newcontext-oss/kitchen-terraform

# frozen_string_literal: true

# Copyright 2016-2021 Copado NCS LLC
#
# 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.

module Kitchen
  module Terraform
    # Behaviour to cache configuration attribute lookups.
    module ConfigAttributeCacher
      # A callback to define an attribute lookup cache which is invoked when this module is extended by a
      # configuration attribute.
      #
      # @param configuration_attribute [::Kitchen::Terraform::ConfigAttribute] a configuration attribute.
      # @return [void]
      def self.extended(configuration_attribute)
        configuration_attribute.define_cache
      end

      # Defines an instance method named "config_<attribute_name>" which caches the value of the configuration attribute
      # lookup using an equivalently named instance variable.
      #
      # @param attribute_name [Symbol] the name of the attribute
      def define_cache(attribute_name: to_sym)
        define_method "config_#{attribute_name}" do
          instance_variable_defined? "@config_#{attribute_name}" and
            instance_variable_get "@config_#{attribute_name}" or
            instance_variable_set(
              "@config_#{attribute_name}",
              config.fetch(attribute_name)
            )
        end
      end
    end
  end
end