"`
		CountryCode string `json:"country_code"`
	}
}

// This is the error that consumers receive when there
// are no results from the geocoding request.
var mapquestZeroResultsError = errors.New("ZERO_RESULTS")

var MapquestAPIKey = ""

// This contains the base URL for the Mapquest Geocoder API.
var mapquestGeocodeURL = "http://open.mapquestapi.com/nominatim/v1"

func SetMapquestAPIKey(newAPIKey string) {
	MapquestAPIKey = newAPIKey
}

// Note:  In the next major revision (1.0.0), it is planned
//        That Geocoders should adhere to the `geo.Geocoder`
//        interface and provide versioning of APIs accordingly.
// Sets the base URL for the MapQuest Geocoding API.
func SetMapquestGeocodeURL(newGeocodeURL string) {
	mapquestGeocodeURL = newGeocodeURL
}

// Issues a request to the open mapquest api geocoding services using the passed in url query.
// Returns an array of bytes as the result of the api call or an error if one occurs during the process.
// Note: Since this is an arbitrary request, you are responsible for passing in your API key if you want one.
func (g *MapQuestGeocoder) Request(url string) ([]byte, error) {
	client := &http.Client{}
	fullUrl := fmt.Sprintf("%s/%s", mapquestGeocodeURL, url)

	// TODO Refactor into an api driver of some sort
	//      It seems odd that golang-geo should be responsible of versioning of APIs, etc.
	req, _ := http.NewRequest("GET", fullUrl, nil)
	resp, requestErr := client.Do(req)

	if requestErr != nil {
		return nil, requestErr
	}

	// TODO figure out a better typing for response
	data, dataReadErr := ioutil.ReadAll(resp.Body)

	if dataReadErr != nil {
		return nil, dataReadErr
	}

	return data, nil
}

// Returns the first point returned by MapQuest's geocoding service or an error
// if one occurs during the geocoding request.
func (g *MapQuestGeocoder) Geocode(address string) (*Point, error) {

	queryStr, err := mapquestGeocodeQueryStr(address)
	if err != nil {
		return nil, err
	}

	data, err := g.Request(queryStr)
	if err != nil {
		return nil, err
	}

	res := []*mapQuestGeocodeResponse{}
	json.Unmarshal(data, &res)

	if len(res) == 0 {
		return &Point{}, mapquestZeroResultsError
	}

	lat, err := strconv.ParseFloat(res[0].Lat, 64)
	if err != nil {
		return nil, err
	}

	lng, err := strconv.ParseFloat(res[0].Lng, 64)
	if err != nil {
		return nil, err
	}

	p := &Point{
		lat: lat,
		lng: lng,
	}

	return p, nil
}

func mapquestGeocodeQueryStr(address string) (string, error) {
	url_safe_query := url.QueryEscape(address)

	var queryBuf = bytes.NewBufferString("search.php?")
	_, err := queryBuf.WriteString(fmt.Sprintf("q=%s", url_safe_query))
	if err != nil {
		return "", err
	}

	if MapquestAPIKey != "" {
		_, err := queryBuf.WriteString(fmt.Sprintf("&key=%s", MapquestAPIKey))
		if err != nil {
			return "", err
		}
	}

	_, err = queryBuf.WriteString("&format=json")
	if err != nil {
		return "", err
	}

	return queryBuf.String(), err
}

// Returns the first most available address that corresponds to the passed in point.
// It may also return an error if one occurs during execution.
func (g *MapQuestGeocoder) ReverseGeocode(p *Point) (string, error) {
	queryStr, err := mapquestReverseGeocodeQueryStr(p)
	if err != nil {
		return "", err
	}

	data, err := g.Request(queryStr)
	if err != nil {
		return "", err
	}

	res := []*mapQuestReverseGeocodeResponse{}
	err = json.Unmarshal(data, &res)
	if err != nil {
		return "", err
	}

	road := res[0].Address.Road
	city := res[0].Address.City
	state := res[0].Address.State
	postcode := res[0].Address.PostCode
	countryCode := res[0].Address.CountryCode

	resStr := fmt.Sprintf("%s %s %s %s %s", road, city, state, postcode, countryCode)
	return resStr, nil
}

func mapquestReverseGeocodeQueryStr(p *Point) (string, error) {
	var queryBuf = bytes.NewBufferString("reverse.php?")

	_, err := queryBuf.WriteString(fmt.Sprintf("lat=%f&lng=%f", p.lat, p.lng))
	if err != nil {
		return "", err
	}

	if MapquestAPIKey != "" {
		_, err := queryBuf.WriteString(fmt.Sprintf("&key=%s", MapquestAPIKey))
		if err != nil {
			return "", err
		}
	}

	_, err = queryBuf.WriteString("&format=json")
	if err != nil {
		return "", err
	}

	return queryBuf.String(), err
}