A backend-only Smart Library System built using Node.js (Express) and MongoDB, designed for a distributed systems course. This project implements a monolithic architecture with RESTful APIs for user management, book management, loan management, and system statistics. The system is tested using Postman.

• Project Overview
• Features
• Technologies
• Project Structure
• Setup Instructions
• API Endpoints
• Testing with Postman
• Troubleshooting
• Future Improvements

The Smart Library System is a monolithic backend application that manages library operations, including user registration, book catalog management, book loans, and system statistics. It uses a single MongoDB database and exposes RESTful APIs for external clients. All modules are tightly coupled, residing in the same codebase and memory space, with communication via function calls.

• Register students or faculty.
• Retrieve and update user profiles.

• Add, update, or remove books.
• Search books by title or author.
• View book availability.

• Issue books to users.
• Return borrowed books.
• View active/past loans and overdue loans.
• Extend loan due dates.

• View most borrowed books.
• Identify most active users.
• Get system-wide statistics (e.g., total books, overdue loans).

• Node.js: JavaScript runtime for the backend.
• Express.js: Web framework for building RESTful APIs.
• MongoDB: NoSQL database for storing users, books, and loans.
• Mongoose: ODM for MongoDB schema management.
• Postman: Tool for testing APIs.
• Dependencies:
  • express, mongoose, body-parser, cors, dotenv, moment, uuid
  • Dev: nodemon

smart-library-monolithic/
├── config/
│   └── db.js              # MongoDB connection setup
├── models/
│   ├── User.js            # User schema
│   ├── Book.js            # Book schema
│   └── Loan.js            # Loan schema
├── routes/
│   ├── userRoutes.js      # User API routes
│   ├── bookRoutes.js      # Book API routes
│   ├── loanRoutes.js      # Loan API routes
│   └── statsRoutes.js     # Statistics API routes
├── controllers/
│   ├── userController.js  # User logic
│   ├── bookController.js  # Book logic
│   ├── loanController.js  # Loan logic
│   └── statsController.js # Statistics logic
├── middleware/
│   └── errorHandler.js    # Global error handling
├── .env                   # Environment variables
├── package.json           # Project metadata and dependencies
├── server.js              # Main server file
└── README.md              # Project documentation

• Node.js (v16 or higher)
• MongoDB (local or cloud, e.g., MongoDB Atlas)
• Postman (for API testing)
• Git (optional, for cloning)

1. Clone the Repository (if applicable):

   git clone https://github.com/FarhanTausif/smart-library-monolithic.git
   cd smart-library-monolithic

2. Install Dependencies:

   npm install

3. Set Up Environment Variables:

   • Create a .env file in the root directory:

     PORT=3000
     MONGO_URI=mongodb://localhost:27017/smart_library
     

   • Replace MONGO_URI with your MongoDB connection string if using a cloud service like MongoDB Atlas.

4. Start MongoDB:

   • If local, run mongod in a terminal.
   • Ensure MongoDB is accessible at the specified MONGO_URI.

5. Run the Application:

   npm run dev

   • Uses nodemon for auto-restart on file changes.
   • Server runs on http://localhost:3000 (or the specified PORT).

The system exposes RESTful APIs under the /api prefix. Below is a summary of key endpoints. All requests/responses use JSON.

• POST /api/users: Register a new user.
  • Body: { "name": "Alice Smith", "email": "[email protected]", "role": "student" }
  • Response: 201 Created
• GET /api/users/:id: Get user profile by ID.
  • Response: 200 OK
• PUT /api/users/:id: Update user profile.
  • Body: { "name": "Alice Smith", "email": "[email protected]", "role": "student" }
  • Response: 200 OK

• POST /api/books: Add a new book.
  • Body: { "title": "Clean Code", "author": "Robert C. Martin", "isbn": "9780132350884", "copies": 3 }
  • Response: 201 Created
• GET /api/books?search=clean: Search books by title or author.
  • Response: 200 OK
• GET /api/books/:id: Get book details.
  • Response: 200 OK
• PUT /api/books/:id: Update book details.
  • Body: { "copies": 5, "available_copies": 3 }
  • Response: 200 OK
• DELETE /api/books/:id: Remove a book.
  • Response: 204 No Content

• POST /api/loans: Issue a book to a user.
  • Body: { "user_id": "user_id", "book_id": "book_id", "due_date": "2025-05-15T23:59:59Z" }
  • Response: 201 Created
• POST /api/returns: Return a borrowed book.
  • Body: { "loan_id": "loan_id" }
  • Response: 200 OK
• GET /api/loans/:user_id: Get user loan history.
  • Response: 200 OK
• GET /api/loans/overdue: List overdue loans.
  • Response: 200 OK
• PUT /api/loans/:id/extend: Extend loan due date.
  • Body: { "extension_days": 7 }
  • Response: 200 OK

• GET /api/stats/books/popular: Get most borrowed books.
  • Response: 200 OK
• GET /api/stats/users/active: Get most active users.
  • Response: 200 OK
• GET /api/stats/overview: Get system overview (total books, users, etc.).
  • Response: 200 OK

1. Install Postman: Download from postman.com.
2. Create a Collection:
   • Name it "Smart Library System".
   • Add requests for each endpoint.
3. Example Requests:
   • Register User:
     • Method: POST
     • URL: http://localhost:3000/api/users
     • Body: { "name": "Alice Smith", "email": "[email protected]", "role": "student" }
     • Expected: 201 Created
   • Add Book:
     • Method: POST
     • URL: http://localhost:3000/api/books
     • Body: { "title": "Clean Code", "author": "Robert C. Martin", "isbn": "9780132350884", "copies": 3 }
     • Expected: 201 Created
   • Issue Book:
     • Method: POST
     • URL: http://localhost:3000/api/loans
     • Body: { "user_id": "user_id", "book_id": "book_id", "due_date": "2025-05-15T23:59:59Z" }
     • Expected: 201 Created
4. Testing Tips:
   • Test sequentially: Create users and books before loans.
   • Verify status codes (201, 200, 204, 400, 404).
   • Test edge cases (e.g., issuing unavailable books, extending loans multiple times).

• MongoDB Connection Error: Ensure MongoDB is running and MONGO_URI is correct.
• Port Conflict: Change PORT in .env if 3000 is in use.
• Nodemon Not Found: Run npm install -g nodemon.
• Postman Errors: Check JSON payloads and URLs.
• API Errors: Review server logs for stack traces.

• Add input validation (e.g., express-validator).
• Implement authentication (e.g., JWT).
• Add automated tests with Jest or Mocha.
• Introduce rate limiting and logging for production.
• Enhance error messages for better debugging.