// Package geoip provides IP address geolocation features.
package geoip

import (
	"errors"
	"net"
	"net/http"
	"strings"

	"code.nonshy.com/nonshy/website/pkg/config"
	"code.nonshy.com/nonshy/website/pkg/utility"
	"github.com/oschwald/geoip2-golang"
)

// GetRequestCity returns the GeoIP City result for the current HTTP request.
func GetRequestCity(r *http.Request) (*geoip2.City, error) {
	var (
		addr = utility.IPAddress(r)
		ip   = net.ParseIP(addr)
	)
	return GetCity(ip)
}

// GetRequestCountryFlag returns the country flag based on the current HTTP request IP address.
func GetRequestCountryFlag(r *http.Request) (string, error) {
	city, err := GetRequestCity(r)
	if err != nil {
		// If the remote addr is localhost (local dev testing), default to US flag.
		if addr := utility.IPAddress(r); addr == "127.0.0.1" || addr == "::1" {
			return CountryFlagEmoji("US")
		}

		return "", err
	}

	return CountryFlagEmoji(city.Country.IsoCode)
}

// GetRequestCountryFlagWithCode returns the flag joined with the country code by a space (like CountryFlagEmojiWithCode).
func GetRequestCountryFlagWithCode(r *http.Request) (string, error) {
	city, err := GetRequestCity(r)
	if err != nil {
		// If the remote addr is localhost (local dev testing), default to US flag.
		if addr := utility.IPAddress(r); addr == "127.0.0.1" || addr == "::1" {
			return CountryFlagEmojiWithCode("US")
		}

		return "", err
	}

	return CountryFlagEmojiWithCode(city.Country.IsoCode)
}

// GetCity queries the GeoIP database for city information for an IP address.
func GetCity(ip net.IP) (*geoip2.City, error) {
	db, err := geoip2.Open(config.GeoIPPath)
	if err != nil {
		return nil, err
	}

	return db.City(ip)
}

// CountryFlagEmoji returns the emoji sequence for a country flag based on
// the two-letter country code.
func CountryFlagEmoji(alpha2 string) (string, error) {
	if len(alpha2) != 2 {
		return "", errors.New("country code must be two letters long")
	}

	alpha2 = strings.ToLower(alpha2)

	var (
		flagBaseIndex = '\U0001F1E6' - 'a'
		box           = func(ch byte) string {
			return string(rune(ch) + flagBaseIndex)
		}
	)

	return string(box(alpha2[0]) + box(alpha2[1])), nil
}

// CountryFlagEmojiWithCode returns a string consisting of the country flag, a space, and the alpha2 code passed in.
func CountryFlagEmojiWithCode(alpha2 string) (string, error) {
	if emoji, err := CountryFlagEmoji(alpha2); err != nil {
		return emoji, err
	} else {
		return emoji + " " + alpha2, nil
	}
}