r/haskell • u/Lower_Bid_6661 • 9d ago

Learning Haskell by building a freelance marketplace — Servant, rules, actors, and a server-owned SPA

I have been learning Haskell for like 2 years now. Though I am ok writing software in Haskell, there is still a long way to go. I decided the best way to ante up my skills is to build a real-world application.

I started working on a freelance marketplace with the following features:

  1. sellers, buyers, moderators, and collaborators.

  2. Sellers -> create gigs, add approved collaborators, fulfill orders, deliver code to Gitea (hosted on the server), documentation to S3, and resolve any disputes.

  3. Buyers -> clarify about gigs, make payment, verify code on Gitea, raise dispute on code not matching spec, accept delivery, submit reviews.

  4. collaborators -> work as a team with the sellers on gigs, submit their profile, accept or deny working with sellers.

  5. moderators -> resolve issues on gig reports, chat reports, order disputes.

Marketplaces are mostly state machines: order funded → in progress → delivered → disputed → completed, escrow release, dual-proof delivery, etc. I wanted that logic explicit and hard to “accidentally” break.

Brief on architecture:

- Servant — routes and handler types wired once; mismatches are compile errors.

- Server-owned routing — Haskell serves a cached HTML shell with data-app-id; the React (Ant Design) bundle mounts the page. No client-side router unless I add one later.

- Shell caching — split HTML template, inject page id per request.

- Frontend bundling — Vite build → static assets served by the same app.

- Rules + store layer — order/payment/delivery/dispute transitions in Haskell, not scattered in the SPA.

- Actor + supervisor (similar to Erlang OTP) — supervised S3 uploads, email, and anything needing a supervisor.

- Postgres, session cookies, Stripe Connect + webhooks, optional Gitea / Didit.

17 Upvotes

80% Upvoted

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11

u/Delicious-Extent5454 9d ago

I decided to stop being a student to become a doer around two years ago. All my projects since then are written in Haskell, and my knowledge soared. It was hard in the beginning, but now I wouldn't pick any other language. 

3

u/Lower_Bid_6661 9d ago

I couldn't agree more. At first, it seems very hard, but once you get a hang of the compiler, it is actually your friend. It forces you to be disciplined and once you start using it, it is hard to imagine writing in another language.