package de.vanitasvitae.enigmandroid.enigma.rotors;

/**
 * Rotor super class and inner concrete implementations
 * The rotors were the key feature of the enigma used to scramble up input signals into
 * encrypted signals difficult to predict. The rotors rotated to achieve a poly-alphabetic
 * substitution which was hard to break. Each signal passes the rotor twice. Once in "forward"-
 * direction and once in "backwards"-direction. There was a set of 3 out of 5 rotors inside the
 * enigma machine M4.
 * 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 class Rotor
{
    protected String type;
    protected int number;
    protected Integer[] connections;
    protected Integer[] reversedConnections;
    protected Integer[] turnOverNotches;

    protected int ringSetting;
    protected int rotation;

    /**
     * This constructor is not accessible from outside this class file.
     * Use one of the createRotor* factory methods instead to create concrete Rotors.
     * Note that connections and reversedConnections MUST be of the same size and that
     * neither connections nor reversedConnections respectively MUST have any number between
     * 0 and connections.length-1 only once (ie they represent permutations)
     * @param type type indicator
     * @param connections wiring of the rotor as Integer array
     * @param reversedConnections inverse wiring used to encryptString in the opposite direction
     *                            (connections[reversedConnections[i]] = i
     *                            for all i in 0..getRotorSize()-1.
     * @param turnOverNotches Position(s) of the turnover notch(es)
     * @param ringSetting setting of the ring that holds the letters
     * @param rotation rotation of the rotor
     */
    protected Rotor(String type, int number, Integer[] connections, Integer[] reversedConnections,
                    Integer[] turnOverNotches, int ringSetting, int rotation)
    {
        this.type = type;
        this.number = number;
        this.connections = connections;
        this.reversedConnections = reversedConnections;
        this.turnOverNotches = turnOverNotches;
        this.ringSetting = ringSetting;
        this.rotation = rotation;
    }

    /**
     * Factory method that creates a rotor accordingly to the type.
     * Also initialize the rotor with ringSetting and rotation.
     * @param type type indicator (1..10)
     *             1..8 -> I..VIII
     *             9,10 -> Beta, Gamma
     *             11..13 -> DI..DIII
     * @param ringSetting setting of the outer ring (0..25)
     * @param rotation rotation of the rotor
     * @return Concrete rotor
     */
    public static Rotor createRotor(int type, int rotation, int ringSetting)
    {
        switch (type)
        {
            case 0: return new EntryWheelD();
            case 1: return new RotorI(rotation, ringSetting);
            case 2: return new RotorII(rotation, ringSetting);
            case 3: return new RotorIII(rotation, ringSetting);
            case 4: return new RotorIV(rotation, ringSetting);
            case 5: return new RotorV(rotation, ringSetting);
            case 6: return new RotorVI(rotation, ringSetting);
            case 7: return new RotorVII(rotation, ringSetting);
            case 8: return new RotorVIII(rotation, ringSetting);
            case 9: return new RotorBeta(rotation, ringSetting);
            case 10: return new RotorGamma(rotation, ringSetting);
            case 11: return new RotorDI(rotation, ringSetting);
            case 12: return new RotorDII(rotation, ringSetting);
            case 13: return new RotorDIII(rotation, ringSetting);

            default: return new RotorI(rotation, ringSetting);
        }
    }

    /**
     * Encrypt an input signal via the internal wiring in "forward" direction towards the reflector
     * (using connections)
     * @param input signal
     * @return encrypted signal
     */
    public int encryptForward(int input)
    {
        return this.connections[normalize(input)];
    }

    /**
     * Encrypt an input signal via the internal wiring in "backwards" direction (using
     * reversedConnections)
     * @param input signal
     * @return encrypted signal
     */
    public int encryptBackward(int input)
    {
        return this.reversedConnections[normalize(input)];
    }

    /**
     * Return the type indicator (usually 1..5)
     * @return type indicator
     */
    public String getType()
    {
        return this.type;
    }

    public int getNumber()
    {
        return this.number;
    }

    /**
     * Return the current rotation of the rotor.
     * The rotation consists of the actual rotation - the ringSetting
     * @return rotation-ringSetting
     */
    public int getRotation()
    {
        return this.rotation;
    }

    /**
     * Increment rotation of the rotor by one.
     */
    public void rotate()
    {
        this.rotation = normalize(this.getRotation()+1);
    }

    /**
     * Return true, if the rotor is at a position, where it turns over the next rotor by one
     * @return rotation==turnOverNotch
     */
    public boolean isAtTurnoverPosition()
    {
        for(int x : getTurnOverNotches())
        {
            //if(x == this.rotation + this.ringSetting) return true;
            if(x == this.rotation) return true;
        }
        return false;
    }

    /**
     * Return true, if the rotor is in a position where the double turn anomaly happens.
     * The double turn anomaly (german: Doppelsprung-Anomalie) is an anomaly in the rotor movement
     * caused by the mechanical implementation of the enigma.
     * Whenever the rightmost rotor turns the middle rotor AND the middle rotor is only one move
     * from turning the leftmost rotor, the middle rotor turns again with the next character.
     * So technically there are only 26*25*26 possible rotor settings for any but firmly 3 rotors.
     * @return rotation == turnOverNotch-1
     */
    public boolean doubleTurnAnomaly()
    {
        for(int x : getTurnOverNotches())
        {
            if(this.rotation == x-1) return true;
        }
        return false;
    }

    /**
     * Returns the positions of the turnover notches in a array
     * @return turnOverNotches
     */
    public Integer[] getTurnOverNotches()
    {
        return this.turnOverNotches;
    }

    /**
     * Return ringSettings of the rotor
     * @return ringSetting
     */
    public int getRingSetting()
    {
        return this.ringSetting;
    }


    /**
     * Returns the size (ie the number of wires/size of the connections array)
     * of the rotor
     * @return size
     */
    public int getRotorSize()
    {
        return this.connections.length;
    }

    /**
     * Normalize the input.
     * Normalizing means keeping the input via modulo in the range from 0 to n-1, where n is equal
     * to the size of the rotor. This is necessary since java allows negative modulo values,
     * which can break this implementation
     * @param input input signal
     * @return "normalized" input signal
     */
    public int normalize(int input)
    {
        return (input + this.getRotorSize()) % this.getRotorSize();
    }

    /**
     * Concrete implementation of Rotor of type 1 (I)
     * Used in Enigma I, M3, M4
     * E K M F L G D Q V Z N T O W Y H X U S P A I B R C J
     */
    private static class RotorI extends Rotor
    {
        public RotorI(int rotation, int ringSetting)
        {
            super("I", 1,
                    new Integer[]{4, 10, 12, 5, 11, 6, 3, 16, 21, 25, 13, 19, 14, 22, 24, 7, 23, 20, 18, 15, 0, 8, 1, 17, 2, 9},
                    new Integer[]{20, 22, 24, 6, 0, 3, 5, 15, 21, 25, 1, 4, 2, 10, 12, 19, 7, 23, 18, 11, 17, 8, 13, 16, 14, 9},
                    new Integer[]{17}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 2 (II)
     * Used in Enigma I, M3, M4
     * A J D K S I R U X B L H W T M C Q G Z N P Y F V O E
     */
    private static class RotorII extends Rotor
    {
        public RotorII(int rotation, int ringSetting)
        {
            super("II", 2,
                    new Integer[]{0, 9, 3, 10, 18, 8, 17, 20, 23, 1, 11, 7, 22, 19, 12, 2, 16, 6, 25, 13, 15, 24, 5, 21, 14, 4},
                    new Integer[]{0, 9, 15, 2, 25, 22, 17, 11, 5, 1, 3, 10, 14, 19, 24, 20, 16, 6, 4, 13, 7, 23, 12, 8, 21, 18},
                    new Integer[]{5}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 3 (III)
     * Used in Enigma I, M3, M4
     * B D F H J L C P R T X V Z N Y E I W G A K M U S Q O
     */
    private static class RotorIII extends Rotor
    {
        public RotorIII(int rotation, int ringSetting)
        {
            super("III", 3,
                    new Integer[]{1, 3, 5, 7, 9, 11, 2, 15, 17, 19, 23, 21, 25, 13, 24, 4, 8, 22, 6, 0, 10, 12, 20, 18, 16, 14},
                    new Integer[]{19, 0, 6, 1, 15, 2, 18, 3, 16, 4, 20, 5, 21, 13, 25, 7, 24, 8, 23, 9, 22, 11, 17, 10, 14, 12},
                    new Integer[]{22}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 4 (IV)
     * Used in Enigma M3, M4
     * E S O V P Z J A Y Q U I R H X L N F T G K D C M W B
     */
    private static class RotorIV extends Rotor
    {
        public RotorIV(int rotation, int ringSetting)
        {
            super("IV", 4,
                    new Integer[]{4, 18, 14, 21, 15, 25, 9, 0, 24, 16, 20, 8, 17, 7, 23, 11, 13, 5, 19, 6, 10, 3, 2, 12, 22, 1},
                    new Integer[]{7, 25, 22, 21, 0, 17, 19, 13, 11, 6, 20, 15, 23, 16, 2, 4, 9, 12, 1, 18, 10, 3, 24, 14, 8, 5},
                    new Integer[]{10}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 5 (V)
     * Used in Enigma M3, M4
     * V Z B R G I T Y U P S D N H L X A W M J Q O F E C K
     */
    private static class RotorV extends Rotor
    {
        public RotorV(int rotation, int ringSetting)
        {
            super("V", 5,
                    new Integer[]{21, 25, 1, 17, 6, 8, 19, 24, 20, 15, 18, 3, 13, 7, 11, 23, 0, 22, 12, 9, 16, 14, 5, 4, 2, 10},
                    new Integer[]{16, 2, 24, 11, 23, 22, 4, 13, 5, 19, 25, 14, 18, 12, 21, 9, 20, 3, 10, 6, 8, 0, 17, 15, 7, 1},
                    new Integer[]{0}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 6 (VI)
     * Used in Enigma M3, M4
     * J P G V O U M F Y Q B E N H Z R D K A S X L I C T W
     */
    private static class RotorVI extends Rotor
    {
        public RotorVI(int rotation, int ringSetting)
        {
            super("VI", 6,
                    new Integer[]{9,15,6,21,14,20,12,5,24,16,1,4,13,7,25,17,3,10,0,18,23,11,8,2,19,22},
                    new Integer[]{18,10,23,16,11,7,2,13,22,0,17,21,6,12,4,1,9,15,19,24,5,3,25,20,8,14},
                    new Integer[]{0,13}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 7 (VII)
     * Used in Enigma M3, M4
     * N Z J H G R C X M Y S W B O U F A I V L P E K Q D T
     */
    private static class RotorVII extends Rotor
    {
        public RotorVII(int rotation, int ringSetting)
        {
            super("VII", 7,
                    new Integer[]{13,25,9,7,6,17,2,23,12,24,18,22,1,14,20,5,0,8,21,11,15,4,10,16,3,19},
                    new Integer[]{16,12,6,24,21,15,4,3,17,2,22,19,8,0,13,20,23,5,10,25,14,18,11,7,9,1},
                    new Integer[]{0,13}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type 8 (VIII)
     * Used in Enigma M3, M4
     * F K Q H T L X O C B J S P D Z R A M E W N I U Y G V
     */
    private static class RotorVIII extends Rotor
    {
        public RotorVIII(int rotation, int ringSetting)
        {
            super("VIII", 8,
                    new Integer[]{5,10,16,7,19,11,23,14,2,1,9,18,15,3,25,17,0,12,4,22,13,8,20,24,6,21},
                    new Integer[]{16,9,8,13,18,0,24,3,21,10,1,5,17,20,7,12,2,15,11,4,22,25,19,6,23,14},
                    new Integer[]{0,13}, ringSetting, rotation);
        }
    }

    /**
     * Concrete implementation of Rotor of type beta (Griechenwalze Beta)
     * Beta was used as a "thin" rotor in the M4. It was thinner than a "normal" rotor, so it
     * could be used together with one of the two thin reflectors as one rotor.
     * When used together with ReflectorThinB, Beta was equivalent to Reflector B (if rotation == 0)
     * That way the M4 was backwards compatible to the M3
     * Used in M4
     */
    private static class RotorBeta extends Rotor
    {
        public RotorBeta(int rotation, int ringSetting)
        {
            super("Beta", 9,
                    new Integer[]{11,4,24,9,21,2,13,8,23,22,15,1,16,12,3,17,19,0,10,25,6,5,20,7,14,18},
                    new Integer[]{17,11,5,14,1,21,20,23,7,3,18,0,13,6,24,10,12,15,25,16,22,4,9,8,2,19},
                    new Integer[]{}, ringSetting, rotation);
        }
        @Override
        public void rotate()
        {
            //Thin rotors are fixed in position, so they dont rotate
        }

        @Override
        public boolean doubleTurnAnomaly()
        {
            //Nope, no anomaly
            return false;
        }
    }

    /**
     * Concrete implementation of Rotor of type gamma (Griechenwalze Gamma)
     * Gamma was used as a "thin" rotor in the M4. It was thinner than a "normal" rotor, so it
     * could be used together with one of the two thin reflectors as one rotor.
     * When used together with ReflectorThinC, Gamma is equivalent to Reflector C
     * (if rotation == 0). That way the M4 was backwards compatible to the M3
     * Used in M4
     */
    private static class RotorGamma extends Rotor
    {
        public RotorGamma(int rotation, int ringSetting)
        {
            super("Gamma", 10,
                    new Integer[]{5,18,14,10,0,13,20,4,17,7,12,1,19,8,24,2,22,11,16,15,25,23,21,6,9,3},
                    new Integer[]{4,11,15,25,7,0,23,9,13,24,3,17,10,5,2,19,18,8,1,12,6,22,16,21,14,20},
                    new Integer[]{}, ringSetting, rotation);
        }
        @Override
        public void rotate()
        {
            //Thin rotors are fixed in position, so they don't rotate
        }

        @Override
        public boolean doubleTurnAnomaly()
        {
            //Thin rotors don't do such weird stuff, they're normal just like you and me.
            return false;
        }
    }

    private static class EntryWheelD extends Rotor
    {
        public EntryWheelD()
        {
            super("ETW-D", 0,
                    new Integer[]{9,22,20,11,2,12,13,14,7,15,16,25,24,23,8,17,0,3,10,4,6,21,1,19,18,5},
                    new Integer[]{16,22,4,17,19,25,20,8,14,0,18,3,5,6,7,9,10,15,24,23,2,21,1,13,12,11},
                    new Integer[]{}, 0, 0);
        }
        @Override
        public void rotate()
        {
            //EntryWheel doesn't rotate
        }

        @Override
        public boolean doubleTurnAnomaly()
        {
            //\forall s \in States : nope
            return false;
        }
    }

    /**
     * Rotor I as used in the Enigma Type D
     * L P G S Z M H A E O Q K V X R F Y B U T N I C J D W
     * Turnover Z
     */
    private static class RotorDI extends Rotor
    {
        public RotorDI(int rotation, int ringSetting)
        {
            super("D-I", 11,
                    new Integer[]{11,15,6,18,25,12,7,0,4,14,16,10,21,23,17,5,24,1,20,19,13,8,2,9,3,22},
                    new Integer[]{7,17,22,24,8,15,2,6,21,23,11,0,5,20,9,1,10,14,3,19,18,12,25,13,16,4},
                    new Integer[]{25}, ringSetting, rotation);
        }
    }

    /**
     * Rotor II as used in the Enigma Type D
     * S L V G B T F X J Q O H E W I R Z Y A M K P C N D U
     * Turnover F
     */
    private static class RotorDII extends Rotor
    {
        public RotorDII(int rotation, int ringSetting)
        {
            super("D-II", 12,
                    new Integer[]{18,11,21,6,1,19,5,23,9,16,14,7,4,22,8,17,25,24,0,12,10,15,2,13,3,20},
                    new Integer[]{18,4,22,24,12,6,3,11,14,8,20,1,19,23,10,21,9,15,0,5,25,2,13,7,17,16},
                    new Integer[]{5}, ringSetting, rotation);
        }
    }

    /**
     * Rotor III as used in the Enigma Type D
     * C J G D P S H K T U R A W Z X F M Y N Q O B V L I E
     * Turnover O
     */
    private static class RotorDIII extends Rotor
    {
        public RotorDIII(int rotation, int ringSetting)
        {
            super("D-III", 13,
                    new Integer[]{2,9,6,3,15,18,7,10,19,20,17,0,22,25,23,5,12,24,13,16,14,1,21,11,8,4},
                    new Integer[]{11,21,0,3,25,15,2,6,24,1,7,23,16,18,20,4,19,10,5,8,9,22,12,14,17,13},
                    new Integer[]{14}, ringSetting, rotation);
        }
    }
}