My Drupal commerce site supports multiple payment gateways. One of the payment types should be paying by invoice. That means if you select invoice payment type during checkout process you don't have to enter any "real" payment info (credit card data or something), but at end site should send you invoice (pdf document) with instructions how to pay your order.
I've installed Invoice module: https://www.drupal.org/project/commerce_invoice
And if I understood well I should use actions and rules to send email after checkout is complete. Is that true?
But what puzzles me most is that this module doesn't provide invoice payment gateway. So I don't know how to achieve that when user is selecting payment method "Pay by invoice" method appears? Should I use some dummy (test) payment gateway or? What payment gateway should be used for invoice payment?
What Rules event should I use to detect that checkout process is finished, so I can send invoice.
Also, what action should I select to send email that contains invoice (with link to PDF document or PDF document attached)?