package de.vanitasvitae.enigmandroid.enigma.rotors;

/**
 * Reflector of the enigma machine.
 * The reflector was used to reflect the scrambled signal at the end of the wiring back to
 * go through another (reversed but not inverting) process of scrambling.
 * 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 Reflector
{
    protected String name;
    protected int type;
    protected Integer[] connections;

    /**
     * This constructor is not accessible from outside this class file.
     * Use the one of the createReflector* methods instead to create concrete Reflectors from
     * outside this class file
     * @param name phonetic name of the reflector (usually A,B,C)
     * @param type type indicator of the reflector (A->1,...,C->3)
     * @param connections wiring of the reflector as Integer array
     */
    protected Reflector(String name, int type, Integer[] connections)
    {
        this.name = name;
        this.type = type;
        this.connections = connections;
    }

    /**
     * Factory method to create reflectors.
     * @param type type of the created reflector
     *             1 -> ReflectorA
     *             2 -> ReflectorB
     *             anything else -> ReflectorC
     * @return ReflectorA | ReflectorB | ReflectorC
     */
    public static Reflector createReflector(int type)
    {
        switch (type)
        {
            case 1: return new ReflectorA();
            case 2: return new ReflectorB();
            case 3: return new ReflectorC();
            case 4: return new ReflectorThinB();
            default: return new ReflectorThinC();
        }
    }

    /**
     * Substitute an input signal via the wiring of the reflector with a different (!) output.
     * The output MUST not be equal to the input for any input, since this was not possible
     * due to the electronic implementation of the historical enigma machine.
     * @param input input signal
     * @return encrypted (substituted) output
     */
    public int encrypt(int input)
    {
        return this.connections[normalize(input)];
    }

    /**
     * Return the type indicator of the reflector
     * @return type
     */
    public int getType()
    {
        return this.type;
    }

    /**
     * Return phonetic name of the reflector
     * @return name
     */
    public String getName()
    {
        return this.name;
    }

    /**
     * Return the size (ie the number of wires/length of the connections array) of the reflector
     * @return size
     */
    private 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 reflector. This is necessary since java allows negative modulo values,
     * which can break this implementation
     * @param input input signal
     * @return "normalized" input signal
     */
    private int normalize(int input)
    {
        return (input + this.getRotorSize()) % this.getRotorSize();
    }

    /**
     * Concrete implementation of ReflectorA
     * Used in Enigma I
     * AE  BJ  CM  DZ  FL  GY  HX  IV  KW  NR  OQ  PU  ST
     */
    private static class ReflectorA extends Reflector
    {
        public ReflectorA()
        {
            super("A", 1, new Integer[]{4,9,12,25,0,11,24,23,21,1,22,5,2,17,16,20,14,13,19,18,15,8,10,7,6,3});
        }
    }

    /**
     * Concrete implementation of ReflectorB
     * Used in Enigma I, M3
     * AY  BR  CU  DH  EQ  FS  GL  IP  JX  KN  MO  TZ  VW
     */
    private static class ReflectorB extends Reflector
    {
        public ReflectorB()
        {
            super("B", 2, new Integer[]{24,17,20,7,16,18,11,3,15,23,13,6,14,10,12,8,4,1,5,25,2,22,21,9,0,19});
        }
    }

    /**
     * Concrete implementation of ReflectorC
     * Used in Enigma I, M3
     * AF  BV  CP  DJ  EI  GO  HY  KR  LZ  MX  NW  QT  SU
     */
    private static class ReflectorC extends Reflector
    {
        public ReflectorC()
        {
            super("C", 3, new Integer[]{5,21,15,9,8,0,14,24,4,3,17,25,23,22,6,2,19,10,20,16,18,1,13,12,7,11});
        }
    }

    /**
     * Concrete implementation of thin reflector type b (not equal to normal type b!)
     * When used with Rotor Beta on rotation 0, the pair was equivalent to normal reflector B
     * S->Beta->ThinB->Beta'->X == X->UKWB->S
     * Used in Enigma M4
     * E N K Q A U Y W J I C O P B L M D X Z V F T H R G S
     */
    private static class ReflectorThinB extends Reflector
    {
        public ReflectorThinB()
        {
            super("B", 4, new Integer[]{4,13,10,16,0,20,24,22,9,8,2,14,15,1,11,12,3,23,25,21,5,19,7,17,6,18});
        }
    }

    /**
     * Concrete implementation of thin reflector type c (not equal to normal type c!)
     * When used with Rotor Gamma on rotation 0, the pair was equivalent to normal reflector C
     * S->Gamma->ThinC->Gamma'->X == X->UKWC->S
     * Used in Enigma M4
     * R D O B J N T K V E H M L F C W Z A X G Y I P S U Q
     */
    private static class ReflectorThinC extends Reflector
    {
        public ReflectorThinC()
        {
            super("B", 5, new Integer[]{17,3,14,1,9,13,19,10,21,4,7,12,11,5,2,22,25,0,23,6,24,8,15,18,20,16});
        }
    }

}