package main

import (
	"errors"
	"fmt"
	"net"
	"os"
	"time"

	"github.com/codegangsta/cli"
	"github.com/cydev/stun"
)

var (
	serverAddress string
)

func discover(c *cli.Context) error {
	conn, err := net.Dial("udp", serverAddress)
	if err != nil {
		return err
	}
	m := stun.AcquireMessage()
	m.Type = stun.MessageType{Method: stun.MethodBinding, Class: stun.ClassRequest}
	m.TransactionID = stun.NewTransactionID()
	m.AddSoftware("cydev/stun alpha")
	m.WriteHeader()
	timeout := 100 * time.Millisecond
	for i := 0; i < 9; i++ {
		_, err := m.WriteTo(conn)
		if err != nil {
			return err
		}
		if err = conn.SetReadDeadline(time.Now().Add(timeout)); err != nil {
			return err
		}
		if timeout < 1600*time.Millisecond {
			timeout *= 2
		}
		var (
			ip   net.IP
			port int
		)
		if err == nil {
			mRec := stun.AcquireMessage()
			if _, err = mRec.ReadFrom(conn); err != nil {
				return err
			}
			if mRec.TransactionID != m.TransactionID {
				return errors.New("TransactionID missmatch")
			}
			ip, port, err = mRec.GetXORMappedAddress()
			if err != nil {
				return err
			}
			fmt.Println(ip, port)
			stun.ReleaseMessage(mRec)
			break
		} else {
			if !err.(net.Error).Timeout() {
				return err
			}
		}
	}
	return nil
}

func main() {
	app := cli.NewApp()
	app.Name = "stun"
	app.Usage = "command line client for STUN"
	app.Flags = []cli.Flag{
		cli.StringFlag{
			Name:        "server",
			Value:       "stun.l.google.com:19302",
			Usage:       "STUN serve address",
			Destination: &serverAddress,
		},
	}
	app.Action = discover

	app.Run(os.Args)
}