package org.jdamico.jrfc.cipher;
 
public class RailFenceCipher {
 
	public String encrypt(String plainText, int key){
		int plainTextLength = plainText.length();
 
		while (plainTextLength % key != 0) {
			plainText = plainText + " ";
			plainTextLength++;
		}
 
		int idx = plainTextLength / key;
		int counterPart = 0;
 
		String[] part = new String[idx];
 
		for (int i = 0; i < plainText.length(); i = i + key) {
			part[counterPart] = plainText.substring(i, i + key);
			counterPart++;
		}
 
		StringBuffer enc = new StringBuffer();
 
		for (int k = 0; k < key; k++) {
 
			int step = key;
			if(step % 2 !=0){
				if (k % 2 == 0)	step++;
				else step--;
			}
			for (int l = k; l < idx; l = l + step) enc.append(part[l]);
 
		}
		return enc.toString();
	}
 
	public String decrypt(String cipheredText, int key){
 
		int idx = cipheredText.length() / key;
		int counterPart = 0;
		String[] decPos = new String[idx];
		String[] part = new String[idx];
 
		for (int i = 0; i < cipheredText.length(); i = i + key) {
			part[counterPart] = cipheredText.substring(i, i + key);
			counterPart++;
		}
 
		StringBuffer dec = new StringBuffer();
 
		String spos = " ";
		int encCounter = 0;
		for (int k = 0; k < key; k++) {
 
			int step = key;
			if(step % 2 !=0){
				if (k % 2 == 0) step++;
				else step--;
			}
			for (int l = k; l < idx; l = l + step) {
				spos = spos + l + "(" + encCounter + ") ";
				decPos[l] = part[encCounter];
				encCounter++;
			}
			spos = " ";
		}
 
		for (int y = 0; y < idx; y++) dec.append(decPos[y]);
 
		return dec.toString();
	}
}