# encoding: BINARY

module MQTT

  # Class representing a MQTT Packet
  # Performs binary encoding and decoding of headers
  class MQTT::Packet
    # The version number of the MQTT protocol to use (default 3.1.0)
    attr_accessor :version

    # Identifier to link related control packets together
    attr_accessor :id

    # Array of 4 bits in the fixed header
    attr_accessor :flags

    # The length of the parsed packet body
    attr_reader :body_length

    # Default attribute values
    ATTR_DEFAULTS = {
      :version => '3.1.0',
      :id => 0,
      :body_length => nil
    }

    # Read in a packet from a socket
    def self.read(socket)
      # Read in the packet header and create a new packet object
      packet = create_from_header(
        read_byte(socket)
      )
      packet.validate_flags

      # Read in the packet length
      multiplier = 1
      body_length = 0
      pos = 1
      begin
        digit = read_byte(socket)
        body_length += ((digit & 0x7F) * multiplier)
        multiplier *= 0x80
        pos += 1
      end while ((digit & 0x80) != 0x00) and pos <= 4

      # Store the expected body length in the packet
      packet.instance_variable_set('@body_length', body_length)

      # Read in the packet body
      packet.parse_body( socket.read(body_length) )

      return packet
    end

    # Parse buffer into new packet object
    def self.parse(buffer)
      packet = parse_header(buffer)
      packet.parse_body(buffer)
      return packet
    end

    # Parse the header and create a new packet object of the correct type
    # The header is removed from the buffer passed into this function
    def self.parse_header(buffer)
      # Check that the packet is a long as the minimum packet size
      if buffer.bytesize < 2
        raise ProtocolException.new("Invalid packet: less than 2 bytes long")
      end

      # Create a new packet object
      bytes = buffer.unpack("C5")
      packet = create_from_header(bytes.first)
      packet.validate_flags

      # Parse the packet length
      body_length = 0
      multiplier = 1
      pos = 1
      begin
        if buffer.bytesize <= pos
          raise ProtocolException.new("The packet length header is incomplete")
        end
        digit = bytes[pos]
        body_length += ((digit & 0x7F) * multiplier)
        multiplier *= 0x80
        pos += 1
      end while ((digit & 0x80) != 0x00) and pos <= 4

      # Store the expected body length in the packet
      packet.instance_variable_set('@body_length', body_length)

      # Delete the fixed header from the raw packet passed in
      buffer.slice!(0...pos)

      return packet
    end

    # Create a new packet object from the first byte of a MQTT packet
    def self.create_from_header(byte)
      # Work out the class
      type_id = ((byte & 0xF0) >> 4)
      packet_class = MQTT::PACKET_TYPES[type_id]
      if packet_class.nil?
        raise ProtocolException.new("Invalid packet type identifier: #{type_id}")
      end

      # Convert the last 4 bits of byte into array of true/false
      flags = (0..3).map { |i| byte & (2 ** i) != 0 }

      # Create a new packet object
      packet_class.new(:flags => flags)
    end

    # Create a new empty packet
    def initialize(args={})
      # We must set flags before the other values
      @flags = [false, false, false, false]
      update_attributes(ATTR_DEFAULTS.merge(args))
    end

    # Set packet attributes from a hash of attribute names and values
    def update_attributes(attr={})
      attr.each_pair do |k,v|
        if v.is_a?(Array) or v.is_a?(Hash)
          send("#{k}=", v.dup)
        else
          send("#{k}=", v)
        end
      end
    end

    # Get the identifer for this packet type
    def type_id
      index = MQTT::PACKET_TYPES.index(self.class)
      if index.nil?
        raise "Invalid packet type: #{self.class}"
      end
      return index
    end

    # Get the name of the packet type as a string in capitals
    # (like the MQTT specification uses)
    #
    # Example: CONNACK
    def type_name
      self.class.name.split('::').last.upcase
    end

    # Set the protocol version number
    def version=(arg)
      @version = arg.to_s
    end

    # Set the length of the packet body
    def body_length=(arg)
      @body_length = arg.to_i
    end

    # Parse the body (variable header and payload) of a packet
    def parse_body(buffer)
      if buffer.bytesize != body_length
        raise ProtocolException.new(
          "Failed to parse packet - input buffer (#{buffer.bytesize}) is not the same as the body length header (#{body_length})"
        )
      end
    end

    # Get serialisation of packet's body (variable header and payload)
    def encode_body
      '' # No body by default
    end


    # Serialise the packet
    def to_s
      # Encode the fixed header
      header = [
        ((type_id.to_i & 0x0F) << 4) |
        (flags[3] ? 0x8 : 0x0) |
        (flags[2] ? 0x4 : 0x0) |
        (flags[1] ? 0x2 : 0x0) |
        (flags[0] ? 0x1 : 0x0)
      ]

      # Get the packet's variable header and payload
      body = self.encode_body

      # Check that that packet isn't too big
      body_length = body.bytesize
      if body_length > 268435455
        raise "Error serialising packet: body is more than 256MB"
      end

      # Build up the body length field bytes
      begin
        digit = (body_length % 128)
        body_length = body_length.div(128)
        # if there are more digits to encode, set the top bit of this digit
        digit |= 0x80 if (body_length > 0)
        header.push(digit)
      end while (body_length > 0)

      # Convert header to binary and add on body
      header.pack('C*') + body
    end

    # Check that fixed header flags are valid for types that don't use the flags
    # @private
    def validate_flags
      if flags != [false, false, false, false]
        raise ProtocolException.new("Invalid flags in #{type_name} packet header")
      end
    end

    # Returns a human readable string
    def inspect
      "\#<#{self.class}>"
    end

    protected

    # Encode an array of bytes and return them
    def encode_bytes(*bytes)
      bytes.pack('C*')
    end

    # Encode an array of bits and return them
    def encode_bits(bits)
      [bits.map{|b| b ? '1' : '0'}.join].pack('b*')
    end

    # Encode a 16-bit unsigned integer and return it
    def encode_short(val)
      [val.to_i].pack('n')
    end

    # Encode a UTF-8 string and return it
    # (preceded by the length of the string)
    def encode_string(str)
      str = str.to_s.encode('UTF-8')

      # Force to binary, when assembling the packet
      str.force_encoding('ASCII-8BIT')
      encode_short(str.bytesize) + str
    end

    # Remove a 16-bit unsigned integer from the front of buffer
    def shift_short(buffer)
      bytes = buffer.slice!(0..1)
      bytes.unpack('n').first
    end

    # Remove one byte from the front of the string
    def shift_byte(buffer)
      buffer.slice!(0...1).unpack('C').first
    end

    # Remove 8 bits from the front of buffer
    def shift_bits(buffer)
      buffer.slice!(0...1).unpack('b8').first.split('').map {|b| b == '1'}
    end

    # Remove n bytes from the front of buffer
    def shift_data(buffer,bytes)
      buffer.slice!(0...bytes)
    end

    # Remove string from the front of buffer
    def shift_string(buffer)
      len = shift_short(buffer)
      str = shift_data(buffer,len)
      # Strings in MQTT v3.1 are all UTF-8
      str.force_encoding('UTF-8')
    end


    private

    # Read and unpack a single byte from a socket
    def self.read_byte(socket)
      byte = socket.read(1)
      if byte.nil?
        raise ProtocolException.new("Failed to read byte from socket")
      end
      byte.unpack('C').first
    end



    ## PACKET SUBCLASSES ##


    # Class representing an MQTT Publish message
    class Publish < MQTT::Packet

      # Duplicate delivery flag
      attr_accessor :duplicate

      # Retain flag
      attr_accessor :retain

      # Quality of Service level (0, 1, 2)
      attr_accessor :qos

      # The topic name to publish to
      attr_accessor :topic

      # The data to be published
      attr_accessor :payload

      # Default attribute values
      ATTR_DEFAULTS = {
        :topic => nil,
        :payload => ''
      }

      # Create a new Publish packet
      def initialize(args={})
        super(ATTR_DEFAULTS.merge(args))
      end

      def duplicate
        @flags[3]
      end

      # Set the DUP flag (true/false)
      def duplicate=(arg)
        if arg.kind_of?(Integer)
          @flags[3] = (arg == 0x1)
        else
          @flags[3] = arg
        end
      end

      def retain
        @flags[0]
      end

      # Set the retain flag (true/false)
      def retain=(arg)
        if arg.kind_of?(Integer)
          @flags[0] = (arg == 0x1)
        else
          @flags[0] = arg
        end
      end

      def qos
        (@flags[1] ? 0x01 : 0x00) | (@flags[2] ? 0x02 : 0x00)
      end

      # Set the Quality of Service level (0/1/2)
      def qos=(arg)
        @qos = arg.to_i
        if @qos < 0 or @qos > 2
          raise "Invalid QoS value: #{@qos}"
        else
          @flags[1] = (arg & 0x01 == 0x01)
          @flags[2] = (arg & 0x02 == 0x02)
        end
      end

      # Get serialisation of packet's body
      def encode_body
        body = ''
        if @topic.nil? or @topic.to_s.empty?
          raise "Invalid topic name when serialising packet"
        end
        body += encode_string(@topic)
        body += encode_short(@id) unless qos == 0
        body += payload.to_s.dup.force_encoding('ASCII-8BIT')
        return body
      end

      # Parse the body (variable header and payload) of a Publish packet
      def parse_body(buffer)
        super(buffer)
        @topic = shift_string(buffer)
        @id = shift_short(buffer) unless qos == 0
        @payload = buffer
      end

      # Check that fixed header flags are valid for this packet type
      # @private
      def validate_flags
        if qos == 3
          raise ProtocolException.new("Invalid packet: QoS value of 3 is not allowed")
        end
        if qos == 0 and duplicate
          raise ProtocolException.new("Invalid packet: DUP cannot be set for QoS 0")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: " +
        "d#{duplicate ? '1' : '0'}, " +
        "q#{qos}, " +
        "r#{retain ? '1' : '0'}, " +
        "m#{id}, " +
        "'#{topic}', " +
        "#{inspect_payload}>"
      end

      protected

      def inspect_payload
        str = payload.to_s
        if str.bytesize < 16 and str =~ /^[ -~]*$/
          "'#{str}'"
        else
          "... (#{str.bytesize} bytes)"
        end
      end
    end

    # Class representing an MQTT Connect Packet
    class Connect < MQTT::Packet
      # The name of the protocol
      attr_accessor :protocol_name

      # The version number of the protocol
      attr_accessor :protocol_level

      # The client identifier string
      attr_accessor :client_id

      # Set to false to keep a persistent session with the server
      attr_accessor :clean_session

      # Period the server should keep connection open for between pings
      attr_accessor :keep_alive

      # The topic name to send the Will message to
      attr_accessor :will_topic

      # The QoS level to send the Will message as
      attr_accessor :will_qos

      # Set to true to make the Will message retained
      attr_accessor :will_retain

      # The payload of the Will message
      attr_accessor :will_payload

      # The username for authenticating with the server
      attr_accessor :username

      # The password for authenticating with the server
      attr_accessor :password

      # Default attribute values
      ATTR_DEFAULTS = {
        :client_id => nil,
        :clean_session => true,
        :keep_alive => 15,
        :will_topic => nil,
        :will_qos => 0,
        :will_retain => false,
        :will_payload => '',
        :username => nil,
        :password => nil,
      }

      # Create a new Client Connect packet
      def initialize(args={})
        super(ATTR_DEFAULTS.merge(args))

        if version == '3.1.0' or version == '3.1'
          self.protocol_name ||= 'MQIsdp'
          self.protocol_level ||= 0x03
        elsif version == '3.1.1'
          self.protocol_name ||= 'MQTT'
          self.protocol_level ||= 0x04
        else
          raise ArgumentError.new("Unsupported protocol version: #{version}")
        end
      end

      # Get serialisation of packet's body
      def encode_body
        body = ''
        if @version == '3.1.0'
          if @client_id.nil? or @client_id.bytesize < 1
            raise "Client identifier too short while serialising packet"
          elsif @client_id.bytesize > 23
            raise "Client identifier too long when serialising packet"
          end
        end
        body += encode_string(@protocol_name)
        body += encode_bytes(@protocol_level.to_i)

        if @keep_alive < 0
          raise "Invalid keep-alive value: cannot be less than 0"
        end

        # Set the Connect flags
        @connect_flags = 0
        @connect_flags |= 0x02 if @clean_session
        @connect_flags |= 0x04 unless @will_topic.nil?
        @connect_flags |= ((@will_qos & 0x03) << 3)
        @connect_flags |= 0x20 if @will_retain
        @connect_flags |= 0x40 unless @password.nil?
        @connect_flags |= 0x80 unless @username.nil?
        body += encode_bytes(@connect_flags)

        body += encode_short(@keep_alive)
        body += encode_string(@client_id)
        unless will_topic.nil?
          body += encode_string(@will_topic)
          # The MQTT v3.1 specification says that the payload is a UTF-8 string
          body += encode_string(@will_payload)
        end
        body += encode_string(@username) unless @username.nil?
        body += encode_string(@password) unless @password.nil?
        return body
      end

      # Parse the body (variable header and payload) of a Connect packet
      def parse_body(buffer)
        super(buffer)
        @protocol_name = shift_string(buffer)
        @protocol_level = shift_byte(buffer).to_i
        if @protocol_name == 'MQIsdp' and @protocol_level == 3
          @version = '3.1.0'
        elsif @protocol_name == 'MQTT' and @protocol_level == 4
          @version = '3.1.1'
        else
          raise ProtocolException.new(
            "Unsupported protocol: #{@protocol_name}/#{@protocol_level}"
          )
        end

        @connect_flags = shift_byte(buffer)
        @clean_session = ((@connect_flags & 0x02) >> 1) == 0x01
        @keep_alive = shift_short(buffer)
        @client_id = shift_string(buffer)
        if ((@connect_flags & 0x04) >> 2) == 0x01
          # Last Will and Testament
          @will_qos = ((@connect_flags & 0x18) >> 3)
          @will_retain = ((@connect_flags & 0x20) >> 5) == 0x01
          @will_topic = shift_string(buffer)
          # The MQTT v3.1 specification says that the payload is a UTF-8 string
          @will_payload = shift_string(buffer)
        end
        if ((@connect_flags & 0x80) >> 7) == 0x01 and buffer.bytesize > 0
          @username = shift_string(buffer)
        end
        if ((@connect_flags & 0x40) >> 6) == 0x01 and buffer.bytesize > 0
          @password = shift_string(buffer)
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        str = "\#<#{self.class}: "
        str += "keep_alive=#{keep_alive}"
        str += ", clean" if clean_session
        str += ", client_id='#{client_id}'"
        str += ", username='#{username}'" unless username.nil?
        str += ", password=..." unless password.nil?
        str += ">"
      end

      # ---- Deprecated attributes and methods  ---- #
      public

      # @deprecated Please use {#protocol_level} instead
      def protocol_version
        protocol_level
      end

      # @deprecated Please use {#protocol_level=} instead
      def protocol_version=(args)
        self.protocol_level = args
      end
    end

    # Class representing an MQTT Connect Acknowledgment Packet
    class Connack < MQTT::Packet
      # Session Present flag
      attr_accessor :session_present

      # The return code (defaults to 0 for connection accepted)
      attr_accessor :return_code

      # Default attribute values
      ATTR_DEFAULTS = {:return_code => 0x00}

      # Create a new Client Connect packet
      def initialize(args={})
        # We must set flags before other attributes
        @connack_flags = [false, false, false, false, false, false, false, false]
        super(ATTR_DEFAULTS.merge(args))
      end

      # Get the Session Present flag
      def session_present
        @connack_flags[0]
      end

      # Set the Session Present flag
      def session_present=(arg)
        if arg.kind_of?(Integer)
          @connack_flags[0] = (arg == 0x1)
        else
          @connack_flags[0] = arg
        end
      end

      # Get a string message corresponding to a return code
      def return_msg
        case return_code
          when 0x00
            "Connection Accepted"
          when 0x01
            "Connection refused: unacceptable protocol version"
          when 0x02
            "Connection refused: client identifier rejected"
          when 0x03
            "Connection refused: server unavailable"
          when 0x04
            "Connection refused: bad user name or password"
          when 0x05
            "Connection refused: not authorised"
          else
            "Connection refused: error code #{return_code}"
        end
      end

      # Get serialisation of packet's body
      def encode_body
        body = ''
        body += encode_bits(@connack_flags)
        body += encode_bytes(@return_code.to_i)
        return body
      end

      # Parse the body (variable header and payload) of a Connect Acknowledgment packet
      def parse_body(buffer)
        super(buffer)
        @connack_flags = shift_bits(buffer)
        unless @connack_flags[1,7] == [false, false, false, false, false, false, false]
          raise ProtocolException.new("Invalid flags in Connack variable header")
        end
        @return_code = shift_byte(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Connect Acknowledgment packet")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X>" % return_code
      end
    end

    # Class representing an MQTT Publish Acknowledgment packet
    class Puback < MQTT::Packet
      # Get serialisation of packet's body
      def encode_body
        encode_short(@id)
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Publish Acknowledgment packet")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X>" % id
      end
    end

    # Class representing an MQTT Publish Received packet
    class Pubrec < MQTT::Packet
      # Get serialisation of packet's body
      def encode_body
        encode_short(@id)
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Publish Received packet")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X>" % id
      end
    end

    # Class representing an MQTT Publish Release packet
    class Pubrel < MQTT::Packet

      # Default attribute values
      ATTR_DEFAULTS = {
        :flags => [false, true, false, false],
      }

      # Create a new Pubrel packet
      def initialize(args={})
        super(ATTR_DEFAULTS.merge(args))
      end

      # Get serialisation of packet's body
      def encode_body
        encode_short(@id)
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Publish Release packet")
        end
      end

      # Check that fixed header flags are valid for this packet type
      # @private
      def validate_flags
        if @flags != [false, true, false, false]
          raise ProtocolException.new("Invalid flags in PUBREL packet header")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X>" % id
      end
    end

    # Class representing an MQTT Publish Complete packet
    class Pubcomp < MQTT::Packet
      # Get serialisation of packet's body
      def encode_body
        encode_short(@id)
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Publish Complete packet")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X>" % id
      end
    end

    # Class representing an MQTT Client Subscribe packet
    class Subscribe < MQTT::Packet
      # One or more topic filters to subscribe to
      attr_accessor :topics

      # Default attribute values
      ATTR_DEFAULTS = {
        :topics => [],
        :flags => [false, true, false, false],
      }

      # Create a new Subscribe packet
      def initialize(args={})
        super(ATTR_DEFAULTS.merge(args))
      end

      # Set one or more topic filters for the Subscribe packet
      # The topics parameter should be one of the following:
      # * String: subscribe to one topic with QoS 0
      # * Array: subscribe to multiple topics with QoS 0
      # * Hash: subscribe to multiple topics where the key is the topic and the value is the QoS level
      #
      # For example:
      #   packet.topics = 'a/b'
      #   packet.topics = ['a/b', 'c/d']
      #   packet.topics = [['a/b',0], ['c/d',1]]
      #   packet.topics = {'a/b' => 0, 'c/d' => 1}
      #
      def topics=(value)
        # Get input into a consistent state
        if value.is_a?(Array)
          input = value.flatten
        else
          input = [value]
        end

        @topics = []
        while(input.length>0)
          item = input.shift
          if item.is_a?(Hash)
            # Convert hash into an ordered array of arrays
            @topics += item.sort
          elsif item.is_a?(String)
            # Peek at the next item in the array, and remove it if it is an integer
            if input.first.is_a?(Integer)
              qos = input.shift
              @topics << [item,qos]
            else
              @topics << [item,0]
            end
          else
            # Meh?
            raise "Invalid topics input: #{value.inspect}"
          end
        end
        @topics
      end

      # Get serialisation of packet's body
      def encode_body
        if @topics.empty?
          raise "no topics given when serialising packet"
        end
        body = encode_short(@id)
        topics.each do |item|
          body += encode_string(item[0])
          body += encode_bytes(item[1])
        end
        return body
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        @topics = []
        while(buffer.bytesize>0)
          topic_name = shift_string(buffer)
          topic_qos = shift_byte(buffer)
          @topics << [topic_name,topic_qos]
        end
      end

      # Check that fixed header flags are valid for this packet type
      # @private
      def validate_flags
        if @flags != [false, true, false, false]
          raise ProtocolException.new("Invalid flags in SUBSCRIBE packet header")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        _str = "\#<#{self.class}: 0x%2.2X, %s>" % [
          id,
          topics.map {|t| "'#{t[0]}':#{t[1]}"}.join(', ')
        ]
      end
    end

    # Class representing an MQTT Subscribe Acknowledgment packet
    class Suback < MQTT::Packet
      # An array of return codes, ordered by the topics that were subscribed to
      attr_accessor :return_codes

      # Default attribute values
      ATTR_DEFAULTS = {
        :return_codes => [],
      }

      # Create a new Subscribe Acknowledgment packet
      def initialize(args={})
        super(ATTR_DEFAULTS.merge(args))
      end

      # Set the granted QoS value for each of the topics that were subscribed to
      # Can either be an integer or an array or integers.
      def return_codes=(value)
        if value.is_a?(Array)
          @return_codes = value
        elsif value.is_a?(Integer)
          @return_codes = [value]
        else
          raise "return_codes should be an integer or an array of return codes"
        end
      end

      # Get serialisation of packet's body
      def encode_body
        if @return_codes.empty?
          raise "no granted QoS given when serialising packet"
        end
        body = encode_short(@id)
        return_codes.each { |qos| body += encode_bytes(qos) }
        return body
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        while(buffer.bytesize>0)
          @return_codes << shift_byte(buffer)
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X, rc=%s>" % [id, return_codes.map{|rc| "0x%2.2X" % rc}.join(',')]
      end

      # ---- Deprecated attributes and methods  ---- #
      public

      # @deprecated Please use {#return_codes} instead
      def granted_qos
        return_codes
      end

      # @deprecated Please use {#return_codes=} instead
      def granted_qos=(args)
        self.return_codes = args
      end
    end

    # Class representing an MQTT Client Unsubscribe packet
    class Unsubscribe < MQTT::Packet
      # One or more topic paths to unsubscribe from
      attr_accessor :topics

      # Default attribute values
      ATTR_DEFAULTS = {
        :topics => [],
        :flags => [false, true, false, false],
      }

      # Create a new Unsubscribe packet
      def initialize(args={})
        super(ATTR_DEFAULTS.merge(args))
      end

      # Set one or more topic paths to unsubscribe from
      def topics=(value)
        if value.is_a?(Array)
          @topics = value
        else
          @topics = [value]
        end
      end

      # Get serialisation of packet's body
      def encode_body
        if @topics.empty?
          raise "no topics given when serialising packet"
        end
        body = encode_short(@id)
        topics.each { |topic| body += encode_string(topic) }
        return body
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        while(buffer.bytesize>0)
          @topics << shift_string(buffer)
        end
      end

      # Check that fixed header flags are valid for this packet type
      # @private
      def validate_flags
        if @flags != [false, true, false, false]
          raise ProtocolException.new("Invalid flags in UNSUBSCRIBE packet header")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X, %s>" % [
          id,
          topics.map {|t| "'#{t}'"}.join(', ')
        ]
      end
    end

    # Class representing an MQTT Unsubscribe Acknowledgment packet
    class Unsuback < MQTT::Packet
      # Create a new Unsubscribe Acknowledgment packet
      def initialize(args={})
        super(args)
      end

      # Get serialisation of packet's body
      def encode_body
        encode_short(@id)
      end

      # Parse the body (variable header and payload) of a packet
      def parse_body(buffer)
        super(buffer)
        @id = shift_short(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Unsubscribe Acknowledgment packet")
        end
      end

      # Returns a human readable string, summarising the properties of the packet
      def inspect
        "\#<#{self.class}: 0x%2.2X>" % id
      end
    end

    # Class representing an MQTT Ping Request packet
    class Pingreq < MQTT::Packet
      # Create a new Ping Request packet
      def initialize(args={})
        super(args)
      end

      # Check the body
      def parse_body(buffer)
        super(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Ping Request packet")
        end
      end
    end

    # Class representing an MQTT Ping Response packet
    class Pingresp < MQTT::Packet
      # Create a new Ping Response packet
      def initialize(args={})
        super(args)
      end

      # Check the body
      def parse_body(buffer)
        super(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Ping Response packet")
        end
      end
    end

    # Class representing an MQTT Client Disconnect packet
    class Disconnect < MQTT::Packet
      # Create a new Client Disconnect packet
      def initialize(args={})
        super(args)
      end

      # Check the body
      def parse_body(buffer)
        super(buffer)
        unless buffer.empty?
          raise ProtocolException.new("Extra bytes at end of Disconnect packet")
        end
      end
    end


    # ---- Deprecated attributes and methods  ---- #
    public

    # @deprecated Please use {#id} instead
    def message_id
      id
    end

    # @deprecated Please use {#id=} instead
    def message_id=(args)
      self.id = args
    end
  end


  # An enumeration of the MQTT packet types
  PACKET_TYPES = [
    nil,
    MQTT::Packet::Connect,
    MQTT::Packet::Connack,
    MQTT::Packet::Publish,
    MQTT::Packet::Puback,
    MQTT::Packet::Pubrec,
    MQTT::Packet::Pubrel,
    MQTT::Packet::Pubcomp,
    MQTT::Packet::Subscribe,
    MQTT::Packet::Suback,
    MQTT::Packet::Unsubscribe,
    MQTT::Packet::Unsuback,
    MQTT::Packet::Pingreq,
    MQTT::Packet::Pingresp,
    MQTT::Packet::Disconnect,
    nil
  ]

end