EnigmAndroid/app/src/main/java/de/vanitasvitae/enigmandroid/enigma/Enigma.java

package de.vanitasvitae.enigmandroid.enigma;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Random;

import de.vanitasvitae.enigmandroid.MainActivity;
import de.vanitasvitae.enigmandroid.enigma.rotors.EntryWheel;
import de.vanitasvitae.enigmandroid.enigma.rotors.Reflector;
import de.vanitasvitae.enigmandroid.enigma.rotors.Rotor;

/**
 * Main component of the Enigma machine
 * This is the mostly abstract base of any enigma machine.
 * Copyright (C) 2015  Paul Schaub

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 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 General Public License for more details.

 You should have received a copy of the GNU General Public License along
 with this program; if not, write to the Free Software Foundation, Inc.,
 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 * @author vanitasvitae
 */
public abstract class Enigma
{
    protected static String machineType;

    protected boolean doAnomaly = false;  //Has the time come to handle an anomaly?

    protected ArrayList<EntryWheel> availableEntryWheels;
    protected ArrayList<Rotor> availableRotors;
    protected ArrayList<Reflector> availableReflectors;

    protected Random rand;

    public Enigma()
    {
        establishAvailableParts();
        initialize();
    }

    /**
     * In this method, available EntryWheels, Rotors and Reflectors can be defined.
     */
    protected abstract void establishAvailableParts();

    /**
     * Add a Rotor to the ArrayList of available rotors for this machine.
     * Also set the index of the Rotor.
     * @param r Rotor
     */
    protected void addAvailableRotor(Rotor r)
    {
        if(availableRotors == null) availableRotors = new ArrayList<>();
        availableRotors.add(availableRotors.size(), r.setIndex(availableRotors.size()));
    }

    protected void addAvailableEntryWheel(EntryWheel e)
    {
        if(availableEntryWheels == null) availableEntryWheels = new ArrayList<>();
        availableEntryWheels.add(availableEntryWheels.size(), e.setIndex(availableEntryWheels.size()));
    }

    protected void addAvailableReflector(Reflector r)
    {
        if(availableReflectors == null) availableReflectors = new ArrayList<>();
        availableReflectors.add(availableReflectors.size(), r.setIndex(availableReflectors.size()));
    }

    public ArrayList<EntryWheel> getAvailableEntryWheels()
    {
        return availableEntryWheels;
    }

    public ArrayList<Rotor> getAvailableRotors()
    {
        return availableRotors;
    }

    public ArrayList<Reflector> getAvailableReflectors()
    {
        return availableReflectors;
    }

    public EntryWheel getEntryWheel(int index)
    {
        if(availableEntryWheels == null || availableEntryWheels.size() == 0) return null;
        return availableEntryWheels.get(index % availableEntryWheels.size()).getInstance();
    }

    public Rotor getRotor(int index)
    {
        if(availableRotors == null || availableRotors.size() == 0) return null;
        return availableRotors.get(index % availableRotors.size()).getInstance();
    }

    public Rotor getRotor(int index, int rotation, int ringSetting)
    {
        return getRotor(index).setRotation(rotation).setRingSetting(ringSetting);
    }

    public Reflector getReflector(int index)
    {
        if(availableReflectors == null || availableReflectors.size() == 0) return null;
        return availableReflectors.get(index % availableReflectors.size()).getInstance();
    }

    public Reflector getReflector(int index, int rotation, int ringSetting)
    {
        return getReflector(index).setRotation(rotation).setRingSetting(ringSetting);
    }

    /**
     * Set the enigma to an initial state
     */
    public abstract void initialize();

    /**
     * Encrypt / Decrypt a given String w.
     * w must be prepared using prepare(w) beforehand.
     * Doing so changes the state of the rotors but not the state of the plugboard and the
     * ringSettings
     *
     * @param w Text to decrypt/encryptString
     * @return encrypted/decrypted string
     */
    public String encryptString(String w)
    {
        //output string
        String output = "";
        //for each char x in k
        for (char x : w.toCharArray())
        {
            output = output + this.encryptChar(x);
        }
        //return en-/decrypted string
        return output;
    }

    /**
     * Set the enigma into the next mechanical state.
     * This rotates the first rotor and eventually also the second/third.
     * Also this method handles the anomaly in case it should happen.
     */
    public abstract void nextState();

    /**
     * Set the enigma into a completely random state using a unseeded SecureRandom object.
     */
    public void randomState()
    {
        this.rand = ((MainActivity) (MainActivity.ActivitySingleton.getInstance().getActivity()))
                .getSecureRandom();
        generateState();
    }

    /**
     * Set the enigma to a random state based on the initialization of rand.
     * Don not choose a rotor twice, set random rotations, ringSettings, ukw and possibly
     * plugboard / rewirable ukw configurations.
     */
     protected abstract void generateState();

    /**
     * Substitute char k by sending the signal through the enigma.
     * The signal passes the plugboard, the rotors and returns back after going through the
     * reflector wheel.
     *
     * @param k input char
     * @return substituted output char
     */
    public abstract char encryptChar(char k);

    /**
     * Set the state of the enigma
     * @param state new state
     */
    public abstract void setState(EnigmaStateBundle state);

    /**
     * Return an object representing the current state of the enigma
     * @return state
     */
    public abstract EnigmaStateBundle getState();

    /**
     * Set the rand into a certain state based on seed.
     * Then set the enigmas state.
     * @param seed passphrase
     */
    public void setStateFromSeed(String seed)
    {
        rand = new Random(seed.hashCode());
        generateState();
    }

    public abstract void restoreState(BigInteger mem);

    public abstract String stateToString();

    public static String numToMachineType(int n)
    {
        n = (12+(n+12)%12)%12; //Problem? Trolololo
        switch (n) {
            case 0: return "I";
            case 1: return "M3";
            case 2: return "M4";
            case 3: return "G31";
            case 4: return "G312";
            case 5: return "G260";
            case 6: return "D";
            case 7: return "K";
            case 8: return "KS";
            case 9: return "KSA";
            case 10: return "R";
            default: return "T";
        }
    }

    public static String chooseEnigmaFromSeed(String seed)
    {
        return numToMachineType(seed.hashCode() % 12);
    }

    public static String chooseEnigmaFromSave(BigInteger save)
    {
        return numToMachineType(getValue(save,20));
    }

    /**
     * Return the name indicator of the enigma machine
     * @return name
     */
    public String getMachineType()
    {
        return machineType;
    }

    /**
     *
     * @param s source
     * @param d domain (max value) of the value
     * @return value
     */
    public static int getValue(BigInteger s, int d)
    {
        BigInteger o = s.mod(BigInteger.valueOf(d)).add(BigInteger.valueOf(d)).mod(BigInteger.valueOf(d));
        return Integer.valueOf(o.toString());
    }

    /**
     * remove a digit of domain d from source s
     * @param s source
     * @param d domain (max value)
     * @return trimmed source
     */
    public static BigInteger removeDigit(BigInteger s, int d)
    {
        s = s.subtract(s.mod(BigInteger.valueOf(d)));
        s = s.divide(BigInteger.valueOf(d));
        return s;
    }

    /**
     *
     * @param s source
     * @param b base (max value)
     * @param v actual value
     * @return lengthened source
     */
    public static BigInteger addDigit(BigInteger s, int v, int b)
    {
        s = s.multiply(BigInteger.valueOf(b));
        s = s.add(BigInteger.valueOf(v % b));
        return s;
    }
}