package openp2p

import (
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"net"
	"strconv"
	"strings"
	"sync"
	"time"

	reuse "github.com/openp2p-cn/go-reuseport"
)

func natTCP(serverHost string, serverPort int, localPort int) (publicIP string, publicPort int) {
	// dialer := &net.Dialer{
	// 	LocalAddr: &net.TCPAddr{
	// 		IP:   net.ParseIP("0.0.0.0"),
	// 		Port: localPort,
	// 	},
	// }
	conn, err := reuse.DialTimeout("tcp4", fmt.Sprintf("%s:%d", "0.0.0.0", localPort), fmt.Sprintf("%s:%d", serverHost, serverPort), time.Second*5)
	// conn, err := net.Dial("tcp4", fmt.Sprintf("%s:%d", serverHost, serverPort))
	if err != nil {
		fmt.Printf("Dial tcp4 %s:%d error:%s", serverHost, serverPort, err)
		return
	}
	defer conn.Close()
	_, wrerr := conn.Write([]byte("1"))
	if wrerr != nil {
		fmt.Printf("Write error: %s\n", wrerr)
		return
	}
	b := make([]byte, 1000)
	conn.SetReadDeadline(time.Now().Add(time.Second * 5))
	n, rderr := conn.Read(b)
	if rderr != nil {
		fmt.Printf("Read error: %s\n", rderr)
		return
	}
	arr := strings.Split(string(b[:n]), ":")
	if len(arr) < 2 {
		return
	}
	publicIP = arr[0]
	port, _ := strconv.ParseInt(arr[1], 10, 32)
	publicPort = int(port)
	return

}
func natTest(serverHost string, serverPort int, localPort int) (publicIP string, publicPort int, err error) {
	conn, err := net.ListenPacket("udp", fmt.Sprintf(":%d", localPort))
	if err != nil {
		gLog.Println(LvERROR, "natTest listen udp error:", err)
		return "", 0, err
	}
	defer conn.Close()

	dst, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", serverHost, serverPort))
	if err != nil {
		return "", 0, err
	}

	// The connection can write data to the desired address.
	msg, err := newMessage(MsgNATDetect, 0, nil)
	_, err = conn.WriteTo(msg, dst)
	if err != nil {
		return "", 0, err
	}
	deadline := time.Now().Add(NatTestTimeout)
	err = conn.SetReadDeadline(deadline)
	if err != nil {
		return "", 0, err
	}
	buffer := make([]byte, 1024)
	nRead, _, err := conn.ReadFrom(buffer)
	if err != nil {
		gLog.Println(LvERROR, "NAT detect error:", err)
		return "", 0, err
	}
	natRsp := NatDetectRsp{}
	err = json.Unmarshal(buffer[openP2PHeaderSize:nRead], &natRsp)

	return natRsp.IP, natRsp.Port, nil
}

func getNATType(host string, udp1 int, udp2 int) (publicIP string, NATType int, hasIPvr int, hasUPNPorNATPMP int, err error) {
	// the random local port may be used by other.
	localPort := int(rand.Uint32()%15000 + 50000)
	echoPort := P2PNetworkInstance(nil).config.TCPPort
	ip1, port1, err := natTest(host, udp1, localPort)
	if err != nil {
		return "", 0, 0, 0, err
	}
	hasIPv4, hasUPNPorNATPMP := publicIPTest(ip1, echoPort)
	gLog.Printf(LvINFO, "local port:%d, nat port:%d, hasIPv4:%d, UPNP:%d", localPort, port1, hasIPv4, hasUPNPorNATPMP)
	_, port2, err := natTest(host, udp2, localPort) // 2rd nat test not need testing publicip
	gLog.Printf(LvDEBUG, "local port:%d  nat port:%d", localPort, port2)
	if err != nil {
		return "", 0, hasIPv4, hasUPNPorNATPMP, err
	}
	natType := NATSymmetric
	if port1 == port2 {
		natType = NATCone
	}
	return ip1, natType, hasIPv4, hasUPNPorNATPMP, nil
}

func publicIPTest(publicIP string, echoPort int) (hasPublicIP int, hasUPNPorNATPMP int) {
	var echoConn *net.UDPConn
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		var err error
		echoConn, err = net.ListenUDP("udp", &net.UDPAddr{IP: net.IPv4zero, Port: echoPort})
		if err != nil {
			gLog.Println(LvERROR, "echo server listen error:", err)
			return
		}
		buf := make([]byte, 1600)
		// close outside for breaking the ReadFromUDP
		// wait 5s for echo testing
		wg.Done()
		echoConn.SetReadDeadline(time.Now().Add(time.Second * 30))
		n, addr, err := echoConn.ReadFromUDP(buf)
		if err != nil {
			return
		}
		echoConn.WriteToUDP(buf[0:n], addr)
	}()
	wg.Wait() // wait echo udp
	defer echoConn.Close()
	// testing for public ip
	for i := 0; i < 2; i++ {
		if i == 1 {
			// test upnp or nat-pmp
			nat, err := Discover()
			if err != nil || nat == nil {
				gLog.Println(LvDEBUG, "could not perform UPNP discover:", err)
				break
			}
			ext, err := nat.GetExternalAddress()
			if err != nil {
				gLog.Println(LvDEBUG, "could not perform UPNP external address:", err)
				break
			}
			log.Println("PublicIP:", ext)

			externalPort, err := nat.AddPortMapping("udp", echoPort, echoPort, "openp2p", 30)
			if err != nil {
				gLog.Println(LvDEBUG, "could not add udp UPNP port mapping", externalPort)
				break
			} else {
				nat.AddPortMapping("tcp", echoPort, echoPort, "openp2p", 604800)
			}
		}
		gLog.Printf(LvDEBUG, "public ip test start %s:%d", publicIP, echoPort)
		conn, err := net.ListenUDP("udp", nil)
		if err != nil {
			break
		}
		defer conn.Close()
		dst, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", publicIP, echoPort))
		if err != nil {
			break
		}
		conn.WriteTo([]byte("echo"), dst)
		buf := make([]byte, 1600)

		// wait for echo testing
		conn.SetReadDeadline(time.Now().Add(PublicIPEchoTimeout))
		_, _, err = conn.ReadFromUDP(buf)
		if err == nil {
			if i == 1 {
				gLog.Println(LvDEBUG, "UPNP or NAT-PMP:YES")
				hasUPNPorNATPMP = 1
			} else {
				gLog.Println(LvDEBUG, "public ip:YES")
				hasPublicIP = 1
			}
			break
		}
	}
	return
}