http proxy

package main

import (
	"flag"
	"fmt"
	"io"
	"net"
	"net/http"
	"strings"
)

var (
	lAddr = flag.String("l", ":7001", "listen addr")
)

func handle(client net.Conn) {
	defer client.Close()

	fmt.Printf("remote addr: %v\n", client.RemoteAddr())

	buf := make([]byte, 1024)

	n, err := client.Read(buf)
	if err != nil {
		fmt.Println(err)
		return
	}

	s := string(buf)
	lines := strings.Split(s, "\r\n")

	firtstLineParts := strings.Split(lines[0], " ")
	method, path := firtstLineParts[0], firtstLineParts[1]
	if err != nil {
		fmt.Println(err)
		return
	}

	address := ""
	if method == http.MethodConnect {
		client.Write([]byte("HTTP/1.1 200 Connection established\r\n\r\n"))
		address = path
	} else {
		address = strings.Split(strings.TrimPrefix(path, "http://"), "/")[0]
	}

	if strings.Index(address, ":") == -1 {
		address += ":80"
	}

	server, err := net.Dial("tcp", address)
	if err != nil {
		fmt.Println(err)
		return
	}

	if method != http.MethodConnect {
		server.Write(buf[:n])
	}

	go io.Copy(client, server)
	io.Copy(server, client)

}

func main() {
	flag.Parse()

	listen, _ := net.Listen("tcp", *lAddr)

	for {
		conn, _ := listen.Accept()
		go handle(conn)
	}

}