https en wikipedia orgwikiautokeycipher an autokey cipher also known as the autoclave cipher is a cipher that incorporates the message the plaintext into the key the key is generated from the message in some automated fashion sometimes by selecting certain letters from the text or more commonly by adding a short primer key to the front of the message encrypt a given plaintext string and key string returning the encrypted ciphertext encrypthello world coffee jsqqs avvwo encryptcoffee is good as python thealgorithms vvjfpk wj ohvp su ddylsv encryptcoffee is good as python 2 traceback most recent call last typeerror key must be a string encrypt thealgorithms traceback most recent call last valueerror plaintext is empty decrypt a given ciphertext string and key string returning the decrypted ciphertext decryptjsqqs avvwo coffee hello world decryptvvjfpk wj ohvp su ddylsv thealgorithms coffee is good as python decryptvvjfpk wj ohvp su ddylsv traceback most recent call last valueerror key is empty decrypt527 26 thealgorithms traceback most recent call last typeerror ciphertext must be a string encrypt a given plaintext string and key string returning the encrypted ciphertext encrypt hello world coffee jsqqs avvwo encrypt coffee is good as python thealgorithms vvjfpk wj ohvp su ddylsv encrypt coffee is good as python 2 traceback most recent call last typeerror key must be a string encrypt thealgorithms traceback most recent call last valueerror plaintext is empty decrypt a given ciphertext string and key string returning the decrypted ciphertext decrypt jsqqs avvwo coffee hello world decrypt vvjfpk wj ohvp su ddylsv thealgorithms coffee is good as python decrypt vvjfpk wj ohvp su ddylsv traceback most recent call last valueerror key is empty decrypt 527 26 thealgorithms traceback most recent call last typeerror ciphertext must be a string
def encrypt(plaintext: str, key: str) -> str:
    
    if not isinstance(plaintext, str):
        raise TypeError("plaintext must be a string")
    if not isinstance(key, str):
        raise TypeError("key must be a string")

    if not plaintext:
        raise ValueError("plaintext is empty")
    if not key:
        raise ValueError("key is empty")

    key += plaintext
    plaintext = plaintext.lower()
    key = key.lower()
    plaintext_iterator = 0
    key_iterator = 0
    ciphertext = ""
    while plaintext_iterator < len(plaintext):
        if (
            ord(plaintext[plaintext_iterator]) < 97
            or ord(plaintext[plaintext_iterator]) > 122
        ):
            ciphertext += plaintext[plaintext_iterator]
            plaintext_iterator += 1
        elif ord(key[key_iterator]) < 97 or ord(key[key_iterator]) > 122:
            key_iterator += 1
        else:
            ciphertext += chr(
                (
                    (ord(plaintext[plaintext_iterator]) - 97 + ord(key[key_iterator]))
                    - 97
                )
                % 26
                + 97
            )
            key_iterator += 1
            plaintext_iterator += 1
    return ciphertext


def decrypt(ciphertext: str, key: str) -> str:
    
    if not isinstance(ciphertext, str):
        raise TypeError("ciphertext must be a string")
    if not isinstance(key, str):
        raise TypeError("key must be a string")

    if not ciphertext:
        raise ValueError("ciphertext is empty")
    if not key:
        raise ValueError("key is empty")

    key = key.lower()
    ciphertext_iterator = 0
    key_iterator = 0
    plaintext = ""
    while ciphertext_iterator < len(ciphertext):
        if (
            ord(ciphertext[ciphertext_iterator]) < 97
            or ord(ciphertext[ciphertext_iterator]) > 122
        ):
            plaintext += ciphertext[ciphertext_iterator]
        else:
            plaintext += chr(
                (ord(ciphertext[ciphertext_iterator]) - ord(key[key_iterator])) % 26
                + 97
            )
            key += chr(
                (ord(ciphertext[ciphertext_iterator]) - ord(key[key_iterator])) % 26
                + 97
            )
            key_iterator += 1
        ciphertext_iterator += 1
    return plaintext


if __name__ == "__main__":
    import doctest

    doctest.testmod()
    operation = int(input("Type 1 to encrypt or 2 to decrypt:"))
    if operation == 1:
        plaintext = input("Typeplaintext to be encrypted:\n")
        key = input("Type the key:\n")
        print(encrypt(plaintext, key))
    elif operation == 2:
        ciphertext = input("Type the ciphertext to be decrypted:\n")
        key = input("Type the key:\n")
        print(decrypt(ciphertext, key))
    decrypt("jsqqs avvwo", "coffee")