autoload :OpenSSL, 'openssl'
autoload :URI, 'uri'


# Client class for talking to an MQTT server
class MQTT::Client
  # Hostname of the remote server
  attr_accessor :host

  # Port number of the remote server
  attr_accessor :port

  # The version number of the MQTT protocol to use (default 3.1.1)
  attr_accessor :version

  # Set to true to enable SSL/TLS encrypted communication
  #
  # Set to a symbol to use a specific variant of SSL/TLS.
  # Allowed values include:
  #
  # @example Using TLS 1.0
  #    client = Client.new('mqtt.example.com', :ssl => :TLSv1)
  # @see OpenSSL::SSL::SSLContext::METHODS
  attr_accessor :ssl

  # Time (in seconds) between pings to remote server (default is 15 seconds)
  attr_accessor :keep_alive

  # Set the 'Clean Session' flag when connecting? (default is true)
  attr_accessor :clean_session

  # Client Identifier
  attr_accessor :client_id

  # Number of seconds to wait for acknowledgement packets (default is 5 seconds)
  attr_accessor :ack_timeout

  # Username to authenticate to the server with
  attr_accessor :username

  # Password to authenticate to the server with
  attr_accessor :password

  # The topic that the Will message is published to
  attr_accessor :will_topic

  # Contents of message that is sent by server when client disconnect
  attr_accessor :will_payload

  # The QoS level of the will message sent by the server
  attr_accessor :will_qos

  # If the Will message should be retain by the server after it is sent
  attr_accessor :will_retain

  # Last ping response time
  attr_reader :last_ping_response


  # Timeout between select polls (in seconds)
  SELECT_TIMEOUT = 0.5

  # Default attribute values
  ATTR_DEFAULTS = {
    :host => nil,
    :port => nil,
    :version => '3.1.1',
    :keep_alive => 15,
    :clean_session => true,
    :client_id => nil,
    :ack_timeout => 5,
    :username => nil,
    :password => nil,
    :will_topic => nil,
    :will_payload => nil,
    :will_qos => 0,
    :will_retain => false,
    :ssl => false
  }

  # Create and connect a new MQTT Client
  #
  # Accepts the same arguments as creating a new client.
  # If a block is given, then it will be executed before disconnecting again.
  #
  # Example:
  #  MQTT::Client.connect('myserver.example.com') do |client|
  #    # do stuff here
  #  end
  #
  def self.connect(*args, &block)
    client = MQTT::Client.new(*args)
    client.connect(&block)
    return client
  end

  # Generate a random client identifier
  # (using the characters 0-9 and a-z)
  def self.generate_client_id(prefix='ruby', length=16)
    str = prefix.dup
    length.times do
      num = rand(36)
      if (num<10)
        # Number
        num += 48
      else
        # Letter
        num += 87
      end
      str += num.chr
    end
    return str
  end

  # Create a new MQTT Client instance
  #
  # Accepts one of the following:
  # - a URI that uses the MQTT scheme
  # - a hostname and port
  # - a Hash containing attributes to be set on the new instance
  #
  # If no arguments are given then the method will look for a URI
  # in the MQTT_SERVER environment variable.
  #
  # Examples:
  #  client = MQTT::Client.new
  #  client = MQTT::Client.new('mqtt://myserver.example.com')
  #  client = MQTT::Client.new('mqtt://user:pass@myserver.example.com')
  #  client = MQTT::Client.new('myserver.example.com')
  #  client = MQTT::Client.new('myserver.example.com', 18830)
  #  client = MQTT::Client.new(:host => 'myserver.example.com')
  #  client = MQTT::Client.new(:host => 'myserver.example.com', :keep_alive => 30)
  #
  def initialize(*args)
    if args.last.is_a?(Hash)
      attr = args.pop
    else
      attr = {}
    end

    if args.length == 0
      if ENV['MQTT_SERVER']
        attr.merge!(parse_uri(ENV['MQTT_SERVER']))
      end
    end

    if args.length >= 1
      case args[0]
        when URI
          attr.merge!(parse_uri(args[0]))
        when %r|^mqtts?://|
          attr.merge!(parse_uri(args[0]))
        else
          attr.merge!(:host => args[0])
      end
    end

    if args.length >= 2
      attr.merge!(:port => args[1]) unless args[1].nil?
    end

    if args.length >= 3
      raise ArgumentError, "Unsupported number of arguments"
    end

    # Merge arguments with default values for attributes
    ATTR_DEFAULTS.merge(attr).each_pair do |k,v|
      self.send("#{k}=", v)
    end

    # Set a default port number
    if @port.nil?
      @port = @ssl ? MQTT::DEFAULT_SSL_PORT : MQTT::DEFAULT_PORT
    end

    # Initialise private instance variables
    @last_ping_request = Time.now
    @last_ping_response = Time.now
    @socket = nil
    @read_queue = Queue.new
    @pubacks = {}
    @read_thread = nil
    @write_semaphore = Mutex.new
    @pubacks_semaphore = Mutex.new
  end

  # Get the OpenSSL context, that is used if SSL/TLS is enabled
  def ssl_context
    @ssl_context ||= OpenSSL::SSL::SSLContext.new
  end

  # Set a path to a file containing a PEM-format client certificate
  def cert_file=(path)
    self.cert = File.read(path)
  end

  # PEM-format client certificate
  def cert=(cert)
    ssl_context.cert = OpenSSL::X509::Certificate.new(cert)
  end

  # Set a path to a file containing a PEM-format client private key
  def key_file=(*args)
    path, passphrase = args.flatten
    ssl_context.key = OpenSSL::PKey::RSA.new(File.open(path), passphrase)
  end

  # Set to a PEM-format client private key
  def key=(*args)
    cert, passphrase = args.flatten
    ssl_context.key = OpenSSL::PKey::RSA.new(cert, passphrase)
  end

  # Set a path to a file containing a PEM-format CA certificate and enable peer verification
  def ca_file=(path)
    ssl_context.ca_file = path
    unless path.nil?
      ssl_context.verify_mode = OpenSSL::SSL::VERIFY_PEER
    end
  end

  # Set the Will for the client
  #
  # The will is a message that will be delivered by the server when the client dies.
  # The Will must be set before establishing a connection to the server
  def set_will(topic, payload, retain=false, qos=0)
    self.will_topic = topic
    self.will_payload = payload
    self.will_retain = retain
    self.will_qos = qos
  end

  # Connect to the MQTT server
  # If a block is given, then yield to that block and then disconnect again.
  def connect(clientid=nil)
    unless clientid.nil?
      @client_id = clientid
    end

    if @client_id.nil? or @client_id.empty?
      if @clean_session
        if @version == '3.1.0'
          # Empty client id is not allowed for version 3.1.0
          @client_id = MQTT::Client.generate_client_id
        end
      else
        raise 'Must provide a client_id if clean_session is set to false'
      end
    end

    if @host.nil?
      raise 'No MQTT server host set when attempting to connect'
    end

    if not connected?
      # Create network socket
      tcp_socket = TCPSocket.new(@host, @port)

      if @ssl
        # Set the protocol version
        if @ssl.is_a?(Symbol)
          ssl_context.ssl_version = @ssl
        end

        @socket = OpenSSL::SSL::SSLSocket.new(tcp_socket, ssl_context)
        @socket.sync_close = true

        # Set hostname on secure socket for Server Name Indication (SNI)
        if @socket.respond_to?(:hostname=)
          @socket.hostname = @host
        end

        @socket.connect
      else
        @socket = tcp_socket
      end

      # Construct a connect packet
      packet = MQTT::Packet::Connect.new(
        :version => @version,
        :clean_session => @clean_session,
        :keep_alive => @keep_alive,
        :client_id => @client_id,
        :username => @username,
        :password => @password,
        :will_topic => @will_topic,
        :will_payload => @will_payload,
        :will_qos => @will_qos,
        :will_retain => @will_retain
      )

      # Send packet
      send_packet(packet)

      # Receive response
      receive_connack

      # Start packet reading thread
      @read_thread = Thread.new(Thread.current) do |parent|
        Thread.current[:parent] = parent
        while connected? do
          receive_packet
        end
      end
    end

    # If a block is given, then yield and disconnect
    if block_given?
      begin
        yield(self)
      ensure
        disconnect
      end
    end
  end

  # Disconnect from the MQTT server.
  # If you don't want to say goodbye to the server, set send_msg to false.
  def disconnect(send_msg=true)
    # Stop reading packets from the socket first
    @read_thread.kill if @read_thread and @read_thread.alive?
    @read_thread = nil

    # Close the socket if it is open
    if connected?
      if send_msg
        packet = MQTT::Packet::Disconnect.new
        send_packet(packet)
      end
      @socket.close unless @socket.nil?
      @socket = nil
    end
  end

  # Checks whether the client is connected to the server.
  def connected?
    (not @socket.nil?) and (not @socket.closed?)
  end

  # Publish a message on a particular topic to the MQTT server.
  def publish(topic, payload='', retain=false, qos=0)
    raise ArgumentError.new("Topic name cannot be nil") if topic.nil?
    raise ArgumentError.new("Topic name cannot be empty") if topic.empty?

    packet = MQTT::Packet::Publish.new(
      :id => next_packet_id,
      :qos => qos,
      :retain => retain,
      :topic => topic,
      :payload => payload
    )

    # Send the packet
    res = send_packet(packet)

    if packet.qos > 0
      Timeout.timeout(@ack_timeout) do
        while connected? do
          @pubacks_semaphore.synchronize do
            return res if @pubacks.delete(packet.id)
          end
          # FIXME: make threads communicate with each other, instead of polling
          # (using a pipe and select ?)
          sleep 0.01
        end
      end
      return -1
    end
  end

  # Send a subscribe message for one or more topics on the MQTT server.
  # 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:
  #   client.subscribe( 'a/b' )
  #   client.subscribe( 'a/b', 'c/d' )
  #   client.subscribe( ['a/b',0], ['c/d',1] )
  #   client.subscribe( 'a/b' => 0, 'c/d' => 1 )
  #
  def subscribe(*topics)
    packet = MQTT::Packet::Subscribe.new(
      :id => next_packet_id,
      :topics => topics
    )
    send_packet(packet)
  end

  # Return the next message received from the MQTT server.
  # An optional topic can be given to subscribe to.
  #
  # The method either returns the topic and message as an array:
  #   topic,message = client.get
  #
  # Or can be used with a block to keep processing messages:
  #   client.get('test') do |topic,payload|
  #     # Do stuff here
  #   end
  #
  def get(topic=nil, options={})
    if block_given?
      get_packet(topic) do |packet|
        yield(packet.topic, packet.payload) unless packet.retain && options[:omit_retained]
      end
    else
      loop do
        # Wait for one packet to be available
        packet = get_packet(topic)
        return packet.topic, packet.payload unless packet.retain && options[:omit_retained]
      end
    end
  end

  # Return the next packet object received from the MQTT server.
  # An optional topic can be given to subscribe to.
  #
  # The method either returns a single packet:
  #   packet = client.get_packet
  #   puts packet.topic
  #
  # Or can be used with a block to keep processing messages:
  #   client.get_packet('test') do |packet|
  #     # Do stuff here
  #     puts packet.topic
  #   end
  #
  def get_packet(topic=nil)
    # Subscribe to a topic, if an argument is given
    subscribe(topic) unless topic.nil?

    if block_given?
      # Loop forever!
      loop do
        packet = @read_queue.pop
        yield(packet)
        puback_packet(packet) if packet.qos > 0
      end
    else
      # Wait for one packet to be available
      packet = @read_queue.pop
      puback_packet(packet) if packet.qos > 0
      return packet
    end
  end

  # Returns true if the incoming message queue is empty.
  def queue_empty?
    @read_queue.empty?
  end

  # Returns the length of the incoming message queue.
  def queue_length
    @read_queue.length
  end

  # Send a unsubscribe message for one or more topics on the MQTT server
  def unsubscribe(*topics)
    if topics.is_a?(Enumerable) and topics.count == 1
      topics = topics.first
    end

    packet = MQTT::Packet::Unsubscribe.new(
      :topics => topics,
      :id => next_packet_id
    )
    send_packet(packet)
  end

private

  # Try to read a packet from the server
  # Also sends keep-alive ping packets.
  def receive_packet
    begin
      # Poll socket - is there data waiting?
      result = IO.select([@socket], [], [], SELECT_TIMEOUT)
      unless result.nil?
        # Yes - read in the packet
        packet = MQTT::Packet.read(@socket)
        handle_packet packet
      end
      keep_alive!
    # Pass exceptions up to parent thread
    rescue Exception => exp
      unless @socket.nil?
        @socket.close
        @socket = nil
      end
      Thread.current[:parent].raise(exp)
    end
  end

  def handle_packet(packet)
    if packet.class == MQTT::Packet::Publish
      # Add to queue
      @read_queue.push(packet)
    elsif packet.class == MQTT::Packet::Pingresp
      @last_ping_response = Time.now
    elsif packet.class == MQTT::Packet::Puback
      @pubacks_semaphore.synchronize do
        @pubacks[packet.id] = packet
      end
    end
    # Ignore all other packets
    # FIXME: implement responses for QoS  2
  end

  def keep_alive!
    if @keep_alive > 0 && connected?
      response_timeout = (@keep_alive * 1.5).ceil
      if Time.now >= @last_ping_request + @keep_alive
        packet = MQTT::Packet::Pingreq.new
        send_packet(packet)
        @last_ping_request = Time.now
      elsif Time.now > @last_ping_response + response_timeout
        raise MQTT::ProtocolException.new(
          "No Ping Response received for #{response_timeout} seconds"
        )
      end
    end
  end

  def puback_packet(packet)
    send_packet(MQTT::Packet::Puback.new :id => packet.id)
  end

  # Read and check a connection acknowledgement packet
  def receive_connack
    Timeout.timeout(@ack_timeout) do
      packet = MQTT::Packet.read(@socket)
      if packet.class != MQTT::Packet::Connack
        raise MQTT::ProtocolException.new(
          "Response wasn't a connection acknowledgement: #{packet.class}"
        )
      end

      # Check the return code
      if packet.return_code != 0x00
        # 3.2.2.3 If a server sends a CONNACK packet containing a non-zero
        # return code it MUST then close the Network Connection
        @socket.close
        raise MQTT::ProtocolException.new(packet.return_msg)
      end
    end
  end

  # Send a packet to server
  def send_packet(data)
    # Raise exception if we aren't connected
    raise MQTT::NotConnectedException if not connected?

    # Only allow one thread to write to socket at a time
    @write_semaphore.synchronize do
      @socket.write(data.to_s)
    end
  end

  private
  def parse_uri(uri)
    uri = URI.parse(uri) unless uri.is_a?(URI)
    if uri.scheme == 'mqtt'
      ssl = false
    elsif uri.scheme == 'mqtts'
      ssl = true
    else
      raise "Only the mqtt:// and mqtts:// schemes are supported"
    end

    {
      :host => uri.host,
      :port => uri.port || nil,
      :username => uri.user ? URI.unescape(uri.user) : nil,
      :password => uri.password ? URI.unescape(uri.password) : nil,
      :ssl => ssl
    }
  end

  def next_packet_id
    @last_packet_id = ( @last_packet_id || 0 ).next
  end

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

  # @deprecated Please use {#host} instead
  def remote_host
    host
  end

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

  # @deprecated Please use {#port} instead
  def remote_port
    port
  end

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

end