Protocol/stream/stream.go

package stream

import (
	"encoding/binary"
	"fmt"
	"sync"
	"sync/atomic"
	"time"

	"git.sharkk.net/EQ2/Protocol/crypto"
	"git.sharkk.net/EQ2/Protocol/opcodes"
	"git.sharkk.net/EQ2/Protocol/packets"
	"github.com/panjf2000/gnet/v2"
)

// Stream implements EQ2's reliable UDP protocol
type Stream struct {
	conn gnet.Conn
	mu   sync.RWMutex

	// Connection state
	state     atomic.Value // StreamState
	sessionID uint32
	crcKey    uint32
	maxLen    uint16
	encodeKey int
	decodeKey int

	// Sequence management
	seqOut      uint16
	seqIn       uint16
	seqLastAck  uint16
	seqExpected uint16

	// Acknowledgment tracking
	pendingAcks  map[uint16]*pendingPacket
	ackTimer     *time.Timer
	lastAckSent  time.Time
	ackThreshold time.Duration
	ackQueue     []uint16 // Sequences needing ACK

	// Fragment assembly
	fragments  map[uint16]*fragmentBuffer
	nextFragID uint16

	// Out of order handling
	outOfOrder map[uint16][]byte

	// Packet queues
	reliableQueue   []*packets.ProtoPacket
	unreliableQueue []*packets.ProtoPacket
	resendQueue     []*pendingPacket

	// Opcode management
	opcodeManager opcodes.Manager
	opcodeSize    uint8

	// Cipher for encryption
	cipher *crypto.Ciphers

	// Timers
	keepAliveTimer *time.Timer
	timeoutTimer   *time.Timer

	// Retransmission settings
	rtt        time.Duration
	rttVar     time.Duration
	rto        time.Duration
	minRTO     time.Duration
	maxRTO     time.Duration
	maxRetries int

	// Stats
	packetsOut  uint64
	packetsIn   uint64
	bytesOut    uint64
	bytesIn     uint64
	retransmits uint64

	// Callbacks
	onPacket     func(*packets.AppPacket)
	onDisconnect func()
}

type pendingPacket struct {
	packet    *packets.ProtoPacket
	seq       uint16
	sentTime  time.Time
	attempts  int
	nextRetry time.Time
}

type fragmentBuffer struct {
	totalSize uint32
	chunks    map[uint16][]byte
	received  uint32
	startTime time.Time
}

type StreamState int

const (
	StateDisconnected StreamState = iota
	StateConnecting
	StateEstablished
	StateClosing
	StateClosed
)

// Config holds stream configuration
type Config struct {
	SessionID       uint32
	CRCKey          uint32
	MaxPacketSize   uint16
	EncodeKey       int
	DecodeKey       int
	OpcodeManager   opcodes.Manager
	OpcodeSize      uint8
	AckThreshold    time.Duration
	KeepaliveTime   time.Duration
	TimeoutDuration time.Duration
}

// NewStream creates a new EQStream instance
func NewStream(conn gnet.Conn, cfg *Config) *Stream {
	s := &Stream{
		conn:          conn,
		sessionID:     cfg.SessionID,
		crcKey:        cfg.CRCKey,
		maxLen:        cfg.MaxPacketSize,
		encodeKey:     cfg.EncodeKey,
		decodeKey:     cfg.DecodeKey,
		opcodeManager: cfg.OpcodeManager,
		opcodeSize:    cfg.OpcodeSize,
		ackThreshold:  cfg.AckThreshold,
		pendingAcks:   make(map[uint16]*pendingPacket),
		fragments:     make(map[uint16]*fragmentBuffer),
		outOfOrder:    make(map[uint16][]byte),
		ackQueue:      make([]uint16, 0),
		seqOut:        0,
		seqIn:         0,
		seqExpected:   0,
		rtt:           time.Second,
		rttVar:        500 * time.Millisecond,
		rto:           time.Second,
		minRTO:        200 * time.Millisecond,
		maxRTO:        10 * time.Second,
		maxRetries:    10,
	}

	if s.maxLen == 0 {
		s.maxLen = packets.DefaultMTU
	}
	if s.ackThreshold == 0 {
		s.ackThreshold = 200 * time.Millisecond
	}

	s.state.Store(StateDisconnected)

	// Initialize cipher if keys provided
	if cfg.EncodeKey != 0 || cfg.DecodeKey != 0 {
		cipher, _ := crypto.NewCiphers(int64(cfg.EncodeKey))
		s.cipher = cipher
	}

	// Start keepalive timer
	if cfg.KeepaliveTime > 0 {
		s.keepAliveTimer = time.AfterFunc(cfg.KeepaliveTime, s.sendKeepalive)
	}

	// Start timeout timer
	if cfg.TimeoutDuration > 0 {
		s.timeoutTimer = time.AfterFunc(cfg.TimeoutDuration, s.handleTimeout)
	}

	return s
}

// Process handles incoming data from gnet
func (s *Stream) Process(data []byte) error {
	// Validate CRC
	if len(data) < 2 {
		return nil
	}

	// Check for CRC (last 2 bytes)
	if len(data) > 2 {
		providedCRC := binary.BigEndian.Uint16(data[len(data)-2:])
		calculatedCRC := crypto.CalculateCRC(data[:len(data)-2], s.crcKey)
		if providedCRC != calculatedCRC {
			return nil // Drop packet with bad CRC
		}
		data = data[:len(data)-2] // Strip CRC
	}

	// Decrypt if needed
	if s.cipher != nil {
		s.cipher.Decrypt(data)
	}

	// Parse protocol opcode
	if len(data) < 2 {
		return nil
	}
	opcode := binary.BigEndian.Uint16(data[:2])

	switch opcode {
	case opcodes.OP_SessionRequest:
		return s.handleSessionRequest(data[2:])
	case opcodes.OP_SessionResponse:
		return s.handleSessionResponse(data[2:])
	case opcodes.OP_Packet:
		return s.handlePacket(data[2:])
	case opcodes.OP_Fragment:
		return s.handleFragment(data[2:])
	case opcodes.OP_Ack:
		return s.handleAck(data[2:])
	case opcodes.OP_Combined:
		return s.handleCombined(data[2:])
	case opcodes.OP_AppCombined:
		return s.handleAppCombined(data[2:])
	case opcodes.OP_KeepAlive:
		s.resetTimeout()
		return nil
	case opcodes.OP_SessionDisconnect:
		return s.handleDisconnect()
	case opcodes.OP_OutOfOrderAck:
		return s.handleOutOfOrderAck(data[2:])
	}

	atomic.AddUint64(&s.packetsIn, 1)
	atomic.AddUint64(&s.bytesIn, uint64(len(data)))

	return nil
}

// handleSessionRequest processes session establishment request
func (s *Stream) handleSessionRequest(data []byte) error {
	if len(data) < 10 {
		return fmt.Errorf("session request too small")
	}

	// Parse session request
	// Format: version(4) + sessionID(4) + maxLen(2)
	version := binary.BigEndian.Uint32(data[:4])
	sessionID := binary.BigEndian.Uint32(data[4:8])
	maxLen := binary.BigEndian.Uint16(data[8:10])

	// Update session info
	s.mu.Lock()
	s.sessionID = sessionID
	if maxLen < s.maxLen {
		s.maxLen = maxLen // Use smaller of the two
	}
	s.mu.Unlock()

	// Send session response
	response := make([]byte, 14)
	binary.BigEndian.PutUint32(response[0:4], sessionID)
	binary.BigEndian.PutUint32(response[4:8], s.crcKey)
	response[8] = 2 // Encoding type
	binary.BigEndian.PutUint16(response[9:11], s.maxLen)
	binary.BigEndian.PutUint32(response[11:15], version)

	s.state.Store(StateEstablished)
	return s.sendRaw(opcodes.OP_SessionResponse, response)
}

// handleSessionResponse processes session establishment response
func (s *Stream) handleSessionResponse(data []byte) error {
	if len(data) < 14 {
		return fmt.Errorf("session response too small")
	}

	// Parse response
	sessionID := binary.BigEndian.Uint32(data[0:4])
	crcKey := binary.BigEndian.Uint32(data[4:8])
	// encodingType := data[8]
	maxLen := binary.BigEndian.Uint16(data[9:11])

	s.mu.Lock()
	s.sessionID = sessionID
	s.crcKey = crcKey
	if maxLen < s.maxLen {
		s.maxLen = maxLen
	}
	s.mu.Unlock()

	s.state.Store(StateEstablished)
	return nil
}

// handlePacket processes reliable packets
func (s *Stream) handlePacket(data []byte) error {
	if len(data) < 2 {
		return nil
	}

	seq := binary.BigEndian.Uint16(data[:2])
	data = data[2:]

	s.mu.Lock()
	defer s.mu.Unlock()

	// Check if this is the expected sequence
	if seq == s.seqExpected {
		// Process in-order packet
		s.seqExpected++
		s.ackQueue = append(s.ackQueue, seq)

		// Process packet data
		if err := s.processPacketData(data); err != nil {
			return err
		}

		// Check for buffered out-of-order packets
		for {
			if buffered, exists := s.outOfOrder[s.seqExpected]; exists {
				delete(s.outOfOrder, s.seqExpected)
				s.ackQueue = append(s.ackQueue, s.seqExpected)
				s.seqExpected++
				if err := s.processPacketData(buffered); err != nil {
					return err
				}
			} else {
				break
			}
		}
	} else if seq > s.seqExpected {
		// Out of order - buffer it
		s.outOfOrder[seq] = append([]byte(nil), data...)
		// Send out-of-order ACK
		go s.sendOutOfOrderAck(seq)
	} else {
		// Duplicate packet - just ACK it
		go s.sendAckImmediate(seq)
	}

	// Schedule grouped ACK
	s.scheduleAck()

	return nil
}

// handleFragment assembles fragmented packets
func (s *Stream) handleFragment(data []byte) error {
	if len(data) < 10 {
		return nil
	}

	seq := binary.BigEndian.Uint16(data[:2])
	fragID := binary.BigEndian.Uint32(data[2:6])
	fragTotal := binary.BigEndian.Uint16(data[6:8])
	fragCur := binary.BigEndian.Uint16(data[8:10])
	data = data[10:]

	s.mu.Lock()
	defer s.mu.Unlock()

	// Get or create fragment buffer
	frag, exists := s.fragments[uint16(fragID)]
	if !exists {
		frag = &fragmentBuffer{
			totalSize: uint32(fragTotal),
			chunks:    make(map[uint16][]byte),
			startTime: time.Now(),
		}
		s.fragments[uint16(fragID)] = frag
	}

	// Store chunk
	frag.chunks[fragCur] = append([]byte(nil), data...)
	frag.received++

	// Check if complete
	if frag.received == uint32(fragTotal) {
		// Reassemble in order
		complete := make([]byte, 0)
		for i := uint16(0); i < fragTotal; i++ {
			if chunk, ok := frag.chunks[i]; ok {
				complete = append(complete, chunk...)
			} else {
				// Missing chunk - wait for retransmit
				return nil
			}
		}
		delete(s.fragments, uint16(fragID))

		// Process reassembled packet
		return s.processPacketData(complete)
	}

	// ACK the fragment
	s.ackQueue = append(s.ackQueue, seq)
	s.scheduleAck()

	return nil
}

// handleAck processes acknowledgments
func (s *Stream) handleAck(data []byte) error {
	if len(data) < 2 {
		return nil
	}

	ackSeq := binary.BigEndian.Uint16(data[:2])

	s.mu.Lock()
	defer s.mu.Unlock()

	// Remove from pending and update RTT
	if pending, exists := s.pendingAcks[ackSeq]; exists {
		delete(s.pendingAcks, ackSeq)

		// Update RTT estimates (TCP-like algorithm)
		sample := time.Since(pending.sentTime)
		if s.rtt == 0 {
			s.rtt = sample
			s.rttVar = sample / 2
		} else {
			alpha := 0.125
			beta := 0.25
			s.rttVar = time.Duration((1-beta)*float64(s.rttVar) + beta*float64(absTime(s.rtt-sample)))
			s.rtt = time.Duration((1-alpha)*float64(s.rtt) + alpha*float64(sample))
		}
		s.rto = s.rtt + 4*s.rttVar
		if s.rto < s.minRTO {
			s.rto = s.minRTO
		}
		if s.rto > s.maxRTO {
			s.rto = s.maxRTO
		}
	}

	// Fast retransmit: if ACK is higher than pending packets, trigger retransmit
	if ackSeq > s.seqLastAck {
		s.seqLastAck = ackSeq

		// Check for gaps that need immediate retransmit
		for seq, pending := range s.pendingAcks {
			if seq < ackSeq {
				// This packet was likely lost, retransmit immediately
				s.resendQueue = append(s.resendQueue, pending)
			}
		}
	}

	return nil
}

// handleOutOfOrderAck handles out-of-order acknowledgments
func (s *Stream) handleOutOfOrderAck(data []byte) error {
	if len(data) < 2 {
		return nil
	}

	seq := binary.BigEndian.Uint16(data[:2])

	s.mu.Lock()
	defer s.mu.Unlock()

	// Immediately retransmit if we have this packet pending
	if pending, exists := s.pendingAcks[seq]; exists {
		s.resendQueue = append(s.resendQueue, pending)
	}

	return nil
}

// handleCombined processes combined protocol packets
func (s *Stream) handleCombined(data []byte) error {
	pos := 0

	for pos < len(data) {
		if pos+1 > len(data) {
			break
		}

		// Read packet size
		size := uint16(data[pos])
		pos++

		// Check for oversized marker
		if size == 0xff {
			if pos+2 > len(data) {
				break
			}
			size = binary.BigEndian.Uint16(data[pos : pos+2])
			pos += 2
		}

		// Extract packet
		if pos+int(size) > len(data) {
			break
		}

		packet := data[pos : pos+int(size)]
		pos += int(size)

		// Process each sub-packet
		if err := s.Process(packet); err != nil {
			return err
		}
	}

	return nil
}

// handleAppCombined processes combined application packets
func (s *Stream) handleAppCombined(data []byte) error {
	pos := 0

	for pos < len(data) {
		if pos+1 > len(data) {
			break
		}

		// Read packet size
		size := uint16(data[pos])
		pos++

		// Check for oversized marker
		if size == 0xff {
			if pos+2 > len(data) {
				break
			}
			size = binary.BigEndian.Uint16(data[pos : pos+2])
			pos += 2
		}

		// Extract packet
		if pos+int(size) > len(data) {
			break
		}

		packet := data[pos : pos+int(size)]
		pos += int(size)

		// Process as application packet
		if err := s.processPacketData(packet); err != nil {
			return err
		}
	}

	return nil
}

// SendPacket sends an application packet
func (s *Stream) SendPacket(app *packets.AppPacket) error {
	// Check state
	if s.state.Load() != StateEstablished {
		return fmt.Errorf("stream not established")
	}

	// Convert to protocol packet
	proto := s.appToProto(app)

	// Check if needs fragmentation
	if proto.Size() > uint32(s.maxLen-10) { // Reserve space for headers
		return s.sendFragmented(proto)
	}

	// Add to appropriate queue based on reliability
	s.mu.Lock()
	if app.Priority > packets.PriorityNormal {
		s.reliableQueue = append(s.reliableQueue, proto)
	} else {
		s.unreliableQueue = append(s.unreliableQueue, proto)
	}
	s.mu.Unlock()

	// Process queues
	return s.processQueues()
}

// sendFragmented fragments and sends large packets
func (s *Stream) sendFragmented(proto *packets.ProtoPacket) error {
	data := make([]byte, proto.Size())
	proto.Serialize(data, 0)

	// Calculate fragment size (leave room for headers)
	fragSize := int(s.maxLen) - 12 // Fragment header is 10 bytes + 2 for protocol
	numFrags := (len(data) + fragSize - 1) / fragSize

	if numFrags > 0xFFFF {
		return fmt.Errorf("packet too large to fragment")
	}

	s.mu.Lock()
	fragID := s.nextFragID
	s.nextFragID++
	s.mu.Unlock()

	// Send each fragment
	for i := 0; i < numFrags; i++ {
		start := i * fragSize
		end := start + fragSize
		if end > len(data) {
			end = len(data)
		}

		// Build fragment header
		fragHeader := make([]byte, 10)
		// Sequence added by sendReliable
		binary.BigEndian.PutUint32(fragHeader[0:4], uint32(fragID))
		binary.BigEndian.PutUint16(fragHeader[4:6], uint16(numFrags))
		binary.BigEndian.PutUint16(fragHeader[6:8], uint16(i))
		binary.BigEndian.PutUint16(fragHeader[8:10], uint16(end-start))

		// Combine header and data
		fragment := append(fragHeader, data[start:end]...)

		// Send as reliable packet
		fragProto := packets.NewProtoPacket(opcodes.OP_Fragment, fragment, s.opcodeManager)
		if err := s.sendReliable(fragProto); err != nil {
			return err
		}
	}

	return nil
}

// sendReliable sends a reliable packet with sequence number
func (s *Stream) sendReliable(proto *packets.ProtoPacket) error {
	s.mu.Lock()
	seq := s.seqOut
	s.seqOut++
	s.mu.Unlock()

	// Build packet with sequence
	data := make([]byte, proto.Size()+2)
	binary.BigEndian.PutUint16(data[:2], seq)
	proto.Serialize(data[2:], 0)

	// Track for retransmission
	pending := &pendingPacket{
		packet:    proto.Copy(),
		seq:       seq,
		sentTime:  time.Now(),
		attempts:  1,
		nextRetry: time.Now().Add(s.rto),
	}

	s.mu.Lock()
	s.pendingAcks[seq] = pending
	s.mu.Unlock()

	// Send with protocol header
	return s.sendRaw(opcodes.OP_Packet, data)
}

// processQueues processes all packet queues
func (s *Stream) processQueues() error {
	s.mu.Lock()

	// Process resends first (highest priority)
	for len(s.resendQueue) > 0 {
		pending := s.resendQueue[0]
		s.resendQueue = s.resendQueue[1:]

		if time.Now().After(pending.nextRetry) {
			s.mu.Unlock()

			// Rebuild packet
			data := make([]byte, pending.packet.Size()+2)
			binary.BigEndian.PutUint16(data[:2], pending.seq)
			pending.packet.Serialize(data[2:], 0)

			// Update pending info
			pending.attempts++
			pending.sentTime = time.Now()
			pending.nextRetry = time.Now().Add(s.rto * time.Duration(pending.attempts))

			// Check max retries
			if pending.attempts > s.maxRetries {
				s.mu.Lock()
				delete(s.pendingAcks, pending.seq)
				s.mu.Unlock()
				// Connection likely dead
				s.handleTimeout()
				return fmt.Errorf("max retransmissions exceeded")
			}

			atomic.AddUint64(&s.retransmits, 1)
			s.sendRaw(opcodes.OP_Packet, data)

			s.mu.Lock()
		} else {
			// Not time yet, re-queue
			s.resendQueue = append(s.resendQueue, pending)
		}
	}

	// Process reliable queue
	for len(s.reliableQueue) > 0 {
		proto := s.reliableQueue[0]
		s.reliableQueue = s.reliableQueue[1:]
		s.mu.Unlock()

		if err := s.sendReliable(proto); err != nil {
			return err
		}

		s.mu.Lock()
	}

	// Process unreliable queue
	for len(s.unreliableQueue) > 0 {
		proto := s.unreliableQueue[0]
		s.unreliableQueue = s.unreliableQueue[1:]
		s.mu.Unlock()

		// Send unreliable (no sequence/retransmit)
		data := make([]byte, proto.Size())
		proto.Serialize(data, 0)
		s.sendRaw(proto.Opcode, data)

		s.mu.Lock()
	}

	// Check for retransmissions needed
	now := time.Now()
	for _, pending := range s.pendingAcks {
		if now.After(pending.nextRetry) {
			s.resendQueue = append(s.resendQueue, pending)
		}
	}

	s.mu.Unlock()

	// Process any pending ACKs
	s.sendPendingAcks()

	return nil
}

// Helper methods

func (s *Stream) processPacketData(data []byte) error {
	// Create ProtoPacket from raw data
	proto := packets.NewProtoPacketFromRaw(data, -1, s.opcodeManager)

	// Decompress if needed
	if err := proto.DecompressPacket(); err != nil {
		return err
	}

	// Convert to AppPacket
	app := proto.MakeApplicationPacket(s.opcodeSize)

	// Deliver to callback
	if s.onPacket != nil {
		go s.onPacket(app)
	}

	return nil
}

func (s *Stream) scheduleAck() {
	if s.ackTimer == nil {
		s.ackTimer = time.AfterFunc(s.ackThreshold, func() {
			s.sendPendingAcks()
		})
	}
}

func (s *Stream) sendPendingAcks() {
	s.mu.Lock()
	if len(s.ackQueue) == 0 {
		s.mu.Unlock()
		return
	}

	// Send all pending ACKs
	for _, seq := range s.ackQueue {
		data := make([]byte, 2)
		binary.BigEndian.PutUint16(data, seq)
		s.sendRaw(opcodes.OP_Ack, data)
	}

	s.ackQueue = s.ackQueue[:0]
	s.lastAckSent = time.Now()
	s.mu.Unlock()
}

func (s *Stream) sendAckImmediate(seq uint16) error {
	data := make([]byte, 2)
	binary.BigEndian.PutUint16(data, seq)
	return s.sendRaw(opcodes.OP_Ack, data)
}

func (s *Stream) sendOutOfOrderAck(seq uint16) error {
	data := make([]byte, 2)
	binary.BigEndian.PutUint16(data, seq)
	return s.sendRaw(opcodes.OP_OutOfOrderAck, data)
}

func (s *Stream) sendKeepalive() {
	if s.state.Load() == StateEstablished {
		s.sendRaw(opcodes.OP_KeepAlive, nil)
	}
	// Reschedule
	if s.keepAliveTimer != nil {
		s.keepAliveTimer.Reset(10 * time.Second)
	}
}

func (s *Stream) resetTimeout() {
	if s.timeoutTimer != nil {
		s.timeoutTimer.Reset(30 * time.Second)
	}
}

func (s *Stream) handleTimeout() {
	s.state.Store(StateClosed)
	if s.onDisconnect != nil {
		s.onDisconnect()
	}
}

func (s *Stream) handleDisconnect() error {
	s.state.Store(StateClosed)
	if s.onDisconnect != nil {
		go s.onDisconnect()
	}
	return nil
}

// sendRaw sends raw data with protocol opcode
func (s *Stream) sendRaw(opcode uint16, data []byte) error {
	// Build packet: opcode + data + CRC
	packet := make([]byte, 2+len(data)+2)
	binary.BigEndian.PutUint16(packet[:2], opcode)
	copy(packet[2:], data)

	// Add CRC
	crc := crypto.CalculateCRC(packet[:len(packet)-2], s.crcKey)
	binary.BigEndian.PutUint16(packet[len(packet)-2:], crc)

	// Encrypt if needed
	if s.cipher != nil {
		s.cipher.Encrypt(packet)
	}

	// Send via gnet
	atomic.AddUint64(&s.packetsOut, 1)
	atomic.AddUint64(&s.bytesOut, uint64(len(packet)))

	return s.conn.AsyncWrite(packet, nil)
}

func (s *Stream) appToProto(app *packets.AppPacket) *packets.ProtoPacket {
	proto := packets.NewProtoPacket(app.Opcode, app.Buffer, s.opcodeManager)
	proto.CopyInfo(app.Packet)
	proto.CompressThreshold = 100
	proto.EncodeKey = s.encodeKey
	return proto
}

// Public methods

// SetPacketCallback sets the callback for received packets
func (s *Stream) SetPacketCallback(fn func(*packets.AppPacket)) {
	s.onPacket = fn
}

// SetDisconnectCallback sets the callback for disconnection
func (s *Stream) SetDisconnectCallback(fn func()) {
	s.onDisconnect = fn
}

// GetState returns current stream state
func (s *Stream) GetState() StreamState {
	return s.state.Load().(StreamState)
}

// IsConnected returns true if stream is established
func (s *Stream) IsConnected() bool {
	return s.GetState() == StateEstablished
}

// SendSessionRequest initiates client connection
func (s *Stream) SendSessionRequest() error {
	// Build session request packet
	// Format: version(4) + sessionID(4) + maxLen(2)
	data := make([]byte, 10)
	binary.BigEndian.PutUint32(data[0:4], 2) // Protocol version
	binary.BigEndian.PutUint32(data[4:8], s.sessionID)
	binary.BigEndian.PutUint16(data[8:10], s.maxLen)

	s.state.Store(StateConnecting)
	return s.sendRaw(opcodes.OP_SessionRequest, data)
}

// validateSession checks if packet belongs to this session
func (s *Stream) validateSession(sessionID uint32) bool {
	if s.sessionID == 0 {
		// Not yet established, accept any
		return true
	}
	if sessionID != s.sessionID {
		// Wrong session - send out of session response
		go s.sendRaw(opcodes.OP_OutOfSession, nil)
		return false
	}
	return true
}

// GetSessionID returns current session ID
func (s *Stream) GetSessionID() uint32 {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.sessionID
}

// SetSessionID sets the session ID (for client mode)
func (s *Stream) SetSessionID(id uint32) {
	s.mu.Lock()
	s.sessionID = id
	s.mu.Unlock()
}

// GetRemoteAddr returns remote address
func (s *Stream) GetRemoteAddr() string {
	if s.conn != nil {
		return s.conn.RemoteAddr().String()
	}
	return ""
}

// Close closes the stream
func (s *Stream) Close() error {
	if s.state.Load() == StateClosed {
		return nil
	}

	s.state.Store(StateClosed)

	// Send disconnect
	s.sendRaw(opcodes.OP_SessionDisconnect, nil)

	// Clean up timers
	if s.keepAliveTimer != nil {
		s.keepAliveTimer.Stop()
	}
	if s.ackTimer != nil {
		s.ackTimer.Stop()
	}
	if s.timeoutTimer != nil {
		s.timeoutTimer.Stop()
	}

	// Clear queues
	s.mu.Lock()
	s.reliableQueue = nil
	s.unreliableQueue = nil
	s.resendQueue = nil
	s.pendingAcks = nil
	s.fragments = nil
	s.outOfOrder = nil
	s.mu.Unlock()

	return nil
}

// Utility functions

func absTime(d time.Duration) time.Duration {
	if d < 0 {
		return -d
	}
	return d
}