package socks

import (
	"io"
	"net"
	"strconv"

	C "github.com/Dreamacro/clash/constant"
	"github.com/Dreamacro/clash/tunnel"

	"github.com/riobard/go-shadowsocks2/socks"
	log "github.com/sirupsen/logrus"
)

var (
	tun = tunnel.GetInstance()
)

func NewSocksProxy(addr string) (*C.ProxySignal, error) {
	l, err := net.Listen("tcp", addr)
	if err != nil {
		return nil, err
	}

	done := make(chan struct{})
	closed := make(chan struct{})
	signal := &C.ProxySignal{
		Done:   done,
		Closed: closed,
	}

	go func() {
		log.Infof("SOCKS proxy listening at: %s", addr)
		for {
			c, err := l.Accept()
			if err != nil {
				if _, open := <-done; !open {
					break
				}
				continue
			}
			go handleSocks(c)
		}
	}()

	go func() {
		<-done
		close(done)
		l.Close()
		closed <- struct{}{}
	}()

	return signal, nil
}

func handleSocks(conn net.Conn) {
	target, err := socks.Handshake(conn)
	if err != nil {
		conn.Close()
		return
	}
	conn.(*net.TCPConn).SetKeepAlive(true)
	tun.Add(NewSocks(target, conn))
}

type SocksAdapter struct {
	conn net.Conn
	addr *C.Addr
}

func (s *SocksAdapter) Close() {
	s.conn.Close()
}

func (s *SocksAdapter) Addr() *C.Addr {
	return s.addr
}

func (s *SocksAdapter) Connect(proxy C.ProxyAdapter) {
	go io.Copy(s.conn, proxy.ReadWriter())
	io.Copy(proxy.ReadWriter(), s.conn)
}

func parseSocksAddr(target socks.Addr) *C.Addr {
	var host, port string
	var ip net.IP

	switch target[0] {
	case socks.AtypDomainName:
		host = string(target[2 : 2+target[1]])
		port = strconv.Itoa((int(target[2+target[1]]) << 8) | int(target[2+target[1]+1]))
		ipAddr, err := net.ResolveIPAddr("ip", host)
		if err == nil {
			ip = ipAddr.IP
		}
	case socks.AtypIPv4:
		ip = net.IP(target[1 : 1+net.IPv4len])
		port = strconv.Itoa((int(target[1+net.IPv4len]) << 8) | int(target[1+net.IPv4len+1]))
	case socks.AtypIPv6:
		ip = net.IP(target[1 : 1+net.IPv6len])
		port = strconv.Itoa((int(target[1+net.IPv6len]) << 8) | int(target[1+net.IPv6len+1]))
	}

	return &C.Addr{
		NetWork:  C.TCP,
		AddrType: int(target[0]),
		Host:     host,
		IP:       &ip,
		Port:     port,
	}
}

func NewSocks(target socks.Addr, conn net.Conn) *SocksAdapter {
	return &SocksAdapter{
		conn: conn,
		addr: parseSocksAddr(target),
	}
}