CAtegory component making

docs/Category-Domain-Report.md

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+# Category Domain Report
+
+## Scope
+
+Sprint 4 added a complete Category Domain on top of the existing backend API contract. Backend endpoints and payload names were not changed.
+
+Existing backend category fields remain isolated as DTO input:
+
+- `categoryID`
+- `parentID`
+- `name`
+- `icon`
+- `priority`
+- `visible`
+- `categoriesCount`
+- `itemCount`
+- `names[]`
+
+The UI now consumes category domain models rather than backend-shaped category responses.
+
+## Implemented Files
+
+### DTO
+
+- `src/app/core/categories/dto/category.dto.ts`
+
+Defines `CategoryDto` and `CategoryNameDto` for existing backend category payloads. Compatibility fields for current mock/API variants are accepted only at the DTO boundary.
+
+### Domain Model
+
+- `src/app/core/categories/models/category-domain.model.ts`
+
+Frontend category model exposes:
+
+- `id`
+- `parentId`
+- `title`
+- `icon`
+- `priority`
+- `visible`
+- `itemCount`
+- `children[]`
+- `translations`
+
+No backend category naming is required by category UI consumers.
+
+### Mapper
+
+- `src/app/core/categories/mappers/category.mapper.ts`
+
+Maps backend DTOs into domain categories, including:
+
+- backend id normalization
+- parent id normalization
+- title fallback selection
+- `names[]` to `translations`
+- nested DTO flattening
+- visible-category filtering
+- priority sorting
+- duplicate id de-duplication
+
+### Tree Utilities
+
+- `src/app/core/categories/utils/category-tree.utils.ts`
+
+Supports:
+
+- flat list to tree
+- unlimited nesting
+- parent lookup
+- children lookup
+- breadcrumb generation
+- leaf detection
+- tree flattening for future lazy-loading compatibility
+
+### Repository Abstraction
+
+- `src/app/core/categories/repositories/category.repository.ts`
+- `src/app/core/categories/repositories/api-category.repository.ts`
+- `src/app/core/categories/category-repository.token.ts`
+
+`CategoryRepository` returns DTOs from the existing `GET /category` API. The injection token uses the existing runtime provider strategy and remains compatible with both mock and API modes. Mock mode continues to work through the existing mock-data interceptor.
+
+### Category Service
+
+- `src/app/core/categories/category.service.ts`
+
+Converts repository DTOs through the mapper and exposes domain methods:
+
+- all categories
+- category tree
+- root categories
+- category by id
+- children
+- parent
+- breadcrumb
+- leaf detection
+
+### Category Facade
+
+- `src/app/facades/platform/category.facade.ts`
+
+Exposes observable streams and state for:
+
+- all categories
+- category tree
+- root categories
+- category by id
+- selected category
+- breadcrumb
+- children
+
+### Product Compatibility
+
+- `src/app/core/products/models/product-domain.model.ts`
+- `src/app/core/products/providers/api-product-data.provider.ts`
+
+`ProductFacade.getCategories()` now resolves through `CategoryService`, so compatibility category access also returns the new category domain model.
+
+## UI Migration
+
+Updated category-facing UI consumers:
+
+- `src/app/pages/home/home.component.ts`
+- `src/app/pages/home/home.component.html`
+- `src/app/pages/category/subcategories.component.ts`
+- `src/app/pages/category/subcategories.component.html`
+- `src/app/pages/category/category.component.ts`
+
+The home page and subcategory page now consume `CategoryFacade` and `Category` domain models. Category route item loading still uses the existing product facade for product lists, without changing product/payment/auth contracts.
+
+## Validation
+
+Completed checks:
+
+- DTOs are isolated under `core/categories/dto`.
+- Category mapper exists and is the only category DTO-to-domain conversion point.
+- Category UI uses `CategoryFacade` and category domain models.
+- Category backend field names are contained to the category DTO/mapper boundary and compatibility internals.
+- Components do not use `HttpClient` for category data.
+- No authentication changes were made.
+- No payment changes were made.
+- No bootstrap contract changes were made.
+- No backend API contract changes were made.
+- Mock/API compatibility is preserved through the repository token and existing mock interceptor.
+
+Build validation passed:
+
+```bash
+npm run build
+```
+
+## Stop Point
+
+Category Domain implementation is complete for Sprint 4. Stop here for approval before starting the next domain or any Builder/Backoffice work.