package service

import (
	"encoding/base64"
	"encoding/binary"
	"fmt"
	"os"
	"runtime"
	"strings"
	"time"

	"golang.org/x/net/http/httpguts"
	"golang.org/x/net/http2/hpack"
)

const (
	GTPU_V1_VERSION = 1 << 5
	GTPU_VER_MASK   = 7 << 5
	GTPU_PT_GTP     = 1 << 4
	GTPU_HEADER_LEN = 12
	GTPU_E_S_PB_BIT = 7
	GTPU_E_BI       = 1 << 2
)

const (
	GTPU_HEADER_VERSION_INDEX  = 0
	GTPU_HEADER_MSG_TYPE_INDEX = 1
	GTPU_HEADER_LENGTH_INDEX   = 2
	GTPU_HEADER_TEID_INDEX     = 4
)

type ExtHeader struct {
	TaskId    uint32
	IMSI      string
	IfType    int
	MsgType   int
	MsgDirect int // 0-recv,1-send
	TimeStamp int64
	SrcIP     string
	DstIP     string
	SrcPort   uint16
	DstPort   uint16
	Proto     int // Protocol
	PPI       int // only for SCTP
	DataLen   uint16
	DataInfo  []byte
}

// parseUDPData 解析UDP数据
func parseUDPData(rvMsg []byte, rvLen int) (ExtHeader, error) {
	var extHdr ExtHeader
	// var tr dborm.TraceData
	var off int
	msg := rvMsg

	verFlags := msg[GTPU_HEADER_VERSION_INDEX]

	gtpuHdrLen := GTPU_HEADER_LEN

	localTeid := binary.BigEndian.Uint32(msg[GTPU_HEADER_TEID_INDEX:])

	extHdr.TaskId = localTeid

	if (verFlags & GTPU_E_S_PB_BIT) != 0 {
		if (verFlags & GTPU_E_BI) != 0 {
			extTypeIndex := GTPU_HEADER_LEN - 1

			extType := msg[extTypeIndex]

			if extType == 0xFE {
				extHdr.IMSI = string(msg[extTypeIndex+2 : extTypeIndex+17])
				extHdr.IfType = int(msg[extTypeIndex+17])
				extHdr.MsgType = int(msg[extTypeIndex+18])
				extHdr.MsgDirect = int(msg[extTypeIndex+19])

				extHdr.TimeStamp = time.Now().UTC().UnixMilli()
				// extHdr.TimeStamp = int64(binary.BigEndian.Uint64(msg[extTypeIndex+19:]))
				// fmt.Printf("ext info %v %s %d %d %d \n", msg[(extTypeIndex+2):(extTypeIndex+20)], extHdr.IMSI, extHdr.IfType, extHdr.MsgType, extHdr.MsgDirect)
				// set offset of IP Packet
				off = 40 + 4
				//src ip: msg+40+12
				extHdr.SrcIP = fmt.Sprintf("%d.%d.%d.%d", msg[off+12], msg[off+13], msg[off+14], msg[off+15])
				//dst ip: msg+40+12+4
				extHdr.DstIP = fmt.Sprintf("%d.%d.%d.%d", msg[off+16], msg[off+17], msg[off+18], msg[off+19])
				extHdr.SrcPort = uint16(binary.BigEndian.Uint16(msg[off+20:]))
				extHdr.DstPort = uint16(binary.BigEndian.Uint16(msg[off+22:]))
				// fmt.Printf("info %s:%d %s:%d \n", extHdr.SrcIP, extHdr.SrcPort, extHdr.DstIP, extHdr.DstPort)
				// ip header start msg+40
				extHdr.DataLen = uint16(rvLen - off)
				extHdr.DataInfo = make([]byte, int(rvLen-off))
				copy(extHdr.DataInfo, []byte(msg[off:]))

				// 132 SCTP
				// 6 TCP
				// 17 UDP
				extHdr.Proto = int(msg[off+9])
				if extHdr.Proto == 132 {
					extHdr.PPI = int(msg[off+47])
					extHdr.DataLen = uint16(binary.BigEndian.Uint16(msg[(off+34):]) - 16)
					// fmt.Printf("dat len %d %d \n", extHdr.DataLen, extHdr.PPI)
				}
			}

			for extType != 0 && extTypeIndex < rvLen {
				extLen := msg[extTypeIndex+1] << 2
				if extLen == 0 {
					return extHdr, fmt.Errorf("error, extLen is zero")
				}

				gtpuHdrLen += int(extLen)
				extTypeIndex += int(extLen)
				extType = msg[extTypeIndex]
			}
		}
	} else {
		gtpuHdrLen -= 4
	}
	return extHdr, nil
}

// UDPDataHandler UDP数据处理
func UDPDataHandler(data []byte, n int) (map[string]any, error) {
	extHdr, err := parseUDPData(data, n)
	if err != nil {
		return nil, err
	}
	if extHdr.TaskId == 0 || extHdr.DataLen < 1 {
		return nil, fmt.Errorf("data error")
	}

	m := map[string]any{
		"taskId":    extHdr.TaskId,
		"imsi":      extHdr.IMSI,
		"ifType":    extHdr.IfType,
		"srcAddr":   fmt.Sprintf("%s:%d", extHdr.SrcIP, extHdr.SrcPort),
		"dstAddr":   fmt.Sprintf("%s:%d", extHdr.DstIP, extHdr.DstPort),
		"msgType":   extHdr.MsgType,
		"msgDirect": extHdr.MsgDirect,
		"timestamp": extHdr.TimeStamp,
		"dataLen":   extHdr.DataLen,
		// "dataInfo":  extHdr.DataInfo,
		"decMsg": "",
	}
	// Base64 编码
	m["dataInfo"] = base64.StdEncoding.EncodeToString(extHdr.DataInfo)

	if extHdr.Proto == 6 { // TCP
		// 取响应数据
		iplen := uint16(binary.BigEndian.Uint16(extHdr.DataInfo[2:]))
		tcplen := uint16(iplen - 32 - 20)
		hdrlen := uint16(binary.BigEndian.Uint16(extHdr.DataInfo[20+32+1:]))
		offset := uint16(52)
		// fmt.Printf("HTTP %d %d %d \n", iplen, tcplen, hdrlen)
		if tcplen > (hdrlen + 9) { // has data
			doffset := uint16(offset + hdrlen + 9)
			datlen := uint16(binary.BigEndian.Uint16(extHdr.DataInfo[doffset+1:]))
			// fmt.Printf("HTTP datlen %d \n", datlen)
			m["decMsg"], _ = httpDataMsg(extHdr.DataInfo[offset+9:offset+9+hdrlen], extHdr.DataInfo[doffset+9:doffset+datlen+9])
		} else {
			m["decMsg"], _ = httpDataMsg(extHdr.DataInfo[offset+9:hdrlen], nil)
		}
	}

	// pcap文件
	m["pcapFile"] = writePcap(extHdr)
	return m, nil
}

// =========== TCP协议Body ===========

// httpDataMsg Http数据信息处理
func httpDataMsg(header []byte, data []byte) (string, error) {
	var remainSize = uint32(16 << 20)
	var sawRegular bool
	var invalid bool // pseudo header field errors
	var Fields []hpack.HeaderField

	invalid = false
	hdec := hpack.NewDecoder(4096, nil)
	hdec.SetEmitEnabled(true)
	hdec.SetMaxStringLength(int(16 << 20))
	hdec.SetEmitFunc(func(hf hpack.HeaderField) {
		if !httpguts.ValidHeaderFieldValue(hf.Value) {
			// Don't include the value in the error, because it may be sensitive.
			invalid = true
		}
		isPseudo := strings.HasPrefix(hf.Name, ":")
		if isPseudo {
			if sawRegular {
				invalid = true
			}
		} else {
			sawRegular = true
			if !validWireHeaderFieldName(hf.Name) {
				invalid = true
			}
		}

		if invalid {
			hdec.SetEmitEnabled(false)
			return
		}

		size := hf.Size()
		if size > remainSize {
			hdec.SetEmitEnabled(false)
			//mh.Truncated = true
			return
		}
		remainSize -= size

		Fields = append(Fields, hf)
	})

	// defer hdec.SetEmitFunc(func(hf hpack.HeaderField) {})

	frag := header
	if _, err := hdec.Write(frag); err != nil {
		return "", err
	}

	if err := hdec.Close(); err != nil {
		return "", err
	}

	// hdec.SetEmitFunc(func(hf hpack.HeaderField) {})

	var headers []byte
	var line string
	for i := range Fields {
		line = fmt.Sprintf("\"%s\":\"%s\",", Fields[i].Name, Fields[i].Value)
		headers = append(headers, []byte(line)...)
	}

	if len(data) > 0 {
		return fmt.Sprintf("{ %s \"content\":%s }", string(headers), string(data)), nil
	} else {
		return fmt.Sprintf("{ %s }", string(headers)), nil
	}
}

// validWireHeaderFieldName 校验报文头字段名称
func validWireHeaderFieldName(v string) bool {
	if len(v) == 0 {
		return false
	}
	for _, r := range v {
		if !httpguts.IsTokenRune(r) {
			return false
		}
		if 'A' <= r && r <= 'Z' {
			return false
		}
	}
	return true
}

// =========== writePcap 写Pcap文件 ===========

const magicMicroseconds = 0xA1B2C3D4
const versionMajor = 2
const versionMinor = 4

func writeEmptyPcap(filename string, timeStamp int64, length int, data []byte) error {
	var err error
	var file *os.File
	if _, err = os.Stat(filename); os.IsNotExist(err) {
		file, err = os.Create(filename)
		// File Header
		var fileHeaderBuf [24]byte
		binary.LittleEndian.PutUint32(fileHeaderBuf[0:4], magicMicroseconds)
		binary.LittleEndian.PutUint16(fileHeaderBuf[4:6], versionMajor)
		binary.LittleEndian.PutUint16(fileHeaderBuf[6:8], versionMinor)
		// bytes 8:12 stay 0 (timezone = UTC)
		// bytes 12:16 stay 0 (sigfigs is always set to zero, according to
		//   http://wiki.wireshark.org/Development/LibpcapFileFormat
		binary.LittleEndian.PutUint32(fileHeaderBuf[16:20], 0x00040000)
		binary.LittleEndian.PutUint32(fileHeaderBuf[20:24], 0x00000071)
		if _, err := file.Write(fileHeaderBuf[:]); err != nil {
			return err
		}
	} else {
		file, err = os.OpenFile(filename, os.O_WRONLY|os.O_APPEND, 0666)
	}
	if err != nil {
		return err
	}
	defer file.Close()

	// Packet Header
	var packetHeaderBuf [24]byte
	t := time.UnixMilli(timeStamp)
	if t.IsZero() {
		t = time.Now()
	}
	secs := t.Unix()
	usecs := t.Nanosecond() / 1000
	binary.LittleEndian.PutUint32(packetHeaderBuf[0:4], uint32(secs))
	binary.LittleEndian.PutUint32(packetHeaderBuf[4:8], uint32(usecs))
	binary.LittleEndian.PutUint32(packetHeaderBuf[8:12], uint32(length+16))
	binary.LittleEndian.PutUint32(packetHeaderBuf[12:16], uint32(length+16))
	if _, err := file.Write(packetHeaderBuf[:]); err != nil {
		return err
	}

	// 数据包内容的定义
	cooked := [...]byte{0x00, 0x00, 0x03, 0x04, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00}
	if _, err := file.Write(cooked[:]); err != nil {
		return err
	}

	// Packet Data
	if _, err := file.Write(data); err != nil {
		return err
	}
	return nil
}

// writePcap 写Pcap文件并返回文件路径
func writePcap(extHdr ExtHeader) string {
	filePath := fmt.Sprintf("/tmp/trace_%d .pcap", extHdr.TaskId)
	if runtime.GOOS == "windows" {
		filePath = fmt.Sprintf("C:%s", filePath)
	}
	err := writeEmptyPcap(filePath, extHdr.TimeStamp, int(extHdr.DataLen), extHdr.DataInfo)
	if err != nil {
		return ""
	}
	return filePath
}