text: # Copyright 2020 Red Hat Inc.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Utility functions for output modules."""
  
  import socket
  from socket import error as socket_error
  
  from mrack.utils import find_value_in_config_hierarchy
  
  
  def resolve_hostname(ip_addr):
      """Resolve IP address to hostname."""
      try:
          return socket.gethostbyaddr(ip_addr)[0]
      except socket_error:
          return None
  
  
  def get_external_id(host, meta_host, config):
      """
      Get host's external ID.
  
      That can be its resolvable DNS name (from IP) or the IP - based on provider or
      host configuration (key: resolve_host, default True).
  
      IP is used as fallback if the desired is not available.
      """
      resolve_ip = find_value_in_config_hierarchy(
          config, host.provider.name, host, meta_host, "resolve_host", None, None, True
      )
  
      external_id = host.ip_addr
      if resolve_ip:
          external_id = resolve_hostname(host.ip_addr) or host.ip_addr
      return external_id
  