module ValidatesDateTime
  module MultiparameterAttributes
    def self.included(base)
      base.alias_method_chain :execute_callstack_for_multiparameter_attributes, :temporal_error_handling
    end
    
    def execute_callstack_for_multiparameter_attributes_with_temporal_error_handling(callstack)
      errors = []
      callstack.each do |name, values|
        klass = (self.class.reflect_on_aggregation(name.to_sym) || column_for_attribute(name)).klass
        
        if values.empty?
          send("#{name}=", nil)
        else
          column = column_for_attribute(name)
          
          if [:date, :time, :datetime].include?(column.type)
            values = values.map(&:to_s)
            
            result = case column.type
              when :date
                extract_date_from_multiparameter_attributes(values)
              when :time
                extract_time_from_multiparameter_attributes(values)
              when :datetime
                date_values, time_values = values.slice!(0, 3), values
                extract_date_from_multiparameter_attributes(date_values) + " " + extract_time_from_multiparameter_attributes(time_values)
            end
                   
            send("#{name}=", result)
          end
        end
      end
      unless errors.empty?
        raise ActiveRecord::MultiparameterAssignmentErrors.new(errors), "#{errors.size} error(s) on assignment of multiparameter attributes"
      end
    end
    
    def extract_date_from_multiparameter_attributes(values)
      [values[0], *values.slice(1, 2).map { |s| s.rjust(2, "0") }].join("-")
    end
    
    def extract_time_from_multiparameter_attributes(values)
      values.last(3).map { |s| s.rjust(2, "0") }.join(":")
    end
  end
end