mk6i-open-oscar-server/server/icq_legacy/v2_handler.go

package icq_legacy

import (
	"bytes"
	"context"
	"encoding/binary"
	"fmt"
	"log/slog"
	"net"
	"time"

	"github.com/mk6i/open-oscar-server/state"
)

// V2Handler handles ICQ V2 protocol packets
type V2Handler struct {
	BaseHandler
	packetBuilder V2PacketBuilder
	dispatcher    MessageDispatcher
}

// NewV2Handler creates a new V2 protocol handler
func NewV2Handler(
	sessions *LegacySessionManager,
	service LegacyService,
	sender PacketSender,
	packetBuilder V2PacketBuilder,
	logger *slog.Logger,
) *V2Handler {
	return &V2Handler{
		BaseHandler: BaseHandler{
			sessions: sessions,
			service:  service,
			sender:   sender,
			logger:   logger,
		},
		packetBuilder: packetBuilder,
	}
}

// SetSender sets the packet sender (for circular dependency resolution)
func (h *V2Handler) SetSender(sender PacketSender) {
	h.sender = sender
}

// SetDispatcher sets the message dispatcher for cross-protocol message routing
func (h *V2Handler) SetDispatcher(dispatcher MessageDispatcher) {
	h.dispatcher = dispatcher
}

// Handle processes a V2 protocol packet
func (h *V2Handler) Handle(session *LegacySession, addr *net.UDPAddr, packet []byte) error {
	// Debug: dump raw packet
	h.logger.Debug("raw V2 packet",
		"hex", fmt.Sprintf("%X", packet),
		"len", len(packet),
	)

	pkt, err := UnmarshalV2ClientPacket(packet)
	if err != nil {
		return fmt.Errorf("parsing V2 packet: %w", err)
	}

	h.logger.Debug("V2 packet received",
		"command", fmt.Sprintf("0x%04X", pkt.Command),
		"uin", pkt.UIN,
		"seq", pkt.SeqNum,
		"addr", addr.String(),
		"data_hex", fmt.Sprintf("%X", pkt.Data),
	)

	// Update session activity if we have one
	if session != nil {
		session.UpdateActivity()
		session.SeqNumClient = pkt.SeqNum
	}

	// If no session exists and this is not a login/registration/ack command,
	// send NOT_CONNECTED to force the client to reconnect.
	if session == nil {
		switch pkt.Command {
		case ICQLegacyCmdAck, ICQLegacyCmdLogin,
			ICQLegacyCmdFirstLogin, ICQLegacyCmdGetDeps,
			ICQLegacyCmdRegNewUser, ICQLegacyCmdExtInfoReq:
			// Allow these through - they don't require a session
		default:
			h.logger.Info("V2 packet from unknown session, sending NOT_CONNECTED",
				"command", fmt.Sprintf("0x%04X", pkt.Command),
				"uin", pkt.UIN,
				"addr", addr.String(),
			)
			return h.sendNotConnectedToAddr(addr, pkt.SeqNum)
		}
	}

	switch pkt.Command {
	case ICQLegacyCmdAck:
		return h.handleAck(session, pkt)
	case ICQLegacyCmdLogin:
		return h.handleLogin(session, addr, pkt)
	case ICQLegacyCmdLogoff:
		return h.handleLogoff(session, pkt)
	case ICQLegacyCmdKeepAlive, ICQLegacyCmdKeepAlive2:
		return h.handleKeepAlive(session, pkt)
	case ICQLegacyCmdContactList:
		return h.handleContactList(session, pkt)
	case ICQLegacyCmdThruServer:
		return h.handleSendMessage(session, pkt)
	case ICQLegacyCmdAuthorize:
		return h.handleAuthorize(session, pkt)
	case ICQLegacyCmdSetStatus:
		return h.handleSetStatus(session, pkt)
	case ICQLegacyCmdInfoReq:
		return h.handleInfoReq(session, pkt)
	case ICQLegacyCmdExtInfoReq:
		return h.handleExtInfoReq(session, addr, pkt)
	case ICQLegacyCmdSearchUIN:
		return h.handleSearchUIN(session, pkt)
	case ICQLegacyCmdSearchUser:
		return h.handleSearchUser(session, pkt)
	case ICQLegacyCmdSysMsgReq:
		return h.handleOfflineMsgReq(session, pkt)
	case ICQLegacyCmdSysMsgDoneAck:
		return h.handleOfflineMsgAck(session, pkt)
	case ICQLegacyCmdVisibleList:
		return h.handleVisibleList(session, pkt)
	case ICQLegacyCmdInvisibleList:
		return h.handleInvisibleList(session, pkt)
	case ICQLegacyCmdUserAdd:
		return h.handleUserAdd(session, pkt)
	case ICQLegacyCmdUpdateBasic, ICQLegacyCmdSetBasicInfo:
		return h.handleUpdateBasic(session, pkt)
	case ICQLegacyCmdUpdateDetail:
		return h.handleUpdateDetail(session, pkt)
	case ICQLegacyCmdGetDeps:
		// 0x03F2 - Pre-auth pseudo-login (historically "get departments list" in iserverd).
		// Some clients send version=2 in the header but use V3 packet structure.
		// We re-parse the raw packet as V3 format (12-byte header) inline.
		return h.handleGetDeps(addr, packet)
	case ICQLegacyCmdFirstLogin:
		return h.handleFirstLogin(session, addr, pkt)
	case ICQLegacyCmdRegNewUser:
		return h.handleRegNewUser(addr, pkt)
	default:
		h.logger.Debug("unhandled V2 command",
			"command", fmt.Sprintf("0x%04X", pkt.Command),
			"uin", pkt.UIN,
		)
		// Send ACK for unknown commands to keep client happy
		if session != nil {
			return h.sendAck(session, pkt.SeqNum)
		}
		return nil
	}
}

// handleAck processes an acknowledgment packet
func (h *V2Handler) handleAck(session *LegacySession, pkt *V2ClientPacket) error {
	// ACKs don't require a response
	h.logger.Debug("received ACK", "seq", pkt.SeqNum)
	return nil
}

// handleLogin processes a login request
// Refactored to use service layer (AuthenticateUser) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
func (h *V2Handler) handleLogin(session *LegacySession, addr *net.UDPAddr, pkt *V2ClientPacket) error {
	ctx := context.Background()

	// 1. Unmarshal packet to typed struct
	loginData, err := ParseV2LoginPacket(pkt.Data)
	if err != nil {
		h.logger.Debug("failed to parse login packet", "err", err)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(pkt.SeqNum, pkt.Version))
	}

	loginData.UIN = pkt.UIN

	// Extract LOGIN_SEQ_NUM from payload.
	// From protocol doc and center-1.10.7 source: after PORT(4) + PASSWORD(2+len),
	// the login_2 struct has: X1(4) + IP(4) + X2(1) + STATUS(4) + X3(4) + SEQ(2)
	// = 17 bytes to reach SEQ. Total offset = 4 + 2 + pwdLen + 17
	var loginSeqNum uint16
	if len(pkt.Data) >= 6 {
		pwdLen := binary.LittleEndian.Uint16(pkt.Data[4:6])
		seqOffset := 4 + 2 + int(pwdLen) + 17
		if seqOffset+2 <= len(pkt.Data) {
			loginSeqNum = binary.LittleEndian.Uint16(pkt.Data[seqOffset : seqOffset+2])
		}
	}

	h.logger.Info("login attempt",
		"uin", pkt.UIN,
		"ip", loginData.IP,
		"port", loginData.Port,
		"status", loginData.Status,
	)

	// 2. Call service layer with typed request
	authReq := AuthRequest{
		UIN:      pkt.UIN,
		Password: loginData.Password,
		Status:   loginData.Status,
		TCPPort:  uint32(loginData.Port),
		Version:  pkt.Version,
	}

	authResult, err := h.service.AuthenticateUser(ctx, authReq)
	if err != nil {
		h.logger.Error("authentication error", "err", err, "uin", pkt.UIN)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(pkt.SeqNum, pkt.Version))
	}

	if !authResult.Success {
		h.logger.Info("login failed - invalid credentials", "uin", pkt.UIN, "error_code", authResult.ErrorCode)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(pkt.SeqNum, pkt.Version))
	}

	// 3. Create session
	newSession, err := h.sessions.CreateSession(pkt.UIN, addr, pkt.Version, authResult.oscarSession)
	if err != nil {
		h.logger.Error("failed to create session", "err", err, "uin", pkt.UIN)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(pkt.SeqNum, pkt.Version))
	}

	newSession.SetStatus(loginData.Status)
	newSession.Password = loginData.Password

	// 4. Send ACK first, then login reply
	ackPkt := h.packetBuilder.BuildAck(pkt.SeqNum, pkt.Version)
	if err := h.sender.SendToSession(newSession, ackPkt); err != nil {
		return err
	}

	// 5. Build and send login reply — echo back LOGIN_SEQ_NUM from payload
	loginReplyPkt := h.packetBuilder.BuildLoginReply(newSession, loginSeqNum)
	if err := h.sender.SendToSession(newSession, loginReplyPkt); err != nil {
		return err
	}

	h.logger.Info("login successful",
		"uin", pkt.UIN,
		"session_id", newSession.SessionID,
	)

	if err := h.service.NotifyUserOnline(ctx, newSession.UIN, newSession.GetStatus()); err != nil {
		h.logger.Debug("V2 failed to notify OSCAR clients of online", "uin", newSession.UIN, "err", err)
	}

	return nil
}

// handleLogoff processes a logout request
func (h *V2Handler) handleLogoff(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	h.logger.Info("logout", "uin", session.UIN)

	// Notify contacts that user is offline
	h.sessions.BroadcastToContacts(session, func(contact *LegacySession) {
		_ = h.sendUserOffline(contact, session.UIN)
	})

	// Notify OSCAR clients that this user went offline
	ctx := context.Background()
	if err := h.service.NotifyUserOffline(ctx, session.UIN); err != nil {
		h.logger.Debug("V2 failed to notify OSCAR clients of offline", "uin", session.UIN, "err", err)
	}

	// Remove session
	h.sessions.RemoveSession(session.UIN)

	return nil
}

// sendNotConnectedToAddr sends a NOT_CONNECTED (0x00F0) response to a V2 client
// address that has no session. This forces the client to reconnect.
// Uses V2 server packet format: VERSION(2) + COMMAND(2) + SEQ(2)
func (h *V2Handler) sendNotConnectedToAddr(addr *net.UDPAddr, seqNum uint16) error {
	pkt := MarshalV2ServerPacket(&V2ServerPacket{
		Version: ICQLegacyVersionV2,
		Command: ICQLegacySrvNotConnected,
		SeqNum:  seqNum,
	})
	return h.sender.SendPacket(addr, pkt)
}

// handleKeepAlive processes a keep-alive ping
func (h *V2Handler) handleKeepAlive(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil // Already handled by the session-nil guard above
	}

	// Session activity already updated, just send ACK
	return h.sendAck(session, pkt.SeqNum)
}

// handleContactList processes a contact list update
// Refactored to use service layer (ProcessContactList) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
//
// IMPORTANT: The client uses SendExpectEvent() which retransmits until it
// receives SRV_ACK with the matching sequence number. We must send ACK first,
// then the data responses. Without the ACK, the client retransmits in a loop.
func (h *V2Handler) handleContactList(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first to stop client retransmission
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// 1. Unmarshal packet to typed struct
	contactList, err := ParseV2ContactList(pkt.Data)
	if err != nil {
		h.logger.Debug("failed to parse contact list", "err", err)
		return nil
	}

	h.logger.Debug("contact list received",
		"uin", session.UIN,
		"contacts", len(contactList.UINs),
	)

	// Update session contact list (handler responsibility - session management)
	session.SetContactList(contactList.UINs)

	// 2. Call service layer with typed request
	contactReq := ContactListRequest{
		UIN:      session.UIN,
		Contacts: contactList.UINs,
	}

	contactResult, err := h.service.ProcessContactList(ctx, session.Instance, contactReq)
	if err != nil {
		h.logger.Debug("failed to process contact list", "err", err)
		// Still send contact list done even on error
		return h.sender.SendToSession(session, h.packetBuilder.BuildContactListDone(session.NextServerSeqNum(), session.UIN))
	}

	// 3. Build and send responses using packet builder
	// Send online status for each contact that is online.
	// Apply downgradeStatusForV2 so V2 clients see correct icons
	// for statuses they don't natively support (N/A→Away, Occupied→DND, FFC→Online).
	for _, contact := range contactResult.OnlineContacts {
		if contact.Online {
			onlinePkt := h.packetBuilder.BuildUserOnline(
				session.NextServerSeqNum(),
				contact.UIN,
				downgradeStatusForV2(contact.Status),
				nil, // IP not available from service layer
				0,   // Port not available from service layer
			)
			_ = h.sender.SendToSession(session, onlinePkt)
		}
	}

	// 4. Send contact list done using packet builder
	return h.sender.SendToSession(session, h.packetBuilder.BuildContactListDone(session.NextServerSeqNum(), session.UIN))
}

// handleSendMessage processes a message send request
// Refactored to use service layer (ProcessMessage) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
//
// IMPORTANT: The client uses SendExpectEvent() which retransmits until it
// receives SRV_ACK with the matching sequence number. We must send ACK
// to stop the retransmission loop.
func (h *V2Handler) handleSendMessage(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first to stop client retransmission
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// 1. Unmarshal packet to typed struct
	msg, err := ParseV2Message(pkt.Data)
	if err != nil {
		h.logger.Debug("failed to parse message", "err", err)
		return nil
	}

	msg.FromUIN = session.UIN

	h.logger.Debug("message received",
		"from", msg.FromUIN,
		"to", msg.ToUIN,
		"type", msg.MsgType,
	)

	// 2. Call service layer with typed request
	msgReq := MessageRequest{
		FromUIN: msg.FromUIN,
		ToUIN:   msg.ToUIN,
		MsgType: msg.MsgType,
		Message: msg.Message,
	}

	msgResult, err := h.service.ProcessMessage(ctx, session, msgReq)
	if err != nil {
		h.logger.Debug("failed to process message", "err", err)
	} else {
		h.logger.Debug("message processed",
			"from", msg.FromUIN,
			"to", msg.ToUIN,
			"delivered", msgResult.Delivered,
			"stored_offline", msgResult.StoredOffline,
			"target_online", msgResult.TargetOnline,
		)

		// Deliver message to target if online via legacy protocol
		if msgResult.TargetOnline {
			targetSession := h.sessions.GetSession(msg.ToUIN)
			if targetSession != nil {
				if h.dispatcher != nil {
					_ = h.dispatcher.SendOnlineMessage(targetSession, msg.FromUIN, msg.MsgType, msg.Message)
				} else {
					_ = h.sendMessage(targetSession, msg.FromUIN, msg.MsgType, msg.Message)
				}
			}
		}
	}

	return nil
}

// handleSetStatus processes a status change request
// Refactored to use service layer (ProcessStatusChange) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
//
// IMPORTANT: The client uses SendExpectEvent() which retransmits until it
// receives SRV_ACK with the matching sequence number. We must send ACK first.
func (h *V2Handler) handleSetStatus(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first to stop client retransmission
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// 1. Unmarshal packet to typed struct
	if len(pkt.Data) < 4 {
		return nil
	}

	newStatus := binary.LittleEndian.Uint32(pkt.Data[0:4])
	oldStatus := session.GetStatus()

	h.logger.Debug("status change",
		"uin", session.UIN,
		"old_status", fmt.Sprintf("0x%08X", oldStatus),
		"new_status", fmt.Sprintf("0x%08X", newStatus),
	)

	// Update session status (handler responsibility - session management)
	session.SetStatus(newStatus)

	// 2. Call service layer with typed request
	statusReq := StatusChangeRequest{
		UIN:       session.UIN,
		NewStatus: newStatus,
		OldStatus: oldStatus,
	}

	statusResult, err := h.service.ProcessStatusChange(ctx, statusReq)
	if err != nil {
		h.logger.Debug("failed to process status change", "err", err)
	} else {
		h.logger.Debug("status change processed",
			"uin", session.UIN,
			"notify_count", len(statusResult.NotifyTargets),
		)

		// 3. Send status notifications to contacts using dispatcher
		// The service layer returns the list of users to notify.
		// We must go through the dispatcher so each target gets the
		// correct packet format for its protocol version.
		for _, target := range statusResult.NotifyTargets {
			targetSession := h.sessions.GetSession(target.UIN)
			if targetSession != nil {
				if h.dispatcher != nil {
					_ = h.dispatcher.SendStatusChange(targetSession, session.UIN, newStatus)
				} else {
					statusPkt := h.packetBuilder.BuildStatusUpdate(
						targetSession.NextServerSeqNum(),
						session.UIN,
						newStatus,
					)
					_ = h.sender.SendToSession(targetSession, statusPkt)
				}
			}
		}
	}

	return nil
}

// handleInfoReq processes a user info request
// Client sends: SEQ(2) + UIN(4) as data (from center-1.10.7 icq_SendInfoReq)
// Server responds with SRV_INFO_REPLY (0x0118)
//
// IMPORTANT: This is an "extended event" in the client. The client's retry
// thread is cancelled by SRV_ACK, which moves the event to the extended event
// list. Then SRV_INFO_REPLY calls DoneExtendedEvent() to complete it.
// Without the ACK, the client retransmits AND DoneExtendedEvent can't find
// the event (it was never moved from running to extended).
func (h *V2Handler) handleInfoReq(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first - required for extended events
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// Client sends SEQ(2) + UIN(4) = 6 bytes minimum
	if len(pkt.Data) < 6 {
		return nil
	}

	// Skip SEQ prefix (2 bytes), read UIN at offset 2
	infoSeq := binary.LittleEndian.Uint16(pkt.Data[0:2])
	targetUIN := binary.LittleEndian.Uint32(pkt.Data[2:6])

	h.logger.Debug("info request",
		"from", session.UIN,
		"target", targetUIN,
		"info_seq", infoSeq,
	)

	// Get user info
	info, err := h.service.GetUserInfo(ctx, targetUIN)
	if err != nil {
		h.logger.Debug("failed to get user info", "err", err)
		return nil
	}

	// Build and send SRV_INFO_REPLY (0x0118)
	// The checkSequence in the data payload must echo the client's info sub-sequence
	// so DoneExtendedEvent() can match the response to the pending request.
	wireInfo := &LegacyUserInfo{
		UIN:       info.UIN,
		Nickname:  truncateField(info.Nickname, 20, h.logger, "nickname", info.UIN),
		FirstName: truncateField(info.FirstName, 64, h.logger, "first_name", info.UIN),
		LastName:  truncateField(info.LastName, 64, h.logger, "last_name", info.UIN),
		Email:     truncateField(info.Email, 64, h.logger, "email", info.UIN),
		Auth:      info.AuthRequired,
	}
	replyPkt := BuildV2InfoReply(session.NextServerSeqNum(), infoSeq, wireInfo)
	replyPkt.Version = session.Version
	return h.sender.SendToSession(session, MarshalV2ServerPacket(replyPkt))
}

// handleExtInfoReq processes an extended user info request
// Client sends: SEQ(2) + UIN(4) as data (from center-1.10.7 icq_SendExtInfoReq)
// Server responds with SRV_EXT_INFO_REPLY (0x0122)
//
// IMPORTANT: This is an "extended event" in the client - ACK must be sent
// first to move the event from running to extended list, then the data reply
// completes it via DoneExtendedEvent().
func (h *V2Handler) handleExtInfoReq(session *LegacySession, addr *net.UDPAddr, pkt *V2ClientPacket) error {
	ctx := context.Background()

	// Client sends SEQ(2) + UIN(4) = 6 bytes minimum
	if len(pkt.Data) < 6 {
		return nil
	}

	// Skip SEQ prefix (2 bytes), read UIN at offset 2
	seqPrefix := binary.LittleEndian.Uint16(pkt.Data[0:2])
	targetUIN := binary.LittleEndian.Uint32(pkt.Data[2:6])

	h.logger.Debug("ext info request",
		"from", pkt.UIN,
		"target", targetUIN,
		"has_session", session != nil,
	)

	// Send ACK
	if session != nil {
		if err := h.sendAck(session, pkt.SeqNum); err != nil {
			return err
		}
	} else {
		ackPkt := h.packetBuilder.BuildAck(pkt.SeqNum, pkt.Version)
		if err := h.sender.SendPacket(addr, ackPkt); err != nil {
			return err
		}
	}

	// Get full user info for extended fields
	user, err := h.service.GetFullUserInfo(ctx, targetUIN)
	if err != nil {
		h.logger.Debug("failed to get full user info", "err", err)
		return nil
	}

	// Build and send SRV_EXT_INFO_REPLY (0x0122)
	wireInfo := &LegacyUserInfo{
		UIN:      targetUIN,
		City:     truncateField(user.ICQInfo.Basic.City, 64, h.logger, "city", targetUIN),
		State:    truncateField(user.ICQInfo.Basic.State, 64, h.logger, "state", targetUIN),
		Country:  user.ICQInfo.Basic.CountryCode,
		Phone:    truncateField(user.ICQInfo.Basic.CellPhone, 30, h.logger, "phone", targetUIN),
		Homepage: truncateField(user.ICQInfo.More.HomePageAddr, 127, h.logger, "homepage", targetUIN),
		About:    truncateField(user.ICQInfo.Notes.Notes, 450, h.logger, "about", targetUIN),
		Age:      user.Age(time.Now),
		Gender:   uint8(user.ICQInfo.More.Gender),
	}

	if session != nil {
		replyPkt := BuildV2ExtInfoReply(session.NextServerSeqNum(), seqPrefix, wireInfo)
		replyPkt.Version = session.Version
		return h.sender.SendToSession(session, MarshalV2ServerPacket(replyPkt))
	}
	// No session (first-login flow) — use seqPrefix as connection ID and send to addr
	replyPkt := BuildV2ExtInfoReply(seqPrefix, seqPrefix, wireInfo)
	return h.sender.SendPacket(addr, MarshalV2ServerPacket(replyPkt))
}

// handleSearchUIN processes a search by UIN request
// Client sends: SEQ(2) + UIN(4) as data (from center-1.10.7 icq_SendSearchUINReq)
//
// IMPORTANT: This is an "extended event" in the client - ACK must be sent
// first to move the event from running to extended list.
func (h *V2Handler) handleSearchUIN(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first - required for extended events
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// Client sends SEQ(2) + UIN(4) = 6 bytes minimum
	if len(pkt.Data) < 6 {
		return h.sendSearchResult(session, &LegacyUserSearchResult{}, true, 0)
	}

	// Read client sub-sequence (2 bytes) and UIN (4 bytes)
	clientSubSeq := binary.LittleEndian.Uint16(pkt.Data[0:2])
	targetUIN := binary.LittleEndian.Uint32(pkt.Data[2:6])

	h.logger.Debug("search by UIN",
		"from", session.UIN,
		"target", targetUIN,
	)

	// Search for user
	result, err := h.service.SearchByUIN(ctx, targetUIN)
	if err != nil {
		h.logger.Debug("search failed", "err", err)
		// Send empty search result
		return h.sendSearchResult(session, &LegacyUserSearchResult{}, true, clientSubSeq)
	}

	return h.sendSearchResult(session, result, true, clientSubSeq)
}

// handleSearchUser processes a search by name/email request
// Client sends: SEQ(2) + NICK_LEN(2) + NICK + FIRST_LEN(2) + FIRST + LAST_LEN(2) + LAST + EMAIL_LEN(2) + EMAIL
// (from center-1.10.7 icq_SendSearchReq)
//
// IMPORTANT: This is an "extended event" in the client - ACK must be sent
// first to move the event from running to extended list.
func (h *V2Handler) handleSearchUser(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first - required for extended events
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	h.logger.Debug("search by name/email", "from", session.UIN)

	// Need at least SEQ(2) + one length-prefixed string
	if len(pkt.Data) < 4 {
		return h.sendSearchResult(session, &LegacyUserSearchResult{}, true, 0)
	}

	// Read client sub-sequence
	clientSubSeq := binary.LittleEndian.Uint16(pkt.Data[0:2])

	// Skip SEQ prefix (2 bytes)
	r := bytes.NewReader(pkt.Data[2:])

	nick, _ := ParseLegacyString(r, true)
	first, _ := ParseLegacyString(r, true)
	last, _ := ParseLegacyString(r, true)
	email, _ := ParseLegacyString(r, true)

	h.logger.Debug("search params",
		"nick", nick,
		"first", first,
		"last", last,
		"email", email,
	)

	results, err := h.service.SearchByName(ctx, nick, first, last, email)
	if err != nil {
		h.logger.Debug("search failed", "err", err)
		return h.sendSearchResult(session, &LegacyUserSearchResult{}, true, clientSubSeq)
	}

	// Send each result
	for i, result := range results {
		isLast := i == len(results)-1
		r := result // copy for pointer
		if err := h.sendSearchResult(session, &r, isLast, clientSubSeq); err != nil {
			return err
		}
	}

	// If no results, send empty done
	if len(results) == 0 {
		return h.sendSearchResult(session, &LegacyUserSearchResult{}, true, clientSubSeq)
	}

	return nil
}

// handleOfflineMsgReq processes an offline message request
//
// IMPORTANT: The client uses SendExpectEvent() which retransmits until it
// receives SRV_ACK with the matching sequence number. We must send ACK first.
// Then offline messages must use SRV_SYS_MSG_OFFLINE (0x00DC) with timestamp
// fields, NOT SRV_SYS_MSG_ONLINE (0x0104). The client parses the timestamp
// from 0x00DC packets to show when the message was originally sent.
func (h *V2Handler) handleOfflineMsgReq(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first to stop client retransmission
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	h.logger.Debug("offline message request", "uin", session.UIN)

	// Get offline messages
	messages, err := h.service.GetOfflineMessages(ctx, session.UIN)
	if err != nil {
		h.logger.Debug("failed to get offline messages", "err", err)
	}

	// Send each offline message using SRV_SYS_MSG_OFFLINE (0x00DC) with timestamp
	for _, msg := range messages {
		ts := msg.Timestamp
		if ts.IsZero() {
			ts = time.Now()
		}
		offlinePkt := BuildV2OfflineMessage(session.NextServerSeqNum(), msg.FromUIN, msg.MsgType, msg.Message, ts)
		offlinePkt.Version = session.Version
		if err := h.sender.SendToSession(session, MarshalV2ServerPacket(offlinePkt)); err != nil {
			h.logger.Debug("failed to send offline message", "err", err)
		}
	}

	// Send end of offline messages (SRV_SYS_MSG_DONE 0x00E6)
	// V2 format includes UIN(4) — from licq: 02 00 E6 00 04 00 50 A5 82 00
	uinData := make([]byte, 4)
	binary.LittleEndian.PutUint32(uinData[0:4], session.UIN)
	endPkt := &V2ServerPacket{
		Version: session.Version,
		Command: ICQLegacySrvSysMsgDone,
		SeqNum:  session.NextServerSeqNum(),
		Data:    uinData,
	}
	return h.sender.SendToSession(session, MarshalV2ServerPacket(endPkt))
}

// handleOfflineMsgAck processes an offline message acknowledgment
//
// IMPORTANT: The client uses SendExpectEvent() which retransmits until it
// receives SRV_ACK with the matching sequence number. We must send ACK first,
// then do the work (delete offline messages).
func (h *V2Handler) handleOfflineMsgAck(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// Send ACK first to stop client retransmission
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	h.logger.Debug("offline message ack", "uin", session.UIN)

	// Delete offline messages
	if err := h.service.AckOfflineMessages(ctx, session.UIN); err != nil {
		h.logger.Debug("failed to ack offline messages", "err", err)
	}

	return nil
}

// handleVisibleList processes a visible list update
func (h *V2Handler) handleVisibleList(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	contactList, err := ParseV2ContactList(pkt.Data)
	if err != nil {
		h.logger.Debug("failed to parse visible list", "err", err)
		return h.sendAck(session, pkt.SeqNum)
	}

	h.logger.Debug("visible list received",
		"uin", session.UIN,
		"count", len(contactList.UINs),
	)

	session.SetVisibleList(contactList.UINs)
	return h.sendAck(session, pkt.SeqNum)
}

// handleInvisibleList processes an invisible list update
func (h *V2Handler) handleInvisibleList(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	contactList, err := ParseV2ContactList(pkt.Data)
	if err != nil {
		h.logger.Debug("failed to parse invisible list", "err", err)
		return h.sendAck(session, pkt.SeqNum)
	}

	h.logger.Debug("invisible list received",
		"uin", session.UIN,
		"count", len(contactList.UINs),
	)

	session.SetInvisibleList(contactList.UINs)
	return h.sendAck(session, pkt.SeqNum)
}

// handleUserAdd processes a user add request
//
// IMPORTANT: The client uses SendExpectEvent() which retransmits until it
// receives SRV_ACK with the matching sequence number. We must send ACK first,
// then do the work (add to contact list, check online status, send notification).
func (h *V2Handler) handleUserAdd(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	// Send ACK first to stop client retransmission
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	if len(pkt.Data) < 4 {
		return nil
	}

	targetUIN := binary.LittleEndian.Uint32(pkt.Data[0:4])

	h.logger.Debug("user add",
		"from", session.UIN,
		"target", targetUIN,
	)

	// Add to contact list
	contacts := session.GetContactList()
	contacts = append(contacts, targetUIN)
	session.SetContactList(contacts)

	ctx := context.Background()

	// Sync to clientSideBuddyList so OSCAR's BuddyArrived reaches this user
	// for the newly added contact (mirrors ProcessContactList sync logic)
	if _, err := h.service.ProcessUserAdd(ctx, session.Instance, UserAddRequest{
		FromUIN:   session.UIN,
		TargetUIN: targetUIN,
	}); err != nil {
		h.logger.Debug("user add service call failed", "err", err)
	}

	// Check if target is online via legacy session and send notification
	targetSession := h.sessions.GetSession(targetUIN)
	if targetSession != nil {
		if h.dispatcher != nil {
			_ = h.dispatcher.SendUserOnline(session, targetUIN, targetSession.GetStatus())
		} else {
			_ = h.sendUserOnline(session, targetUIN, targetSession.GetStatus(), nil, 0)
		}

		// Also send the adder's online status to the target.
		// The target won't see the adder as online unless we tell them.
		if h.dispatcher != nil {
			_ = h.dispatcher.SendUserOnline(targetSession, session.UIN, session.GetStatus())
		} else {
			_ = h.sendUserOnline(targetSession, session.UIN, session.GetStatus(), nil, 0)
		}
	} else {
		// Check if target is online via OSCAR session
		info, err := h.service.GetUserInfoForProtocol(ctx, targetUIN)
		if err == nil && info != nil && info.Online {
			status := downgradeStatusForV2(info.Status)
			_ = h.sendUserOnline(session, targetUIN, status, nil, 0)
		}
	}

	return nil
}

// handleFirstLogin processes the initial login setup packet (0x04EC)
// This is sent before the actual login to set up the connection.
// From iserverd v3_process_firstlog(): just send ACK, nothing else.
// The client then proceeds with getdeps (0x03F2).
func (h *V2Handler) handleFirstLogin(session *LegacySession, addr *net.UDPAddr, pkt *V2ClientPacket) error {
	h.logger.Debug("first login packet received",
		"uin", pkt.UIN,
		"addr", addr.String(),
	)

	// Send V2-format ACK only. Do NOT send cmd 370 (server info reply).
	// The client's connection list is preserved, allowing the subsequent
	// cmd 1010 ACK to trigger message 0x455 via sub_430097, which advances
	// the wizard to the next step.
	ackPkt := &V2ServerPacket{
		Version: pkt.Version,
		Command: ICQLegacySrvAck,
		SeqNum:  pkt.SeqNum,
	}
	return h.sender.SendPacket(addr, MarshalV2ServerPacket(ackPkt))
}

// handleGetDeps processes the pre-auth pseudo-login packet (0x03F2).
// Historically called "get departments list" in iserverd (from its Users_Deps database table).
// The server validates credentials, sends V3-format ACK, then sends the pre-auth response (0x0032).
// The client then proceeds with the actual login (0x03E8).
//
// IMPORTANT: Even though the client sends version=2 in the header, this packet
// uses V3 packet structure (12-byte header with seq1, seq2, UIN). The response
// packets (ACK and depslist) MUST also be V3 format, matching iserverd behavior.
// iserverd's v3_send_ack and v3_send_depslist always use V3_PROTO (0x0003) in
// the response regardless of the client's declared version.
//
// Raw packet layout (V3 header):
//
//	VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + DATA...
//
// Data layout:
//
//	PWD_LEN(2) + PASSWORD(pwdLen) + STATUS(4)
func (h *V2Handler) handleGetDeps(addr *net.UDPAddr, packet []byte) error {
	ctx := context.Background()

	if len(packet) < 14 { // 12-byte V3 header + at least 2 bytes for pwd_len
		h.logger.Debug("getdeps packet too short", "len", len(packet))
		return nil
	}

	// Parse as V3 header (12 bytes)
	seq1 := binary.LittleEndian.Uint16(packet[4:6])
	seq2 := binary.LittleEndian.Uint16(packet[6:8])
	uin := binary.LittleEndian.Uint32(packet[8:12])
	data := packet[12:]

	h.logger.Debug("getdeps packet (0x03F2)",
		"addr", addr.String(),
		"seq1", seq1,
		"seq2", seq2,
		"uin", uin,
		"data_len", len(data),
		"data_hex", fmt.Sprintf("%X", data),
	)

	// Parse password from data
	offset := 0
	if len(data) < 2 {
		return nil
	}
	pwdLen := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2

	if pwdLen == 0 || pwdLen > 20 || offset+int(pwdLen) > len(data) {
		h.logger.Debug("invalid password in getdeps", "pwd_len", pwdLen)
		return h.sendBadPassword(addr, seq1, 2)
	}

	password := string(data[offset : offset+int(pwdLen)])
	if len(password) > 0 && password[len(password)-1] == 0 {
		password = password[:len(password)-1]
	}

	h.logger.Info("getdeps (pseudo-login)",
		"uin", uin,
		"password_len", len(password),
	)

	// Validate credentials using service layer
	authReq := AuthRequest{
		UIN:      uin,
		Password: password,
		Version:  ICQLegacyVersionV2,
	}

	loginOK, err := h.service.ValidateCredentials(ctx, authReq.UIN, authReq.Password)
	if err != nil || !loginOK {
		h.logger.Info("getdeps failed - invalid credentials", "uin", uin)
		return h.sendBadPassword(addr, seq1, 2)
	}

	h.logger.Debug("credentials validated successfully", "uin", uin)

	// Send V2-format ACK for cmd 1010.
	ackPkt := h.packetBuilder.BuildAck(seq1, ICQLegacyVersionV2)
	if err := h.sender.SendPacket(addr, ackPkt); err != nil {
		return err
	}

	// Send V2-format DeptsList (cmd 0x0032 = 50).
	// From disassembly: the client's cmd 50 handler reads:
	//   connection_id (word) + UIN (dword)
	// The connection_id must match the one used by cmd 1010 (= seq2).
	// The UIN must match g_saved_uin + 0x9C.
	depsData := make([]byte, 6)
	binary.LittleEndian.PutUint16(depsData[0:2], seq2) // connection ID
	binary.LittleEndian.PutUint32(depsData[2:6], uin)  // UIN
	depsPkt := &V2ServerPacket{
		Version: ICQLegacyVersionV2,
		Command: ICQLegacySrvUserDepsList, // 0x0032
		SeqNum:  seq1,
		Data:    depsData,
	}
	return h.sender.SendPacket(addr, MarshalV2ServerPacket(depsPkt))
}

// handleAuthorize processes CMD_AUTHORIZE (0x0456) which is a thru-server
// message in V2. The packet format is identical to CMD_THRUxSERVER (0x010E):
// TO_UIN(4) + MSG_TYPE(2) + MSG_LEN(2) + MESSAGE
// iserverd routes both 0x010E and 0x0456 through the same v3_process_sysmsg.
func (h *V2Handler) handleAuthorize(session *LegacySession, pkt *V2ClientPacket) error {
	return h.handleSendMessage(session, pkt)
}

// handleUpdateBasic processes a basic profile update (CMD_UPDATExBASIC 0x04A6)
// Client sends: SEQ(2) + ALIAS_LEN(2) + ALIAS + FIRST_LEN(2) + FIRST +
//
//	LAST_LEN(2) + LAST + EMAIL_LEN(2) + EMAIL + AUTH(1)
//
// Server responds with SRV_UPDATEDxBASIC (0x00B4) containing SEQ(2) on success,
// or SRV_UPDATExBASICxFAIL (0x00BE) on failure.
//
// IMPORTANT: This is an "extended event" - ACK moves it from running to
// extended list, then the response completes it via DoneExtendedEvent().
func (h *V2Handler) handleUpdateBasic(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	// Send ACK first - required for extended events
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// Need at least SEQ(2) + one length-prefixed string
	if len(pkt.Data) < 4 {
		return h.sendUpdateBasicFail(session, 0)
	}

	// Read the update sequence (2 bytes)
	updateSeq := binary.LittleEndian.Uint16(pkt.Data[0:2])
	r := bytes.NewReader(pkt.Data[2:])

	alias, _ := ParseLegacyString(r, true)
	firstName, _ := ParseLegacyString(r, true)
	lastName, _ := ParseLegacyString(r, true)
	email, _ := ParseLegacyString(r, true)

	var auth uint8
	hasAuth := binary.Read(r, binary.LittleEndian, &auth) == nil && r.Len() >= 0

	h.logger.Debug("update basic info",
		"uin", session.UIN,
		"alias", alias,
		"first", firstName,
		"last", lastName,
		"email", email,
		"auth", auth,
		"has_auth", hasAuth,
	)

	// Persist basic info via service layer using read-merge-write
	// to avoid overwriting fields not present in the V2 packet
	// (city, state, country, phone, etc.)
	ctx := context.Background()
	existing, err := h.service.GetFullUserInfo(ctx, session.UIN)
	var info state.ICQBasicInfo
	if err == nil && existing != nil {
		info = existing.ICQInfo.Basic
	}
	info.Nickname = alias
	info.FirstName = firstName
	info.LastName = lastName
	info.EmailAddress = email
	if err := h.service.UpdateBasicInfo(ctx, session.UIN, info); err != nil {
		h.logger.Error("V2 update basic info failed", "uin", session.UIN, "err", err)
	}

	// Update auth mode only if the auth byte was present in the packet.
	// V2 format (0x04A6) includes AUTH(1), V4 format (0x050A) does not.
	if hasAuth && pkt.Command == ICQLegacyCmdUpdateBasic {
		if err := h.service.SetAuthMode(ctx, session.UIN, auth == 1); err != nil {
			h.logger.Error("V2 set auth mode failed", "uin", session.UIN, "err", err)
		}
	}

	// Send SRV_UPDATEDxBASIC — V2 uses 0x00B4, V4 uses 0x01E0
	replyCmd := ICQLegacySrvUpdatedBasic // 0x00B4
	if pkt.Command == ICQLegacyCmdSetBasicInfo {
		replyCmd = ICQLegacySrvUpdatedBasicV4 // 0x01E0
	}
	data := make([]byte, 2)
	binary.LittleEndian.PutUint16(data[0:2], updateSeq)
	replyPkt := &V2ServerPacket{
		Version: session.Version,
		Command: replyCmd,
		SeqNum:  session.NextServerSeqNum(),
		Data:    data,
	}
	return h.sender.SendToSession(session, MarshalV2ServerPacket(replyPkt))
}

// sendUpdateBasicFail sends SRV_UPDATExBASICxFAIL (0x00BE)
func (h *V2Handler) sendUpdateBasicFail(session *LegacySession, updateSeq uint16) error {
	data := make([]byte, 2)
	binary.LittleEndian.PutUint16(data[0:2], updateSeq)
	pkt := &V2ServerPacket{
		Version: session.Version,
		Command: ICQLegacySrvUpdateBasicFail,
		SeqNum:  session.NextServerSeqNum(),
		Data:    data,
	}
	return h.sender.SendToSession(session, MarshalV2ServerPacket(pkt))
}

// handleUpdateDetail processes an extended profile update (CMD_UPDATExDETAIL 0x04B0)
// Client sends: SEQ(2) + CITY_LEN(2) + CITY + COUNTRY(2) + COUNTRY_STAT(1) +
//
//	STATE_LEN(2) + STATE + AGE(2) + SEX(1) + PHONE_LEN(2) + PHONE +
//	HP_LEN(2) + HP + ABOUT_LEN(2) + ABOUT
//
// Server responds with SRV_UPDATEDxDETAIL (0x00C8) containing SEQ(2) on success,
// or SRV_UPDATExDETAILxFAIL (0x00D2) on failure.
//
// IMPORTANT: This is an "extended event" - ACK moves it from running to
// extended list, then the response completes it via DoneExtendedEvent().
func (h *V2Handler) handleUpdateDetail(session *LegacySession, pkt *V2ClientPacket) error {
	if session == nil {
		return nil
	}

	// Send ACK first - required for extended events
	if err := h.sendAck(session, pkt.SeqNum); err != nil {
		return err
	}

	// Need at least SEQ(2) + one length-prefixed string
	if len(pkt.Data) < 4 {
		return h.sendUpdateDetailFail(session, 0)
	}

	// Read the update sequence (2 bytes)
	updateSeq := binary.LittleEndian.Uint16(pkt.Data[0:2])
	r := bytes.NewReader(pkt.Data[2:])

	city, _ := ParseLegacyString(r, true)
	var country uint16
	_ = binary.Read(r, binary.LittleEndian, &country)
	var countryStat uint8
	_ = binary.Read(r, binary.LittleEndian, &countryStat)
	st, _ := ParseLegacyString(r, true)
	var age uint16
	_ = binary.Read(r, binary.LittleEndian, &age)
	var sex uint8
	_ = binary.Read(r, binary.LittleEndian, &sex)
	phone, _ := ParseLegacyString(r, true)
	homepage, _ := ParseLegacyString(r, true)
	about, _ := ParseLegacyString(r, true)

	h.logger.Debug("update detail info",
		"uin", session.UIN,
		"city", city,
		"country", country,
		"state", st,
		"age", age,
		"sex", sex,
		"phone", phone,
		"homepage", homepage,
		"about", about,
	)

	// Persist detail info via service layer
	// Read existing basic info to avoid overwriting nick/first/last/email
	ctx := context.Background()
	existing, err := h.service.GetFullUserInfo(ctx, session.UIN)
	if err == nil && existing != nil {
		existing.ICQInfo.Basic.City = city
		existing.ICQInfo.Basic.CountryCode = country
		existing.ICQInfo.Basic.State = st
		existing.ICQInfo.Basic.Phone = phone
		if err := h.service.UpdateBasicInfo(ctx, session.UIN, existing.ICQInfo.Basic); err != nil {
			h.logger.Error("V2 update detail basic failed", "uin", session.UIN, "err", err)
		}
	}

	// Read existing more info to avoid overwriting birthday/languages
	if existing != nil {
		existing.ICQInfo.More.Gender = uint16(sex)
		existing.ICQInfo.More.HomePageAddr = homepage
		if err := h.service.UpdateMoreInfo(ctx, session.UIN, existing.ICQInfo.More); err != nil {
			h.logger.Error("V2 update detail more failed", "uin", session.UIN, "err", err)
		}
	}

	if about != "" {
		if err := h.service.SetNotes(ctx, session.UIN, about); err != nil {
			h.logger.Error("V2 update detail about failed", "uin", session.UIN, "err", err)
		}
	}

	// Send SRV_UPDATEDxDETAIL (0x00C8) with the update sequence
	data := make([]byte, 2)
	binary.LittleEndian.PutUint16(data[0:2], updateSeq)
	replyPkt := &V2ServerPacket{
		Version: session.Version,
		Command: ICQLegacySrvUpdatedDetail,
		SeqNum:  session.NextServerSeqNum(),
		Data:    data,
	}
	return h.sender.SendToSession(session, MarshalV2ServerPacket(replyPkt))
}

// sendUpdateDetailFail sends SRV_UPDATExDETAILxFAIL (0x00D2)
func (h *V2Handler) sendUpdateDetailFail(session *LegacySession, updateSeq uint16) error {
	data := make([]byte, 2)
	binary.LittleEndian.PutUint16(data[0:2], updateSeq)
	pkt := &V2ServerPacket{
		Version: session.Version,
		Command: ICQLegacySrvUpdateDetailFail,
		SeqNum:  session.NextServerSeqNum(),
		Data:    data,
	}
	return h.sender.SendToSession(session, MarshalV2ServerPacket(pkt))
}

// handleRegNewUser processes a CMD_REG_NEW_USER (0x03FC) registration packet.
// This uses the srv_net_icq_pak format (6-byte header, no UIN).
// Data format from center icq_RegNewUser():
//
//	CONST(2) + PWD_LEN(2) + PASSWORD(variable, null-terminated) + TRAILING(8)
//
// Server responds with SRV_NEW_UIN (0x0046) containing the new UIN.
func (h *V2Handler) handleRegNewUser(addr *net.UDPAddr, pkt *V2ClientPacket) error {
	ctx := context.Background()

	h.logger.Debug("registration packet (0x03FC)",
		"addr", addr.String(),
		"data_len", len(pkt.Data),
		"data_hex", fmt.Sprintf("%X", pkt.Data),
	)

	// Need at least: CONST(2) + PWD_LEN(2) + 1 byte password + null
	if len(pkt.Data) < 6 {
		h.logger.Debug("registration packet too short")
		return nil
	}

	offset := 2 // skip 2-byte constant

	// Read password length (2 bytes)
	pwdLen := binary.LittleEndian.Uint16(pkt.Data[offset : offset+2])
	offset += 2

	if pwdLen == 0 || len(pkt.Data) < offset+int(pwdLen) {
		h.logger.Debug("invalid password length in registration", "pwd_len", pwdLen)
		return nil
	}

	// Read password, strip null terminator
	password := string(pkt.Data[offset : offset+int(pwdLen)])
	if len(password) > 0 && password[len(password)-1] == 0 {
		password = password[:len(password)-1]
	}

	h.logger.Info("registration attempt",
		"addr", addr.String(),
		"password_len", len(password),
	)

	// Call service layer to create the new user
	newUIN, err := h.service.RegisterNewUser(ctx, "", "", "", "", password)
	if err != nil {
		h.logger.Error("registration failed", "err", err)
		return nil
	}

	h.logger.Info("registration successful",
		"new_uin", newUIN,
		"addr", addr.String(),
	)

	// Send SRV_NEW_UIN (0x0046) response
	replyPkt := BuildV2NewUIN(pkt.SeqNum, newUIN)
	replyBytes := MarshalV2ServerPacket(replyPkt)
	h.logger.Debug("sending SRV_NEW_UIN",
		"new_uin", newUIN,
		"seq", pkt.SeqNum,
		"raw_hex", fmt.Sprintf("%X", replyBytes),
	)
	return h.sender.SendPacket(addr, replyBytes)
}