import argparse
from typing import Optional
from typing import Sequence

BLACKLIST = [
    b'BEGIN RSA PRIVATE KEY',
    b'BEGIN DSA PRIVATE KEY',
    b'BEGIN EC PRIVATE KEY',
    b'BEGIN OPENSSH PRIVATE KEY',
    b'BEGIN PRIVATE KEY',
    b'PuTTY-User-Key-File-2',
    b'BEGIN SSH2 ENCRYPTED PRIVATE KEY',
    b'BEGIN PGP PRIVATE KEY BLOCK',
]


def main(argv: Optional[Sequence[str]] = None) -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument('filenames', nargs='*', help='Filenames to check')
    args = parser.parse_args(argv)

    private_key_files = []

    for filename in args.filenames:
        with open(filename, 'rb') as f:
            content = f.read()
            if any(line in content for line in BLACKLIST):
                private_key_files.append(filename)

    if private_key_files:
        for private_key_file in private_key_files:
            print(f'Private key found: {private_key_file}')
        return 1
    else:
        return 0


if __name__ == '__main__':
    exit(main())
