# 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.