Automated Checkout Script Development

I need a lightweight, reliable auto-buy script that goes all the way through checkout, submitting payment and shipping details automatically once an item becomes available. The core requirement is completion of the full purchase flow; simply adding to cart or passively watching for price changes is not enough for this job.

I will supply the site URL, account credentials, and any API keys after we start. Your code should:

• Launch quickly, locate the product page, and keep retrying until stock appears.
• Fill in predefined buyer information, apply any discount codes I specify, and confirm the order.
• Return a clear success or failure response so I can trigger follow-up actions.

Please write clean, well-commented code and include a short README explaining setup, required libraries, and how to adjust item IDs or variants. Preference goes to solutions in Python, but I am open to JavaScript or another language if you can justify the advantage.

Deliver the finished script, dependency list, and basic test proof (screenshot or log) that shows it completing an order in a sandbox or demo environment.