Expense Tracker API (FastAPI)

This is the backend for the Expense Tracker web application. It is a robust and secure RESTful API built with Python and FastAPI that handles user authentication, expense management, and data processing.

Core Features

• Secure Authentication: Uses JWT (JSON Web Tokens) for secure user signup, login, and session management. API endpoints are protected, ensuring users can only access their own data.
• Full CRUD Functionality: Provides complete Create, Read, Update, and Delete operations for expense records.
• Data Validation: Leverages Pydantic models to ensure all incoming and outgoing data is well-structured and valid.
• CSV Export: An endpoint to export all of a user's expense data into a downloadable CSV file.
• Database Agnostic: Built with SQLAlchemy ORM, allowing for easy switching between SQLite (for development) and PostgreSQL (for production).
• Containerized: Includes a Dockerfile for easy, consistent deployment on services like Render.

Tech Stack

• Framework: FastAPI
• Database ORM: SQLAlchemy
• Authentication: Passlib for password hashing, python-jose for JWT management.
• Data Validation: Pydantic
• Server: Uvicorn
• Database Drivers: psycopg2-binary for PostgreSQL, sqlite for development.

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Getting Started

Follow these instructions to get the backend server running on your local machine.

Prerequisites

• Python 3.9+
• pip package manager

Installation & Setup

1. Clone the repository:

   git clone https://github.com/David234-star/Expense-Tracker-Backend.git
   cd Expense-Tracker-Backend/backend

2. Create and activate a virtual environment:

   # For macOS/Linux
   python3 -m venv venv
   source venv/bin/activate
   
   # For Windows
   python -m venv venv
   .\venv\Scripts\activate

3. Install the required dependencies:

   pip install -r requirements.txt

4. Set up your environment variables: Create a file named .env in the backend directory. Copy the contents of .env.example (or the block below) into it and fill in your details. The SECRET_KEY should be a long, random, and secret string.

   # .env
   
   # For JWT Authentication. Generate a long random string for SECRET_KEY.
   # You can generate one using: openssl rand -hex 32
   SECRET_KEY="YOUR_SUPER_LONG_AND_RANDOM_SECRET_KEY"
   ALGORITHM="HS256"
   ACCESS_TOKEN_EXPIRE_MINUTES=60
   
   # For local SQLite development (default)
   DATABASE_URL="sqlite:///./sql_app.db"
   
   # For production with PostgreSQL, you would comment out the line above and use this:
   # DATABASE_URL="postgresql://user:password@host:port/dbname"

Running the Application

With your virtual environment activated, run the Uvicorn server:

uvicorn app.main:app --reload

The API will now be running at http://127.0.0.1:8000. You can access the interactive API documentation at http://127.0.0.1:8000/docs.

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API Endpoints

Method	Endpoint	Protection	Description
POST	/signup	Public	Creates a new user account.
POST	/token	Public	Logs in a user and returns a JWT access token.
GET	/users/me	Protected	Retrieves the profile of the currently logged-in user.
POST	/expenses/	Protected	Adds a new expense record for the current user.
GET	/expenses/	Protected	Retrieves all expense records for the current user.
PUT	/expenses/{expense_id}	Protected	Updates an existing expense record.
DELETE	/expenses/{expense_id}	Protected	Deletes an existing expense record.
GET	/export/csv	Protected	Exports all user expenses to a CSV file.

Deployment

This application is ready to be deployed on Render.

1. Push your code to a GitHub repository.
2. On Render, create a new "Web Service" and connect it to your repository.
3. Set the runtime to Docker.
4. Add the environment variables from your .env file to the Render environment settings. If using Render's PostgreSQL, use the provided internal DATABASE_URL.
5. Deploy!