module Persistable

  require 'set' unless defined? Set

  def self.included(klass)
    klass.class_eval do
      attr_accessor :_store
      private :_store

      def store
        self._store ||= if defined?(Maglev)
          self.maglev_persistable
          ( Maglev::PERSISTENT_ROOT[self] ||= Set.new )
        else
          Set.new
        end
      end

     def self.store
       (self.first) ? (self.first._store) : nil
     end

      class << self
        include Enumerable

        require 'debug'
        debug

        def each(&block)
          #@@store.each {|x| yield x}
          @@store.each &block
        end

        def count
          @@store.count
        end

        def all
          @@store.to_a
        end

        def delete_all
          @@store -= @@store
        end
      end

      def persist
        @@store.add?(self) ? true: false
      end

      def desist
        @@store.delete self
      end

      def persistent?
        @@store.include? self
      end

      def transient?
        not persistent?
      end

    end
  end

end