geocoding.go

package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"time"
)

type Location struct {
	Lat string `json:"lat"`
	Lon string `json:"lon"`
	DisplayName string `json:"display_name"`
}

func getCoordinates(city, country string) (float64, float64, string, error) {
	query := fmt.Sprintf("%s, %s", city, country)
	u, err := url.Parse("https://nominatim.openstreetmap.org/search")
	if err != nil {
		return 0, 0, "", err
	}

	q := u.Query()
	q.Set("q", query)
	q.Set("format", "json")
	q.Set("limit", "1")
	u.RawQuery = q.Encode()

	req, err := http.NewRequest("GET", u.String(), nil)
	if err != nil {
		return 0, 0, "", err
	}
	req.Header.Set("User-Agent", "CartoGo/1.0")

	client := &http.Client{Timeout: 10 * time.Second}
	resp, respErr := client.Do(req)
	if respErr != nil {
		return 0, 0, "", respErr
	}
	defer resp.Body.Close()

	var locations []Location
	if err := json.NewDecoder(resp.Body).Decode(&locations); err != nil {
		return 0, 0, "", err
	}

	if len(locations) == 0 {
		return 0, 0, "", fmt.Errorf("could not find coordinates for %s, %s", city, country)
	}

	var lat, lon float64
	fmt.Sscanf(locations[0].Lat, "%f", &lat)
	fmt.Sscanf(locations[0].Lon, "%f", &lon)

	return lat, lon, locations[0].DisplayName, nil
}