Message Encoder/Decoder

---

This Python script allows to encode or decode messages using a keyword-based cipher. It provides a command-line interface for user interaction.

Features:

Encoding and Decoding: Choose between encoding and decoding a message.

Keyword Input: Enter a keyword to modify the encoding pattern.

Interactive Interface: Continuously prompts the user for new messages until they choose to exit.

Human-like Interaction: Uses time delays to simulate a more natural interaction flow.

To run this program, users will need a Python-friendly environment.

---

This script has gone through several development stages and has been continuously modified throughout my programming journey. The latest version is optimized with best practices including maintainability, reusability, and DRY (Don't Repeat Yourself).

What used to be multiple repeating funtions is now two organized process_message and get_keyword_string functions:

process_message:

def process_message(type, process):
    message_to_process = get_message()
    keyword = get_keyword()
    
    print("\n", process)
    time.sleep(1)

    # get keyword string
    keyword_string = get_keyword_string(message_to_process, keyword)  

    # initialize resultant message string
    resultant_message = ''
    # loop through message to process
    for i, char in enumerate(message_to_process):
        # if current character is alphabetic
        if char.isalpha():
            # get corresponding alphabetic reference index
            message_index = reference.index(char)
            # get corresponding alphabetic reference keyword index
            keyword_string_index = reference.index(keyword_string[i]) 
            # shift message letter by keyword letter, wrap around the alphabet
            if type == '+':
                result_index = (message_index + keyword_string_index) % 26
            elif type == '-':
                result_index = (message_index - keyword_string_index) % 26
            # add character to encoded message string
            resultant_message += reference[result_index]
        # else add current character to decoded message
        else:
            resultant_message += char

get_keyword_string:

def get_keyword_string(message, keyword):
    #initialize keyword string and index
    keyword_string = ''
    keyword_index = 0
    # loop through message to decode
    for char in message:
        # if current character is alphabetic
        if char.isalpha():
            # add to keyword string
            keyword_string += keyword[keyword_index]
            # increment keyword index
            keyword_index = (keyword_index + 1) % len(keyword)  
        # else add curent character to keyword string 
        else:
            keyword_string += char
    
    return keyword_string