Event Emitter: Order Processing

You have been given the task to write an Order-Processing Script that takes the order data as input, performs a few pre-order checks/validations, and returns the result. If any line-item in the order data does not pass the pre-order checks, the order should fail, and the corresponding failure event should be fired.

Class Definition

Create a module, processor.js, and implement the following set of functionalities:

The file should export a class OrderProcessor as the default export of the module, and it should inherit from the EventEmitter class.

Methods:

placeOrder: Accepts the order data as an argument and immediately starts performing the validations on it. The orderData passed to the function should have the following properties/shape:

[
  {
    "orderNumber": "OD2323", // Order Number of the order
    "lineItems": [
      // Array containing the lineItems in the order
      {
        "itemId": 3, // ID of the line Item.
        "quantity": 4 // The quantity requested in the order
      },
      {
        "itemId": 5,
        "quantity": 4
      }
    ]
  }
]

Events:

The class should emit the following events

PROCESSING_STARTED: Should be fired just before the validations are started for an order. The order number of the current order should be passed to the callback of the event handler.
PROCESSING_FAILED: Should be fired if, for any reason, the pre-order checks do not pass. The callback of the event handler will accept an object containing the following properties:
- orderNumber: The orderNumber of the order that failed to process.
- itemId: The ID of the first matching item that failed to process.
- reason: The reason why the processing failed. It can be one of INSUFFICIENT_STOCK or LINEITEMS_EMPTY.
  - If the lineItems property is a blank array, the check should fail with the reason LINEITEMS_EMPTY. The itemId property need not be passed to the errorObject in this scenario.
  - If any of the lineItems' requested quantity is more than the matching stock property in the stockData array, the check should fail with the reason INSUFFICIENT_STOCK.
PROCESSING_SUCCESS: Should be fired if all the pre-order checks pass. The order number of the current order should be passed to the callback of the event handler.

The file containing the current stock information, stock-list.json, is added to the root of the project and can be used for validation. An explanation of an entry in the JSON array is as follows:

id: The ID of the item for which stock information is stored.
stock: The current stock count of the item.

[
  {
    "id": 0,
    "stock": 4
  },
  {
    "id": 1,
    "stock": 12
  },
...
]

Note: It can be assumed that lineitems passed to the placeOrder function will always be an array, and the ID of the lineItem passed will always be present in the stock list. No extra code is required for these conditions.

Example Implementation

Please open the file index.js for example implementation.

Project Specifications

Read-Only Paths

test

Commands

run: npm start
install: npm install
test: npm test