/**
 * **************************************************************
 * This program is responsible for simple encryption using RSA.
 * It uses pre-existing keys of a short length.  It is designed
 * to be modular, for possible later additions of other 
 * algorithms, multiple pairs of plain- and ciphertexts, and
 * decryption/cryptanalysis within this main.
 *
 * *******************
 * File: encryption.java
 * Associated classes:
 *   Text
 *   RSA
 *   AttackRSA
 *   Key
 *   Prime
 * $id
 * ************************************************************
 */

import java.lang.*;
import java.io.*;

/**
 * This is the primary class that is the center of whatever encryption, 
 * decryption, or cryptanalysis activities are present.
 */
public class Encryption {
	
	public static boolean debug = false; // true to see all the substeps
	public static boolean stillValid = true; // if false, proceed to exit
	public static StringBuffer userInput = new StringBuffer();
	public static int userSelection = 5;
	public static short badSelections = 0;
	public static Text currentCase = new Text();
	public static InputStreamReader streamIn = new InputStreamReader(System.in);
	public static BufferedReader in = new BufferedReader(streamIn);
	
	public static void main (String args[]) throws IOException {
		while (stillValid) {
			// clean up before content of loop
			resetValues();
			if (debug) System.out.println("badSelections " + badSelections);
			System.out.println("\n");
			
			System.out.println("Enter 3 to try to break a cipher.");
			System.out.println("Enter 2 to decrypt using the existing key.");
			System.out.println("Enter 1 to encrypt using the existing key.");
			System.out.println("Enter 0 to quit.");
			System.out.print("Your selection: ");
			userInput.insert(0, in.readLine());
			try { // catch an error if the input is not an integer
				userSelection = Integer.parseInt(userInput.toString());
			}catch (NumberFormatException e) {
				if (debug) System.out.println("Main number error caught.");
				badUser();
				continue;
			}
			
			try { // this is actually the main activity
				interactWithUser();
			} catch (WrongInputLengthException e) { // applies only to case 2
				System.out.println("Incorrect input length for this key.");
				badUser();
			} catch (NumberFormatException e) {
				System.out.println("This takes only integers.");
				if (debug) System.out.println(e);
				badUser();
			}
		}
	} // main
	
	/**
	 * Prints out users instructions according to selection, and calls the
	 * relevant class for the requested activity.  Called by main.
	 *
	 * @throws IOException  If error with input
	 * @throws WrongInputLengthException  If user inputs incorrect length
	 */
	public static void interactWithUser() throws IOException,
		WrongInputLengthException {
		switch (userSelection){
			
			case 0:
				stillValid = false;
				break;
			
			case 1:
				System.out.println("Enter your text to encrypt with RSA.");
				System.out.println("No fancy characters, including accents.");
				System.out.println("Pressing a carriage return will begin" +
					" encryption.");
				currentCase.initializePlain(in.readLine());
				System.out.print("Encrypting ...");
				if (debug) System.out.println();
				RSA.encrypt();
				System.out.println("\nYour ciphertext is as follows:");
				System.out.println(currentCase.cipherBlock);
				break;
			
			case 2:
				System.out.println("Enter your text to decrypt with RSA.");
				System.out.println("Enter the large integer to decrypt.");
				System.out.println("Pressing a carriage return will begin" +
					" decryption.");
				currentCase.initializeCipher(in.readLine());
				System.out.print("Decrypting ...");
				if (debug) { System.out.println("yo"); }
				RSA.decrypt();
				System.out.println("\nPound signs at the end may not have" +
					" been part of the original message.");
				System.out.println("Your plaintext is as follows:");
				System.out.println(currentCase.plainBlock);
				break;
			
			case 3:
				AttackRSA.attack();
				break;
			
			default: // not a sanctioned entry, though an integer
				badUser();
				break;
		}
	}
	
	/**
	 * Keeps track of how many times the user has messed up, and eventually
	 * just quits.  Called by main or elsewhere.
	 */
	static void badUser() {
		// When dealing with a stupid or defiant user, don't even attempt
		// to explain.  Just try it again.  Eventually give up.
		
		if (badSelections < 5) {
			badSelections++;
		} else {
			stillValid = false;
		}
	}	
	
	/**
	 * Clears variable values all over the classes before repeating the loop.
	 */
	static void resetValues(){
		userSelection = 5;
		userInput.delete(0, userInput.length());
		currentCase.clearAll();
		RSA.clearAll();
		
	}
} // class