watchparty/README.md
Nicolas 5d535d18d8
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Switch to Socket.IO; fix two real memory leaks
Requested: Socket.IO instead of raw WebSockets, and explicit attention
to memory leaks. Auditing for the second turned up two real, concrete
leaks, independent of the transport library:

1. Server-side: a raw `ws` server has no idea a client is gone unless
   it gets a proper close frame - a sleeping laptop, a network drop, a
   killed tab never fire 'close', so the PartyMember's socket
   reference (and everything it closes over) sat in memory forever,
   and the party was never cleaned up by anything else either
   (removeIdleParties only looks at lastActivityUtc). Socket.IO's
   built-in heartbeat (pingInterval/pingTimeout) detects and closes
   these out on its own - a real, not just cosmetic, reason to prefer
   it here.

2. Client-side: router.js only ever did currentRoot.innerHTML = ''
   between routes, destroying DOM but never telling the outgoing
   view's JS to stop. Leaving the player any way other than its own
   "Quitter" button (a sidebar link, browser back) left the 3s
   heartbeat setInterval, the realtime connection, and the hls.js
   instance all running against a detached <video> indefinitely, for
   as long as the tab stayed open.

Fixes:
- server/src/socketHandler.js replaces wsHandler.js: same protocol
  (see its own top comment), over Socket.IO. Rooms (socket.join/
  io.to) replace manually iterating party.members to broadcast.
  Error event renamed to "errorMessage" - Socket.IO reserves "error".
- server/src/index.js: socket.io server instead of a raw
  WebSocketServer, same-origin (no CORS config needed).
- client/js/party.js: socket.io-client (window.io, loaded via
  <script> in index.html) instead of hand-rolled WebSocket + JSON
  framing - also gets automatic reconnection for free.
- router.js: route() handlers may now return a cleanup function;
  render() calls whatever the previous view returned before switching
  to the next route, regardless of how navigation happened.
- player.js returns a cleanup that clears the heartbeat, destroys
  hls, disconnects the socket, and removes its document-level click
  listener (now named, not inline-anonymous, specifically so it CAN
  be removed - an anonymous one added fresh per visit would itself
  have been a slow leak even with everything else fixed). The
  "Quitter" button is now just navigate('/home') - cleanup runs the
  same way regardless of how you leave.

Verified for real (see session history): a real Socket.IO client
connected to a really-running local server end to end. Then, with
document.addEventListener/removeEventListener and setInterval/
clearInterval instrumented, drove the router through repeated "join a
party, then navigate away without clicking Quitter" cycles - adds and
removes matched exactly every time (3/3 listeners over three cycles,
2/2 intervals over two), nothing left pending.

docs/architecture.md has the full writeup under "Realtime transport:
Socket.IO, and two real memory leaks".

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-13 23:07:51 +02:00

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Markdown

# Watch Party for Emby
A standalone web app for watching the same title, in sync, with other users
of the same Emby server. It reads your Emby catalog and streams your Emby
media, but it's its own app with its own player — not an Emby plugin.
See [docs/architecture.md](docs/architecture.md) for the full design,
including why this replaced an earlier Emby-plugin attempt (still in
[src/WatchParty/](src/WatchParty/) for reference — see below).
## How it works
1. Sign in with your Emby account (just username/password — the server
address is fixed server-side, see Deploying below).
2. A sidebar lists your Emby libraries; the home page shows every ongoing
watch party plus a "recently added" row per library, Emby-style.
3. Pick a movie/episode tile and hit "Lancer une watch party" (or drill into
a Series' seasons/episodes first) — you become the host — or join one
with a 6-character code.
4. The host's play/pause/seek drives everyone else's player automatically;
starting from an episode queues the rest of the series so the host can
just hit "Épisode suivant" instead of restarting a party each time.
Everything — catalog, images, video, sync — flows through this app's own
backend, which proxies whatever it needs from Emby server-side. The browser
never talks to Emby directly and never holds an Emby access token; it only
ever has a session cookie for this app.
Music isn't part of this yet — it needs its own player and a collaborative
playlist, different enough to be its own pass. The sidebar already lists a
Music library if you have one; the page just says so for now.
## Status
Login, and the rendering/navigation logic for the sidebar/home/library/series
pages, have been exercised end to end (login against the real Emby server
with intentionally-wrong credentials; the pages against mocked API
responses). See [docs/architecture.md](docs/architecture.md#assumptions-to-verify)
for exactly what that does and doesn't confirm — the real Emby response
shapes this now depends on (library `CollectionType`, seasons/episodes,
`PlaybackInfo`'s media streams) and actual HLS playback are still unverified.
## Project layout
```
server/ Node.js backend: proxies ALL Emby access (auth, catalog,
images, HLS streaming) and coordinates party/room state +
realtime sync. The browser only ever talks to this.
src/index.js Express app + REST endpoints
src/embyAuth.js server-side login against Emby + session cookies
src/embyProxy.js generic Emby request/response proxying (incl. HLS)
src/socketHandler.js Socket.IO protocol (see comments in the file)
src/partyManager.js in-memory room state
client/ Static frontend (plain JS, ES modules, no build step).
Talks only to server/ - never to Emby directly.
js/shell.js persistent sidebar + #mainContent the router swaps
js/tiles.js poster-tile rendering shared by home.js and library.js
js/embyApi.js calls our own /api/* routes (auth, catalog, playback options)
js/party.js our own backend's party REST + Socket.IO client
js/views/ one file per screen: login, home, library, series, player
src/WatchParty/ The earlier Emby-plugin attempt. Builds fine and installs,
but Emby has no supported extension point for a player
button, and even menu integration required reverse-
engineering undocumented internals - see
docs/architecture.md for the full story. Kept for
reference; not the active direction.
docs/architecture.md full design doc for the standalone app
```
## Running locally
```bash
cd server
npm install
EMBY_SERVER_URL=https://your-emby-server npm start
```
Then open `http://localhost:3000`.
## Deploying
Build the Docker image from the **repo root** (it needs both `server/` and
`client/`):
```bash
docker build -f server/Dockerfile -t watchparty .
docker run -d --name watchparty -p 3000:3000 -e EMBY_SERVER_URL=https://theater.media.kyuno.fr watchparty
```
Then put it behind your existing reverse proxy like everything else
(`theater.media.kyuno.fr`, `git.dev.kyuno.fr`, ...), e.g.
`watchparty.kyuno.fr` → `http://<container>:3000`.
## Roadmap
- [x] Design + scaffold the standalone app
- [x] Proxy all Emby access server-side; Emby-themed UI (sidebar, carousels)
- [x] TV show navigation (Series → Seasons → Episodes) + episode auto-queue
- [x] Player language/subtitle/quality pickers
- [x] Socket.IO instead of raw WebSockets; fixed two real memory leaks
(dead-connection cleanup server-side, view teardown on navigation
client-side) — see docs/architecture.md
- [ ] Try a full party end-to-end with two real accounts (still the main gap)
- [ ] Music: dedicated player, artist/album browsing, collaborative playlist
- [ ] Tune transcoding target / support direct play when possible
No chat, no OIDC — deliberately out of scope (Emby-only auth was the
explicit choice; see docs/architecture.md).
## License
MIT — see [LICENSE](LICENSE).