from pycipher import SimpleSubstitution as SimpleSub

import random

import re

from ngram_score import ngram_score

fitness = ngram_score('quadgrams.txt') # load our quadgram statistics

ctext = 'pmpafxaikkitprdsikcplifhwceigixkirradfeirdgkipgigudkcekiigpwrpucikceiginasikwduearrxiiqepcceindgmieinpwdfprduppcedoikiqiasafmfddfipfgmdafmfdteiki'

ctext = re.sub('[^A-Z]', '', ctext.upper())

maxkey = list('ABCDEFGHIJKLMNOPQRSTUVWXYZ')

maxscore = -99e9

parentscore, parentkey = maxscore, maxkey[:]

print "Substitution Cipher solver, you may have to wait several iterations"

print "for the correct result. Press ctrl+c to exit program."

# keep going until we are killed by the user

i = 0

while 1:

i = i + 1

random.shuffle(parentkey)

deciphered = SimpleSub(parentkey).decipher(ctext)

parentscore = fitness.score(deciphered)

count = 0

while count < 1000:

a = random.randint(0, 25)

b = random.randint(0, 25)

child = parentkey[:]

# swap two characters in the child

child[a], child[b] = child[b], child[a]

deciphered = SimpleSub(child).decipher(ctext)

score = fitness.score(deciphered)

# if the child was better, replace the parent with it

if score > parentscore:

parentscore = score

parentkey = child[:]

count = 0

count = count + 1

# keep track of best score seen so far

if parentscore > maxscore:

maxscore, maxkey = parentscore, parentkey[:]

print '\nbest score so far:', maxscore, 'on iteration', i

ss = SimpleSub(maxkey)

print ' best key: ' + ''.join(maxkey)

print ' plaintext: ' + ss.decipher(ctext)