Daily Expenses Sharing Application
This Daily Expenses Sharing Application is designed to manage shared expenses among users. It allows users to split expenses in different ways and track their individual contributions over time. It also provides a balance sheet feature for users to view and download their expense summaries.

Features
1. User Management
Registration: Users can create an account by providing their name, email, mobile number, and password.
Login: Users can log in to the system using their email and password, with authentication powered by JSON Web Tokens (JWT).
2. Expense Management
Add Expenses: Users can add expenses and split them among participants.
Equal Split: The expense is divided equally among all participants.
Exact Split: Specify the exact amount each participant owes.
Percentage Split: Specify the percentage each participant owes (total must sum up to 100%).
3. Balance Sheet
View and Download: Users can view their individual expenses, overall expenses, and download balance sheets.
4. Authentication and Authorization
JWT-based authentication to ensure that only registered users can access their data.
5. Data Validation and Error Handling
Input validation ensures data integrity (e.g., percentages must add up to 100% for the percentage-based split).
Comprehensive error handling provides useful messages in case of issues.
6. Performance Optimization
Efficient handling of large datasets using pagination and database indexing.
7. Testing
Unit and integration tests using Jest and Supertest to ensure application reliability.
Technologies Used
Node.js: Backend server
Express.js: Web framework
MongoDB: Database for storing user and expense data
Mongoose: ODM for MongoDB
JWT (JSON Web Tokens): User authentication and authorization
Express Validator: Input validation
Jest: Testing framework
Supertest: HTTP assertion library for testing APIs
bcryptjs: For password hashing and security
API Endpoints
User Endpoints
POST /api/users/register: Register a new user
POST /api/users/login: Login an existing user
GET /api/users/:id: Get user details (Protected route)
Expense Endpoints
POST /api/expenses: Add a new expense (Protected route)
GET /api/expenses/user/:userId: Get individual user's expenses (Protected route)
GET /api/expenses/overall: Get overall expenses for all users (Protected route)
GET /api/expenses/download: Download the balance sheet (Protected route)
Usage
The Daily Expenses Sharing Application is useful for managing and tracking shared expenses among groups of people. Whether you go on trips with friends, share rent, or split bills after social gatherings, this app makes it easy to ensure everyone pays their fair share.

Example Use Case
A user can register and log in to the system.
The user can then add an expense and choose how it will be split among participants: equally, by specific amounts, or by percentages.
After the expense is added, users can view and download balance sheets to see who owes what.
Main Features Highlight
User Authentication and Authorization: Ensures secure access to personal data.
Multiple Expense Splitting Methods: Supports equal, exact, and percentage-based expense splitting.
Balance Sheet Management: Users can view and download a balance sheet of their expenses.
Error Handling and Validation: Ensures data integrity and provides clear error messages.
Optimized for Large Datasets: Paginated results and indexed database fields for better performance.
Unit and Integration Testing: Tests ensure the reliability and correctness of the application.
Future Enhancements
User Notifications: Notify participants when a new expense is added.
Automated Settlements: Suggest settlement amounts between users based on the overall balance sheet.
Analytics Dashboard: Provide insights into spending patterns.

Steps to Run the Project
Prerequisites
Node.js: Ensure you have Node.js installed (version 14 or higher). You can download it from nodejs.org.
MongoDB: Make sure you have MongoDB installed and running. You can either install it locally or use a cloud service like MongoDB Atlas.
Postman (optional): To test the API endpoints, you can use Postman or any other API testing tool.
Step 1: Clone the Repository
Step 2: Navigate to the Project Directory
Change into the project directory: daily-expenses-sharing-app
Step 3: Install Dependencies
Install the necessary dependencies for the backend:
Step 4: Set Up Environment Variables
Create a .env file in the root directory of your project and add the following environment variables:
makefile
PORT=5000
MONGODB_URI=mongodb://localhost:27017/expensesDB
JWT_SECRET=your_jwt_secret
MONGODB_URI: Update this if you are using a cloud MongoDB service.
JWT_SECRET: Set a secret key for JWT authentication.
Step 5: Run the Application
Start the application using the following command:
The server should now be running on http://localhost:5000.
Step 6: Test the API Endpoints
You can use Postman or another API testing tool to test the API endpoints. Here are some endpoints to start with:
User Registration: POST /api/users/register
User Login: POST /api/users/login
Add Expense: POST /api/expenses
Retrieve Individual User Expenses: GET /api/expenses/user/:userId
Download Balance Sheet: GET /api/expenses/download

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