Vingere

from typing import List
import argparse

IDX_OF_LOWERCASE_A = ord("a")
CIPHER_TEXT = "oplxombzseviwyklcgvmghupwiqmyfsijlkyt"  # "BQQCKVOUCKORNOAUSRFUAGLJHJBTKDMSRPUVNROCNF"

def convert_to_base(key_number: int, base: int=26):
    key_list = []
    while key_number > 0:
        key_list.insert(0, key_number % base)
        key_number //= base
    print('Vigenère key is:', ''.join(
        [chr(n + IDX_OF_LOWERCASE_A) for n in key_list]))
    return key_list

def crypt(cipher: str, key: List[int], *, decrypt=True):
    cipher_list = [ord(c) - IDX_OF_LOWERCASE_A for c in cipher.lower()]
    key_pointer = 0
    plain_numeric = []
    operator = -1 if decrypt else 1
    for c in cipher_list:
        plain_numeric.append((c + key[key_pointer] * operator) % 26)
        key_pointer = (key_pointer + 1) % len(key)
    return ''.join([chr(d + IDX_OF_LOWERCASE_A) for d in plain_numeric])


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description='Vingere decryption tool')
    parser.add_argument('key', type=int, help='enter your key as an integer')
    parser.add_argument('-e', '--encrypt', default=None)
    args = parser.parse_args()
    key_26 = convert_to_base(int(args.key), 26)
    if args.encrypt is None:
        print(crypt(CIPHER_TEXT, key_26, decrypt=True))
    else:
        print(crypt(args.encrypt, key_26, decrypt=False))