Automatically offer gift product / apply voucher

[razvy]

Hi,

 

I need to make Prestashop 1.6 to automatically add a free gift to every cart that contains at least one product from a list of categories.

I could do it with using a cart rule, but this means that the customer needs to manually apply a voucher code to the cart and I don't want that/ I want the code to be applied automatically, without the customer intervention.

 

How can I achieve that?

Thank you