Implementing Choreographed Saga for E-commerce Transactions

Demonstrate the implementation of a choreographed saga in JavaScript for handling an e-commerce transaction, including order creation, payment processing, and stock update.

const EventEmitter = require('events');
const eventEmitter = new EventEmitter();

// Mock services
class OrderService {
  static createOrder(data) {
    console.log('Creating order', data);
    // Emulate order creation
    eventEmitter.emit('orderCreated', { orderId: 123, ...data });
  }
}

class PaymentService {
  static processPayment(order) {
    console.log('Processing payment for', order);
    // Payment logic
    eventEmitter.emit('paymentProcessed', order);
  }
}

class StockService {
  static updateStock(order) {
    console.log('Updating stock for', order);
    // Stock update logic
    eventEmitter.emit('stockUpdated', order);
  }
}

Sets up basic services and their methods to simulate order creation, payment processing, and stock update. Each service method emits an event upon completion.

// Event listeners
eventEmitter.on('orderCreated', (order) => {
  // Proceed to process payment upon order creation
  PaymentService.processPayment(order);
});

eventEmitter.on('paymentProcessed', (order) => {
  // Proceed to update stock once payment is processed
  StockService.updateStock(order);
});

eventEmitter.on('stockUpdated', (order) => {
  console.log(`Transaction completed for order: ${order.orderId}`);
});

Defines event listeners for 'orderCreated', 'paymentProcessed', and 'stockUpdated' events to move the transaction through the required stages.

// Initiating a saga example
OrderService.createOrder({ item: 'Smartphone', quantity: 1, price: 599 });

Initiates the saga by creating an order. The rest of the process is handled through event-driven callbacks.