Cleaning things up and getting add item to cart working for anonymous or authenticated users.

src/ApplicationCore/Entities/ApplicationUser.cs

@@ -1,10 +0,0 @@
-using System.Security.Claims;
-
-namespace ApplicationCore.Entities
-{
-    public class ApplicationUser : ClaimsIdentity
-    {
-        public string UserId { get; set; }
-        public string UserName { get; set; }
-    }
-}

src/ApplicationCore/Entities/Basket.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.eShopWeb.ApplicationCore.Entities
 {
@@ -6,5 +7,21 @@ namespace Microsoft.eShopWeb.ApplicationCore.Entities
     {
         public string BuyerId { get; set; }
         public List<BasketItem> Items { get; set; } = new List<BasketItem>();
+
+        public void AddItem(int productId, decimal unitPrice, int quantity = 1)
+        {
+            if(!Items.Any(i => i.ProductId == productId))
+            {
+                Items.Add(new BasketItem()
+                {
+                    ProductId = productId,
+                    Quantity = quantity,
+                    UnitPrice = unitPrice
+                });
+                return;
+            }
+            var existingItem = Items.FirstOrDefault(i => i.ProductId == productId);
+            existingItem.Quantity += quantity;
+        }
     }
 }

src/ApplicationCore/Interfaces/IBasketService.cs

@@ -1,17 +1,13 @@
-using ApplicationCore.Entities;
-using Microsoft.eShopWeb.ApplicationCore.Entities;
-using System.Security.Principal;
+using Microsoft.eShopWeb.ApplicationCore.Entities;
 using System.Threading.Tasks;
 
 namespace ApplicationCore.Interfaces
 {
     public interface IBasketService
     {
-        Task<Basket> GetBasket(ApplicationUser user);
-    }
-
-    public interface IIdentityParser<T>
-    {
-        T Parse(IPrincipal principal);
+        Task<Basket> GetBasket(string basketId);
+        Task<Basket> CreateBasket();
+        Task<Basket> CreateBasketForUser(string userId);
+        Task UpdateBasket(Basket basket);
     }
 }

src/ApplicationCore/Interfaces/IIdentityParser.cs

@@ -0,0 +1,9 @@
+using System.Security.Principal;
+
+namespace ApplicationCore.Interfaces
+{
+    public interface IIdentityParser<T>
+    {
+        T Parse(IPrincipal principal);
+    }
+}