package geoip

import (
	_ "embed"
	"net"

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

//go:embed dbip-country-lite.mmdb
var mmdbData []byte

// Reader provides country-level GeoIP lookups using an embedded DB-IP Lite database.
type Reader struct {
	db *maxminddb.Reader
}

// New opens the embedded MMDB and returns a ready-to-use Reader.
func New() (*Reader, error) {
	db, err := maxminddb.FromBytes(mmdbData)
	if err != nil {
		return nil, err
	}
	return &Reader{db: db}, nil
}

type countryRecord struct {
	Country struct {
		ISOCode string `maxminddb:"iso_code"`
	} `maxminddb:"country"`
}

// Lookup returns the ISO 3166-1 alpha-2 country code for the given IP address,
// or an empty string if the lookup fails or no result is found.
func (r *Reader) Lookup(ipStr string) string {
	ip := net.ParseIP(ipStr)
	if ip == nil {
		return ""
	}

	var record countryRecord
	if err := r.db.Lookup(ip, &record); err != nil {
		return ""
	}
	return record.Country.ISOCode
}

// Close releases resources held by the reader.
func (r *Reader) Close() error {
	return r.db.Close()
}