I would like to set up so that if stock = 0 the customer can either pre-purchase or register for notification when in stock. From CS-Cart "explanation" box:
Note that the 'Buy in advance' option requires a positive product amount while the 'Sign up for notification' option requires a non-positive amount. Also note that the 'Sign up for notification' option is not applied to products tracked with options.
What does "product amount" refer to? Inventory quantity in CS-Cart? The amount the customer wants to buy?
Also, what actually happens with these product options? Does the buy in advance option allow the sale to complete and then flag it as bought in advance? Does "Sign up for notification" keep an internal database or and automate notification as soon as CS-Cart stock becomes positive?