Thanks for the quick response siam.
See I can't change the price of a variant via an API. There is not such feature in cart APIs , I guess . Do you know some way of changing a product variant's price on the fly ?
Moreover I tried to create a hidden product instead with some deducted price but hidden products are blocked by the checkout process anyway. So this option is also wasted.
Also , I think I shouldn't use the discount codes API , since its an unsupported thing and I'll have to ask every user of my App to provide me their store credentials to use this discount API which is not good.
Your views please.
Thanks.