Parser

package ie.gmit.dip;

import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;



public class Parser {
	private String[] charPairs = new String[100];
	
	
	public static boolean isValid(String url){
		try {
	           new URL(url).toURI();
	           return true;
	        }
	        catch (Exception e) {
	           return false;
	        }
	}

	public String[] parseEncrypt (String resource, boolean isUrl, char[][] newArrayofArrays) {
		BufferedReader br = null;
		
		
			try {
				if(isUrl) {
					// buffer reader is assigned the value of an openinputstream if its a url
					br = new BufferedReader(new InputStreamReader(new URL(resource).openStream()));
				}else {
					// buffer reader is assigned the value of an fileinputstream if its a file
					br = new BufferedReader(new InputStreamReader(new FileInputStream(resource)));
				
				}
				FileWriter fw = new FileWriter("encrypted.txt");	
				String line = null;
				
				while ((line = br.readLine()) != null){
					// any characters that are not alphanumeric are removed and replaced with "" and all characters are made uppercase to match the matrix array.
					line = line.replaceAll("[^A-Za-z0-9]", "").toUpperCase();
					// to ensure an even length of line an X has been added to the line when the line is uneven.
						if ((line.length() % 2) != 0) {
							line = line + "X";					
						}
					// a string array of pairs of characters is the created from line.
					String[] bigrams = line.split("(?<=\\G.{2})");
					// a new FourSquareCipher object is created
					FourSquareCipher cipher = new FourSquareCipher(newArrayofArrays);
					// the string array bigrams is passed to the encrypt method of the FourSquareCipher class line by line.
					String encryptedtext = cipher.encrypt(bigrams);
					// the encrypted text is then added to the file per line
					fw.write(encryptedtext + "\n");
					
				}
				// the input streams and most importantly the writer streams are closed.
				br.close();
				fw.flush();
				fw.close();		
				
			} catch (MalformedURLException e) {
				System.out.println("an incorrect URL has been encountered, please use a correctly formatted url");
				
			} catch (IOException e) {
				System.out.println("File not found "+ resource +" did you forget the file extension?");
				
			}
						
		return charPairs;
	}
	
	public String[] parseDecrypt (String resource, boolean isUrl, char[][] newArrayofArrays) {
		BufferedReader br = null;
		
		
			try {
				if(isUrl) {
					br = new BufferedReader(new InputStreamReader(new URL(resource).openStream()));
				}else {
					br = new BufferedReader(new InputStreamReader(new FileInputStream(resource)));
				
				}
				FileWriter fw = new FileWriter("decrypted.txt");	
				String line = null;
				
				while ((line = br.readLine()) != null){
					// any characters that are not alphanumeric are removed and replaced with "" and all characters are made uppercase to match matrix.
					line = line.replaceAll("[^A-Za-z0-9]", "").toUpperCase();
					// to ensure an even length of line an X has been added to the line when the line is uneven.
						if ((line.length() % 2) != 0) {
							line = line + "X";					
						}
					// a string array of pairs of characters is the created from line.
					String[] bigrams = line.split("(?<=\\G.{2})");
					
					FourSquareCipher cipher = new FourSquareCipher(newArrayofArrays);
					String encryptedtext = cipher.decrypt(bigrams);
					fw.write(encryptedtext + "\n");
					
				}
				
				br.close();
				fw.flush();
				fw.close();		
				
			} catch (MalformedURLException e) {
				
				e.printStackTrace();
			} catch (IOException e) {
				
				e.printStackTrace();
			}
						
		return charPairs;
	}
	
	
	  public char[] parseKey(String parse){
		  	// passed string is converted to upper case
		    parse = parse.toUpperCase();
		    // anything that is not A-Z in upper case is removed and any j's are replaced with i's
		    parse = parse.replaceAll("[^A-Z]", "").replace("J", "I");;
		    String alphabet =  "ABCDEFGHIKLMNOPQRSTUVWXYZ";
		    // the whole alphabet is added to the end of the parse string
		    String keyword = parse + alphabet;
		    // this keyword is then stripped of any duplicate letters while keeping its original order.
		    keyword = removeDuplicates(keyword);
		    // the stripped down string is then returned as a char[] array.
		    return keyword.toCharArray();
		    
		  }
	  
	  static String removeDuplicates(String s) {
		  // a new stringbuilder is created
		    StringBuilder noDupes = new StringBuilder();
		    // the string is traversed 
		    for (int i = 0; i < s.length(); i++) {
		        String si = s.substring(i, i + 1);
		        // where the substring of one letter is not part of the stringbuilder then append it to the stringbuilder
		        if (noDupes.indexOf(si) == -1) {
		            noDupes.append(si);
		        }
		    }
		    // return the string without duplicates
		    return noDupes.toString();
		}
	
	
	
	/*
	public void addBigrams (String[] s) {
		for (int i = 0; i < s.length; i++) {
			append(s[i]);
		}
		
	}
	
	public void append(String s) {
		// if there is not enough capacity in the char pairs array then the array length is doubled(? this is probably a little bit like napalm for ants in the garden but it'll get the job done) in order to accommodate the new array.
		ensureCapacity();
		// each string in the bigrams string array is then added to the charPairs array.
		charPairs[index] = s;
		//System.out.println(charPairs[index]); - used in testing the code
		index++;
		//System.out.println(index);- used in testing the code

	}
	
	private void ensureCapacity() {
		if (index >= charPairs.length) {
			String[] temp = new String[charPairs.length * 2];
			for (int i = 0; i < charPairs.length; i++) {
				temp[i] = charPairs[i];
			}
			
			charPairs = temp;
		}
	}

	*/
}