from random import randint as rand
from math import log10

class Scoring:
    floor = 0

    def __init__(self):
        self.trigrams = {}
        # read trigrams from file
        with open(os.path.dirname(os.path.realpath(__file__)) + '/english_trigrams.txt', 'r') as trigram_file:
            for line in trigram_file:
                trigram, score = line.split(' ')
                self.trigrams[trigram.lower()] = int(score)

        score_sum = sum(self.trigrams.values())
        self.floor = log10(0.1 / score_sum)

        for i in list(self.trigrams.keys()):
            self.trigrams[i] = log10(float(self.trigrams[i]) / score_sum)
        pass

    def get_score(self, text):
        score = 0

        for k in range(len(text) - 3):
            trigram = text[k:k + 3]
            if trigram in self.trigrams:
                score += self.trigrams[trigram]
            else:
                score += self.floor
        return score


def randomize_key(key):
    a_index = rand(0, 25)
    b_index = rand(0, 25)
    a = key[a_index]
    b = key[b_index]
    key = key[:a_index] + b + key[a_index + 1:]
    key = key[:b_index] + a + key[b_index + 1:]

    return key


if __name__ == "__main__":
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('FILE')
    args = parser.parse_args()

    t = ''.join([x for x in open(args.FILE, "r").read().lower() if x.isalpha()])
    import os
    words = open(os.path.abspath(os.path.dirname(__file__))+"/common.txt", "r").read().split('\n')

    occurance_string = 'etaoinsrhdlucmfywgpbvkxqjz'

    occur_count = {chr(x+0x61): 0 for x in range(26)}
    for char in t:
        occur_count[char]+=1
    mapping = {}
    sorted_occur = sorted(occur_count, key=occur_count.__getitem__, reverse=True)
    for i in range(26):
        mapping[occurance_string[i]]=sorted_occur[i]
    key = ''.join([x for _, x in sorted(mapping.items())])

    import re
    import mono

    best_score = -10000
    best_key = key

    scoring = Scoring()

    trys = 0
    while trys < 20000:
        score = 0
        tmp = randomize_key(key)
        plain = mono.mono_decrypt(t, tmp)
        #for word in words:
        #    search_res = re.search(word, plain, re.IGNORECASE)
        #    if search_res:
        #        score += len(word)
        score = scoring.get_score(plain)
        if score > best_score:
            trys = 0
            best_score = score 
            best_key = key
            key=tmp
            print(best_score)
        else:
            trys+=1

    print(best_key)
    print()
    print(mono.mono_decrypt(t, best_key))