module ChefConfig::Mixin::TrainTransport

def build_transport
  return nil unless config.target_mode?
  # TODO: Consider supporting parsing the protocol from a URI passed to `--target`
  #
  train_config = {}
  # Load the target_mode config context from config, and place any valid settings into the train configuration
  tm_config = config.target_mode
  protocol = tm_config.protocol
  train_config = tm_config.to_hash.select { |k| Train.options(protocol).key?(k) }
  logger.trace("Using target mode options from #{ChefUtils::Dist::Infra::PRODUCT} config file: #{train_config.keys.join(", ")}") if train_config
  # Load the credentials file, and place any valid settings into the train configuration
  credentials = load_credentials(tm_config.host)
  if credentials
    valid_settings = credentials.select { |k| Train.options(protocol).key?(k) }
    valid_settings[:enable_password] = credentials[:enable_password] if credentials.key?(:enable_password)
    train_config.merge!(valid_settings)
    logger.trace("Using target mode options from credentials file: #{valid_settings.keys.join(", ")}") if valid_settings
  end
  train_config[:logger] = logger
  # Train handles connection retries for us
  Train.create(protocol, train_config)
rescue SocketError => e # likely a dns failure, not caught by train
  e.message.replace "Error connecting to #{train_config[:target]} - #{e.message}"
  raise e
rescue Train::PluginLoadError
  logger.error("Invalid target mode protocol: #{protocol}")
  exit(1)
end