Leave Management System

A comprehensive web application designed to streamline the leave management process for organizations. It enables employees to submit leave requests, while administrators can efficiently manage and approve them.

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Problem Statement & Objective

Build an MVP Leave Management System for a startup with 50 employees. The HR team should be able to:

• Add employees with details (Name, Email, Department, Joining Date).
• Apply, approve, and reject leave requests.
• Track leave balance for each employee.

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Edge Cases Handled

• Applying for leave before joining date is disallowed.
• Applying for more leave days than available balance is rejected.
• Overlapping leave requests by the same employee are prevented.
• Operations on non-existent employees return appropriate errors.
• Invalid date inputs (e.g., end date before start date) are validated.
• Leave cannot be applied for past dates.
• Concurrent approval requests are handled safely to avoid inconsistencies.

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Assumptions

• Each employee has a fixed annual leave quota reset yearly.
• Leave types (Paid, Sick, Casual) are predefined but extensible.
• Only Admin/HR can approve or reject leave requests.
• Leave balance is decremented only upon approval.
• Authentication via JWT with token expiry of 24 hours.
• Partial day leaves are not handled in MVP.
• Employees can view their leave balance and history.

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High-Level System Design

• Frontend: React-based SPA with separate Admin and Employee views.
• Backend: REST API built with Node.js and Express handling all business logic and validations.
• Database: MongoDB storing employees, leave requests, and user credentials.
• API-DB Interaction: APIs validate input, check constraints, update DB documents atomically.
• Scaling:
  • Initially handles 50 employees with a single server instance.
  • For scaling to 500+ employees, horizontal scaling via multiple stateless backend instances behind a load balancer.
  • Database optimizations like indexing, query optimization, and possible sharding.
  • Future microservices separation for user management and leave processing.

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Project Structure

The project is organized into two main directories:

• client: Contains the frontend application built with React.
• server: Hosts the backend API developed using Node.js and Express.

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Setup Instructions

Prerequisites

• Node.js (v16 or higher)
• npm (v8 or higher)
• PastgreSql database (local or cloud)

Installation Steps

1. Clone the Repository

   git clone https://github.com/HeatBlastee/Leave-Management-System.git
   cd Leave-Management-System

2. Set Up the Backend

   • Navigate to the server directory:

     cd server

   • Install dependencies:

     npm install

   • Create a .env file and configure the following variables:

     PORT=5000
     DATABASE_URL=your_mongodb_connection_string
     JWT_SECRET=your_jwt_secret_key
     

   • Start the server:

     npm run dev

3. Set Up the Frontend

   • Navigate to the client directory:

     cd ../client

   • Install dependencies:

     npm install

   • Create a .env file and configure the following variable:

     VITE_BACKEND_URL=http://localhost:8000
     

   • Start the frontend:

     npm run dev

4. Credentials

• Admin: email: admin@email.com password: 123456

• Employee: email: sunilkumar@gmail.com password: 123456

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Features

• Employee Module:

  • User authentication and authorization using JWT.
  • Submit leave requests with dates and types.
  • View leave balance and history.

• Admin Module:

  • Manage employee records (add, update, delete).
  • View and manage leave requests.
  • Access admin-only stats and reports.

• Authentication & Authorization:

  • Secure endpoints using requireAuth middleware to verify JWT.
  • Role-based access control via requireAdmin middleware.

• User Interface:

  • Responsive design for seamless experience across devices.
  • Real-time status updates for leave requests.

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🔌 API Endpoints

Authentication (/auth)

• POST /register-admin: Register an admin (protected in production).
• POST /create-employee: Create an employee account (Admin only).
• POST /login: Authenticate user and receive JWT token.
• GET /me: Get logged-in user profile.

Employees (/employees)

• GET /: Get all employees (Admin only).
• GET /:id: Get employee details by ID.
• PUT /:id: Update employee details (Admin only).
• DELETE /:id: Delete an employee (Admin only).

Leaves (/leaves)

• POST /: Apply for leave (Authenticated users).
• GET /: Get leave requests (Admins get all, employees get own).
• PUT /:id/status: Update leave status (Admin only).

Admin (/api/admin)

• GET /stats: Get admin stats (Admin only).

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Security Considerations

• Admin registration route /api/auth/register-admin should be protected or disabled in production to prevent unauthorized admin creation.
• All protected routes require a valid JWT token.
• Role-based middleware ensures only authorized users can access sensitive endpoints.
• Use HTTPS in production deployments.
• Consider adding security middlewares like Helmet and rate limiting.

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High-Level Design

Class Diagram

Main entities:

• User (Admin or Employee)
• Employee Profile
• Leave Request with status (Pending, Approved, Rejected)

Flow Diagram

• User registration/login → JWT issued.
• Employee applies for leave → Backend validates, checks balance and overlapping.
• Admin approves/rejects leave → Leave status updated, balance adjusted.
• Users can fetch their leave status and history.

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🚧 Potential Improvements

• Role-based access control with finer granularity.
• Email notifications on leave application status changes.
• Calendar integration for leave visualization.
• Support partial day leaves and multiple leave types.
• Two-factor authentication for enhanced security.

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🌐 Live Demo

• API Server: https://leave-manager-server.onrender.com
• Frontend Application: https://leavemanager-n3sg.onrender.com

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

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📸 Screenshots

Employee Dashboard

Admin Dashboard

Leave Request Form

Admin Leave

Admin Leave

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For detailed documentation and code walkthrough, please refer to the GitHub repository.