feat(): added compute actions for buyget promotions (#6255)

what:

- computes actions for buyget promotion (RESOLVES CORE-1700)

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

@@ -0,0 +1,101 @@
+import { PromotionTypes } from "@medusajs/types"
+import {
+  ApplicationMethodTargetType,
+  ComputedActions,
+  MedusaError,
+  PromotionType,
+} from "@medusajs/utils"
+import { areRulesValidForContext } from "../validations/promotion-rule"
+import { computeActionForBudgetExceeded } from "./usage"
+
+export function getComputedActionsForBuyGet(
+  promotion: PromotionTypes.PromotionDTO,
+  itemsContext: PromotionTypes.ComputeActionContext[ApplicationMethodTargetType.ITEMS],
+  methodIdPromoValueMap: Map<string, number>
+): PromotionTypes.ComputeActions[] {
+  const buyRulesMinQuantity =
+    promotion.application_method?.buy_rules_min_quantity
+  const applyToQuantity = promotion.application_method?.apply_to_quantity
+  const buyRules = promotion.application_method?.buy_rules
+  const targetRules = promotion.application_method?.target_rules
+  const computedActions: PromotionTypes.ComputeActions[] = []
+
+  if (!itemsContext) {
+    throw new MedusaError(
+      MedusaError.Types.INVALID_DATA,
+      `"items" should be present as an array in the context to compute actions`
+    )
+  }
+
+  if (!Array.isArray(buyRules) || !Array.isArray(targetRules)) {
+    return []
+  }
+
+  const validQuantity = itemsContext
+    .filter((item) => areRulesValidForContext(buyRules, item))
+    .reduce((acc, next) => acc + next.quantity, 0)
+
+  if (
+    !buyRulesMinQuantity ||
+    !applyToQuantity ||
+    buyRulesMinQuantity > validQuantity
+  ) {
+    return []
+  }
+
+  const validItemsForTargetRules = itemsContext
+    .filter((item) => areRulesValidForContext(targetRules, item))
+    .sort((a, b) => {
+      return b.unit_price - a.unit_price
+    })
+
+  let remainingQtyToApply = applyToQuantity
+
+  for (const method of validItemsForTargetRules) {
+    const appliedPromoValue = methodIdPromoValueMap.get(method.id) || 0
+    const multiplier = Math.min(method.quantity, remainingQtyToApply)
+    const amount = method.unit_price * multiplier
+    const newRemainingQtyToApply = remainingQtyToApply - multiplier
+
+    if (newRemainingQtyToApply < 0 || amount <= 0) {
+      break
+    } else {
+      remainingQtyToApply = newRemainingQtyToApply
+    }
+
+    const budgetExceededAction = computeActionForBudgetExceeded(
+      promotion,
+      amount
+    )
+
+    if (budgetExceededAction) {
+      computedActions.push(budgetExceededAction)
+
+      continue
+    }
+
+    methodIdPromoValueMap.set(method.id, appliedPromoValue + amount)
+
+    computedActions.push({
+      action: ComputedActions.ADD_ITEM_ADJUSTMENT,
+      item_id: method.id,
+      amount,
+      code: promotion.code!,
+    })
+  }
+
+  return computedActions
+}
+
+export function sortByBuyGetType(a, b) {
+  if (a.type === PromotionType.BUYGET && b.type !== PromotionType.BUYGET) {
+    return -1
+  } else if (
+    a.type !== PromotionType.BUYGET &&
+    b.type === PromotionType.BUYGET
+  ) {
+    return 1
+  } else {
+    return 0
+  }
+}

packages/promotion/src/utils/compute-actions/index.ts

@@ -1,3 +1,4 @@
+export * from "./buy-get"
 export * from "./items"
 export * from "./order"
 export * from "./shipping-methods"