module ZMQ

  # General utility methods.
  #
  class Util

    # Generate and return a CURVE public/private keypair
    #
    # Raises an error if ZeroMQ is not configured for CURVE connections.
    # Install libsodium if this is the case.
    def self.curve_keypair
      public_key = FFI::MemoryPointer.from_string(' ' * 41)
      private_key = FFI::MemoryPointer.from_string(' ' * 41)
      rc = LibZMQ.zmq_curve_keypair public_key, private_key

      if rc < 0
        raise NotSupportedError.new "zmq_curve_keypair" , rc, ZMQ::Util.errno,
          "Rebuild zeromq with libsodium to enable CURVE security options."
      end

      [public_key.read_string, private_key.read_string]
    end

    # Returns true when +rc+ is greater than or equal to 0, false otherwise.
    #
    # We use the >= test because zmq_poll() returns the number of sockets
    # that had a read or write event triggered. So, a >= 0 result means
    # it succeeded.
    #
    def self.resultcode_ok? rc
      rc >= 0
    end

    # Returns the +errno+ as set by the libzmq library.
    #
    def self.errno
      LibZMQ.zmq_errno
    end

    # Returns a string corresponding to the currently set #errno. These
    # error strings are defined by libzmq.
    #
    def self.error_string
      LibZMQ.zmq_strerror(errno).read_string
    end

    # Attempts to bind to a random tcp port on +host+ up to +max_tries+
    # times. Returns the port number upon success or nil upon failure.
    #
    def self.bind_to_random_tcp_port host = '127.0.0.1', max_tries = 500
      tries = 0
      rc = -1

      while !resultcode_ok?(rc) && tries < max_tries
        tries += 1
        random = random_port
        rc = socket.bind "tcp://#{host}:#{random}"
      end

      resultcode_ok?(rc) ? random : nil
    end

    # :doc:
    # Called to verify whether there were any errors during
    # operation. If any are found, raise the appropriate #ZeroMQError.
    #
    # When no error is found, this method returns +true+ which is behavior
    # used internally by #send and #recv.
    #
    def self.error_check source, result_code
      if -1 == result_code
        raise_error source, result_code
      end

      # used by Socket::send/recv, ignored by others
      true
    end


    private

    # generate a random port between 10_000 and 65534
    def self.random_port
      rand(55534) + 10_000
    end

    def self.raise_error source, result_code
      if context_error?(source)
        raise ContextError.new source, result_code, ZMQ::Util.errno, ZMQ::Util.error_string

      elsif message_error?(source)
        raise MessageError.new source, result_code, ZMQ::Util.errno, ZMQ::Util.error_string

      else
        raise ZeroMQError.new source, result_code, -1,
          "Source [#{source}] does not match any zmq_* strings, rc [#{result_code}], errno [#{ZMQ::Util.errno}], error_string [#{ZMQ::Util.error_string}]"
      end
    end

    def self.eagain?
      EAGAIN == ZMQ::Util.errno
    end

    def self.context_error?(source)
      'zmq_ctx_new' == source ||
        'zmq_ctx_set' == source ||
        'zmq_ctx_get' == source ||
        'zmq_ctx_destory' == source ||
        'zmq_ctx_set_monitor' == source
    end

    def self.message_error?(source)
      ['zmq_msg_init', 'zmq_msg_init_data', 'zmq_msg_copy', 'zmq_msg_move', 'zmq_msg_close', 'zmq_msg_get',
       'zmq_msg_more', 'zmq_msg_recv', 'zmq_msg_send', 'zmq_msg_set'].include?(source)
    end

  end # module Util

end # module ZMQ