from sys import argv
import sys
import binascii

def toBinary(string):
    return "".join([format(ord(char),'#010b')[2:] for char in string])

def binnahex(var):
    all = {"0000": "0",
            "0001": "1",
            "0010": "2",
            "0011": "3",
            "0100": "4",
            "0101": "5",
            "0110": "6",
            "0111": "7",
            "1000": "8",
            "1001": "9",
            "1010": "A",
            "1011": "B",
            "1100": "C",
            "1101": "D",
            "1110": "E",
            "1111": "F"
            }
    i = 0
    output = ""

    while (len(var) % 4 != 0):
        var = "0" + var

    while (i < len(var)):
        output = output + all[var[i:i + 4]]
        i = i + 4

    output = output.lstrip("0")
    output = "0" if len(output) == 0 else output

    return output

#XOR
def xor(a, b):
 
    # init
    result = []
 
    # porownuje znaki
    for i in range(1, len(b)):
        if a[i] == b[i]:
            result.append('0')
        else:
            result.append('1')
 
    return ''.join(result)
 
 
# dzielenie modulo 2
def divide(message, poly16):
 
    # Ilosc bitow dla operacji XOR 'na raz'
    step = len(poly16)
 
    # podzial krok po kroku
    temp = message[0 : step]
 
    while step < len(message):
 
        if temp[0] == '1':
 
            temp = xor(poly16, temp) + message[step]
 
        else:   
            # jezeli 1 bit po lewej == 0
            temp = xor('0'*step, temp) + message[step]
 
        # kolejny krok
        step += 1
 
    if temp[0] == '1':
        temp = xor(poly16, temp)
    else:
        temp = xor('0'*step, temp)
 
    check = temp
    return check

def decode(message_final,poly16,crc):
    l_poly16 = len(poly16)
    appended_message2 = toBinary(message_final)
    obroc = list(appended_message2)
    for i in range(l_poly16 - 1):
        if obroc[i] == "0":
            obroc[i] = "1"
        elif obroc[i] == '1':
            obroc[i] = "0"

    appended_message2 = "".join(obroc)
    
    dec = int(crc, 16)
    crc2=bin(dec)[2:]
    msg=appended_message2+crc2
    remainder = divide(msg, poly16)
    #Poprawione sprawdzanie
    suma = 0
    for i in range(0, len(remainder)):
            if '1' in remainder:
                suma = suma+1

    if suma == 0:
        print("true ")
    elif suma > 0:
        print("false")

def encode(message, poly16):
    
    a=message
    
    message = bytearray(message, 'ascii')
    message = format(int.from_bytes(message, "big"), "b")
    l_poly16 = len(poly16)
    message = message + '0'*(l_poly16-1)
    while len(message) % 8 != 0:
        message = "0" + message
    obroc = list(message)
    for i in range(l_poly16 - 1):
        if obroc[i] == "0":
            obroc[i] = "1"
        elif obroc[i] == '1':
            obroc[i] = "0"

    message = "".join(obroc)
    remainder = divide(message, poly16)
    ab=binnahex(remainder)
    message_final = a + ab
    message_final = bytearray(message_final, 'ascii')
    ab = bytearray(ab, 'ascii')
    print("calosc : ", message_final)
    print("crc : ", ab)      

    
poly16 = "10001000000100001"

def main():
    global message
    message = list(argv[1])
    flag = argv[2] 
    if flag == 'encode':
        encode(sys.argv[1], poly16)
    elif flag == 'decode':
        crc = argv[3] 
        decode(sys.argv[1], poly16,sys.argv[3])    
if __name__ == '__main__':
    main()