About

C7: the tutorial swap board

MyTimetable’s swap request is blind: you ask to move into a full class and wait, with no view of who else wants yours and no way to talk to them. C7 is a small parallel system for one course’s COMP4020 crit-group sessions: a student posts the class they’re leaving and the classes they’d join, another student who’s happy to swap says so, and the poster accepts or declines. It makes swapping visible, discussable and agreed by both students — it cannot change a real ANU allocation, and nothing here is official.

All of it is built and deployed: the login and eight demo students, the board of swap posts, editing and withdrawing a post, offers with accept and decline, comments, private messages, live updates and the transit-board look. The site calls itself “Swap Board”, and its classes are crit-group sessions, not tutorials.

What good looks like here

A simple, real login, not automatic matching. Private messages between students aren’t private without real accounts, so C7 uses a plain username and password (not ANU single sign-on) rather than skip identity altogether. Signing up is open to anyone: a tutor at the crit can be themselves, or use a seeded demo student. Because C7 does no automatic matching — no pairing, no cycles, no “fits your post” hint — a student finds a swap by reading the board and agrees it with an offer the poster accepts. That keeps the whole system legible: every match on the board was two people choosing each other, not an algorithm’s guess.

Everything except this README, the login and the sign-up form is behind the login. A logged-out visitor gets the login page at /, so the board’s own content is never visible without an account; every other page redirects to /login/ and returns them where they were headed once they’re in. A login lasts 30 days on that browser, stored as a row in the database so it survives a redeploy, with a visible “Log out” on every logged-in page.

Demo login, not ANU single sign-on. Don’t use your ANU password. Anyone can sign up or use a demo student, so treat what you post as visible to strangers. Demo students are shared, so their messages aren’t private. Private messages can be read only by the two students in the conversation, which for a demo student means anyone. They are stored unencrypted, and whoever runs the site can read them. There is no rate limiting, password reset or account deletion.

Eight demo students, one shared password. The login page has a one-click button for each of Alex, Priya, Sam, Lena, Jordan, Mei, Noah and Zara, plus “Random demo student”. They share the password demo-student, published here, for anyone who would rather type it in the ordinary form. Their names are taken: signing up as one fails like any other duplicate. The demo students are written once, when the database has none; a server restart never rewrites them.

Resetting the demo is the operator’s job, and the app has no button for it. pnpm seed:reset locally, or fly ssh console -C "node dist/seed-reset.mjs" on Fly, deletes every swap post, offer, comment and private message that involves a demo student, including a real student’s post swapped through a demo student’s accepted offer, then writes the demo seed again, all in one transaction. Real students keep their accounts and everything that involves only real students.

Real names and uni IDs are allowed, since the demo-login notice above already tells a student who can read what they post.

The board is home. / lists every open swap post, newest first. On a wide screen a side column holds the student’s own post under “Your swap” (or a “Post a swap” button when they have none) and, once they have made an offer, “Your offers”; beside it sit the open posts. On a phone the columns stack in that order. Each entry reads GIVING (the class being left) → LOOKING FOR (the classes that would do), with the message cut short and the counts of pending offers and comments. A post names the class the student is leaving, one or more classes they would join (never the one they are leaving) and an optional message of up to 500 characters. A student has at most one open post. Each post has its own page at /posts/<id>/ with the whole message, and it still loads after the post is withdrawn or swapped. Every time shown is Canberra time.

A post can be edited until someone offers, and withdrawn any time. The poster can change the classes and message while the post has no pending offers (a declined offer doesn’t lock it), and an edited post says so with the time. Withdrawing takes the post off the board, closes its pending offers and lets the student post again.

An offer is “I’m happy to swap”, made from the post’s page. Any other student can offer on an open post by naming the one join class they hold and would leave; an offer carries no message, since talking happens in comments and private messages. A student has at most one pending offer per post and can withdraw it until it is accepted; after a decline they can’t offer on that post again. Everyone sees how many offers a post has, but only the poster sees who offered. The poster accepts or declines each one. Declining is one click and the post stays open. Accepting is final, and a confirm step says so: the post becomes swapped and leaves the board, and the app closes the post’s other pending offers, every other pending offer made by either student, and the offerer’s own open post. The app then says who moves where and that the change must be made in MyTimetable, because this app can’t make it. An offerer sees each offer as Pending, Accepted, Declined, You withdrew or a closed reason.

Comments are one flat thread on the post’s page. Any logged-in student can add a plain-text comment of up to 500 characters. Comments can’t be edited; only their author can delete one, which leaves a “Comment deleted” marker. A withdrawn or swapped post’s comments are read-only.

Private messages are one conversation per pair of students. A “Message” link beside a username on a post page opens /messages/<username>/, where plain-text notes of up to 500 characters go back and forth, oldest first. They can’t be edited or deleted. The inbox at /messages/ lists the conversations, most recent first, and the header reads “Messages (N)” when N are unread. A message is unread until its recipient opens the conversation.

Open pages update live. The board, a post page and an open conversation refresh themselves when something changes, with no reload; the header’s “Messages (N)” and the inbox update on reload only. The pages still work without JavaScript, only correct on reload. The event stream at /api/events is public, so it carries only a post’s id and the kind of change, or just “a private message was sent”, never a comment, message, class or name; the page then refetches its content over its own login.

Coral means you have something to do. The one warm colour on the site marks what is waiting on you: pending offers on your own post, unread private messages and form errors. Everything else is neutral, and no status is told by colour alone.

Unofficial, and it says so. The design borrows a transit board’s wayfinding vocabulary (navy, cyan, GIVING → LOOKING FOR) and nothing that looks official: no crest, no ANU gold, no campus imagery. Every page carries the footer “Unofficial, student-built COMP4020 demo. Not an ANU system: it can’t change your real class allocation.”

The classes are real COMP4020 crit-group sessions. The six classes (Mon 14:00, Mon 15:30, Wed 09:00, Wed 10:30, Wed 14:00, Wed 15:30) come from the course’s public crit-groups data at https://comp.anu.edu.au/courses/comp4020-agentic-coding-studio/api/crit-groups.json, copied into the app on 2026-09-29 and never fetched while it runs. Credit: COMP4020 Agentic Coding Studio (ANU School of Computing), Ben Swift, from https://comp.anu.edu.au/courses/comp4020-agentic-coding-studio/, licensed CC BY-NC-SA 4.0. The data is provisional until enrolments settle, so it may be out of date.

What’s enforced, and what’s a judgement call

The rules above that are checkable are asserted against the built server: the username shape, the password length, case-insensitive uniqueness, the 30-day cookie, the redirect and next handling, the guarded pages and the demo-login notice’s presence in spec/auth.test.ts; the swap post rules in spec/posts.test.ts, spec/posts-edit.test.ts and spec/events.test.ts; offers, accepting and declining in spec/offers.test.ts and spec/accept.test.ts; comments, private messages and the inbox in spec/comments.test.ts, spec/private-messages.test.ts and spec/inbox.test.ts; the live board and post page in spec/live.test.ts; the demo seed and its reset in spec/demo-seed.test.ts and spec/seed-reset.test.ts. Browser tests in e2e/ check the same flows in Chrome at 1920×1080 and 390×844, including that the redesigned pages don’t scroll sideways.

Whether the pages actually read clearly and look like a board a student would trust, at a phone width and a desktop one, is a judgement call for the crit, not something a test can decide. The tests pin the layout’s structure (the split, the exchange row, the coral rule), not whether it is good.

Not built, on purpose

Automatic matching (pairs, cycles, or a “fits your post” hint) is out of scope for the whole of C7, not just this slice — a student always finds a swap by reading the board and agreeing it directly with another student. Also not built: an offer message, editing or deleting a private message, editing a comment, unread markers on comments, a block or report feature, and any way to change a real ANU allocation.