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