text: # -*- coding: utf-8 -*-
  """
  h2/config
  ~~~~~~~~~
  
  Objects for controlling the configuration of the HTTP/2 stack.
  """
  
  
  class _BooleanConfigOption(object):
      """
      Descriptor for handling a boolean config option.  This will block
      attempts to set boolean config options to non-bools.
      """
      def __init__(self, name):
          self.name = name
          self.attr_name = '_%s' % self.name
  
      def __get__(self, instance, owner):
          return getattr(instance, self.attr_name)
  
      def __set__(self, instance, value):
          if not isinstance(value, bool):
              raise ValueError("%s must be a bool" % self.name)
          setattr(instance, self.attr_name, value)
  
  
  class DummyLogger(object):
      """
      An Logger object that does not actual logging, hence a DummyLogger.
  
      For the class the log operation is merely a no-op.  The intent is to avoid
      conditionals being sprinkled throughout the hyper-h2 code for calls to
      logging functions when no logger is passed into the corresponding object.
      """
      def __init__(self, *vargs):
          pass
  
      def debug(self, *vargs, **kwargs):
          """
          No-op logging. Only level needed for now.
          """
          pass
  
  
  class H2Configuration(object):
      """
      An object that controls the way a single HTTP/2 connection behaves.
  
      This object allows the users to customize behaviour. In particular, it
      allows users to enable or disable optional features, or to otherwise handle
      various unusual behaviours.
  
      This object has very little behaviour of its own: it mostly just ensures
      that configuration is self-consistent.
  
      :param client_side: Whether this object is to be used on the client side of
          a connection, or on the server side. Affects the logic used by the
          state machine, the default settings values, the allowable stream IDs,
          and several other properties. Defaults to ``True``.
      :type client_side: ``bool``
  
      :param header_encoding: Controls whether the headers emitted by this object
          in events are transparently decoded to ``unicode`` strings, and what
          encoding is used to do that decoding. This defaults to ``None``,
          meaning that headers will be returned as bytes. To automatically
          decode headers (that is, to return them as unicode strings), this can
          be set to the string name of any encoding, e.g. ``'utf-8'``.
  
          .. versionchanged:: 3.0.0
             Changed default value from ``'utf-8'`` to ``None``
  
      :type header_encoding: ``str``, ``False``, or ``None``
  
      :param validate_outbound_headers: Controls whether the headers emitted
          by this object are validated against the rules in RFC 7540.
          Disabling this setting will cause outbound header validation to
          be skipped, and allow the object to emit headers that may be illegal
          according to RFC 7540. Defaults to ``True``.
      :type validate_outbound_headers: ``bool``
  
      :param normalize_outbound_headers: Controls whether the headers emitted
          by this object are normalized before sending.  Disabling this setting
          will cause outbound header normalization to be skipped, and allow
          the object to emit headers that may be illegal according to
          RFC 7540. Defaults to ``True``.
      :type normalize_outbound_headers: ``bool``
  
      :param validate_inbound_headers: Controls whether the headers received
          by this object are validated against the rules in RFC 7540.
          Disabling this setting will cause inbound header validation to
          be skipped, and allow the object to receive headers that may be illegal
          according to RFC 7540. Defaults to ``True``.
      :type validate_inbound_headers: ``bool``
  
      :param normalize_inbound_headers: Controls whether the headers received by
          this object are normalized according to the rules of RFC 7540.
          Disabling this setting may lead to hyper-h2 emitting header blocks that
          some RFCs forbid, e.g. with multiple cookie fields.
  
          .. versionadded:: 3.0.0
  
      :type normalize_inbound_headers: ``bool``
  
      :param logger: A logger that conforms to the requirements for this module,
          those being no I/O and no context switches, which is needed in order
          to run in asynchronous operation.
  
          .. versionadded:: 2.6.0
  
      :type logger: ``logging.Logger``
      """
      client_side = _BooleanConfigOption('client_side')
      validate_outbound_headers = _BooleanConfigOption(
          'validate_outbound_headers'
      )
      normalize_outbound_headers = _BooleanConfigOption(
          'normalize_outbound_headers'
      )
      validate_inbound_headers = _BooleanConfigOption(
          'validate_inbound_headers'
      )
      normalize_inbound_headers = _BooleanConfigOption(
          'normalize_inbound_headers'
      )
  
      def __init__(self,
                   client_side=True,
                   header_encoding=None,
                   validate_outbound_headers=True,
                   normalize_outbound_headers=True,
                   validate_inbound_headers=True,
                   normalize_inbound_headers=True,
                   logger=None):
          self.client_side = client_side
          self.header_encoding = header_encoding
          self.validate_outbound_headers = validate_outbound_headers
          self.normalize_outbound_headers = normalize_outbound_headers
          self.validate_inbound_headers = validate_inbound_headers
          self.normalize_inbound_headers = normalize_inbound_headers
          self.logger = logger or DummyLogger(__name__)
  
      @property
      def header_encoding(self):
          """
          Controls whether the headers emitted by this object in events are
          transparently decoded to ``unicode`` strings, and what encoding is used
          to do that decoding. This defaults to ``None``, meaning that headers
          will be returned as bytes. To automatically decode headers (that is, to
          return them as unicode strings), this can be set to the string name of
          any encoding, e.g. ``'utf-8'``.
          """
          return self._header_encoding
  
      @header_encoding.setter
      def header_encoding(self, value):
          """
          Enforces constraints on the value of header encoding.
          """
          if not isinstance(value, (bool, str, type(None))):
              raise ValueError("header_encoding must be bool, string, or None")
          if value is True:
              raise ValueError("header_encoding cannot be True")
          self._header_encoding = value
  