MultiparameterHack

module MultiparameterHack
  def self.included klass
    klass.class_eval do
      @date_error_on_attribute = nil
      
      def validate
        errors.add_to_base "Invalid Date #{@date_error_on_attribute}" if @date_error_on_attribute
      end
      
      undef :execute_callstack_for_multiparameter_attributes
      def execute_callstack_for_multiparameter_attributes(callstack)
        errors = []
        callstack.each do |name, values_with_empty_parameters|
          begin
            klass = (self.class.reflect_on_aggregation(name.to_sym) || column_for_attribute(name)).klass
            # in order to allow a date to be set without a year, we must keep the empty values.
            # Otherwise, we wouldn't be able to distinguish it from a date with an empty day.
            values = values_with_empty_parameters.reject(&:nil?)

            if values.empty?
              send(name + "=", nil)
            else

              value = if Time == klass
                instantiate_time_object(name, values)
              elsif Date == klass
                begin
                  values = values_with_empty_parameters.collect do |v| v.nil? ? 1 : v end
                  Date.new(*values)
                rescue ArgumentError => ex # if Date.new raises an exception on an invalid date
                  instantiate_time_object(name, values).to_date # we instantiate Time object and convert it back to a date thus using Time's logic in handling invalid dates
                end
              else
                klass.new(*values)
              end

              send(name + "=", value)
            end
          rescue => ex
            errors << ActiveRecord::AttributeAssignmentError.new("error on assignment #{values.inspect} to #{name}", ex, name)
            
            if self.errors.empty?
              @date_error_on_attribute = name
            end
          end
        end
      end
      
    end
  end
end  
  
ActiveRecord::Base.send(:include, MultiparameterHack)