Buy X get Y: discount items already in the cart - GoGoGo 折扣优惠

Buy X get Y discounts eligible items that are already in the cart. It does not add products automatically. Use automatic gifts when the system should add a qualifying gift.

Configuration

Add 买 X 件，另 Y 件减价 (Buy X items, discount another Y).
Enter 需购买件数 X (Purchase quantity X) and 购物车中享优惠件数 Y (Discounted quantity Y).
Choose purchase scope and discounted-item scope separately.
Set the discount type and value. Enter percentage 100 to make the discounted items free.
Optionally set 每单最多优惠组数（可选） (Maximum groups per order).
Save and activate. Add both purchase and discounted items before testing checkout.

Same-product example: buy one, get another half price

Use product P for both scopes, X = 1, Y = 1, and 50% off. Each P costs 60.

Cart	Expected result without a group limit
1 P	No offer; one unit cannot serve both roles
2 P	One unit saves 30; total 90
3 P	Still only one complete offer group
4 P	Two groups; two units each save 30

For overlapping scopes, the rule reserves purchase quantities before selecting discounted quantities. Among different prices, the current implementation discounts lower-priced eligible units first. For fixed savings, check the amount per group rather than treating it as a final item price. See the buy-one-get-one scenario.