Check stock availability when creating an order

Distribution/Features/Order/OrderService.cs

@@ -1,6 +1,7 @@
 using Distribution.Features.Item;
 using Distribution.Features.PriceList;
 using Distribution.Features.Store;
+using Distribution.Features.Stock;
 using Distribution.Infra.Authorization;
 using Distribution.Infra.UoW;
 using Distribution.Models;
@@ -12,6 +13,7 @@ public class OrderService(
     IOrderRepository repo,
     IStoreRepository storeRepo,
     IItemRepository itemRepo,
+    IStockRepository stockRepo,
     PriceListService priceListService,
     IUnitOfWork uow,
     ICurrentUserService currentUser,
@@ -56,6 +58,19 @@ public class OrderService(
         return requestedUnitPrice.Value;
     }
 
+    /// <summary>
+    /// checkStockAvailability (mainPlan.md §1): confirms the requested quantity does not exceed
+    /// total on-hand stock for the item, summed across every warehouse/vehicle location. Does not
+    /// reserve or decrement stock — actual decrement happens later at loading/delivery time
+    /// (04_loading_event.md / future 05-06 ride execution), not at order placement.
+    /// </summary>
+    private async Task<bool> HasSufficientStockAsync(Guid itemId, decimal quantity)
+    {
+        var balances = await stockRepo.GetBalancesByItemAsync(itemId);
+        var totalAvailable = balances.Sum(b => b.Quantity);
+        return quantity <= totalAvailable;
+    }
+
     public async Task<List<OrderResponse>> GetAllAsync()
     {
         var orders = (await repo.GetAllAsync()).Where(o => o.IsActive).ToList();
@@ -116,6 +131,8 @@ public class OrderService(
         var orderItems = new List<Models.OrderItem>();
         foreach (var i in request.Items)
         {
+            if (!await HasSufficientStockAsync(i.ItemId, i.Quantity)) return null;
+
             var unitPrice = await ResolveUnitPriceAsync(i.ItemId, i.UnitPrice, store, request.OrderDate);
             if (unitPrice is null) return null;