# Video Download Backend

FastAPI service that wraps [yt-dlp](https://github.com/yt-dlp/yt-dlp) to expose endpoints for inspecting video metadata and downloading media files.

## Requirements

- Python 3.11+
- `fastapi`, `uvicorn[standard]`, `yt-dlp` (install via `pip install -r requirements.txt`)
- `ffmpeg` available in PATH (required for merging best video and audio streams into mp4)
- `aiofiles` (installed via `requirements.txt`) to support static file serving

## Running locally

```bash
cd download-backend
python -m venv .venv
. .venv/bin/activate
pip install -r requirements.txt
uvicorn app.main:app --reload --port 8000
```

The API will be available at http://localhost:8000. Interactive docs are served at http://localhost:8000/docs.

## API Overview

- `GET /health` – simple readiness check.
- `GET /api/info?url=<video_url>` – returns normalized metadata plus available formats for a given video.
- `POST /api/download` – downloads the requested video (optionally specifying a `format_id`), stores it in `tmp_downloads/`, and returns a JSON response with a `download_url`. The service inspects available formats, preferring MP4 progressive or MP4 video + M4A audio when available, and gracefully falls back through compatible combinations before using yt-dlp's generic best selection.

Downloaded files are served at `http://localhost:8000/downloads/<file-name>` for direct access while the server is running.

### Download payload

```json
{
  "url": "https://www.youtube.com/watch?v=...",
  "format_id": "22",
  "filename": "optional-custom-name"
}
```

- `format_id` matches the entries in the `formats` array returned by `/api/info`.
- `filename` is optional; omit the extension to let yt-dlp set it automatically.

Temporary files are cleaned up automatically after each request.