'use cache';
import { cacheLife, cacheTag } from 'next/cache';

export async function getProduct(id: string) {
  cacheLife('products');  // Profile from next.config.ts
  cacheTag(`product:${id}`);
  
  // Pure read, no auth
  const supabase = createStaticClient();
  return supabase.from('products').select('id, title, price').eq('id', id).single();
}

import { revalidateTag, revalidatePath } from 'next/cache';

// After mutation
export async function updateProduct(id: string, data: ProductData) {
  // ... update logic
  
  revalidateTag(`product:${id}`);  // Specific product
  revalidateTag('products');       // Product listings
}

// ✅ Server Component - direct fetch
async function ProductPage({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params;
  const product = await getProduct(id);  // Cached server function
  return <ProductView product={product} />;
}

// ❌ Client Component - avoid for initial data
'use client';
function ProductPage({ id }) {
  const [product, setProduct] = useState(null);
  useEffect(() => { fetchProduct(id).then(setProduct) }, [id]);  // Bad
}

app/[locale]/
├── (main)/           # Public layout
│   ├── layout.tsx    # Shared header/footer
│   └── products/
├── (auth)/           # Auth layout
│   ├── layout.tsx    # Minimal UI
│   └── login/
└── (seller)/         # Seller layout
    ├── layout.tsx    # Seller nav
    └── dashboard/

// Server Component with cached data
async function CategoryPage({ params }) {
  const { slug } = await params;
  const products = await getCategoryProducts(slug);
  return <ProductGrid products={products} />;
}

// Small client island for interactivity
'use client';
function FilterSidebar({ onFilterChange }) {
  const [filters, setFilters] = useState({});
  // Handle user interaction
}

// Don't make entire pages client components
'use client';
export default function ProductPage() {
  // Everything is now client-side
}

// Don't fetch in useEffect for initial data
useEffect(() => {
  fetch('/api/products').then(r => r.json()).then(setProducts);
}, []);

// Don't create middleware.ts
// middleware.ts - NO!