feat(ADM-018): completed feature

project/src/modules/inventory/domain/stock.ts

@@ -0,0 +1,30 @@
+export type StockState = 'available' | 'reserved' | 'sold' | 'incoming';
+
+export interface StockItem {
+  id: string;
+  variantId: string;
+  available: number;
+  reserved: number;
+  sold: number;
+  incoming: number;
+  createdAt: Date;
+  updatedAt: Date;
+}
+
+export interface StockCommand {
+  variantId: string;
+  quantity: number;
+}
+
+export type SetAvailableStockCommand = StockCommand;
+
+export interface Availability {
+  available: boolean;
+  availableQuantity: number;
+}
+
+export function assertPositiveQuantity(quantity: number): void {
+  if (!Number.isInteger(quantity) || quantity <= 0) {
+    throw new Error('Stock quantity must be a positive integer');
+  }
+}