//CipherStreamJava/src/main/java/com/mattrixwv/CipherStreamJava/monoSubstitution/Caesar.java
//Matthew Ellison
// Created: 07-25-21
//Modified: 02-17-22
package com.mattrixwv.cipherstream.monosubstitution;


import com.mattrixwv.cipherstream.exceptions.InvalidInputException;


public class Caesar{
	private String inputString;		//The string that needs encoded/decoded
	private String outputString;	//The encoded/decoded string
	private int shift;	//The amount that you need to shift each letter
	private boolean preserveCapitals;	//Whether to respect capitals in the output string
	private boolean preserveWhitespace;	//Whether to respect whitespace in the output string
	private boolean preserveSymbols;	//Whether to respect symbols in the output string
	//Sets shift and makes sure it is within the propper bounds
	private void setShift(int shiftAmount){
		//If you shift more than 26 you will just be wrapping back around again
		shift = shiftAmount % 26;
	}
	//Sets the input string
	private void setInputString(String inputString) throws InvalidInputException{
		if(inputString == null){
			throw new NullPointerException("Input cannot be null");
		}

		if(!preserveCapitals){
			inputString = inputString.toLowerCase();
		}
		if(!preserveWhitespace){
			inputString = inputString.replaceAll("\\s", "");
		}
		if(!preserveSymbols){
			inputString = inputString.replaceAll("[^a-zA-Z\\s]", "");
		}

		this.inputString = inputString;

		if(this.inputString.isBlank()){
			throw new InvalidInputException("Input must contain at least 1 letter");
		}
	}
	//Encodes the inputString and stores the result in outputString
	private String encode(){
		StringBuilder output = new StringBuilder();
		for(int cnt = 0;cnt < inputString.length();++cnt){
			char currentChar = inputString.charAt(cnt);	//A temperary holder for the current working character
			//If it is an upper case letter shift it and wrap if necessary
			if(Character.isUpperCase(currentChar)){
				currentChar += shift;
				//Wrap around if the letter is now out of bounds
				if(currentChar < 'A'){
					currentChar += 26;
				}
				else if(currentChar > 'Z'){
					currentChar -= 26;
				}
			}
			//If it is a lower case letter shift it and wrap if necessary
			else if(Character.isLowerCase(currentChar)){
				currentChar += shift;
				//Wrap around if the letter is now out of bounds
				if(currentChar < 'a'){
					currentChar += 26;
				}
				else if(currentChar > 'z'){
					currentChar -= 26;
				}
			}
			//If it is whitespace, number, or punctuation just let it pass through
			//Add it to the output string
			output.append(currentChar);
		}

		outputString = output.toString();
		return outputString;
	}
	//Decodes the inputString and stores the result in outputString
	private String decode(){
		StringBuilder output = new StringBuilder();
		for(int cnt = 0;cnt < inputString.length();++cnt){
			char currentChar = inputString.charAt(cnt);	//A temperary holder for the current working character
			//If it is an upper case letter shift it and wrap if necessary
			if(Character.isUpperCase(currentChar)){
				currentChar -= shift;
				//Wrap around if the letter is now out of bounds
				if(currentChar < 'A'){
					currentChar += 26;
				}
				else if(currentChar > 'Z'){
					currentChar -= 26;
				}
			}
			//If it is a lower case letter shift it and wrap if necessary
			else if(Character.isLowerCase(currentChar)){
				currentChar -= shift;
				//Wrap around if the letter is now out of bounds
				if(currentChar < 'a'){
					currentChar += 26;
				}
				else if(currentChar > 'z'){
					currentChar -= 26;
				}
			}
			//If it is whitespace, number, or punctuation just let it pass through
			//Add it to the output string
			output.append(currentChar);
		}

		outputString = output.toString();
		return outputString;
	}

	//Constructor
	public Caesar(){
		reset();
		preserveCapitals = false;
		preserveWhitespace = false;
		preserveSymbols = false;
	}
	public Caesar(boolean preserveCapitals, boolean preserveWhitespace, boolean preserveSymbols){
		reset();
		this.preserveCapitals = preserveCapitals;
		this.preserveWhitespace = preserveWhitespace;
		this.preserveSymbols = preserveSymbols;
	}
	//Returns the inputString
	public String getInputString(){
		return inputString;
	}
	//Returns shift
	public int getShift(){
		return shift;
	}
	//Returns the outputString
	public String getOutputString(){
		return outputString;
	}
	//Sets the shift and inputString and encodes the message
	public String encode(int shiftAmount, String inputString) throws InvalidInputException{
		reset();
		setShift(shiftAmount);
		setInputString(inputString);
		return encode();
	}
	//Sets the shift and inputString and decodes the message
	public String decode(int shiftAmount, String inputString) throws InvalidInputException{
		reset();
		setShift(shiftAmount);
		setInputString(inputString);
		return decode();
	}
	//Makes sure all of the variables are empty
	public void reset(){
		inputString = outputString = "";
		shift = 0;
	}
}