package icq_legacy

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

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

// V3Handler handles ICQ V3 protocol packets
// V3 packet format (from iserverd source):
// VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + DATA...
// Total header: 12 bytes (NO checksum in V3, unlike V5!)
type V3Handler struct {
	sessions      *LegacySessionManager
	service       LegacyService
	sender        PacketSender
	packetBuilder V3PacketBuilder   // Packet builder for constructing V3 protocol packets
	dispatcher    MessageDispatcher // Central dispatcher for cross-protocol messaging
	logger        *slog.Logger
}

// NewV3Handler creates a new V3 protocol handler
func NewV3Handler(
	sessions *LegacySessionManager,
	service LegacyService,
	sender PacketSender,
	packetBuilder V3PacketBuilder,
	logger *slog.Logger,
) *V3Handler {
	return &V3Handler{
		sessions:      sessions,
		service:       service,
		sender:        sender,
		packetBuilder: packetBuilder,
		dispatcher:    nil, // Set later via SetDispatcher to avoid circular dependency
		logger:        logger,
	}
}

// SetSender sets the packet sender (for circular dependency resolution)
func (h *V3Handler) SetSender(sender PacketSender) {
	h.sender = sender
}

// SetDispatcher sets the message dispatcher for cross-protocol messaging
func (h *V3Handler) SetDispatcher(dispatcher MessageDispatcher) {
	h.dispatcher = dispatcher
}

// Handle processes a V3 protocol packet
func (h *V3Handler) Handle(session *LegacySession, addr *net.UDPAddr, packet []byte) error {
	// V3 packet format (from iserverd source):
	// VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + DATA...
	// Total header: 12 bytes (NO checksum in V3!)

	h.logger.Debug("raw V3 packet",
		"hex", fmt.Sprintf("%X", packet),
		"len", len(packet),
	)

	if len(packet) < 12 {
		return fmt.Errorf("V3 packet too short: %d bytes", len(packet))
	}

	// Parse V3 header directly (iserverd: pack >> vvers >> pcomm >> seq1 >> seq2 >> uin_num)
	version := binary.LittleEndian.Uint16(packet[0:2])
	command := binary.LittleEndian.Uint16(packet[2:4])
	seq1 := binary.LittleEndian.Uint16(packet[4:6])
	seq2 := binary.LittleEndian.Uint16(packet[6:8])
	uin := binary.LittleEndian.Uint32(packet[8:12])

	// Extract data after header
	var data []byte
	if len(packet) > 12 {
		data = packet[12:]
	}

	h.logger.Debug("V3 packet parsed",
		"version", version,
		"command", fmt.Sprintf("0x%04X", command),
		"seq1", seq1,
		"seq2", seq2,
		"uin", uin,
		"data_len", len(data),
	)

	// Update session activity if we have one
	if session != nil {
		session.UpdateActivity()
		session.SeqNumClient = seq1
	}

	// 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 command {
		case ICQLegacyCmdAck, ICQLegacyCmdFirstLogin,
			ICQLegacyCmdGetDeps, ICQLegacyCmdLogin:
			// Allow these through - they don't require a session
		default:
			h.logger.Info("V3 packet from unknown session, sending NOT_CONNECTED",
				"command", fmt.Sprintf("0x%04X", command),
				"uin", uin,
				"addr", addr.String(),
			)
			return h.sendNotConnected(addr, seq2, uin)
		}
	}

	// Handle V3 commands directly (matching iserverd's handle_v3_proto)
	switch command {
	case ICQLegacyCmdFirstLogin:
		return h.handleFirstLogin(addr, seq1, seq2, uin)
	case ICQLegacyCmdLogin:
		return h.handleLogin(session, addr, seq1, seq2, uin, data)
	case ICQLegacyCmdGetDeps:
		return h.handleGetDeps(addr, seq1, seq2, data)
	case ICQLegacyCmdUserGetInfo:
		return h.handleGetInfo(session, seq1, seq2, uin, data)
	case ICQLegacyCmdAck:
		h.logger.Debug("received ACK", "seq1", seq1, "seq2", seq2)
		return nil
	case ICQLegacyCmdKeepAlive, ICQLegacyCmdKeepAlive2:
		return h.handlePing(session, addr, seq1, seq2, uin)
	case ICQLegacyCmdLogoff:
		return h.handleLogoff(session, seq1, seq2, uin)
	case ICQLegacyCmdContactList:
		return h.handleContactList(session, seq1, seq2, uin, data)
	case ICQLegacyCmdSetStatus:
		return h.handleSetStatus(session, seq1, seq2, uin, data)
	case ICQLegacyCmdThruServer, ICQLegacyCmdAuthorize: // 0x010E and 0x0456 (authorize)
		return h.handleMessage(session, seq1, seq2, uin, data)
	case ICQLegacyCmdUserAdd:
		return h.handleUserAdd(session, seq1, seq2, uin, data)
	case ICQLegacyCmdSysMsgReq:
		return h.handleOfflineMsgReq(session, seq1, seq2, uin)
	case ICQLegacyCmdSetBasicInfo:
		return h.handleSetBasicInfo(session, seq1, seq2, uin, data)
	case 0x0582: // SetHomeInfo
		return h.handleSetHomeInfo(session, seq1, seq2, uin, data)
	case 0x058C: // SetHomeWeb
		return h.handleSetHomeWeb(session, seq1, seq2, uin, data)
	case 0x0578: // SetWorkInfo
		return h.handleSetWorkInfo(session, seq1, seq2, uin, data)
	case 0x05BE: // SetWorkWeb
		return h.handleSetWorkWeb(session, seq1, seq2, uin, data)
	case 0x0604: // ICQ_CMDxRCV_UKNOWN_DEP - unknown deps request (historical iserverd naming)
		return h.handleUnknownDep(session, seq1, seq2, uin, data)
	case 0x06AE: // ICQ_CMDxRCV_VISxLIST - visible list
		return h.handleVisibleList(session, seq1, seq2, uin, data)
	case 0x06A4: // ICQ_CMDxRCV_INVISxLIST - invisible list
		return h.handleInvisibleList(session, seq1, seq2, uin, data)
	case ICQLegacyCmdSearchStart: // 0x05C8 - Search user
		return h.handleSearchStart(session, seq1, seq2, uin, data)
	case ICQLegacyCmdGetDeps1: // 0x05F0 - Get deps list during session (pre-auth list, historical iserverd naming)
		return h.handleGetDeps1(session, seq1, seq2, uin, data)
	case 0x05AA: // ICQ_CMDxRCV_GETxNOTES - Get notes
		return h.handleGetNotes(session, seq1, seq2, uin, data)
	case 0x0596: // ICQ_CMDxRCV_SETxNOTES - Set notes
		return h.handleSetNotes(session, seq1, seq2, uin, data)
	case ICQLegacyCmdSetPassword: // 0x049C - Set password
		return h.handleSetPassword(session, seq1, seq2, uin, data)
	case ICQLegacyCmdSetAuth: // 0x0514 - Set auth mode
		return h.handleSetAuth(session, seq1, seq2, uin, data)
	case 0x0528: // ICQ_CMDxRCV_SETxSTATE - Set client state (not search!)
		return h.handleSetState(session, seq1, seq2, uin, data)
	case 0x0532: // ICQ_CMDxRCV_USAGExSTATS - Usage statistics
		return h.handleUsageStats(session, seq1, seq2, uin, data)
	case ICQLegacyCmdGetExternals: // 0x04C4 - Get externals
		return h.handleGetExternals(session, seq1, seq2, uin, data)
	case 0x0442: // ICQ_CMDxRCV_SYSxMSGxDONExACK - System message ack
		return h.handleSysAck(session, seq1, seq2, uin, data)
	case ICQLegacyCmdReconnect: // 0x015E - Reconnect/online info
		return h.handleOnlineInfo(session, seq1, seq2, uin, data)
	case 0x0460: // ICQ_CMDxRCV_USERxGETINFO1 - Get basic info only
		return h.handleGetInfo1(session, seq1, seq2, uin, data)
	default:
		h.logger.Debug("unhandled V3 command",
			"command", fmt.Sprintf("0x%04X", command),
			"uin", uin,
		)
		// Send ACK for unknown commands
		return h.sendAck(addr, seq1, seq2, uin)
	}
}

// handleFirstLogin processes the first login packet (0x04EC)
// From iserverd: v3_process_firstlog() - just sends ACK
func (h *V3Handler) handleFirstLogin(addr *net.UDPAddr, seq1, seq2 uint16, uin uint32) error {
	h.logger.Debug("first login packet",
		"uin", uin,
		"addr", addr.String(),
	)
	return h.sendAck(addr, seq1, seq2, uin)
}

// handleGetDeps processes the pre-auth pseudo-login packet (0x03F2).
// Historically called "get departments list" in iserverd (from its Users_Deps database table).
// Data format: JUNK(4) + UIN(4) + PWD_LEN(2) + PASSWORD
// The server validates credentials and sends the pre-auth response before actual login.
//
// Refactored to use service layer (AuthenticateUser) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
func (h *V3Handler) handleGetDeps(addr *net.UDPAddr, seq1, seq2 uint16, data []byte) error {
	ctx := context.Background()

	// 1. Unmarshal packet to typed struct
	if len(data) < 10 {
		h.logger.Debug("getdeps packet too short", "len", len(data))
		return nil
	}

	offset := 0

	// Skip junk (4 bytes)
	offset += 4

	// Read UIN (4 bytes)
	uin := binary.LittleEndian.Uint32(data[offset : offset+4])
	offset += 4

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

	if pwdLen > 20 {
		pwdLen = 20
	}

	// Read password
	if offset+int(pwdLen) > len(data) {
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}
	password := string(data[offset : offset+int(pwdLen)])
	if len(password) > 0 && password[len(password)-1] == 0 {
		password = password[:len(password)-1]
	}

	h.logger.Info("V3 getdeps (pseudo-login)",
		"uin", uin,
		"password_len", len(password),
	)

	// 2. Call service layer with typed request
	authReq := AuthRequest{
		UIN:      uin,
		Password: password,
		Version:  ICQLegacyVersionV3,
	}

	loginOK, err := h.service.ValidateCredentials(ctx, authReq.UIN, authReq.Password)
	if err != nil {
		h.logger.Error("getdeps authentication error", "err", err, "uin", uin)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}

	if !loginOK {
		h.logger.Info("getdeps failed - invalid credentials", "uin", uin)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}

	// 3. Build and send responses using packet builder
	// Send ACK
	_ = h.sender.SendPacket(addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// Send pre-auth response using packet builder
	return h.sender.SendPacket(addr, h.packetBuilder.BuildDeptsList(seq2, uin))
}

// handleLogin processes login packet (0x03E8)
// From iserverd v3_process_login():
// After header (12 bytes): TIMESTAMP(4) + TCP_PORT(4) + PWD_LEN(2) + PASSWORD + ...
//
// Refactored to use service layer (AuthenticateUser) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
func (h *V3Handler) handleLogin(session *LegacySession, addr *net.UDPAddr, seq1, seq2 uint16, uin uint32, data []byte) error {
	ctx := context.Background()

	// First send ACK (iserverd does this immediately)
	_ = h.sender.SendPacket(addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 1. Unmarshal packet to typed struct
	// V3 login data format (from iserverd):
	// TIMESTAMP(4) + TCP_PORT(4) + PWD_LEN(2) + PASSWORD(pwdLen) + ...
	if len(data) < 10 {
		h.logger.Debug("login packet too short", "len", len(data))
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}

	offset := 0

	// Read timestamp (4 bytes) - skip it
	// timestamp := binary.LittleEndian.Uint32(data[offset : offset+4])
	offset += 4

	// Read TCP port (4 bytes)
	port := binary.LittleEndian.Uint32(data[offset : offset+4])
	offset += 4

	// Read password length (2 bytes)
	if offset+2 > len(data) {
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}
	pwdLen := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2

	// Sanity check password length
	if pwdLen > 20 {
		pwdLen = 20
	}

	// Read password
	if offset+int(pwdLen) > len(data) {
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}
	password := string(data[offset : offset+int(pwdLen)])
	// Remove null terminator if present
	if len(password) > 0 && password[len(password)-1] == 0 {
		password = password[:len(password)-1]
	}

	h.logger.Info("V3 login attempt",
		"uin", uin,
		"port", port,
		"password_len", len(password),
	)

	// 2. Call service layer with typed request
	authReq := AuthRequest{
		UIN:      uin,
		Password: password,
		Status:   ICQLegacyStatusOnline, // Default status for V3
		TCPPort:  port,
		Version:  ICQLegacyVersionV3,
	}

	authResult, err := h.service.AuthenticateUser(ctx, authReq)
	if err != nil {
		h.logger.Error("login authentication error", "err", err, "uin", uin)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}

	if !authResult.Success {
		h.logger.Info("login failed - invalid credentials",
			"uin", uin,
			"error_code", authResult.ErrorCode,
		)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}

	// 3. Create session (handler responsibility - session management)
	// TODO: parse and store direct connection info (IP, port, DC version, DC type)
	// from the V3 login packet so that presence notifications can include real
	// connection details when ICQ_LEGACY_DIRECT_CONNECTIONS includes V3.
	newSession, err := h.sessions.CreateSession(uin, addr, ICQLegacyVersionV3, authResult.oscarSession)
	if err != nil {
		h.logger.Error("failed to create session", "err", err, "uin", uin)
		return h.sender.SendPacket(addr, h.packetBuilder.BuildBadPassword(seq1, seq2, uin))
	}

	newSession.Password = password

	// 4. Build and send response using packet builder
	loginReplyPkt := h.packetBuilder.BuildLoginReply(newSession, seq1, seq2)
	if err := h.sender.SendToSession(newSession, loginReplyPkt); err != nil {
		return err
	}

	h.logger.Info("V3 login successful",
		"uin", uin,
		"session_id", newSession.SessionID,
	)

	if err := h.service.NotifyUserOnline(ctx, newSession.UIN, newSession.GetStatus()); err != nil {
		h.logger.Debug("V3 failed to notify OSCAR clients of online", "uin", newSession.UIN, "err", err)
	}

	return nil
}

// handlePing processes keep-alive packets
func (h *V3Handler) handlePing(session *LegacySession, addr *net.UDPAddr, seq1, seq2 uint16, uin uint32) error {
	if session == nil {
		return h.sendNotConnected(addr, seq2, uin)
	}
	return h.sendAck(addr, seq1, seq2, uin)
}

// handleLogoff processes logout
func (h *V3Handler) handleLogoff(session *LegacySession, seq1, seq2 uint16, uin uint32) error {
	if session == nil {
		return nil
	}
	h.logger.Info("V3 logout", "uin", uin)

	// Notify contacts that this user is going offline BEFORE removing session
	h.notifyContactsUserOffline(session)

	// Notify OSCAR clients that this user went offline
	ctx := context.Background()
	if err := h.service.NotifyUserOffline(ctx, uin); err != nil {
		h.logger.Debug("V3 failed to notify OSCAR clients of offline", "uin", uin, "err", err)
	}

	h.sessions.RemoveSession(uin)
	return nil
}

// notifyContactsUserOffline notifies all contacts who have this user in their list that we're offline
func (h *V3Handler) notifyContactsUserOffline(session *LegacySession) {
	if h.dispatcher == nil {
		return
	}

	// Find all sessions that have this user in their contact list
	contactsToNotify := h.sessions.NotifyContactsOfStatus(session)

	h.logger.Debug("notifying contacts of user offline",
		"uin", session.UIN,
		"contacts_to_notify", contactsToNotify,
	)

	for _, contactUIN := range contactsToNotify {
		contactSession := h.sessions.GetSession(contactUIN)
		if contactSession != nil {
			// Use dispatcher to send offline notification in correct protocol format
			_ = h.dispatcher.SendUserOffline(contactSession, session.UIN)
		}
	}
}

// handleContactList processes contact list (0x0406)
// From iserverd v3_process_contact_list(): processes contact list and sends online notifications
//
// Refactored to use service layer (ProcessContactList) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> send notifications
func (h *V3Handler) handleContactList(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	// 1. Send ACK using packet builder
	_ = h.sender.SendPacket(session.Addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 2. Unmarshal packet to typed request struct
	req, err := h.parseContactListPacket(data, uin)
	if err != nil {
		h.logger.Debug("V3 contact list parse error", "uin", uin, "err", err)
		// Send contact list done even on parse error
		return h.sender.SendToSession(session, h.packetBuilder.BuildContactListDone(session.NextServerSeqNum(), seq2, session.UIN))
	}

	h.logger.Debug("V3 contact list",
		"uin", uin,
		"count", len(req.Contacts),
	)

	// Store contact list in session (handler responsibility - session management)
	session.SetContactList(req.Contacts)

	// 3. Call service layer with typed request
	ctx := context.Background()
	result, err := h.service.ProcessContactList(ctx, session.Instance, req)
	if err != nil {
		h.logger.Error("contact list processing failed", "uin", uin, "err", err)
		// Still send contact list done on error
		return h.sender.SendToSession(session, h.packetBuilder.BuildContactListDone(session.NextServerSeqNum(), seq2, session.UIN))
	}

	// 4. Send online notifications based on service result
	for _, contact := range result.OnlineContacts {
		if contact.Online {
			if h.dispatcher != nil {
				// Use central dispatcher - routes to correct protocol based on session's version
				_ = h.dispatcher.SendUserOnline(session, contact.UIN, contact.Status)
			} else {
				// Fallback to V3 format if dispatcher not set
				_ = h.sendUserOnline(session, contact.UIN, contact.Status)
			}
		}
	}

	h.notifyContactsUserOnline(session)

	// 5. Send contact list done using packet builder
	return h.sender.SendToSession(session, h.packetBuilder.BuildContactListDone(session.NextServerSeqNum(), seq2, session.UIN))
}

// parseContactListPacket parses a V3 contact list packet into a typed ContactListRequest struct.
// Format: TIMESTAMP(4) + COUNT(1) + UIN(4)*COUNT
func (h *V3Handler) parseContactListPacket(data []byte, ownerUIN uint32) (ContactListRequest, error) {
	req := ContactListRequest{
		UIN:      ownerUIN,
		Contacts: make([]uint32, 0),
	}

	if len(data) < 5 {
		return req, fmt.Errorf("contact list packet too short: %d bytes", len(data))
	}

	// Skip timestamp (4 bytes)
	offset := 4

	// Contact count (1 byte)
	count := int(data[offset])
	offset++

	// Parse contact UINs
	for i := 0; i < count && offset+4 <= len(data); i++ {
		contactUIN := binary.LittleEndian.Uint32(data[offset : offset+4])
		req.Contacts = append(req.Contacts, contactUIN)
		offset += 4
	}

	return req, nil
}

// notifyContactsUserOnline notifies all contacts who have this user in their list that we're online
// Following iserverd's pattern: when user comes online, notify everyone who cares
func (h *V3Handler) notifyContactsUserOnline(session *LegacySession) {
	if h.dispatcher == nil {
		return
	}

	// Find all sessions that have this user in their contact list
	contactsToNotify := h.sessions.NotifyContactsOfStatus(session)

	h.logger.Debug("notifying contacts of user online",
		"uin", session.UIN,
		"contacts_to_notify", contactsToNotify,
	)

	for _, contactUIN := range contactsToNotify {
		contactSession := h.sessions.GetSession(contactUIN)
		if contactSession != nil {
			// Use dispatcher to send in correct protocol format for each contact
			_ = h.dispatcher.SendUserOnline(contactSession, session.UIN, session.GetStatus())
		}
	}
}

// handleSetStatus processes status change (0x04D8)
// From iserverd v3_process_status(): when a user changes their status
// (e.g., Online -> Away, Away -> DND), this handler updates the session
// and notifies all contacts who have this user in their contact list.
//
// Refactored to use service layer (ProcessStatusChange) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> broadcast
func (h *V3Handler) handleSetStatus(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	ctx := context.Background()

	// 1. Send ACK using packet builder
	_ = h.sender.SendPacket(session.Addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 2. Unmarshal packet to typed request struct
	// Parse status - format: TIMESTAMP(4) + STATUS(4)
	if len(data) < 8 {
		return nil
	}

	newStatus := binary.LittleEndian.Uint32(data[4:8])
	oldStatus := session.GetStatus()

	h.logger.Debug("V3 status change",
		"uin", 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)

	// 3. Call service layer with typed request
	statusReq := StatusChangeRequest{
		UIN:       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)
		return nil
	}

	h.logger.Debug("V3 status change processed",
		"uin", uin,
		"notify_count", len(statusResult.NotifyTargets),
	)

	// 4. Broadcast status change to contacts using packet builder
	// The service layer returns the list of users to notify
	for _, target := range statusResult.NotifyTargets {
		targetSession := h.sessions.GetSession(target.UIN)
		if targetSession != nil {
			if h.dispatcher != nil {
				// Use central dispatcher - routes to correct protocol based on target's version
				_ = h.dispatcher.SendStatusChange(targetSession, uin, newStatus)
			} else {
				// Fallback to V3 format if dispatcher not set
				statusPkt := h.packetBuilder.BuildUserStatus(
					targetSession.NextServerSeqNum(),
					uin,
					newStatus,
				)
				_ = h.sender.SendToSession(targetSession, statusPkt)
			}
		}
	}

	return nil
}

// handleMessage processes through-server messages (0x010E)
// From iserverd v3_process_sysmsg(): forwards messages to target user
// Format: TIMESTAMP(4) + TO_UIN(4) + MSG_TYPE(2) + MSG_LEN(2) + MESSAGE
//
// Refactored to use service layer (ProcessMessage) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> route
func (h *V3Handler) handleMessage(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	// 1. Send ACK using packet builder
	_ = h.sender.SendPacket(session.Addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 2. Unmarshal packet to typed request struct
	req, err := h.parseMessagePacket(data, uin)
	if err != nil {
		h.logger.Debug("V3 message parse error", "from", uin, "err", err)
		return nil
	}

	h.logger.Info("V3 message received",
		"from", req.FromUIN,
		"to", req.ToUIN,
		"type", fmt.Sprintf("0x%04X", req.MsgType),
		"msg_len", len(req.Message),
	)

	// 3. Call service layer with typed request
	ctx := context.Background()
	result, err := h.service.ProcessMessage(ctx, session, req)
	if err != nil {
		h.logger.Error("message processing failed",
			"from", req.FromUIN,
			"to", req.ToUIN,
			"err", err,
		)
		return nil
	}

	// 4. Route message based on service result
	if result.TargetOnline {
		// Target is online - forward message via dispatcher or direct send
		targetSession := h.sessions.GetSession(req.ToUIN)
		if targetSession != nil {
			if h.dispatcher != nil {
				// Use central dispatcher - routes to correct protocol based on target's version
				_ = h.dispatcher.SendOnlineMessage(targetSession, req.FromUIN, req.MsgType, req.Message)
			} else {
				// Fallback to V3 format if dispatcher not set
				_ = h.sendOnlineMessage(targetSession, req.FromUIN, req.MsgType, req.Message, seq2)
			}
			h.logger.Debug("V3 message forwarded",
				"from", req.FromUIN,
				"to", req.ToUIN,
				"target_version", targetSession.Version,
			)
		}
	} else if result.StoredOffline {
		// Message was stored for offline delivery by the service layer
		h.logger.Info("V3 message stored for offline delivery",
			"from", req.FromUIN,
			"to", req.ToUIN,
			"type", fmt.Sprintf("0x%04X", req.MsgType),
		)
	}

	return nil
}

// parseMessagePacket parses a V3 message packet into a typed MessageRequest struct.
// Format: TIMESTAMP(4) + TO_UIN(4) + MSG_TYPE(2) + MSG_LEN(2) + MESSAGE
func (h *V3Handler) parseMessagePacket(data []byte, fromUIN uint32) (MessageRequest, error) {
	req := MessageRequest{
		FromUIN: fromUIN,
	}

	if len(data) < 12 {
		return req, fmt.Errorf("message packet too short: %d bytes", len(data))
	}

	offset := 0

	// Skip timestamp (4 bytes)
	offset += 4

	// Target UIN (4 bytes)
	req.ToUIN = binary.LittleEndian.Uint32(data[offset : offset+4])
	offset += 4

	// Message type (2 bytes)
	req.MsgType = binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2

	// Message length (2 bytes)
	msgLen := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2

	// Message content
	if msgLen > 0 && offset+int(msgLen) <= len(data) {
		req.Message = string(data[offset : offset+int(msgLen)])
		// Remove null terminator if present
		if len(req.Message) > 0 && req.Message[len(req.Message)-1] == 0 {
			req.Message = req.Message[:len(req.Message)-1]
		}
	}

	return req, nil
}

// handleUserAdd processes user add to contact list (0x053C)
// From iserverd v3_process_useradd(): adds user and sends "you were added" notification
//
// Refactored to use service layer (ProcessUserAdd) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> send notifications
func (h *V3Handler) handleUserAdd(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	// 1. Send ACK using packet builder
	_ = h.sender.SendPacket(session.Addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 2. Unmarshal packet to typed request struct
	req, err := h.parseUserAddPacket(data, uin)
	if err != nil {
		h.logger.Debug("V3 user add parse error", "uin", uin, "err", err)
		return nil
	}

	h.logger.Debug("V3 user add",
		"from", req.FromUIN,
		"target", req.TargetUIN,
	)

	// Add to contact list (handler responsibility - session management)
	contacts := session.GetContactList()
	contacts = append(contacts, req.TargetUIN)
	session.SetContactList(contacts)

	// 3. Call service layer with typed request
	ctx := context.Background()
	result, err := h.service.ProcessUserAdd(ctx, session.Instance, req)
	if err != nil {
		h.logger.Error("user add processing failed", "from", req.FromUIN, "target", req.TargetUIN, "err", err)
		return nil
	}

	// 4. Send notifications based on service result
	if result.TargetOnline {
		// Send target's online status to the user who added them
		_ = h.sendUserOnline(session, req.TargetUIN, result.TargetStatus)

		// Send "you were added" notification to target user if service says to
		if result.SendYouWereAdded {
			targetSession := h.sessions.GetSession(req.TargetUIN)
			if targetSession != nil {
				// Message format: nick#FE#first#FE#last#FE#email#FE#auth
				// Using UIN as nick for now since we don't have user info
				youWereAddedMsg := fmt.Sprintf("%d\xFE\xFE\xFE\xFE0", req.FromUIN)

				if h.dispatcher != nil {
					// Use dispatcher for cross-protocol support
					_ = h.dispatcher.SendOnlineMessage(targetSession, req.FromUIN, ICQLegacyMsgAdded, youWereAddedMsg)
				} else {
					// Fallback to V3 format
					_ = h.sendOnlineMessage(targetSession, req.FromUIN, ICQLegacyMsgAdded, youWereAddedMsg, 0)
				}

				// Also send the adder's online status to the target.
				// The target receives "you were added" but won't see the
				// adder as online unless we explicitly tell them.
				if h.dispatcher != nil {
					_ = h.dispatcher.SendUserOnline(targetSession, req.FromUIN, session.GetStatus())
				} else {
					_ = h.sendUserOnline(targetSession, req.FromUIN, session.GetStatus())
				}

				h.logger.Debug("V3 sent 'you were added' notification",
					"from", req.FromUIN,
					"to", req.TargetUIN,
				)
			}
		}
	}

	return nil
}

// parseUserAddPacket parses a V3 user add packet into a typed UserAddRequest struct.
// Format: TIMESTAMP(4) + TARGET_UIN(4)
func (h *V3Handler) parseUserAddPacket(data []byte, fromUIN uint32) (UserAddRequest, error) {
	req := UserAddRequest{
		FromUIN: fromUIN,
	}

	if len(data) < 8 {
		return req, fmt.Errorf("user add packet too short: %d bytes", len(data))
	}

	// Skip timestamp (4 bytes)
	// Target UIN (4 bytes)
	req.TargetUIN = binary.LittleEndian.Uint32(data[4:8])

	return req, nil
}

// handleGetInfo processes user info request (0x05FA)
// From iserverd v3_process_getinfo(): sends basic, home, home_web, work, work_web info
//
// Refactored to use service layer (GetUserInfoForProtocol) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
func (h *V3Handler) handleGetInfo(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	// 1. Send ACK using packet builder
	_ = h.sender.SendPacket(session.Addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 2. Unmarshal packet to extract target UIN
	// Format: TIMESTAMP(4) + TARGET_UIN(4)
	if len(data) < 8 {
		return nil
	}

	targetUIN := binary.LittleEndian.Uint32(data[4:8])

	h.logger.Debug("V3 get info request",
		"from", uin,
		"target", targetUIN,
	)

	// 3. Call service layer to get user info
	ctx := context.Background()
	info, err := h.service.GetUserInfoForProtocol(ctx, targetUIN)
	if err != nil {
		h.logger.Error("failed to get user info", "target", targetUIN, "err", err)
		// Still send minimal info packets even on error
		info = &UserInfoResult{
			UIN:      targetUIN,
			Nickname: fmt.Sprintf("%d", targetUIN),
		}
	}

	// 4. Build and send all user info packets using packet builder
	// (matching iserverd v3_process_getinfo which sends 5 packets)
	_ = h.sender.SendToSession(session, h.packetBuilder.BuildBasicInfo(session.NextServerSeqNum(), seq2, session.UIN, info))
	_ = h.sender.SendToSession(session, h.packetBuilder.BuildHomeInfo(session.NextServerSeqNum(), seq2, session.UIN, info))
	_ = h.sender.SendToSession(session, h.packetBuilder.BuildHomeWeb(session.NextServerSeqNum(), seq2, session.UIN, info))
	_ = h.sender.SendToSession(session, h.packetBuilder.BuildWorkInfo(session.NextServerSeqNum(), seq2, session.UIN, info))
	_ = h.sender.SendToSession(session, h.packetBuilder.BuildWorkWeb(session.NextServerSeqNum(), seq2, session.UIN, info))

	return nil
}

// V3 packet sending helpers

// sendAck sends ACK packet (V3 format from iserverd v3_send_ack)
func (h *V3Handler) sendAck(addr *net.UDPAddr, seq1, seq2 uint16, uin uint32) error {
	// V3 ACK format: VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + RESERVED(4)
	pkt := make([]byte, 16)
	binary.LittleEndian.PutUint16(pkt[0:2], ICQLegacyVersionV3)
	binary.LittleEndian.PutUint16(pkt[2:4], ICQLegacySrvAck)
	binary.LittleEndian.PutUint16(pkt[4:6], seq1)
	binary.LittleEndian.PutUint16(pkt[6:8], seq2)
	binary.LittleEndian.PutUint32(pkt[8:12], uin)
	binary.LittleEndian.PutUint32(pkt[12:16], 0) // reserved

	return h.sender.SendPacket(addr, pkt)
}

// sendNotConnected sends not connected error
func (h *V3Handler) sendNotConnected(addr *net.UDPAddr, seq2 uint16, uin uint32) error {
	pkt := make([]byte, 16)
	binary.LittleEndian.PutUint16(pkt[0:2], ICQLegacyVersionV3)
	binary.LittleEndian.PutUint16(pkt[2:4], ICQLegacySrvNotConnected)
	binary.LittleEndian.PutUint16(pkt[4:6], 0)
	binary.LittleEndian.PutUint16(pkt[6:8], seq2)
	binary.LittleEndian.PutUint32(pkt[8:12], uin)
	binary.LittleEndian.PutUint32(pkt[12:16], 0)

	return h.sender.SendPacket(addr, pkt)
}

// sendUserOnline sends user online notification
// From iserverd v3_send_user_online()
func (h *V3Handler) sendUserOnline(session *LegacySession, uin uint32, status uint32) error {
	// V3 USER_ONLINE format from iserverd:
	// header(16) + UIN(4) + IP(4) + PORT(4) + INT_IP(4) + DC_TYPE(1) + STATUS(2) + ESTAT(2) + DCVER(2) + UNKNOWN(2)
	// Total: 16 + 4 + 4 + 4 + 4 + 1 + 2 + 2 + 2 + 2 = 41 bytes

	pkt := make([]byte, 41)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacySrvUserOnline)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0) // seq2
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved
	offset += 4

	// UIN of the user who is online
	binary.LittleEndian.PutUint32(pkt[offset:], uin)
	offset += 4

	// IP address (0 for privacy - V3 clients crash on non-V3 client connect)
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	// TCP port (0 for privacy)
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	// Internal IP (0 for privacy)
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	// DC type (0)
	pkt[offset] = 0
	offset++

	// Status (low word)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(status&0xFFFF))
	offset += 2

	// Extended status (high word)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(status>>16))
	offset += 2

	// DC version
	binary.LittleEndian.PutUint16(pkt[offset:], 0)
	offset += 2

	// Unknown
	binary.LittleEndian.PutUint16(pkt[offset:], 0)
	offset += 2

	h.logger.Debug("sending V3 user online notification",
		"to", session.UIN,
		"online_uin", uin,
		"status", fmt.Sprintf("0x%08X", status),
	)

	return h.sender.SendToSession(session, pkt[:offset])
}

// handleOfflineMsgReq processes offline message request (0x044C)
// From iserverd v3_process_sysmsg_req()
func (h *V3Handler) handleOfflineMsgReq(session *LegacySession, seq1, seq2 uint16, uin uint32) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	ctx := context.Background()

	// Fetch offline messages from database
	messages, err := h.service.GetOfflineMessages(ctx, uin)
	if err != nil {
		h.logger.Error("failed to get offline messages", "uin", uin, "err", err)
		return h.sendOfflineMsgDone(session, seq2)
	}

	h.logger.Debug("V3 offline message request",
		"uin", uin,
		"message_count", len(messages),
	)

	// Send each offline message
	for _, msg := range messages {
		if err := h.sendOfflineMessage(session, seq2, &msg); err != nil {
			h.logger.Error("failed to send offline message",
				"uin", uin,
				"from", msg.FromUIN,
				"err", err,
			)
		}
	}

	// Send end of offline messages
	return h.sendOfflineMsgDone(session, seq2)
}

// handleSetBasicInfo processes set basic info (0x050A)
// Format: TIMESTAMP(4) + NICK_LEN(2)+NICK + FIRST_LEN(2)+FIRST + LAST_LEN(2)+LAST + EMAIL_LEN(2)+EMAIL
func (h *V3Handler) handleSetBasicInfo(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	if len(data) < 6 {
		return h.sendReplyOK(session, seq2, 0x01E0)
	}

	r := bytes.NewReader(data[4:]) // skip timestamp
	nick, _ := ParseLegacyString(r, true)
	first, _ := ParseLegacyString(r, true)
	last, _ := ParseLegacyString(r, true)
	email, _ := ParseLegacyString(r, true)

	ctx := context.Background()
	info := state.ICQBasicInfo{
		Nickname:     nick,
		FirstName:    first,
		LastName:     last,
		EmailAddress: email,
	}
	if err := h.service.UpdateBasicInfo(ctx, uin, info); err != nil {
		h.logger.Error("V3 set basic info failed", "uin", uin, "err", err)
	}

	return h.sendReplyOK(session, seq2, 0x01E0)
}

// handleSetHomeInfo processes set home info (0x0582)
// Format: TIMESTAMP(4) + ADDR_LEN(2)+ADDR + CITY_LEN(2)+CITY + STATE_LEN(2)+STATE + COUNTRY(2) + PHONE_LEN(2)+PHONE + FAX_LEN(2)+FAX + CELL_LEN(2)+CELL + ZIP(4) + GMT(2) + AUTH(1) + WEBAWARE(1) + HIDEIP(1) + PUBLISH_EMAIL(1)
func (h *V3Handler) handleSetHomeInfo(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	if len(data) < 6 {
		return h.sendReplyOK(session, seq2, 0x0280)
	}

	r := bytes.NewReader(data[4:]) // skip timestamp
	address, _ := ParseLegacyString(r, true)
	city, _ := ParseLegacyString(r, true)
	st, _ := ParseLegacyString(r, true)
	var country uint16
	_ = binary.Read(r, binary.LittleEndian, &country)
	phone, _ := ParseLegacyString(r, true)
	fax, _ := ParseLegacyString(r, true)
	cell, _ := ParseLegacyString(r, true)
	var zipCode uint32
	_ = binary.Read(r, binary.LittleEndian, &zipCode)
	var gmt uint16
	_ = binary.Read(r, binary.LittleEndian, &gmt)
	var auth, webaware uint8
	_ = binary.Read(r, binary.LittleEndian, &auth)
	_ = binary.Read(r, binary.LittleEndian, &webaware)

	// Read existing basic info to avoid overwriting nick/first/last/email
	ctx := context.Background()
	existing, err := h.service.GetFullUserInfo(ctx, uin)
	if err == nil && existing != nil {
		existing.ICQInfo.Basic.Address = address
		existing.ICQInfo.Basic.City = city
		existing.ICQInfo.Basic.State = st
		existing.ICQInfo.Basic.CountryCode = country
		existing.ICQInfo.Basic.Phone = phone
		existing.ICQInfo.Basic.Fax = fax
		existing.ICQInfo.Basic.CellPhone = cell
		existing.ICQInfo.Basic.ZIPCode = fmt.Sprintf("%d", zipCode)
		existing.ICQInfo.Basic.GMTOffset = uint8(gmt)
		if err := h.service.UpdateBasicInfo(ctx, uin, existing.ICQInfo.Basic); err != nil {
			h.logger.Error("V3 set home info failed", "uin", uin, "err", err)
		}
	}
	if err := h.service.SetAuthMode(ctx, uin, auth == 0); err != nil {
		h.logger.Error("V3 set home auth failed", "uin", uin, "err", err)
	}

	return h.sendReplyOK(session, seq2, 0x0280)
}

// handleSetHomeWeb processes set home web (0x058C)
// Format: TIMESTAMP(4) + AGE(2) + SEX(1) + HP_LEN(2)+HP + BIRTH_YEAR(2) + BIRTH_MONTH(1) + BIRTH_DAY(1) + LANG1(1) + LANG2(1) + LANG3(1)
func (h *V3Handler) handleSetHomeWeb(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	if len(data) < 7 {
		return h.sendReplyOK(session, seq2, 0x0294)
	}

	r := bytes.NewReader(data[4:]) // skip timestamp
	var age uint16
	_ = binary.Read(r, binary.LittleEndian, &age)
	var sex uint8
	_ = binary.Read(r, binary.LittleEndian, &sex)
	hp, _ := ParseLegacyString(r, true)
	var birthYear uint16
	_ = binary.Read(r, binary.LittleEndian, &birthYear)
	var birthMonth, birthDay, lang1, lang2, lang3 uint8
	_ = binary.Read(r, binary.LittleEndian, &birthMonth)
	_ = binary.Read(r, binary.LittleEndian, &birthDay)
	_ = binary.Read(r, binary.LittleEndian, &lang1)
	_ = binary.Read(r, binary.LittleEndian, &lang2)
	_ = binary.Read(r, binary.LittleEndian, &lang3)

	ctx := context.Background()
	info := state.ICQMoreInfo{
		Gender:       uint16(sex),
		HomePageAddr: hp,
		BirthYear:    birthYear,
		BirthMonth:   birthMonth,
		BirthDay:     birthDay,
		Lang1:        lang1,
		Lang2:        lang2,
		Lang3:        lang3,
	}
	if err := h.service.UpdateMoreInfo(ctx, uin, info); err != nil {
		h.logger.Error("V3 set home web failed", "uin", uin, "err", err)
	}

	return h.sendReplyOK(session, seq2, 0x0294)
}

// handleSetWorkInfo processes set work info (0x0578)
// Format: TIMESTAMP(4) + ADDR_LEN(2)+ADDR + CITY_LEN(2)+CITY + STATE_LEN(2)+STATE + COUNTRY(2) + COMPANY_LEN(2)+COMPANY + TITLE_LEN(2)+TITLE + DEPT(2) + PHONE_LEN(2)+PHONE + FAX_LEN(2)+FAX + PAGER_LEN(2)+PAGER + ZIP(4)
func (h *V3Handler) handleSetWorkInfo(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	if len(data) < 6 {
		return h.sendReplyOK(session, seq2, 0x026C)
	}

	r := bytes.NewReader(data[4:]) // skip timestamp
	address, _ := ParseLegacyString(r, true)
	city, _ := ParseLegacyString(r, true)
	st, _ := ParseLegacyString(r, true)
	var country uint16
	_ = binary.Read(r, binary.LittleEndian, &country)
	company, _ := ParseLegacyString(r, true)
	position, _ := ParseLegacyString(r, true)
	var dept uint16
	_ = binary.Read(r, binary.LittleEndian, &dept)
	phone, _ := ParseLegacyString(r, true)
	fax, _ := ParseLegacyString(r, true)
	// pager field — not stored in ICQWorkInfo, skip
	_, _ = ParseLegacyString(r, true)
	var zipCode uint32
	_ = binary.Read(r, binary.LittleEndian, &zipCode)

	// Read existing work info to preserve WebPage (set separately via 0x05BE)
	ctx := context.Background()
	existing, existErr := h.service.GetFullUserInfo(ctx, uin)
	if existErr == nil && existing != nil {
		existing.ICQInfo.Work.Address = address
		existing.ICQInfo.Work.City = city
		existing.ICQInfo.Work.State = st
		existing.ICQInfo.Work.CountryCode = country
		existing.ICQInfo.Work.Company = company
		existing.ICQInfo.Work.Position = position
		existing.ICQInfo.Work.Phone = phone
		existing.ICQInfo.Work.Fax = fax
		existing.ICQInfo.Work.ZIPCode = fmt.Sprintf("%d", zipCode)
		if err := h.service.UpdateWorkInfo(ctx, uin, existing.ICQInfo.Work); err != nil {
			h.logger.Error("V3 set work info failed", "uin", uin, "err", err)
		}
	}

	return h.sendReplyOK(session, seq2, 0x026C)
}

// handleSetWorkWeb processes set work web (0x05BE)
// Format: TIMESTAMP(4) + WEB_LEN(2)+WEB
func (h *V3Handler) handleSetWorkWeb(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	if len(data) < 6 {
		return h.sendReplyOK(session, seq2, 0x0258)
	}

	r := bytes.NewReader(data[4:]) // skip timestamp
	web, _ := ParseLegacyString(r, true)

	// Read existing work info to avoid overwriting other fields
	ctx := context.Background()
	existing, err := h.service.GetFullUserInfo(ctx, uin)
	if err == nil && existing != nil {
		existing.ICQInfo.Work.WebPage = web
		if err := h.service.UpdateWorkInfo(ctx, uin, existing.ICQInfo.Work); err != nil {
			h.logger.Error("V3 set work web failed", "uin", uin, "err", err)
		}
	}

	return h.sendReplyOK(session, seq2, 0x0258)
}

// handleVisibleList processes visible list (0x06AE)
func (h *V3Handler) handleVisibleList(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 visible list", "uin", uin)

	return nil
}

// handleInvisibleList processes invisible list (0x06A4)
func (h *V3Handler) handleInvisibleList(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 invisible list", "uin", uin)

	return nil
}

// handleUnknownDep processes unknown pre-auth related request (0x0604)
func (h *V3Handler) handleUnknownDep(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 unknown dep request", "uin", uin)

	return nil
}

// handleSearchStart processes search user request (0x05C8)
// From V3 protocol: TIMESTAMP(4) + TYPE(2) + COMP(2) + LEN(2) + STRING
// Type: 0x00FF=UIN, 0x01FF=Nick, 0x02FF=First, 0x03FF=Last, etc.
// Comp: 0x0000=contains, 0x0001=doesn't contain, 0x0002=is, etc.
func (h *V3Handler) handleSearchStart(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	ctx := context.Background()

	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	// Parse search parameters - format: TIMESTAMP(4) + TYPE(2) + COMP(2) + LEN(2) + STRING
	if len(data) < 10 {
		h.logger.Debug("V3 search start - packet too short", "uin", uin, "len", len(data))
		return h.sendSearchDone(session, seq2)
	}

	offset := 4 // Skip timestamp

	searchType := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2
	compType := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2
	strLen := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2

	var searchStr string
	if len(data) >= offset+int(strLen) && strLen > 0 {
		searchStr = string(data[offset : offset+int(strLen)])
		// Remove null terminator if present
		if len(searchStr) > 0 && searchStr[len(searchStr)-1] == 0 {
			searchStr = searchStr[:len(searchStr)-1]
		}
	}

	h.logger.Debug("V3 search start",
		"uin", uin,
		"search_type", fmt.Sprintf("0x%04X", searchType),
		"comp_type", compType,
		"search_str", searchStr,
	)

	// Handle UIN search (type 0x00FF)
	if searchType == 0x00FF && searchStr != "" {
		// Try to parse as UIN
		var targetUIN uint64
		_, err := fmt.Sscanf(searchStr, "%d", &targetUIN)
		if err == nil && targetUIN > 0 {
			// Search in database first (includes both online and offline users)
			result, err := h.service.SearchByUIN(ctx, uint32(targetUIN))
			if err == nil && result != nil {
				// User found in database - truncate fields for legacy client safety
				nick := truncateField(result.Nickname, 20, h.logger, "nickname", result.UIN)
				first := truncateField(result.FirstName, 64, h.logger, "first_name", result.UIN)
				last := truncateField(result.LastName, 64, h.logger, "last_name", result.UIN)
				email := truncateField(result.Email, 64, h.logger, "email", result.UIN)
				_ = h.sendSearchFound(session, seq2, result.UIN, nick, first, last, email, 0)
				h.logger.Debug("V3 search found user in database",
					"searcher", uin,
					"found", result.UIN,
					"nick", result.Nickname,
				)
			} else {
				h.logger.Debug("V3 search - user not found",
					"searcher", uin,
					"target", targetUIN,
					"err", err,
				)
			}
		}
	}

	// Send search done
	return h.sendSearchDone(session, seq2)
}

// handleGetDeps1 processes in-session pre-auth list request (0x05F0).
// Historically called "get departments list" in iserverd. Used by the client
// to replicate the pre-auth response during a normal session.
// From iserverd v3_process_getdeps1() - sends ICQ_CMDxSND_USERxDEPS_LIST1 (0x0082)
func (h *V3Handler) handleGetDeps1(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 get deps1 request", "uin", uin)

	// Send deps list using 0x0082 (during session, not login)
	return h.sendDeptsList1(session, seq2)
}

// sendDeptsList1 sends the in-session pre-auth list response (0x0082).
// Historically called "departments list" in iserverd (from its Users_Deps database table).
// Different from login depslist (0x0032).
func (h *V3Handler) sendDeptsList1(session *LegacySession, seq2 uint16) error {
	// V3 DEPS_LIST1 format from iserverd:
	// VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + RESERVED(4) +
	// UNKNOWN(2) + DEPLIST_VERSION(4) + COUNT(4) + [deps...] + TRAILER(4)

	// For now, send empty list with version 1
	pkt := make([]byte, 32)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacySrvUserDepsList1) // 0x0082 - ICQ_CMDxSND_USERxDEPS_LIST1
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], seq2)
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved
	offset += 4

	// Unknown field (0x003C from iserverd)
	binary.LittleEndian.PutUint16(pkt[offset:], 0x003C)
	offset += 2

	// Deplist version
	binary.LittleEndian.PutUint32(pkt[offset:], 1)
	offset += 4

	// Count = 0 (empty deps list)
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	// Trailer from iserverd
	binary.LittleEndian.PutUint16(pkt[offset:], 0x0002)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0x002a)
	offset += 2

	return h.sender.SendToSession(session, pkt[:offset])
}

// sendOfflineMessage sends an offline message to a V3 client
// From iserverd v3_send_offline_message()
// Format: header(16) + FROM_UIN(4) + YEAR(2) + MONTH(1) + DAY(1) + HOUR(1) + MINUTE(1) + MSG_TYPE(2) + MSG_LEN(2) + MESSAGE
func (h *V3Handler) sendOfflineMessage(session *LegacySession, seq2 uint16, msg *LegacyOfflineMessage) error {
	// Build message data
	msgBytes := []byte(msg.Message)
	pktLen := 16 + 4 + 2 + 1 + 1 + 1 + 1 + 2 + 2 + len(msgBytes) + 1
	pkt := make([]byte, pktLen)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacySrvSysMsgOffline) // 0x00DC
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], seq2)
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved
	offset += 4

	// From UIN
	binary.LittleEndian.PutUint32(pkt[offset:], msg.FromUIN)
	offset += 4

	// Timestamp: YEAR(2) + MONTH(1) + DAY(1) + HOUR(1) + MINUTE(1)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(msg.Timestamp.Year()))
	offset += 2
	pkt[offset] = byte(msg.Timestamp.Month())
	offset++
	pkt[offset] = byte(msg.Timestamp.Day())
	offset++
	pkt[offset] = byte(msg.Timestamp.Hour())
	offset++
	pkt[offset] = byte(msg.Timestamp.Minute())
	offset++

	// Message type
	binary.LittleEndian.PutUint16(pkt[offset:], msg.MsgType)
	offset += 2

	// Message length (including null terminator)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(msgBytes)+1))
	offset += 2

	// Message content
	copy(pkt[offset:], msgBytes)
	offset += len(msgBytes)
	pkt[offset] = 0 // null terminator

	h.logger.Debug("sending V3 offline message",
		"to", session.UIN,
		"from", msg.FromUIN,
		"type", fmt.Sprintf("0x%04X", msg.MsgType),
		"timestamp", msg.Timestamp,
	)

	return h.sender.SendToSession(session, pkt)
}

// sendOfflineMsgDone sends end of offline messages
func (h *V3Handler) sendOfflineMsgDone(session *LegacySession, seq2 uint16) error {
	pkt := make([]byte, 16)
	binary.LittleEndian.PutUint16(pkt[0:2], ICQLegacyVersionV3)
	binary.LittleEndian.PutUint16(pkt[2:4], 0x00E6) // ICQ_CMDxSND_SYSxMSGxDONE
	binary.LittleEndian.PutUint16(pkt[4:6], session.NextServerSeqNum())
	binary.LittleEndian.PutUint16(pkt[6:8], seq2)
	binary.LittleEndian.PutUint32(pkt[8:12], session.UIN)
	binary.LittleEndian.PutUint32(pkt[12:16], 0)

	return h.sender.SendToSession(session, pkt)
}

// sendReplyOK sends a generic OK response
func (h *V3Handler) sendReplyOK(session *LegacySession, seq2 uint16, command uint16) error {
	pkt := make([]byte, 16)
	binary.LittleEndian.PutUint16(pkt[0:2], ICQLegacyVersionV3)
	binary.LittleEndian.PutUint16(pkt[2:4], command)
	binary.LittleEndian.PutUint16(pkt[4:6], session.NextServerSeqNum())
	binary.LittleEndian.PutUint16(pkt[6:8], seq2)
	binary.LittleEndian.PutUint32(pkt[8:12], session.UIN)
	binary.LittleEndian.PutUint32(pkt[12:16], 0)

	return h.sender.SendToSession(session, pkt)
}

// sendSearchDone sends search complete response
// From iserverd v3_send_search_finished()
// Packet format (17 bytes total):
//
//	VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + RESERVED(4) + MORE(1)
//
// The 'more' parameter indicates if there are more search results available:
//
//	0 = no more results, 1 = more results available (pagination)
func (h *V3Handler) sendSearchDone(session *LegacySession, seq2 uint16, more ...bool) error {
	pkt := make([]byte, 17)
	binary.LittleEndian.PutUint16(pkt[0:2], ICQLegacyVersionV3)
	binary.LittleEndian.PutUint16(pkt[2:4], 0x00A0) // ICQ_CMDxSND_SEARCHxDONE
	binary.LittleEndian.PutUint16(pkt[4:6], session.NextServerSeqNum())
	binary.LittleEndian.PutUint16(pkt[6:8], seq2)
	binary.LittleEndian.PutUint32(pkt[8:12], session.UIN)
	binary.LittleEndian.PutUint32(pkt[12:16], 0) // reserved

	// Set 'more' flag - indicates if more search results are available
	if len(more) > 0 && more[0] {
		pkt[16] = 1 // more results available
	} else {
		pkt[16] = 0 // no more results
	}

	return h.sender.SendToSession(session, pkt)
}

// sendSearchFound sends a search result
// From iserverd v3_send_found_info()
// Format: header(16) + UIN(4) + NICK_LEN(2) + NICK + FIRST_LEN(2) + FIRST +
//
//	LAST_LEN(2) + LAST + EMAIL_LEN(2) + EMAIL + AUTH(1)
func (h *V3Handler) sendSearchFound(session *LegacySession, seq2 uint16, foundUIN uint32, nick, first, last, email string, auth uint8) error {
	// Calculate packet size
	pktSize := 16 + 4 + 2 + len(nick) + 1 + 2 + len(first) + 1 + 2 + len(last) + 1 + 2 + len(email) + 1 + 1
	pkt := make([]byte, pktSize)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0x008C) // ICQ_CMDxSND_SEARCHxFOUND
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], seq2)
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved
	offset += 4

	// Found user UIN
	binary.LittleEndian.PutUint32(pkt[offset:], foundUIN)
	offset += 4

	// Nick (length-prefixed with null terminator)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(nick)+1))
	offset += 2
	copy(pkt[offset:], nick)
	offset += len(nick)
	pkt[offset] = 0
	offset++

	// First name
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(first)+1))
	offset += 2
	copy(pkt[offset:], first)
	offset += len(first)
	pkt[offset] = 0
	offset++

	// Last name
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(last)+1))
	offset += 2
	copy(pkt[offset:], last)
	offset += len(last)
	pkt[offset] = 0
	offset++

	// Email
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(email)+1))
	offset += 2
	copy(pkt[offset:], email)
	offset += len(email)
	pkt[offset] = 0
	offset++

	// Auth flag
	pkt[offset] = auth
	offset++

	h.logger.Debug("V3 sending search found",
		"to", session.UIN,
		"found_uin", foundUIN,
		"nick", nick,
		"packet_hex", fmt.Sprintf("%X", pkt[:offset]),
		"packet_len", offset,
	)

	return h.sender.SendToSession(session, pkt[:offset])
}

// sendOnlineMessage sends an online system message to a V3/V4 client
// From iserverd v3_send_user_message()
// Format: header(16) + FROM_UIN(4) + MSG_TYPE(2) + MSG_LEN(2) + MESSAGE
// Note: V3 packets do NOT have a checkcode - they have a reserved field (always 0)
func (h *V3Handler) sendOnlineMessage(session *LegacySession, fromUIN uint32, msgType uint16, message string, seq2 uint16) error {
	msgBytes := []byte(message)

	h.logger.Debug("V3 sending online message",
		"to", session.UIN,
		"from", fromUIN,
		"type", fmt.Sprintf("0x%04X", msgType),
		"msg_len", len(msgBytes),
	)

	// Send V3 format packet
	pktSize := 16 + 4 + 2 + 2 + len(msgBytes) + 1
	pkt := make([]byte, pktSize)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacySrvSysMsgOnline) // 0x0104
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], seq2)
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved (V3 has NO checkcode!)
	offset += 4

	// From UIN
	binary.LittleEndian.PutUint32(pkt[offset:], fromUIN)
	offset += 4

	// Message type (mask high byte for V3 clients)
	binary.LittleEndian.PutUint16(pkt[offset:], msgType&0x00FF)
	offset += 2

	// Message length (including null terminator)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(msgBytes)+1))
	offset += 2

	// Message content
	copy(pkt[offset:], msgBytes)
	offset += len(msgBytes)
	pkt[offset] = 0 // null terminator
	offset++

	h.logger.Debug("V3 sending online message packet",
		"to", session.UIN,
		"from", fromUIN,
		"packet_hex", fmt.Sprintf("%X", pkt[:offset]),
	)

	return h.sender.SendToSession(session, pkt[:offset])
}

// sendUserOffline sends user offline notification
// From iserverd v3_send_user_offline()
func (h *V3Handler) sendUserOffline(session *LegacySession, uin uint32) error {
	// V3 USER_OFFLINE format: header(16) + UIN(4)
	pkt := make([]byte, 20)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacySrvUserOffline)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0) // seq2
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved
	offset += 4

	// UIN of the user who went offline
	binary.LittleEndian.PutUint32(pkt[offset:], uin)
	offset += 4

	h.logger.Debug("sending V3 user offline notification",
		"to", session.UIN,
		"offline_uin", uin,
	)

	return h.sender.SendToSession(session, pkt[:offset])
}

// sendUserStatus sends user status change notification
// From iserverd v3_send_user_status() in make_packet.cpp
// This is used when a user changes status while already online
// (e.g., Away -> Online, Online -> DND)
// Format: header(16) + UIN(4) + STATUS(2) + ESTAT(2)
func (h *V3Handler) sendUserStatus(session *LegacySession, uin uint32, status uint32) error {
	// V3 USER_STATUS format from iserverd:
	// VERSION(2) + COMMAND(2) + SEQ1(2) + SEQ2(2) + UIN(4) + RESERVED(4) +
	// TARGET_UIN(4) + STATUS(2) + ESTAT(2)
	pkt := make([]byte, 24)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacySrvUserStatus) // 0x01A4
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0) // seq2
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0) // reserved
	offset += 4

	// UIN of the user whose status changed
	binary.LittleEndian.PutUint32(pkt[offset:], uin)
	offset += 4

	// Status (low word)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(status&0xFFFF))
	offset += 2

	// Extended status (high word)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(status>>16))
	offset += 2

	h.logger.Debug("sending V3 user status change notification",
		"to", session.UIN,
		"changed_uin", uin,
		"status", fmt.Sprintf("0x%08X", status),
	)

	return h.sender.SendToSession(session, pkt[:offset])
}

// handleGetNotes processes get notes request (0x05AA)
// From iserverd v3_process_notes() - returns user's notes
func (h *V3Handler) handleGetNotes(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	// Parse: TIMESTAMP(4) + TARGET_UIN(4)
	if len(data) < 8 {
		return nil
	}

	targetUIN := binary.LittleEndian.Uint32(data[4:8])

	h.logger.Debug("V3 get notes", "uin", uin, "target", targetUIN)

	// Retrieve notes from database via service layer
	ctx := context.Background()
	notes, err := h.service.GetNotes(ctx, targetUIN)
	if err != nil {
		h.logger.Debug("V3 get notes failed", "uin", uin, "target", targetUIN, "err", err)
		// Send empty notes on error
		notes = ""
	}

	// Send notes response
	return h.sendNotes(session, seq2, targetUIN, notes)
}

// handleSetNotes processes set notes request (0x0596)
// From iserverd v3_process_setnotes()
// Data format: TIMESTAMP(4) + NOTES_LEN(2) + NOTES
func (h *V3Handler) handleSetNotes(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	// Parse notes from packet
	// Format: TIMESTAMP(4) + NOTES_LEN(2) + NOTES
	if len(data) < 6 {
		h.logger.Debug("V3 set notes - data too short", "uin", uin, "len", len(data))
		return h.sendReplyOK(session, seq2, 0x01CC)
	}

	offset := 4 // Skip timestamp

	// Read notes length (2 bytes)
	notesLen := binary.LittleEndian.Uint16(data[offset : offset+2])
	offset += 2

	// Read notes content
	var notes string
	if notesLen > 0 && offset+int(notesLen) <= len(data) {
		notes = string(data[offset : offset+int(notesLen)])
		// Remove null terminator if present
		if len(notes) > 0 && notes[len(notes)-1] == 0 {
			notes = notes[:len(notes)-1]
		}
	}

	h.logger.Debug("V3 set notes", "uin", uin, "notes_len", len(notes))

	// Save notes to database via service layer
	ctx := context.Background()
	if err := h.service.SetNotes(ctx, uin, notes); err != nil {
		h.logger.Error("V3 set notes failed", "uin", uin, "err", err)
		// Still send OK response to client (matching iserverd behavior)
	}

	// Send OK response (0x01CC = ICQ_CMDxSND_USERxSET_NOTES_OK)
	return h.sendReplyOK(session, seq2, 0x01CC)
}

// handleSetPassword processes set password request (0x049C)
// From iserverd v3_process_setpass()
// Data format: TIMESTAMP(4) + PASSWORD_LEN(2) + NEW_PASSWORD
// Note: iserverd doesn't validate old password, just updates to new password
func (h *V3Handler) handleSetPassword(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	// Parse password from data
	// Format: TIMESTAMP(4) + PASSWORD_LEN(2) + NEW_PASSWORD
	if len(data) < 6 {
		h.logger.Debug("V3 set password - data too short", "uin", uin, "len", len(data))
		return h.sendReplyOK(session, seq2, 0x0140)
	}

	offset := 0

	// Skip timestamp (4 bytes)
	offset += 4

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

	// Sanity check password length
	if pwdLen > 32 {
		pwdLen = 32
	}

	// Read new password
	if offset+int(pwdLen) > len(data) {
		h.logger.Debug("V3 set password - password truncated", "uin", uin)
		return h.sendReplyOK(session, seq2, 0x0140)
	}
	newPassword := string(data[offset : offset+int(pwdLen)])
	// Remove null terminator if present
	if len(newPassword) > 0 && newPassword[len(newPassword)-1] == 0 {
		newPassword = newPassword[:len(newPassword)-1]
	}

	h.logger.Info("V3 set password request",
		"uin", uin,
		"new_password_len", len(newPassword),
	)

	// Update password using service
	// Note: iserverd doesn't validate old password, so we pass empty string
	ctx := context.Background()
	if err := h.service.SetPassword(ctx, uin, "", newPassword); err != nil {
		h.logger.Error("V3 set password failed",
			"uin", uin,
			"err", err,
		)
		// Still send OK response to match iserverd behavior
		// (iserverd doesn't have error handling for this)
	} else {
		h.logger.Info("V3 password updated successfully", "uin", uin)
	}

	// Send OK response (0x0140 = ICQ_CMDxSND_USERxSET_PASSWD_OK)
	return h.sendReplyOK(session, seq2, 0x0140)
}

// handleSetAuth processes set auth mode request (0x0514)
// From iserverd v3_process_setauth()
// Data format: TIMESTAMP(4) + AUTH_MODE(1)
// - AUTH_MODE: 0 = no auth required, 1 = auth required
func (h *V3Handler) handleSetAuth(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	// Parse auth mode - format: TIMESTAMP(4) + AUTH_MODE(1)
	// From iserverd v3_process_setauth():
	// int_pack >> ... >> temp_stamp;
	// auth_mode = 0;
	// int_pack >> auth_mode;
	authRequired := false
	if len(data) >= 5 {
		// Skip timestamp (4 bytes), read auth_mode (1 byte)
		authMode := data[4]
		authRequired = authMode != 0
	}

	h.logger.Debug("V3 set auth",
		"uin", uin,
		"auth_required", authRequired,
	)

	// Update auth mode in database
	ctx := context.Background()
	if err := h.service.SetAuthMode(ctx, uin, authRequired); err != nil {
		h.logger.Error("V3 set auth failed",
			"uin", uin,
			"err", err,
		)
		// Still send OK response to match iserverd behavior
	}

	// Send OK response (0x01F4 = ICQ_CMDxSND_USERxSET_AUTH_OK)
	return h.sendReplyOK(session, seq2, 0x01F4)
}

// handleSetState processes set client state request (0x0528)
// From iserverd v3_process_state() - client state/mode changes
// This is the V3 status change command - when a user changes their status
// (e.g., Online -> Away, Away -> DND), this handler updates the session
// and broadcasts the status change to all contacts.
//
// Data format: TIMESTAMP(4) + STATUS(4) + ESTATUS(4)
// - STATUS: Low 16 bits of status (Online=0, Away=1, DND=2, NA=4, etc.)
// - ESTATUS: High 16 bits of status (extended status flags)
func (h *V3Handler) handleSetState(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	// Parse status - format: TIMESTAMP(4) + STATUS(4) + ESTATUS(4)
	// From iserverd v3_process_status():
	// int_pack >> ... >> new_status >> new_estatus;
	if len(data) < 12 {
		h.logger.Debug("V3 set state - data too short", "uin", uin, "len", len(data))
		return nil
	}

	// Skip timestamp (4 bytes)
	offset := 4

	// Read status (4 bytes) - low word is status, high word is extended status
	newStatus := binary.LittleEndian.Uint32(data[offset : offset+4])
	offset += 4

	// Read extended status (4 bytes) - some clients send this separately
	newEStatus := binary.LittleEndian.Uint32(data[offset : offset+4])

	// Combine status and extended status (iserverd: user.status = new_status, user.estat = new_estatus)
	// The full status is stored as: status | (estatus << 16)
	fullStatus := newStatus | (newEStatus << 16)

	oldStatus := session.GetStatus()
	session.SetStatus(fullStatus)

	h.logger.Info("V3 status change",
		"uin", uin,
		"old_status", fmt.Sprintf("0x%08X", oldStatus),
		"new_status", fmt.Sprintf("0x%08X", fullStatus),
	)

	// Broadcast status change to all contacts who have this user in their list
	// From iserverd v3_process_status(): broadcast_status(user, old_status)
	h.broadcastStatusChange(session, fullStatus)

	return nil
}

// broadcastStatusChange notifies all contacts who have this user in their list
// that the user's status has changed.
// From iserverd broadcast_status() in broadcast.cpp - this function finds all
// online users who have the target user in their contact list and sends them
// a status update notification.
func (h *V3Handler) broadcastStatusChange(session *LegacySession, newStatus uint32) {
	if h.dispatcher == nil {
		return
	}

	// Find all sessions that have this user in their contact list
	// This is the same logic used for online/offline notifications
	contactsToNotify := h.sessions.NotifyContactsOfStatus(session)

	h.logger.Debug("broadcasting status change to contacts",
		"uin", session.UIN,
		"new_status", fmt.Sprintf("0x%08X", newStatus),
		"contacts_to_notify", contactsToNotify,
	)

	for _, contactUIN := range contactsToNotify {
		contactSession := h.sessions.GetSession(contactUIN)
		if contactSession != nil {
			// Use dispatcher to send status change in correct protocol format
			// This routes to V3 or V5 handler based on the contact's protocol version
			_ = h.dispatcher.SendStatusChange(contactSession, session.UIN, newStatus)
		}
	}
}

// handleUsageStats processes usage statistics (0x0532)
// From iserverd v3_process_usagestats() - client sends usage data
func (h *V3Handler) handleUsageStats(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 usage stats", "uin", uin)

	return nil
}

// handleGetExternals processes get externals request (0x04C4)
// From iserverd v3_process_getext() - returns external services list
func (h *V3Handler) handleGetExternals(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 get externals", "uin", uin)

	// Send externals response (empty list)
	return h.sendExternals(session, seq2)
}

// handleSysAck processes system message acknowledgment (0x0442)
// From iserverd v3_process_sysack() - client acknowledges receipt of offline messages
// After receiving this, we delete the offline messages from the database
func (h *V3Handler) handleSysAck(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	ctx := context.Background()

	// Delete offline messages for this user
	if err := h.service.AckOfflineMessages(ctx, uin); err != nil {
		h.logger.Error("failed to delete offline messages", "uin", uin, "err", err)
	} else {
		h.logger.Debug("V3 offline messages deleted", "uin", uin)
	}

	return nil
}

// handleOnlineInfo processes reconnect/online info request (0x015E)
// From iserverd v3_process_onlineinfo()
func (h *V3Handler) handleOnlineInfo(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	_ = h.sendAck(session.Addr, seq1, seq2, uin)

	h.logger.Debug("V3 online info", "uin", uin)

	return nil
}

// handleGetInfo1 processes get basic info only request (0x0460)
// From iserverd v3_process_getinfo1() - sends only basic info (not full 5-packet set)
//
// Refactored to use service layer (GetUserInfoForProtocol) and packet builder.
// Following the OSCAR pattern: unmarshal -> call service -> build response
func (h *V3Handler) handleGetInfo1(session *LegacySession, seq1, seq2 uint16, uin uint32, data []byte) error {
	if session == nil {
		return nil
	}

	// 1. Send ACK using packet builder
	_ = h.sender.SendPacket(session.Addr, h.packetBuilder.BuildAck(seq1, seq2, uin))

	// 2. Unmarshal packet to extract target UIN
	// Format: TIMESTAMP(4) + TARGET_UIN(4)
	if len(data) < 8 {
		return nil
	}

	targetUIN := binary.LittleEndian.Uint32(data[4:8])

	h.logger.Debug("V3 get info1", "uin", uin, "target", targetUIN)

	// 3. Call service layer to get user info
	ctx := context.Background()
	info, err := h.service.GetUserInfoForProtocol(ctx, targetUIN)
	if err != nil {
		h.logger.Error("failed to get user info", "target", targetUIN, "err", err)
		// Still send minimal info packet even on error
		info = &UserInfoResult{
			UIN:      targetUIN,
			Nickname: fmt.Sprintf("%d", targetUIN),
		}
	}

	// 4. Build and send only basic info using packet builder
	// (unlike handleGetInfo which sends all 5 packets)
	return h.sender.SendToSession(session, h.packetBuilder.BuildBasicInfo(session.NextServerSeqNum(), seq2, session.UIN, info))
}

// sendNotes sends notes response (0x0352)
// From iserverd v3_send_notes()
func (h *V3Handler) sendNotes(session *LegacySession, seq2 uint16, targetUIN uint32, notes string) error {
	pktSize := 16 + 2 + len(notes) + 1 + 12 // header + notes + timestamps
	pkt := make([]byte, pktSize)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0x0352) // ICQ_CMDxSND_USERxNOTES
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], seq2)
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	// Notes (length-prefixed)
	binary.LittleEndian.PutUint16(pkt[offset:], uint16(len(notes)+1))
	offset += 2
	copy(pkt[offset:], notes)
	offset += len(notes)
	pkt[offset] = 0
	offset++

	// Timestamps: nupdate(4) + lastlogin(4) + ip_addr(4)
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	return h.sender.SendToSession(session, pkt[:offset])
}

// sendExternals sends externals list response (0x00B4)
// From iserverd v3_send_externals()
func (h *V3Handler) sendExternals(session *LegacySession, seq2 uint16) error {
	pkt := make([]byte, 20)
	offset := 0

	// Header
	binary.LittleEndian.PutUint16(pkt[offset:], ICQLegacyVersionV3)
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], 0x00B4) // ICQ_CMDxSND_USERxEXTERNALS
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], session.NextServerSeqNum())
	offset += 2
	binary.LittleEndian.PutUint16(pkt[offset:], seq2)
	offset += 2
	binary.LittleEndian.PutUint32(pkt[offset:], session.UIN)
	offset += 4
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	// Count = 0 (no externals)
	binary.LittleEndian.PutUint32(pkt[offset:], 0)
	offset += 4

	return h.sender.SendToSession(session, pkt[:offset])
}