//CipherStreamJava/src/main/java/com/mattrixwv/cipherstream/monosubstitution/Beaufort.java
//Mattrixwv
// Created: 02-23-22
//Modified: 08-11-24
/*
	Copyright (C) 2024  Mattrixwv

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
package com.mattrixwv.cipherstream.monosubstitution;


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

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


/**
 * A class for encoding and decoding strings using the Beaufort cipher,
 * which is a variant of the Vigenère cipher with additional steps.
 *
 * <p>
 * The Beaufort cipher consists of three main steps:
 * </p>
 * <ul>
 *   <li>Atbash cipher for reversing the string</li>
 *   <li>Caesar cipher for shifting characters by a fixed amount</li>
 *   <li>Vigenère cipher for applying a keyword-based shift</li>
 * </ul>
 * This class allows you to encode and decode strings with options to preserve
 * capitalization, whitespace, and symbols.
 */
public class Beaufort{
	private static final Logger logger = LoggerFactory.getLogger(Beaufort.class);
	//?Fields
	/** This is the string that needs encoded/decoded */
	protected String inputString;
	/** This is the string that is output after encoding/decoding */
	protected String outputString;
	/** This is the keyword that is responsible for determining the offsets that you change each character by */
	protected String keyword;
	//?Settings
	/** Persist capitals in the output string */
	protected boolean preserveCapitals;
	/** Persist whitespace in the output string */
	protected boolean preserveWhitespace;
	/** Persist symbols in the output string */
	protected boolean preserveSymbols;
	//?Internal ciphers
	/** The first step in encoding/decoding the cipher */
	protected Atbash atbash;
	/** The second step in encoding/decoding the cipher */
	protected Caesar caesar;
	/** The third step in encoding/decoding the cipher */
	protected Vigenere vigenere;


	/**
	 * Sets the input string for encoding or decoding, applying removal options
	 * for case, whitespace, and symbols.
	 *
	 * @param inputString the string to be processed
	 * @throws InvalidInputException if the input string is null or blank after processing
	 */
	public void setInputString(String inputString) throws InvalidInputException{
		//Make sure the input isn't null
		if(inputString == null){
			throw new InvalidInputException("Input cannot be null");
		}

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

		//Apply removal options
		if(!preserveCapitals){
			logger.debug("Removing case");

			inputString = inputString.toUpperCase();
		}
		if(!preserveWhitespace){
			logger.debug("Removing whitespace");

			inputString = inputString.replaceAll("\\s", "");
		}
		if(!preserveSymbols){
			logger.debug("Removing symbols");

			inputString = inputString.replaceAll("[^a-zA-Z\\s]", "");
		}

		//Save the string
		logger.debug("Cleaned input string '{}'", inputString);
		this.inputString = inputString;

		//Make sure the string isn't blank
		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	/**
	 * Sets the keyword for encoding or decoding, ensuring it contains only
	 * uppercase letters and is at least 2 letters long.
	 *
	 * @param keyword the keyword for the Vigenère cipher
	 * @throws InvalidKeywordException if the keyword is null, blank, or less than 2 letters
	 */
	public void setKeyword(String keyword) throws InvalidKeywordException{
		//Make sure the keyword isn't null
		if(keyword == null){
			throw new InvalidKeywordException("Keyword cannot be null");
		}

		logger.debug("Original keyword '{}'", keyword);

		//Convert all letters to uppercase
		logger.debug("Removing case");
		keyword = keyword.toUpperCase();
		//Remove all characters except capital letters
		logger.debug("Removing all non-letters");
		keyword = keyword.replaceAll("[^A-Z]", "");

		//Save the string
		logger.debug("Cleaned keyword '{}'", keyword);
		this.keyword = keyword;

		//If after all the elimination of unusable characters the keyword is empty throw an exception
		if(this.keyword.isBlank() || (this.keyword.length() < 2)){
			throw new InvalidKeywordException("Keyword must contain at least 2 letters");
		}
	}
	/**
	 * Encodes the input string using the Beaufort cipher and stores the result in {@code outputString}.
	 *
	 * @throws InvalidKeywordException if the keyword is invalid
	 * @throws InvalidInputException    if the input string is invalid
	 */
	protected void encode() throws InvalidKeywordException, InvalidInputException{
		logger.debug("Encoding");

		code();
	}
	/**
	 * Decodes the input string using the Beaufort cipher and stores the result in {@code outputString}.
	 * Decoding is the same process as encoding in this cipher.
	 *
	 * @throws InvalidKeywordException if the keyword is invalid
	 * @throws InvalidInputException    if the input string is invalid
	 */
	protected void decode() throws InvalidKeywordException, InvalidInputException{
		logger.debug("Decoding");

		//Decoding is just encoding again
		code();
	}
	/**
	 * Performs the Beaufort cipher encoding/decoding process:
	 * <ul>
	 *   <li>Encodes the input string using the Atbash cipher</li>
	 *   <li>Shifts the result by 1 using the Caesar cipher</li>
	 *   <li>Applies the Vigenère cipher using the keyword</li>
	 * </ul>
	 */
	protected void code(){
		//Reverse the string
		logger.debug("Encoding with Atbash");
		String atbashString = atbash.encode(inputString);
		//Shift the reversal by 1
		//?Not quite sure why this is needed. Need to look into this cipher a bit more closely
		logger.debug("Shifting all letters by 1");
		String caesarString = caesar.encode(1, atbashString);
		//Shift each letter according to the key
		logger.debug("Encoding with Vigenere");
		String vigenereString = vigenere.encode(keyword, caesarString);

		//Save the output
		logger.debug("Saving output string '{}'", vigenereString);
		this.outputString = vigenereString;
	}


	//?Constructor
	/**
	 * Constructs a new {@code Beaufort} instance with default settings.
	 */
	public Beaufort(){
		preserveCapitals = false;
		preserveWhitespace = false;
		preserveSymbols = false;
		atbash = new Atbash(false, false, false);
		caesar = new Caesar(false, false, false);
		vigenere = new Vigenere(false, false, false);
		reset();
	}
	/**
	 * Constructs a new {@code Beaufort} instance with specified settings.
	 *
	 * @param preserveCapitals   whether to preserve capitalization in the output
	 * @param preserveWhitespace whether to preserve whitespace in the output
	 * @param preserveSymbols    whether to preserve symbols in the output
	 */
	public Beaufort(boolean preserveCapitals, boolean preserveWhitespace, boolean preserveSymbols){
		this.preserveCapitals = preserveCapitals;
		this.preserveWhitespace = preserveWhitespace;
		this.preserveSymbols = preserveSymbols;
		atbash = new Atbash(preserveCapitals, preserveWhitespace, preserveSymbols);
		caesar = new Caesar(preserveCapitals, preserveWhitespace, preserveSymbols);
		vigenere = new Vigenere(preserveCapitals, preserveWhitespace, preserveSymbols);
		reset();
	}

	 /**
	 * Encodes the input string using the specified keyword.
	 *
	 * @param keyword     the keyword for the Vigenère cipher
	 * @param inputString the string to be encoded
	 * @return the encoded string
	 * @throws InvalidKeywordException if the keyword is invalid
	 * @throws InvalidInputException    if the input string is invalid
	 */
	public String encode(String keyword, String inputString) throws InvalidKeywordException, InvalidInputException{
		//Set the parameters
		setKeyword(keyword);
		setInputString(inputString);

		//Encode and return the message
		encode();
		return outputString;
	}
	/**
	 * Decodes the input string using the specified keyword.
	 *
	 * @param keyword     the keyword for the Vigenère cipher
	 * @param inputString the string to be decoded
	 * @return the decoded string
	 * @throws InvalidKeywordException if the keyword is invalid
	 * @throws InvalidInputException    if the input string is invalid
	 */
	public String decode(String keyword, String inputString) throws InvalidKeywordException, InvalidInputException{
		//Set the parameters
		setKeyword(keyword);
		setInputString(inputString);

		//Decode and return the message
		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;
	}
	/**
	 * Gets the current keyword.
	 *
	 * @return the keyword
	 */
	public String getKeyword(){
		return keyword;
	}
	/**
	 * Resets the input string, output string, and keyword to empty.
	 */
	public void reset(){
		logger.debug("Resetting fields");

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