Extract Catalog stock validation service

src/Catalog.API/Extensions/Extensions.cs

@@ -27,6 +27,7 @@ public static void AddApplicationServices(this IHostApplicationBuilder builder)
         builder.Services.AddTransient<IIntegrationEventLogService, IntegrationEventLogService<CatalogContext>>();
 
         builder.Services.AddTransient<ICatalogIntegrationEventService, CatalogIntegrationEventService>();
+        builder.Services.AddTransient<ICatalogStockValidationService, CatalogStockValidationService>();
 
         builder.AddRabbitMqEventBus("eventbus")
                .AddSubscription<OrderStatusChangedToAwaitingValidationIntegrationEvent, OrderStatusChangedToAwaitingValidationIntegrationEventHandler>()

src/Catalog.API/IntegrationEvents/CatalogStockValidationService.cs

@@ -0,0 +1,25 @@
+namespace eShop.Catalog.API.IntegrationEvents;
+
+public sealed class CatalogStockValidationService(CatalogContext catalogContext) : ICatalogStockValidationService
+{
+    public async Task<IntegrationEvent> ValidateStockAsync(int orderId, IEnumerable<OrderStockItem> orderStockItems)
+    {
+        var confirmedOrderStockItems = new List<ConfirmedOrderStockItem>();
+
+        foreach (var orderStockItem in orderStockItems)
+        {
+            var catalogItem = await catalogContext.CatalogItems.FindAsync(orderStockItem.ProductId);
+            if (catalogItem is not null)
+            {
+                var hasStock = catalogItem.AvailableStock >= orderStockItem.Units;
+                var confirmedOrderStockItem = new ConfirmedOrderStockItem(catalogItem.Id, hasStock);
+
+                confirmedOrderStockItems.Add(confirmedOrderStockItem);
+            }
+        }
+
+        return confirmedOrderStockItems.Any(c => !c.HasStock)
+            ? new OrderStockRejectedIntegrationEvent(orderId, confirmedOrderStockItems)
+            : new OrderStockConfirmedIntegrationEvent(orderId);
+    }
+}

src/Catalog.API/IntegrationEvents/EventHandling/OrderStatusChangedToAwaitingValidationIntegrationEventHandler.cs

@@ -1,7 +1,7 @@
 namespace eShop.Catalog.API.IntegrationEvents.EventHandling;
 
 public class OrderStatusChangedToAwaitingValidationIntegrationEventHandler(
-    CatalogContext catalogContext,
+    ICatalogStockValidationService stockValidationService,
     ICatalogIntegrationEventService catalogIntegrationEventService,
     ILogger<OrderStatusChangedToAwaitingValidationIntegrationEventHandler> logger) :
     IIntegrationEventHandler<OrderStatusChangedToAwaitingValidationIntegrationEvent>
@@ -10,23 +10,7 @@ public async Task Handle(OrderStatusChangedToAwaitingValidationIntegrationEvent
     {
         logger.LogInformation("Handling integration event: {IntegrationEventId} - ({@IntegrationEvent})", @event.Id, @event);
 
-        var confirmedOrderStockItems = new List<ConfirmedOrderStockItem>();
-
-        foreach (var orderStockItem in @event.OrderStockItems)
-        {
-            var catalogItem = catalogContext.CatalogItems.Find(orderStockItem.ProductId);
-            if (catalogItem is not null)
-            {
-                var hasStock = catalogItem.AvailableStock >= orderStockItem.Units;
-                var confirmedOrderStockItem = new ConfirmedOrderStockItem(catalogItem.Id, hasStock);
-
-                confirmedOrderStockItems.Add(confirmedOrderStockItem);
-            }
-        }
-
-        var confirmedIntegrationEvent = confirmedOrderStockItems.Any(c => !c.HasStock)
-            ? (IntegrationEvent)new OrderStockRejectedIntegrationEvent(@event.OrderId, confirmedOrderStockItems)
-            : new OrderStockConfirmedIntegrationEvent(@event.OrderId);
+        var confirmedIntegrationEvent = await stockValidationService.ValidateStockAsync(@event.OrderId, @event.OrderStockItems);
 
         await catalogIntegrationEventService.SaveEventAndCatalogContextChangesAsync(confirmedIntegrationEvent);
         await catalogIntegrationEventService.PublishThroughEventBusAsync(confirmedIntegrationEvent);

src/Catalog.API/IntegrationEvents/ICatalogStockValidationService.cs

@@ -0,0 +1,6 @@
+namespace eShop.Catalog.API.IntegrationEvents;
+
+public interface ICatalogStockValidationService
+{
+    Task<IntegrationEvent> ValidateStockAsync(int orderId, IEnumerable<OrderStockItem> orderStockItems);
+}