import shutil
from argparse import ArgumentParser
from pathlib import Path
from random import randbytes

from rc4 import rc4


def generate_key(key_length: int) -> bytes:
    """
    Generates a random key with a length of key_length bytes
    """
    return randbytes(key_length)


if __name__ == "__main__":
    parser = ArgumentParser()
    parser.add_argument("group", type=Path, help="Group root directory")
    parser.add_argument("file", type=Path, help="File to decrypt for this group")
    key_opts = parser.add_mutually_exclusive_group(required=True)
    key_opts.add_argument(
        "--key-file",
        "-k",
        dest="key_file",
        type=Path,
        help="Key source file for this group",
    )
    key_opts.add_argument(
        "--key-length",
        "-l",
        dest="key_length",
        type=int,
        help="Key length for this group",
    )
    args = parser.parse_args()

    # Create required files in group directory
    shutil.copy(args.file, args.group / "data_decrypted")
    if args.key_file is not None:
        try:
            shutil.copy(args.key_file, args.group / "key")
        except shutil.SameFileError:
            pass
    else:
        with open(args.group / "key", "wb") as key_file:
            key_file.write(generate_key(args.key_length))
    rc4(args.group / "data_decrypted", args.group / "data_encrypted", args.group / "key")