//CipherStreamJava/src/main/java/com/mattrixwv/cipherstream/monosubstitution/BaseX.java
//Mattrixwv
// Created: 01-08-22
//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 java.util.StringJoiner;

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

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


/**
 * A class for encoding and decoding strings using a specified numerical base.
 * The BaseX class allows encoding and decoding of strings where characters are represented in a given base.
 * The base can be set to any value between Character.MIN_RADIX and Character.MAX_RADIX.
 *
 * <p>
 * This class supports encoding and decoding of ASCII characters into their base-X representations,
 * where X is the base provided by the user. It ensures that input strings are valid and within the acceptable range
 * for the specified base.
 * </p>
 */
public class BaseX{
	private static final Logger logger = LoggerFactory.getLogger(BaseX.class);
	//?Fields
	/** The string that needs encoded/decoded */
	protected String inputString;
	/** The encoded/decoded string */
	protected String outputString;
	//?Settings
	/** The base that the number will be encoded at */
	protected int base;


	/**
	 * Sets the input string for encoding, ensuring it is not null and contains at least one letter.
	 *
	 * @param inputString the string to be encoded
	 * @throws InvalidInputException if the input string is null or blank
	 */
	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);

		this.inputString = inputString;

		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	/**
	 * Sets the input string for decoding, ensuring it is not null, does not contain invalid characters, and is properly formatted.
	 *
	 * @param inputString the string to be decoded
	 * @throws InvalidCharacterException if the input string contains invalid characters
	 * @throws InvalidInputException     if the input string is null or blank
	 */
	protected void setInputStringDecode(String inputString) throws InvalidCharacterException, InvalidInputException{
		if(inputString == null){
			throw new InvalidInputException("Input cannot be null");
		}

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

		//Create a string of valid 'numbers'
		logger.debug("Creating string of valid 'numbers'");
		StringBuilder validNumbers = new StringBuilder();
		for(int cnt = 0;cnt < base;++cnt){
			String number = Integer.toString(cnt, base).toUpperCase();
			logger.debug("Current number {}, converted {}", cnt, number);
			validNumbers.append(number);
		}

		//Remove all invalid characters
		logger.debug("Checking for invalid characters");
		this.inputString = inputString.replaceAll("[^" + validNumbers.toString() + "\\s]", "");
		//Throw an exception if there were any invalid characters
		if(!this.inputString.equals(inputString)){
			throw new InvalidCharacterException("inputString cannot contain anything except numbers 0-" + Integer.toString(base - 1, base) + ", and whitespace");
		}

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

		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	/**
	 * Sets the base for encoding and decoding, ensuring it is within valid range.
	 *
	 * @param base the base to be set
	 * @throws InvalidBaseException if the base is less than Character.MIN_RADIX or greater than Character.MAX_RADIX
	 */
	protected void setBase(int base) throws InvalidBaseException{
		if(base < Character.MIN_RADIX){
			throw new InvalidBaseException("Base cannot be less than " + Character.MIN_RADIX);
		}
		else if(base > Character.MAX_RADIX){
			throw new InvalidBaseException("Base cannot be larger than " + Character.MAX_RADIX);
		}

		logger.debug("Setting base {}", base);

		this.base = base;
	}
	/**
	 * Encodes the input string using the specified base.
	 */
	protected void encode(){
		logger.debug("Encoding");

		//Encode every character in inputString
		StringJoiner output = new StringJoiner(" ");
		for(int cnt = 0;cnt < inputString.length();++cnt){
			//Get the next character
			char ch = inputString.charAt(cnt);
			logger.debug("Working number {}", ch);

			//Encode the character to binary and add it to the output
			String convertedNum = Integer.toString(ch, base);
			output.add(convertedNum);
			logger.debug("Converted number {}", convertedNum);
		}

		//Save the output
		outputString = output.toString().toUpperCase();
		logger.debug("Saving output string '{}'", outputString);
	}
	/**
	 * Decodes the input string from the specified base.
	 *
	 * @throws InvalidCharacterException if the input string contains invalid characters for the base
	 */
	protected void decode() throws InvalidCharacterException{
		logger.debug("Decoding");

		//Decode every binary number in the string
		StringBuilder output = new StringBuilder();
		for(String baseXString : inputString.split(" ")){
			logger.debug("Current number {}", baseXString);

			//Decode the current binary number
			int num = Integer.valueOf(baseXString, base);
			logger.debug("Decoded number {}", num);

			//Make sure it is in a valid range
			if((num < 0) || (num > 255)){
				throw new InvalidCharacterException("The base" + base + " string '" + baseXString + "' is not a valid ASCII character");
			}

			//Convert the int to a char and save it
			output.append((char)num);
		}

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

	//?Constructor
	/**
	 * Constructs a new {@code BaseX} instance with the default base of 2.
	 *
	 * @throws InvalidBaseException if the default base is invalid
	 */
	public BaseX() throws InvalidBaseException{
		reset();
		setBase(2);
	}
	/**
	 * Constructs a new {@code BaseX} instance with the specified base.
	 *
	 * @param base the base to be used for encoding and decoding
	 * @throws InvalidBaseException if the base is invalid
	 */
	public BaseX(int base) throws InvalidBaseException{
		reset();
		setBase(base);
	}

	/**
	 * Encodes the given input string using the current base.
	 *
	 * @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;
	}
	/**
	 * Encodes the given input string using the specified base.
	 *
	 * @param base        the base to use for encoding
	 * @param inputString the string to be encoded
	 * @return the encoded string
	 * @throws InvalidBaseException if the base is invalid
	 * @throws InvalidInputException if the input string is invalid
	 */
	public String encode(int base, String inputString) throws InvalidBaseException, InvalidInputException{
		reset();
		setBase(base);
		setInputStringEncode(inputString);
		encode();
		return outputString;
	}
	/**
	 * Decodes the given input string using the current base.
	 *
	 * @param inputString the string to be decoded
	 * @return the decoded string
	 * @throws InvalidCharacterException if the input string contains invalid characters
	 * @throws InvalidInputException     if the input string is invalid
	 */
	public String decode(String inputString) throws InvalidCharacterException, InvalidInputException{
		reset();
		setInputStringDecode(inputString);
		decode();
		return outputString;
	}
	/**
	 * Decodes the given input string using the specified base.
	 *
	 * @param base        the base to use for decoding
	 * @param inputString the string to be decoded
	 * @return the decoded string
	 * @throws InvalidBaseException     if the base is invalid
	 * @throws InvalidCharacterException if the input string contains invalid characters
	 * @throws InvalidInputException     if the input string is invalid
	 */
	public String decode(int base, String inputString) throws InvalidBaseException, InvalidCharacterException, InvalidInputException{
		reset();
		setBase(base);
		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;
	}
	/**
	 * Gets the current base.
	 *
	 * @return the base
	 */
	public int getBase(){
		return base;
	}
	/**
	 * Resets the input and output strings to empty.
	 */
	public void reset(){
		logger.debug("Resetting fields");

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