CipherStreamJava/src/main/java/com/mattrixwv/cipherstream/monosubstitution/Baconian.java

package com.mattrixwv.cipherstream.monosubstitution;


import java.util.ArrayList;
import java.util.Arrays;
import java.util.StringJoiner;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.mattrixwv.cipherstream.exceptions.InvalidCharacterException;
import com.mattrixwv.cipherstream.exceptions.InvalidInputException;


/**
 * Implements the Baconian cipher, a method of steganography where each letter of the alphabet is represented by a unique sequence of five characters ('a' or 'b').
 * The Baconian cipher is a simple substitution cipher that can encode and decode text based on these sequences.
 *
 * <p>
 * The cipher uses a predefined list of five-character strings to represent each letter of the alphabet (A-Z). The input string is converted to these sequences for encoding,
 * and sequences are converted back to letters for decoding.
 * </p>
 */
public final class Baconian{
	private static final Logger logger = LoggerFactory.getLogger(Baconian.class);

	//?Conversions
	/** Predefined code for Baconian cipher (5-character strings for A-Z) */
	protected static final ArrayList<String> code = new ArrayList<>(Arrays.asList(
		"aaaaa", "aaaab", "aaaba", "aaabb", "aabaa", "aabab", "aabba","aabbb", "abaaa", "abaaa", "abaab", "ababa", "ababb",	//A-M
		"abbaa", "abbab", "abbba", "abbbb", "baaaa", "baaab", "baaba", "baabb", "baabb", "babaa", "babab", "babba", "babbb"		//N-Z
	));
	/** The string that needs encoded/decoded */
	protected String inputString;
	/** The encoded/decoded string */
	protected String outputString;
	/** Persist capitals in the output string */
	protected boolean preserveCapitals;


	/**
	 * Sets the input string for encoding, removing whitespace and symbols, and handling capitalization based on the flag.
	 *
	 * @param inputString the string to be encoded
	 * @throws InvalidInputException if the input string is null, empty, or invalid
	 */
	protected void setInputStringEncode(String inputString) throws InvalidInputException{
		if(inputString == null){
			throw new InvalidInputException("Input cannot be null");
		}

		logger.debug("Setting input string for encoding '{}'", inputString);

		//Remove all whitespace and symbols
		inputString = inputString.replaceAll("[^A-Za-z]", "");
		if(!preserveCapitals){
			logger.debug("Removing case");

			inputString = inputString.toLowerCase();
		}

		this.inputString = inputString;

		logger.debug("Cleaned input string '{}'", inputString);

		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	/**
	 * Sets the input string for decoding, ensuring it contains only valid Baconian characters (a's and b's) with a length of 5.
	 *
	 * @param inputString the string to be decoded
	 * @throws InvalidCharacterException if the input string contains invalid Baconian characters
	 * @throws InvalidInputException     if the input string is null or empty
	 */
	protected void setInputStringDecode(String inputString) throws InvalidCharacterException, InvalidInputException{
		if(inputString == null){
			throw new InvalidInputException("Input cannot be null");
		}
		else if(inputString.isBlank()){
			throw new InvalidInputException("Input cannot be empty");
		}

		logger.debug("Setting input string for decoding '{}'", inputString);

		if(!preserveCapitals){
			logger.debug("Removing case");

			inputString = inputString.toLowerCase();
		}

		//Check each Baconian Cipher letter for validity
		logger.debug("Ensuring all 'letters' contain 5 characters");
		for(String str : inputString.split(" ")){
			logger.debug("Current 'letter' {}", str);

			//Make sure each letter contains 5 characters
			if(str.length() != 5){
				throw new InvalidCharacterException("All Baconian 'letters' contain exactly 5 characters. Invalid 'letter': " + str);
			}

			//Make sure the letter contains only a's and b's
			logger.debug("Replacing all non-abAB characters");
			String temp = str.replaceAll("[^abAB]", "");
			if(!temp.equals(str)){
				throw new InvalidCharacterException("Baconian 'letters' contain only a's and b's. Invalid 'letter': " + str);
			}
		}

		this.inputString = inputString;

		logger.debug("Cleaned input string '{}'", inputString);
	}
	/**
	 * Encodes the input string using the Baconian cipher.
	 * Each character in the input string is converted to its corresponding Baconian sequence.
	 */
	protected void encode(){
		logger.debug("Encoding");
		StringJoiner output = new StringJoiner(" ");
		//Go through every character in the inputString and encode it
		for(char ch : inputString.toCharArray()){
			logger.debug("Working character {}", ch);

			//Convert the character to a binary string with A = 0
			String binary = null;
			if(Character.isUpperCase(ch)){
				logger.debug("Encoding uppercase");

				binary = code.get(ch - 'A').toUpperCase();
			}
			else{
				logger.debug("Encoding lowercase");

				binary = code.get(ch - 'a').toLowerCase();
			}

			//Add the encoded character to the output
			logger.debug("Output letter {}", binary);
			output.add(binary);
		}

		//Save and return the output
		outputString = output.toString();
		logger.debug("Saving output string '{}'", outputString);
	}
	/**
	 * Decodes the input string using the Baconian cipher.
	 * Each Baconian sequence in the input string is converted back to its corresponding character.
	 */
	protected void decode(){
		logger.debug("Decoding");

		StringBuilder output = new StringBuilder();
		//Go through every Baconian Cipher character in the inputString and decode it
		for(String baconianCharacter : inputString.split(" ")){
			logger.debug("Working letter {}", baconianCharacter);

			//Get the location of the Baconian character in the array
			int location = code.indexOf(baconianCharacter.toLowerCase());
			logger.debug("Location of letter {}", location);

			//Convert the Baconian character to an ASCII character
			char ch;
			if(Character.isUpperCase(baconianCharacter.charAt(0))){
				logger.debug("Decoding uppercase");

				ch = (char)(location + 'A');
			}
			else{
				logger.debug("Decoding lowercase");

				ch = (char)(location + 'a');
			}

			//Add the decoded character to the output
			logger.debug("Decoded character {}", ch);
			output.append(ch);
		}

		//Save and return the output
		outputString = output.toString();
		logger.debug("Saving output string '{}'", outputString);
	}

	//?Constructor
	/**
	 * Constructs a new {@code Baconian} instance with default settings for preserving capitals.
	 */
	public Baconian(){
		reset();
		preserveCapitals = false;
	}
	/**
	 * Constructs a new {@code Baconian} instance with a specified setting for preserving capitals.
	 *
	 * @param preserveCapitals whether to preserve capital letters in the output
	 */
	public Baconian(boolean preserveCapitals){
		reset();
		this.preserveCapitals = preserveCapitals;
	}

	/**
	 * Encodes the input string using the Baconian cipher.
	 *
	 * @param inputString the string to be encoded
	 * @return the encoded string
	 * @throws InvalidInputException if the input string is invalid
	 */
	public String encode(String inputString) throws InvalidInputException{
		reset();
		setInputStringEncode(inputString);
		encode();
		return outputString;
	}
	/**
	 * Decodes the input string using the Baconian cipher.
	 *
	 * @param inputString the string to be decoded
	 * @return the decoded string
	 * @throws InvalidCharacterException if the input string contains invalid Baconian characters
	 * @throws InvalidInputException     if the input string is invalid
	 */
	public String decode(String inputString) throws InvalidCharacterException, InvalidInputException{
		reset();
		setInputStringDecode(inputString);
		decode();
		return outputString;
	}

	//?Getters
	/**
	 * Gets the current input string.
	 *
	 * @return the input string
	 */
	public String getInputString(){
		return inputString;
	}
	/**
	 * Gets the current output string.
	 *
	 * @return the output string
	 */
	public String getOutputString(){
		return outputString;
	}
	/**
	 * Resets the input and output strings to empty.
	 */
	public void reset(){
		logger.debug("Resetting fields");

		inputString = "";
		outputString = "";
	}
}