ENIGMA

enigma.js

'use strict';

Array.prototype.clone = function() {
	return this.slice(0);
}

class Enigma {

	constructor() {

		this.alphabet = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];

		this.original_rotors = [
			['C','D','Z','R','M','G','H','X','A','W','Q','V','U','F','S','B','P','L','T','O','E','I','Y','N','K','J'],
			['V','E','W','O','A','S','X','D','H','R','C','Y','Q','J','N','P','T','K','B','L','M','F','U','Z','G','I'],
			['I','P','R','N','F','M','W','O','Z','J','Q','C','X','G','T','D','B','K','E','L','Y','V','A','H','S','U'],
			['D','Q','N','T','S','X','Z','R','O','J','B','A','K','C','G','E','Y','P','U','I','H','F','L','M','V','W'],
			['B','K','Q','S','L','P','M','D','C','A','N','Y','H','G','I','R','Z','V','J','F','T','U','X','E','O','W'],
			// REFLECTOR
			['O','K','Y','X','V','G','F','S','T','Q','B','W','N','M','A','U','J','Z','H','I','P','E','L','D','C','R']
		];

		this.num_plugs = 0;
		this.num_rotors = 0;

		this.rotors = [
			this.alphabet.clone() // entry rotor
		];
	}

	setPlug(letter1, letter2) {

		if ( this.num_plugs == 6 ) {
			return;
		}

		// change positions in the entry rotor
		this.rotors[0][this.alphabet.indexOf(letter1)] = letter2; 
		this.rotors[0][this.alphabet.indexOf(letter2)] = letter1;

		this.num_plugs++;
	}

	initalizeRotor(rotorIndex, entryLetter) {

		if ( this.num_rotors == 3 ) {
			return;
		}

		let entryIndex = this.alphabet.indexOf(entryLetter);
		let rotor = this.original_rotors[rotorIndex - 1].clone();
		let new_rotor = [];

		for(let i = entryIndex; i < 26; i++) {
			new_rotor.push( rotor[i] );
		}

		for(let i = 0; i < entryIndex; i++) {
			new_rotor.push( rotor[i] );
		}

		this.rotors.push(new_rotor);

		this.num_rotors++;

		// PLACE REFLECTOR AFTER ALL ROTORS
		if ( this.num_rotors == 3 ) {
			this.rotors.push( this.original_rotors[5].clone() );
		}

	}

	// Place the first letter in the end and move all to the left
	rotateRotor(rotorIndex) {

		let rotor = this.rotors[rotorIndex].clone();
		let temp = rotor[0];
		let new_rotor = rotor.slice(1, 26);

		new_rotor.push(temp);

		this.rotors[rotorIndex] = new_rotor;
	}

	encodeChar(char) {

		let index;

		// From the first rotor to the reflector
		for(let i = 0; i < 5; i++) {

			index = this.alphabet.indexOf(char);

			// Not a alphabetical letter
			if ( index < 0 ) {
				return char;
			}

			char = this.rotors[i][index];
		}

		// From the third rotor to the entry rotor
		for(let i = 3; i >= 0; i--) {
			index = this.rotors[i].indexOf(char);
			char = this.alphabet[index];
		}

		this.rotateRotor(3);

		return char;
	}

	encode(text) {
		return text.split('')
				.map(c => this.encodeChar(c))
				.join('');
	}

}

let enigma = new Enigma;

enigma.setPlug('X', 'R');
enigma.setPlug('Q', 'S');
enigma.setPlug('J', 'M');
enigma.setPlug('U', 'T');
enigma.setPlug('C', 'F');
enigma.setPlug('W', 'L');

enigma.initalizeRotor(4, 'V');
enigma.initalizeRotor(5, 'D');
enigma.initalizeRotor(3, 'O');

console.log(enigma.encode('HELLO WORLD'));