feat(order): order change actions engine (#6467)

packages/order/src/utils/actions/write-off-item.ts

@@ -0,0 +1,47 @@
+import { MedusaError, isDefined } from "@medusajs/utils"
+import { ChangeActionType } from "../action-key"
+import { OrderChangeProcessing } from "../calculate-order-change"
+
+OrderChangeProcessing.registerActionType(ChangeActionType.WRITE_OFF_ITEM, {
+  operation({ action, currentOrder }) {
+    const existing = currentOrder.items.find(
+      (item) => item.id === action.details.reference_id
+    )!
+
+    existing.written_off_quantity ??= 0
+    existing.written_off_quantity += action.details.quantity
+  },
+  revert({ action, currentOrder }) {
+    const existing = currentOrder.items.find(
+      (item) => item.id === action.details.reference_id
+    )!
+
+    existing.written_off_quantity -= action.details.quantity
+  },
+  validate({ action, currentOrder }) {
+    const refId = action.details?.reference_id
+    if (!isDefined(refId)) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_DATA,
+        "Details reference ID is required."
+      )
+    }
+
+    const existing = currentOrder.items.find((item) => item.id === refId)
+
+    if (!existing) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_DATA,
+        `Reference ID "${refId}" not found.`
+      )
+    }
+
+    const quantityAvailable = existing!.quantity ?? 0
+    if (action.details.quantity > quantityAvailable) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_DATA,
+        "Cannot claim more items than what was ordered."
+      )
+    }
+  },
+})