Complete OrbitStack qualifying tasks

[Phloraxx]

Submission checklist

Updated GitHub repository

https://github.com/Phloraxx/orbitstack/tree/fix/orbitstack-challenge

Working version

The application is working on the submitted branch and was verified with the test suite, TypeScript checks, Prisma validation, and a production Next.js build.

Bugs identified

• Pro free-shipping and a stackable free-shipping discount could apply the same shipping benefit twice through discountCents.
• Dashboard order history used an N+1 query pattern, causing query count to grow with the number of orders.
• Past orders had no Duplicate Order flow for safely re-adding currently available products to the cart.

Fixes implemented

• Corrected pricing so free shipping is represented only through shippingCents = 0 and is not credited again as a monetary discount.
• Replaced per-order item queries with a Prisma relation query, limited dashboard history to the most recent 30 days, and added a compound (userId, createdAt) index.
• Added POST /api/orders/[id]/duplicate with authentication, 404 for missing orders, 403 for wrong-owner requests, current product/stock checks, and the existing { data, error } response envelope.
• Added the dashboard Duplicate Order action and a batched Zustand cart update that merges eligible items into the current persisted cart.

Remaining bugs / incomplete features

• No known blockers remain for the three requested challenge tasks.
• Duplicate Order currently re-adds an order line only when the full original quantity is available. Stock is validated again during checkout because inventory can change while items remain in the cart.
• Repository-wide npm run lint still reports 7 pre-existing errors and 4 warnings in unrelated UI/hydration/link code. These were present outside the challenge changes; changed-file lint passes and the production build succeeds.

Run locally

npm ci
cp .env.example .env
npm run dev

Then open http://localhost:3000.

Verification

• npm test — 9/9 tests passed
• npx tsc --noEmit — passed
• focused ESLint checks on changed source/test files — passed
• npx prisma validate — passed
• npm run build — passed
• git diff --check — passed

AI usage is documented in AI_LOG.md.

Screenshots/demo video were not included because they are optional in the challenge brief.