Service Layer

Controller (HTTP layer)
    │
    ├── Receives validated request
    ├── Calls service method
    └── Returns resource response

Service (Business layer)
    │
    ├── Executes domain logic
    ├── Coordinates multiple models
    ├── Dispatches events
    └── Calls other services via contracts

class ProductService
{
    // Public methods — called by controllers
    public function createProduct(array $data): Product
    {
        $product = Product::create([
            'title'           => $data['title'],
            'type'            => $data['type'],
            'status'          => $data['status'] ?? ProductStatus::DRAFT,
            'organization_id' => getTeamOrganization()->id,
        ]);

        $this->attachCategories($product, $data['categories'] ?? []);
        $this->createVariants($product, $data['variants']);

        return $product->load('variants', 'categories');
    }

    public function updateProduct(Product $product, array $data): Product
    {
        $product->update($data);

        if (isset($data['categories'])) {
            $product->categories()->sync($data['categories']);
        }

        return $product->fresh();
    }

    // Private methods — internal helpers
    private function attachCategories(Product $product, array $categoryIds): void
    {
        $product->categories()->attach($categoryIds);
    }

    private function createVariants(Product $product, array $variants): void
    {
        foreach ($variants as $variantData) {
            $product->variants()->create($variantData);
        }
    }
}

class OrderController extends Controller
{
    public function __construct(private OrderService $orderService) {}

    public function store(CreateOrderRequest $request): JsonResponse
    {
        // Controller: delegates to service
        $order = $this->orderService->createOrder($request->validated());

        // Controller: returns formatted response
        return new OrderResource($order);
    }

    public function confirm(string $id): JsonResponse
    {
        $order = Order::findOrFail($id);
        $this->authorize('update', $order);

        $order = $this->orderService->confirmOrder($order);

        return new OrderResource($order);
    }
}

class ProductServiceTest extends TestCase
{
    public function test_create_product_with_variants(): void
    {
        $service = app(ProductService::class);

        $product = $service->createProduct([
            'title'    => 'Test Product',
            'type'     => 'physical',
            'variants' => [
                ['sku' => 'TEST-001', 'price' => 10000],
            ],
        ]);

        $this->assertEquals('Test Product', $product->title);
        $this->assertCount(1, $product->variants);
    }
}