###not done

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives import padding



def decrypt(nameIn,nameOut,key,iv,encMode):

    file = open( "key.key", 'br')
    key = file.read()

    if iv != None:
        ivRead = open(nameIn, "br") # opening for [r]eading as [b]inary
        iv = ivRead.read(16) # if you only wanted to read 512 bytes, do .read(512)
        ivRead.close()

    file = open(encMode, "r")
    file = file.read()
    alg = file.split('\n', 1)[0]

    try: 
        mode = file.split('\n', 1)[1]
    except IndexError:
        mode = None

   # with open(nameIn, 'rb') as file1:
   #     with open(nameIn, 'wb') as file2:
   #         file2.write(file1.read()[16:])
   #         file.close()


    encFile = open(nameIn, "rb+")
    encodedTxt = encFile.read()

    #data = file[16:]
    #encOut.seek(16,0) #<-- AttributeError: 'bytes' object has no attribute 'seek'
    #print(encOut.tell())
    #print(encOut)          

    #print(os.path.getsize(nameIn))


    if alg == "chacha20":
            algorithm = algorithms.ChaCha20(key, iv)
            cipher = Cipher(algorithm, mode=None)
    elif alg == "aes":
            if  mode == "cfb":
                cipher = Cipher(algorithms.AES(key),modes.CFB(iv))
            elif mode == "obf":
                cipher = Cipher(algorithms.AES(key),modes.OFB(iv))
            elif mode == "ecb":
                cipher = Cipher(algorithms.AES(key),modes.ECB())
            elif mode == "cbc":
                cipher = Cipher(algorithms.AES(key),modes.CBC(iv))
            else:
                 print ("Invalid mode, please append the correct one")
                 exit()
    else:
        print ("Invalid algorithm, please append the correct one")
        exit()

    decryptor = cipher.decryptor()


    unpadder = padding.PKCS7(128).unpadder()

    
    dec = decryptor.update(encodedTxt) + decryptor.finalize()

    unpadded_data = unpadder.update(dec) + unpadder.finalize()



    fileOut = open(nameOut, 'wb+')
    fileOut.write(unpadded_data)  
    fileOut.close



def main():   

    nameIn, nameOut, key = input("Write what file to decrypt, where you want the output and the key to decrypt \n").split()
    
    ans = input("do you have the Iv? [Y/N] ")
    ans = ans.lower()
#
    if ans == "y":
        iv = input("Paste the Iv string here  \n")
    else:
        iv = None
#
    ans = input("Do you have the encryption mode? [Y/N] ")
    ans = ans.lower()
#
    if ans == "y":
        encMode = input("In what file do you have that information ")
    else: 
        print("You need to know the encoding algorithm and mode in order to decode")
#



    #testing
    #nameIn = "encoded.txt"
    #nameOut = "decrypted.txt"
    #key = "key.key"
    #iv = "y"
    #encMode = "algorithm.txt"

    decrypt(nameIn, nameOut, key, iv, encMode)
    
    
if __name__ == main():
    main()