module Annotatable::ClassMethods

def self.extended(base)
  base.instance_eval do
    alias :inherited_without_annotatable :inherited
    alias :inherited :inherited_with_annotatable
  end
end

def annotate(*attrs)
  options = {}
  options = attrs.pop if attrs.last.is_a?(Hash)
  options.symbolize_keys!
  inherit = options[:inherit]
  if inherit
    @inherited_annotations ||= []
    @inherited_annotations += attrs
  end
  attrs.each do |attr|
    class_eval %{
      def self.#{attr}(string = nil)
        @#{attr} = string || @#{attr}
      end
      def #{attr}(string = nil)
        self.class.#{attr}(string)
      end
      def self.#{attr}=(string = nil)
        #{attr}(string)
      end
      def #{attr}=(string = nil)
        self.class.#{attr}=(string)
      end
    }
  end
  attrs
end

def inherited_with_annotatable(subclass)
  inherited_without_annotatable(subclass)
  (['inherited_annotations'] + (@inherited_annotations || [])).each do |t|
    ivar = "@#{t}"
    subclass.instance_variable_set(ivar, instance_variable_get(ivar))
  end
end