# Votify Download System

## Overview

Votify is the primary Spotify download backend. It invokes the `votify-fix` CLI tool (a third-party Python package) as a subprocess, streams its output to the job log, and post-processes the resulting files.

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## How It Works

1. User submits Spotify URLs and options via `POST /api/download`.
2. A job is created and a background thread runs `run_download()`.
3. `run_download()` builds a `votify` CLI command and launches it via `subprocess.Popen`.
4. stdout is streamed line-by-line into the job's output log.
5. On completion, post-processing runs:
   - Flatten nested directories
   - Rename files from embedded metadata
   - Wrap single-track downloads in a folder
   - Convert to MP3 if requested

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## Authentication

Votify authenticates with Spotify using a `cookies.txt` file in Netscape format. This file must be uploaded by an admin via the Settings page before any downloads will succeed.

Path: `/config/cookies.txt` (configurable via `COOKIES_PATH` env var)

A Widevine device certificate (`device.wvd`) may also be required depending on the content. It is uploaded separately via Settings.

Path: `/config/device.wvd` (configurable via `WVD_PATH` env var)

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## Download Options

| Option | Values | Description |
|--------|--------|-------------|
| `audio_quality` | `aac-medium`, `aac-high`, `vorbis-low`, `vorbis-medium`, `vorbis-high` | Audio quality |
| `output_format` | `original`, `mp3` | Keep original format or convert to MP3 |
| `download_mode` | `ytdlp`, `aria2c` | Download backend |
| `save_cover` | bool | Save cover art as a separate image file |
| `save_playlist` | bool | Save playlist metadata file |
| `overwrite` | bool | Re-download if file already exists |
| `download_music_videos` | bool | Include music video downloads |
| `no_lrc` | bool | Skip LRC (lyrics) file generation |
| `video_format` | `mp4`, `webm` | Format for music videos |
| `cover_size` | `small`, `medium`, `large`, `extra-large` | Cover art resolution |
| `truncate` | int (optional) | Limit number of tracks to download |

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## MP3 Conversion

If `output_format` is set to `mp3`, files are converted after download using `ffmpeg` at 320 kbps. The conversion preserves embedded metadata. Original files are deleted after successful conversion.

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## Cancellation

The Popen process handle is stored on the job dict. `POST /api/jobs/<id>/cancel` calls `process.terminate()`, which sends SIGTERM to the votify subprocess.

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## Post-Processing Detail

After the subprocess exits, `post_process_votify_files()` runs:

1. **Snapshot before** — records which audio files existed before the download started (to identify new files).
2. **Flatten** — collapses single-subdirectory chains into the parent folder.
3. **Rename** — calls `rename_from_metadata()` to produce `Title - Artist.ext` filenames.
4. **Wrap singles** — if exactly one file downloaded with no enclosing folder, wraps it in a folder named after the file.
5. **Cleanup** — removes leftover empty directories.

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## External Dependencies

| Dependency | Purpose |
|------------|---------|
| `votify-fix` (GitHub: GladistonXD/votify-fix) | Spotify download CLI |
| `ffmpeg` | MP3 conversion |
| `aria2c` | Optional download manager |
| `yt-dlp` | Default download manager |
| `mp4decrypt` (Bento4) | MP4 DRM decryption |

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## Limitations

- Requires valid Spotify cookies (must be refreshed periodically when they expire).
- DRM-protected content requires a Widevine device certificate.
- Quality options are limited to what Votify and the Spotify API expose.

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## Key Files

| File | Relevance |
|------|-----------|
| [app.py](../app.py) | `run_download()`, `post_process_votify_files()`, route `/api/download` |
| [utils.py](../utils.py) | `rename_from_metadata()`, `cleanup_empty_dirs()` |
| [Dockerfile](../Dockerfile) | Installation of votify-fix, ffmpeg, aria2, Bento4 |