module Maintain
  module Backend
    class ActiveRecord < Maintain::Backend::Base
      def aggregate(maintainee, name, attribute, states, options = {})
        # named_scope will handle the array of states as "IN" in SQL
        state(maintainee, name, attribute, states, options.merge(:dirty => false))
      end

      def on(maintainee, attribute, event, state, method, options)
        attribute_check = "#{attribute}#{"_was" if event == :exit}_#{state}?"
        hook_method = options[:after] ? :after : :before
        maintainee.send("#{hook_method}_save", method, :if => lambda {|instance|
          if instance.send("#{attribute}_changed?") && instance.send(attribute_check)
            if options[:if]
              if options[:if].is_a?(Proc)
                instance.instance_eval(&options[:if])
              else
                instance.send(options[:if])
              end
            elsif options[:unless]
              if options[:unless].is_a?(Proc)
                !instance.instance_eval(&options[:unless])
              else
                !instance.send(options[:unless])
              end
            else
              true
            end
          else
            false
          end
        })
      end

      def read(instance, attribute)
        instance.read_attribute(attribute)
      end

      def state(maintainee, name, attribute, value, options = {})
        options = {:dirty => true}.merge(options)
        conditions = {:conditions => {attribute => value}}
        named_scope_method = defined?(::ActiveRecord::VERSION) && ::ActiveRecord::VERSION::STRING >= '3' ? :scope : :named_scope
        maintainee.send(named_scope_method, name, conditions) if !maintainee.respond_to?(name) || options[:force]
        maintainee.send(named_scope_method, "#{attribute}_#{name}", conditions)
        if options[:dirty]
          maintainee.class_eval <<-dirty_tracker
            def #{attribute}_was_#{name}?
              #{attribute}_was == self.class.maintainers[:#{attribute}].value(self).value_for(:#{name})
            end
          dirty_tracker
        end
      end

      def write(instance, attribute, value)
        instance.send(:write_attribute, attribute, value)
      end
    end
  end
end