package proxy

import (
	"io"
	"log"
	"net"
	"net/http"
	"time"
)

type Options struct {
	Addr string
}

type Proxy struct {
	Server *http.Server
}

func (proxy *Proxy) Start() error {
	log.Printf("Proxy start listen at %v\n", proxy.Server.Addr)
	return proxy.Server.ListenAndServe()
}

func (proxy *Proxy) ServeHTTP(res http.ResponseWriter, req *http.Request) {
	if req.Method == "CONNECT" {
		proxy.handleConnect(res, req)
		return
	}

	if !req.URL.IsAbs() || req.URL.Host == "" {
		res.WriteHeader(400)
		_, err := io.WriteString(res, "此为代理服务器，不能直接发起请求")
		if err != nil {
			log.Printf("error: %v, url: %v\n", err, req.URL.String())
		}
		return
	}

	start := time.Now()

	proxyReq, err := http.NewRequest(req.Method, req.URL.String(), req.Body)
	if err != nil {
		log.Printf("error: %v, url: %v\n", err, req.URL.String())
		res.WriteHeader(502)
		return
	}

	// TODO: handle Proxy- header
	for key, value := range req.Header {
		proxyReq.Header[key] = value
	}
	proxyRes, err := http.DefaultClient.Do(proxyReq)
	if err != nil {
		log.Printf("error: %v, url: %v\n", err, req.URL.String())
		res.WriteHeader(502)
		return
	}
	defer proxyRes.Body.Close()

	for key, value := range proxyRes.Header {
		res.Header()[key] = value
	}
	res.WriteHeader(proxyRes.StatusCode)
	_, err = io.Copy(res, proxyRes.Body)
	if err != nil {
		log.Printf("error: %v, url: %v\n", err, req.URL.String())
		return
	}

	log.Printf("%v %v %v - %v ms", req.Method, req.URL.String(), proxyRes.StatusCode, time.Since(start).Milliseconds())
}

func (proxy *Proxy) handleConnect(res http.ResponseWriter, req *http.Request) {
	log.Printf("CONNECT: %v\n", req.Host)

	conn, err := net.Dial("tcp", req.Host)
	if err != nil {
		log.Printf("error: %v, host: %v\n", err, req.Host)
		res.WriteHeader(502)
		return
	}
	defer conn.Close()

	cconn, _, err := res.(http.Hijacker).Hijack()
	if err != nil {
		log.Printf("error: %v, host: %v\n", err, req.Host)
		res.WriteHeader(502)
		return
	}
	defer cconn.Close()

	_, err = io.WriteString(cconn, "HTTP/1.1 200 Connection Established\r\n\r\n")
	if err != nil {
		log.Printf("error: %v, host: %v\n", err, req.Host)
		return
	}

	ch := make(chan bool)
	go func() {
		_, err := io.Copy(conn, cconn)
		if err != nil {
			log.Printf("error: %v, host: %v\n", err, req.Host)
		}
		ch <- true
	}()

	_, err = io.Copy(cconn, conn)
	if err != nil {
		log.Printf("error: %v, host: %v\n", err, req.Host)
	}

	<-ch
}

func NewProxy(opts *Options) *Proxy {
	proxy := new(Proxy)
	proxy.Server = &http.Server{
		Addr:    opts.Addr,
		Handler: proxy,
	}
	return proxy
}