WooCommerce plugin

We have a basic B2B WooCommerce set up for clients. We require a custom plugin that will automatically add a "loyalty gift" product to each order, depending on some criteria. For every 10 products ordered from the category "Retail", a loyalty gift product will be added. However, we require the balances to carry over to future orders by the same client, so that they continue to receive a free loyalty gift product for every 10 products ordered from the "Retail" category. Example #1: A client orders 5 units from the "Retail" category. No loyalty gift product is added to this order. On their next order, the same client orders 8 units from the "Retail" category. One loyalty gift product is automatically added, as 5 units from the first order and 8 units from the second order equals 13 units, so they have earned one loyalty gift. When the same client places a third order, they will need to order at least 7 units from the "Retail" category to earn another loyalty gift product. Example #2: A client orders 24 units from the "Retail" category. Two loyalty gits are automatically added to the order (every 10 units from the "Retail" category earns one loyalty gift - therefore they would earn two gifts for this order, and the 4 units will carry over to the next order) On their next order, the same client orders 2 units from the "Retail" category. No loyalty gift is added, as they have not yet reached the next 10 units to earn a loyalty gift (4 units carried over from the first order, plus 2 units for the second order). When the same client places a third order, they will need to order at least 4 units from the "Retail" category to earn another loyalty gift product. We would like the ability to alter the ID of the loyalty gift product, and also the ability to modify/add additional categories that qualify. We would also like the ability to change the number of qualifying units. Thank you