Implement product categories CRUD operations with CMS integration

src/BackOffice.BFF.Application/ProductsCQ/Queries/GetCategories/GetCategoriesQueryHandler.cs

@@ -1,20 +1,67 @@
 using BackOffice.BFF.Application.Common.Interfaces;
+using CMSCategory = CMSMicroservice.Protobuf.Protos.Category;
+using CMSPruductCategory = CMSMicroservice.Protobuf.Protos.PruductCategory;
 
 namespace BackOffice.BFF.Application.ProductsCQ.Queries.GetCategories;
 
 public class GetCategoriesQueryHandler : IRequestHandler<GetCategoriesQuery, GetCategoriesResponseDto>
 {
+    private readonly IApplicationContractContext _context;
+
     public GetCategoriesQueryHandler(IApplicationContractContext context)
     {
-        // context is currently unused; reserved for future CMS integration
+        _context = context;
     }
 
     public async Task<GetCategoriesResponseDto> Handle(GetCategoriesQuery request, CancellationToken cancellationToken)
     {
-        // Stub implementation: returns empty list.
-        // When CMS protobuf package with Category support is available,
-        // this handler can be updated to call Category and PruductCategory services.
-        await Task.CompletedTask;
-        return new GetCategoriesResponseDto();
+        // Load all categories
+        var categoryRequest = new CMSCategory.GetAllCategoryByFilterRequest
+        {
+            Filter = new CMSCategory.GetAllCategoryByFilterFilter(),
+            PaginationState = new CMSMicroservice.Protobuf.Protos.PaginationState
+            {
+                PageNumber = 1,
+                PageSize = 1000
+            }
+        };
+
+        var categoriesResponse = await _context.Categories.GetAllCategoryByFilterAsync(categoryRequest, cancellationToken: cancellationToken);
+        var categories = categoriesResponse.Models ?? new();
+
+        // Load existing product-category relations for this product
+        var productCategoryRequest = new CMSPruductCategory.GetAllPruductCategoryByFilterRequest
+        {
+            Filter = new CMSPruductCategory.GetAllPruductCategoryByFilterFilter
+            {
+                ProductId = request.ProductId
+            },
+            PaginationState = new CMSMicroservice.Protobuf.Protos.PaginationState
+            {
+                PageNumber = 1,
+                PageSize = 1000
+            }
+        };
+
+        var productCategoriesResponse = await _context.ProductCategories.GetAllPruductCategoryByFilterAsync(productCategoryRequest, cancellationToken: cancellationToken);
+        var productCategories = productCategoriesResponse.Models ?? new();
+
+        var selectedIds = productCategories
+            .Select(pc => pc.CategoryId)
+            .ToHashSet();
+
+        var result = new GetCategoriesResponseDto
+        {
+            Items = categories
+                .Select(c => new CategoryItemDto
+                {
+                    Id = c.Id,
+                    Title = c.Title,
+                    Selected = selectedIds.Contains(c.Id)
+                })
+                .ToList()
+        };
+
+        return result;
     }
 }