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

Name: CLI to order groceries via reverse-engineered REWE API (Haskell)
Availability: InStock
Author: wazHFsRy

by wazHFsRy·Mar 30, 2026·205 points·85 comments

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AI Analysis

●●SolidNiche GemBig Brain

Reverse-engineered mTLS grocery API with full checkout workflow in Haskell.

Strengths

•mTLS certificate extraction and API reverse-engineering is genuinely clever technical work
•Agent-first JSON output design suits automation workflows
•Full order lifecycle coverage from search through cancellation

Weaknesses

•Only works for one German supermarket chain with extremely limited applicability
•Requires manual certificate extraction and breaks if REWE changes their API

Post Description

I just had the best time learning about the REWE (German supermarket chain) API, how they use mTLS and what the workflows are. Also `mitmproxy2swagger`[1] is a great tool to create OpenAPI spec automatically.

And then 2026 feels like the perfect time writing Haskell. The code is handwritten, but whenever I got stuck with the build system or was just not getting the types right, I could fall back to ask AI to unblock me. It was never that smooth before.

Finally the best side projects are the ones you actually use and this one will be used for all my future grocery shopping.

[1]https://github.com/alufers/mitmproxy2swagger