LibraryManagementAPI

A simple, maintainable library management API that manages books, users, and transactions (borrowing and returning books).built with N-Layered Architecture in ASP.NET Core — prioritizing separation of concerns, testability, and real-world workflows. Features

 User & Book Management (CRUD)  
 Transaction Lifecycle: Borrowing, returning, due date tracking  
 Validation: Ensures users/books exist before transactions  
 Secure Authentication: JWT-based login (with BCrypt hashing)  
 Resilient Design: Proper exception handling, logging, and async/await  

Tech Stack Framework

ASP.NET Core 8 (Minimal APIs) Architecture

N-Layered Architecture Data

Entity Framework Core, SQL Server (SSMS) Auth

JWT Bearer, BCrypt.Net for password hashing API Docs

Swagger/OpenAPI Testing

Tools

Git (project tracking)

Getting Started Prerequisites

.NET 8 SDK 
SQL Server (LocalDB, Express, or Docker)

Setup

Clone the repo: 
bash

1 2 git clone https://github.com/your-username/LibraryManagementAPI.git cd LibraryManagementAPI

Update the connection string in appsettings.json: json

1 2 3 ⌄ "ConnectionStrings": { "DefaultConnection": "Server=(localdb)\mssqllocaldb;Database=LibraryDB;Trusted_Connection=true;" }

Apply migrations & seed (optional): bash

1 dotnet ef database update

Run the API: bash

1
dotnet run
 
 

Explore the API: 
    Swagger UI: https://localhost:5001/swagger

Authentication Flow

Register a user (POST /api/auth/register)  
Login to receive a JWT (POST /api/auth/login)  
Include token in Authorization: Bearer <token> header for protected endpoints (e.g., /api/transactions)
 

Passwords are hashed using BCrypt — never stored in plaintext. 

📦 Key Endpoints /api/books

GET

Get all books /api/books/{id}

GET

Get book by ID /api/users/{id}

GET

Get user by ID /api/transactions

POST

Borrow a book (requires bookId , userId , expectedReturnDate ) /api/transactions/{id}/return

PATCH

Return a book (updates status & actual return date) /api/transactions/user/{userId}

GET

Get all transactions for a user

Design Note: Transaction creation validates existence of user & book before proceeding — avoiding invalid state. Future iterations can include:

Fine calculation on overdue returns
Reservation queues

Testing & Validation

✅ Swagger auto-docs with example requests/responses  
✅ Proper HTTP status codes (400 for validation, 404 for not found, 401 for auth failures)

Contributing

PRs welcome! For major changes, please open an issue first. Let’s build a system that’s not just functional — but thoughtful.