fix(promotion): percentage value is accounted for in buyget promotions (#11799)

what:

- allows percentage value to be considered for buy get percentage

FIXES https://github.com/medusajs/medusa/issues/11259

.changeset/friendly-comics-sort.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/promotion": patch
+---
+
+fix(promotion): percentage value is accounted for in buyget promotions

packages/modules/promotion/integration-tests/__tests__/services/promotion-module/compute-actions.spec.ts

@@ -4443,9 +4443,9 @@ moduleIntegrationTestRunner({
               },
             ],
             application_method: {
-              type: "fixed",
+              type: "percentage",
               target_type: "items",
-              value: 1000,
+              value: 100,
               allocation: "each",
               max_quantity: 1,
               apply_to_quantity: 1,
@@ -4623,11 +4623,11 @@ moduleIntegrationTestRunner({
             ],
             campaign_id: undefined,
             application_method: {
-              type: "fixed",
+              type: "percentage",
               target_type: "items",
               allocation: "each",
               max_quantity: 1,
-              value: 1000,
+              value: 100,
               apply_to_quantity: 4,
               buy_rules_min_quantity: 1,
               target_rules: [
@@ -4764,9 +4764,9 @@ moduleIntegrationTestRunner({
             buyXGetXPromotion = await createDefaultPromotion(service, {
               type: PromotionType.BUYGET,
               application_method: {
-                type: "fixed",
+                type: "percentage",
                 target_type: "items",
-                value: 2000,
+                value: 100,
                 allocation: "each",
                 max_quantity: 2,
                 apply_to_quantity: 2,
@@ -4827,13 +4827,13 @@ moduleIntegrationTestRunner({
             const buyXGetXPromotionBulk1 = await createDefaultPromotion(
               service,
               {
-                code: "BUY50GET1000",
+                code: "BUY50GET100",
                 type: PromotionType.BUYGET,
                 campaign_id: null,
                 application_method: {
-                  type: "fixed",
+                  type: "percentage",
                   target_type: "items",
-                  value: 20000,
+                  value: 100,
                   allocation: "each",
                   max_quantity: 1000,
                   apply_to_quantity: 1000,
@@ -4863,9 +4863,9 @@ moduleIntegrationTestRunner({
                 type: PromotionType.BUYGET,
                 campaign_id: null,
                 application_method: {
-                  type: "fixed",
+                  type: "percentage",
                   target_type: "items",
-                  value: 20000,
+                  value: 20,
                   allocation: "each",
                   max_quantity: 20,
                   apply_to_quantity: 20,
@@ -4910,11 +4910,11 @@ moduleIntegrationTestRunner({
                 action: "addItemAdjustment",
                 item_id: "item_cotton_tshirt",
                 amount: 2500,
-                code: "BUY50GET1000",
+                code: "BUY50GET100",
               },
               {
                 action: "addItemAdjustment",
-                amount: 50,
+                amount: 10,
                 code: "BUY10GET20",
                 item_id: "item_cotton_tshirt",
               },
@@ -4925,13 +4925,13 @@ moduleIntegrationTestRunner({
             const buyXGetXPromotionBulk1 = await createDefaultPromotion(
               service,
               {
-                code: "BUY50GET1000",
+                code: "BUY50GET100",
                 type: PromotionType.BUYGET,
                 campaign_id: null,
                 application_method: {
-                  type: "fixed",
+                  type: "percentage",
                   target_type: "items",
-                  value: 20000,
+                  value: 100,
                   allocation: "each",
                   max_quantity: 1000,
                   apply_to_quantity: 1000,
@@ -4961,9 +4961,9 @@ moduleIntegrationTestRunner({
                 type: PromotionType.BUYGET,
                 campaign_id: null,
                 application_method: {
-                  type: "fixed",
+                  type: "percentage",
                   target_type: "items",
-                  value: 20000,
+                  value: 20,
                   allocation: "each",
                   max_quantity: 20,
                   apply_to_quantity: 20,
@@ -5018,18 +5018,18 @@ moduleIntegrationTestRunner({
                   action: "addItemAdjustment",
                   item_id: "item_cotton_tshirt2",
                   amount: 1225,
-                  code: "BUY50GET1000",
+                  code: "BUY50GET100",
                 },
                 {
                   action: "addItemAdjustment",
                   item_id: "item_cotton_tshirt",
                   amount: 1275,
-                  code: "BUY50GET1000",
+                  code: "BUY50GET100",
                 },
                 {
                   action: "addItemAdjustment",
                   item_id: "item_cotton_tshirt2",
-                  amount: 50,
+                  amount: 10,
                   code: "BUY10GET20",
                 },
               ])

packages/modules/promotion/src/utils/compute-actions/buy-get.ts

@@ -200,10 +200,12 @@ export function getComputedActionsForBuyGet(
     const appliedPromoValue =
       methodIdPromoValueMap.get(item.id) ?? MathBN.convert(0)
     const multiplier = MathBN.min(targetItem.quantity, remainingQtyToApply)
-    const amount = MathBN.mult(
+    const applicableAmount = MathBN.mult(
       MathBN.div(item.subtotal, item.quantity),
       multiplier
     )
+    const applicablePercentage = promotion.application_method?.value ?? 100
+    const amount = MathBN.mult(applicableAmount, applicablePercentage).div(100)
 
     const newRemainingQtyToApply = MathBN.sub(remainingQtyToApply, multiplier)