# encoding: utf-8
require "moped/connection/manager"
require "moped/connection/sockets"

module Moped
  # This class contains behaviour of database socket connections.
  #
  # @since 2.0.0
  class Connection
    include Authenticatable

    # The default connection timeout, in seconds.
    #
    # @since 2.0.0
    TIMEOUT = 5

    REPLY_DECODE_STR = 'l<5q<l<2'

    # @!attribute host
    #   @return [ String ] The ip address of the host.
    # @!attribute options
    #   @return [ Hash ] The connection options.
    # @!attribute port
    #   @return [ String ] The port the connection connects on.
    # @!attribute timeout
    #   @return [ Integer ] The timeout in seconds.
    attr_reader :host, :options, :port, :timeout

    # Is the connection alive?
    #
    # @example Is the connection alive?
    #   connection.alive?
    #
    # @return [ true, false ] If the connection is alive.
    #
    # @since 1.0.0
    def alive?
      connected? ? @sock.alive? : false
    end

    # Connect to the server defined by @host, @port without timeout @timeout.
    #
    # @example Open the connection
    #   connection.connect
    #
    # @return [ TCPSocket ] The socket.
    #
    # @since 1.0.0
    def connect
      credentials.clear
      @sock = if !!options[:ssl]
        Socket::SSL.connect(host, port, timeout)
      else
        Socket::TCP.connect(host, port, timeout)
      end
    end

    # Is the connection connected?
    #
    # @example Is the connection connected?
    #   connection.connected?
    #
    # @return [ true, false ] If the connection is connected.
    #
    # @since 1.0.0
    def connected?
      !!@sock
    end

    # Disconnect from the server.
    #
    # @example Disconnect from the server.
    #   connection.disconnect
    #
    # @return [ nil ] nil.
    #
    # @since 1.0.0
    def disconnect
      @sock.close
    rescue
    ensure
      @sock = nil
    end

    # Initialize the connection.
    #
    # @example Initialize the connection.
    #   Connection.new("localhost", 27017, 5)
    #
    # @param [ String ] host The host to connect to.
    # @param [ Integer ] post The server port.
    # @param [ Integer ] timeout The connection timeout.
    # @param [ Hash ] options Options for the connection.
    #
    # @option options [ Boolean ] :ssl Connect using SSL
    # @since 1.0.0
    def initialize(host, port, timeout, options = {})
      @host = host
      @port = port
      @timeout = timeout
      @options = options
      @sock = nil
      @request_id = 0
    end

    # Read from the connection.
    #
    # @example Read from the connection.
    #   connection.read
    #
    # @return [ Hash ] The returned document.
    #
    # @since 1.0.0
    def read
      with_connection do |socket|
        reply = Protocol::Reply.allocate
        data = read_data(socket, 36)
        response = data.unpack(REPLY_DECODE_STR)
        reply.length,
          reply.request_id,
          reply.response_to,
          reply.op_code,
          reply.flags,
          reply.cursor_id,
          reply.offset,
          reply.count = response

        if reply.count == 0
          reply.documents = []
        else
          sock_read = read_data(socket, reply.length - 36)
          buffer = StringIO.new(sock_read)
          reply.documents = reply.count.times.map do
            ::BSON::Document.from_bson(buffer)
          end
        end
        reply
      end
    end

    # Get the replies to the database operation.
    #
    # @example Get the replies.
    #   connection.receive_replies(operations)
    #
    # @param [ Array<Message> ] operations The query or get more ops.
    #
    # @return [ Array<Hash> ] The returned deserialized documents.
    #
    # @since 1.0.0
    def receive_replies(operations)
      operations.map do |operation|
        operation.receive_replies(self)
      end
    end

    # Write to the connection.
    #
    # @example Write to the connection.
    #   connection.write(data)
    #
    # @param [ Array<Message> ] operations The database operations.
    #
    # @return [ Integer ] The number of bytes written.
    #
    # @since 1.0.0
    def write(operations)
      buf = ""
      operations.each do |operation|
        operation.request_id = (@request_id += 1)
        operation.serialize(buf)
      end
      with_connection do |socket|
        socket.write(buf)
      end
    end

    private

    # Read data from the socket until we get back the number of bytes that we
    # are expecting.
    #
    # @api private
    #
    # @example Read the number of bytes.
    #   connection.read_data(socket, 36)
    #
    # @param [ TCPSocket ] socket The socket to read from.
    # @param [ Integer ] length The number of bytes to read.
    #
    # @return [ String ] The read data.
    #
    # @since 1.2.9
    def read_data(socket, length)
      data = socket.read(length)
      unless data
        raise Errors::ConnectionFailure.new(
          "Attempted to read #{length} bytes from the socket but nothing was returned."
        )
      end
      if data.length < length
        data << read_data(socket, length - data.length)
      end
      data
    end

    # Yields a connected socket to the calling back. It will attempt to reconnect
    # the socket if it is not connected.
    #
    # @api private
    #
    # @example Write to the connection.
    #   with_connection do |socket|
    #     socket.write(buf)
    #   end
    #
    # @return The yielded block
    #
    # @since 1.3.0
    def with_connection
      if @sock.nil? || !@sock.alive?
        connect
        apply_credentials(@original_credentials || {})
      end
      yield @sock
    end
  end
end