"""Module stego

to be filled in
"""

import sys
import getopt
import nltk
import random
from cPickle import dump,load

def make_dict(file):
    f = open(file)
    cry = f.read()
    tokens = nltk.word_tokenize(cry)
    text = nltk.Text(tokens)
    words = [w.lower() for w in text]
    bigrams=nltk.bigrams(words)
    cfd = nltk.ConditionalFreqDist() # fix for init before pickling
    for tuples in bigrams:
        cfd[tuples[0]].inc(tuples[1])
    output = open('cfd.pkl', 'wb')
    dump(cfd, output)
    output.close()

def markov_encode(word, encodedword):
    input = open('cfd.pkl', 'rb')
    cfdist = load(input)
    input.close()
    wd = bitstring = ''
    addedbits=wert=tootal=xx=jj=rr=0
    encodedword+="x"
    loppy=(len(encodedword)*8)
    lippy=len(encodedword)
    while wert < lippy: # number of bits
        wd += " " + word
        # how many bits can we encode in next decision
        lenny = len(cfdist[word].items())
        while lenny<=1:
            # choose random next word
            word = random.choice(cfdist.conditions())
            lenny = len(cfdist[word].items())
            wd = wd + " " + word
        bits = 1
        while (2 << bits) < lenny:
            bits+=1
        addedbits=0
        
        for j in range(bits):
            addedbits+=(ord(encodedword[wert])>>(rr%8)&1)<<j 
            bitstring += str(ord(encodedword[wert])>>(rr%8)&1)
            rr+=1
            xx+=1
            if (xx%8)==0:
                bitstring=''
                wert+=1
            if xx == loppy:
                break

        word =''.join(cfdist[word].items()[addedbits][:1])
        tootal+=bits
    return wd

def markov_decode(text):
    input = open('cfd.pkl', 'rb')
    cfdist = load(input)
    input.close()
    newtext=text.split()
    decodedchar=j=xx=result=jj=rr=0
    bitstring = wd = ""
    for i in range(len(newtext)-1):
        lenny = len(cfdist[newtext[i]].items()) # bits are encoded for next word
        if lenny<=1:
            continue # goto next word
        bits = 1
        while (2 << bits) < lenny:
            bits+=1
        xx=0
        for x in cfdist[newtext[i]].items():
            yy = ''.join(x[:1])
            if yy == newtext[i+1]:
                result=xx
                xx = 0
                break
            xx+=1
        for j in range(bits):
            if (j+jj)%8 == 0:
                if (j+jj)>0:
                    wd+= chr(decodedchar)
                    bitstring=''
                    decodedchar=0
            decodedbit=(result>>j)&1
            bitstring += str(decodedbit)
            rr+=1
            decodedchar+=decodedbit<<((j+jj)%8)
        jj+=bits
    return wd

def main(argv=None):
    if argv is None:
        argv = sys.argv
    try:                                
        opts, args = getopt.getopt(argv[1:], "hdes", ["help" , "dict", "encode" , "decode"])
    except getopt.GetoptError:          
        print __doc__
        sys.exit(2)            

    for o,a in opts:
        if o in ("-h", "--help"):
            print __doc__
            sys.exit(0)
        if o in ("-d", "--dict"):
            make_dict(args[0])
            sys.exit(0)
        if o in ("-e", "--encode"):
            print markov_encode(args[0], args[1])
            sys.exit(0)
        if o in ("-s", "--decode"):
            print markov_decode(args[0])
            sys.exit(0)


if __name__ == "__main__":
    sys.exit(main())