# CLAUDE.md

Guidance for Claude Code when working in this repository.

## What this is

NovaSonic — a self-hosted music streaming **PWA** (Vite + vanilla ES modules) and
**Android app** (Jetpack Compose + Media3/ExoPlayer) for Navidrome / Subsonic servers,
plus a **Node.js/Express backend** that downloads tracks via yt-dlp and proxies APIs.

## Critical rules

- **Never hardcode or mock frontend data.** All library data comes from the Navidrome
  (Subsonic) API. No placeholder songs/albums/artists, ever.
- **Don't commit or push unless asked.** When asked, push to the Gitea remote.
- **Two-part versioning** `MAJOR.MINOR` (e.g. `0.8`) — no patch component. Each release
  bumps the minor; features and fixes go in the same release. See `CHANGELOG.md`.
- Keep the `CHANGELOG.md` Platform Parity Matrix accurate when adding cross-platform features.

## Layout

- `src/` — web PWA (vanilla ES modules). State in `src/state.js` (the `S` object);
  Subsonic/iTunes API in `src/api.js`; views in `src/views/`, UI in `src/ui/`.
- `backend/novasonic-server.js` — Express API (downloads, metadata edit/delete, events/ABS proxy).
- `backend/lib/` — `ytdlp.js` (download + cascade + ffmpeg tagging), `downloader.js`,
  `metadata.js` (iTunes lookup, file resolution helpers), `config.js`, `jobs.js`, `romaji.js`.
- `android/` — native Kotlin app (separate; backend-dependent web features like the
  metadata editor are **not** in the Android app).

## Commands

```bash
npm run dev      # Vite dev server (HMR)
npm run build    # production build → dist/
npm run preview  # preview the production build
```

Backend runs in Docker (see `docker-compose.yml`); on the deploy host it lives at
`/opt/navidrome/music`. Restart after backend changes: `docker compose restart novasonic-backend`
(this also re-pulls the latest yt-dlp).

## Download pipeline (hard-won knowledge)

- Downloads are **yt-dlp only** (the old squid.wtf/Qobuz backend was removed).
- **File naming:** `{NN - }Artist - Title.ext` with the release suffix stripped from the
  title (no `- Single`/`- EP`). The **album folder keeps the full album name**. Original names
  are used for folder, filename, and all main tags (artist/title/album/album\_artist) — even
  for Japanese tracks. Romaji goes **only** into sort tags (TITLESORT / ARTISTSORT / etc.).
- **Search cascade** (`ytdlp.js`): YTM search first (`web_music` player client, Songs filter
  param), then regular YouTube; each candidate filtered by duration (±10%, min 10s),
  title keyword, artist channel, and variant exclusions (remix/cover/sped/…).
- **"Mittelweg" rule** (with AND without duration): when nothing matches in the filtered steps,
  relax only the duration constraint while **still requiring the artist channel**. If nothing
  matches, download **nothing** and fail cleanly with "Nicht eindeutig gefunden — bitte
  Direktlink im Importer nutzen". Never fall back to a blind title-only/no-filter grab — it
  pulled same-titled covers by other uploaders, and wrong Piano Echoes for Japanese tracks.
- **Size cap:** `--max-filesize 30M` on every yt-dlp call; Mittelweg steps also cap at 2×
  expected duration. Prevents saving a 28-min video (52 MB) when the wrong result slips through.
- **Duplicate detection** (`metadata.js findExistingTrack`): searches case-insensitively across
  all album folders under the matching artist folder; compares normalized artist+title ignoring
  track prefix and release/variant suffix. Handles DJ OKAWARI vs DJ Okawari and "- Single" drift.
- **Known limitation:** yt-dlp's YTM/YouTube *search* can't surface very obscure Art Tracks by
  ambiguously-named artists (e.g. "MINA") — the browser finds them, yt-dlp's API extraction
  doesn't (confirmed across params/clients/deno). For those, the **direct link in the importer**
  (`sourceUrl` path) is the reliable route.
- **File resolution for edit/delete:** Navidrome's stored path may use a different mount root
  or a stale stem. `metadata.js` rebases the path and falls back to recursive/stem matching
  (tolerant of release-suffix mismatch). A ghost Navidrome entry needs a full library rescan.
- **Album splitting:** prevented by consistent `album_artist` tag. All tracks in a download
  share the same `mainArtist` value (= iTunes `collectionArtistName` when available, else
  `albumArtist` param, else track artist). Never use `rawArtist` for `album_artist`.

## UI / references

When referencing files in chat, use clickable markdown links, not backticks:
`[ytdlp.js](backend/lib/ytdlp.js)`.