Loran Cipher

CaesarCipher.py

'''
By Loran E.
Caesar Cipher w/ range to ascii table

A true Caesar Cipher would only inlcude the alphabet

ascii table: 127
extended: 255
'''

'''
Powershell Instructions:
"This is a message" > message.txt
cat message.txt | py CaeserCypher.py encrypt UserKey > encrypted.txt
cat encrypted.txt | py CaeserCypher.py decrypt UserKey > decrypted.txt
type decrpted.txt
'''

# include standard modules
import argparse, sys

class CaesarCipher:
    def __init__(self, user_key):
        self.user_key = user_key

    def encrypt(self, user_input):
        buffer_message = ""
        new_message = ""

        for x in range(len(user_input)):
            buffer_message = (ord(user_input[x]) + ord(self.user_key[x % len(self.user_key)]))
            new_message += chr(buffer_message % 127)

        return(new_message)

    def decrypt(self, user_input):
        buffer_message = ""
        new_message = ""

        for x in range(len(user_input)):
            buffer_message = (ord(user_input[x]) - ord(self.user_key[x % len(self.user_key)]))
            new_message += chr(buffer_message % 127)

        return(new_message)

class InvalidConfig(Exception):
    def __init__(self, config_name, config_value):
        Exception.__init__(self, f'The config {config_name} "{config_value}" is invalid')

class Config:
    mode: str
    key: str
    def validate(self):
        if self.mode != "encrypt" and self.mode != "decrypt":
            raise InvalidConfig("mode", self.mode)

        if len(self.key) is 0:
            raise InvalidConfig("key", self.key)

def getConfig():
    parser = argparse.ArgumentParser()
    parser.add_argument("mode", help="Valid modes are 'encrypt' 'decrypt'", type=str)
    parser.add_argument("key", help="Cipher Key", type=str)

    # Read and parse command line arguments
    args = parser.parse_args()

    config = Config()
    config.mode = args.mode
    config.key = args.key

    return config

def getInputData():
    inputData = sys.stdin.readlines()

    inputData = '\n'.join(inputData)

    inputData = inputData.rstrip()

    return inputData

#### Start the app
try:
    config = getConfig()

    config.validate()

    inputData = getInputData()

    # Do cipher
    cipher = CaesarCipher(config.key)

    if config.mode == 'encrypt':
        print(cipher.encrypt(inputData))
    elif config.mode == 'decrypt':
        print(cipher.decrypt(inputData))
    else:
        raise Exception('Invalid Operation')
except InvalidConfig as error:
    parser = argparse.ArgumentParser()
    parser.add_argument("mode", help="Valid modes are 'encrypt' 'decrypt'", type=str)
    parser.add_argument("key", help="Cipher Key", type=str)

    errorString = str(error)

    parser.error(errorString)
except Exception as error:
    traceback.print_tb(error.__traceback__)
    exit(-1)