Always provide best possible item price from combination of discounts

Hi

Say I have the following active discount types:

Line item discounts

1. Buy Products for Discount on All Selections

   • Buy at least item: 1
   • From entries: Product A
   • At the follwing discount: 10 % off

2. Buy Products for Discount on All Selections

   • Buy at least item: 1
   • From entries: Product B
   • At the follwing discount: 25 % off

3. Buy Products for Discount on All Selections

   • Buy at least item: 1
   • From entries: Product C
   • At the follwing discount: 30 % off

With one of each products the cart now looks something like this:

I also have another discount which gives 20 % off the entire order if the spent amount is more than 2000 including VAT:

Order discounts

1. Spend for Discount on Order

   • Spend at least: 2000 (incl. VAT)
   • Get the follwing discount: 20 % off

Because I always want to provide the best (lowest) possible price I want the 10 % line item discount to be replaced with a 20 % off that item. The products which get 25 % and 30 % off should remain as their discounts are better than the 20 % provided by the order campaign.

I have tried a few different setups, but I am not able to fully acheive what I want:

• If i leave the discounts as explained above and let the order discount have lower priority than the line item discounts, the order discount takes another 20 % off all the discounted products and any other products in the cart.

            Money orderDiscountTotal = _orderGroupCalculator.GetOrderDiscountTotal(cart);

 This is as expected as it returns the sum of all line items OrderDiscountValue, but it is not what I want.

• If provide a line item discount of 20 % when spent amount is more than 2000 (incl. VAT) another 20 % is taken off all products. Even previously discounted ones. I have tried playing around with sorting order and exclusion rules, but no luck.

• I have also tried finding the entries related to a given promotion, and checking the if the EntryDiscountValue is smaller than OrderDiscountValue.

If I do that, and set the EntryDiscountValue = OrderDiscountValue I sort of get what I want, but I'm unsure how this will affect any other cart totals retrievals down the line fx. when I create summary for order email etc.

Rough code from trying that out:

            foreach (ILineItem affectedLineItem in affectedLineItems)
            {
                var entryDiscountValue = affectedLineItem.GetEntryDiscountValue();
                var orderDiscountValue = affectedLineItem.GetOrderDiscountValue();
                if (entryDiscountValue < orderDiscountValue)
                {
                    decimal percentage = fulfilledOrderRewardDescriptions.FirstOrDefault().Percentage;
                    var result = affectedLineItem.PlacedPrice - (affectedLineItem.PlacedPrice - (affectedLineItem.PlacedPrice * percentage / 100));
                    cart.GetFirstForm().GetAllLineItems().FirstOrDefault(x => x.Code == affectedLineItem.Code).SetEntryDiscountValue(result);
                    _orderRepository.Save(cart);
                }
            }

Has anyone had to implement something similar to my use case? Or perhaps someone can point me towards are proper approach?