# ytplayer — project facts for agents

## What this is
Ad-free YouTube player. Three shells share `frontend/`: **web PWA** (Bun + Hono in
`server/`, the production deployment), Tauri (Windows), zero-native (Linux/macOS).
The PWA is what runs in production; `legacy/` holds the old native-only docs.

## Repo map

| Path | What lives there |
|------|------------------|
| `frontend/app.js` | The entire UI (~3.6k lines, no framework): player, playlists, search, settings, sync |
| `frontend/sw.js` + `frontend/sw-update.js` | Service worker + update flow (FRAGILE — see below) |
| `frontend/opfs.js` / `opfs-worker.js` | OPFS offline audio cache |
| `frontend/fingerprint.js` | Browser fingerprint used as the sync key |
| `frontend/async-guard.js` | Stale-async-response guard (unit-tested) |
| `server/server.js` | Bun + Hono backend — endpoint list is in its header comment |
| `server/db.js` | libsql schema/queries (`users`, `profiles`, `video_history`, `media_cache`…) |
| `server/media-cache.js` | Server-side video cache: background fetch jobs, validation gate, x264 lane, LRU |
| `bin/yt-dlp` | Downloaded by `npm run setup`, gitignored |
| `scripts/` | icon generation, yt-dlp setup, push helper |
| `tests/` | Playwright e2e specs · unit tests live next to sources in `frontend/*.test.js` |
| `legacy/` | Old native-shell docs — do not treat as current |

API endpoints: `GET /api/search|channel|streams|download/:id|version|user/data|profile/load`,
`GET /api/media/:id|media/:id/status|media/stats`, `POST /api/media/:id/redownload`,
`POST /api/user/sync|profile/create|profile/save`, `GET /sw.js` (BUILD_TAG-injected), `GET /*` static.
JSON shapes mirror the Tauri Rust bridge exactly — don't change one side alone
(`/api/streams`' `data.serverCached` is additive and web-only).

## Server media cache (`server/media-cache.js`)
- Every played (`/api/streams`, LOW priority, ≤ `MEDIA_AUTO_MAX_SECONDS`) or saved
  (`/api/download`, HIGH, ≤ 3 h) video gets ONE copy: `$MEDIA_DIR/<id>.<gen>.mp4`
  (≤720p H.264 8-bit + AAC, faststart) + `<id>.<gen>.m4a` audio sidecar for audio-only
  mode. `MEDIA_DIR` defaults to `./data/media` (the `ytplayer-data` volume in prod).
- Jobs are server-owned — **never pass a request AbortSignal into them**; a client
  closing its tab must not kill a fetch. Downloads still run inside `withSaveSlot`.
- **Validation gate** (`validateMedia`): h264 yuv420p + AAC, container/stream durations
  cover the source, a full `-c copy` demux pass with zero stderr, head + tail decode.
  The demux pass is what catches a faststart file whose index is intact but whose
  data is cut. Nothing reaches the cache dir without passing it; failures back off
  (15 min · 2^n, max 24 h) and saves fall back to the legacy per-request path.
- `gen` is in the filename and URL (`/api/media/<id>?g=<gen>`): a URL never serves
  different bytes. A replaced gen is kept 30 min so in-flight Range playback survives.
- **Compression lane**: niced x264 `-preset slow -crf 28 -fpsmax 30`, audio copied,
  kept only if ≥15% smaller. Measured: YouTube's 720p avc1 is already ~0.6–0.7 Mbps, so
  CRF 24 made files *bigger*; CRF 28 ≈ −20% video at SSIM 0.994. Lyric videos usually
  keep the original. HEVC/AV1/10-bit are smaller but don't play in iOS `<video>`.
- **Budget**: `MEDIA_CACHE_MAX_BYTES` (10 GiB) LRU by `last_access` (anything played in
  the last 10 min is protected) + `MEDIA_MIN_FREE_BYTES` (5 GiB) disk guard → skip, stream.
- **Broken**: `POST /api/media/:id/redownload` (now-playing ⚠ Broken button). When a
  client falls back from a cached copy (`/api/streams?nocache=1`) the server also
  re-validates its copy and refetches it if it fails — never trusts one device's error.
- Ops: `curl https://worship.hesed.sbs/api/media/stats`; files under
  `/app/data/media` in the container.

## Local dev

```bash
npm run setup            # download bin/yt-dlp (once)
cd server && bun install
ln -s ../frontend public # once — the server serves ONLY ./public (Docker copies frontend/ there)
bun --hot server.js      # http://localhost:3000
node --test frontend/    # unit tests (run from repo root)
npx playwright test      # e2e (see Testing below)
```

Local DB file: `server/data/ytplayer.db` (gitignored). `BUILD_TAG` is computed from `./public` contents.

## Production deployment (web PWA)
- URL: **https://worship.hesed.sbs** (Traefik label in `docker-compose.yml`)
- Runs on the **homelab** Dokploy remote node; control plane is Dokploy on the VPS
  (`193.160.119.172`, API key in `~/development/.secrets/dokploy-api.env`).
- Compose ID: **`wprYCM8T51f7JtSHb983p`** (project `ytplayer`, env `production`).
- **Pushing to git does NOT deploy.** Trigger explicitly (build ≈ 5–6 min):
  ```bash
  ssh -i ~/.ssh/tmp_vps/dokploy_session root@193.160.119.172 \
    "curl -s -X POST -H 'x-api-key: $KEY' -H 'Content-Type: application/json' \
     -d '{\"composeId\":\"wprYCM8T51f7JtSHb983p\"}' http://localhost:3000/api/compose.deploy"
  # poll composeStatus via /api/compose.one?composeId=... until done|error
  ```
- Confirm the deploy landed: `curl https://worship.hesed.sbs/api/version` — the
  `buildTag` (content hash of every file under `./public`) must change.
- Homelab node is NOT always reachable on LAN; SSH via the VPS hop:
  `ssh root@193.160.119.172` → `ssh root@10.8.0.2` (WireGuard). Container name:
  `ytplayer-main-1dihzn-ytplayer-1`. DB: libsql file `/app/data/ytplayer.db`
  (query with `docker exec <c> bun -e '...' `using `@libsql/client`).

## Update-flow architecture (fragile — read before touching)
- `GET /sw.js` is served by the server with the real `BUILD_TAG` **injected by
  regex** over the fallback expression in `frontend/sw.js`. Never switch back to
  an exact-string replace: when the fallback literal was bumped (`v1.0.3`→`v1.0.4`)
  the exact match silently failed, the SW version froze, and **no client ever
  received another update** while `/api/version` kept announcing one — the
  "Update available keeps showing" bug.
- `BUILD_TAG` hashes **every** file under `./public` recursively. Don't reduce it
  to a file subset; a change to an unlisted shell file would stop busting caches.
- The update banner only shows when a waiting SW exists **and the page already
  has a controller** — a first install (fresh visit, or after Settings → Force
  refresh unregisters) passes through `waiting` transiently and must not banner.
- "Refresh UI" (`frontend/sw-update.js`): if no worker is waiting yet (banner came
  from the `/api/version` poll), it calls `reg.update()`, waits for `installed`,
  posts SKIP_WAITING, waits for `controllerchange`, then reloads once.

## Cache layout & offline thumbnails
- Three cache families, and the split matters on activate: the **versioned shell
  cache** `ytplayer-<BUILD_TAG>` is evicted on every deploy, while the **utility
  caches** `ytplayer-thumbs` and `ytplayer-fonts` are listed in `UTILITY_CACHES`
  and deliberately survive it. Adding a new utility cache means adding it there
  too, or it gets wiped on the next deploy.
- **Thumbnails are cache-first, not stale-while-revalidate** — a given thumbnail
  URL is immutable, so revalidating just burns a round trip per image per launch.
- **The opaque-response trap (this silently emptied the thumb cache for months).**
  An `<img>` to another origin is a **no-cors** request, so `fetch(request)` in the
  SW resolves to an **opaque** response with `status === 0` — not 200. The old
  guard was `if (r.status === 200) cache.put(...)`, which rejected every single
  thumbnail, so `ytplayer-thumbs` was permanently empty and offline showed broken
  images (measured on prod: 0 entries after browsing pages full of visible thumbs).
  Fix in `thumbnail()`: re-issue the request in `cors` mode — ytimg/ggpht all send
  `Access-Control-Allow-Origin: *` — and cache that readable response; an opaque
  one is accepted only as a last resort. **Never reintroduce a bare `status === 200`
  check on a cross-origin subresource.**
- Thumbnail hosts live in `THUMB_HOSTS`. An unlisted host doesn't error — it just
  bypasses the cache and breaks offline, so add mirrors/avatar hosts there.
- The thumb cache is capped at `THUMB_CACHE_MAX` (800, oldest-first via the
  insertion-ordered `cache.keys()`). Keep a cap: CacheStorage and the OPFS offline
  audio share one origin quota, and opaque entries are padded to ~7 MB each for
  quota accounting, so an unbounded thumb cache can evict saved audio.
- App side (`app.js`): `warmThumb()` pulls artwork through the SW when a video is
  saved offline, and `warmOfflineThumbs()` runs a bounded launch backfill
  (`THUMB_WARM_MAX` = 400, 4 at a time) over cached ids + playlist videos so
  libraries saved before this fix repair themselves. Thumbnails only cache when
  something requests them — a device needs one online launch to get offline art.
- `staleWhileRevalidate()` (fonts) must not `return cached || networkFetch` bare:
  the fetch resolves to `null` offline and `respondWith(null)` throws. It ends
  with `|| Response.error()`.

## Data model quirks
- Client state persists in localStorage key **`_ytpdata`** and syncs (debounced
  400 ms) to `POST /api/user/sync`, keyed by a browser fingerprint.
- **A-B loop markers are per-song-per-playlist**: stored on the playlist's own
  copy of the video (`entry.ab = {a, b}`) when playback source is that playlist;
  `data.abMarkers[videoId]` is only the fallback for non-playlist playback.
- **Online profiles** (`profiles` table, `/api/profile/*`): named cross-device
  sync where the lowercase profile NAME is the only credential (passkey-style,
  by design). Client stores `data.profile = {name, syncedAt}`; sync is
  last-write-wins — push debounced on every persist(), pull on app launch when
  the server's `updated_at` is newer than the local `syncedAt`.
- **Profile share links**: `?profile=<name>` is consumed by `adoptProfileFromUrl()`
  at boot, before any rendering. It strips the param via `replaceState` (so a
  reload can't re-fire it) and confirms first when the device already has
  playlists/history or another profile — adopting *replaces* the synced slice.
  The name comes off the URL untrusted, hence `escapeHtml()` on it.
- **Empty-home playlist grid**: `renderHomePlaylists()` swaps the branding hero in
  `#playerPlaceholder` for the user's playlists (hero is the no-playlists
  fallback). It is driven from the tail of `renderSidebar()` — not from
  `render()` — so every playlist mutation refreshes both in one place.

## Testing
- Unit: **`node --test frontend/*.test.js`** (sw, sw-update, async-guard, video-edit).
  Server: **`cd server && bun test`** (media-cache: real ffmpeg fixtures + a temp libsql DB).
  Local e2e needs a CURRENT yt-dlp — a 2-month-old one 403s on every download.
  The directory form `node --test frontend/` fails on Node 22 with
  `Cannot find module .../frontend` — it resolves the dir as a module, not a test
  glob. That's the harness, not the tests.
- E2E: `npx playwright test` — WebKit iPhone-12 profile against a static serve of
  `frontend/` (needs `npx playwright install webkit`). A spurious update banner
  will make the settings-panel specs fail with `#modal intercepts pointer events`
  — that failure mode is a real app bug, not test flake. On the WSL laptop the
  WebKit install fails host validation (missing `libgtk-4`, `libgstreamer*`, …,
  needs `sudo npx playwright install-deps`); chromium is already downloaded, so
  ad-hoc rendering/offline checks can drive it directly instead.
- Service-worker behaviour (thumb caching, offline) is only provable in a real
  browser: serve `frontend/` statically, let the SW take control (needs a second
  reload), then `context.setOffline(true)` and assert `img.naturalWidth > 0` plus
  the `ytplayer-thumbs` entry count. Asserting against the browser's own HTTP
  cache proves nothing — check the Cache API entry count.
- Test records on prod use `Probe */Recon *` names; clean via the container DB,
  children (`video_history`) first.

## Harness

Skills live in `.agents/skills/` (symlinked into `.claude/skills/`):
- **deploy-prod** — the Dokploy deploy + buildTag verification flow (manual-only; use for any "deploy"/"release" request).
- **mobile-app-ui-design** — UI/UX design work on the PWA screens.

## Commit rules
One changeset = one commit, single-line imperative message, **no AI attribution
of any kind** (global rule). `git push origin main` pushes to both remotes.