# paper CLI — Design

A CLI tool that downloads academic papers by DOI from Anna's Archive and converts them to markdown.

## CLI Interface

```
paper <DOI>
```

Single positional argument. Markdown output goes to stdout.

```
paper 10.1038/nature12373 > paper.md
```

## Download Flow

1. Request `https://annas-archive.org/scidb/<DOI>` with a browser-like User-Agent
2. Parse HTML for `<iframe>` or `<embed>` with `id="pdf"` — extract `src` for direct PDF URL
3. Fallback: find any link ending in `.pdf`
4. Download PDF to a temp file
5. Exit with clear error if no PDF found

## Conversion

1. Shell out to `marker_single <tempfile.pdf> --output_dir <tempdir>`
2. Read the generated `.md` file from the output dir
3. Print to stdout
4. Clean up temp dir

## Error Handling

- `marker_single` not on PATH: tell user to install (`pip install marker-pdf`)
- Conversion failure: forward marker's stderr
- Network errors: surface reqwest errors clearly
- No PDF found: specific error message with the DOI

## Dependencies

- `clap` — argument parsing
- `reqwest` (blocking, rustls-tls) — HTTP
- `scraper` — HTML parsing
- `tempfile` — temp directory
- `anyhow` — error handling

## Dev Environment

The nix flake includes Rust nightly toolchain and marker-pdf in the devshell.