Ports example in hexagonal architecture

processingCustomerCartPorts.js

const ProcessingCustomerPorts = (useCase, userInterface, router, eventBus, errorHandler) => {
  // inbound messages - here event bus approach is used.
  eventBus.on('addItemToCart',  item => {
    useCase.addItemToCart(item);
  });
  
  eventBus.on('cartLoaded', items => {
    items.forEach(item => {
      useCase.addItemToCart(item);
    });
  });
  
  // outbound messages - passed directly to the use case. 
  // Can use event bus publishing as well on the use case side.
  return {
    cartErrorHappened(userMessage) {
      errorHandler.notify(errorHandler.USER_ERROR, userMessage);
    },
    cartItemAdded(cartItems, addedItem) {
      userInterface.updateCart(cartItems);
    },
    cartItemsConfirmed() {
      router.proceedToCheckout();
    }
  };
};