Calendar Integration and Event Sync

This project simulates the integration of various external calendar services (Google Calendar, Outlook Calendar, iCal) and synchronizes their events with a local calendar. It demonstrates clean code architecture using OOP principles, proper error handling, and conflict detection during event synchronization.

Features

Mock API Setup:

• Endpoints for mock calendar services:

  • GET /google-calendar/events
  • GET /outlook-calendar/events
  • GET /ical/events

• Endpoints for mock authentication:

  • POST /auth/token
  • POST /auth/refresh

Calendar Class:

• addEvent: Adds an event to the local calendar after checking for conflicts.
• syncWithExternalCalendar: Fetches events from an external provider, normalizes them, and adds them to the local calendar.

Event class

• fromProviderData: Converts events from various providers into a common format.

Conflict Detection:

• Detects overlapping events.
• Logs conflicts and skips conflicting events.
• Suggests time slots for rescheduling conflicting calls.

Getting Started

Prerequisites

• Node.js (v14 or later)

Install dependencies

1. Clone the repository:

   git clone https://github.com/your-username/calendar-sync-project.git
   cd calendar-sync-project

2. Install dependencies:

   npm install

Run the server

Start the mock server:

npm start

Run tests

Execute the test cases:

npm test

Testing the APIs

• Fetch Events (GET): http://localhost:3000/ical/events?calendarId=<calendarId>
  • Return events with 200 status if calendar ID is found
  • Return 404 status with error message if calendar ID is not found

Error Handling Scenarios

• Network Errors: If there is a network error while fetching events from an external calendar, the system will retry up to 3 times before logging an error message and aborting the sync process.
• Conflict Detection: When adding an event, if there is a conflict with an existing event, the system will log a conflict message and suggest alternative time slots.
• Invalid Provider: If an unknown provider is specified for syncing, the system will log an error message and abort the sync process.

Test Cases for Code Validation

The project includes comprehensive test cases to validate the functionality of the calendar integration and event sync.

Test Cases:

1. Add Event Without Conflicts:

   • Adds a new event to the local calendar and verifies that it is added successfully without conflicts.

2. Detect Conflict and Skip Adding Event:

   • Attempts to add an event that conflicts with an existing event and verifies that the conflict is detected and the event is not added.

3. Remove Existing Event:

   • Adds an event to the local calendar, removes it, and verifies that it is removed successfully.

4. Update Existing Event:

   • Adds an event to the local calendar, updates it, and verifies that the event is updated successfully.

5. Sync with External Calendar:

   • Mocks API responses for external calendar events, syncs events with the local calendar, and verifies that events are added or conflicts are detected as expected.

Example Test Case:

// Test Cases for Calendar Integration

const { Calendar } = require('../src/models/calendar');
const { Event } = require('../src/models/event');
const axios = require('axios');
jest.mock('axios');

describe('Calendar Integration Example Workflow', () => {
  let calendar;

  beforeEach(() => {
    calendar = new Calendar();
    jest.clearAllMocks();
  });

  test('should sync events, detect conflicts, and suggest time slots', async () => {
    // Mock API responses
    axios.get.mockImplementation((url) => {
      if (url.includes('google-calendar')) {
        return Promise.resolve({
          data: [
            {
              eventId: 'g-1',
              summary: 'Team Meeting',
              start: { dateTime: '2025-01-04T10:00:00Z' },
              end: { dateTime: '2025-01-04T11:00:00Z' },
              attendees: ['user-1', 'user-2']
            }
          ]
        });
      }
      if (url.includes('outlook-calendar')) {
        return Promise.resolve({
          data: [
            {
              id: 'o-1',
              subject: 'Client Call',
              start: '2025-01-04T12:00:00Z',
              end: '2025-01-04T13:00:00Z',
              participants: ['user-1']
            }
          ]
        });
      }
      if (url.includes('ical')) {
        return Promise.resolve({
          data: [
            {
              UID: 'ical-1',
              SUMMARY: 'Project Kickoff',
              DTSTART: '20250104T090000Z',
              DTEND: '20250104T100000Z',
              ATTENDEES: ['user-1', 'user-3']
            }
          ]
        });
      }
      return Promise.reject(new Error('Unknown provider'));
    });

    console.log = jest.fn();

    // Initial local event
    const localEvent = new Event(
      'local-1',
      'Project Discussion',
      '2025-01-04T10:30:00Z',
      '2025-01-04T11:30:00Z',
      ['user-1', 'user-3']
    );
    calendar.addEvent('calendar-1', localEvent);

    // Sync with external calendars
    await calendar.syncWithExternalCalendar('calendar-1', 'google');
    await calendar.syncWithExternalCalendar('calendar-1', 'outlook');

    // Check logs for added events and conflicts
    expect(console.log).toHaveBeenCalledWith(
      'Fetching google events for calendarId: calendar-1'
    );
    expect(console.log).toHaveBeenCalledWith(
      'Conflict Detected: Team Meeting overlaps with Project Discussion in calendar calendar-1'
    );
    expect(console.log).toHaveBeenCalledWith(
      'Suggested Time Slots for Team Meeting:', expect.any(Array)
    );
    expect(console.log).toHaveBeenCalledWith(
      'Successfully synced events for calendar calendar-1 from google'
    );
    expect(console.log).toHaveBeenCalledWith(
      'Fetching outlook events for calendarId: calendar-1'
    );
    expect(console.log).toHaveBeenCalledWith(
      'Added Event: Client Call to calendar calendar-1'
    );
    expect(console.log).toHaveBeenCalledWith(
      'Successfully synced events for calendar calendar-1 from outlook'
    );

    // Ensure the final state of the calendar is as expected
    expect(calendar.calendars['calendar-1'].length).toBe(2);
  });
});

Challenges Faced

Project is surely very interesting and since I am working in Node.js after a little while, its fun to do as well since I have learned a lot!

I have structured the project in a manner that is following Object-Oriented design principles throughout the code. Writing test cases in this project is also a learning experience.

So initially structuring and planing the task was surely a challenge, but then it was very fun during implementation.