module Vedeu

  # When included into a class, provides the mechanism to store the class in a
  # repository for later retrieval.
  #
  # @api private
  module Model

    attr_reader :repository

    module ClassMethods

      # Build models using a simple DSL when a block is given, otherwise returns
      # a new instance of the class including this module.
      #
      # @param attributes [Hash] A collection of attributes specific to the
      #   model.
      # @param block [Proc] The block passed to the build method.
      # @return [Object] An instance of the model.
      def build(attributes = {}, &block)
        attributes = defaults.merge(attributes)

        model = new(attributes)
        model.deputy(attributes[:client]).instance_eval(&block) if block_given?
        model
      end

      # Provide a convenient way to define the child or children of a model.
      #
      # @param klass [Class] The member (singular) or collection (multiple)
      #   class name for the respective model.
      # @return []
      def child(klass)
        send(:define_method, __callee__) { klass }
      end
      alias_method :member,     :child
      alias_method :collection, :child

      private

      # The default values for a new instance of this class.
      #
      # @return [Hash]
      def defaults
        {
          client:    nil,
          name:      '',
        }
      end

    end # ClassMethods

    # When this module is included in a class, provide ClassMethods as class
    # methods for the class.
    #
    # @param klass [Class]
    def self.included(klass)
      klass.send :extend, ClassMethods
    end

    # Returns a DSL instance responsible for defining the DSL methods of this
    # model.
    #
    # @param client [Object|NilClass] The client binding represents
    #   the client application object that is currently invoking a DSL method.
    #   It is required so that we can send messages to the client application
    #   object should we need to.
    # @return [void] The DSL instance for this model.
    def deputy(client = nil)
      Object.const_get(dsl_class).new(self, client)
    end

    # @todo Perhaps some validation could be added here?
    # @return [void] The model instance stored in the repository.
    def store
      repository.store(self) # if valid?
    end

    private

    # Removes the module part from the expression in the string.
    #
    # @example
    #   demodulize('Vedeu::DSL::Interface') # => "Interface"
    #
    # @param klass [Class|String]
    def demodulize(klass)
      klass = klass.to_s

      klass[(klass.rindex('::') + 2)..-1]
    end

    # Returns the DSL class name responsible for this model.
    #
    # @return [String]
    def dsl_class
      'Vedeu::DSL::' + demodulize(self.class.name)
    end

  end # Model

end # Vedeu