scripts/verify_checksums.py

#!/usr/bin/env python3
"""Verify a dataset export against metadata/checksums.sha256."""

from __future__ import annotations

import argparse
import hashlib
from pathlib import Path


def sha256(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as handle:
        for chunk in iter(lambda: handle.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument(
        "root",
        nargs="?",
        type=Path,
        default=Path(__file__).resolve().parent.parent,
        help="Dataset repository root (default: parent of this script).",
    )
    args = parser.parse_args()
    root = args.root.resolve()
    checksum_file = root / "metadata" / "checksums.sha256"

    failures: list[str] = []
    checked = 0
    for line in checksum_file.read_text(encoding="utf-8").splitlines():
        if not line.strip():
            continue
        expected, relative = line.split("  ", 1)
        path = root / Path(relative)
        if not path.is_file():
            failures.append(f"missing: {relative}")
        elif sha256(path) != expected:
            failures.append(f"checksum mismatch: {relative}")
        checked += 1

    if failures:
        raise SystemExit("\n".join(failures))
    print(f"Verified {checked} files under {root}")


if __name__ == "__main__":
    main()