only one per customer...

I posted this before, but maybe there are some new members who possibly made this happen, you never know.....

I have a cart owner who wants to limit the sale of one particular item to "One per customer" (not just one per order, that's easy). I know, he can go in if they order a second time and just delete the order, but this is something he wants to work on it's own. I currently have that one item outside of the cart system, using a cookie to track the buyer (I would try to do it within the cart system, but I have had no success integrating non-cart cookies into the cart system), but if the buyer is savvy, they can delete the cookie to circumvent the lockout. I need something that can be added to the database that says "already bought" so the user cannot possibly bypass the system to buy a second one.
I have tried a few things, but nothing has worked so far. I usually figure these things out eventually, but I'm tired of hitting my head against the wall on this one.

You could build a test in that checks when the product is added to the cart is it set to 1 per customer ... then not allow it to be added and post a message ...

This would require some custom coding but it can be done ...

That's what I am attempting to do, but my experience is limited..... I was hoping for a few places to start looking for where I can hijack the cart process for this one item.

/includes/main_cart_actions.php manages all the cart actions ...

You need to catch the products_id on the way in ...

Then do a check on the orders the customer has made to see if they purchased this product before ... as in do any of the orders have orders_products that match the products_id for this product ...

If so, stop the add to cart before it happens and toss out a message that says: no way jelly bean ...

Thanks, I'm sure I'll be back on this one.....
It's the most involved edit I've done yet.