DALGLI0/Zadanie3

from sys import argv
import sys
import binascii
import base64

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 = "10001000000100001"
    # 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,crc):
    poly16 = "10001000000100001"
    l_poly16 = len(poly16)
    message = bytearray(message, 'ascii')
    message = format(int.from_bytes(message, "big"), "b")
    while len(message) % 8 != 0:
        message = "0" + message
    dec = int(crc, 16)
    crc2=bin(dec)[2:]
    while len(crc2) % 8 != 0:
        crc2 = "0" + crc2
    msg=message+crc2
    while len(msg) % 8 != 0:
        msg = "0" + msg
    obroc = list(msg)
    for i in range(l_poly16 - 1):
        if obroc[i] == "0":
            obroc[i] = "1"
        elif obroc[i] == '1':
            obroc[i] = "0"

    msg = "".join(obroc)

    remainder = divide(msg)

    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 = "10001000000100001"
    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)
    ab=binnahex(remainder)
    d=str(base64.b16decode(ab))[2:-1]
    message_final = a + d
    message_final = bytearray(message_final, 'ascii')
    d = bytearray(d, 'ascii')
    print("calosc : ", message_final)
    print("crc hex : ", ab)   
    print("crc ascii : ", d)       
    decode(a,ab)

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