module Me
  module ActsAsBitfield

    def self.included(base)
      base.send :extend, ClassMethods
    end

    module ClassMethods
      def acts_as_bitfield(bitfield, attrs, virtual_attrs = {})
        unless respond_to? :bitfields
          class_eval { cattr_accessor :bitfields }
          self.bitfields = {}
        end
        b = 0
        self.bitfields[bitfield.to_sym] = attrs.inject({}) do |attr_values, attr|
          attr_values[attr.to_sym] = 2 ** b
          b +=
        end

        virtual_attrs.each do |attr, values|
          self.bitfields[bitfield.to_sym][attr.to_sym] = virtuals(bitfield, attr, values)
        end

        define_method("get_#{bitfield}") do
          self.bitfields[bitfield.to_sym].select{|attr, value| get_bit_into_bitfield(bitfield, value) == 1 }.keys
        end

        # Create bit accessors
        self.bitfields[bitfield.to_sym].each_key do |attr|
          value = self.bitfields[bitfield.to_sym][attr]

          define_method("#{bitfield}_#{attr}") do
            get_bit_into_bitfield(bitfield, value)
          end

          define_method("#{bitfield}_#{attr}?") do
            get_bit_into_bitfield(bitfield, value) == 1
          end

          define_method("#{bitfield}_#{attr}=") do |flag|
            set_bit_into_bitfield(bitfield, value, flag)
          end
        end

        puts self.bitfields
        # Virtual bit accessors
        def virtuals(bitfield, attr, values)
          value = values.inject(self.bitfields[bitfield.to_sym][values[0]]) do |memo, v|
            memo & self.bitfields[bitfield.to_sym][v]
          end
          value
        end

        send :include, InstanceMethods
      end
    end

    module InstanceMethods
      private

      def get_bit_into_bitfield(bitfield, value)
        (self.send(bitfield) & value == 0) ? 0 : 1
      end

      def set_bit_into_bitfield(bitfield, value, flag)
        write_attribute(bitfield, self.send(bitfield) | value)
        write_attribute(bitfield, self.send(bitfield) ^ value) unless ActiveRecord::Type::Boolean.new.type_cast_from_user(flag)
      end
    end
  end
end