atrium

A small chat server in the spirit of IRC: pick a nick, hop between channels in the sidebar, talk. Built with Phoenix LiveView and backed by SQLite, so there is no database server to run.

• Elixir 1.17+ and Erlang/OTP 26+

mix setup          # fetch deps, create the SQLite db, run migrations + seeds, build assets
mix phx.server     # http://localhost:4000

mix setup seeds three channels to start with: #general, #random, #dev. The database lives in atrium_dev.db (gitignored); delete it to start fresh, or run mix ecto.reset.

Pick a nick on the splash prompt, then type in the composer at the bottom.

Anything starting with / is a command:

New lines appear live for everyone in the channel. Opening a channel loads its last 100 messages, and the on-screen log is capped at 100 lines as you chat. Messages are limited to 2000 characters, nicks to 24 characters (letters, numbers and a few IRC-safe symbols); channel names are lowercase, up to 32 characters.

• Atrium.Chat — the context. Channels and messages are Ecto schemas in SQLite. post_message/4 inserts a row and broadcasts it on a per-channel Phoenix.PubSub topic; a separate topic announces new channels so every client's sidebar stays current.
• AtriumWeb.ChatLive — the entire UI is one LiveView at /. It subscribes to the current channel, renders messages as a LiveView stream, and parses the slash commands.
• Concurrency — the SQLite connection uses WAL journal mode so reads never block the writer, plus a 5s busy_timeout so simultaneous writers wait for the lock instead of failing. Many people can talk at once without losing messages.

mix test           # unit + LiveView tests, including a concurrent-write test
mix precommit      # compile --warnings-as-errors, unused-deps check, format, test

Set DATABASE_PATH (where the SQLite file should live) and SECRET_KEY_BASE, then follow the standard Phoenix deployment guides. Point DATABASE_PATH at a persistent volume so history survives restarts.

Set both JEV_API_KEY and CHAT_RULES to moderate every message with TypeSafe's Jev API before it's stored. CHAT_RULES is a plain-text description of what's not allowed, e.g.:

JEV_API_KEY=sk-...
CHAT_RULES="No spam or advertising. No harassment or hate speech."

Messages judged to break the rules are rejected with a flash error instead of being posted. Leave either variable unset to disable moderation entirely; a failed or unreachable moderation call also fails open so the chat keeps working. See Atrium.Chat.Moderation.