#!/usr/bin/env python3
"""Verify SHA-256 hashes for the listed release files, without network access."""
from __future__ import annotations

import hashlib
import re
from pathlib import Path

ROOT = Path(__file__).resolve().parent


def verify() -> int:
    manifest = ROOT / "SHA256SUMS.txt"
    if not manifest.is_file():
        raise ValueError("Missing release SHA256SUMS.txt")
    entries = manifest.read_text(encoding="utf-8").splitlines()
    if not entries:
        raise ValueError("Empty checksum manifest")
    seen = set()
    for line in entries:
        match = re.fullmatch(r"([0-9a-f]{64})  (.+)", line)
        if match is None:
            raise ValueError("Malformed checksum manifest line")
        expected, relative = match.groups()
        path = (ROOT / relative).resolve()
        if not path.is_relative_to(ROOT) or relative in seen:
            raise ValueError("Unsafe or duplicate checksum path")
        seen.add(relative)
        if not path.is_file():
            raise ValueError(f"Missing release file: {relative}")
        if hashlib.sha256(path.read_bytes()).hexdigest() != expected:
            raise ValueError(f"Checksum mismatch: {relative}")
    return len(entries)


if __name__ == "__main__":
    try:
        print(f"PASS: {verify()} listed release files match SHA-256 hashes.")
    except (OSError, ValueError) as error:
        raise SystemExit(f"FAIL: {error}")