package main

import (
	"bytes"
	"crypto/rand"
	"encoding/binary"
	"fmt"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/nonoo/kappanhang/log"
)

var conn *net.UDPConn
var localSID uint32
var remoteSID uint32
var sendSeq uint16
var authSendSeq uint16
var authID [6]byte
var randIDByteForPktSeven [1]byte
var expectedPkt7ReplySeq uint16

func send(d []byte) {
	_, err := conn.Write(d)
	if err != nil {
		log.Fatal(err)
	}
}

func read() ([]byte, error) {
	err := conn.SetReadDeadline(time.Now().Add(time.Second))
	if err != nil {
		log.Fatal(err)
	}

	b := make([]byte, 1500)
	n, _, err := conn.ReadFromUDP(b)
	if err != nil {
		if err, ok := err.(net.Error); ok && !err.Timeout() {
			log.Fatal(err)
		}
	}
	return b[:n], err
}

func setupCloseHandler() {
	c := make(chan os.Signal)
	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
	go func() {
		<-c
		log.Print("disconnecting")
		sendDisconnect()
		os.Exit(0)
	}()
}

func sendPkt7(replyID []byte, seq uint16) {
	// Example request from PC:  0x15, 0x00, 0x00, 0x00, 0x07, 0x00, 0x09, 0x00, 0xbe, 0xd9, 0xf2, 0x63, 0xe4, 0x35, 0xdd, 0x72, 0x00, 0x78, 0x40, 0xf6, 0x02
	// Example reply from radio: 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x09, 0x00, 0xe4, 0x35, 0xdd, 0x72, 0xbe, 0xd9, 0xf2, 0x63, 0x01, 0x78, 0x40, 0xf6, 0x02
	var replyFlag byte
	if replyID == nil {
		replyID = make([]byte, 4)
		var randID [2]byte
		_, err := rand.Read(randID[:])
		if err != nil {
			log.Fatal(err)
		}
		replyID[0] = randID[0]
		replyID[1] = randID[1]
		replyID[2] = randIDByteForPktSeven[0]
		replyID[3] = 0x03
	} else {
		replyFlag = 0x01
	}

	expectedPkt7ReplySeq = sendSeq

	send([]byte{0x15, 0x00, 0x00, 0x00, 0x07, 0x00, byte(seq), byte(seq >> 8),
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID),
		replyFlag, replyID[0], replyID[1], replyID[2], replyID[3]})
}

func sendPkt3() {
	send([]byte{0x10, 0x00, 0x00, 0x00, 0x03, 0x00, byte(sendSeq), byte(sendSeq >> 8),
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID)})
}

func sendPkt6() {
	send([]byte{0x10, 0x00, 0x00, 0x00, 0x06, 0x00, 0x01, 0x00,
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID)})
}

func sendPktLogin() {
	var randID [2]byte
	_, err := rand.Read(randID[:])
	if err != nil {
		log.Fatal(err)
	}
	send([]byte{0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00,
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID),
		0x00, 0x00, 0x00, 0x70, 0x01, 0x00, 0x00, byte(authSendSeq),
		byte(authSendSeq >> 8), 0x00, randID[0], randID[1], 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x2b, 0x3f, 0x55, 0x5c, 0x00, 0x00, 0x00, 0x00, // username: beer
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x2b, 0x3f, 0x55, 0x5c, 0x3f, 0x25, 0x77, 0x58, // pass: beerbeer
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x69, 0x63, 0x6f, 0x6d, 0x2d, 0x70, 0x63, 0x00, // icom-pc
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
}

func sendPktReauth() {
	// Example request from PC:  0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0d, 0x00,
	//                           0xbb, 0x41, 0x3f, 0x2b, 0xe6, 0xb2, 0x7b, 0x7b,
	//                           0x00, 0x00, 0x00, 0x30, 0x01, 0x05, 0x00, 0x02,
	//                           0x00, 0x00, 0x5d, 0x37, 0x12, 0x82, 0x3b, 0xde,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
	// Example reply from radio: 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x00,
	//                           0xe6, 0xb2, 0x7b, 0x7b, 0xbb, 0x41, 0x3f, 0x2b,
	//                           0x00, 0x00, 0x00, 0x30, 0x02, 0x05, 0x00, 0x02,
	//                           0x00, 0x00, 0x5d, 0x37, 0x12, 0x82, 0x3b, 0xde,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	//                           0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
	send([]byte{0x40, 0x00, 0x00, 0x00, 0x00, 0x00, byte(sendSeq), byte(sendSeq >> 8),
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID),
		0x00, 0x00, 0x00, 0x30, 0x01, 0x05, 0x00, byte(authSendSeq),
		byte(authSendSeq >> 8), 0x00, authID[0], authID[1], authID[2], authID[3], authID[4], authID[5],
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
}

func sendDisconnect() {
	send([]byte{0x40, 0x00, 0x00, 0x00, 0x00, 0x00, byte(sendSeq), byte(sendSeq >> 8),
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID),
		0x00, 0x00, 0x00, 0x30, 0x01, 0x01, 0x00, byte(authSendSeq),
		byte(authSendSeq >> 8), 0x00, authID[0], authID[1], authID[2], authID[3], authID[4], authID[5],
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
	send([]byte{0x10, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00,
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID),
		byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID)})
}

func sendRequestSerialAndAudio() {
	send([]byte{0x90, 0x00, 0x00, 0x00, 0x00, 0x00, byte(sendSeq), byte(sendSeq >> 8),
		byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID),
		0x00, 0x00, 0x00, 0x80, 0x01, 0x03, 0x00, byte(authSendSeq),
		byte(authSendSeq >> 8), 0x00, authID[0], authID[1], authID[2], authID[3], authID[4], authID[5],
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10,
		0x80, 0x00, 0x00, 0x90, 0xc7, 0x0e, 0x86, 0x01, // The last 5 bytes from this row can be acquired from a reply starting with 0xa8 pr 0x90
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x49, 0x43, 0x2d, 0x37, 0x30, 0x35, 0x00, 0x00, // IC-705
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x2b, 0x3f, 0x55, 0x5c, 0x00, 0x00, 0x00, 0x00, // username: beer
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x01, 0x01, 0x04, 0x04, 0x00, 0x00, 0xbb, 0x80,
		0x00, 0x00, 0xbb, 0x80, 0x00, 0x00, 0xc3, 0x52,
		0x00, 0x00, 0xc3, 0x53, 0x00, 0x00, 0x00, 0x64,
		0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
}

func main() {
	log.Init()
	parseArgs()
	setupCloseHandler()

	hostPort := fmt.Sprint(connectAddress, ":", connectPort)
	log.Print("connecting to ", hostPort)
	raddr, err := net.ResolveUDPAddr("udp", hostPort)
	if err != nil {
		log.Fatal(err)
	}
	conn, err = net.DialUDP("udp", nil, raddr)
	if err != nil {
		log.Fatal(err)
	}

	// Constructing the local session ID by combining the local IP address and port.
	laddr := conn.LocalAddr().(*net.UDPAddr)
	localSID = binary.BigEndian.Uint32(laddr.IP[len(laddr.IP)-4:])<<16 | uint32(laddr.Port&0xffff)
	log.Debugf("using session id %.8x", localSID)

	sendPkt3()
	sendSeq = 1
	sendPkt7(nil, sendSeq)
	sendSeq = 0
	sendPkt3()

	for {
		// Expecting a Pkt4 answer.
		// Example answer from radio: 0x10, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x8c, 0x7d, 0x45, 0x7a, 0x1d, 0xf6, 0xe9, 0x0b
		r, _ := read()
		if bytes.Equal(r[:8], []byte{0x10, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00}) {
			remoteSID = binary.BigEndian.Uint32(r[8:12])
			break
		}
	}

	log.Debugf("got remote session id %.8x", remoteSID)

	sendSeq = 1
	authSendSeq = 1
	sendPkt6()
	sendPktLogin()
	authSendSeq++

	var lastPingAt time.Time
	var lastReauthAt time.Time
	var lastStatusLog time.Time
	var errCount int

	_, err = rand.Read(randIDByteForPktSeven[:])
	if err != nil {
		log.Fatal(err)
	}

	for {
		r, err := read()
		if err != nil {
			errCount++
			if errCount > 5 {
				log.Fatal("timeout")
			}
			log.Error("stream break detected")
		}
		errCount = 0

		// Example success auth packet: 0x60, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00,
		//                              0xe6, 0xb2, 0x7b, 0x7b, 0xbb, 0x41, 0x3f, 0x2b,
		//                              0x00, 0x00, 0x00, 0x50, 0x02, 0x00, 0x00, 0x00,
		//                              0x00, 0x00, 0x5d, 0x37, 0x12, 0x82, 0x3b, 0xde,
		//                              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		//                              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		//                              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		//                              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		//                              0x46, 0x54, 0x54, 0x48, 0x00, 0x00, 0x00, 0x00,
		//                              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		//                              0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		//                              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
		if len(r) == 96 && bytes.Equal(r[:8], []byte{0x60, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00}) {
			if bytes.Equal(r[48:52], []byte{0xff, 0xff, 0xff, 0xfe}) {
				log.Fatal("invalid user/password")
			} else {
				copy(authID[:], r[26:32])
				log.Print("auth ok")
			}
		}
		if len(r) == 21 && bytes.Equal(r[1:6], []byte{0x00, 0x00, 0x00, 0x07, 0x00}) {
			gotSeq := binary.LittleEndian.Uint16(r[6:8])
			if r[16] == 0x00 { // This is a pkt7 request from the radio.
				// Replying to the radio.
				// Example request from radio: 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x1c, 0x0e, 0xe4, 0x35, 0xdd, 0x72, 0xbe, 0xd9, 0xf2, 0x63, 0x00, 0x57, 0x2b, 0x12, 0x00
				// Example answer from PC:     0x15, 0x00, 0x00, 0x00, 0x07, 0x00, 0x1c, 0x0e, 0xbe, 0xd9, 0xf2, 0x63, 0xe4, 0x35, 0xdd, 0x72, 0x01, 0x57, 0x2b, 0x12, 0x00
				sendPkt7(r[17:21], gotSeq)
			} else {
				if expectedPkt7ReplySeq != gotSeq {
					var missingPkts int
					if gotSeq > expectedPkt7ReplySeq {
						missingPkts = int(gotSeq) - int(expectedPkt7ReplySeq)
					} else {
						missingPkts = int(gotSeq) + 65536 - int(expectedPkt7ReplySeq)
					}
					if missingPkts < 1000 {
						log.Error("lost ", missingPkts, " packets ", gotSeq, " ", expectedPkt7ReplySeq)
					}
				}
			}
		}
		if len(r) == 16 && bytes.Equal(r[:6], []byte{0x10, 0x00, 0x00, 0x00, 0x00, 0x00}) {
			// Replying to the radio.
			// Example request from radio: 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0x00, 0xe4, 0x35, 0xdd, 0x72, 0xbe, 0xd9, 0xf2, 0x63
			// Example answer from PC:     0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0x00, 0xbe, 0xd9, 0xf2, 0x63, 0xe4, 0x35, 0xdd, 0x72
			gotSeq := binary.LittleEndian.Uint16(r[6:8])
			send([]byte{0x10, 0x00, 0x00, 0x00, 0x00, 0x00, byte(gotSeq), byte(gotSeq >> 8), byte(localSID >> 24), byte(localSID >> 16), byte(localSID >> 8), byte(localSID), byte(remoteSID >> 24), byte(remoteSID >> 16), byte(remoteSID >> 8), byte(remoteSID)})
		}

		if time.Since(lastPingAt) >= 100*time.Millisecond {
			sendPkt7(nil, sendSeq)
			sendPkt3()
			sendSeq++
			lastPingAt = time.Now()

			if time.Since(lastReauthAt) >= 60*time.Second {
				sendPktReauth()
				authSendSeq++
				lastReauthAt = time.Now()
			}

			if time.Since(lastStatusLog) >= 10*time.Second {
				log.Print("still connected")
				lastStatusLog = time.Now()
			}
		}
	}
}