package rdp

import (
	"bytes"
	"context"
	"encoding/binary"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"os"
	"time"
	"unicode/utf16"

	"ezops/pkg/rdp/credssp"
	"ezops/pkg/rdp/transport"
)

const (
	mcsConnectInitial  = 0x65
	mcsConnectResponse = 0x66

	mcsErectDomainRequest  = 1
	mcsAttachUserRequest   = 10
	mcsAttachUserConfirm   = 11
	mcsChannelJoinRequest  = 14
	mcsChannelJoinConfirm  = 15
	mcsSendDataRequest     = 25
	mcsSendDataIndication  = 26
	mcsGlobalChannelID     = 1003
	mcsUserChannelIDOffset = 1001

	gccCSCore     = 0xC001
	gccCSSecurity = 0xC002
	gccCSNet      = 0xC003
	gccSCCore     = 0x0C01
	gccSCSecurity = 0x0C02
	gccSCNet      = 0x0C03

	// 静态虚拟通道声明(MS-RDPBCGR 2.2.7.1.1 Channel Pool)
	// channel name 固定 8 字节 ASCII，不足补 0；options 控制通道加密/压缩行为 // Logan.Li
	channelNameRdpdr          = "rdpdr"
	channelNameRdpsnd         = "rdpsnd"
	channelNameCliprdr        = "cliprdr"
	channelNameDrdynvc        = "drdynvc"
	channelOptionInitialized  = 0x80000000
	channelOptionEncryptRDP   = 0x40000000
	channelOptionShowProtocol = 0x00200000
	channelOptionCompressRDP  = 0x00800000

	secFlagInfoPkt    = 0x0040
	secFlagLicensePkt = 0x0080

	licenseErrorAlert        = 0xff
	licenseStatusValid       = 0x00000007
	licenseStateNoTransit    = 0x00000002
	pduTypeDemandActive      = 0x0011
	pduTypeConfirmActive     = 0x0013
	pduTypeDeactivateAll     = 0x0016
	pduTypeData              = 0x0017
	pduTypeServerRedirect    = 0x001a
	pduType2Synchronize      = 0x1f
	pduType2Control          = 0x14
	pduType2FontList         = 0x27
	pduType2FontMap          = 0x28
	pduType2RefreshRect      = 0x21
	pduType2SetErrorInfo     = 0x2f
	pduType2SuppressOutput   = 0x23
	pduType2SaveSessionInfo  = 0x26
	pduType2FrameAcknowledge = 0x38
	ctrlActionGrantedControl = 0x0002
)

var errFinalizeActive = errors.New("RDP 会话已进入图形更新流")

// MCSProbeInfo 记录 NLA 后 MCS/GCC 连接期响应，用于确认图形会话层入口是否跑通 // Logan.Li
type MCSProbeInfo struct {
	HandshakeInfo
	UserDataBytes      int
	ServerCoreVersion  uint32
	ServerChannelID    uint16
	ServerChannelCount uint16
	ServerChannelIDs   []uint16
	// ChannelNameByID 记录服务端在 Connect-Response 里分配的 channel ID 对应的名称。
	// 客户端在 Connect-Initial 里声明的 channel def 顺序与服务端返回的 ServerChannelIDs 一一对应，
	// 据此建立 ID→名称映射，供 readLoop 按通道分发虚拟通道数据（cliprdr/rdpdr）。// Logan.Li
	ChannelNameByID     map[uint16]string
	ServerEncryption    uint32
	ServerEncryptionLvl uint32
	UserChannelID       uint16
	MessageChannelID    uint16
	JoinedChannels      []uint16
	FirstDataChannelID  uint16
	FirstSecurityFlags  uint16
	FirstPayloadBytes   int
	LicenseMessageType  uint8
	LicenseErrorCode    uint32
	LicenseState        uint32
	DemandPDUType       uint16
	DemandSharedID      uint32
	DemandCapabilities  uint16
	DemandSource        string
	PostConfirmTypes    []uint8
}

// ProbeMCSConnect 复用同一条 CredSSP TLS 连接发送 MCS Connect Initial 并解析 Connect Response // Logan.Li
func ProbeMCSConnect(ctx context.Context, cfg Config) (MCSProbeInfo, error) {
	port := cfg.Port
	if port == 0 {
		port = 3389
	}
	address := fmt.Sprintf("%s:%d", cfg.Host, port)
	start := time.Now()
	rdpDebugf(cfg, "probe start address=%s mode=%q", address, cfg.MCSMode)
	strategies := []credssp.Options{
		{Version: 6, PubKeyStyle: "binding"},
		{Version: 6, PubKeyStyle: "binding", UseCBT: true},
		{Version: 6, PubKeyStyle: "binding", ForceMIC: true},
		{Version: 2, PubKeyStyle: "raw"},
	}
	var lastErr error
	for _, opts := range strategies {
		rdpDebugf(cfg, "strategy start version=%d pubkey=%s cbt=%v mic=%v", opts.Version, opts.PubKeyStyle, opts.UseCBT, opts.ForceMIC)
		info, err := probeMCSConnectOnce(ctx, cfg, address, opts)
		if err == nil {
			info.Duration = time.Since(start)
			rdpDebugf(cfg, "probe ok duration=%s joined=%v post=%v", info.Duration.Round(time.Millisecond), info.JoinedChannels, info.PostConfirmTypes)
			return info, nil
		}
		rdpDebugf(cfg, "strategy failed version=%d pubkey=%s err=%v", opts.Version, opts.PubKeyStyle, err)
		lastErr = err
	}
	if lastErr == nil {
		lastErr = fmt.Errorf("MCS Connect Initial 失败")
	}
	return MCSProbeInfo{HandshakeInfo: HandshakeInfo{Address: address, Duration: time.Since(start)}}, lastErr
}

func probeMCSConnectOnce(ctx context.Context, cfg Config, address string, opts credssp.Options) (MCSProbeInfo, error) {
	start := time.Now()
	tlsConn, result, err := dialCredSSPOnce(ctx, cfg, address, opts)
	if err != nil {
		return MCSProbeInfo{}, err
	}
	defer tlsConn.Close()
	rdpDebugf(cfg, "credssp ok protocol=%s elapsed=%s", result.ProtocolName(), time.Since(start).Round(time.Millisecond))
	_ = tlsConn.SetDeadline(time.Now().Add(30 * time.Second))
	rdpDebugf(cfg, "send MCS ConnectInitial")
	if err := transport.WriteX224Data(tlsConn, buildMCSConnectInitial(cfg)); err != nil {
		return MCSProbeInfo{}, err
	}
	payload, err := transport.ReadX224Data(tlsConn)
	if err != nil {
		return MCSProbeInfo{}, err
	}
	if cfg.Debug {
		debugGCCServerBlocks(cfg, payload)
	}
	mcsInfo, err := parseMCSConnectResponse(payload)
	if err != nil {
		return MCSProbeInfo{}, err
	}
	rdpDebugf(cfg, "connect response userData=%d channel=%d channels=%v enc=%d/%d", mcsInfo.UserDataBytes, mcsInfo.ServerChannelID, mcsInfo.ServerChannelIDs, mcsInfo.ServerEncryption, mcsInfo.ServerEncryptionLvl)
	userID, err := attachMCSUser(tlsConn)
	if err != nil {
		return MCSProbeInfo{}, err
	}
	mcsInfo.UserChannelID = userID
	rdpDebugf(cfg, "attach user ok userID=%d", userID)
	joinIDs := append([]uint16{mcsGlobalChannelID, userID}, mcsInfo.ServerChannelIDs...)
	if mcsInfo.MessageChannelID != 0 {
		joinIDs = append(joinIDs, mcsInfo.MessageChannelID)
	}
	for _, channelID := range joinIDs {
		joined, err := joinMCSChannel(tlsConn, userID, channelID)
		if err != nil {
			return MCSProbeInfo{}, err
		}
		mcsInfo.JoinedChannels = append(mcsInfo.JoinedChannels, joined)
		rdpDebugf(cfg, "join channel ok channel=%d", joined)
	}
	first, demand, err := sendClientInfoAndReadDemand(tlsConn, cfg, userID)
	if err != nil {
		return MCSProbeInfo{}, err
	}
	mcsInfo.FirstDataChannelID = first.channelID
	mcsInfo.FirstSecurityFlags = first.securityFlags
	mcsInfo.FirstPayloadBytes = len(first.payload)
	mcsInfo.LicenseMessageType = first.licenseMsgType
	mcsInfo.LicenseErrorCode = first.licenseErrorCode
	mcsInfo.LicenseState = first.licenseState
	mcsInfo.DemandPDUType = demand.pduType
	mcsInfo.DemandSharedID = demand.sharedID
	mcsInfo.DemandCapabilities = demand.capabilityCount
	mcsInfo.DemandSource = string(demand.sourceDescriptor)
	rdpDebugf(cfg, "demand active shared=0x%08x caps=%d source=%q firstSecurity=0x%04x firstPayload=%d", demand.sharedID, demand.capabilityCount, string(demand.sourceDescriptor), first.securityFlags, len(first.payload))
	postTypes, _, err := sendConfirmActiveAndFinalize(tlsConn, cfg, userID, demand)
	if err != nil {
		return MCSProbeInfo{}, fmt.Errorf("Client Finalize 失败: shared=0x%08x caps=%d source=%q: %w", demand.sharedID, demand.capabilityCount, string(demand.sourceDescriptor), err)
	}
	mcsInfo.PostConfirmTypes = postTypes
	state := tlsConn.ConnectionState()
	certSubject := ""
	if len(state.PeerCertificates) > 0 {
		certSubject = state.PeerCertificates[0].Subject.String()
	}
	mcsInfo.HandshakeInfo = HandshakeInfo{
		Address:          address,
		SelectedProtocol: result.ProtocolName(),
		TLSCipher:        transport.TLSCipherSuiteName(state.CipherSuite),
		CertSubject:      certSubject,
	}
	return mcsInfo, nil
}

func debugGCCServerBlocks(cfg Config, mcsPayload []byte) {
	info, err := parseMCSConnectResponse(mcsPayload)
	if err != nil {
		rdpDebugf(cfg, "debug gcc parse failed err=%v", err)
		return
	}
	rdpDebugf(cfg, "debug gcc summary userData=%d core=0x%08x scNet=%d msg=%d", info.UserDataBytes, info.ServerCoreVersion, info.ServerChannelID, info.MessageChannelID)
}

type mcsDataIndication struct {
	channelID        uint16
	securityFlags    uint16
	payload          []byte
	licenseMsgType   uint8
	licenseErrorCode uint32
	licenseState     uint32
}

type demandActiveProbe struct {
	pduType          uint16
	sharedID         uint32
	capabilityCount  uint16
	sourceDescriptor []byte
}

func sendClientInfoAndReadDemand(rw io.ReadWriter, cfg Config, userID uint16) (mcsDataIndication, demandActiveProbe, error) {
	infoPDU := buildClientInfoPDU(cfg)
	rdpDebugf(cfg, "send ClientInfo userID=%d bytes=%d", userID, len(infoPDU))
	if err := transport.WriteX224Data(rw, buildMCSSendDataRequest(userID, mcsGlobalChannelID, infoPDU)); err != nil {
		return mcsDataIndication{}, demandActiveProbe{}, err
	}
	payload, err := transport.ReadX224Data(rw)
	if err != nil {
		return mcsDataIndication{}, demandActiveProbe{}, err
	}
	first, err := parseMCSDataIndication(payload)
	if err != nil {
		return mcsDataIndication{}, demandActiveProbe{}, err
	}
	if first.securityFlags&secFlagLicensePkt != 0 {
		rdpDebugf(cfg, "license packet security=0x%04x payload=%d", first.securityFlags, len(first.payload))
		if err := parseLicensePacket(&first); err != nil {
			return first, demandActiveProbe{}, err
		}
		payload, err = transport.ReadX224Data(rw)
		if err != nil {
			return first, demandActiveProbe{}, err
		}
	}
	next, err := parseMCSDataIndication(payload)
	if err != nil {
		return first, demandActiveProbe{}, err
	}
	demand, err := parseDemandActiveProbe(next.payload)
	if err != nil {
		return first, demandActiveProbe{}, err
	}
	return first, demand, nil
}

func sendConfirmActiveAndFinalize(rw io.ReadWriter, cfg Config, userID uint16, demand demandActiveProbe) ([]uint8, []mcsDataIndication, error) {
	rdpDebugf(cfg, "finalize start userID=%d shared=0x%08x", userID, demand.sharedID)
	pdus := []struct {
		name string
		data []byte
	}{
		{"ConfirmActive", buildConfirmActivePDU(cfg, userID, demand)},
		{"Synchronize", buildDataPDU(userID, demand.sharedID, pduType2Synchronize, buildSynchronizeData(userID))},
		{"ControlCooperate", buildDataPDU(userID, demand.sharedID, pduType2Control, buildControlData(0x0004))},
		{"ControlRequest", buildDataPDU(userID, demand.sharedID, pduType2Control, buildControlData(0x0001))},
		{"FontList", buildDataPDU(userID, demand.sharedID, pduType2FontList, buildFontListData())},
	}
	var types []uint8
	for _, pdu := range pdus {
		rdpDebugf(cfg, "finalize send %s bytes=%d", pdu.name, len(pdu.data))
		if err := transport.WriteX224Data(rw, buildMCSSendDataRequest(userID, mcsGlobalChannelID, pdu.data)); err != nil {
			return nil, nil, fmt.Errorf("发送 %s 失败: %w", pdu.name, err)
		}
		if isRDPStepMode(cfg) {
			if stepTypes, err := readFinalizeStep(rw, pdu.name, 500*time.Millisecond); err != nil {
				return append(types, stepTypes...), nil, err
			} else if len(stepTypes) > 0 {
				types = append(types, stepTypes...)
			}
		}
	}
	readTypes, pending, err := waitFinalizeResponses(rw, cfg, 5*time.Second)
	if err != nil {
		return types, pending, err
	}
	types = append(types, readTypes...)
	return types, pending, nil
}

func isRDPStepMode(cfg Config) bool {
	return cfg.MCSMode == "step" || cfg.MCSMode == "step-legacy" || cfg.MCSMode == "step-bpp32" || cfg.MCSMode == "step-minimal" || cfg.MCSMode == "step-plain-info" || cfg.MCSMode == "step-grdp-comment" || cfg.MCSMode == "step-grdp-modern"
}

func readFinalizeStep(rw io.ReadWriter, name string, timeout time.Duration) ([]uint8, error) {
	conn, ok := rw.(interface{ SetReadDeadline(time.Time) error })
	if !ok {
		return nil, nil
	}
	_ = conn.SetReadDeadline(time.Now().Add(timeout))
	defer conn.SetReadDeadline(time.Time{})
	payload, err := transport.ReadX224Data(rw)
	if err != nil {
		return nil, nil
	}
	data, err := parseMCSDataIndication(payload)
	if err != nil {
		return nil, fmt.Errorf("%s 后响应解析失败: %w", name, err)
	}
	got, err := parseShareDataPDUInfo(data.payload)
	if err != nil {
		return nil, fmt.Errorf("%s 后 Share Data 解析失败: %w", name, err)
	}
	if got.type2 == pduType2SetErrorInfo {
		return []uint8{got.type2}, fmt.Errorf("%s 后服务端返回 ErrorInfo: code=0x%08x(%s) raw=%s", name, got.errorInfo, rdpErrorInfoName(got.errorInfo), got.rawPrefix)
	}
	return []uint8{got.type2}, nil
}

func waitFinalizeResponses(rw io.ReadWriter, cfg Config, timeout time.Duration) ([]uint8, []mcsDataIndication, error) {
	if conn, ok := rw.(interface{ SetReadDeadline(time.Time) error }); ok {
		_ = conn.SetReadDeadline(time.Now().Add(timeout))
		defer conn.SetReadDeadline(time.Time{})
	}
	expected := []finalizeExpectation{
		{type2: pduType2Synchronize},
		{type2: pduType2Control, action: 0x0004},
		{type2: pduType2Control, action: ctrlActionGrantedControl},
		{type2: pduType2FontMap},
	}
	var types []uint8
	var pending []mcsDataIndication
	for _, want := range expected {
		for {
			payload, err := readNextSlowPathPayload(rw, cfg, timeout)
			if err != nil {
				if errors.Is(err, errFinalizeActive) || len(types) > 0 {
					rdpDebugf(cfg, "finalize accept active session types=%v err=%v", types, err)
					return types, pending, nil
				}
				return types, pending, fmt.Errorf("读取 Client Finalize 响应失败: %w", err)
			}
			data, err := parseMCSDataIndication(payload)
			if err != nil {
				return types, pending, err
			}
			// 虚拟通道数据(cliprdr/rdpdr 等,channel ≠ 1003 global)在 finalize 阶段
			// 先缓存，等 SessionEngine 创建对应 handler 后再分发。 // Logan.Li
			if data.channelID != mcsGlobalChannelID {
				rdpDebugf(cfg, "finalize skip virtual channel data channel=%d payload=%d", data.channelID, len(data.payload))
				pending = append(pending, data)
				continue
			}
			got, err := parseShareDataPDUInfo(data.payload)
			if err != nil {
				return types, pending, err
			}
			types = append(types, got.type2)
			rdpDebugf(cfg, "finalize recv type2=0x%02x action=0x%04x raw=%s", got.type2, got.controlAction, got.rawPrefix)
			if got.type2 == pduType2SetErrorInfo {
				return types, pending, fmt.Errorf("服务端返回 ErrorInfo: code=0x%08x(%s) seen=%v raw=%s", got.errorInfo, rdpErrorInfoName(got.errorInfo), types, got.rawPrefix)
			}
			if got.type2 == pduType2SaveSessionInfo {
				continue
			}
			if got.type2 != want.type2 {
				continue
			}
			if want.type2 == pduType2Control && got.controlAction != want.action {
				continue
			}
			break
		}
	}
	return types, pending, nil
}

func readNextSlowPathPayload(r io.Reader, cfg Config, timeout time.Duration) ([]byte, error) {
	deadline := time.Now().Add(timeout)
	seenFastPath := false
	for {
		pkt, err := ReadWirePacket(r)
		if err != nil {
			if seenFastPath {
				return nil, errFinalizeActive
			}
			return nil, err
		}
		if !pkt.FastPath {
			return pkt.Payload, nil
		}
		seenFastPath = true
		rdpDebugf(cfg, "finalize skip fastpath sec=0x%02x payload=%d", pkt.SecFlag, len(pkt.Payload))
		if time.Now().After(deadline) {
			return nil, errFinalizeActive
		}
	}
}

type finalizeExpectation struct {
	type2  uint8
	action uint16
}

func buildConfirmActivePDU(cfg Config, userID uint16, demand demandActiveProbe) []byte {
	source := demand.sourceDescriptor
	if len(source) == 0 {
		source = []byte("rdpy")
	}
	body := bytes.Buffer{}
	writeLE32(&body, demand.sharedID)
	writeLE16(&body, 0x03ea)
	writeLE16(&body, uint16(len(source)))
	caps, capCount := buildConfirmCapabilities(cfg)
	rdpDebugf(cfg, "build ConfirmActive sourceLen=%d caps=%d capsBytes=%d", len(source), capCount, len(caps))
	debugCapabilityList(cfg, caps)
	writeLE16(&body, uint16(len(caps)+4))
	body.Write(source)
	writeLE16(&body, capCount)
	writeLE16(&body, 0)
	body.Write(caps)
	pdu := buildShareControlPDU(userID, pduTypeConfirmActive, body.Bytes())
	prefixLen := len(pdu)
	if prefixLen > 96 {
		prefixLen = 96
	}
	rdpDebugf(cfg, "ConfirmActive pduLen=%d prefix=%s", len(pdu), hex.EncodeToString(pdu[:prefixLen]))
	return pdu
}

func rdpDebugf(cfg Config, format string, args ...interface{}) {
	if !cfg.Debug {
		return
	}
	_, _ = fmt.Fprintf(os.Stderr, "[rdp] "+format+"\n", args...)
}

func rdpErrorInfoName(code uint32) string {
	switch code {
	case 0x000010EA:
		return "ERRINFO_BAD_CAPABILITIES"
	case 0x000010E9:
		return "ERRINFO_NO_CURSOR_CACHE"
	case 0x000010E8:
		return "ERRINFO_CAPABILITY_SET_TOO_LARGE"
	case 0x000010E7:
		return "ERRINFO_CAPABILITY_SET_TOO_SMALL"
	case 0x000010D4:
		return "ERRINFO_CONFIRM_ACTIVE_HAS_WRONG_SHAREID"
	case 0x000010D5:
		return "ERRINFO_CONFIRM_ACTIVE_HAS_WRONG_ORIGINATOR"
	default:
		return "UNKNOWN"
	}
}

func debugCapabilityList(cfg Config, caps []byte) {
	if !cfg.Debug {
		return
	}
	offset := 0
	index := 0
	for offset+4 <= len(caps) {
		capType := binary.LittleEndian.Uint16(caps[offset : offset+2])
		capLen := int(binary.LittleEndian.Uint16(caps[offset+2 : offset+4]))
		if capLen < 4 || offset+capLen > len(caps) {
			rdpDebugf(cfg, "cap[%02d] invalid offset=%d type=0x%04x len=%d total=%d", index, offset, capType, capLen, len(caps))
			return
		}
		body := caps[offset+4 : offset+capLen]
		prefixLen := len(body)
		if prefixLen > 24 {
			prefixLen = 24
		}
		rdpDebugf(cfg, "cap[%02d] type=0x%04x len=%d body=%s", index, capType, capLen, hex.EncodeToString(body[:prefixLen]))
		offset += capLen
		index++
	}
	if offset != len(caps) {
		rdpDebugf(cfg, "cap trailing bytes=%d offset=%d total=%d", len(caps)-offset, offset, len(caps))
	}
}

func buildConfirmCapabilities(cfg Config) ([]byte, uint16) {
	width := cfg.Width
	if width <= 0 {
		width = 1280
	}
	height := cfg.Height
	if height <= 0 {
		height = 800
	}
	out := bytes.Buffer{}
	count := uint16(0)
	addCapability := func(capType uint16, body []byte) {
		writeCapability(&out, capType, body)
		count++
	}
	if cfg.MCSMode == "comment" || cfg.MCSMode == "step-comment" || cfg.MCSMode == "grdp-comment" || cfg.MCSMode == "step-grdp-comment" {
		return buildGRDPCommentCapabilities(cfg, width, height)
	}
	addCapability(0x0001, buildGeneralCapability())
	bitmap := bytes.Buffer{}
	preferredBPP := uint16(24)
	if cfg.MCSMode == "bpp32" || cfg.MCSMode == "step-bpp32" || cfg.MCSMode == "modern" || cfg.MCSMode == "step-modern" || cfg.MCSMode == "raw" || cfg.MCSMode == "step-raw" || cfg.MCSMode == "grdp-modern" || cfg.MCSMode == "step-grdp-modern" || cfg.MCSMode == "grdp-raw" || cfg.MCSMode == "step-grdp-raw" {
		preferredBPP = 32
	}
	writeLE16(&bitmap, preferredBPP)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, uint16(width))
	writeLE16(&bitmap, uint16(height))
	writeLE16(&bitmap, 0)
	writeLE16(&bitmap, 1)
	if cfg.MCSMode == "raw" || cfg.MCSMode == "step-raw" || cfg.MCSMode == "grdp-raw" || cfg.MCSMode == "step-grdp-raw" {
		writeLE16(&bitmap, 0)
	} else {
		writeLE16(&bitmap, 1)
	}
	writeLE16(&bitmap, 0)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 0)
	addCapability(0x0002, bitmap.Bytes())
	if cfg.MCSMode == "basic" {
		addCapability(0x000d, buildInputCapability())
		return out.Bytes(), count
	}
	if cfg.MCSMode == "legacy" || cfg.MCSMode == "step-legacy" {
		addCapability(0x0003, mustHex("00000000000000000000000000000000010014000000010000000a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008403000000000000000000"))
		addCapability(0x0005, mustHex("0000000002000200"))
		addCapability(0x0007, mustHex("0000000000000000"))
		addCapability(0x0008, buildPointerCapability(128))
		addCapability(0x0009, mustHex("00000000"))
		addCapability(0x000a, mustHex("06000000"))
		addCapability(0x000c, mustHex("01000000"))
		addCapability(0x000d, buildInputCapability())
		addCapability(0x000e, mustHex("01000000"))
		addCapability(0x000f, mustHex("01000000"))
		addCapability(0x0010, make([]byte, 48))
		addCapability(0x0014, mustHex("0000000040060000"))
		return out.Bytes(), count
	}
	if cfg.MCSMode == "minimal" || cfg.MCSMode == "step-minimal" {
		addCapability(0x0003, mustHex("00000000000000000000000000000000010014000000010000000a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008403000000000000000000"))
		addCapability(0x0008, mustHex("00001400"))
		addCapability(0x000d, buildInputCapability())
		addCapability(0x000e, mustHex("01000000"))
		return out.Bytes(), count
	}
	if cfg.MCSMode == "modern" || cfg.MCSMode == "step-modern" || cfg.MCSMode == "raw" || cfg.MCSMode == "step-raw" || cfg.MCSMode == "grdp-modern" || cfg.MCSMode == "step-grdp-modern" || cfg.MCSMode == "grdp-raw" || cfg.MCSMode == "step-grdp-raw" {
		addCapability(0x0003, buildGRDPOrderCapability())
		addCapability(0x0005, mustHex("0000000002000200"))
		addCapability(0x0007, mustHex("0000000000000000"))
		addCapability(0x0008, buildPointerCapability(20))
		addCapability(0x0009, mustHex("00000000"))
		addCapability(0x000a, mustHex("06000000"))
		addCapability(0x000c, mustHex("01000000"))
		addCapability(0x000d, buildInputCapability())
		addCapability(0x000e, mustHex("01000000"))
		addCapability(0x000f, mustHex("01000000"))
		addCapability(0x0010, buildGlyphNoneCapability())
		addCapability(0x001d, buildBitmapCodecsCapability())
		addCapability(0x0013, buildBitmapCacheRev2CapabilityWithPersist(2))
		addCapability(0x0014, mustHex("0000000040060000"))
		addCapability(0x001a, mustHex("00003f00"))
		addCapability(0x0017, mustHex("ff000000"))
		addCapability(0x001b, mustHex("0100"))
		addCapability(0x0019, mustHex("0100"))
		addCapability(0x001c, mustHex("5200000000000000"))
		addCapability(0x001e, mustHex("02000000"))
		return out.Bytes(), count
	}
	addCapability(0x0003, mustHex("00000000000000000000000000000000010014000000010000000a000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008403000000000000000000"))
	addCapability(0x0008, buildPointerCapability(128))
	addCapability(0x000c, mustHex("00000000"))
	addCapability(0x000d, buildInputCapability())
	addCapability(0x000f, mustHex("00000000"))
	addCapability(0x0010, make([]byte, 48))
	addCapability(0x0013, buildBitmapCacheRev2Capability())
	addCapability(0x0011, mustHex("0000000000000000"))
	addCapability(0x0014, mustHex("0000000040060000"))
	addCapability(0x001a, mustHex("00000000"))
	return out.Bytes(), count
}

func buildGRDPCommentCapabilities(cfg Config, width int, height int) ([]byte, uint16) {
	out := bytes.Buffer{}
	count := uint16(0)
	addCapability := func(capType uint16, body []byte) {
		writeCapability(&out, capType, body)
		count++
	}
	addCapability(0x0001, buildGeneralCapability())
	bitmap := bytes.Buffer{}
	writeLE16(&bitmap, 24)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, uint16(width))
	writeLE16(&bitmap, uint16(height))
	writeLE16(&bitmap, 0)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 0)
	writeLE16(&bitmap, 1)
	writeLE16(&bitmap, 0)
	addCapability(0x0002, bitmap.Bytes())
	addCapability(0x0003, mustHex("000000000000000000000000000000000000000000000000010014000000010000000a0000000000000000000000000000000000000000000000000000000000000000000000000000000000008403000000000000000000"))
	addCapability(0x0004, make([]byte, 36))
	addCapability(0x0008, mustHex("00001400"))
	addCapability(0x000c, mustHex("00000000"))
	addCapability(0x000d, buildInputCapability())
	addCapability(0x000f, mustHex("00000000"))
	addCapability(0x0010, buildGlyphNoneCapability())
	addCapability(0x0011, mustHex("0000000000000000"))
	addCapability(0x0014, mustHex("0000000000000000"))
	addCapability(0x001a, mustHex("00000000"))
	rdpDebugf(cfg, "grdp-comment caps=%d bytes=%d", count, out.Len())
	return out.Bytes(), count
}

func buildGRDPOrderCapability() []byte {
	out := bytes.Buffer{}
	out.Write(make([]byte, 16))
	writeLE32(&out, 0)
	writeLE16(&out, 1)
	writeLE16(&out, 20)
	writeLE16(&out, 0)
	writeLE16(&out, 1)
	writeLE16(&out, 0)
	writeLE16(&out, 0x00aa)
	orderSupport := make([]byte, 32)
	// native 暂不处理 Orders，能力集必须全关，避免服务端只发订单导致桌面黑屏 // Logan.Li
	out.Write(orderSupport)
	writeLE16(&out, 0)
	writeLE16(&out, 0x0004)
	writeLE32(&out, 0)
	writeLE32(&out, 480*480)
	writeLE16(&out, 0)
	writeLE16(&out, 0)
	writeLE16(&out, 0x04e4)
	writeLE16(&out, 0)
	return out.Bytes()
}

func buildGeneralCapability() []byte {
	out := bytes.Buffer{}
	writeLE16(&out, 0x0001)
	writeLE16(&out, 0x0003)
	writeLE16(&out, 0x0200)
	writeLE16(&out, 0)
	writeLE16(&out, 0x0002)
	writeLE16(&out, 0x041d)
	writeLE16(&out, 0)
	writeLE16(&out, 0)
	writeLE16(&out, 0)
	out.WriteByte(1)
	out.WriteByte(1)
	return out.Bytes()
}

func buildPointerCapability(cacheSize uint16) []byte {
	out := bytes.Buffer{}
	writeLE16(&out, 1)
	writeLE16(&out, cacheSize)
	writeLE16(&out, cacheSize)
	return out.Bytes()
}

func buildBitmapCacheRev2Capability() []byte {
	return buildBitmapCacheRev2CapabilityWithPersist(0)
}

func buildBitmapCacheRev2CapabilityWithPersist(persist uint16) []byte {
	out := bytes.Buffer{}
	writeLE16(&out, persist)
	out.WriteByte(0)
	out.WriteByte(5)
	for _, cells := range []uint32{0x258, 0x258, 0x800, 0x1000, 0x800} {
		writeLE32(&out, cells)
	}
	out.Write(make([]byte, 12))
	return out.Bytes()
}

func buildGlyphNoneCapability() []byte {
	out := bytes.Buffer{}
	out.Write(make([]byte, 40))
	writeLE32(&out, 0)
	writeLE16(&out, 0)
	writeLE16(&out, 0)
	return out.Bytes()
}

func buildBitmapCodecsCapability() []byte {
	out := bytes.Buffer{}
	out.WriteByte(2)
	out.Write(mustHex("b91b8dca0f004f15589fae2d1a87e2d6"))
	out.WriteByte(1)
	writeLE16(&out, 3)
	out.Write([]byte{1, 1, 3})
	out.Write(mustHex("122f777672bd6344afb3b73c9c6f7886"))
	out.WriteByte(3)
	rfx := buildRemoteFXProperties()
	writeLE16(&out, uint16(len(rfx)))
	out.Write(rfx)
	return out.Bytes()
}

func buildRemoteFXProperties() []byte {
	return mustHex("29000000000000001d000000c0cb080000000100c1cb1500000001c0cf010008000001400001010104")
}

func buildInputCapability() []byte {
	out := bytes.Buffer{}
	writeLE16(&out, 0x003d)
	writeLE16(&out, 0)
	writeLE32(&out, 0x00000409)
	writeLE32(&out, 4)
	writeLE32(&out, 0)
	writeLE32(&out, 12)
	out.Write(make([]byte, 64))
	return out.Bytes()
}

func writeCapability(w io.Writer, capType uint16, body []byte) {
	writeLE16(w, capType)
	writeLE16(w, uint16(len(body)+4))
	_, _ = w.Write(body)
}

func buildShareControlPDU(userID uint16, pduType uint16, body []byte) []byte {
	out := bytes.Buffer{}
	writeLE16(&out, uint16(len(body)+6))
	writeLE16(&out, pduType)
	writeLE16(&out, userID)
	out.Write(body)
	return out.Bytes()
}

func buildDataPDU(userID uint16, sharedID uint32, type2 uint8, body []byte) []byte {
	data := bytes.Buffer{}
	writeLE32(&data, sharedID)
	data.WriteByte(0)
	data.WriteByte(1)
	writeLE16(&data, uint16(len(body)+4))
	data.WriteByte(type2)
	data.WriteByte(0)
	writeLE16(&data, 0)
	data.Write(body)
	return buildShareControlPDU(userID, pduTypeData, data.Bytes())
}

func buildSynchronizeData(userID uint16) []byte {
	out := bytes.Buffer{}
	writeLE16(&out, 1)
	writeLE16(&out, userID)
	return out.Bytes()
}

func buildControlData(action uint16) []byte {
	out := bytes.Buffer{}
	writeLE16(&out, action)
	writeLE16(&out, 0)
	writeLE32(&out, 0)
	return out.Bytes()
}

func buildFontListData() []byte {
	out := bytes.Buffer{}
	writeLE16(&out, 0)
	writeLE16(&out, 0)
	writeLE16(&out, 0x0003)
	writeLE16(&out, 0x0032)
	return out.Bytes()
}

func attachMCSUser(rw io.ReadWriter) (uint16, error) {
	if err := transport.WriteX224Data(rw, buildMCSErectDomainRequest()); err != nil {
		return 0, err
	}
	if err := transport.WriteX224Data(rw, buildMCSAttachUserRequest()); err != nil {
		return 0, err
	}
	payload, err := transport.ReadX224Data(rw)
	if err != nil {
		return 0, err
	}
	return parseMCSAttachUserConfirm(payload)
}

func joinMCSChannel(rw io.ReadWriter, userID uint16, channelID uint16) (uint16, error) {
	if err := transport.WriteX224Data(rw, buildMCSChannelJoinRequest(userID, channelID)); err != nil {
		return 0, err
	}
	payload, err := transport.ReadX224Data(rw)
	if err != nil {
		return 0, err
	}
	return parseMCSChannelJoinConfirm(payload, userID, channelID)
}

func buildMCSErectDomainRequest() []byte {
	out := bytes.Buffer{}
	writeMCSPDUHeader(&out, mcsErectDomainRequest)
	writePERInteger(&out, 0)
	writePERInteger(&out, 0)
	return out.Bytes()
}

func buildMCSAttachUserRequest() []byte {
	out := bytes.Buffer{}
	writeMCSPDUHeader(&out, mcsAttachUserRequest)
	return out.Bytes()
}

func buildMCSChannelJoinRequest(userID uint16, channelID uint16) []byte {
	out := bytes.Buffer{}
	writeMCSPDUHeader(&out, mcsChannelJoinRequest)
	writeBE16Value(&out, userID-mcsUserChannelIDOffset)
	writeBE16Value(&out, channelID)
	return out.Bytes()
}

func buildMCSSendDataRequest(userID uint16, channelID uint16, data []byte) []byte {
	out := bytes.Buffer{}
	writeMCSPDUHeader(&out, mcsSendDataRequest)
	writeBE16Value(&out, userID-mcsUserChannelIDOffset)
	writeBE16Value(&out, channelID)
	out.WriteByte(0x70)
	writePERLength(&out, len(data))
	out.Write(data)
	return out.Bytes()
}

func parseMCSAttachUserConfirm(data []byte) (uint16, error) {
	r := bytes.NewReader(data)
	pdu, err := readMCSPDUHeader(r)
	if err != nil {
		return 0, err
	}
	if pdu != mcsAttachUserConfirm {
		return 0, fmt.Errorf("MCS AttachUserConfirm 类型错误: %d", pdu)
	}
	result, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	if result != 0 {
		return 0, fmt.Errorf("MCS AttachUser 被拒绝: %d", result)
	}
	userID, err := readBE16Value(r)
	if err != nil {
		return 0, err
	}
	return userID + mcsUserChannelIDOffset, nil
}

func parseMCSChannelJoinConfirm(data []byte, expectedUserID uint16, expectedChannelID uint16) (uint16, error) {
	r := bytes.NewReader(data)
	pdu, err := readMCSPDUHeader(r)
	if err != nil {
		return 0, err
	}
	if pdu != mcsChannelJoinConfirm {
		return 0, fmt.Errorf("MCS ChannelJoinConfirm 类型错误: %d", pdu)
	}
	result, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	userID, err := readBE16Value(r)
	if err != nil {
		return 0, err
	}
	userID += mcsUserChannelIDOffset
	channelID, err := readBE16Value(r)
	if err != nil {
		return 0, err
	}
	if userID != expectedUserID {
		return 0, fmt.Errorf("MCS ChannelJoin 用户不匹配: got=%d want=%d", userID, expectedUserID)
	}
	if channelID != expectedChannelID {
		return 0, fmt.Errorf("MCS ChannelJoin 通道不匹配: got=%d want=%d", channelID, expectedChannelID)
	}
	if result != 0 && (channelID == mcsGlobalChannelID || channelID == expectedUserID) {
		return 0, fmt.Errorf("MCS 必需通道加入失败: channel=%d result=%d", channelID, result)
	}
	return channelID, nil
}

// ParseMCSChannel 解析 MCS SendDataIndication,返回 channel ID(探针诊断用)。// Logan.Li
func ParseMCSChannel(data []byte) (uint16, error) {
	ind, err := parseMCSDataIndication(data)
	if err != nil {
		return 0, err
	}
	return ind.channelID, nil
}

func parseMCSDataIndication(data []byte) (mcsDataIndication, error) {
	r := bytes.NewReader(data)
	pdu, err := readMCSPDUHeader(r)
	if err != nil {
		return mcsDataIndication{}, err
	}
	if pdu != mcsSendDataIndication {
		return mcsDataIndication{}, fmt.Errorf("MCS DataIndication 类型错误: %d", pdu)
	}
	if _, err := readBE16Value(r); err != nil {
		return mcsDataIndication{}, err
	}
	channelID, err := readBE16Value(r)
	if err != nil {
		return mcsDataIndication{}, err
	}
	if _, err := r.ReadByte(); err != nil {
		return mcsDataIndication{}, err
	}
	size, err := readPERLength(r)
	if err != nil {
		return mcsDataIndication{}, err
	}
	if int(size) > r.Len() {
		return mcsDataIndication{}, io.ErrUnexpectedEOF
	}
	payload := make([]byte, int(size))
	_, _ = io.ReadFull(r, payload)
	flags := uint16(0)
	if len(payload) >= 4 {
		flags = binary.LittleEndian.Uint16(payload[0:2])
	}
	return mcsDataIndication{channelID: channelID, securityFlags: flags, payload: payload}, nil
}

func parseLicensePacket(data *mcsDataIndication) error {
	if len(data.payload) < 8 {
		return fmt.Errorf("License PDU 太短: %d", len(data.payload))
	}
	body := data.payload[4:]
	data.licenseMsgType = body[0]
	if len(body) >= 12 && data.licenseMsgType == licenseErrorAlert {
		data.licenseErrorCode = binary.LittleEndian.Uint32(body[4:8])
		data.licenseState = binary.LittleEndian.Uint32(body[8:12])
		if data.licenseErrorCode == licenseStatusValid && data.licenseState == licenseStateNoTransit {
			return nil
		}
		return fmt.Errorf("License ErrorAlert: code=0x%08x state=0x%08x", data.licenseErrorCode, data.licenseState)
	}
	return fmt.Errorf("暂未实现 License msgType=0x%02x 的响应", data.licenseMsgType)
}

func parseDemandActiveProbe(payload []byte) (demandActiveProbe, error) {
	r := bytes.NewReader(payload)
	totalLength, err := readLE16(r)
	if err != nil {
		return demandActiveProbe{}, err
	}
	pduType, err := readLE16(r)
	if err != nil {
		return demandActiveProbe{}, err
	}
	if int(totalLength) > len(payload) {
		return demandActiveProbe{}, fmt.Errorf("Share Control 长度超出数据: total=%d payload=%d", totalLength, len(payload))
	}
	if pduType != pduTypeDemandActive {
		return demandActiveProbe{pduType: pduType}, fmt.Errorf("等待 DemandActive，收到 PDU type=0x%04x", pduType)
	}
	if _, err := readLE16(r); err != nil {
		return demandActiveProbe{}, err
	}
	sharedID, err := readLE32(r)
	if err != nil {
		return demandActiveProbe{}, err
	}
	sourceLen, err := readLE16(r)
	if err != nil {
		return demandActiveProbe{}, err
	}
	if _, err := readLE16(r); err != nil {
		return demandActiveProbe{}, err
	}
	if int(sourceLen) > r.Len() {
		return demandActiveProbe{}, io.ErrUnexpectedEOF
	}
	source := make([]byte, int(sourceLen))
	_, _ = io.ReadFull(r, source)
	capabilityCount, err := readLE16(r)
	if err != nil {
		return demandActiveProbe{}, err
	}
	return demandActiveProbe{pduType: pduType, sharedID: sharedID, capabilityCount: capabilityCount, sourceDescriptor: source}, nil
}

func parseShareDataPDUType(payload []byte) (uint8, error) {
	info, err := parseShareDataPDUInfo(payload)
	if err != nil {
		return 0, err
	}
	return info.type2, nil
}

type shareDataPDUInfo struct {
	type2         uint8
	controlAction uint16
	errorInfo     uint32
	rawPrefix     string
}

func parseShareDataPDUInfo(payload []byte) (shareDataPDUInfo, error) {
	if len(payload) < 18 {
		return shareDataPDUInfo{}, fmt.Errorf("Share Data PDU 太短: %d", len(payload))
	}
	pduType := binary.LittleEndian.Uint16(payload[2:4])
	if pduType != pduTypeData {
		return shareDataPDUInfo{}, fmt.Errorf("等待 Data PDU，收到 type=0x%04x", pduType)
	}
	prefixLen := len(payload)
	if prefixLen > 32 {
		prefixLen = 32
	}
	info := shareDataPDUInfo{type2: payload[14], rawPrefix: hex.EncodeToString(payload[:prefixLen])}
	if info.type2 == pduType2Control {
		if len(payload) < 20 {
			return shareDataPDUInfo{}, fmt.Errorf("Control Data PDU 太短: %d", len(payload))
		}
		info.controlAction = binary.LittleEndian.Uint16(payload[18:20])
	}
	if info.type2 == pduType2SetErrorInfo {
		if len(payload) < 22 {
			return shareDataPDUInfo{}, fmt.Errorf("ErrorInfo Data PDU 太短: %d", len(payload))
		}
		info.errorInfo = binary.LittleEndian.Uint32(payload[18:22])
	}
	return info, nil
}

func mustHex(value string) []byte {
	data, err := hex.DecodeString(value)
	if err != nil {
		panic(err)
	}
	return data
}

func buildClientInfoPDU(cfg Config) []byte {
	info := buildRDPInfo(cfg)
	out := bytes.Buffer{}
	writeLE16(&out, secFlagInfoPkt)
	writeLE16(&out, 0)
	out.Write(info)
	return out.Bytes()
}

func buildRDPInfo(cfg Config) []byte {
	domain := utf16LENull(cfg.Domain)
	user := utf16LENull(cfg.Username)
	password := utf16LENull(cfg.Password)
	alternateShell := []byte{0, 0}
	workingDir := []byte{0, 0}
	flags := uint32(0x00000001 | 0x00000002 | 0x00000008 | 0x00000010 | 0x00000020 | 0x00000040 | 0x00000100 | 0x00004000 | 0x00010000 | 0x00020000)
	if cfg.MCSMode == "plain-info" || cfg.MCSMode == "step-plain-info" {
		flags = 0x00000001 | 0x00000002 | 0x00000008 | 0x00004000
	}

	out := bytes.Buffer{}
	writeLE32(&out, 0)
	writeLE32(&out, flags)
	writeLE16(&out, uint16(len(domain)-2))
	writeLE16(&out, uint16(len(user)-2))
	writeLE16(&out, uint16(len(password)-2))
	writeLE16(&out, uint16(len(alternateShell)-2))
	writeLE16(&out, uint16(len(workingDir)-2))
	out.Write(domain)
	out.Write(user)
	out.Write(password)
	out.Write(alternateShell)
	out.Write(workingDir)
	out.Write(buildExtendedInfo())
	return out.Bytes()
}

func buildExtendedInfo() []byte {
	clientAddress := []byte{0, 0}
	clientDir := []byte{0, 0}
	out := bytes.Buffer{}
	writeLE16(&out, 0x0002)
	writeLE16(&out, uint16(len(clientAddress)))
	out.Write(clientAddress)
	writeLE16(&out, uint16(len(clientDir)))
	out.Write(clientDir)
	out.Write(make([]byte, 172))
	writeLE32(&out, 0)
	writeLE32(&out, 0x00000001|0x00000002|0x00000004|0x00000080|0x00000100)
	return out.Bytes()
}

func buildMCSConnectInitial(cfg Config) []byte {
	userData := bytes.Buffer{}
	userData.Write(buildGCCClientCore(cfg))
	userData.Write(buildGCCClientNetwork())
	userData.Write(buildGCCClientSecurity())
	userData.Write(buildGCCClientMessageChannel())
	conference := buildGCCConferenceCreate(userData.Bytes())

	body := bytes.Buffer{}
	writeBEROctetString(bodyWriter(&body), []byte{0x01})
	writeBEROctetString(bodyWriter(&body), []byte{0x01})
	writeBERBoolean(bodyWriter(&body), true)
	writeBERDomainParameters(bodyWriter(&body), 34, 2, 0, 0xffff)
	writeBERDomainParameters(bodyWriter(&body), 1, 1, 1, 0x0420)
	writeBERDomainParameters(bodyWriter(&body), 0xffff, 0xfc17, 0xffff, 0xffff)
	writeBEROctetString(bodyWriter(&body), conference)

	out := bytes.Buffer{}
	writeBERApplicationTag(bodyWriter(&out), mcsConnectInitial, body.Len())
	out.Write(body.Bytes())
	return out.Bytes()
}

func buildGCCClientCore(cfg Config) []byte {
	width := cfg.Width
	if width <= 0 {
		width = 1280
	}
	height := cfg.Height
	if height <= 0 {
		height = 800
	}
	highColorDepth := uint16(24)
	supportedColorDepths := uint16(0x000f)
	if cfg.MCSMode == "bpp32" || cfg.MCSMode == "step-bpp32" || cfg.MCSMode == "modern" || cfg.MCSMode == "step-modern" || cfg.MCSMode == "grdp-modern" || cfg.MCSMode == "step-grdp-modern" {
		highColorDepth = 32
		supportedColorDepths = 0x001f
	}
	body := bytes.Buffer{}
	writeLE32(&body, 0x00080007)
	writeLE16(&body, uint16(width))
	writeLE16(&body, uint16(height))
	writeLE16(&body, 0xCA01)
	writeLE16(&body, 0xAA03)
	writeLE32(&body, 0x00000409)
	writeLE32(&body, 22621)
	body.Write(fixedUTF16LE("AIOPS", 32))
	writeLE32(&body, 4)
	writeLE32(&body, 0)
	writeLE32(&body, 12)
	body.Write(make([]byte, 64))
	writeLE16(&body, 0xCA01)
	writeLE16(&body, 1)
	writeLE32(&body, 0)
	writeLE16(&body, highColorDepth)
	writeLE16(&body, supportedColorDepths)
	writeLE16(&body, 0x00a3)
	body.Write(make([]byte, 64))
	body.WriteByte(0x06)
	body.WriteByte(0)
	writeLE32(&body, transport.ProtocolCredSSP)
	return withGCCBlock(gccCSCore, body.Bytes())
}

// declaredStaticChannels 是客户端在 MCS Connect-Initial 里声明的静态虚拟通道。
// 顺序与服务端 Connect-Response 的 SCNet.ChannelIdArray 一一对应，保持接近 MSTSC/FreeRDP 的通道组合。// Logan.Li
var declaredStaticChannels = []struct {
	Name    string
	Options uint32
}{
	{Name: channelNameRdpdr, Options: channelOptionInitialized | channelOptionEncryptRDP},
	{Name: channelNameRdpsnd, Options: channelOptionInitialized | channelOptionEncryptRDP},
	{Name: channelNameCliprdr, Options: channelOptionInitialized | channelOptionEncryptRDP | channelOptionShowProtocol},
	{Name: channelNameDrdynvc, Options: channelOptionInitialized | channelOptionCompressRDP},
}

func buildGCCClientNetwork() []byte {
	body := bytes.Buffer{}
	writeLE32(&body, uint32(len(declaredStaticChannels))) // channelCount
	for _, ch := range declaredStaticChannels {
		// channel name: 8 字节 ASCII，不足补 0 // Logan.Li
		nameBuf := make([]byte, 8)
		copy(nameBuf, ch.Name)
		body.Write(nameBuf)
		writeLE32(&body, ch.Options)
	}
	return withGCCBlock(gccCSNet, body.Bytes())
}

func buildGCCClientSecurity() []byte {
	body := bytes.Buffer{}
	writeLE32(&body, 0x0000000b)
	writeLE32(&body, 0)
	return withGCCBlock(gccCSSecurity, body.Bytes())
}

func buildGCCClientMessageChannel() []byte {
	body := bytes.Buffer{}
	writeLE32(&body, 0)
	return withGCCBlock(0xC006, body.Bytes())
}

func withGCCBlock(blockType uint16, body []byte) []byte {
	out := bytes.Buffer{}
	writeLE16(&out, blockType)
	writeLE16(&out, uint16(len(body)+4))
	out.Write(body)
	return out.Bytes()
}

func buildGCCConferenceCreate(userData []byte) []byte {
	out := bytes.Buffer{}
	writePERChoice(&out, 0)
	writePERObjectIdentifier(&out, []byte{0, 0, 20, 124, 0, 1})
	writePERLength(&out, len(userData)+14)
	writePERChoice(&out, 0)
	out.WriteByte(0x08)
	writePERNumericString(&out, "1", 1)
	out.WriteByte(0)
	out.WriteByte(1)
	writePERChoice(&out, 0xc0)
	writePEROctetStream(&out, []byte("Duca"), 4)
	writePEROctetStream(&out, userData, 0)
	return out.Bytes()
}

func parseMCSConnectResponse(data []byte) (MCSProbeInfo, error) {
	r := bytes.NewReader(data)
	if err := readBERApplicationTag(r, mcsConnectResponse); err != nil {
		return MCSProbeInfo{}, err
	}
	if _, err := readBEREnumerated(r); err != nil {
		return MCSProbeInfo{}, err
	}
	if _, err := readBERInteger(r); err != nil {
		return MCSProbeInfo{}, err
	}
	if err := skipBERDomainParameters(r); err != nil {
		return MCSProbeInfo{}, err
	}
	userData, err := readBEROctetString(r)
	if err != nil {
		return MCSProbeInfo{}, err
	}
	info := MCSProbeInfo{UserDataBytes: len(userData)}
	parseGCCConferenceResponse(userData, &info)
	return info, nil
}

func parseGCCConferenceResponse(data []byte, info *MCSProbeInfo) {
	r := bytes.NewReader(data)
	_, _ = r.ReadByte()
	_ = readPERObjectIdentifier(r, []byte{0, 0, 20, 124, 0, 1})
	_, _ = readPERLength(r)
	_, _ = r.ReadByte()
	_, _ = readBE16(r)
	_, _ = readPERInteger(r)
	_, _ = r.ReadByte()
	_, _ = r.ReadByte()
	_, _ = r.ReadByte()
	if !readPEROctetStreamMatch(r, []byte("McDn"), 4) {
		return
	}
	total, _ := readPERLength(r)
	for total >= 4 && r.Len() >= 4 {
		blockType, _ := readLE16(r)
		blockLen, _ := readLE16(r)
		if blockLen < 4 || int(blockLen-4) > r.Len() {
			return
		}
		body := make([]byte, int(blockLen-4))
		_, _ = io.ReadFull(r, body)
		total -= blockLen
		parseGCCServerBlock(blockType, body, info)
	}
}

func parseGCCServerBlock(blockType uint16, body []byte, info *MCSProbeInfo) {
	r := bytes.NewReader(body)
	switch blockType {
	case gccSCCore:
		info.ServerCoreVersion, _ = readLE32(r)
	case gccSCSecurity:
		info.ServerEncryption, _ = readLE32(r)
		info.ServerEncryptionLvl, _ = readLE32(r)
	case gccSCNet:
		info.ServerChannelID, _ = readLE16(r)
		info.ServerChannelCount, _ = readLE16(r)
		for i := 0; i < int(info.ServerChannelCount) && r.Len() >= 2; i++ {
			channelID, _ := readLE16(r)
			info.ServerChannelIDs = append(info.ServerChannelIDs, channelID)
			// 与 buildGCCClientNetwork 声明的 declaredStaticChannels 按顺序对应，建立 ID→名称映射。 // Logan.Li
			if i < len(declaredStaticChannels) {
				if info.ChannelNameByID == nil {
					info.ChannelNameByID = make(map[uint16]string)
				}
				info.ChannelNameByID[channelID] = declaredStaticChannels[i].Name
			}
		}
	case 0x0C04:
		info.MessageChannelID, _ = readLE16(r)
	}
}

type bodyWriter interface {
	Write([]byte) (int, error)
	WriteByte(byte) error
}

func writeBERApplicationTag(w bodyWriter, tag int, size int) {
	w.WriteByte(0x7f)
	w.WriteByte(byte(tag))
	writeBERLength(w, size)
}

func readBERApplicationTag(r *bytes.Reader, tag int) error {
	first, err := r.ReadByte()
	if err != nil {
		return err
	}
	if first != 0x7f {
		return fmt.Errorf("MCS BER application tag 头错误: 0x%x", first)
	}
	got, err := r.ReadByte()
	if err != nil {
		return err
	}
	if int(got) != tag {
		return fmt.Errorf("MCS BER application tag 不匹配: 0x%x", got)
	}
	_, err = readBERLength(r)
	return err
}

func writeBERDomainParameters(w bodyWriter, maxChannelIDs, maxUserIDs, maxTokenIDs, maxPDUSize int) {
	body := bytes.Buffer{}
	writeBERInteger(&body, maxChannelIDs)
	writeBERInteger(&body, maxUserIDs)
	writeBERInteger(&body, maxTokenIDs)
	writeBERInteger(&body, 1)
	writeBERInteger(&body, 0)
	writeBERInteger(&body, 1)
	writeBERInteger(&body, maxPDUSize)
	writeBERInteger(&body, 2)
	w.WriteByte(0x30)
	writeBERLength(w, body.Len())
	w.Write(body.Bytes())
}

func skipBERDomainParameters(r *bytes.Reader) error {
	tag, err := r.ReadByte()
	if err != nil {
		return err
	}
	if tag != 0x30 {
		return fmt.Errorf("MCS DomainParameters tag 错误: 0x%x", tag)
	}
	size, err := readBERLength(r)
	if err != nil {
		return err
	}
	if size > r.Len() {
		return io.ErrUnexpectedEOF
	}
	_, err = r.Seek(int64(size), io.SeekCurrent)
	return err
}

func writeBEROctetString(w bodyWriter, data []byte) {
	w.WriteByte(0x04)
	writeBERLength(w, len(data))
	w.Write(data)
}

func readBEROctetString(r *bytes.Reader) ([]byte, error) {
	tag, err := r.ReadByte()
	if err != nil {
		return nil, err
	}
	if tag != 0x04 {
		return nil, fmt.Errorf("MCS octet string tag 错误: 0x%x", tag)
	}
	size, err := readBERLength(r)
	if err != nil {
		return nil, err
	}
	if size > r.Len() {
		return nil, io.ErrUnexpectedEOF
	}
	out := make([]byte, size)
	_, err = io.ReadFull(r, out)
	return out, err
}

func writeBERBoolean(w bodyWriter, value bool) {
	w.WriteByte(0x01)
	w.WriteByte(1)
	if value {
		w.WriteByte(0xff)
		return
	}
	w.WriteByte(0)
}

func writeBERInteger(w bodyWriter, value int) {
	w.WriteByte(0x02)
	switch {
	case value <= 0xff:
		w.WriteByte(1)
		w.WriteByte(byte(value))
	case value <= 0xffff:
		w.WriteByte(2)
		var b [2]byte
		binary.BigEndian.PutUint16(b[:], uint16(value))
		w.Write(b[:])
	default:
		w.WriteByte(4)
		var b [4]byte
		binary.BigEndian.PutUint32(b[:], uint32(value))
		w.Write(b[:])
	}
}

func readBERInteger(r *bytes.Reader) (int, error) {
	tag, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	if tag != 0x02 {
		return 0, fmt.Errorf("MCS integer tag 错误: 0x%x", tag)
	}
	size, err := readBERLength(r)
	if err != nil {
		return 0, err
	}
	if size > 4 || size > r.Len() {
		return 0, io.ErrUnexpectedEOF
	}
	raw := make([]byte, size)
	_, _ = io.ReadFull(r, raw)
	value := 0
	for _, b := range raw {
		value = value<<8 | int(b)
	}
	return value, nil
}

func readBEREnumerated(r *bytes.Reader) (byte, error) {
	tag, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	if tag != 0x0a {
		return 0, fmt.Errorf("MCS enumerated tag 错误: 0x%x", tag)
	}
	size, err := readBERLength(r)
	if err != nil {
		return 0, err
	}
	if size != 1 {
		return 0, fmt.Errorf("MCS enumerated 长度错误: %d", size)
	}
	return r.ReadByte()
}

func writeBERLength(w bodyWriter, size int) {
	if size > 0x7f {
		w.WriteByte(0x82)
		var b [2]byte
		binary.BigEndian.PutUint16(b[:], uint16(size))
		w.Write(b[:])
		return
	}
	w.WriteByte(byte(size))
}

func readBERLength(r *bytes.Reader) (int, error) {
	first, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	if first&0x80 == 0 {
		return int(first), nil
	}
	count := int(first & 0x7f)
	if count == 0 || count > 2 || count > r.Len() {
		return 0, fmt.Errorf("BER length 字节数非法: %d", count)
	}
	value := 0
	for i := 0; i < count; i++ {
		b, _ := r.ReadByte()
		value = value<<8 | int(b)
	}
	return value, nil
}

func writePERChoice(w bodyWriter, choice byte) {
	w.WriteByte(choice)
}

func writePERInteger(w bodyWriter, value int) {
	if value <= 0xff {
		writePERLength(w, 1)
		w.WriteByte(byte(value))
		return
	}
	if value <= 0xffff {
		writePERLength(w, 2)
		var b [2]byte
		binary.BigEndian.PutUint16(b[:], uint16(value))
		w.Write(b[:])
		return
	}
	writePERLength(w, 4)
	var b [4]byte
	binary.BigEndian.PutUint32(b[:], uint32(value))
	w.Write(b[:])
}

func writePERObjectIdentifier(w bodyWriter, oid []byte) {
	w.WriteByte(5)
	w.WriteByte((oid[0] << 4) | (oid[1] & 0x0f))
	w.Write(oid[2:6])
}

func readPERObjectIdentifier(r *bytes.Reader, oid []byte) bool {
	size, err := r.ReadByte()
	if err != nil || size != 5 || r.Len() < 5 {
		return false
	}
	raw := make([]byte, 5)
	_, _ = io.ReadFull(r, raw)
	got := []byte{raw[0] >> 4, raw[0] & 0x0f, raw[1], raw[2], raw[3], raw[4]}
	return bytes.Equal(got, oid)
}

func writePERLength(w bodyWriter, size int) {
	if size > 0x7f {
		var b [2]byte
		binary.BigEndian.PutUint16(b[:], uint16(size|0x8000))
		w.Write(b[:])
		return
	}
	w.WriteByte(byte(size))
}

func readPERLength(r *bytes.Reader) (uint16, error) {
	first, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	if first&0x80 == 0 {
		return uint16(first), nil
	}
	next, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	return uint16(first&0x7f)<<8 | uint16(next), nil
}

func writePERNumericString(w bodyWriter, s string, minValue int) {
	length := len(s)
	encodedLength := minValue
	if length >= minValue {
		encodedLength = length - minValue
	}
	writePERLength(w, encodedLength)
	for i := 0; i < length; i += 2 {
		left := (s[i] - '0') % 10
		right := byte(0)
		if i+1 < length {
			right = (s[i+1] - '0') % 10
		}
		w.WriteByte((left << 4) | right)
	}
}

func writePEROctetStream(w bodyWriter, data []byte, minValue int) {
	encodedLength := minValue
	if len(data) >= minValue {
		encodedLength = len(data) - minValue
	}
	writePERLength(w, encodedLength)
	w.Write(data)
}

func readPEROctetStreamMatch(r *bytes.Reader, expected []byte, minValue int) bool {
	encodedLength, err := readPERLength(r)
	if err != nil {
		return false
	}
	size := int(encodedLength) + minValue
	if size != len(expected) || size > r.Len() {
		return false
	}
	raw := make([]byte, size)
	_, _ = io.ReadFull(r, raw)
	return bytes.Equal(raw, expected)
}

func readPERInteger(r *bytes.Reader) (uint32, error) {
	size, err := readPERLength(r)
	if err != nil {
		return 0, err
	}
	if int(size) > r.Len() {
		return 0, io.ErrUnexpectedEOF
	}
	switch size {
	case 1:
		b, _ := r.ReadByte()
		return uint32(b), nil
	case 2:
		return readBE16(r)
	case 4:
		return readBE32(r)
	default:
		_, _ = r.Seek(int64(size), io.SeekCurrent)
		return 0, nil
	}
}

func fixedUTF16LE(value string, size int) []byte {
	out := make([]byte, size)
	encoded := utf16.Encode([]rune(value))
	for i, r := range encoded {
		offset := i * 2
		if offset+1 >= len(out) {
			break
		}
		binary.LittleEndian.PutUint16(out[offset:offset+2], r)
	}
	return out
}

func utf16LENull(value string) []byte {
	out := bytes.Buffer{}
	for _, r := range utf16.Encode([]rune(value)) {
		writeLE16(&out, r)
	}
	writeLE16(&out, 0)
	return out.Bytes()
}

func writeLE16(w io.Writer, value uint16) {
	var b [2]byte
	binary.LittleEndian.PutUint16(b[:], value)
	_, _ = w.Write(b[:])
}

func writeLE32(w io.Writer, value uint32) {
	var b [4]byte
	binary.LittleEndian.PutUint32(b[:], value)
	_, _ = w.Write(b[:])
}

func readLE16(r io.Reader) (uint16, error) {
	var b [2]byte
	_, err := io.ReadFull(r, b[:])
	return binary.LittleEndian.Uint16(b[:]), err
}

func readLE32(r io.Reader) (uint32, error) {
	var b [4]byte
	_, err := io.ReadFull(r, b[:])
	return binary.LittleEndian.Uint32(b[:]), err
}

func readBE16(r io.Reader) (uint32, error) {
	var b [2]byte
	_, err := io.ReadFull(r, b[:])
	return uint32(binary.BigEndian.Uint16(b[:])), err
}

func readBE32(r io.Reader) (uint32, error) {
	var b [4]byte
	_, err := io.ReadFull(r, b[:])
	return binary.BigEndian.Uint32(b[:]), err
}

func writeMCSPDUHeader(w bodyWriter, pduType byte) {
	w.WriteByte(pduType << 2)
}

func readMCSPDUHeader(r *bytes.Reader) (byte, error) {
	header, err := r.ReadByte()
	if err != nil {
		return 0, err
	}
	return header >> 2, nil
}

func writeBE16Value(w bodyWriter, value uint16) {
	var b [2]byte
	binary.BigEndian.PutUint16(b[:], value)
	w.Write(b[:])
}

func readBE16Value(r io.Reader) (uint16, error) {
	var b [2]byte
	_, err := io.ReadFull(r, b[:])
	return binary.BigEndian.Uint16(b[:]), err
}