# encoding: utf-8

module Hexx

  # @api hide
  # The module contains helper classes and modules.
  #
  # All the helpers injects some code into corresponding class or module.
  #
  # The content of the module is not a part of API, but its implementation
  # details.
  module Helpers

    # @api hide
    # @abstract
    # The base class for attribute injection.
    #
    # The objects of the class validates its parameters and adds
    # attribute's getter and setter into the target class or module.
    class Base < Struct.new(:target, :name)

      # @api hide
      # @!method add(target, name)
      # Injects an attribute to the target class.
      #
      # @param  [Module] target The class or module to inject the attribute to.
      # @param  [String, Symbol] name The name of the attribute.
      # @raise  (see Hexx::Helpers::Base#validate)
      # @return [Hexx::Helpers::Base] the base class object.
      def self.add(*args)
        new(*args).validate.add_getter.add_setter
      end

      # @api hide
      # @!attribute target
      # The class to inject the attribute to
      # @return [Class] the target for the injection

      # @api hide
      # @!attribute name
      # The name of the attribute to be created in a target class
      # @return [Class] the name of the attribute

      # @api hide
      # Validates parameters of the dependency declaration.
      #
      # @raise  (see Hexx::Helpers::Base#check_target)
      # @raise  (see Hexx::Helpers::Base#check_name_type)
      # @raise  (see Hexx::Helpers::Base#check_name_value)
      # @return [Hexx::Helpers::Base] +self+
      def validate
        check_target
        check_name_type
        check_name_value
        self
      end

      # @api hide
      # Adds the parameter getter to the +target+ instance
      # @return [Hexx::Helpers::Base] +self+
      def add_getter
        target.class_eval getter
        self
      end

      # @api hide
      # Adds the parameter setter to the +target+ instance
      # @return [Hexx::Helpers::Base] +self+
      def add_setter
        target.class_eval setter
        self
      end

      private

      # @abstract
      # @return [String] the getter definition
      def getter
        ""
      end

      # @abstract
      # @return [String] the setter definition
      def setter
        ""
      end

      # @api hide
      # @raise [TypeError] if a target to add the instance parameter to
      #   is not a class.
      def check_target
        return if target.is_a? Class
        fail TypeError.new "#{ target.inspect } is not a class"
      end

      # @api hide
      # @raise [TypeError] if the attribute name is neither a string nor symbol.
      def check_name_type
        return if name.is_a?(String) || name.is_a?(Symbol)
        fail TypeError.new "#{ name.inspect } is neither string nor symbol"
      end

      # @api hide
      # @raise [AttributeError] it the name is blank.
      def check_name_value
        return unless name.to_s == ""
        fail ArgumentError.new "Dependency should have a name"
      end
    end
  end
end