Refactor categories view with tree structure and improve product caching

src/FrontOffice.Main/Utilities/CategoryService.cs

@@ -25,7 +25,7 @@ public class CategoryService
         }
 
         var response = await _client.GetAllCategoriesAsync(new GetCategoriesRequest());
-        _cache = response.Categories
+        _cache = response.Models
             .Select(dto => new CategoryItem(
                 Id: dto.Id,
                 Title: dto.Title ?? dto.Name ?? string.Empty,

src/FrontOffice.Main/Utilities/ProductService.cs

@@ -98,7 +98,10 @@ public class ProductService
 
     public async Task<Product?> GetByIdAsync(long id)
     {
-        if (TryGetCachedProduct(id, out var cached)) return cached;
+        if (TryGetCachedProduct(id, out var cached) && HasDetailedData(cached))
+        {
+            return cached;
+        }
 
         try
         {
@@ -112,6 +115,11 @@ public class ProductService
         }
         catch
         {
+            if (cached is not null)
+            {
+                return cached;
+            }
+
             TryGetCachedProduct(id, out var result);
             return result;
         }
@@ -134,6 +142,8 @@ public class ProductService
                 Rate: m.Rate,
                 RemainingCount: m.RemainingCount
             );
+
+            p = PreserveCachedDetails(p);
             CacheProduct(p);
 
             list.Add(p);
@@ -142,6 +152,27 @@ public class ProductService
         return list;
     }
 
+    private Product PreserveCachedDetails(Product product)
+    {
+        if (_cache.TryGetValue(product.Id, out var entry))
+        {
+            var cached = entry.Product;
+            var hasGallery = cached.Gallery.Count > 0;
+            var hasCategories = cached.Categories.Count > 0;
+
+            if (hasGallery || hasCategories)
+            {
+                product = product with
+                {
+                    Gallery = hasGallery ? cached.Gallery : product.Gallery,
+                    Categories = hasCategories ? cached.Categories : product.Categories
+                };
+            }
+        }
+
+        return product;
+    }
+
     private Product MapAndCache(GetProductsResponse model)
     {
         var gallery = model.Gallery
@@ -202,6 +233,9 @@ public class ProductService
             .Where(entry => entry.Expiration > now)
             .Select(entry => entry.Product);
     }
+
+    private static bool HasDetailedData(Product product)
+        => product.Gallery.Count > 0 || product.Categories.Count > 0;
     
     private sealed record CacheEntry(Product Product, DateTime Expiration);
     private static string BuildUrl(string? path) =>