simple geo ip server

internal/geo/resolver.go

@@ -0,0 +1,80 @@
+package geo
+
+import (
+	"errors"
+	"net"
+	"strings"
+
+	"github.com/oschwald/geoip2-golang"
+)
+
+// ErrInvalidIP is returned when an IP cannot be parsed.
+var ErrInvalidIP = errors.New("invalid ip address")
+
+type Resolver struct {
+	db *geoip2.Reader
+}
+
+type Location struct {
+	IP        string
+	Country   string
+	Region    string
+	City      string
+	Address   string
+	Latitude  float64
+	Longitude float64
+}
+
+func NewResolver(dbPath string) (*Resolver, error) {
+	if dbPath == "" {
+		return nil, errors.New("db path is required")
+	}
+
+	db, err := geoip2.Open(dbPath)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Resolver{db: db}, nil
+}
+
+func (r *Resolver) Close() error {
+	return r.db.Close()
+}
+
+func (r *Resolver) Lookup(ipStr string) (Location, error) {
+	ip := net.ParseIP(ipStr)
+	if ip == nil {
+		return Location{}, ErrInvalidIP
+	}
+
+	record, err := r.db.City(ip)
+	if err != nil {
+		return Location{}, err
+	}
+
+	country := record.Country.Names["en"]
+	region := ""
+	if len(record.Subdivisions) > 0 {
+		region = record.Subdivisions[0].Names["en"]
+	}
+
+	city := record.City.Names["en"]
+
+	addressParts := make([]string, 0, 3)
+	for _, part := range []string{city, region, country} {
+		if part != "" {
+			addressParts = append(addressParts, part)
+		}
+	}
+
+	return Location{
+		IP:        ip.String(),
+		Country:   country,
+		Region:    region,
+		City:      city,
+		Address:   strings.Join(addressParts, ", "),
+		Latitude:  record.Location.Latitude,
+		Longitude: record.Location.Longitude,
+	}, nil
+}