Buy 2,3r. at 1/2price. Buy 3, 4th. is Free

I am using opencart to design an inkcartridge and toner cartridge store.
categories = remanufactured, new(oem), compatible

In the remanufactured and compatible categories only, both inkjet and toners, I want to be able to give the following special. The special should be available whenever we decide, not as a standard thing.

The special is:
1. buy 2 toners and the 3rd one has a 50% discount. The one with the discount is the one with lowest price.
That is, buy 2 get the 3rd. one on 50% disc.

2. buy 3 toners and get a 4th. toner cartridge for Free. Buy 3 get 1 Free (the one with the lowest price).

Can this be done?

My email is admin@br-e-solutions.com

Thanks,
Irving Billigue

By default OpenCart is not able to do it that way.

If I understand you correctly, you want the ability to describe the product specials rule on a per category basis. In the model, we'd need another DB table, e.g. category_product_special, with at least 'category_id', 'min_qty' and 'percent_price' as its fields. Then, whenever Opencart calls the cart->getProducts(), which queries the DB, it would modify the resulting prices for some of the products, and the cart page would show it immediately. All of this would require some modifications of the Opencart code, but I think it is doable.

Send me a PM if interested.