backend

README

Backend Workflow - Library Management System

Overview

The backend of the Library Management System (LibMS) is responsible for handling user authentication, managing book inventories, processing issue requests, and maintaining user roles and permissions. Built with Go (Gin framework) and PostgreSQL (GORM ORM), it ensures high performance and secure operations.

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Technology Stack

• Language: Go (Gin framework)
• Database: PostgreSQL (GORM ORM), SQLite (testing)
• Authentication: JWT-based authentication
• Middleware: JWT for authorization, CORS for cross-origin requests
• Configuration: .env files for environment management
• Logging & Error Handling: Structured logging for debugging and monitoring
• Testing: Unit testing using Go's built-in framework and sqlmock for database interactions

NOTE

The test report is saved as a csv in ./.blob/report. You can generate the report via running the shellscipt ./gen_report.sh

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Backend Project Structure

backend/
├── gen_report.sh
├── go.mod
├── go.sum
├── README.md
├── src
│   ├── db
│   │   └── db.go
│   ├── handlers
│   │   ├── auth_handler.go
│   │   ├── book_handler.go
│   │   ├── claims_handler.go
│   │   ├── issue_handler.go
│   │   ├── library_handler.go
│   │   ├── owner_handler.go
│   │   ├── request_events_handler.go
│   │   └── user_handler.go
│   ├── main.go
│   ├── middleware
│   │   └── jwt.go
│   ├── models
│   │   ├── book_inventory_model.go
│   │   ├── issue_registry_model.go
│   │   ├── library_model.go
│   │   ├── request_events_model.go
│   │   └── user_model.go
│   └── routes
│       └── routes.go
└── test
    ├── books_test.go
    ├── db_setup_test.go
    ├── issue_request_test.go
    ├── jwt_test.go
    ├── library_test.go
    ├── login_user_test.go
    ├── negative_test.go
    ├── owner_operations_test.go
    ├── raise_request_test.go
    ├── register_user_test.go
    └── user_test.go

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Database Schema

The database schema follows a relational structure that efficiently manages books, users, and transactions. It ensures data integrity and minimizes redundancy by implementing foreign key constraints where necessary. The design allows easy scalability for adding more libraries, book categories, and multi-location tracking.

Authentication Workflow

User Registration (POST /api/auth/register)

1. User submits registration details (name, email, password, contact, role, library ID).
2. Password is hashed using bcrypt.
3. Data is saved in the users table with a default role of Reader.
4. Response: 201 Created with success message.

User Login (POST /api/auth/login)

1. User submits credentials (email & password).
2. Credentials are validated against the database.
3. If valid, a JWT token is generated and returned.
4. Token contains user ID, role, and library ID for authorization.

JWT Authentication Middleware (jwt.go)

• Extracts JWT token from the Authorization header.
• Validates the token.
• Sets user claims in context for role-based access.

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Book Management Workflow

Add Book (POST /api/books)

1. Admin submits book details (ISBN, title, author, copies, etc.).
2. If book exists, copies are incremented.
3. If book is new, a new record is created in book_inventory.

Remove Book (POST /api/books/remove)

1. Admin selects a book via ISBN.
2. Requested number of copies are deducted from the inventory.
3. If all copies are removed, the book record is deleted.

Update Book (PUT /api/books/:isbn)

1. Admin submits updated details (title, author, language, etc.).
2. Changes are applied to the book_inventory table.

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Request Handling Workflow

Raise Book Request (POST /api/requestEvents)

1. Readers can request up to 4 active book requests.
2. System checks book availability before processing request.
3. Request is stored in request_events with status Issue.

Approve / Reject Request (PUT /api/issueRequests/:id)

1. Admin reviews the request.
2. If approved:
   • Available book copies are decremented.
   • Request status is updated to Approved.
3. If rejected, request status is updated to Rejected.

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Book Issue & Return Workflow

Issue Book (POST /api/issueRegistry)

1. Approved requests result in book issuance.
2. Entry is created in issue_registry with expected return date.
3. Book’s available copies are reduced in book_inventory.

Return Book (POST /api/issueRegistry/return)

1. User returns the book.
2. Admin marks return date in issue_registry.
3. Available copies are incremented back in book_inventory.

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Admin & Owner Management Workflow

Assign Admin (POST /api/owner/assign-admin)

1. Owner selects a user via email.
2. User’s role is updated to LibraryAdmin.

Revoke Admin (POST /api/owner/revoke-admin)

1. Admin privileges are revoked.
2. User is demoted to Reader.

Audit Logs (GET /api/owner/audit-logs)

1. Tracks all admin actions (book additions, role changes, request approvals).

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API Endpoints Summary

Authentication

• POST /api/auth/register → Register new user
• POST /api/auth/login → User login & JWT token generation

Library Management

• POST /api/library → Create a new library
• GET /api/libraries → Get all libraries

Book Inventory

• POST /api/books → Add/increment book copies
• GET /api/books → Retrieve all books
• POST /api/books/remove → Remove book copies
• PUT /api/books/:isbn → Update book details

Book Requests

• POST /api/requestEvents → Request book issue
• GET /api/issueRequests → Get all book requests
• PUT /api/issueRequests/:id → Approve/reject issue request

Issue & Return

• POST /api/issueRegistry → Issue a book
• POST /api/issueRegistry/return → Return a book

Admin Actions

• POST /api/owner/assign-admin → Assign admin role
• POST /api/owner/revoke-admin → Revoke admin role
• GET /api/owner/audit-logs → Retrieve audit logs