package httptunnel

import (
	"bufio"
	"errors"
	"log"
	"net"
	"net/http"
	"strings"
)

type Server struct {
	addr    string
	forward func(src net.Conn, dst string) (err error)
}

func New(addr string, forward func(src net.Conn, dst string) (err error)) *Server {
	return &Server{
		addr,
		forward,
	}
}

func (s *Server) ListenAndServe() (err error) {
	l, err := net.Listen("tcp", s.addr)
	if err != nil {
		return err
	}
	defer l.Close()

	for {
		conn, err := l.Accept()
		if err != nil {
			return err
		}
		go s.Serve(conn)
	}
}

func (s *Server) Parse(conn net.Conn) (target string, err error) {
	reader := bufio.NewReader(conn)
	line, _, err := reader.ReadLine()
	if err != nil {
		return "", err
	}

	terms := strings.Split(string(line), " ")
	if len(terms) != 3 {
		return "", errors.New("bad protocol")
	}
	if terms[0] != http.MethodConnect {
		return "", errors.New("method is not connect")
	}
	_, err = conn.Write([]byte("HTTP/1.1 200 OK\r\n\r\n"))
	return terms[1], err
}

func (s *Server) Serve(conn net.Conn) {
	defer conn.Close()

	target, err := s.Parse(conn)
	if err != nil {
		log.Printf("failed to parse http tunnel protocol error: %v", err)
		return
	}

	if err := s.forward(conn, target); err != nil {
		log.Printf("http tunnel server forward request error: %v", err)
	}
}