package main

import (
	"bytes"
	"fmt"
	"log"
	"net"
)

var buff = make([]byte, 1000, 1000)

func main() {
	log.SetFlags(log.LstdFlags | log.Lshortfile)
	l, err := net.Listen("tcp", ":8081")
	if err != nil {
		log.Panic(err)
	}
	for {
		client, err := l.Accept()
		if err != nil {
			log.Panic(err)
		}
		go handleClientRequest(client)
	}
}
func handleClientRequest(client net.Conn) {
	if client == nil {
		return
	}
	defer client.Close()
	buff = buff[:0]
	buff = buff[:cap(buff)]
	c, err := client.Read(buff)
	if err != nil {
		log.Println(err)
	}
	log.Printf("%s", buff)
	var method, host, protocol string
	fmt.Sscanf(string(buff[:bytes.IndexByte(buff, '\n')]), "%s %s %s", &method, &host, &protocol)
	//获得了请求的host和port，就开始拨号吧
	server, err := net.Dial("tcp", host)
	if err != nil {
		log.Println(err)
	}
	if method == "CONNECT" {
		fmt.Fprint(client, "HTTP/1.1 200 Connection established\r\n\r\n")
	} else {
		server.Write(buff[:c])
	}
	//进行转发
	go io.Copy(server, client)
	io.Copy(client, server)
}