Can I vibe code Cross Sell?

Build an open-source Cross-Sell and Recommendation system for Shopify stores using Node.js, Next.js, and Tailwind CSS.

1. DATA MODEL & BACKEND ARCHITECTURE:
- Create a database schema (PostgreSQL / Prisma) storing: Merchant Credentials, Manual Cross-Sell Rules (source_product_id, target_product_ids, priority), and Co-Occurrence Cache (product_id_a, product_id_b, score).
- Build a background sync job that fetches historical Shopify orders via Admin GraphQL API, parses line items, and runs a co-occurrence query: `SELECT item_a, item_b, COUNT(*) FROM order_items GROUP BY item_a, item_b`. Store top pairs per product.

2. ADMIN UI (Next.js + App Bridge):
- Dashboard allowing store owners to define manual recommendations per product or collection.
- Fallback toggle: If manual rules do not exist, fall back to historical co-occurrence pairs; if co-occurrence lacks data, fall back to top global bestsellers.
- Rule manager with drag-and-drop ordering for target recommendations.

3. FRONTEND WIDGET ENGINE:
- Build a lightweight web component (JavaScript / Shadow DOM under 10KB) that embeds into Shopify Product Pages (PDP) and Cart Drawer.
- Fetch recommendations via a fast cached API endpoint (`/api/recommendations?product_id=X&limit=4`).
- Implement inline 'Add to Cart' functionality using standard Shopify Ajax Cart API (`/cart/add.js`).
- Handle inventory checks: do not render recommended items if available quantity is 0.

4. FAILURE MODES & EDGE CASES:
- If an item in the recommendation list goes out of stock, automatically filter it out on the client side without throwing errors.
- Prevent recursive recommendation loops (e.g., Item A recommends B, B recommends A in an infinite visual chain).
- Respect Shopify variant selections: if a recommended product has multiple options (size, color), display a variant selector dropdown inside the widget UI.

5. OUT OF SCOPE:
- Heavy ML real-time personalization algorithms.
- Multi-currency conversion logic (rely on native Shopify currency attributes on page).

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