# drift

Discovers similar artists via Last.fm and builds playlists from your local music library. Point it at a directory, pick a seed artist, and get a playlist of tracks weighted by artist similarity and popularity.

## Metadata requirements

Your music files need **MusicBrainz artist IDs** in their tags (`MUSICBRAINZ_ARTISTID`). Without these, tracks are skipped during indexing. Track titles help with popularity scoring — drift matches them against Last.fm's top tracks to bias toward well-known songs.

Most taggers (Picard, beets, etc.) can write MusicBrainz IDs automatically.

## Setup

You need a Last.fm API key. Create one at https://www.last.fm/api/account/create, then set it:

```
echo 'LASTFM_API_KEY=your_key_here' > .env
```

Or export it directly — drift loads `.env` automatically via dotenvy.

## Usage

### Index your library

```
drift index /path/to/music
```

Scans for tagged files, fetches similar artists and top tracks from Last.fm, and stores everything in a local SQLite database (`~/.local/share/drift/drift.db`).

Flags:
- `-v` — print progress
- `-f` — re-index artists that were already indexed

### Build a playlist

```
drift build
```

Opens an interactive picker to choose a seed artist. Or pass an artist name directly:

```
drift build "Radiohead"
```

Flags:
- `-n 30` — number of tracks (default 20)
- `-p 8` — popularity bias, 0–10 (default 5, higher = prefer popular tracks)
- `-s` — interleave artists evenly instead of score order
- `-r` — fully randomize track order
- `-v` — print track scores to stderr

### Output

By default, drift prints file paths to stdout — pipe it wherever you want.

#### MPD

```
drift build -m
```

Queues tracks directly in MPD. Requires `MPD_HOST` and `MPD_MUSIC_DIR` environment variables.

#### Airsonic

```
drift build -a
```

Creates a playlist in Airsonic/Navidrome. Requires `AIRSONIC_URL`, `AIRSONIC_USER`, and `AIRSONIC_PASS` environment variables.