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Project ideas from Hacker News discussions.

Show HN: CLI to order groceries via reverse-engineered REWE API (Haskell)

Original Article

Hacker News Discussion

📝 Discussion Summary (Click to expand)

3 Prevalent Themes| Theme | Supporting Quote |

|-------|------------------| | Haskell‑centric development & formal verification | "Love Haskell. It's the language of 2026. Having an agent available if you get stuck with some weird type error is a blessing. It also helps with the tooling. Though the modern tooling with cabal is pretty good." — wazHFsRy | | Mixed feelings about API openness & price transparency | "B2C: Is it really surprising that a business has no interest in providing more price transparency to their customers?" — rmoriz | | AI‑driven grocery automation & recipe integration | "Could even ask it to find recipes and then have it buy the ingredients needed for them next time it's doing your shopping!" — aprilnya |

These themes capture the community’s focus on the Haskell implementation, the debate over open supermarket APIs, and the aspiration to let AI handle end‑to‑end grocery ordering.

🚀 Project Ideas

[Grocery PriceOptimizer]

Summary

  • One‑stop comparator that shows unit prices & discounts across REWE, Billa, etc.
  • Auto‑generated “cheapest basket” suggestions with sortable price columns.

Details

Key Value
Target Audience Budget‑aware shoppers, deal hunters, families
Core Feature Cross‑market price comparison & cheapest basket builder
Tech Stack Python 3.11, FastAPI, PostgreSQL, React + TypeScript, Docker
Difficulty Medium
Monetization Revenue-ready: Freemium (free basic, $4.99 /mo premium)

Notes- Users repeatedly asked for unit‑price sorting (e.g., “I’d settle for just being able to sort items by unit price”). - Integrates easily with existing supermarket APIs; adds value without violating terms.

  • Could be packaged as a SaaS widget for recipe sites or a browser extension.

[AI Grocery Reorder Agent]

Summary- LLM‑driven CLI that reads a recipes file and automatically fills a grocery basket.

  • Supports “re‑order” scripts and seasonal‑ingredient filtering for weekly meal planning.

Details

Key Value
Target Audience Busy home cooks, recipe enthusiasts, meal‑plan creators
Core Feature AI‑generated grocery list that auto‑adds items to REWE/Billa carts
Tech Stack Node.js CLI, OpenAI / Claude API, SQLite for preference storage
Difficulty Low
Monetization Revenue-ready: Subscription $2.99 /mo

Notes

  • Commenters suggested re‑order scripts and integration with recipe YAML files.
  • Works as a lightweight wrapper around existing supermarket APIs, adding convenience without extra UI work.
  • Potential upsell: premium “seasonal filter” or “shopping‑history analytics”.

[Verified Grocery Automation Engine]

Summary

  • Open‑source library that formal‑verifies grocery‑automation code using Lean 4 specifications and generates test suites for Haskell implementations.
  • Guarantees correctness of suggestion engines and price‑comparison logic.

Details

Key Value
Target Audience Developers building reliable grocery automation tools, functional‑programming fans
Core Feature Formal verification of suggestion algorithms & API client behavior
Tech Stack Haskell, Lean 4, Stack/Cabal, CI pipelines (GitHub Actions)
Difficulty High
Monetization Hobby

Notes

  • Inspired by a user’s mention of formal verification in Lean to assure correctness.
  • Addresses concerns about fragile scraping/clients breaking, offering confidence to maintain bots.
  • Could be offered as a consulting service or paid “verification-as‑a‑service” for startups.

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