package main

import (
	"net/http"
	"net"
	"strings"	
        "encoding/base32"
	"os"
)

// DomainFromIP derives a meshname subdomain for the authoritative DNS server address
func DomainFromIP(target net.IP) string {
        host := strings.ToLower(base32.StdEncoding.EncodeToString(target)[0:26])
	tld := ".mesh.cat"
	domain := strings.Join([]string{host, tld}, "")
	return domain
}

func handler(w http.ResponseWriter, r *http.Request) {
	ip, port, err := net.SplitHostPort(r.RemoteAddr)
	_, _ = port, err	
	parsedIP := net.ParseIP(ip)
	// return domain for IPv6 only
	if parsedIP.To4() == nil {
		w.Write([]byte(DomainFromIP(parsedIP)))
	}
}

func main() {
	http.HandleFunc("/", handler)
	listenPort := "3000"
	// Get the first command-line argument
	if len(os.Args) > 1 {
		listenPort = os.Args[1]
	}
	print("Listening on port:", listenPort, "\n")
	listenPort = strings.Join([]string{":", listenPort}, "")
	http.ListenAndServe(listenPort, nil)
}