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
}