package reality

import (
	"net"

	"github.com/oschwald/geoip2-golang"
)

// GeoResolver performs GeoIP country lookups using a MaxMind MMDB file.
type GeoResolver struct {
	reader *geoip2.Reader
}

// NewGeoResolver opens an MMDB file for country lookups.
// Returns nil resolver (not an error) if path is empty — callers get "N/A" for all lookups.
func NewGeoResolver(mmdbPath string) (*GeoResolver, error) {
	if mmdbPath == "" {
		return nil, nil
	}
	reader, err := geoip2.Open(mmdbPath)
	if err != nil {
		return nil, err
	}
	return &GeoResolver{reader: reader}, nil
}

// Lookup returns the ISO country code for an IP, or "N/A" if unavailable.
func (g *GeoResolver) Lookup(ip net.IP) string {
	if g == nil || g.reader == nil {
		return "N/A"
	}
	record, err := g.reader.Country(ip)
	if err != nil || record.Country.IsoCode == "" {
		return "N/A"
	}
	return record.Country.IsoCode
}

// Close releases the MMDB reader resources.
func (g *GeoResolver) Close() {
	if g != nil && g.reader != nil {
		g.reader.Close()
	}
}