# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## What this is

LinTunes is an iTunes-replacement music library manager and player for Linux,
built with PyQt6 / Qt Multimedia. It imports an iTunes 12 library, stores the
library as plain JSON (syncable via Syncthing), and reproduces the iTunes UI
(left sidebar + right playlist view, column browser, customizable per-playlist
columns). `spec.md` is the original design brief; `TASKS.md` is the live backlog
and `tasks-done.md` records completed work.

## Commands

```sh
pip install -e .                 # install deps (PyQt6, mutagen, numpy, requests)
python3 -m lintunes.main         # run the app straight from the checkout
python3 -m pytest                # run the whole test suite
python3 -m pytest tests/test_round9.py            # one test file
python3 -m pytest tests/test_round9.py::test_name # one test
```

The app needs a `--data-dir`; config persists to `~/.config/lintunes/config.json`.
One-time iTunes import:

```sh
lintunes --import-xml "iTunes Library.xml" \
         --music-root "/path/to/iTunes Media" \
         --data-dir /path/to/library-data --save-config
```

Runtime needs FFmpeg codecs for Qt Multimedia (`qt6-qtmultimedia` w/ ffmpeg).
Tests run headless via the `qapp` fixture in `tests/conftest.py`
(`QT_QPA_PLATFORM=offscreen`).

## Architecture

**Data flows in one direction through three layers:** storage (JSON on disk) →
model (`Library`/`Track`/`Playlist` dataclasses) → `LibraryManager` (mutations +
persistence) → GUI (Qt widgets that read the manager and connect to its signals).

- **`lintunes/main.py`** — CLI entry. `--import-xml` runs a headless import and
  exits; otherwise `run_gui()` resolves Syncthing conflicts, loads the library,
  builds `Preferences`/`LibraryManager`/`LastFm`/`MainWindow`, wires MPRIS, and
  installs the window as a global event filter (for media keys).

- **`lintunes/models/`** — pure dataclasses (`track.py`, `playlist.py`,
  `library.py`) with `to_dict`/`from_dict` round-tripping. `PlaylistType` is
  `REGULAR | FOLDER | SMART | SYSTEM`. Per-playlist `PlaylistSettings` holds
  visible columns / sort column / widths. Playlists are identified by an 8-char
  hex `persistent_id` (folder containment via `parent_persistent_id`).

- **`lintunes/storage/json_storage.py`** — the library is **multiple files** in
  the data dir: `library.json` (all tracks), `library_metadata.json`, and one
  `playlists/<persistent_id>.json` per playlist. Writes are atomic (`*.json.tmp`
  → rename). **`storage/conflict_resolver.py`** merges Syncthing
  `*.sync-conflict-*` files on startup: play counts take the max, edited fields
  take the newest, playlist membership takes the union.

- **`lintunes/library_manager.py`** — `LibraryManager(QObject)` owns the
  `Library`, is the single funnel for all mutations, and persists them
  **debounced** (3 s) with per-area dirty tracking (a play-count bump rewrites
  only `library.json`; a playlist edit rewrites only that playlist file). User
  edits go through `undo_stack` (Ctrl+Z); the internal `_apply_*`/`_set_*`
  helpers do the real mutation + dirty-mark + signal and are reused by undo/redo
  without recursing. Widgets react to its signals (`playlists_changed`,
  `playlist_content_changed(pid)`, `track_updated(id)`, `track_fields_edited`).

- **`lintunes/player.py`** — `Player(QObject)` walks a queue through a swappable
  **`PlaybackSink`**. Player owns the queue, shuffle walk, per-track start/stop
  times and the play-count/scrobble bookkeeping; a sink owns only "make this file
  come out of something, and report where it's up to". `LocalSink` (the
  `QMediaPlayer`/`QAudioOutput` pipeline, with the `QAudioBufferOutput` PCM tee
  that feeds the visualizer) **stays in `player.py`** — the Player tests stub Qt
  Multimedia with `patch.multiple(player_module, QMediaPlayer=..., …)`, so those
  names must resolve in this module. `cast/sink.py::CastSink` is the other
  implementation. `set_sink()` carries the current track, position and
  playing-state across a swap and deliberately does *not* re-emit
  `track_changed` (that would double-scrobble the same song).
  Player is also deliberately **context-agnostic**: playback *context*
  ("library" / "playlist:<pid>") is tracked in `MainWindow`, not the player.

- **`lintunes/gui/`** — `main_window.py` assembles a top `TransportBar` over a
  horizontal `QSplitter` (`SidebarPanel` | stacked `LibraryView`/`PlaylistView`).
  `track_table.py` is the shared track grid (drag/drop, copy/paste, drop
  indicator). `playlist_ops.py::add_tracks_with_dup_check` is the single funnel
  for every add-to-playlist path. `theme.py` applies the palette (highlight
  colors, UI scales) from prefs.

- **`lintunes/importers/itunes_importer.py`** — parses the iTunes XML plist.
  Remaps Mac `file:///Volumes/...` paths to the local `--music-root` with
  case/Unicode-normalization fuzzy matching (macOS is case-insensitive + NFD vs
  ext4). Imports user playlists/folders only; smart and system playlists are
  currently skipped. Album art is read live from embedded ID3 tags
  (`tagging.py`), never stored in the library JSON.

- **`lintunes/preferences.py`** — app settings in `<data_dir>/preferences.json`
  (rides the same Syncthing share). `Preferences.set(key, value)` saves and emits
  `changed`; `MainWindow._on_prefs_changed` re-applies theme/metrics live.

- **`lintunes/mpris.py`** — registers `org.mpris.MediaPlayer2.lintunes` over D-Bus
  so the desktop's media keys / now-playing popup control playback. Spacebar and
  arrow keys are handled locally via `MainWindow.eventFilter`.

- **`lintunes/device_sync.py`** — one-way playlist sync to the Rabbit R1 (Device
  menu). The Rabbit mounts via **MTP/gvfs** (a FUSE path under
  `/run/user/<uid>/gvfs`), not mass storage — so plain file I/O, but never
  copystat and never trust mtimes (diff by name+size). Sync owns exactly
  `Music/<Playlist Name>/` on the device (creates/overwrites/deletes there,
  plus an Auxio-importable `.m3u`); it never deletes outside that folder and
  only ever *reads* local library files.

- **`lintunes/cast/`** — Chromecast playback (Connections menu), using the
  **media-receiver model**: `server.py` runs a `ThreadingHTTPServer` on an
  ephemeral port for the life of a session and the device fetches the *original*
  file itself (bit-exact, no transcode). URLs carry an opaque random token, never
  a path, so traversal is structurally impossible; Range + HEAD are mandatory
  (the device seeks by re-requesting ranges and won't report a duration without
  them). A token resolves to an `_Asset` that is either a file on disk (audio)
  or an in-memory blob (album art, which lives in tags rather than as its own
  file); the two have **separate eviction rings** so a cover can't push out the
  previous track's audio. Art is passed as `play_media(thumb=…)`, which
  pychromecast folds into `metadata["images"]` — that's what a TV paints
  full-screen. `support.py` is the format gate — ALAC, AIFF and protected AAC are
  refused and Player skips them with a status-bar message. `discovery.py` wraps
  `CastBrowser`; `sink.py` is the `PlaybackSink`; `controller.py` owns the
  session and its own `SleepInhibitor`. **pychromecast is imported lazily**, never
  at module scope, so the app still launches where the dep isn't installed yet.
  While casting there is no local PCM, so the visualizer shows the cast glyph
  instead of bars, and position comes from a 500 ms poll of
  `adjusted_current_time` (only trusted while PLAYING — it creeps while paused).

## Conventions & gotchas

- **Tests are organized as `tests/test_roundN.py`** — each development round adds
  a new `test_roundN.py` alongside the topical files (`test_models.py`,
  `test_itunes_importer.py`, etc.). New feature work follows the same pattern.
- **Keep `Player` and `track_table` manager-free where they already are** —
  cross-cutting data is injected via callbacks/signals (e.g. `track_table` takes
  a `playlists_for_track` callback rather than importing the manager).
- **Qt/Wayland gotchas (GNOME/Mutter):** `QDrag.setPixmap` / `setDragCursor` /
  `QCursor.pos()` are unreliable during a drag — `gui/drag_ghost.py` paints its
  own child-widget overlay instead. `QAudioOutput` must not be constructed before
  a `QMainWindow` exists (Qt 6.10 deadlock). Some PyQt signal relays need explicit
  types/lambdas.
- **Music files are only touched deliberately:** tag edits via `tagging.py`,
  and — since Round 18 — artist/album_artist/album edits relocate the file
  inside `LibraryManager.organize_root()` (`<music_folder>/Music`) to keep the
  tree organized iTunes-style (`_maybe_move_file`; undoable; files outside the
  root are never moved; the new path syncs cross-machine via the `location`
  newest-wins merge in `conflict_resolver`). Nothing else may move or rewrite
  music files. The library JSON is the source of truth for everything else.
- **Versioning & self-update:** `__version__` in `lintunes/__init__.py` is
  the single source of truth (`setup.py` regex-reads it, never imports the
  package). Claude bumps minor for feature rounds and patch for fix-only
  rounds as part of each round's final commit; trav decides major bumps. The
  status-bar version button (`gui/version_button.py` + `lintunes/updater.py`)
  checks `origin` shortly after launch and every 4 h, and a click runs
  `git pull --ff-only` then re-execs the app — pushing `master` is
  effectively releasing to the other machines (a new pip dependency still
  needs a manual `pip install -e .` there). **Every round ends with commit
  AND push** (trav's standing request, 2026-07-03: both machines ride the
  bleeding edge, sync as often as possible) — so never leave master in a
  half-working state between commits you push.
- `scripts/` holds one-off maintenance tools (`audit_artwork.py`,
  `recover_artwork.py`, `clear_computed_ratings.py`) run manually against a data
  dir; most default to dry-run and need `--write` to mutate files.
- **Not under version control until recently** — the `*~` files are editor
  backups (gitignored). `data/` and `itunes-test-library/` are gitignored (the
  user's real library + large import fixture).