qba73/geonames

package geonames

import (
    "context"
    "encoding/json"
    "fmt"
    "io"
    "net/http"
    "os"
    "time"
)

// Client holds data required for communicating with the Geonames Web Services.
type Client struct {
    UserName   string
    UserAgent  string
    BaseURL    string
    HTTPClient *http.Client

    // Optional HTTP headers to set for each API request.
    Headers map[string][]string
}

const (
    libraryVersion = "0.1"
    userAgent      = "geonames/" + libraryVersion
)

// NewClient creates a new client for GeoNames Web service.
//
// The username has to be registered at the GeoNames.org website.
// HTTP requests without a valid username will return 403 HTTP errors.
func NewClient(username string) *Client {
    c := Client{
        UserName:  username,
        UserAgent: userAgent,
        BaseURL:   "http://api.geonames.org",
        HTTPClient: &http.Client{
            Timeout: time.Second * 5,
        },
        Headers: map[string][]string{
            "User-Agent":   {userAgent},
            "Content-Type": {"application/json"},
        },
    }
    return &c
}

func (c Client) get(ctx context.Context, url string, data any) error {
    req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
    if err != nil {
        return fmt.Errorf("creating request: %w", err)
    }
    res, err := c.HTTPClient.Do(req)
    if err != nil {
        return fmt.Errorf("sending GET request: %w", err)
    }
    defer res.Body.Close()

    if res.StatusCode != http.StatusOK {
        return fmt.Errorf("got response code: %v", res.StatusCode)
    }

    body, err := io.ReadAll(res.Body)
    if err != nil {
        return fmt.Errorf("reading response body: %w", err)
    }

    if err := json.Unmarshal(body, data); err != nil {
        return fmt.Errorf("unmarshaling response body: %w", err)
    }
    return nil
}

// Position holds information about Lat and Long.
type Position struct {
    Lat float64
    Lng float64
}

var DemoClient = &Client{
    UserName:   "demo",
    BaseURL:    "http://api.geonames.org",
    HTTPClient: http.DefaultClient,
    Headers: map[string][]string{
        "Content-Type": {"application/json"},
    },
}

var ClientFromEnv = &Client{
    UserName: os.Getenv("GEONAMES_USER"),
    BaseURL:  "http://api.geonames.org",
    HTTPClient: &http.Client{
        Timeout: 10 * time.Second,
    },
    Headers: map[string][]string{
        "Content-Type": {"application/json"},
    },
}