Example of using Simple Rules to determine item worth and ShelfLife of a project.

• com.lcamilo.other_team.model.Item Cannot be altered as it is maintained by another team that doesn’t believe in shared code ownership. To solve this, an Item adapter was created com.lcamilo.store_front.model.ItemRuleAdapter which wraps an Item and add functionality without having to alter the other teams code.

• Two solutions were implemented which both implement an InventoryWorthCalculator:

  A modified implementation of the original code, com.lcamilo.store_front.service.LegacyInventoryWorthCalculator which simplifies the logic by making the code a little more readable.

     public CalculableItem updateWorth(CalculableItem calculableItem) {
      applyGoldRule(calculableItem);
      applyHeliumRule(calculableItem);
      applyCadmiumRule(calculableItem);
      applyAlchemyRule(calculableItem);
      applyMaxWorthValueRule(calculableItem);
      applyMinWorthValueRule(calculableItem);
      applyRegularItemValueRule(calculableItem);
      calculableItem.incrementShelfLifeBy(-1);
      return calculableItem;
    }
  

  A dynamic rule worth based calculator, [com.lcamilo.store_front.service.RuleBasedInventoryWorthCalculator] (https://github.com/lcamilo15/sf-java/blob/master/src/main/java/com/lcamilo/store_front/service/RuleBasedInventoryWorthCalculator.java). A more flexible approach using a simple Rules engine by creating a modified version of a command pattern.

   itemRules = ItemRuleBuilder.newBuilder()
      .addRule(
          when(IS_REGULAR_ITEM.and(SHELF_DATE_HAS_NOT_PASSED)),
          then(incrementBy(incrementValueBy, defaultMaxWorthValue))
      )