package com.mattrixwv.cipherstream.monosubstitution;


import java.util.ArrayList;
import java.util.List;

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 Vigenère cipher.
 * This cipher uses a keyword to determine the shift for each character in the input string.
 *
 * <p>
 * The Vigenère cipher applies a series of Caesar ciphers based on the letters of a keyword.
 * The keyword determines the shift for each letter in the input string.
 * </p>
 */
public class Vigenere{
	private static final Logger logger = LoggerFactory.getLogger(Vigenere.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 resposible for determining the offsets that you change each character by */
	protected String keyword;
	/** Holds the offsets coputed from each character in the keyword */
	protected ArrayList<Integer> offset;
	//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;


	/**
	 * Calculates the offsets for the Vigenère cipher from the keyword.
	 */
	protected void setOffset(){
		logger.debug("Setting offset array from keyword");

		//Reserve the correct size to increase speed later
		offset.ensureCapacity(keyword.length());

		//Loop through every letter in keyword and get the offset from A
		for(int cnt = 0;cnt < keyword.length();++cnt){
			char letter = keyword.charAt(cnt);
			offset.add((letter - 'A') % 26);
		}

		logger.debug("Offset {}", offset);
	}
	/**
	 * Sets the input string and applies transformation settings.
	 *
	 * @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{
		if(inputString == null){
			throw new InvalidInputException("Input cannot be null");
		}

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

		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]", "");
		}

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

		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	/**
	 * Sets the keyword for the Vigenère cipher and computes the offsets.
	 *
	 * @param keyword the keyword to be used for encoding/decoding
	 * @throws InvalidKeywordException if the keyword is null, too short, or contains invalid characters
	 */
	protected void setKeyword(String keyword) throws InvalidKeywordException{
		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-letter characters");
		keyword = keyword.replaceAll("[^A-Z]", "");

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

		//Make sure offset is empty before adding to it
		offset.clear();
		setOffset();

		//If after all the eliminating of unusable characters the keyword is empty throw an exception
		if(this.keyword.length() < 2){
			throw new InvalidKeywordException("Keyword must contain at least 2 letters");
		}
	}
	/**
	 * Encodes the input string using the Vigenère cipher and stores the result.
	 */
	protected void encode(){
		logger.debug("Encoding");

		StringBuilder output = new StringBuilder();

		//Step through every character in the inputString and advance it the correct amount, according to offset
		int offsetCnt = 0;
		for(int inputCnt = 0;inputCnt < inputString.length();++inputCnt){
			char letter = inputString.charAt(inputCnt);
			logger.debug("Working character {}", letter);

			if(Character.isUpperCase(letter)){
				logger.debug("Encoding uppercase");

				letter += offset.get((offsetCnt++) % offset.size());

				//Make sure the character is still a letter, if not, wrap around
				if(letter > 'Z'){
					logger.debug("Wrapping around to A");

					letter -= 26;
				}
			}
			else if(Character.isLowerCase(letter)){
				logger.debug("Encoding lowercase");

				letter += offset.get((offsetCnt++) % offset.size());

				//Make sure the character is still a letter, if not, wrap around
				if(letter > 'z'){
					logger.debug("Wrapping around to a");

					letter -= 26;
				}
			}

			logger.debug("Encoded character {}", letter);
			output.append(letter);
		}

		//Save output
		outputString = output.toString();
		logger.debug("Encoded message '{}'", outputString);
	}
	/**
	 * Decodes the input string using the Vigenère cipher and stores the result.
	 */
	protected void decode(){
		logger.debug("Decoding");

		StringBuilder output = new StringBuilder();

		//Step through every character in the inputString and advance it the correct amount, according to offset
		int offsetCnt = 0;
		for(int letterCnt = 0;letterCnt < inputString.length();++letterCnt){
			char letter = inputString.charAt(letterCnt);

			logger.debug("Working character {}", letter);

			if(Character.isUpperCase(letter)){
				logger.debug("Decoding uppercase");

				letter -= offset.get((offsetCnt++) % offset.size());

				if(letter < 'A'){
					logger.debug("Wrapping around to Z");

					letter += 26;
				}
			}
			else if(Character.isLowerCase(letter)){
				logger.debug("Decoding lowercase");

				letter -= offset.get((offsetCnt++) % offset.size());

				if(letter < 'a'){
					logger.debug("Wrapping around to z");

					letter += 26;
				}
			}

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

		//Save output
		outputString = output.toString();
		logger.debug("Decoded message '{}'", outputString);
	}


	//?Constructor
	/**
	 * Constructs a new {@code Vigenere} instance with default settings.
	 */
	public Vigenere(){
		offset = new ArrayList<>();
		inputString = "";
		outputString = "";
		keyword = "";
		offset.clear();
		preserveCapitals = false;
		preserveWhitespace = false;
		preserveSymbols = false;
	}
	/**
	 * Constructs a new {@code Vigenere} 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 Vigenere(boolean preserveCapitals, boolean preserveWhitespace, boolean preserveSymbols){
		offset = new ArrayList<>();
		inputString = "";
		outputString = "";
		keyword = "";
		offset.clear();
		this.preserveCapitals = preserveCapitals;
		this.preserveWhitespace = preserveWhitespace;
		this.preserveSymbols = preserveSymbols;
	}

	/**
	 * Encodes the input string using the provided keyword.
	 *
	 * @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{
		reset();
		setKeyword(keyword);
		setInputString(inputString);
		encode();
		return outputString;
	}
	/**
	 * Decodes the input string using the provided keyword.
	 *
	 * @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{
		reset();
		setKeyword(keyword);
		setInputString(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;
	}
	/**
	 * Gets the current keyword.
	 *
	 * @return the keyword
	 */
	public String getKeyword(){
		return keyword;
	}
	/**
	 * Gets the current offset list.
	 *
	 * @return the offset list
	 */
	public List<Integer> getOffsets(){
		return offset;
	}
	/**
	 * Resets all fields to their default values.
	 */
	public void reset(){
		logger.debug("Resetting fields");

		inputString = "";
		outputString = "";
		keyword = "";
		offset.clear();
	}
}