Wordpress WooCommerce Subscription custom file output

I need the following logic when a subscription is purchased and active:
- Trigger on the correct hook after payment is successful for subscription
- Get from a custom DB table a free license code and assign it to the customer who placed the order
- Retrieve a remote text file (csv) from a FTP server
- Check if the user is already in this file, if yes update it, else add it and save the file to the FTP
- Add a customer note to the subscription with a custom welcome text + the license code

When a subscription status switch from Active to any other status
- Retrieve the file from the FTP and remove the line regarding the customer

As a developer I know this isn't a big deal, just saving my time here. Please do not ask for thousands $ for this, I won't accept.