#!/usr/bin/env python3
"""Create a deterministic SHA-256 manifest for release files."""

from __future__ import annotations

import argparse
import hashlib
import os
from pathlib import Path


EXCLUDED_PARTS = {".git", "__pycache__", ".pytest_cache"}


def included(path: Path, root: Path) -> bool:
    relative = path.relative_to(root)
    return (
        path.is_file()
        and path.name != "MANIFEST.sha256"
        and not path.name.endswith(".partial")
        and not any(part in EXCLUDED_PARTS for part in relative.parts)
    )


def digest(path: Path, chunk_size: int = 64 * 1024 * 1024) -> str:
    value = hashlib.sha256()
    with path.open("rb") as stream:
        while block := stream.read(chunk_size):
            value.update(block)
    return value.hexdigest()


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--root", required=True, type=Path)
    args = parser.parse_args()
    root = args.root.resolve()
    files = sorted(path for path in root.rglob("*") if included(path, root))
    temporary = root / ".MANIFEST.sha256.partial"
    with temporary.open("w", encoding="utf-8") as stream:
        for index, path in enumerate(files, start=1):
            relative = path.relative_to(root).as_posix()
            stream.write(f"{digest(path)}  {relative}\n")
            print(f"[manifest] {index:,}/{len(files):,} {relative}", flush=True)
        stream.flush()
        os.fsync(stream.fileno())
    os.replace(temporary, root / "MANIFEST.sha256")


if __name__ == "__main__":
    main()