chore(inventory): convert to dml (#10569)

Fixes: FRMW-2848

Co-authored-by: Harminder Virk <1706381+thetutlage@users.noreply.github.com>

packages/modules/inventory/src/utils/apply-decorators.ts

@@ -0,0 +1,45 @@
+import {
+  BigNumber,
+  isDefined,
+  MathBN,
+  toMikroORMEntity,
+} from "@medusajs/framework/utils"
+import { Formula, OnInit } from "@mikro-orm/core"
+
+import InventoryItem from "../models/inventory-item"
+import InventoryLevel from "../models/inventory-level"
+
+function applyHook() {
+  const MikroORMEntity = toMikroORMEntity(InventoryLevel)
+
+  MikroORMEntity.prototype["onInit"] = function () {
+    if (isDefined(this.stocked_quantity) && isDefined(this.reserved_quantity)) {
+      this.available_quantity = new BigNumber(
+        MathBN.sub(this.raw_stocked_quantity, this.raw_reserved_quantity)
+      )
+    }
+  }
+
+  OnInit()(MikroORMEntity.prototype, "onInit")
+}
+
+function applyFormulas() {
+  const MikroORMEntity = toMikroORMEntity(InventoryItem)
+
+  Formula(
+    (item) =>
+      `(SELECT SUM(reserved_quantity) FROM inventory_level il WHERE il.inventory_item_id = ${item}.id AND il.deleted_at IS NULL)`,
+    { lazy: true, serializer: Number, hidden: true, type: "number" }
+  )(MikroORMEntity.prototype, "reserved_quantity")
+
+  Formula(
+    (item) =>
+      `(SELECT SUM(stocked_quantity) FROM inventory_level il WHERE il.inventory_item_id = ${item}.id AND il.deleted_at IS NULL)`,
+    { lazy: true, serializer: Number, hidden: true, type: "number" }
+  )(MikroORMEntity.prototype, "stocked_quantity")
+}
+
+export const applyEntityHooks = () => {
+  applyHook()
+  applyFormulas()
+}