mqtt-packet/writeToStream.js

const protocol = require('./constants')
const empty = Buffer.allocUnsafe(0)
const zeroBuf = Buffer.from([0])
const numbers = require('./numbers')
const nextTick = require('process-nextick-args').nextTick
const debug = require('debug')('mqtt-packet:writeToStream')

const numCache = numbers.cache
const generateNumber = numbers.generateNumber
const generateCache = numbers.generateCache
const genBufVariableByteInt = numbers.genBufVariableByteInt
const generate4ByteBuffer = numbers.generate4ByteBuffer
let writeNumber = writeNumberCached
let toGenerate = true

function generate (packet, stream, opts) {
  debug('generate called')
  if (stream.cork) {
    stream.cork()
    nextTick(uncork, stream)
  }

  if (toGenerate) {
    toGenerate = false
    generateCache()
  }
  debug('generate: packet.cmd: %s', packet.cmd)
  switch (packet.cmd) {
    case 'connect':
      return connect(packet, stream, opts)
    case 'connack':
      return connack(packet, stream, opts)
    case 'publish':
      return publish(packet, stream, opts)
    case 'puback':
    case 'pubrec':
    case 'pubrel':
    case 'pubcomp':
      return confirmation(packet, stream, opts)
    case 'subscribe':
      return subscribe(packet, stream, opts)
    case 'suback':
      return suback(packet, stream, opts)
    case 'unsubscribe':
      return unsubscribe(packet, stream, opts)
    case 'unsuback':
      return unsuback(packet, stream, opts)
    case 'pingreq':
    case 'pingresp':
      return emptyPacket(packet, stream, opts)
    case 'disconnect':
      return disconnect(packet, stream, opts)
    case 'auth':
      return auth(packet, stream, opts)
    default:
      stream.emit('error', new Error('Unknown command'))
      return false
  }
}
/**
 * Controls numbers cache.
 * Set to "false" to allocate buffers on-the-flight instead of pre-generated cache
 */
Object.defineProperty(generate, 'cacheNumbers', {
  get () {
    return writeNumber === writeNumberCached
  },
  set (value) {
    if (value) {
      if (!numCache || Object.keys(numCache).length === 0) toGenerate = true
      writeNumber = writeNumberCached
    } else {
      toGenerate = false
      writeNumber = writeNumberGenerated
    }
  }
})

function uncork (stream) {
  stream.uncork()
}

function connect (packet, stream, opts) {
  const settings = packet || {}
  const protocolId = settings.protocolId || 'MQTT'
  let protocolVersion = settings.protocolVersion || 4
  const will = settings.will
  let clean = settings.clean
  const keepalive = settings.keepalive || 0
  const clientId = settings.clientId || ''
  const username = settings.username
  const password = settings.password
  /* mqtt5 new oprions */
  const properties = settings.properties

  if (clean === undefined) clean = true

  let length = 0

  // Must be a string and non-falsy
  if (!protocolId ||
     (typeof protocolId !== 'string' && !Buffer.isBuffer(protocolId))) {
    stream.emit('error', new Error('Invalid protocolId'))
    return false
  } else length += protocolId.length + 2

  // Must be 3 or 4 or 5
  if (protocolVersion !== 3 && protocolVersion !== 4 && protocolVersion !== 5) {
    stream.emit('error', new Error('Invalid protocol version'))
    return false
  } else length += 1

  // ClientId might be omitted in 3.1.1 and 5, but only if cleanSession is set to 1
  if ((typeof clientId === 'string' || Buffer.isBuffer(clientId)) &&
     (clientId || protocolVersion >= 4) && (clientId || clean)) {
    length += Buffer.byteLength(clientId) + 2
  } else {
    if (protocolVersion < 4) {
      stream.emit('error', new Error('clientId must be supplied before 3.1.1'))
      return false
    }
    if ((clean * 1) === 0) {
      stream.emit('error', new Error('clientId must be given if cleanSession set to 0'))
      return false
    }
  }

  // Must be a two byte number
  if (typeof keepalive !== 'number' ||
      keepalive < 0 ||
      keepalive > 65535 ||
      keepalive % 1 !== 0) {
    stream.emit('error', new Error('Invalid keepalive'))
    return false
  } else length += 2

  // Connect flags
  length += 1

  let propertiesData
  let willProperties

  // Properties
  if (protocolVersion === 5) {
    propertiesData = getProperties(stream, properties)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // If will exists...
  if (will) {
    // It must be an object
    if (typeof will !== 'object') {
      stream.emit('error', new Error('Invalid will'))
      return false
    }
    // It must have topic typeof string
    if (!will.topic || typeof will.topic !== 'string') {
      stream.emit('error', new Error('Invalid will topic'))
      return false
    } else {
      length += Buffer.byteLength(will.topic) + 2
    }

    // Payload
    length += 2 // payload length
    if (will.payload) {
      if (will.payload.length >= 0) {
        if (typeof will.payload === 'string') {
          length += Buffer.byteLength(will.payload)
        } else {
          length += will.payload.length
        }
      } else {
        stream.emit('error', new Error('Invalid will payload'))
        return false
      }
    }
    // will properties
    willProperties = {}
    if (protocolVersion === 5) {
      willProperties = getProperties(stream, will.properties)
      if (!willProperties) { return false }
      length += willProperties.length
    }
  }

  // Username
  let providedUsername = false
  if (username != null) {
    if (isStringOrBuffer(username)) {
      providedUsername = true
      length += Buffer.byteLength(username) + 2
    } else {
      stream.emit('error', new Error('Invalid username'))
      return false
    }
  }

  // Password
  if (password != null) {
    if (!providedUsername) {
      stream.emit('error', new Error('Username is required to use password'))
      return false
    }

    if (isStringOrBuffer(password)) {
      length += byteLength(password) + 2
    } else {
      stream.emit('error', new Error('Invalid password'))
      return false
    }
  }

  // Generate header
  stream.write(protocol.CONNECT_HEADER)

  // Generate length
  writeVarByteInt(stream, length)

  // Generate protocol ID
  writeStringOrBuffer(stream, protocolId)

  if (settings.bridgeMode) {
    protocolVersion += 128
  }

  stream.write(
    protocolVersion === 131
      ? protocol.VERSION131
      : protocolVersion === 132
        ? protocol.VERSION132
        : protocolVersion === 4
          ? protocol.VERSION4
          : protocolVersion === 5
            ? protocol.VERSION5
            : protocol.VERSION3
  )

  // Connect flags
  let flags = 0
  flags |= (username != null) ? protocol.USERNAME_MASK : 0
  flags |= (password != null) ? protocol.PASSWORD_MASK : 0
  flags |= (will && will.retain) ? protocol.WILL_RETAIN_MASK : 0
  flags |= (will && will.qos) ? will.qos << protocol.WILL_QOS_SHIFT : 0
  flags |= will ? protocol.WILL_FLAG_MASK : 0
  flags |= clean ? protocol.CLEAN_SESSION_MASK : 0

  stream.write(Buffer.from([flags]))

  // Keepalive
  writeNumber(stream, keepalive)

  // Properties
  if (protocolVersion === 5) {
    propertiesData.write()
  }

  // Client ID
  writeStringOrBuffer(stream, clientId)

  // Will
  if (will) {
    if (protocolVersion === 5) {
      willProperties.write()
    }
    writeString(stream, will.topic)
    writeStringOrBuffer(stream, will.payload)
  }

  // Username and password
  if (username != null) {
    writeStringOrBuffer(stream, username)
  }
  if (password != null) {
    writeStringOrBuffer(stream, password)
  }
  // This is a small packet that happens only once on a stream
  // We assume the stream is always free to receive more data after this
  return true
}

function connack (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const rc = version === 5 ? settings.reasonCode : settings.returnCode
  const properties = settings.properties
  let length = 2 // length of rc and sessionHeader

  // Check return code
  if (typeof rc !== 'number') {
    stream.emit('error', new Error('Invalid return code'))
    return false
  }
  // mqtt5 properties
  let propertiesData = null
  if (version === 5) {
    propertiesData = getProperties(stream, properties)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  stream.write(protocol.CONNACK_HEADER)
  // length
  writeVarByteInt(stream, length)
  stream.write(settings.sessionPresent ? protocol.SESSIONPRESENT_HEADER : zeroBuf)

  stream.write(Buffer.from([rc]))
  if (propertiesData != null) {
    propertiesData.write()
  }
  return true
}

function publish (packet, stream, opts) {
  debug('publish: packet: %o', packet)
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const qos = settings.qos || 0
  const retain = settings.retain ? protocol.RETAIN_MASK : 0
  const topic = settings.topic
  const payload = settings.payload || empty
  const id = settings.messageId
  const properties = settings.properties

  let length = 0

  // Topic must be a non-empty string or Buffer
  if (typeof topic === 'string') length += Buffer.byteLength(topic) + 2
  else if (Buffer.isBuffer(topic)) length += topic.length + 2
  else {
    stream.emit('error', new Error('Invalid topic'))
    return false
  }

  // Get the payload length
  if (!Buffer.isBuffer(payload)) length += Buffer.byteLength(payload)
  else length += payload.length

  // Message ID must a number if qos > 0
  if (qos && typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  } else if (qos) length += 2

  // mqtt5 properties
  let propertiesData = null
  if (version === 5) {
    propertiesData = getProperties(stream, properties)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // Header
  stream.write(protocol.PUBLISH_HEADER[qos][settings.dup ? 1 : 0][retain ? 1 : 0])

  // Remaining length
  writeVarByteInt(stream, length)

  // Topic
  writeNumber(stream, byteLength(topic))
  stream.write(topic)

  // Message ID
  if (qos > 0) writeNumber(stream, id)

  // Properties
  if (propertiesData != null) {
    propertiesData.write()
  }

  // Payload
  debug('publish: payload: %o', payload)
  return stream.write(payload)
}

/* Puback, pubrec, pubrel and pubcomp */
function confirmation (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const type = settings.cmd || 'puback'
  const id = settings.messageId
  const dup = (settings.dup && type === 'pubrel') ? protocol.DUP_MASK : 0
  let qos = 0
  const reasonCode = settings.reasonCode
  const properties = settings.properties
  let length = version === 5 ? 3 : 2

  if (type === 'pubrel') qos = 1

  // Check message ID
  if (typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  }

  // properies mqtt 5
  let propertiesData = null
  if (version === 5) {
    // Confirm should not add empty property length with no properties (rfc 3.4.2.2.1)
    if (typeof properties === 'object') {
      propertiesData = getPropertiesByMaximumPacketSize(stream, properties, opts, length)
      if (!propertiesData) { return false }
      length += propertiesData.length
    }
  }

  // Header
  stream.write(protocol.ACKS[type][qos][dup][0])

  // Length
  writeVarByteInt(stream, length)

  // Message ID
  writeNumber(stream, id)

  // reason code in header
  if (version === 5) {
    stream.write(Buffer.from([reasonCode]))
  }

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }
  return true
}

function subscribe (packet, stream, opts) {
  debug('subscribe: packet: ')
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const dup = settings.dup ? protocol.DUP_MASK : 0
  const id = settings.messageId
  const subs = settings.subscriptions
  const properties = settings.properties

  let length = 0

  // Check message ID
  if (typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  } else length += 2

  // properies mqtt 5
  let propertiesData = null
  if (version === 5) {
    propertiesData = getProperties(stream, properties)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // Check subscriptions
  if (typeof subs === 'object' && subs.length) {
    for (let i = 0; i < subs.length; i += 1) {
      const itopic = subs[i].topic
      const iqos = subs[i].qos

      if (typeof itopic !== 'string') {
        stream.emit('error', new Error('Invalid subscriptions - invalid topic'))
        return false
      }
      if (typeof iqos !== 'number') {
        stream.emit('error', new Error('Invalid subscriptions - invalid qos'))
        return false
      }

      if (version === 5) {
        const nl = subs[i].nl || false
        if (typeof nl !== 'boolean') {
          stream.emit('error', new Error('Invalid subscriptions - invalid No Local'))
          return false
        }
        const rap = subs[i].rap || false
        if (typeof rap !== 'boolean') {
          stream.emit('error', new Error('Invalid subscriptions - invalid Retain as Published'))
          return false
        }
        const rh = subs[i].rh || 0
        if (typeof rh !== 'number' || rh > 2) {
          stream.emit('error', new Error('Invalid subscriptions - invalid Retain Handling'))
          return false
        }
      }

      length += Buffer.byteLength(itopic) + 2 + 1
    }
  } else {
    stream.emit('error', new Error('Invalid subscriptions'))
    return false
  }

  // Generate header
  debug('subscribe: writing to stream: %o', protocol.SUBSCRIBE_HEADER)
  stream.write(protocol.SUBSCRIBE_HEADER[1][dup ? 1 : 0][0])

  // Generate length
  writeVarByteInt(stream, length)

  // Generate message ID
  writeNumber(stream, id)

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }

  let result = true

  // Generate subs
  for (const sub of subs) {
    const jtopic = sub.topic
    const jqos = sub.qos
    const jnl = +sub.nl
    const jrap = +sub.rap
    const jrh = sub.rh
    let joptions

    // Write topic string
    writeString(stream, jtopic)

    // options process
    joptions = protocol.SUBSCRIBE_OPTIONS_QOS[jqos]
    if (version === 5) {
      joptions |= jnl ? protocol.SUBSCRIBE_OPTIONS_NL : 0
      joptions |= jrap ? protocol.SUBSCRIBE_OPTIONS_RAP : 0
      joptions |= jrh ? protocol.SUBSCRIBE_OPTIONS_RH[jrh] : 0
    }
    // Write options
    result = stream.write(Buffer.from([joptions]))
  }

  return result
}

function suback (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const id = settings.messageId
  const granted = settings.granted
  const properties = settings.properties
  let length = 0

  // Check message ID
  if (typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  } else length += 2

  // Check granted qos vector
  if (typeof granted === 'object' && granted.length) {
    for (let i = 0; i < granted.length; i += 1) {
      if (typeof granted[i] !== 'number') {
        stream.emit('error', new Error('Invalid qos vector'))
        return false
      }
      length += 1
    }
  } else {
    stream.emit('error', new Error('Invalid qos vector'))
    return false
  }

  // properies mqtt 5
  let propertiesData = null
  if (version === 5) {
    propertiesData = getPropertiesByMaximumPacketSize(stream, properties, opts, length)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // header
  stream.write(protocol.SUBACK_HEADER)

  // Length
  writeVarByteInt(stream, length)

  // Message ID
  writeNumber(stream, id)

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }

  return stream.write(Buffer.from(granted))
}

function unsubscribe (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const id = settings.messageId
  const dup = settings.dup ? protocol.DUP_MASK : 0
  const unsubs = settings.unsubscriptions
  const properties = settings.properties

  let length = 0

  // Check message ID
  if (typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  } else {
    length += 2
  }
  // Check unsubs
  if (typeof unsubs === 'object' && unsubs.length) {
    for (let i = 0; i < unsubs.length; i += 1) {
      if (typeof unsubs[i] !== 'string') {
        stream.emit('error', new Error('Invalid unsubscriptions'))
        return false
      }
      length += Buffer.byteLength(unsubs[i]) + 2
    }
  } else {
    stream.emit('error', new Error('Invalid unsubscriptions'))
    return false
  }
  // properies mqtt 5
  let propertiesData = null
  if (version === 5) {
    propertiesData = getProperties(stream, properties)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // Header
  stream.write(protocol.UNSUBSCRIBE_HEADER[1][dup ? 1 : 0][0])

  // Length
  writeVarByteInt(stream, length)

  // Message ID
  writeNumber(stream, id)

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }

  // Unsubs
  let result = true
  for (let j = 0; j < unsubs.length; j++) {
    result = writeString(stream, unsubs[j])
  }

  return result
}

function unsuback (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const id = settings.messageId
  const dup = settings.dup ? protocol.DUP_MASK : 0
  const granted = settings.granted
  const properties = settings.properties
  const type = settings.cmd
  const qos = 0

  let length = 2

  // Check message ID
  if (typeof id !== 'number') {
    stream.emit('error', new Error('Invalid messageId'))
    return false
  }

  // Check granted
  if (version === 5) {
    if (typeof granted === 'object' && granted.length) {
      for (let i = 0; i < granted.length; i += 1) {
        if (typeof granted[i] !== 'number') {
          stream.emit('error', new Error('Invalid qos vector'))
          return false
        }
        length += 1
      }
    } else {
      stream.emit('error', new Error('Invalid qos vector'))
      return false
    }
  }

  // properies mqtt 5
  let propertiesData = null
  if (version === 5) {
    propertiesData = getPropertiesByMaximumPacketSize(stream, properties, opts, length)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // Header
  stream.write(protocol.ACKS[type][qos][dup][0])

  // Length
  writeVarByteInt(stream, length)

  // Message ID
  writeNumber(stream, id)

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }

  // payload
  if (version === 5) {
    stream.write(Buffer.from(granted))
  }
  return true
}

function emptyPacket (packet, stream, opts) {
  return stream.write(protocol.EMPTY[packet.cmd])
}

function disconnect (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const reasonCode = settings.reasonCode
  const properties = settings.properties
  let length = version === 5 ? 1 : 0

  // properies mqtt 5
  let propertiesData = null
  if (version === 5) {
    propertiesData = getPropertiesByMaximumPacketSize(stream, properties, opts, length)
    if (!propertiesData) { return false }
    length += propertiesData.length
  }

  // Header
  stream.write(Buffer.from([protocol.codes.disconnect << 4]))

  // Length
  writeVarByteInt(stream, length)

  // reason code in header
  if (version === 5) {
    stream.write(Buffer.from([reasonCode]))
  }

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }

  return true
}

function auth (packet, stream, opts) {
  const version = opts ? opts.protocolVersion : 4
  const settings = packet || {}
  const reasonCode = settings.reasonCode
  const properties = settings.properties
  let length = version === 5 ? 1 : 0

  if (version !== 5) stream.emit('error', new Error('Invalid mqtt version for auth packet'))

  // properies mqtt 5
  const propertiesData = getPropertiesByMaximumPacketSize(stream, properties, opts, length)
  if (!propertiesData) { return false }
  length += propertiesData.length

  // Header
  stream.write(Buffer.from([protocol.codes.auth << 4]))

  // Length
  writeVarByteInt(stream, length)

  // reason code in header
  stream.write(Buffer.from([reasonCode]))

  // properies mqtt 5
  if (propertiesData !== null) {
    propertiesData.write()
  }
  return true
}

/**
 * writeVarByteInt - write an MQTT style variable byte integer to the buffer
 *
 * @param <Buffer> buffer - destination
 * @param <Number> pos - offset
 * @param <Number> length - length (>0)
 * @returns <Number> number of bytes written
 *
 * @api private
 */

const varByteIntCache = {}
function writeVarByteInt (stream, num) {
  if (num > protocol.VARBYTEINT_MAX) {
    stream.emit('error', new Error(`Invalid variable byte integer: ${num}`))
    return false
  }

  let buffer = varByteIntCache[num]

  if (!buffer) {
    buffer = genBufVariableByteInt(num)
    if (num < 16384) varByteIntCache[num] = buffer
  }
  debug('writeVarByteInt: writing to stream: %o', buffer)
  return stream.write(buffer)
}

/**
 * writeString - write a utf8 string to the buffer
 *
 * @param <Buffer> buffer - destination
 * @param <Number> pos - offset
 * @param <String> string - string to write
 * @return <Number> number of bytes written
 *
 * @api private
 */

function writeString (stream, string) {
  const strlen = Buffer.byteLength(string)
  writeNumber(stream, strlen)

  debug('writeString: %s', string)
  return stream.write(string, 'utf8')
}

/**
 * writeStringPair - write a utf8 string pairs to the buffer
 *
 * @param <Buffer> buffer - destination
 * @param <String> name - string name to write
 * @param <String> value - string value to write
 * @return <Number> number of bytes written
 *
 * @api private
 */
function writeStringPair (stream, name, value) {
  writeString(stream, name)
  writeString(stream, value)
}

/**
 * writeNumber - write a two byte number to the buffer
 *
 * @param <Buffer> buffer - destination
 * @param <Number> pos - offset
 * @param <String> number - number to write
 * @return <Number> number of bytes written
 *
 * @api private
 */
function writeNumberCached (stream, number) {
  debug('writeNumberCached: number: %d', number)
  debug('writeNumberCached: %o', numCache[number])
  return stream.write(numCache[number])
}
function writeNumberGenerated (stream, number) {
  const generatedNumber = generateNumber(number)
  debug('writeNumberGenerated: %o', generatedNumber)
  return stream.write(generatedNumber)
}
function write4ByteNumber (stream, number) {
  const generated4ByteBuffer = generate4ByteBuffer(number)
  debug('write4ByteNumber: %o', generated4ByteBuffer)
  return stream.write(generated4ByteBuffer)
}
/**
 * writeStringOrBuffer - write a String or Buffer with the its length prefix
 *
 * @param <Buffer> buffer - destination
 * @param <Number> pos - offset
 * @param <String> toWrite - String or Buffer
 * @return <Number> number of bytes written
 */
function writeStringOrBuffer (stream, toWrite) {
  if (typeof toWrite === 'string') {
    writeString(stream, toWrite)
  } else if (toWrite) {
    writeNumber(stream, toWrite.length)
    stream.write(toWrite)
  } else writeNumber(stream, 0)
}

function getProperties (stream, properties) {
  /* connect properties */
  if (typeof properties !== 'object' || properties.length != null) {
    return {
      length: 1,
      write () {
        writeProperties(stream, {}, 0)
      }
    }
  }
  let propertiesLength = 0
  function getLengthProperty (name, value) {
    const type = protocol.propertiesTypes[name]
    let length = 0
    switch (type) {
      case 'byte': {
        if (typeof value !== 'boolean') {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + 1
        break
      }
      case 'int8': {
        if (typeof value !== 'number' || value < 0 || value > 0xff) {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + 1
        break
      }
      case 'binary': {
        if (value && value === null) {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + Buffer.byteLength(value) + 2
        break
      }
      case 'int16': {
        if (typeof value !== 'number' || value < 0 || value > 0xffff) {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + 2
        break
      }
      case 'int32': {
        if (typeof value !== 'number' || value < 0 || value > 0xffffffff) {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + 4
        break
      }
      case 'var': {
        // var byte integer is max 24 bits packed in 32 bits
        if (typeof value !== 'number' || value < 0 || value > 0x0fffffff) {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + Buffer.byteLength(genBufVariableByteInt(value))
        break
      }
      case 'string': {
        if (typeof value !== 'string') {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += 1 + 2 + Buffer.byteLength(value.toString())
        break
      }
      case 'pair': {
        if (typeof value !== 'object') {
          stream.emit('error', new Error(`Invalid ${name}: ${value}`))
          return false
        }
        length += Object.getOwnPropertyNames(value).reduce((result, name) => {
          const currentValue = value[name]
          if (Array.isArray(currentValue)) {
            result += currentValue.reduce((currentLength, value) => {
              currentLength += 1 + 2 + Buffer.byteLength(name.toString()) + 2 + Buffer.byteLength(value.toString())
              return currentLength
            }, 0)
          } else {
            result += 1 + 2 + Buffer.byteLength(name.toString()) + 2 + Buffer.byteLength(value[name].toString())
          }
          return result
        }, 0)
        break
      }
      default: {
        stream.emit('error', new Error(`Invalid property ${name}: ${value}`))
        return false
      }
    }
    return length
  }
  if (properties) {
    for (const propName in properties) {
      let propLength = 0
      let propValueLength = 0
      const propValue = properties[propName]
      if (Array.isArray(propValue)) {
        for (let valueIndex = 0; valueIndex < propValue.length; valueIndex++) {
          propValueLength = getLengthProperty(propName, propValue[valueIndex])
          if (!propValueLength) { return false }
          propLength += propValueLength
        }
      } else {
        propValueLength = getLengthProperty(propName, propValue)
        if (!propValueLength) { return false }
        propLength = propValueLength
      }
      if (!propLength) return false
      propertiesLength += propLength
    }
  }
  const propertiesLengthLength = Buffer.byteLength(genBufVariableByteInt(propertiesLength))

  return {
    length: propertiesLengthLength + propertiesLength,
    write () {
      writeProperties(stream, properties, propertiesLength)
    }
  }
}

function getPropertiesByMaximumPacketSize (stream, properties, opts, length) {
  const mayEmptyProps = ['reasonString', 'userProperties']
  const maximumPacketSize = opts && opts.properties && opts.properties.maximumPacketSize ? opts.properties.maximumPacketSize : 0

  let propertiesData = getProperties(stream, properties)
  if (maximumPacketSize) {
    while (length + propertiesData.length > maximumPacketSize) {
      const currentMayEmptyProp = mayEmptyProps.shift()
      if (currentMayEmptyProp && properties[currentMayEmptyProp]) {
        delete properties[currentMayEmptyProp]
        propertiesData = getProperties(stream, properties)
      } else {
        return false
      }
    }
  }
  return propertiesData
}

function writeProperty (stream, propName, value) {
  const type = protocol.propertiesTypes[propName]
  switch (type) {
    case 'byte': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      stream.write(Buffer.from([+value]))
      break
    }
    case 'int8': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      stream.write(Buffer.from([value]))
      break
    }
    case 'binary': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      writeStringOrBuffer(stream, value)
      break
    }
    case 'int16': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      writeNumber(stream, value)
      break
    }
    case 'int32': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      write4ByteNumber(stream, value)
      break
    }
    case 'var': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      writeVarByteInt(stream, value)
      break
    }
    case 'string': {
      stream.write(Buffer.from([protocol.properties[propName]]))
      writeString(stream, value)
      break
    }
    case 'pair': {
      Object.getOwnPropertyNames(value).forEach(name => {
        const currentValue = value[name]
        if (Array.isArray(currentValue)) {
          currentValue.forEach(value => {
            stream.write(Buffer.from([protocol.properties[propName]]))
            writeStringPair(stream, name.toString(), value.toString())
          })
        } else {
          stream.write(Buffer.from([protocol.properties[propName]]))
          writeStringPair(stream, name.toString(), currentValue.toString())
        }
      })
      break
    }
    default: {
      stream.emit('error', new Error(`Invalid property ${propName} value: ${value}`))
      return false
    }
  }
}

function writeProperties (stream, properties, propertiesLength) {
  /* write properties to stream */
  writeVarByteInt(stream, propertiesLength)
  for (const propName in properties) {
    if (Object.prototype.hasOwnProperty.call(properties, propName) && properties[propName] !== null) {
      const value = properties[propName]
      if (Array.isArray(value)) {
        for (let valueIndex = 0; valueIndex < value.length; valueIndex++) {
          writeProperty(stream, propName, value[valueIndex])
        }
      } else {
        writeProperty(stream, propName, value)
      }
    }
  }
}

function byteLength (bufOrString) {
  if (!bufOrString) return 0
  else if (bufOrString instanceof Buffer) return bufOrString.length
  else return Buffer.byteLength(bufOrString)
}

function isStringOrBuffer (field) {
  return typeof field === 'string' || field instanceof Buffer
}

module.exports = generate