Guide on Building a Full-Stack Authentication System with Python and Next.js

This repository, Mumina04/app-authentication, implements a complete user authentication system that can be integrated into web applications. It uses Python for the backend to handle secure user login and registration, and Next.js (with TypeScript) for the frontend. The project provides a foundational framework for building modern web applications requiring user authentication, such as Software-as-a-Service (SaaS) platforms or internal enterprise tools.

Overview
Key Technologies
Project Structure
Setup Instructions
Authentication Flow
Common Debugging Issues

Overview

The repository implements a modern full-stack authentication mechanism where the backend handles user credentials, while the frontend manages user interactions such as login forms and token storage. With Python responsible for the backend operations like session management, password hashing, and user database handling, the Next.js frontend offers a responsive user interface for managing authentication workflows.

This architecture is common for web applications that require secure, scalable authentication solutions. The project likely follows best practices for secure password handling (e.g., hashing) and may support features like session-based authentication or JWT (JSON Web Tokens), which enables stateless user sessions.

Core Features:

User Registration: Allows new users to sign up with a secure method of storing passwords.
User Login: Validates user credentials and issues a session or token for future requests.
Token-based Authentication: The system likely uses JWTs, which securely transmit user identity and authorization between the frontend and backend.
Frontend-Backend Communication: The frontend securely sends user data (e.g., login credentials) to the backend API for processing, ensuring the user experience is smooth and data security is maintained.

Key Technologies

The project leverages a combination of modern web technologies to handle different aspects of the authentication process:

Python: The backend is written in Python and handles the core business logic for user authentication, such as validating credentials, managing sessions, and interacting with a database.
Next.js (TypeScript): The frontend is developed using Next.js, a React framework, for server-side rendering and API routes. TypeScript is used to add type safety to the JavaScript code, making it more reliable and easier to maintain.
JWT: Likely used for session management and secure authentication across stateless HTTP requests.
CSS and JavaScript: Minimal use of CSS to style the frontend components and JavaScript for frontend interactions such as form submission and token management.

Project Structure

The project is structured to keep backend and frontend components cleanly separated, ensuring ease of development and deployment:

app-authentication/
│
├── authentication_app/        # Python backend
│   ├── auth/                  # Handles authentication logic (register, login)
│   └── models/                # Database models, includes User models
│
├── my-nextjs-app/             # Next.js frontend
│   ├── components/            # UI components such as login and signup forms
│   ├── pages/                 # Next.js pages (login, signup)
│   └── api/                   # Frontend API routes for interacting with backend
│
├── README.md                  # Project documentation
├── requirements.txt           # Python dependencies
└── ...

Directory Breakdown

authentication_app/: This directory contains the backend logic for managing user authentication. It likely has code for registering users, validating login credentials, and generating tokens (JWTs).
my-nextjs-app/: The frontend, built using Next.js, manages the user interface for login and registration. It includes reusable components like forms and pages for interacting with the backend.
requirements.txt: Lists the Python dependencies required for the backend, including libraries for handling user authentication, password hashing, and possibly database management.

Setup Instructions (Beginner Friendly)

To run the application locally, follow these steps. If you are unfamiliar with some of the tools or commands, don't worry – each step is broken down with additional guidance.

Clone the repository:

First, you'll need to copy the project files from GitHub to your local machine. Open your terminal or command prompt and run the following command:

   git clone https://github.com/Mumina04/app-authentication.git

This will download the project into a folder named app-authentication. After cloning, navigate into the folder using:

   cd app-authentication

This command changes the directory to the newly cloned project.

Install Python dependencies:

Make sure Python 3 is installed on your machine. You can check if Python is installed by running:

   python --version

If you see a version number (e.g., Python 3.9.7), you are good to go. If not, you will need to install Python first.

Now, install the required Python packages using the pip package manager, which is used to install Python libraries. Run the following command inside the app-authentication directory:

   pip install -r requirements.txt

This will install all the necessary libraries listed in the requirements.txt file.

Set up the Next.js frontend:

Now, we need to set up the frontend (the part of the application users interact with). The frontend is built with Next.js, which requires Node.js to run.

Install Node.js: If you haven't installed Node.js, download and install it from here.
Navigate to the frontend folder: After installing Node.js, switch to the my-nextjs-app directory inside the project:
```
  cd my-nextjs-app
```
Install Node.js dependencies: In this folder, run the following command to install the dependencies for the frontend:
```
  npm install
```

This command installs all the necessary packages for the frontend, like React and Next.js.

Run the applications:

At this point, you're ready to run both the backend (Python) and frontend (Next.js) applications.

Start the backend server:

Go back to the app-authentication folder, where the backend code lives, using:
```
 cd ..
```
Now start the backend server with this command:
```
 python run_backend.py  # Make sure to replace this with the actual script if different
```
This command starts the backend, which handles user authentication, like registering users and verifying logins.
Start the Next.js frontend:

After starting the backend, go back to the my-nextjs-app folder:
```
 cd my-nextjs-app
```
Run the following command to start the Next.js frontend:
```
 npm run dev
```
By default, the frontend should be available at http://localhost:3000 in your browser.

You can open this URL in any web browser to interact with the login and registration forms provided by the application.

Authentication Flow

The project implements a typical authentication flow used in modern web applications:

User Registration:
- The user submits their registration details (e.g., email, password) via the frontend.
- The backend processes the request, hashes the password securely (likely using a library like bcrypt), and stores the user details in a database.
User Login:
- The user provides their credentials via the login form in the frontend.
- These credentials are sent to the backend, which verifies the username and password.
- Upon successful validation, the backend generates a JWT or session token, which is returned to the frontend.
Token Management:
- The frontend stores the token (in local storage or cookies) and includes it in subsequent requests to protected routes.
- The backend verifies the token for each request, ensuring the user is authenticated before granting access to sensitive resources.
Frontend Pages:
- Login and Signup Pages: These are handled by the Next.js pages under the /pages directory, responsible for rendering forms and sending requests to the backend API.
- Protected Routes: The frontend checks for a valid token before rendering certain pages, ensuring only authenticated users can access them.

Authentication Flow Diagram

To better understand the authentication process, here's a simple flowchart illustrating the flow between the user, frontend, and backend during the authentication process:

Common Debugging Issues

Here are some common issues you might encounter while setting up

the project and how to resolve them:

1. Python Version Issue

Problem: If the python --version command shows a version lower than Python 3, the application might not run as expected.
Solution: Download and install Python 3.x.

2. Pip Not Found

Problem: You might see an error saying "pip command not found."
Solution: Install pip by following the pip installation guide.

3. Node.js Missing

Problem: When trying to run npm install, you may get an error indicating Node.js is not installed.
Solution: Install Node.js from here.

4. Frontend Fails to Start (Port in Use)

Problem: If you get an error when starting the frontend (npm run dev) saying the port 3000 is already in use.
Solution: Either stop the application using port 3000 or specify a different port when running the command:
```
 npm run dev -- -p 3001
```

5. Backend Not Starting

Problem: If the backend fails to start, ensure that the entry point (python run_backend.py) is the correct file. You may also encounter errors if Python dependencies are missing.
Solution: Double-check the file names and ensure all required packages are installed using pip install -r requirements.txt.

For more information, visit the full app-authentication repository.