require 'hashconfig'
require 'fileutils'

module Junkie

  # Module that encapsulates the handling for configuration into a module
  # which can be included into any Class which includes a constant Hash named
  # DEFAULT_CONFIG is returned by Config.get_config(self) merged with the
  # version from the config file
  #
  # @example
  #   class Foo
  #     include Config
  #
  #     DEFAULT_CONFIG = { refresh: 5 }
  #
  #     def initialize
  #       # the following holds the merged version from DEFAULT_CONFIG
  #       @config = Config.get_config(self)
  #     end
  #   end
  #
  module Config
    @including_classes = []
    @comlete_config = nil

    # Callback method which is called when a class includes the module
    #
    # @param [Class] the class which includes the module
    def self.included(mod)
      @including_classes << mod
    end


    # Get the config hash for the calling module merged with the hash from the
    # config file
    #
    # @param [Class] should be equal to `self`
    # @return [Hash] merged version of DEFAULT_CONFIG from the calling class
    def self.get_config(source)

      # builds up the complete config and merges them with serialzed version
      # at the first call to this method
      if @comlete_config.nil?
        default_config = self.collect_default_configs

        FileUtils.mkdir_p File.dirname(Junkie::CONFIG_FILE)
        @comlete_config =
          default_config.merge_with_serialized(Junkie::CONFIG_FILE)
      end

      return @comlete_config[source.class.to_s]
    end


    # Collects the DEFAULT_CONFIG from all including Classes
    #
    # @return [Hash] hash of hashes indexed by class name
    def self.collect_default_configs
      config = Hash.new

      @including_classes.each do |klass|
        if not klass.const_defined? :DEFAULT_CONFIG
          raise NotImplementedError,
            "#{klass} has to include a constant DEFAULT_CONFIG as Hash"
        end

        config[klass.to_s] = klass.const_get :DEFAULT_CONFIG
      end

      config
    end

  end
end