💳 Payment API

This is a back-end RESTful API developed with FastAPI and SQLAlchemy to simulate a simplified payment system.

The project implements core functionalities like user and shopkeeper management, secure money transfers, external service integration for transaction authorization and notifications, and a robust testing suite.

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🚀 Getting Started

Follow these steps to set up and run the project locally.

✅ Prerequisites

Make sure you have the following installed:

• Python 3.8+
• pip (Python package installer)
• PostgreSQL (database server)
• DBeaver or pgAdmin (database client tool)

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1. Clone the Repository

git clone https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip  
cd payment-api

2. Set up the Python Virtual Environment

Create and activate a virtual environment to manage project dependencies.
# Create the virtual environment
python -m venv enviroment

# Activate the virtual environment
# On Windows
.\enviroment\Scripts\activate
# On macOS/Linux
source enviroment/bin/activate

3. Install Dependencies

pip install -r https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip

4. Configure Environment Variables

Create a .env file in the root directory and add the following variables:
# PostgreSQL database connection string
# Format: postgresql://<user>:<password>@<host>:<port>/<database>
DB_URL="postgresql://postgres:postgres@localhost:5432/your_database_name"

# Notifiers to be used (separate multiple services with a comma)
# Options: log, mock, twilio
NOTIFIERS="log, mock, twilio"

# Twilio account details (only required if "twilio" is in NOTIFIERS)
TWILIO_ACCOUNT_SID="your_twilio_account_sid"
TWILIO_AUTH_TOKEN="your_twilio_auth_token"

5. Create the Database Tables

Run the following SQL commands inside your PostgreSQL database:
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(200) NOT NULL,
    cpf_cnpj VARCHAR(14) NOT NULL UNIQUE,
    email VARCHAR(200) NOT NULL UNIQUE,
    balance DECIMAL(10, 2) DEFAULT 0.00,
    phone VARCHAR(11) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE transactions (
    id SERIAL PRIMARY KEY,
    source_id INT NOT NULL,
    destination_id INT NOT NULL,
    value DECIMAL(10, 2) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (source_id) REFERENCES users(id),
    FOREIGN KEY (destination_id) REFERENCES users(id)
);

5.1 Alternative: Creating Tables and Populating with a Python Script

First, ensure your PostgreSQL database (e.g., a database named db) has been created. The command below will create the necessary tables within an existing database, but it will not create the database itself. You can create the tables by running a Python command that uses SQLAlchemy to generate the schema from your models.

# Make sure your virtual environment is activated
# And your .env file is configured correctly

python -c "from https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip import Base, engine; https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip(bind=engine)"

Once the tables are created, you can add test users by running the utility script from your project's root directory:

python https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip

This script will add the "Jane Smith" user to your database, allowing you to run transactions and test your API. You can modify the script to add more users as needed.

6. Run the Application

Start the API server using Uvicorn:
uvicorn main:app --reload
The API documentation will be available at:
👉 http://127.0.0.1:8000/docs

⚙️ Project Structure

payment-api/
│── https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip                # Main application entry point
│── database/              # Database connection and models
│   └── https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip
│── https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip           # Unit tests with pytest
│── .env                   # Environment variables
│── https://github.com/thaysvs2/payment-api/raw/refs/heads/master/database/api-payment-contester.zip       # Project dependencies

🧪 Running Tests

Run all tests with:
pytest

✅ Implemented Features

User and Shopkeeper Models: Differentiates between two user types.

Unique Constraints: Enforces unique CPF/CNPJ and email addresses.

Money Transfer Logic: Allows money transfer between users and to shopkeepers.

Shopkeeper Restrictions: Prevents shopkeepers from initiating transfers.

Balance Validation: Checks for sufficient balance before a transaction.

External Service Integration: Integrates with mock services for transaction authorization and notifications.

Atomic Transactions: Ensures all operations are completed or rolled back.

RESTful API: Clean and well-structured API using FastAPI.

🛠️ Technologies Used

Python 3.10+

FastAPI: High-performance, easy-to-use API framework

SQLAlchemy: ORM and SQL toolkit

psycopg2: PostgreSQL driver for Python

Twilio: SMS notification service

python-dotenv: Environment variables management

Pytest: Testing framework

httpx: HTTP client for FastAPI tests