chore: move code around

app/internal/utils/geoip.go

@@ -0,0 +1,70 @@
+package utils
+
+import (
+	"io"
+	"net/http"
+	"os"
+
+	"github.com/oschwald/geoip2-golang"
+)
+
+const (
+	geoipDefaultFilename = "GeoLite2-Country.mmdb"
+	geoipDownloadURL     = "https://git.io/GeoLite2-Country.mmdb"
+)
+
+// GeoIPLoader provides the on-demand GeoIP database loading function required by the ACL engine.
+type GeoIPLoader struct {
+	Filename        string
+	DownloadFunc    func(filename, url string) // Called when downloading the GeoIP database.
+	DownloadErrFunc func(err error)            // Called when downloading the GeoIP database succeeds/fails.
+
+	db *geoip2.Reader
+}
+
+func (l *GeoIPLoader) download() error {
+	resp, err := http.Get(geoipDownloadURL)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	f, err := os.Create(geoipDefaultFilename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	_, err = io.Copy(f, resp.Body)
+	return err
+}
+
+func (l *GeoIPLoader) Load() *geoip2.Reader {
+	if l.db == nil {
+		if l.Filename == "" {
+			// Filename not specified, try default.
+			if _, err := os.Stat(geoipDefaultFilename); err == nil {
+				// Default already exists, just use it.
+				l.Filename = geoipDefaultFilename
+			} else if os.IsNotExist(err) {
+				// Default doesn't exist, download it.
+				l.DownloadFunc(geoipDefaultFilename, geoipDownloadURL)
+				err := l.download()
+				l.DownloadErrFunc(err)
+				if err != nil {
+					return nil
+				}
+				l.Filename = geoipDefaultFilename
+			} else {
+				// Other error
+				return nil
+			}
+		}
+		db, err := geoip2.Open(l.Filename)
+		if err != nil {
+			return nil
+		}
+		l.db = db
+	}
+	return l.db
+}