fix(utils,promotion): fix case where mutliple percentage promotions werent applied (#11992)

what:

- fix case where mutliple percentage promotions werent applied

packages/core/utils/src/totals/promotion/index.ts

@@ -9,12 +9,26 @@ function getPromotionValueForPercentage(promotion, lineItemTotal) {
   return MathBN.mult(MathBN.div(promotion.value, 100), lineItemTotal)
 }
 
-function getPromotionValueForFixed(promotion, lineItemTotal, lineItemsTotal) {
+function getPromotionValueForFixed(promotion, itemTotal, allItemsTotal) {
   if (promotion.allocation === ApplicationMethodAllocation.ACROSS) {
-    return MathBN.mult(
-      MathBN.div(lineItemTotal, lineItemsTotal),
+    const promotionValueForItem = MathBN.mult(
+      MathBN.div(itemTotal, allItemsTotal),
       promotion.value
     )
+
+    if (MathBN.lte(promotionValueForItem, itemTotal)) {
+      return promotionValueForItem
+    }
+
+    const percentage = MathBN.div(
+      MathBN.mult(itemTotal, 100),
+      promotionValueForItem
+    )
+
+    return MathBN.mult(
+      promotionValueForItem,
+      MathBN.div(percentage, 100)
+    ).precision(4)
   }
 
   return promotion.value
@@ -45,12 +59,84 @@ export function calculateAdjustmentAmountFromPromotion(
   promotion,
   lineItemsTotal: BigNumberInput = 0
 ) {
-  const quantity = getApplicableQuantity(lineItem, promotion.max_quantity)
-  const lineItemTotal = MathBN.mult(getLineItemUnitPrice(lineItem), quantity)
-  const applicableTotal = MathBN.sub(lineItemTotal, promotion.applied_value)
+  /*
+    For a promotion with an across allocation, we consider not only the line item total, but also the total of all other line items in the order.
+
+    We then distribute the promotion value proportionally across the line items based on the total of each line item.
+
+    For example, if the promotion is 100$, and the order total is 400$, and the items are:
+      item1: 250$
+      item2: 150$
+      total: 400$
+    
+    The promotion value for the line items would be:
+      item1: 62.5$
+      item2: 37.5$
+      total: 100$
+
+    For the next 100$ promotion, we remove the applied promotions value from the line item total and redistribute the promotion value across the line items based on the updated totals.
+
+    Example:
+      item1: (250 - 62.5) = 187.5
+      item2: (150 - 37.5) = 112.5
+      total: 300
+
+      The promotion value for the line items would be:
+      item1: $62.5
+      item2: $37.5
+      total: 100$
+  
+  */
+  if (promotion.allocation === ApplicationMethodAllocation.ACROSS) {
+    const quantity = getApplicableQuantity(lineItem, promotion.max_quantity)
+    const lineItemTotal = MathBN.mult(getLineItemUnitPrice(lineItem), quantity)
+    const applicableTotal = MathBN.sub(lineItemTotal, promotion.applied_value)
+
+    if (MathBN.lte(applicableTotal, 0)) {
+      return applicableTotal
+    }
+
+    const promotionValue = getPromotionValue(
+      promotion,
+      applicableTotal,
+      lineItemsTotal
+    )
+
+    return MathBN.min(promotionValue, applicableTotal)
+  }
+
+  /*
+    For a promotion with an EACH allocation, we calculate the promotion value on the line item as a whole.
+
+    Example:
+      item1: {
+        subtotal: 200$,
+        unit_price: 50$,
+        quantity: 4,
+      }
+      
+      When applying promotions, we need to consider 2 values:
+        1. What is the maximum promotion value?
+        2. What is the maximum promotion we can apply on the line item?
+      
+      After applying each promotion, we reduce the maximum promotion that you can add to the line item by the value of the promotions applied.
+      
+      We then apply whichever is lower.
+  */
+
+  const remainingItemTotal = MathBN.sub(
+    lineItem.subtotal,
+    promotion.applied_value
+  )
+  const unitPrice = MathBN.div(lineItem.subtotal, lineItem.quantity)
+  const maximumPromotionTotal = MathBN.mult(
+    unitPrice,
+    promotion.max_quantity ?? MathBN.convert(1)
+  )
+  const applicableTotal = MathBN.min(remainingItemTotal, maximumPromotionTotal)
 
   if (MathBN.lte(applicableTotal, 0)) {
-    return applicableTotal
+    return MathBN.convert(0)
   }
 
   const promotionValue = getPromotionValue(