Reverse Geocode NOAA station coordinates

main.go

package main

import (
	"context"
	"encoding/csv"
	"fmt"
	"log"
	"os"
	"sync"
	"time"

	"cloud.google.com/go/bigquery"
	"google.golang.org/api/iterator"

	"googlemaps.github.io/maps"
)

type station struct {
	Usaf string
	Lat  float64
	Lon  float64
}

func main() {
	os.Remove("result.csv")
	file, err := os.Create("result.csv")
	checkError("Cannot create file", err)
	defer file.Close()

	writer := csv.NewWriter(file)
	defer writer.Flush()

	ctx := context.Background()
	client, err := bigquery.NewClient(ctx, os.Getenv("GCP_PROJECT_ID"))
	q := client.Query("SELECT usaf, lat, lon FROM `bigquery-public-data.noaa_gsod.stations` WHERE country='US'")
	q.Location = "US"
	job, err := q.Run(ctx)
	if err != nil {
		checkError("", err)
	}
	status, err := job.Wait(ctx)
	if err != nil {
		checkError("", err)
	}
	if err := status.Err(); err != nil {
		checkError("", err)
	}

	it, err := q.Read(ctx)
	if err != nil {
		checkError("", err)
	}

	rows := []station{}
	for {
		var row station
		err := it.Next(&row)
		if err == iterator.Done {
			break
		}
		if err != nil {
			checkError("", err)
		}
		rows = append(rows, row)
	}

	mapsClient, err := maps.NewClient(maps.WithAPIKey(os.Getenv("GOOGLE_MAPS_KEY")))
	if err != nil {
		checkError("", err)
	}

	results := [][]string{[]string{
		"StationNumber",
		"Lat",
		"Lon",
		"Address",
		"State",
		"City",
		"County",
		"Zip"}}

	rate := time.Second / 10
	throttle := time.Tick(rate)
	var wg sync.WaitGroup

	for _, row := range rows {
		<-throttle
		wg.Add(1)

		go func(row station) {
			defer wg.Done()

			req := &maps.GeocodingRequest{
				LatLng: &maps.LatLng{row.Lat, row.Lon},
			}
			extractResult, err := mapsClient.Geocode(ctx, req)
			if err != nil {
				log.Println(err.Error())
				return
			}
			if len(extractResult) == 0 {
				log.Println("GeocodingResults is empty")
				return
			}
			geocoding := extractResult[0]
			result := []string{
				row.Usaf,
				fmt.Sprintf("%f", row.Lat),
				fmt.Sprintf("%f", row.Lon),
				geocoding.FormattedAddress,
				compString(geocoding.AddressComponents, "administrative_area_level_1", true),
				compString(geocoding.AddressComponents, "locality", false),
				compString(geocoding.AddressComponents, "administrative_area_level_2", true),
				compString(geocoding.AddressComponents, "postal_code", true),
			}
			results = append(results, result)
		}(row)
	}
	wg.Wait()

	for _, value := range results {
		err := writer.Write(value)
		checkError("Cannot write to file", err)
	}
}

func compString(comps []maps.AddressComponent, typ string, short bool) string {
	for _, comp := range comps {
		for _, t := range comp.Types {
			if t == typ {
				var val string
				if short {
					val = comp.ShortName
				} else {
					val = comp.LongName
				}
				return val
			}
		}
	}

	return ""
}

func checkError(message string, err error) {
	if err != nil {
		log.Fatal(message, err)
	}
}