Mock Payment System with Automated Cart and Checkout Flow 🚀

This project provides a complete payment flow simulation using two FastAPI services:

Cart Service: Handles item additions and initiates the checkout process.
URL: http://localhost:8001
Payment Server: Processes payments and sends webhook notifications.
URL: http://localhost:8000

The flow mimics a real-world e-commerce payment process with these steps:

Adding items to a cart.
Initiating a checkout and sending a payment request.
Capturing the payment.
Sending and receiving a webhook notification.

Prerequisites

Python 3.9 or higher
Install the following Python packages:
```
pip install fastapi uvicorn requests
```
Install jq for JSON parsing:
- Ubuntu/Debian:
```
sudo apt-get install jq
```
- macOS:
```
brew install jq
```

Usage Instructions

Clone the Repository:

git clone https://github.com/r74tech/dummy-payment.git
cd dummy-payment

Start the Cart Service:

uvicorn cart_service:app --reload --port 8001

Ensure the Payment Server is Running:
- If not already running, start it on port 8000:
```
docker compose up -d --build
```
Run the Payment Flow Script: Make sure both services are running, then execute the script to test the complete flow:
```
./run_payment_flow.sh
```

Expected Output

=== Step 1: Get Access Token ===
Access Token: YHPGUNHOXHO3
=== Step 2: Add Item to Cart ===
Cart Response: {"msg":"Item item001 added to cart","cart":{"item001":{"quantity":2,"price":100.0}}}
=== Step 3: Start Checkout ===
Order ID: 2HXG07P5EU7R
Payment Token: YHPGUNHOXHO3
=== Payment Flow Completed Successfully ===

Docker Compose Logs:

INFO:     Started server process [8]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8001 (Press CTRL+C to quit)
INFO:     Started server process [7]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
INFO:     192.168.65.1:38645 - "POST /auth/token HTTP/1.1" 200 OK
INFO:     192.168.65.1:27506 - "POST /cart/add HTTP/1.1" 200 OK
INFO:     192.168.65.1:27507 - "POST /checkout HTTP/1.1" 200 OK
INFO:     127.0.0.1:53820 - "POST /payments/start HTTP/1.1" 200 OK
INFO:     127.0.0.1:53826 - "POST /payments/capture/YHPGUNHOXHO3 HTTP/1.1" 200 OK
INFO:     127.0.0.1:52438 - "POST /callback HTTP/1.1" 200 OK
Received Webhook: {'token': 'YHPGUNHOXHO3', 'transaction': {'status': 'captured', 'order_id': '2HXG07P5EU7R', 'amount': 200.0}}

sequenceDiagram
    participant User as User
    participant CartService as Cart Service (Port 8001)
    participant PaymentServer as Payment Server (Port 8000)

    User ->> CartService: POST /cart/add (item_id, quantity, price)
    CartService ->> User: Item added to cart (200 OK)

    User ->> CartService: POST /checkout (access-token: <token>)
    CartService ->> PaymentServer: POST /payments/start (order_id, amount, access-token)
    PaymentServer -->> CartService: Payment initiated (access_token)

    CartService ->> PaymentServer: POST /payments/capture/<access_token>
    PaymentServer -->> CartService: Payment captured successfully

    PaymentServer ->> CartService: POST /callback (token, transaction)
    CartService -->> PaymentServer: Webhook received successfully

Troubleshooting

Verify Services:
- Ensure both services are running on the correct ports:
  - Cart Service: http://localhost:8001
  - Payment Server: http://localhost:8000
Common Errors:
- Connection Refused: Verify that the services are running.
- jq not found: Install jq using the instructions above.
Check Logs:
- Use logs from the services to debug any issues:
```
tail -f uvicorn.log
```

Project Overview

This project offers a full payment workflow simulation, from cart management to payment capture and webhook notifications. It’s ideal for:

Testing e-commerce integrations
Simulating payment flows for development and security exercises
Mocking webhook handling scenarios

Feel free to extend this project with additional features like security challenges, error simulations, or support for additional payment methods.