Email Service Notification Handler

Build a notification handler that processes email events using callback functions. The handler should accept callback functions for different email events and invoke them with the appropriate data.

Requirements

Implement a NotificationHandler class with the following functionality:

1. Accept three callback functions in the constructor:

   • onEmailSent: Called when an email is successfully sent
   • onEmailFailed: Called when an email fails to send
   • onEmailQueued: Called when an email is queued for sending

2. Provide a processEmail method that:

   • Takes an email object with properties: to, subject, status (one of: 'sent', 'failed', 'queued')
   • Invokes the appropriate callback based on the status
   • Passes the email object to the callback

3. Provide a processBatch method that:

   • Takes an array of email objects
   • Processes each email using the processEmail method
   • Returns the total count of emails processed

Implementation

@generates

API

/**
 * NotificationHandler manages callbacks for email events
 */
class NotificationHandler {
  /**
   * @param {Object} callbacks - Callback functions for email events
   * @param {Function} callbacks.onEmailSent - Called when email is sent
   * @param {Function} callbacks.onEmailFailed - Called when email fails
   * @param {Function} callbacks.onEmailQueued - Called when email is queued
   */
  constructor(callbacks) {
    // Implementation
  }

  /**
   * Process a single email and invoke the appropriate callback
   * @param {Object} email - Email object with to, subject, and status
   */
  processEmail(email) {
    // Implementation
  }

  /**
   * Process multiple emails
   * @param {Array<Object>} emails - Array of email objects
   * @returns {number} Total number of emails processed
   */
  processBatch(emails) {
    // Implementation
  }
}

module.exports = { NotificationHandler };

Tests

• When an email with status 'sent' is processed, the onEmailSent callback is invoked with the email object @test
• When an email with status 'failed' is processed, the onEmailFailed callback is invoked with the email object @test
• When an email with status 'queued' is processed, the onEmailQueued callback is invoked with the email object @test
• When processing a batch of 5 emails, all callbacks are invoked the correct number of times based on email statuses @test

Dependencies { .dependencies }

jest { .dependency }

Provides testing framework and mocking capabilities.