feat: Add sing-geoip database support

component/mmdb/reader.go

@@ -0,0 +1,36 @@
+package mmdb
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/oschwald/maxminddb-golang"
+)
+
+type geoip2Country struct {
+	Country struct {
+		IsoCode string `maxminddb:"iso_code"`
+	} `maxminddb:"country"`
+}
+
+type Reader struct {
+	*maxminddb.Reader
+	databaseType
+}
+
+func (r Reader) LookupCode(ipAddress net.IP) string {
+	switch r.databaseType {
+	case typeMaxmind:
+		var country geoip2Country
+		_ = r.Lookup(ipAddress, &country)
+		return country.Country.IsoCode
+
+	case typeSing:
+		var code string
+		_ = r.Lookup(ipAddress, &code)
+		return code
+
+	default:
+		panic(fmt.Sprint("unknown geoip database type:", r.databaseType))
+	}
+}