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"""Common code used throughout tests of gRPC."""

import collections

import grpc
import six

INVOCATION_INITIAL_METADATA = (('0', 'abc'), ('1', 'def'), ('2', 'ghi'),)
SERVICE_INITIAL_METADATA = (('3', 'jkl'), ('4', 'mno'), ('5', 'pqr'),)
SERVICE_TERMINAL_METADATA = (('6', 'stu'), ('7', 'vwx'), ('8', 'yza'),)
DETAILS = 'test details'


def metadata_transmitted(original_metadata, transmitted_metadata):
  """Judges whether or not metadata was acceptably transmitted.

  gRPC is allowed to insert key-value pairs into the metadata values given by
  applications and to reorder key-value pairs with different keys but it is not
  allowed to alter existing key-value pairs or to reorder key-value pairs with
  the same key.

  Args:
    original_metadata: A metadata value used in a test of gRPC. An iterable over
      iterables of length 2.
    transmitted_metadata: A metadata value corresponding to original_metadata
      after having been transmitted via gRPC. An iterable over iterables of
      length 2.

  Returns:
     A boolean indicating whether transmitted_metadata accurately reflects
      original_metadata after having been transmitted via gRPC.
  """
  original = collections.defaultdict(list)
  for key, value in original_metadata:
    original[key].append(value)
  transmitted = collections.defaultdict(list)
  for key, value in transmitted_metadata:
    transmitted[key].append(value)

  for key, values in six.iteritems(original):
    transmitted_values = transmitted[key]
    transmitted_iterator = iter(transmitted_values)
    try:
      for value in values:
        while True:
          transmitted_value = next(transmitted_iterator)
          if value == transmitted_value:
            break
    except StopIteration:
      return False
  else:
    return True


def test_secure_channel(
    target, channel_credentials, server_host_override):
  """Creates an insecure Channel to a remote host.

  Args:
    host: The name of the remote host to which to connect.
    port: The port of the remote host to which to connect.
    channel_credentials: The implementations.ChannelCredentials with which to
      connect.
    server_host_override: The target name used for SSL host name checking.

  Returns:
    An implementations.Channel to the remote host through which RPCs may be
      conducted.
  """
  channel = grpc.secure_channel(
      target, channel_credentials,
      (('grpc.ssl_target_name_override', server_host_override,),))
  return channel