Refactor CartService to use async methods for cart operations and integrate gRPC for backend synchronization

src/FrontOffice.Main/Utilities/CartService.cs

@@ -1,3 +1,6 @@
+using FrontOffice.BFF.ShopingCart.Protobuf.Protos.ShopingCart;
+using Google.Protobuf.WellKnownTypes;
+
 namespace FrontOffice.Main.Utilities;
 
 public record CartItem(long ProductId, string Title, string ImageUrl, long UnitPrice, int Quantity)
@@ -7,14 +10,21 @@ public record CartItem(long ProductId, string Title, string ImageUrl, long UnitP
 
 public class CartService
 {
+    private readonly ShopingCartContract.ShopingCartContractClient _client;
     private readonly List<CartItem> _items = new();
     public event Action? OnChange;
 
+    public CartService(ShopingCartContract.ShopingCartContractClient client)
+    {
+        _client = client;
+        _ = LoadFromServerAsync();
+    }
+
     public IReadOnlyList<CartItem> Items => _items.AsReadOnly();
     public long Total => _items.Sum(i => i.LineTotal);
     public int Count => _items.Sum(i => i.Quantity);
 
-    public void Add(Product product, int quantity = 1)
+    public async Task Add(Product product, int quantity = 1)
     {
         if (quantity <= 0) return;
         var existing = _items.FirstOrDefault(i => i.ProductId == product.Id);
@@ -28,9 +38,22 @@ public class CartService
             _items[idx] = existing with { Quantity = existing.Quantity + quantity };
         }
         Notify();
+
+        try
+        {
+            await _client.AddNewUserCartAsync(new AddNewUserCartRequest
+            {
+                ProductId = product.Id,
+                Count = quantity
+            });
+        }
+        catch
+        {
+            // Best-effort sync with backend; keep local state on failure
+        }
     }
 
-    public void UpdateQuantity(long productId, int quantity)
+    public async Task UpdateQuantity(long productId, int quantity)
     {
         var existing = _items.FirstOrDefault(i => i.ProductId == productId);
         if (existing is null) return;
@@ -42,20 +65,87 @@ public class CartService
         var idx = _items.IndexOf(existing);
         _items[idx] = existing with { Quantity = quantity };
         Notify();
+
+        try
+        {
+            await _client.UpdateUserCartAsync(new UpdateUserCartRequest
+            {
+                UserCartId = productId,
+                Count = quantity
+            });
+        }
+        catch
+        {
+            // Best-effort sync with backend; keep local state on failure
+        }
     }
 
-    public void Remove(long productId)
+    public async Task Remove(long productId)
     {
         _items.RemoveAll(i => i.ProductId == productId);
         Notify();
+
+        try
+        {
+            // Interpret Count=0 as remove from cart
+            await _client.UpdateUserCartAsync(new UpdateUserCartRequest
+            {
+                UserCartId = productId,
+                Count = 0
+            });
+        }
+        catch
+        {
+            // Best-effort sync with backend; keep local state on failure
+        }
     }
 
-    public void Clear()
+    public async Task Clear()
     {
+        var productIds = _items.Select(i => i.ProductId).ToList();
         _items.Clear();
         Notify();
+
+        try
+        {
+            foreach (var id in productIds)
+            {
+                await _client.UpdateUserCartAsync(new UpdateUserCartRequest
+                {
+                    UserCartId = id,
+                    Count = 0
+                });
+            }
+        }
+        catch
+        {
+            // Best-effort sync with backend; keep local state on failure
+        }
     }
 
     private void Notify() => OnChange?.Invoke();
-}
 
+    private async Task LoadFromServerAsync()
+    {
+        try
+        {
+            var response = await _client.GetAllUserCartAsync(new Empty());
+            _items.Clear();
+            foreach (var m in response.Models)
+            {
+                var item = new CartItem(
+                    ProductId: m.Id,
+                    Title: m.Title ?? string.Empty,
+                    ImageUrl: string.IsNullOrWhiteSpace(m.ImagePath) ? string.Empty : UrlUtility.DownloadUrl + m.ImagePath,
+                    UnitPrice: m.Price,
+                    Quantity: m.SaleCount > 0 ? m.SaleCount : 1);
+                _items.Add(item);
+            }
+            Notify();
+        }
+        catch
+        {
+            // If backend is unreachable or user is unauthenticated, fall back to local-only cart.
+        }
+    }
+}