// Package miot provides MIoT core client for Xiaomi Home devices.
// miot_lan.go — MIoT LAN device control, ported from py-miot/miot_lan.py.
//
// Only supports MIoT SPEC-v2 WiFi devices on the local network.
package miot

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/md5"
	"crypto/rand"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"math/big"
	"net"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"xiaomihome/logger"
)

// ============================================================================
// Protocol constants (aligned with Python _MIoTLanDevice / MIoTLan)
// ============================================================================

const (
	otHeader              = 0x2131
	otHeaderLen           = 32
	otPort                = 54321
	otProbeLen            = 32
	otMsgLen              = 1400
	otSupportWildcardSub  = 0xFE

	// Keep-alive intervals (seconds)
	kaIntervalMin     = 10.0
	kaIntervalMax     = 50.0
	fastPingInterval  = 5.0
	constructStatePending = 15.0

	// Network instability detection
	networkUnstableCntTh      = 10
	networkUnstableTimeTh     = 120.0
	networkUnstableResumeTh   = 300.0

	// Scan intervals (seconds)
	otProbeIntervalMin = 5.0
	otProbeIntervalMax = 45.0
)

// ============================================================================
// LanDeviceState — device keep-alive state machine
// ============================================================================

// LanDeviceState represents the keep-alive state of a LAN device.
type LanDeviceState int

const (
	LanDeviceFresh LanDeviceState = iota // 0 — just received a ping response
	LanDevicePing1                       // 1 — first fast ping attempt
	LanDevicePing2                       // 2 — second fast ping attempt
	LanDevicePing3                       // 3 — third fast ping attempt
	LanDeviceDead                        // 4 — device considered offline
)

// String returns a human-readable name.
func (s LanDeviceState) String() string {
	switch s {
	case LanDeviceFresh:
		return "fresh"
	case LanDevicePing1:
		return "ping1"
	case LanDevicePing2:
		return "ping2"
	case LanDevicePing3:
		return "ping3"
	case LanDeviceDead:
		return "dead"
	default:
		return "unknown"
	}
}

// ============================================================================
// LanDevice — single LAN device with encryption
// ============================================================================

// LanDevice manages the encrypted UDP communication and keep-alive for one
// MIoT SPEC-v2 WiFi device on the local network.
type LanDevice struct {
	DID       string
	Token     []byte
	IP        string
	IfName    string

	manager   *MIoTLan
	cipher    cipher.Block
	aesIV     []byte

	offset    int
	subscribed bool
	subTS     int
	supportedWildcardSub bool
	subLocked bool

	state  LanDeviceState
	online bool

	onlineHistory   []onlineEvent
	unstableTimer   *time.Timer

	kaTimer    *time.Timer
	kaInterval float64
}

type onlineEvent struct {
	ts     int
	online bool
}

// newLanDevice creates a new LanDevice and initializes its AES cipher.
func newLanDevice(mgr *MIoTLan, did, tokenHex, ip string) (*LanDevice, error) {
	token, err := hexDecode(tokenHex)
	if err != nil {
		return nil, fmt.Errorf("invalid token hex: %w", err)
	}
	if len(token) != 16 {
		return nil, fmt.Errorf("token must be 16 bytes (32 hex chars), got %d", len(token))
	}

	aesKey := md5Sum(token)
	aesIV := md5Sum(append(aesKey[:], token...))
	block, err := aes.NewCipher(aesKey[:])
	if err != nil {
		return nil, fmt.Errorf("create aes cipher: %w", err)
	}

	d := &LanDevice{
		DID:          did,
		Token:        token,
		IP:           ip,
		manager:      mgr,
		cipher:       block,
		aesIV:        aesIV[:],
		state:        LanDeviceDead,
		online:       false,
		kaInterval:   kaIntervalMin,
		onlineHistory: make([]onlineEvent, 0),
	}

	// Schedule initial keep-alive transition after a randomized delay.
	delay := randomizeFloat(constructStatePending, 0.5)
	d.kaTimer = time.AfterFunc(time.Duration(delay*float64(time.Second)), func() {
		d.updateKeepAlive(LanDeviceDead)
	})

	mgr.lgr.Infof("[lan] device added: did=%s", d.DID)
	return d, nil
}

// KeepAlive is called when a probe response is received from the device.
func (d *LanDevice) KeepAlive(ip, ifName string) {
	d.IP = ip
	if d.IfName != ifName {
		d.IfName = ifName
		d.manager.lgr.Infof("[lan] device if_name changed: %s, did=%s", d.IfName, d.DID)
	}
	d.updateKeepAlive(LanDeviceFresh)
}

// Online returns whether the device is currently considered online.
func (d *LanDevice) Online() bool {
	return d.online
}

// setOnline transitions the online state and broadcasts the change.
func (d *LanDevice) setOnline(v bool) {
	if d.online == v {
		return
	}
	d.online = v
	d.manager.broadcastDeviceState(d.DID, map[string]interface{}{
		"online":         d.online,
		"push_available": d.subscribed,
	})
}

// GenPacket encrypts a JSON message and writes the wire-format packet into out.
// Returns the number of bytes written.
// Wire format: [0x2131(2)][len(2)][did(8)][timestamp(4)][md5(16)] + encrypted_body
func (d *LanDevice) GenPacket(out []byte, msg map[string]interface{}) (int, error) {
	clearBytes, err := json.Marshal(msg)
	if err != nil {
		return 0, fmt.Errorf("marshal message: %w", err)
	}

	// PKCS7 padding
	blockSize := aes.BlockSize
	padding := blockSize - len(clearBytes)%blockSize
	padded := make([]byte, len(clearBytes)+padding)
	copy(padded, clearBytes)
	for i := len(clearBytes); i < len(padded); i++ {
		padded[i] = byte(padding)
	}

	if len(padded)+otHeaderLen > len(out) {
		return 0, fmt.Errorf("packet too long: %d > %d", len(padded)+otHeaderLen, len(out))
	}

	// Encrypt
	enc := cipher.NewCBCEncrypter(d.cipher, d.aesIV)
	enc.CryptBlocks(padded, padded)

	dataLen := len(padded) + otHeaderLen

	// Header (bytes 0-15)
	binary.BigEndian.PutUint16(out[0:2], otHeader)
	binary.BigEndian.PutUint16(out[2:4], uint16(dataLen))
	binary.BigEndian.PutUint64(out[4:12], mustParseUint64(d.DID))
	binary.BigEndian.PutUint32(out[12:16], uint32(int(time.Now().Unix())-d.offset))
	copy(out[16:32], d.Token)

	// Body
	copy(out[32:dataLen], padded)

	// MD5 over [0:dataLen]
	md5Hash := md5Sum(out[:dataLen])
	copy(out[16:32], md5Hash[:])

	return dataLen, nil
}

// DecryptPacket decrypts and authenticates a received packet.
func (d *LanDevice) DecryptPacket(data []byte) (map[string]interface{}, error) {
	if len(data) < otHeaderLen {
		return nil, fmt.Errorf("packet too short: %d", len(data))
	}

	dataLen := int(binary.BigEndian.Uint16(data[2:4]))
	if dataLen > len(data) {
		return nil, fmt.Errorf("declared len %d exceeds buffer %d", dataLen, len(data))
	}

	// Verify MD5
	origMD5 := make([]byte, 16)
	copy(origMD5, data[16:32])

	// Replace MD5 slot with token for verification
	saved := make([]byte, 16)
	copy(saved, data[16:32])
	copy(data[16:32], d.Token)

	calcMD5 := md5Sum(data[:dataLen])

	// Restore
	copy(data[16:32], saved)

	if string(origMD5) != string(calcMD5[:]) {
		return nil, fmt.Errorf("invalid md5")
	}

	// Decrypt
	encrypted := data[32:dataLen]
	if len(encrypted) == 0 {
		return nil, fmt.Errorf("empty payload")
	}

	dec := cipher.NewCBCDecrypter(d.cipher, d.aesIV)
	decrypted := make([]byte, len(encrypted))
	dec.CryptBlocks(decrypted, encrypted)

	// PKCS7 unpadding
	if len(decrypted) == 0 {
		return nil, fmt.Errorf("empty decrypted data")
	}
	paddingLen := int(decrypted[len(decrypted)-1])
	if paddingLen > aes.BlockSize || paddingLen == 0 || paddingLen > len(decrypted) {
		return nil, fmt.Errorf("invalid PKCS7 padding: %d", paddingLen)
	}
	decrypted = decrypted[:len(decrypted)-paddingLen]

	// Some devices add a trailing null byte
	decrypted = trimNull(decrypted)

	var msg map[string]interface{}
	if err := json.Unmarshal(decrypted, &msg); err != nil {
		return nil, fmt.Errorf("unmarshal decrypted: %w", err)
	}
	return msg, nil
}

// Subscribe sends a miIO.sub request to the device.
func (d *LanDevice) Subscribe() {
	if d.subLocked {
		return
	}
	d.subLocked = true
	defer func() { d.subLocked = false }()

	subTS := int(time.Now().Unix())
	d.manager.sendToDevice(d.DID, map[string]interface{}{
		"method": "miIO.sub",
		"params": map[string]interface{}{
			"version":    "2.0",
			"did":        d.manager.VirtualDID(),
			"update_ts":  subTS,
			"sub_method": ".",
		},
	}, func(msg map[string]interface{}, ctx interface{}) {
		d.subscribeHandler(msg, subTS)
	}, nil, 5000)
}

func (d *LanDevice) subscribeHandler(msg map[string]interface{}, subTS int) {
	result, _ := msg["result"].(map[string]interface{})
	if result == nil {
		d.manager.lgr.Infof("[lan] subscribe error: no result, did=%s, msg=%v", d.DID, msg)
		return
	}
	code, _ := result["code"].(float64)
	if code != 0 {
		d.manager.lgr.Infof("[lan] subscribe error: code=%v, did=%s, msg=%v", code, d.DID, msg)
		return
	}
	d.subscribed = true
	d.subTS = subTS
	d.manager.broadcastDeviceState(d.DID, map[string]interface{}{
		"online":         d.online,
		"push_available": d.subscribed,
	})
	d.manager.lgr.Infof("[lan] subscribe success: if=%s, did=%s", d.IfName, d.DID)
}

// Unsubscribe sends a miIO.unsub request to the device.
func (d *LanDevice) Unsubscribe() {
	if !d.subscribed {
		return
	}
	subTS := d.subTS
	d.manager.sendToDevice(d.DID, map[string]interface{}{
		"method": "miIO.unsub",
		"params": map[string]interface{}{
			"version":    "2.0",
			"did":        d.manager.VirtualDID(),
			"update_ts":  subTS,
			"sub_method": ".",
		},
	}, func(msg map[string]interface{}, ctx interface{}) {
		result, _ := msg["result"].(map[string]interface{})
		if result != nil {
			if code, _ := result["code"].(float64); code != 0 {
				d.manager.lgr.Infof("[lan] unsubscribe error: code=%v, did=%s, msg=%v", code, d.DID, msg)
				return
			}
		}
		d.manager.lgr.Infof("[lan] unsubscribe success: if=%s, did=%s", d.IfName, d.DID)
	}, nil, 5000)
	d.subscribed = false
	d.manager.broadcastDeviceState(d.DID, map[string]interface{}{
		"online":         d.online,
		"push_available": d.subscribed,
	})
}

// OnDelete cleans up timers when the device is removed.
func (d *LanDevice) OnDelete() {
	if d.kaTimer != nil {
		d.kaTimer.Stop()
		d.kaTimer = nil
	}
	if d.unstableTimer != nil {
		d.unstableTimer.Stop()
		d.unstableTimer = nil
	}
	d.manager.lgr.Infof("[lan] device deleted: did=%s", d.DID)
}

// UpdateInfo updates the device token if it has changed.
func (d *LanDevice) UpdateInfo(info map[string]interface{}) {
	tokenStr, ok := info["token"].(string)
	if !ok || len(tokenStr) != 32 {
		return
	}
	newToken, err := hexDecode(tokenStr)
	if err != nil {
		return
	}
	if strings.EqualFold(fmt.Sprintf("%x", d.Token), tokenStr) {
		return
	}
	// Token changed — recreate cipher
	d.Token = newToken
	aesKey := md5Sum(d.Token)
	aesIV := md5Sum(append(aesKey[:], d.Token...))
	block, err := aes.NewCipher(aesKey[:])
	if err != nil {
		d.manager.lgr.Infof("[lan] update token cipher error: %v, did=%s", err, d.DID)
		return
	}
	d.cipher = block
	d.aesIV = aesIV[:]
	d.manager.lgr.Infof("[lan] token updated: did=%s", d.DID)
}

// ============================================================================
// Keep-alive state machine
// ============================================================================

func (d *LanDevice) updateKeepAlive(state LanDeviceState) {
	lastState := d.state
	d.state = state

	if d.state != LanDeviceFresh {
		d.manager.lgr.Infof("[lan] device status: did=%s, state=%s", d.DID, d.state)
	}

	// Cancel existing timer
	if d.kaTimer != nil {
		d.kaTimer.Stop()
		d.kaTimer = nil
	}

	switch state {
	case LanDeviceFresh:
		if lastState == LanDeviceDead {
			d.kaInterval = kaIntervalMin
			d.changeOnline(true)
		}
		nextTimeout := d.nextKATimeout()
		d.kaTimer = time.AfterFunc(time.Duration(nextTimeout*float64(time.Second)), func() {
			d.updateKeepAlive(LanDevicePing1)
		})

	case LanDevicePing1, LanDevicePing2, LanDevicePing3:
		// Set timer first (matching Python's approach)
		nextState := LanDeviceState(int(state) + 1)
		d.kaTimer = time.AfterFunc(time.Duration(fastPingInterval*float64(time.Second)), func() {
			d.updateKeepAlive(nextState)
		})
		// Fast ping
		if d.IfName == "" {
				d.manager.lgr.Infof("[lan] if_name not set for device: did=%s", d.DID)
			return
		}
		if d.IP == "" {
			d.manager.lgr.Infof("[lan] ip not set for device: did=%s", d.DID)
			return
		}
		d.manager.ping(d.IfName, d.IP)

	case LanDeviceDead:
		if lastState == LanDevicePing3 {
			d.kaInterval = kaIntervalMin
			d.changeOnline(false)
		}
	}
}

func (d *LanDevice) nextKATimeout() float64 {
	d.kaInterval = minFloat(d.kaInterval*2, kaIntervalMax)
	return randomizeFloat(d.kaInterval, 0.1)
}

func (d *LanDevice) changeOnline(online bool) {
	d.manager.lgr.Infof("[lan] change online: did=%s, online=%v", d.DID, online)
	tsNow := int(time.Now().Unix())
	d.onlineHistory = append(d.onlineHistory, onlineEvent{ts: tsNow, online: online})
	if len(d.onlineHistory) > networkUnstableCntTh {
		d.onlineHistory = d.onlineHistory[1:]
	}

	if d.unstableTimer != nil {
		d.unstableTimer.Stop()
		d.unstableTimer = nil
	}

	if !online {
		d.setOnline(false)
	} else {
		if len(d.onlineHistory) < networkUnstableCntTh ||
			float64(tsNow-d.onlineHistory[0].ts) > networkUnstableTimeTh {
			d.setOnline(true)
		} else {
			d.manager.lgr.Infof("[lan] unstable device detected: did=%s", d.DID)
			d.unstableTimer = time.AfterFunc(time.Duration(networkUnstableResumeTh*float64(time.Second)), func() {
				d.manager.lgr.Infof("[lan] unstable resume threshold passed: did=%s", d.DID)
				d.setOnline(true)
			})
		}
	}
}

// ============================================================================
// MIoTLan — LAN device control manager
// ============================================================================

// MIoTLan manages MIoT LAN device discovery, communication, and subscriptions.
type MIoTLan struct {
	mu sync.Mutex

	netIFs      map[string]bool
	network     *MIoTNetwork
	mipsService *MipsService
	enableSub   bool
	virtualDID  string

	// UDP sockets per interface
	socks     map[string]*net.UDPConn
	localPort int

	// Devices
	devices map[string]*LanDevice

	// Message ID sequencing
	msgIDSeq    int32
	pendingReqs map[int]*pendingRequest

	// Subscriptions
	deviceStateSubs map[string]*deviceStateCallback
	matcher         *MIoTMatcher

	// Duplicate message filter
	replyBuf map[string]*time.Timer

	// Control
	stopCh   chan struct{}
	cmdCh    chan func()
	initDone bool
	initMu   sync.Mutex

	// Network state
	availableIFs    map[string]bool
	scanTimer       *time.Timer
	lastScanInterval float64

	// LAN state votes
	lanStateSubs map[string]func(bool)
	lanCtrlVotes map[string]bool

	// Profile models (loaded from YAML, models that should NOT use LAN control)
	profileModels map[string]bool

	lgr logger.Logger
}

type pendingRequest struct {
	msgID   int
	handler func(map[string]interface{}, interface{})
	ctx     interface{}
	timer   *time.Timer
}

type deviceStateCallback struct {
	key     string
	handler func(did string, state map[string]interface{}, ctx interface{})
	ctx     interface{}
}

// NewMIoTLan creates a new MIoTLan manager.
// netIFs: allowed network interface names (matched against MIoTNetwork).
// network: the MIoTNetwork monitor for interface change notifications.
// mipsService: the MipsService for central hub gateway detection.
func NewMIoTLan(netIFs []string, network *MIoTNetwork, mipsService *MipsService, enableSub bool, virtualDID int64) (*MIoTLan, error) {
	if network == nil {
		return nil, fmt.Errorf("network is required")
	}
	if mipsService == nil {
		return nil, fmt.Errorf("mipsService is required")
	}

	vDID := fmt.Sprintf("%d", virtualDID)
	if virtualDID == 0 {
		n, err := rand.Int(rand.Reader, big.NewInt(1<<62))
		if err != nil {
			return nil, fmt.Errorf("generate virtual did: %w", err)
		}
		vDID = fmt.Sprintf("%d", n.Uint64())
	}

	// Build probe message
	probe := make([]byte, otProbeLen)
	copy(probe[0:20], []byte("!1\x00\x20\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFFMDID"))
	binary.BigEndian.PutUint64(probe[20:28], mustParseUint64(vDID))
	// bytes 28:32 are zeros

	m := &MIoTLan{
		netIFs:          make(map[string]bool),
		network:         network,
		mipsService:     mipsService,
		enableSub:       enableSub,
		virtualDID:      vDID,
		socks:           make(map[string]*net.UDPConn),
		devices:         make(map[string]*LanDevice),
		msgIDSeq:        genMsgIDSeed(),
		pendingReqs:     make(map[int]*pendingRequest),
		deviceStateSubs: make(map[string]*deviceStateCallback),
		matcher:         NewMIoTMatcher(),
		replyBuf:        make(map[string]*time.Timer),
		stopCh:          make(chan struct{}),
		cmdCh:           make(chan func(), 64),
		availableIFs:    make(map[string]bool),
		lanStateSubs:    make(map[string]func(bool)),
		lanCtrlVotes:    make(map[string]bool),
		profileModels:   make(map[string]bool),
		lgr:             logger.Default(),
	}


	for _, ifName := range netIFs {
		m.netIFs[ifName] = true
	}

	// Subscribe to network interface changes
	network.SubNetworkInfo("miot_lan", m.onNetworkInfoChange)

	// Subscribe to mDNS service changes
	mipsService.SubServiceChange("miot_lan", "*", m.onMipsServiceChange)

	// Auto-init if no central hub gateway exists and we have interfaces
	if len(mipsService.GetServices("")) == 0 && len(netIFs) > 0 {
		m.lgr.Infof("[lan] no central hub gateway service, scheduling init")
		go func() {
			m.Init()
		}()
	}

	return m, nil
}

// SetLogger sets a custom logger for MIoTLan.
func (m *MIoTLan) SetLogger(l logger.Logger) { m.lgr = l }

// VirtualDID returns the virtual device ID used for LAN communication.
func (m *MIoTLan) VirtualDID() string {
	return m.virtualDID
}

// InitDone returns whether the LAN controller is initialized.
func (m *MIoTLan) InitDone() bool {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.initDone
}

// ============================================================================
// Init / Deinit
// ============================================================================

// Init starts the LAN controller. Safe to call multiple times.
func (m *MIoTLan) Init() {
	m.initMu.Lock()
	defer m.initMu.Unlock()

	m.mu.Lock()
	if m.initDone {
		m.mu.Unlock()
		m.lgr.Infof("[lan] already initialized")
		return
	}
	if len(m.netIFs) == 0 {
		m.mu.Unlock()
		m.lgr.Infof("[lan] no net_ifs configured")
		return
	}

	// Check if anyone voted for LAN control
	hasVote := false
	for _, v := range m.lanCtrlVotes {
		if v {
			hasVote = true
			break
		}
	}
	if !hasVote {
		m.mu.Unlock()
		m.lgr.Infof("[lan] no vote for lan ctrl")
		return
	}

	if len(m.mipsService.GetServices("")) > 0 {
		m.mu.Unlock()
		m.lgr.Infof("[lan] central hub gateway service exists, skip LAN init")
		return
	}

	// Build available interface set
	for ifName := range m.network.GetNetworkInfo() {
		m.availableIFs[ifName] = true
	}
	if len(m.availableIFs) == 0 {
		m.mu.Unlock()
		m.lgr.Infof("[lan] no available network interfaces")
		return
	}

	// Check that configured netIFs intersect with available IFs
	hasValid := false
	for ifName := range m.netIFs {
		if m.availableIFs[ifName] {
			hasValid = true
			break
		}
	}
	if !hasValid {
		m.mu.Unlock()
		m.lgr.Infof("[lan] no valid net_ifs matching configured list")
		return
	}

	m.mu.Unlock()

	// Start internal goroutine
	go m.internalLoop()

	m.mu.Lock()
	m.initDone = true
	m.mu.Unlock()

	// Notify LAN state subscribers
	m.mu.Lock()
	handlers := make([]func(bool), 0, len(m.lanStateSubs))
	for _, h := range m.lanStateSubs {
		handlers = append(handlers, h)
	}
	m.mu.Unlock()
	for _, h := range handlers {
		go h(true)
	}

	m.lgr.Infof("[lan] initialized: netIFs=%v, available=%v", m.netIFs, m.availableIFs)
}

// Deinit stops the LAN controller.
func (m *MIoTLan) Deinit() {
	m.initMu.Lock()
	defer m.initMu.Unlock()

	m.mu.Lock()
	if !m.initDone {
		m.mu.Unlock()
		m.lgr.Infof("[lan] not initialized")
		return
	}
	m.initDone = false
	m.mu.Unlock()

	// Signal the internal goroutine to stop
	m.cmdCh <- nil // sentinel: stop

	m.mu.Lock()
	// Clean up
	m.profileModels = make(map[string]bool)
	m.devices = make(map[string]*LanDevice)
	m.socks = make(map[string]*net.UDPConn)
	m.localPort = 0
	m.scanTimer = nil
	m.lastScanInterval = 0
	m.msgIDSeq = genMsgIDSeed()
	m.pendingReqs = make(map[int]*pendingRequest)
	m.matcher = NewMIoTMatcher()
	m.deviceStateSubs = make(map[string]*deviceStateCallback)
	m.replyBuf = make(map[string]*time.Timer)

	handlers := make([]func(bool), 0, len(m.lanStateSubs))
	for _, h := range m.lanStateSubs {
		handlers = append(handlers, h)
	}
	m.mu.Unlock()

	for _, h := range handlers {
		go h(false)
	}

	m.lgr.Infof("[lan] deinitialized")
}

// ============================================================================
// Internal loop (runs in a dedicated goroutine)
// ============================================================================

func (m *MIoTLan) internalLoop() {
	m.lgr.Infof("[lan] internal loop started")
	m.initSockets()

	// Start scan timer
	scanDelay := randomizeFloat(3.0, 1.0) // 0-6s random delay
	m.scanTimer = time.AfterFunc(time.Duration(scanDelay*float64(time.Second)), m.scanDevices)

	for {
		select {
		case cmd := <-m.cmdCh:
			if cmd == nil {
				// Stop signal
				m.deinitInternal()
				m.lgr.Infof("[lan] internal loop stopped")
				return
			}
			cmd()
		}
	}
}

func (m *MIoTLan) deinitInternal() {
	if m.scanTimer != nil {
		m.scanTimer.Stop()
		m.scanTimer = nil
	}
	for _, dev := range m.devices {
		dev.OnDelete()
	}
	m.devices = make(map[string]*LanDevice)

	for _, req := range m.pendingReqs {
		if req.timer != nil {
			req.timer.Stop()
		}
	}
	m.pendingReqs = make(map[int]*pendingRequest)

	for _, t := range m.replyBuf {
		t.Stop()
	}
	m.replyBuf = make(map[string]*time.Timer)

	m.deinitSockets()
}

// ============================================================================
// Socket management
// ============================================================================

func (m *MIoTLan) initSockets() {
	m.mu.Lock()
	defer m.mu.Unlock()

	m.deinitSocketsLocked()
	for ifName := range m.netIFs {
		if !m.availableIFs[ifName] {
			continue
		}
		m.createSocketLocked(ifName)
	}
}

func (m *MIoTLan) deinitSockets() {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.deinitSocketsLocked()
}

func (m *MIoTLan) deinitSocketsLocked() {
	for ifName := range m.socks {
		m.destroySocketLocked(ifName)
	}
	m.socks = make(map[string]*net.UDPConn)
}

func (m *MIoTLan) createSocketLocked(ifName string) {
	if _, ok := m.socks[ifName]; ok {
		return
	}

	// Get the interface IP from MIoTNetwork
	ni := m.network.GetNetworkInfo()
	info, ok := ni[ifName]
	if !ok || info.IP == "" {
		m.lgr.Infof("[lan] no IP for interface: %s", ifName)
		return
	}

	conn, err := createBoundSocket(info.IP, m.localPort)
	if err != nil {
		m.lgr.Infof("[lan] create socket error: if=%s, err=%v", ifName, err)
		return
	}

	m.socks[ifName] = conn
	if m.localPort == 0 {
		addr := conn.LocalAddr().(*net.UDPAddr)
		m.localPort = addr.Port
	}

	// Start reader goroutine for this socket
	go m.socketReader(ifName, conn)

	m.lgr.Infof("[lan] socket created: if=%s, ip=%s, port=%d", ifName, info.IP, m.localPort)
}

func (m *MIoTLan) destroySocketLocked(ifName string) {
	conn, ok := m.socks[ifName]
	if !ok {
		return
	}
	delete(m.socks, ifName)
	conn.Close()
	m.lgr.Infof("[lan] socket destroyed: if=%s", ifName)
}

// createBoundSocket creates a UDP socket bound to a specific IP address.
func createBoundSocket(ip string, port int) (*net.UDPConn, error) {
	addr := &net.UDPAddr{
		IP:   net.ParseIP(ip),
		Port: port,
	}
	return net.ListenUDP("udp4", addr)
}

// socketReader reads from a UDP socket and dispatches raw messages.
func (m *MIoTLan) socketReader(ifName string, conn *net.UDPConn) {
	buf := make([]byte, otMsgLen)
	for {
		n, remoteAddr, err := conn.ReadFromUDP(buf)
		if err != nil {
			// Socket closed or error
			return
		}
		if n <= 0 {
			continue
		}
		if remoteAddr.Port != otPort {
			continue
		}
		m.handleRawMessage(buf[:n], n, remoteAddr.IP.String(), ifName)
	}
}

// ============================================================================
// Sending
// ============================================================================

// send broadcasts a probe/data to all or a specific interface.
func (m *MIoTLan) send(ifName, targetIP string, data []byte) {
	m.mu.Lock()
	defer m.mu.Unlock()

	if ifName == "" {
		// Broadcast to all sockets
		for ifn, conn := range m.socks {
			conn.WriteToUDP(data, &net.UDPAddr{IP: net.ParseIP(targetIP), Port: otPort})
			_ = ifn
		}
	} else {
		conn, ok := m.socks[ifName]
		if !ok {
			m.lgr.Infof("[lan] invalid socket: if=%s", ifName)
			return
		}
		conn.WriteToUDP(data, &net.UDPAddr{IP: net.ParseIP(targetIP), Port: otPort})
	}
}

func (m *MIoTLan) ping(ifName, targetIP string) {
	if targetIP == "" {
		return
	}
	m.send(ifName, targetIP, m.buildProbe())
}

func (m *MIoTLan) buildProbe() []byte {
	probe := make([]byte, otProbeLen)
	binary.BigEndian.PutUint16(probe[0:2], otHeader)
	binary.BigEndian.PutUint16(probe[2:4], otProbeLen)
	binary.BigEndian.PutUint64(probe[4:12], mustParseUint64(m.virtualDID))
	// timestamp at 12:16
	binary.BigEndian.PutUint32(probe[12:16], uint32(time.Now().Unix()))
	// bytes 16:32 remain zero (will be filled by receiver md5)
	return probe
}

// sendToDevice sends an encrypted message to a specific device.
func (m *MIoTLan) sendToDevice(did string, msg map[string]interface{}, handler func(map[string]interface{}, interface{}), ctx interface{}, timeoutMs int) {
	m.mu.Lock()
	dev, ok := m.devices[did]
	m.mu.Unlock()

	if !ok {
		if handler != nil {
			go handler(map[string]interface{}{
				"code":  CodeInternalError,
				"error": "device not found",
			}, ctx)
		}
		return
	}
	if dev.cipher == nil {
		if handler != nil {
			go handler(map[string]interface{}{
				"code":  CodeInternalError,
				"error": "device cipher not initialized",
			}, ctx)
		}
		return
	}
	if dev.IfName == "" || dev.IP == "" {
		if handler != nil {
			go handler(map[string]interface{}{
				"code":  CodeInternalError,
				"error": "device network info missing",
			}, ctx)
		}
		return
	}

	msgID := m.genMsgID()
	msg["id"] = msgID

	out := make([]byte, otMsgLen)
	dataLen, err := dev.GenPacket(out, msg)
	if err != nil {
		if handler != nil {
			go handler(map[string]interface{}{
				"code":  CodeInternalError,
				"error": err.Error(),
			}, ctx)
		}
		return
	}

	m.makeRequest(msgID, out[:dataLen], dev.IfName, dev.IP, handler, ctx, timeoutMs)
}

func (m *MIoTLan) makeRequest(msgID int, data []byte, ifName, ip string, handler func(map[string]interface{}, interface{}), ctx interface{}, timeoutMs int) {
	req := &pendingRequest{
		msgID:   msgID,
		handler: handler,
		ctx:     ctx,
	}

	if timeoutMs > 0 && handler != nil {
		req.timer = time.AfterFunc(time.Duration(timeoutMs)*time.Millisecond, func() {
			m.mu.Lock()
			if _, ok := m.pendingReqs[msgID]; ok {
				delete(m.pendingReqs, msgID)
				m.mu.Unlock()
				handler(map[string]interface{}{
					"code":  CodeTimeout,
					"error": "timeout",
				}, ctx)
			} else {
				m.mu.Unlock()
			}
		})
	}

	m.mu.Lock()
	m.pendingReqs[msgID] = req
	m.mu.Unlock()

	m.send(ifName, ip, data)
}

// ============================================================================
// Message ID generation
// ============================================================================

func (m *MIoTLan) genMsgID() int {
	for {
		id := int(atomic.AddInt32(&m.msgIDSeq, 1))
		if id > 0x80000000 {
			atomic.StoreInt32(&m.msgIDSeq, 1)
			continue
		}
		return id
	}
}

func genMsgIDSeed() int32 {
	n, _ := rand.Int(rand.Reader, big.NewInt(0x7FFFFFFF))
	return int32(n.Int64())
}

// ============================================================================
// Raw message handling
// ============================================================================

func (m *MIoTLan) handleRawMessage(data []byte, dataLen int, ip, ifName string) {
	if dataLen < 4 || binary.BigEndian.Uint16(data[0:2]) != otHeader {
		return
	}

	did := fmt.Sprintf("%d", binary.BigEndian.Uint64(data[4:12]))

	m.mu.Lock()
	dev, ok := m.devices[did]
	m.mu.Unlock()

	if !ok {
		return
	}

	// Update clock offset
	if dataLen >= 16 {
		timestamp := binary.BigEndian.Uint32(data[12:16])
		dev.offset = int(time.Now().Unix()) - int(timestamp)
	}

	// Keep alive on probe or if subscribed
	if dataLen == otProbeLen || dev.subscribed {
		dev.KeepAlive(ip, ifName)
	}

	// Check for subscription handshake in probe
	if m.enableSub && dataLen == otProbeLen && dataLen >= 29 {
		if string(data[16:20]) == "MSUB" && string(data[24:27]) == "PUB" {
			dev.supportedWildcardSub = data[28] == otSupportWildcardSub
			subTS := int(binary.BigEndian.Uint32(data[20:24]))
			subType := data[27]
			if dev.supportedWildcardSub && (subType == 0 || subType == 1 || subType == 4) && subTS != dev.subTS {
				dev.subscribed = false
				dev.Subscribe()
			}
		}
	}

	// Decrypt and handle device messages
	if dataLen > otProbeLen {
		msg, err := dev.DecryptPacket(data[:dataLen])
		if err != nil {
			m.lgr.Infof("[lan] decrypt error: did=%s, err=%v", did, err)
			return
		}
		m.handleMessage(did, msg)
	}
}

func (m *MIoTLan) handleMessage(did string, msg map[string]interface{}) {
	msgID, ok := msg["id"]
	if !ok {
		m.lgr.Infof("[lan] message without id: did=%s, msg=%v", did, msg)
		return
	}
	id, ok := toInt(msgID)
	if !ok {
		return
	}

	// Check if this is a reply to a pending request
	m.mu.Lock()
	req, ok := m.pendingReqs[id]
	if ok {
		delete(m.pendingReqs, id)
	}
	m.mu.Unlock()

	if ok {
		if req.timer != nil {
			req.timer.Stop()
		}
		if req.handler != nil {
			go req.handler(msg, req.ctx)
		}
		return
	}

	// Uplink message — check for method
	method, ok := msg["method"].(string)
	if !ok {
		return
	}

	// Filter duplicate messages
	if m.filterDup(did, id) {
		m.sendToDevice(did, map[string]interface{}{
			"id":     id,
			"result": map[string]interface{}{"code": 0},
		}, nil, nil, 0)
		return
	}

	m.lgr.Infof("[lan] message: did=%s, method=%s", did, method)

	switch method {
	case "properties_changed":
		params, _ := msg["params"].([]interface{})
		for _, p := range params {
			param, ok := p.(map[string]interface{})
			if !ok {
				continue
			}
			siid, _ := param["siid"]
			piid, _ := param["piid"]
			if siid == nil || piid == nil {
				continue
			}
			key := fmt.Sprintf("%s/p/%v/%v", did, siid, piid)
			for _, entry := range m.matcher.Match(key) {
				if entry.Handler != nil {
					go entry.Handler(param, entry.Ctx)
				}
			}
		}
	case "event_occured":
		params, _ := msg["params"].(map[string]interface{})
		if params != nil {
			siid, _ := params["siid"]
			eiid, _ := params["eiid"]
			if siid != nil && eiid != nil {
				key := fmt.Sprintf("%s/e/%v/%v", did, siid, eiid)
				for _, entry := range m.matcher.Match(key) {
					if entry.Handler != nil {
						go entry.Handler(params, entry.Ctx)
					}
				}
			}
		}
	}

	// Acknowledge
	m.sendToDevice(did, map[string]interface{}{
		"id":     id,
		"result": map[string]interface{}{"code": 0},
	}, nil, nil, 0)
}

func (m *MIoTLan) filterDup(did string, msgID int) bool {
	m.mu.Lock()
	defer m.mu.Unlock()

	filterID := fmt.Sprintf("%s.%d", did, msgID)
	if _, ok := m.replyBuf[filterID]; ok {
		return true
	}
	m.replyBuf[filterID] = time.AfterFunc(5*time.Second, func() {
		m.mu.Lock()
		delete(m.replyBuf, filterID)
		m.mu.Unlock()
	})
	return false
}

// ============================================================================
// Device management (internal loop commands)
// ============================================================================

// broadcastDeviceState sends device state to all subscribers.
func (m *MIoTLan) broadcastDeviceState(did string, state map[string]interface{}) {
	m.mu.Lock()
	callbacks := make([]*deviceStateCallback, 0, len(m.deviceStateSubs))
	for _, cb := range m.deviceStateSubs {
		callbacks = append(callbacks, cb)
	}
	m.mu.Unlock()

	for _, cb := range callbacks {
		if cb.handler != nil {
			go cb.handler(did, state, cb.ctx)
		}
	}
}

// ============================================================================
// Scan devices
// ============================================================================

func (m *MIoTLan) scanDevices() {
	if m.scanTimer != nil {
		m.scanTimer.Stop()
		m.scanTimer = nil
	}

	m.send("", "255.255.255.255", m.buildProbe())

	scanTime := m.nextScanTime()
	m.scanTimer = time.AfterFunc(time.Duration(scanTime*float64(time.Second)), m.scanDevices)
	m.lgr.Infof("[lan] next scan in %.0fs", scanTime)
}

func (m *MIoTLan) nextScanTime() float64 {
	if m.lastScanInterval == 0 {
		m.lastScanInterval = otProbeIntervalMin
	}
	m.lastScanInterval = minFloat(m.lastScanInterval*2, otProbeIntervalMax)
	return m.lastScanInterval
}

// ============================================================================
// Network interface change handler
// ============================================================================

func (m *MIoTLan) onNetworkInfoChange(status InterfaceStatus, info *NetworkInfo) {
	m.lgr.Infof("[lan] network info change: status=%s, if=%s", status, info.Name)

	m.mu.Lock()
	// Rebuild available IFs
	m.availableIFs = make(map[string]bool)
	for ifName := range m.network.GetNetworkInfo() {
		m.availableIFs[ifName] = true
	}

	if len(m.availableIFs) == 0 {
		m.mu.Unlock()
		go m.Deinit()
		return
	}

	valid := false
	for ifName := range m.netIFs {
		if m.availableIFs[ifName] {
			valid = true
			break
		}
	}
	if !valid {
		m.mu.Unlock()
		m.lgr.Infof("[lan] no valid net_ifs after change")
		go m.Deinit()
		return
	}

	if !m.initDone {
		m.mu.Unlock()
		go m.Init()
		return
	}
	m.mu.Unlock()

	// Send command to internal loop
	m.cmdCh <- func() {
		switch status {
		case InterfaceAdd:
			m.mu.Lock()
			m.availableIFs[info.Name] = true
			if m.netIFs[info.Name] {
				m.createSocketLocked(info.Name)
			}
			m.mu.Unlock()
		case InterfaceRemove:
			m.mu.Lock()
			delete(m.availableIFs, info.Name)
			m.destroySocketLocked(info.Name)
			m.mu.Unlock()
		}
	}
}

// ============================================================================
// mDNS service change handler
// ============================================================================

func (m *MIoTLan) onMipsServiceChange(groupID string, state MipsServiceState, data map[string]interface{}) {
	m.lgr.Infof("[lan] mips service change: groupID=%s, state=%s, data=%v", groupID, state, data)
	if len(m.mipsService.GetServices("")) > 0 {
		m.lgr.Infof("[lan] central hub gateway found, deinit LAN")
		go m.Deinit()
	} else {
		m.lgr.Infof("[lan] no central hub gateway, init LAN")
		go m.Init()
	}
}

// ============================================================================
// Public API
// ============================================================================

// VoteForLanCtrl votes for or against LAN control.
func (m *MIoTLan) VoteForLanCtrl(key string, vote bool) {
	m.lgr.Infof("[lan] vote for lan ctrl: key=%s, vote=%v", key, vote)
	m.mu.Lock()
	m.lanCtrlVotes[key] = vote
	hasVote := false
	for _, v := range m.lanCtrlVotes {
		if v {
			hasVote = true
			break
		}
	}
	m.mu.Unlock()

	if !hasVote {
		go m.Deinit()
	} else {
		go m.Init()
	}
}

// UpdateSubscribeOption enables or disables device subscriptions.
func (m *MIoTLan) UpdateSubscribeOption(enable bool) {
	m.lgr.Infof("[lan] update subscribe option: %v", enable)
	m.mu.Lock()
	oldEnable := m.enableSub
	m.enableSub = enable
	m.mu.Unlock()

	if oldEnable && !enable {
		// Unsubscribe all devices
		m.cmdCh <- func() {
			m.mu.Lock()
			defer m.mu.Unlock()
			for _, dev := range m.devices {
				dev.Unsubscribe()
			}
		}
	}
}

// UpdateDevices registers or updates devices.
func (m *MIoTLan) UpdateDevices(devices map[string]map[string]interface{}) {
	if !m.InitDone() {
		return
	}
	m.cmdCh <- func() {
		m.mu.Lock()
		defer m.mu.Unlock()

		for did, info := range devices {
			if !isNumeric(did) {
				m.lgr.Infof("[lan] invalid did (non-numeric): %s", did)
				continue
			}
			model, _ := info["model"].(string)
			if model != "" && m.profileModels[model] {
				m.lgr.Infof("[lan] model not supported for LAN ctrl: did=%s, model=%s", did, model)
				continue
			}
			if existing, ok := m.devices[did]; ok {
				existing.UpdateInfo(info)
			} else {
				tokenStr, _ := info["token"].(string)
				if len(tokenStr) != 32 {
					m.lgr.Infof("[lan] invalid token for device: did=%s", did)
					continue
				}
				ip, _ := info["ip"].(string)
				dev, err := newLanDevice(m, did, tokenStr, ip)
				if err != nil {
					m.lgr.Infof("[lan] create device error: did=%s, err=%v", did, err)
					continue
				}
				m.devices[did] = dev
			}
		}
	}
}

// DeleteDevices removes devices from LAN management.
func (m *MIoTLan) DeleteDevices(dids []string) {
	if !m.InitDone() {
		return
	}
	m.cmdCh <- func() {
		m.mu.Lock()
		defer m.mu.Unlock()
		for _, did := range dids {
			if dev, ok := m.devices[did]; ok {
				dev.OnDelete()
				delete(m.devices, did)
			}
		}
	}
}

// SubLanState subscribes to LAN controller state changes (init/deinit).
func (m *MIoTLan) SubLanState(key string, handler func(bool)) {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.lanStateSubs[key] = handler
}

// UnsubLanState unsubscribes from LAN controller state changes.
func (m *MIoTLan) UnsubLanState(key string) {
	m.mu.Lock()
	defer m.mu.Unlock()
	delete(m.lanStateSubs, key)
}

// SubDeviceState subscribes to device online/offline state changes.
func (m *MIoTLan) SubDeviceState(key string, handler func(did string, state map[string]interface{}, ctx interface{}), ctx interface{}) {
	m.cmdCh <- func() {
		m.mu.Lock()
		defer m.mu.Unlock()
		m.deviceStateSubs[key] = &deviceStateCallback{key: key, handler: handler, ctx: ctx}
	}
}

// UnsubDeviceState unsubscribes from device state changes.
func (m *MIoTLan) UnsubDeviceState(key string) {
	m.cmdCh <- func() {
		m.mu.Lock()
		defer m.mu.Unlock()
		delete(m.deviceStateSubs, key)
	}
}

// SubProp subscribes to property change broadcasts for a device.
func (m *MIoTLan) SubProp(did string, handler func(map[string]interface{}, interface{}), siid, piid int, ctx interface{}) {
	key := fmt.Sprintf("%s/p/#", did)
	if siid > 0 && piid > 0 {
		key = fmt.Sprintf("%s/p/%d/%d", did, siid, piid)
	}
	m.cmdCh <- func() {
		m.matcher.Sub(key, handler, ctx)
		m.lgr.Infof("[lan] sub prop: key=%s", key)
	}
}

// UnsubProp unsubscribes from property change broadcasts.
func (m *MIoTLan) UnsubProp(did string, siid, piid int) {
	key := fmt.Sprintf("%s/p/#", did)
	if siid > 0 && piid > 0 {
		key = fmt.Sprintf("%s/p/%d/%d", did, siid, piid)
	}
	m.cmdCh <- func() {
		m.matcher.Unsub(key)
		m.lgr.Infof("[lan] unsub prop: key=%s", key)
	}
}

// SubEvent subscribes to event broadcasts for a device.
func (m *MIoTLan) SubEvent(did string, handler func(map[string]interface{}, interface{}), siid, eiid int, ctx interface{}) {
	key := fmt.Sprintf("%s/e/#", did)
	if siid > 0 && eiid > 0 {
		key = fmt.Sprintf("%s/e/%d/%d", did, siid, eiid)
	}
	m.cmdCh <- func() {
		m.matcher.Sub(key, handler, ctx)
		m.lgr.Infof("[lan] sub event: key=%s", key)
	}
}

// UnsubEvent unsubscribes from event broadcasts.
func (m *MIoTLan) UnsubEvent(did string, siid, eiid int) {
	key := fmt.Sprintf("%s/e/#", did)
	if siid > 0 && eiid > 0 {
		key = fmt.Sprintf("%s/e/%d/%d", did, siid, eiid)
	}
	m.cmdCh <- func() {
		m.matcher.Unsub(key)
		m.lgr.Infof("[lan] unsub event: key=%s", key)
	}
}

// GetDevList returns the list of online devices and their push availability.
func (m *MIoTLan) GetDevList() map[string]map[string]interface{} {
	m.mu.Lock()
	defer m.mu.Unlock()

	result := make(map[string]map[string]interface{})
	for _, dev := range m.devices {
		if dev.online {
			result[dev.DID] = map[string]interface{}{
				"online":         dev.online,
				"push_available": dev.subscribed,
			}
		}
	}
	return result
}

// GetProps retrieves device properties in batch via LAN.
// Sends encrypted UDP requests to each device.
func (m *MIoTLan) GetProps(params []PropParam) ([]PropResult, error) {
	results := make([]PropResult, 0, len(params))
	resultCh := make(chan PropResult, len(params))

	var wg sync.WaitGroup
	for _, p := range params {
		wg.Add(1)
		go func(param PropParam) {
			defer wg.Done()
			resultCh <- m.getPropSingle(param)
		}(p)
	}
	wg.Wait()
	close(resultCh)

	for r := range resultCh {
		results = append(results, r)
	}
	return results, nil
}

// getPropSingle fetches a single property from a LAN device.
func (m *MIoTLan) getPropSingle(param PropParam) PropResult {
	m.mu.Lock()
	dev, ok := m.devices[param.DID]
	m.mu.Unlock()

	if !ok || dev.cipher == nil {
		return PropResult{
			DID:  param.DID,
			Siid: param.Siid,
			Piid: param.Piid,
			Code: CodeInternalError,
		}
	}

	msg := map[string]interface{}{
		"method": "properties/get",
		"params": []interface{}{
			map[string]interface{}{
				"did":  param.DID,
				"siid": param.Siid,
				"piid": param.Piid,
			},
		},
	}

	resultCh := make(chan PropResult, 1)
	m.sendToDevice(param.DID, msg, func(resp map[string]interface{}, ctx interface{}) {
		code, _ := resp["code"].(float64)
		r := PropResult{
			DID:  param.DID,
			Siid: param.Siid,
			Piid: param.Piid,
			Code: int(code),
		}
		if result, ok := resp["result"].(map[string]interface{}); ok {
			r.Value = result["value"]
		}
		select {
		case resultCh <- r:
		default:
		}
	}, nil, 5000)

	select {
	case r := <-resultCh:
		return r
	case <-time.After(6 * time.Second):
		return PropResult{
			DID:  param.DID,
			Siid: param.Siid,
			Piid: param.Piid,
			Code: CodeTimeout,
		}
	}
}

// ============================================================================
// Crypto helpers
// ============================================================================

// md5Sum computes the MD5 hash of data and returns the 16-byte result.
func md5Sum(data []byte) [16]byte {
	return md5.Sum(data)
}

// hexDecode decodes a hex string to bytes.
func hexDecode(s string) ([]byte, error) {
	// Use fmt.Sscanf-style approach
	dst := make([]byte, len(s)/2)
	for i := 0; i < len(s); i += 2 {
		var b byte
		_, err := fmt.Sscanf(s[i:i+2], "%02x", &b)
		if err != nil {
			return nil, fmt.Errorf("invalid hex at position %d: %s", i, s[i:i+2])
		}
		dst[i/2] = b
	}
	return dst, nil
}

// ============================================================================
// Math / utility helpers
// ============================================================================

func minFloat(a, b float64) float64 {
	if a < b {
		return a
	}
	return b
}

func randomizeFloat(value, ratio float64) float64 {
	return value * (1 - ratio + randFloat()*2*ratio)
}

func randFloat() float64 {
	n, _ := rand.Int(rand.Reader, big.NewInt(1<<53))
	return float64(n.Int64()) / float64(1<<53)
}

func mustParseUint64(s string) uint64 {
	var v uint64
	fmt.Sscanf(s, "%d", &v)
	return v
}

func toInt(v interface{}) (int, bool) {
	switch n := v.(type) {
	case float64:
		return int(n), true
	case int:
		return n, true
	case int64:
		return int(n), true
	case json.Number:
		i, err := n.Int64()
		if err != nil {
			return 0, false
		}
		return int(i), true
	}
	return 0, false
}

func isNumeric(s string) bool {
	for _, c := range s {
		if c < '0' || c > '9' {
			return false
		}
	}
	return len(s) > 0
}

func trimNull(b []byte) []byte {
	for len(b) > 0 && b[len(b)-1] == 0 {
		b = b[:len(b)-1]
	}
	return b
}