import argparse
import re
import vig
import os


def probe(key, substrings, words):
    key_hits = {}
    for x in range(ord('a'), ord('z')+1):
        count = 0
        for substr in substrings:
            if re.search(vig.decrypt(key+chr(x), substr[0:len(key)+1]), words):
                count += 1
        key_hits[key+chr(x)] = count
    best_val = [val for key, val in sorted(
        key_hits.items(), key=lambda ele: ele[1])][-1]
    return {key: val for key, val in key_hits.items() if val == best_val}


def remove_crap_from_list(tree, max_depth, thr):
    best = [-x * thr for x in range(max_depth+2)]
    for key, val in tree.items():
        if val > best[len(key)]:
            best[len(key)] = val

    import copy
    tmp = copy.copy(list(tree.items()))
    for key, val in tmp:
        for i in range(len(key), max_depth+1):
            if val < (best[i] - thr + (i-len(key))*thr*1.5):
                del tree[key]
                break


def crack(substrings, words):
    tree = {"": 0}
    while tree:
        curr = [key for key, val in sorted(
            tree.items(), key=lambda ele: ele[1])][-1]
        if len(curr) == len(substrings[0]):
            return curr
        del tree[curr]
        tree.update(probe(curr, substrings, words))
        remove_crap_from_list(tree, len(substrings[0]), 10)


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('FILE')
    parser.add_argument('--keylen', type=int, metavar="INT", required=True)
    args = parser.parse_args()

    t = ''.join([x for x in open(args.FILE, "r").read().lower() if x.isalpha()])
    substrings = [(t[i:i+args.keylen]) for i in range(0, len(t), args.keylen)]
    words = open(os.path.abspath(os.path.dirname(__file__))+"/words.txt", "r").read()

    print(crack(substrings, words))