{
    "_id" : ObjectId("58da18fb5f2caa20fffa8cf8"),
    "name" : "Barbara Clark",
    "status" : true,
    "location" : {
        "type" : "Point",
        "coordinates" : [
            108.12309125955089,
            -7.421944444444445
        ]
    }
}

// insert dummy location from latitude and longitude.
func insertDummyMarkLocation(cityName string, city *cityModel.City) {
    // some location in Bandung
    lat := -6.8647721
    lon := 107.553501
    var locations []location.Location

    // geneerate location with distance 1 km in every point and limit lenght 50 km.
    // so it will be (50/1)^2 = 2500 district
    newLocations = location.GenerateLocation(lat, lon, 1, 50)
}

Bandung_district_58da0f8a5f2caa20ff61c1a7

type City struct {
    Id       bson.ObjectId `json:"id" bson:"_id,omitempty"`
    Name     string        `json:"name"`
    District int           `json:"district"`
    Location GeoJson       `json:"location"`
}

// get Near district in the city with given distance in meters
func (c *City) GetNearestDistrict(cityName string, lat, lon float64, distance int64) (City, error) {
    var err error
    var city City

    err = checkMongoConnection(mongo)
    if err != nil {
        logger.Println(err)
        return city, err
    }

    collection := mongo.DB("Driver").C(cityName)

    err = collection.Find(bson.M{
        "location": bson.M{
            "$nearSphere": bson.M{
                "$geometry": bson.M{
                    "type":        "Point",
                    "coordinates": []float64{lon, lat}, // lon,lat in order is the rule from mongodb
                },
                "$maxDistance": distance,
            },
        },
    }).One(&city)
    if err != nil {
        logger.Println(err)
        return city, err
    }

    return city, nil
}

type DriverData struct {
    Id       bson.ObjectId `json:"id" bson:"_id,omitempty"`
    Name     string        `json:"name"`
    Status   bool          `json:"status"`
    Location GeoJson       `json:"location"`
}

// struct for storing geo location in mongodb
type GeoJson struct {
    Type        string    `json:"type"`
    Coordinates []float64 `json:"coordinates"`
}

// Get available driver from given cityName and idDistrict/marked location.
func (d *DriverData) GetAvailableDriver(city, idDistrict string) []DriverData {
    collectionKey := getFormatDistrict(city, idDistrict)

    collection := mongo.DB("Driver").C(collectionKey)

    var drivers []DriverData
    err := collection.Find(bson.M{
        "status": true,
    }).Limit(100).All(&drivers)

    if err != nil {
        logger.Println(err)
    }

    return drivers
}