"""Check SHA-256 hashes of the distributed files. This is integrity, not proof checking."""
from pathlib import Path, PurePosixPath
import hashlib
import sys

root=Path(__file__).resolve().parent
manifest=root/'MANIFEST.sha256'
if not manifest.is_file():
    raise SystemExit('MANIFEST.sha256 is missing.')
errors=[]; checked=0
for line in manifest.read_text(encoding='utf-8').splitlines():
    if not line.strip(): continue
    try:
        expected,name=line.split('  ',1)
    except ValueError:
        errors.append('Malformed manifest line');continue
    rel=PurePosixPath(name)
    if rel.is_absolute() or '..' in rel.parts or len(expected)!=64:
        errors.append(f'Unsafe or malformed entry: {name}');continue
    path=root.joinpath(*rel.parts)
    if not path.is_file():
        errors.append(f'Missing: {name}');continue
    actual=hashlib.sha256(path.read_bytes()).hexdigest()
    if actual!=expected:
        errors.append(f'Changed: {name}')
    checked+=1
if errors:
    print('\n'.join(errors),file=sys.stderr)
    raise SystemExit(1)
print(f'Integrity verified for {checked} distributed files. This is not mathematical proof verification.')