package main

import (
	"log"
	"crypto/tls"
	"net"
)

const localAddr string = "127.0.0.1:9999"
const remoteAddr string = "127.0.0.1:25500"
const MaxConn int16 = 3

func proxyConn(conn net.Conn) {
	defer conn.Close()

	rAddr, err := net.ResolveTCPAddr("tcp", remoteAddr)
	if err != nil {
		log.Print(err)
	}

	conf := &tls.Config{
		InsecureSkipVerify: true,
	}

	//rConn, err := net.DialTCP("tcp", nil, rAddr)
	rConn, err := tls.Dial("tcp", rAddr.String(), conf)
	if err != nil {
		log.Print(err)
		return
	}
	defer rConn.Close()

//	log.Printf("remoteAddr connected: %v\n", rAddr.String())

	Pipe(conn, rConn)
//	log.Printf("proxyConn end: %v -> %v\n", conn.RemoteAddr(), rConn.RemoteAddr())
}

func chanFromConn(conn net.Conn) chan []byte {
	c := make(chan []byte)

	go func() {
		b := make([]byte, 1024)

		for {
			n, err := conn.Read(b)
			if n > 0 {
				res := make([]byte, n)
				// Copy the buffer so it doesn't get changed while read by the recipient.
				copy(res, b[:n])
				c <- res
			}
			if err != nil {
				c <- nil
				break
			}
		}
	}()

	return c
}

func Pipe(conn1 net.Conn, conn2 net.Conn) {
	chan1 := chanFromConn(conn1)
	chan2 := chanFromConn(conn2)

	for {
		select {
		case b1 := <-chan1:
			if b1 == nil {
				return
			} else {
				conn2.Write(b1)
			}
		case b2 := <-chan2:
			if b2 == nil {
				return
			} else {
				conn1.Write(b2)
			}
		}
	}
}

func main() {
	log.SetFlags(log.Lshortfile)

	log.Printf("Listening: %v -> %v\n\n", localAddr, remoteAddr)

	addr, err := net.ResolveTCPAddr("tcp", localAddr)
	if err != nil {
		panic(err)
	}

	listener, err := net.ListenTCP("tcp", addr)
	if err != nil {
		panic(err)
	}

	var i int16 = 0;
	count := make(chan int16, 1)
	for {
		log.Printf("wait accepted...\n")
		conn, err := listener.AcceptTCP()
		if err != nil {
			log.Print(err)
		}
		//go proxyConn(conn);
		
		//log.Printf("accepted: %v\n", conn.RemoteAddr())
		select {
			case t := <- count:
				i += t 
//				print("received ", i, "\n")

			default:
				
		}
		if i < MaxConn {
			i++
			log.Printf("[%v/%v]accepted: %v\n", i, MaxConn, conn.RemoteAddr())

			// Create a new goroutine which will call the connection handler and  then free up the space.
			go func(connection net.Conn) {
				proxyConn(connection)
//				log.Printf("[%v/%v]Closed connection from %s\r\n", i, MaxConn, connection.RemoteAddr())
				log.Printf("Closed connection from %s\r\n", connection.RemoteAddr())
				select {
					case t := <- count:
						count <- t-1 

					default:
						count <- -1
				}
			}(conn)
		}else{
			conn.Close()
//			log.Printf("closed: %v\n", i)
		}
	}

}