Online Learning Platform - Backend API

A comprehensive backend API for an online learning platform similar to Unacademy, built with Node.js, Express.js, and SQLite. This platform supports course management, live classes, video lectures, tests, educator profiles, subscriptions, and detailed progress tracking.

🚀 Features

Core Features

User Authentication & Authorization - JWT-based authentication with role-based access (learner/educator)
Course Management - Complete CRUD operations for courses with enrollment tracking
Video Learning - Lesson management with progress tracking and watch history
Live Classes - Scheduled live sessions with attendance tracking
Test Engine - Comprehensive testing system with analytics and performance tracking
Educator Profiles - Detailed educator management with ratings and reviews
Subscription System - Tiered subscription plans with access control
Doubt Resolution - Q&A system for student-teacher interaction
Study Materials - Resource management with download tracking
Progress Analytics - Detailed learning analytics and performance insights
Search & Discovery - Global search across courses, educators, and lessons
Review System - Course and educator rating system

Advanced Features

Real-time Progress Tracking - Video watch progress with timestamp tracking
Performance Analytics - Detailed test analysis with subject-wise breakdown
Subscription Tiers - Plus and Iconic plans with different access levels
Content Access Control - Enrollment and subscription-based access verification
Error Handling - Comprehensive error handling with appropriate HTTP status codes
Input Validation - Robust validation for all API endpoints
Security Features - Password hashing, rate limiting, and input sanitization

🛠 Tech Stack

Runtime: Node.js
Framework: Express.js
Database: SQLite (with Knex.js ORM)
Authentication: JWT (JSON Web Tokens)
Password Hashing: bcryptjs
Validation: express-validator
Security: Helmet, CORS, Rate Limiting
Logging: Morgan
Environment: dotenv

📋 Prerequisites

Node.js (v14 or higher)
npm or yarn
Git

🚀 Quick Start

1. Clone the Repository

git clone <repository-url>
cd onlineLearningPlatform

2. Install Dependencies

npm install

3. Environment Setup

# Copy the environment example file
cp env.example .env

# Edit .env file with your configuration

4. Database Setup

# Run database migrations
npm run migrate

# Seed the database with sample data
npm run seed

5. Start the Server

# Development mode with auto-reload
npm run dev

# Production mode
npm start

The API will be available at http://localhost:3000

📁 Project Structure

onlineLearningPlatform/
├── src/
│   ├── config/
│   │   ├── database.js          # Database configuration and connection
│   │   ├── migrate.js           # Database migration script
│   │   └── seed.js              # Database seeding script
│   ├── controllers/
│   │   ├── authController.js    # Authentication logic
│   │   ├── courseController.js  # Course management
│   │   ├── lessonController.js  # Lesson and video management
│   │   └── testController.js    # Test and quiz management
│   ├── middleware/
│   │   ├── auth.js              # JWT authentication middleware
│   │   ├── enrollment.js        # Enrollment verification
│   │   ├── subscription.js      # Subscription access control
│   │   ├── validation.js        # Input validation
│   │   └── errorHandler.js      # Error handling middleware
│   ├── models/
│   │   ├── user.js              # User model
│   │   ├── course.js            # Course model
│   │   ├── lesson.js            # Lesson model
│   │   └── educator.js          # Educator model
│   ├── routes/
│   │   ├── authRoutes.js        # Authentication routes
│   │   ├── courseRoutes.js      # Course routes
│   │   ├── lessonRoutes.js      # Lesson routes
│   │   └── testRoutes.js        # Test routes
│   ├── utils/
│   │   ├── constants.js         # Application constants
│   │   └── helpers.js           # Utility functions
│   └── app.js                   # Main application file
├── database/
│   ├── schema.sql               # Database schema
│   ├── seeds.sql                # Sample data
│   └── online_learning.db       # SQLite database file
├── .env                         # Environment variables
├── package.json                 # Dependencies and scripts
└── README.md                    # This file

🗄 Database Design

Core Entities

Users (Learners)

Profile information (name, email, phone)
Target exam (UPSC, NEET, JEE, etc.)
Preferred language
Learning preferences

Educators

Professional profile and credentials
Subject expertise (comma-separated)
Years of experience and qualifications
Rating and student count

Courses

Course details and structure
Target exam and subject
Pricing and discount information
Course type (live/recorded/hybrid)
Features and syllabus

Lessons

Individual video lessons
Duration and order tracking
Free/premium access control
Video URLs and thumbnails

Live Classes

Scheduled live sessions
Capacity management
Attendance tracking
Recording availability

Enrollments & Progress

User course enrollments
Video watch progress
Completion tracking
Last accessed timestamps

Tests & Analytics

Practice tests and mock exams
Question banks with explanations
Performance analytics
Subject-wise analysis

Subscriptions

Tiered subscription plans
Payment tracking
Access control
Feature benefits

Key Relationships

One-to-Many: Educator → Courses, Course → Lessons
Many-to-Many: Users ↔ Courses (via Enrollments)
One-to-Many: Course → Tests, User → Test Attempts
One-to-Many: User → Doubts, Educator → Doubt Answers

🔌 API Documentation

Base URL

http://localhost:3000

Authentication

All protected endpoints require a JWT token in the Authorization header:

Authorization: Bearer <jwt_token>

1. Authentication Endpoints

Register Learner

POST /api/auth/register
Content-Type: application/json

{
    "email": "learner@example.com",
    "password": "SecurePass123",
    "firstName": "John",
    "lastName": "Doe",
    "targetExam": "JEE Main",
    "preferredLanguage": "English",
    "phone": "+91-9876543210"
}

Register Educator

POST /api/auth/educator/register
Content-Type: application/json

{
    "email": "educator@example.com",
    "password": "SecurePass123",
    "firstName": "Dr. Sarah",
    "lastName": "Kumar",
    "bio": "Experienced educator with 10+ years of teaching",
    "subjects": "Mathematics,Physics",
    "experience": 10,
    "qualification": "Ph.D. Mathematics, IIT Delhi"
}

Login

POST /api/auth/login
Content-Type: application/json

{
    "email": "learner@example.com",
    "password": "SecurePass123"
}

2. Course Endpoints

Browse Courses

GET /api/courses?exam=JEE Main&subject=Mathematics&type=recorded&page=1&limit=10

Get Course Details

GET /api/courses/1

Enroll in Course

POST /api/courses/1/enroll
Authorization: Bearer <token>

Get Course Progress

GET /api/courses/1/progress
Authorization: Bearer <token>

3. Lesson Endpoints

Get Lesson Details

GET /api/lessons/1
Authorization: Bearer <token>

Update Lesson Progress

POST /api/lessons/1/progress
Authorization: Bearer <token>
Content-Type: application/json

{
    "watchedDuration": 1800,
    "totalDuration": 2700,
    "completionStatus": "in_progress"
}

Save Lesson Notes

POST /api/lessons/1/notes
Authorization: Bearer <token>
Content-Type: application/json

{
    "note": "Important concept about algebra",
    "timestamp": 120
}

4. Test Endpoints

Get Available Tests

GET /api/tests?courseId=1&type=mock_test
Authorization: Bearer <token>

Start Test

POST /api/tests/1/start
Authorization: Bearer <token>

Submit Test Answers

POST /api/tests/session_001/submit
Authorization: Bearer <token>
Content-Type: application/json

{
    "answers": [
        { "questionId": 1, "selectedOption": "4" },
        { "questionId": 2, "selectedOption": "wrong" }
    ],
    "timeSpent": 180
}

5. Live Class Endpoints

Get Live Class Schedule

GET /api/live-classes/schedule?courseId=1
Authorization: Bearer <token>

Join Live Class

POST /api/live-classes/1/join
Authorization: Bearer <token>

6. Doubt Resolution

Post a Doubt

POST /api/doubts
Authorization: Bearer <token>
Content-Type: application/json

{
    "courseId": 1,
    "lessonId": 1,
    "question": "Why is acceleration constant in free fall?",
    "attachments": ["http://example.com/image.jpg"]
}

Answer a Doubt (Educator Only)

POST /api/doubts/1/answer
Authorization: Bearer <educator_token>
Content-Type: application/json

{
    "answer": "Acceleration is constant in free fall because gravity is constant near the Earth's surface."
}

7. Subscription Management

Get Subscription Plans

GET /api/subscriptions/plans

Purchase Subscription

POST /api/subscriptions/purchase
Authorization: Bearer <token>
Content-Type: application/json

{
    "planId": 1,
    "paymentMethod": "credit_card",
    "couponCode": "DISCOUNT10"
}

8. Search & Discovery

Global Search

GET /api/search?q=physics
Authorization: Bearer <token>

Browse Educators

GET /api/educators?subject=Physics&rating=4.5
Authorization: Bearer <token>

9. Reviews & Ratings

Post Course Review

POST /api/reviews/courses/1/review
Authorization: Bearer <token>
Content-Type: application/json

{
    "rating": 5,
    "title": "Excellent course!",
    "comment": "The explanations are very clear and the practice questions are helpful."
}

🔒 Security Features

Authentication & Authorization

JWT-based authentication with configurable expiration
Role-based access control (learner/educator)
Password hashing using bcryptjs
Token refresh mechanism

Input Validation & Sanitization

Comprehensive input validation using express-validator
SQL injection prevention through parameterized queries
XSS protection with Helmet middleware
Rate limiting to prevent abuse

Content Access Control

Enrollment verification for course content
Subscription-based access control
Video URL security (signed URLs recommended for production)
Download tracking for study materials

📊 Error Handling

The API implements comprehensive error handling with appropriate HTTP status codes:

200 - Success
201 - Created
400 - Bad Request (validation errors)
401 - Unauthorized (missing/invalid token)
403 - Forbidden (insufficient permissions)
404 - Not Found (resource not found)
409 - Conflict (already enrolled, duplicate resource)
422 - Unprocessable Entity (validation errors)
429 - Too Many Requests (rate limit exceeded)
500 - Internal Server Error

Error Response Format

{
    "success": false,
    "message": "Error description",
    "errors": [
        {
            "field": "email",
            "message": "Invalid email format"
        }
    ]
}

🧪 Testing

Test Files Available

app.http - Complete HTTP test suite for VS Code
test-*.js - Various test scripts for different functionalities
comprehensive-test.js - End-to-end API testing

Running Tests

# Test all APIs using the HTTP file
# Open app.http in VS Code and use the REST Client extension

# Or run individual test scripts
node test-auth.js
node test-courses.js
node test-comprehensive.js

Sample Test Data

The database is seeded with:

10 sample users (learners)
5 educators with profiles
15 courses across different exams
50+ lessons with video content
20+ test questions
Sample enrollments and progress data

🚀 Deployment

Environment Variables

Create a .env file with the following variables:

# Server Configuration
PORT=3000
NODE_ENV=development

# Database Configuration
DB_PATH=./database/online_learning.db

# JWT Configuration
JWT_SECRET=your_jwt_secret_here
JWT_EXPIRES_IN=7d

# Security
RATE_LIMIT_WINDOW_MS=900000
RATE_LIMIT_MAX_REQUESTS=1000

# CORS
ALLOWED_ORIGINS=http://localhost:3000,http://localhost:3001

Production Deployment

Set NODE_ENV=production
Configure proper CORS origins
Use a production database (PostgreSQL/MySQL)
Set up proper logging and monitoring
Configure SSL/TLS certificates
Set up rate limiting and security headers

📈 Performance & Analytics

Learning Analytics

Video watch progress tracking
Test performance analytics
Subject-wise performance breakdown
Learning streak tracking
Course completion rates

Performance Optimizations

Database indexing on frequently queried fields
Efficient query optimization
Response caching for static content
Pagination for large datasets

🔧 Development

Available Scripts

npm start          # Start production server
npm run dev        # Start development server with nodemon
npm run migrate    # Run database migrations
npm run seed       # Seed database with sample data

Code Style

Consistent error handling patterns
Input validation on all endpoints
Proper HTTP status codes
Comprehensive logging
Security best practices

📝 Assumptions Made

Content Delivery: Video URLs are assumed to be external (YouTube, Vimeo, etc.)
File Storage: Study materials are stored externally with download URLs
Payment Processing: Payment gateway integration is not implemented (mock responses)
Real-time Features: Live class streaming uses external services
Email Notifications: Email service integration not implemented
Mobile App: API designed to work with mobile applications
Scalability: Database designed to handle thousands of concurrent users

🎯 Bonus Features Implemented

Comprehensive Progress Tracking: Detailed video watch progress with timestamps
Advanced Test Analytics: Subject-wise performance analysis with percentiles
Subscription Tiers: Plus and Iconic plans with different access levels
Doubt Resolution System: Complete Q&A system for student-teacher interaction
Study Material Management: Resource tracking with download analytics
Global Search: Cross-entity search functionality
Review System: Course and educator rating system
Live Class Management: Scheduling and attendance tracking
Performance Analytics: Detailed learning insights and progress tracking

🎓Outcomes

This project demonstrates:

Database design with proper relationships and constraints
Authentication & authorization with JWT tokens
Input validation and error handling
Security best practices implementation
Performance optimization techniques
Comprehensive testing strategies
API documentation and developer experience

Name		Name	Last commit message	Last commit date
Latest commit History 3 Commits
database		database
src		src
.gitignore		.gitignore
ER_Relationship_Diagram.txt		ER_Relationship_Diagram.txt
Online_Learning_Platform_API.postman_collection.json		Online_Learning_Platform_API.postman_collection.json
Online_Learning_Platform_Environment.postman_environment.json		Online_Learning_Platform_Environment.postman_environment.json
POSTMAN_SETUP.md		POSTMAN_SETUP.md
README.md		README.md
app.http		app.http
comprehensive-test.js		comprehensive-test.js
create-test-user.js		create-test-user.js
fix-passwords.js		fix-passwords.js
package-lock.json		package-lock.json
package.json		package.json
test-all-apis.js		test-all-apis.js
test-apis.js		test-apis.js
test-app-http-focused.js		test-app-http-focused.js
test-app-http.js		test-app-http.js
test-auth.js		test-auth.js
test-comprehensive.js		test-comprehensive.js
test-core-apis.js		test-core-apis.js
test-enrollment.js		test-enrollment.js
test-lesson-api.js		test-lesson-api.js
test-name-splitting.js		test-name-splitting.js
test-registration.js		test-registration.js
test-working-endpoints.js		test-working-endpoints.js

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