"""Optional helper script to fetch larger real datasets for extended benchmarking.

This script is intentionally conservative and does not run by default in package installation.
Users should edit accession lists and data sources for their use case and licensing constraints.
"""

from __future__ import annotations

from pathlib import Path


def main() -> None:
    out = Path("examples/external_real_data")
    out.mkdir(parents=True, exist_ok=True)
    readme = out / "README.txt"
    readme.write_text(
        "Populate this directory with codon alignments and trees from your chosen curated datasets.\n"
        "Then point babappa validate/fit-null/score to those files.\n",
        encoding="utf-8",
    )
    print(f"Prepared {out}")


if __name__ == "__main__":
    main()
