//CipherStreamJava/src/main/java/com/mattrixwv/cipherstream/monosubstitution/Porta.java
//Mattrixwv
// Created: 02-28-22
//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 Porta cipher,
 * which is a variant of the Vigenère cipher that uses a tableau of
 * alphabets to encode and decode messages.
 *
 * <p>
 * The Porta cipher uses a series of Caesar ciphers based on a repeating
 * keyword, with a pre-defined set of alphabetic shifts. This implementation
 * allows for encoding and decoding of messages while preserving or removing
 * certain characters based on configuration settings.
 * </p>
 */
public class Porta{
	private static final Logger logger = LoggerFactory.getLogger(Porta.class);

	/** Predefined alphabetic tableau used for encoding and decoding */
	private static final String[] tableau = {
		"NOPQRSTUVWXYZABCDEFGHIJKLM",	//A-B
		"OPQRSTUVWXYZNMABCDEFGHIJKL",	//C-D
		"PQRSTUVWXYZNOLMABCDEFGHIJK",	//E-F
		"QRSTUVWXYZNOPKLMABCDEFGHIJ",	//G-H
		"RSTUVWXYZNOPQJKLMABCDEFGHI",	//I-J
		"STUVWXYZNOPQRIJKLMABCDEFGH",	//K-L
		"TUVWXYZNOPQRSHIJKLMABCDEFG",	//M-N
		"UVWXYZNOPQRSTGHIJKLMABCDEF",	//O-P
		"VWXYZNOPQRSTUFGHIJKLMABCDE",	//Q-R
		"WXYZNOPQRSTUVEFGHIJKLMABCD",	//S-T
		"XYZNOPQRSTUVWDEFGHIJKLMABC",	//U-V
		"YZNOPQRSTUVWXCDEFGHIJKLMAB",	//W-X
		"ZNOPQRSTUVWXYBCDEFGHIJKLMA"	//Y-Z
	};

	//?Fields
	/** The string that needs encoded/decoded */
	protected String inputString;
	/** The encoded/decoded string */
	protected String outputString;
	/** The keyword used to encode the input string */
	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;


	/**
	 * Ensures all keyword constraints are followed.
	 *
	 * @param keyword the keyword to be used for encoding/decoding
	 * @throws InvalidKeywordException if the keyword is null, empty, or less than 2 characters
	 */
	protected 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 and save the string
		logger.debug("Removing all non-letters");
		keyword = keyword.replaceAll("[^A-Z]", "");

		//Save the keyword
		this.keyword = keyword;

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

		//If after eliminating all ususable 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");
		}
	}
	/**
	 * Ensures all input constraints are followed.
	 *
	 * @param inputString the string to be encoded/decoded
	 * @throws InvalidInputException if the input string is null or blank
	 */
	protected void setInputString(String inputString) throws InvalidInputException{
		//Ensure 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;

		//Ensure the string isn't blank
		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	/**
	 * Returns the letter that replaces the passed-in letter based on the keyword and tableau.
	 *
	 * @param keywordCnt the index of the keyword character to use
	 * @param letter     the letter to be replaced
	 * @return the replacement letter
	 */
	protected char getReplacer(int keywordCnt, char letter){
		logger.debug("Getting letter that replaces {} at {}", letter, keywordCnt);

		char keyLetter = keyword.charAt(keywordCnt % keyword.length());
		int tableauColumn = (Character.toUpperCase(letter) - 'A');

		char replacer;
		switch(keyLetter){
			case 'A', 'B' -> replacer = tableau[0].charAt(tableauColumn);
			case 'C', 'D' -> replacer = tableau[1].charAt(tableauColumn);
			case 'E', 'F' -> replacer = tableau[2].charAt(tableauColumn);
			case 'G', 'H' -> replacer = tableau[3].charAt(tableauColumn);
			case 'I', 'J' -> replacer = tableau[4].charAt(tableauColumn);
			case 'K', 'L' -> replacer = tableau[5].charAt(tableauColumn);
			case 'M', 'N' -> replacer = tableau[6].charAt(tableauColumn);
			case 'O', 'P' -> replacer = tableau[7].charAt(tableauColumn);
			case 'Q', 'R' -> replacer = tableau[8].charAt(tableauColumn);
			case 'S', 'T' -> replacer = tableau[9].charAt(tableauColumn);
			case 'U', 'V' -> replacer = tableau[10].charAt(tableauColumn);
			case 'W', 'X' -> replacer = tableau[11].charAt(tableauColumn);
			case 'Y', 'Z' -> replacer = tableau[12].charAt(tableauColumn);
			default -> replacer = letter;
		}

		logger.debug("Replacer {}", replacer);
		return replacer;
	}
	/**
	 * Encodes the inputString and stores the result in outputString.
	 * Encoding is the same as decoding for this cipher.
	 */
	protected void encode(){
		logger.debug("Encoding");

		//Encoding is the same as decoding
		code();
	}
	/**
	 * Decodes the inputString and stores the result in outputString.
	 * Decoding is the same as encoding for this cipher.
	 */
	protected void decode(){
		logger.debug("Decoding");

		//Decoding is the same as encoding
		code();
	}
	/**
	 * Encodes or decodes the inputString based on the provided keyword.
	 * Uses the tableau to replace characters.
	 */
	protected void code(){
		StringBuilder output = new StringBuilder();

		//Step through every character in the inputString and advance it the correct amount according to the keyword and tableau
		int keywordCnt = 0;
		for(char letter : inputString.toCharArray()){
			logger.debug("Working character {}", letter);
			//If the character is a letter replace with the corresponding character from the tableau
			if(Character.isUpperCase(letter)){
				logger.debug("Encoding uppercase");
				letter = Character.toUpperCase(getReplacer(keywordCnt, letter));
				++keywordCnt;
			}
			else if(Character.isLowerCase(letter)){
				logger.debug("Encoding lowercase");
				letter = Character.toLowerCase(getReplacer(keywordCnt, letter));
				++keywordCnt;
			}

			//Add the current character to the output
			logger.debug("Encoded letter {}", letter);
			output.append(letter);
		}

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


	//?Constructor
	/**
	 * Constructs a new {@code Porta} instance with default settings.
	 */
	public Porta(){
		preserveCapitals = false;
		preserveWhitespace = false;
		preserveSymbols = false;
		reset();
	}
	/**
	 * Constructs a new {@code Porta} 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 Porta(boolean preserveCapitals, boolean preserveWhitespace, boolean preserveSymbols){
		this.preserveCapitals = preserveCapitals;
		this.preserveWhitespace = preserveWhitespace;
		this.preserveSymbols = preserveSymbols;
		reset();
	}

	/**
	 * Sets the keyword and inputString and encodes the message.
	 *
	 * @param keyword   the keyword to use for encoding
	 * @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
		reset();
		setKeyword(keyword);
		setInputString(inputString);

		//Encode and return the message
		encode();
		return outputString;
	}
	/**
	 * Sets the keyword and inputString and decodes the message.
	 *
	 * @param keyword   the keyword to use for decoding
	 * @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
		reset();
		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 all fields to their default values.
	 */
	public void reset(){
		logger.debug("Resetting fields");

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