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// Copyright (c) 2017 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package geo
import (
"reflect"
"strings"
)
// ExtractGeoPoint takes an arbitrary interface{} and tries it's best to
// interpret it is as geo point. Supported formats:
// Container:
// slice length 2 (GeoJSON)
// first element lon, second element lat
// map[string]interface{}
// exact keys lat and lon or lng
// struct
// w/exported fields case-insensitive match on lat and lon or lng
// struct
// satisfying Later and Loner or Lnger interfaces
//
// in all cases values must be some sort of numeric-like thing: int/uint/float
func ExtractGeoPoint(thing interface{}) (lon, lat float64, success bool) {
var foundLon, foundLat bool
thingVal := reflect.ValueOf(thing)
thingTyp := thingVal.Type()
// is it a slice
if thingVal.IsValid() && thingVal.Kind() == reflect.Slice {
// must be length 2
if thingVal.Len() == 2 {
first := thingVal.Index(0)
if first.CanInterface() {
firstVal := first.Interface()
lon, foundLon = extractNumericVal(firstVal)
}
second := thingVal.Index(1)
if second.CanInterface() {
secondVal := second.Interface()
lat, foundLat = extractNumericVal(secondVal)
}
}
}
// is it a map
if l, ok := thing.(map[string]interface{}); ok {
if lval, ok := l["lon"]; ok {
lon, foundLon = extractNumericVal(lval)
} else if lval, ok := l["lng"]; ok {
lon, foundLon = extractNumericVal(lval)
}
if lval, ok := l["lat"]; ok {
lat, foundLat = extractNumericVal(lval)
}
}
// now try reflection on struct fields
if thingVal.IsValid() && thingVal.Kind() == reflect.Struct {
for i := 0; i < thingVal.NumField(); i++ {
fieldName := thingTyp.Field(i).Name
if strings.HasPrefix(strings.ToLower(fieldName), "lon") {
if thingVal.Field(i).CanInterface() {
fieldVal := thingVal.Field(i).Interface()
lon, foundLon = extractNumericVal(fieldVal)
}
}
if strings.HasPrefix(strings.ToLower(fieldName), "lng") {
if thingVal.Field(i).CanInterface() {
fieldVal := thingVal.Field(i).Interface()
lon, foundLon = extractNumericVal(fieldVal)
}
}
if strings.HasPrefix(strings.ToLower(fieldName), "lat") {
if thingVal.Field(i).CanInterface() {
fieldVal := thingVal.Field(i).Interface()
lat, foundLat = extractNumericVal(fieldVal)
}
}
}
}
// last hope, some interfaces
// lon
if l, ok := thing.(loner); ok {
lon = l.Lon()
foundLon = true
} else if l, ok := thing.(lnger); ok {
lon = l.Lng()
foundLon = true
}
// lat
if l, ok := thing.(later); ok {
lat = l.Lat()
foundLat = true
}
return lon, lat, foundLon && foundLat
}
// extract numeric value (if possible) and returns a float64
func extractNumericVal(v interface{}) (float64, bool) {
val := reflect.ValueOf(v)
typ := val.Type()
switch typ.Kind() {
case reflect.Float32, reflect.Float64:
return val.Float(), true
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return float64(val.Int()), true
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return float64(val.Uint()), true
}
return 0, false
}
// various support interfaces which can be used to find lat/lon
type loner interface {
Lon() float64
}
type later interface {
Lat() float64
}
type lnger interface {
Lng() float64
}
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