#!/usr/bin/env python3

# DRACONDI: Dual-key Rotating Alphabet CONDI

import sys, re
from collections import OrderedDict
from random import randint, choice
from string import ascii_lowercase

def prepmsg(s:str):
    return re.sub(r'[^a-z]', '', s.lower())

def dracondi_key(keyphrase:str):
    prekey = ''
    oa = ord('a')
    for c in prepmsg(keyphrase):
        while prekey.find(c) != -1 and len(prekey) < 26:
            c = chr(oa + ((25 + ord(c) - oa) % 26))
        prekey += c
    offs = len(prekey) % 26
    alpha = prekey + ''.join(ascii_lowercase)
    unshifted = ''.join(list(OrderedDict.fromkeys(alpha).keys()))
    return (unshifted + unshifted)[offs:offs+26]

def dracondi_enc(msg:str, ka1:str, ka2:str):
    offs = randint(0, 25)
    res = ka1[offs]
    for i,c in enumerate(prepmsg(msg)):
        rc = ka1[(ka1.index(c) + offs) % 26]
        res += rc
        offs = (ka2.index(rc) + i + 1) % 26
    l = len(res) % 5
    if l > 0:
        res += ''.join([choice(ascii_lowercase) for i in range(0, 5 - l)])
    return ' '.join([res[i:i+5] for i in range(0, len(res), 5)])

def dracondi_dec(msg:str, ka1:str, ka2:str):
    res = ''
    msg = prepmsg(msg)
    offs = ka1.index(msg[0])
    for i,c in enumerate(msg[1:]):
        res += ka1[(26 + ka1.index(c) - offs) % 26]
        offs = (ka2.index(c) + i + 1) % 26
    return res

# entrypoint parameters: [mode] [key1] [key2]
# modes: e - encrypt, d - decrypt, k - print out keyed alphabets
def main():
    mode = sys.argv[1].lower()
    kp1 = sys.argv[2]
    kp2 = sys.argv[3]
    ka1 = dracondi_key(kp1)
    ka2 = dracondi_key(kp2)
    if mode.startswith('e'):
        msg = sys.stdin.read()
        print(dracondi_enc(msg, ka1, ka2))
    elif mode.startswith('k'):
        print('Keyed alphabet 1:', ka1)
        print('Keyed alphabet 2:', ka2)
    else:
        msg = sys.stdin.read()
        print(dracondi_dec(msg, ka1, ka2))

if __name__ == '__main__':
    main()