/**
 * Title:		RXCipher
 * Description:	Simple and relatively quick stream cipher algorithm - JavaScript implementation
 * Author:		Jonathan Voss
 * Date:		8/7/2012 (v1.0); 12/16/2014 (v2.0); 11/19/2015 (v3.0)
 * Version:		3.2
 * Namespace:	github.com/k98kurz
 * License:		MIT
 *
 * Basic byte-level algorithm
 * t = plaintext byte, c = ciphertext byte, k = encryption keystream byte
 *		function enc (t, k) { return (t+k>255 ? t+k-256 : t+k)^k; }
 *		function dec (c, k) { return (c^k)-k<0 ? (c^k)-k+256 : (c^k)-k; }
 *
 *
 * Class implementation
 * Methods:
 *		encrypt ( plaintext )
 *			encrypts plaintext with key stream derived from skey
 *		decrypt ( ciphertext)
 *			decrypts ciphertext with key stream derived from skey
 *		getKeyStream ()
 *			returns a KeyStream for PRNG generation
 *		reset ()
 *			resets the internal KeyStream
 *
 * Changes:
 *	2.0 (12/16/2014): added pseudo-random key stream; dropped automatic hex conversion of ciphertext
 *	2.1 (12/29/2014): changed default seed value for XORShiftPlus PRNG
 *	2.2 (11/18/2015): converts to/from UTF-8 encoding; new keystream uses multiple csprngs and XORs the key with csprng values
 *	2.3 (11/18/2015): added explicit IV support; made base RXEncrypt & RXDecrypt use a Uint8 byte
 *	3.0 (11/19/2015): changed KeyStream to use an internally mixed 64 byte state; improved IV handling; improved performance
 *	3.1 (02/01/2016): updated KeyStream to use improved/fixed XORShiftPlus class; encrypt/decrypt use hex; encryptRaw/decryptRaw use Uint8Array
 *	3.2 (03/08/2016): bug fix: getKeyStream now returns actual KeyStream; reset method returns this
*/

function RXCipher (key, iv) {
	var skey, siv = iv, stream;
	skey = (typeof key == 'object' && key instanceof Uint8Array) ? fromUTF8Array(key) : key;
	siv = (typeof iv == 'object' && iv instanceof Uint8Array) ? fromUTF8Array(iv) : iv;
	stream = new KeyStream(skey, siv);

	function encrypt (plaintext) {
		var ciphertext = new Uint8Array(plaintext.length), g, t, k, key;
		key = stream.get(plaintext.length);
		for (var i = 0, ij = plaintext.length; i < ij; ++i) {
			ciphertext[i] = plaintext[i] ^ key[i];
		}
		return ciphertext;
	}

	function decrypt (ciphertext) {
		var plaintext = new Uint8Array(ciphertext.length), g, c, k, key;
		key = stream.get(ciphertext.length);
		for (var i = 0, ij = ciphertext.length; i < ij; ++i) {
			plaintext[i] = ciphertext[i] ^ key[i];
		}
		return plaintext;
	}

	this.encrypt = function (plaintext) {
		var ciphertext = encrypt(toUTF8Array(plaintext));
		return toHex(ciphertext);
	};

	this.decrypt = function (ciphertext) {
		var plaintext = decrypt(fromHex(ciphertext));
		return fromUTF8Array(plaintext);
	};

	this.encryptRaw = function (plaintext) {
		return encrypt(toUTF8Array(plaintext));
	};

	this.decryptRaw = function (ciphertext) {
		return fromUTF8Array(decrypt(ciphertext));
	};

	this.getKeyStream = function () {
		return new KeyStream(skey, siv);
	};

	this.reset = function () {
		stream = new KeyStream (skey, siv);
		return this;
	};

	function RXEncrypt (t, k, workingByte) {
		workingByte[0] = (t+k);
		return workingByte[0]^k;
	}

	function RXDecrypt (c, k, workingByte) {
		workingByte[0] = (c^k) - k;
		return workingByte[0];
	}

	/**
	 *  Class: XORShiftPlus: "non-linear" PRNG
	 *  Description: Based upon the xorshift128+ generator, one of the fastest generators passing BigCrush.
	 *	Methods:
	 *		next(n)			returns Uint32Array of n random numbers
	 *		nextHex(n)		returns Array of n hexidecimal numbers
	 *		bytes(n)		returns Uint8Array of n random bytes
	 *		bytesHex(n)		returns Array of n random bytes in hexidecimal
	 *		hex(n)			returns hexidecimal string of n bytes
	 *	Note: This generates with higher periodicity and better random distribution than the linear XORShift
	 */
	function XORShiftPlus (seed) {
		var x = new Uint32Array(1), y = new Uint32Array(1), z = new Uint32Array(1), w = new Uint32Array(1);
		x[0] = seed ? seed|0 : 317973455;
		y[0] = x[0]<<362436069;
		z[0] = y[0]+x[0];
		w[0] = z[0]^x[0]+y[0];

		function next () {
			var t = new Uint32Array(1);
			t[0] = x[0]^(x<<11);
			x[0] = y[0]; y[0] = z[0]; z[0] = w[0];
			w[0] = w[0]^(w[0]>>19)^(t[0]^(t[0]>>8));
			return w[0]+y[0];
		}

		// discard the first numbers as they are somewhat predictable
		for (var i=0, n=next(), j=next()%256; i<=j; next(), ++i);

		this.next = function (n, option) {
			if (typeof n == 'undefined' || typeof n !== 'number')
				var n = 1;
			var t; n |= 0; n = n>0 ? n : 1;
			if (typeof option == 'undefined' || typeof n !== 'number')
				var option = 0;

			// redundant code, but improved performance
			switch (option) {
				// nextHex
				case 1:
					t = [];
					for (var i=0, il=n; i<il; t[i++] = next().toString(16));
					break;
				// bytes
				case 2:
					t = new Uint8Array(n);
					for (var i=0, il=n; i<il; t[i++] = next());
					break;
				// bytesHex
				case 3:
					t = [];
					for (var i=0, il=n; i<il; t[i] = (next()%256).toString(16), t[i] = t[i].length%2 ? '0'+t[i] : t[i], ++i);
					break;
				// hex
				case 4:
					t = [];
					for (var i=0, il=n; i<il; t[i] = (next()%256).toString(16), t[i] = t[i].length%2 ? '0'+t[i] : t[i], ++i);
					t = t.join('');
					break;
				// next
				default:
					t = new Uint32Array(n);
					for (var i=0, il=n; i<il; t[i++] = next());
			}
			return t;
		};

		this.nextHex = function (n) { return this.next(n, 1); };

		this.bytes = function (n) { return this.next(n, 2); };

		this.bytesHex = function (n) { return this.next(n, 3); };

		this.hex = function (n) { return this.next(n, 4); };
	}

	function KeyStream (key, iv) {
		var csprngs, state, keyLength, keyIndex, stateIndex, workingByte = new Uint8Array(1), t, j;

		if (typeof key == 'undefined')
			throw new Error('RXCipher@KeyStream: key required');
		if (typeof key == 'object' && key instanceof Array)
			key = (typeof key[0] == 'number') ? new Uint8Array(key) : key.join('');
		if (typeof key == 'string')
			key = toUTF8Array(key);
		if (typeof key !== 'object' && !(key instanceof Uint8Array))
			throw new Error('RXCipher@KeyStream: expected key of type String, Array, or Uint8Array');

		if (typeof iv == 'undefined')
			iv = '0123456';
		if (typeof iv == 'object' && iv instanceof Array)
			iv = (typeof iv[0] == 'number') ? new Uint8Array(iv) : iv.join('');
		if (typeof iv == 'string')
			iv = toUTF8Array(iv);
		if (!(iv instanceof Uint8Array) || iv.length == 0)
			throw new Error('RXCipher@KeyStream: expected iv of type String, Array or Uint8Array, or undefined');

		// initialize some internal state
		csprngs = []; keyLength = key.length; keyIndex = 0; state = new Uint8Array(64); stateIndex = 0;
		for (var i = 0; i < keyLength; i++) {
			csprngs[i] = new XORShiftPlus(key[i]);
		}
		for (var i = 0, j = 0, c = 0; c < keyLength * 4; ++i, ++j, ++c) {
			j = (j == keyLength) ? 0 : j;
			i = (i == iv.length) ? 0 : i;
			key[j] = key[j] + iv[i];
		}
		for (var i = 0, j = 0; i < 64; ++i, ++j) {
			j = (j == keyLength) ? 0 : j;
			state[i] = csprngs[j].next()[0];
		}
		for (var i = 63, j = 0, t, m; i >= 0; --i, ++j) {
			j = (j == keyLength) ? 0 : j;
			t = (csprngs[j].next()[0]+key[j])%64;
			m = state[t];
			state[t] = RXEncrypt(state[i], key[j], workingByte);
			state[i] = RXDecrypt(m, t, workingByte);
		}

		function next () {
			keyIndex = (++keyIndex == keyLength) ? 0 : keyIndex;
			stateIndex = (++stateIndex == 64) ? 0 : stateIndex;
			state[stateIndex] = RXEncrypt(state[stateIndex], key[keyIndex], workingByte);
			state[63 - stateIndex] = RXEncrypt(state[63 - stateIndex], state[stateIndex], workingByte);
			return state[stateIndex];
		}

		this.get = function (nBytes) {
			nBytes = (nBytes|0 ? nBytes|0 : (parseInt(nBytes) ? parseInt(nBytes) : 1));
			var k = new Uint8Array(nBytes);
			for (var o=0; o<nBytes; ++o) {
				k[o] = next();
			}
			return k;
		};
	}

	// convert from JavaScript's internal UTF-16 strings to UTF-8
	// ripped from http://stackoverflow.com/a/18729931
	// credit: Joni Salonen
	function toUTF8Array(str) {
		var utf8 = [], charcode;
		for (var i=0; i < str.length; i++) {
			charcode = str.charCodeAt(i);
			if (charcode < 0x80) utf8.push(charcode);
			else if (charcode < 0x800) {
				utf8.push(0xc0 | (charcode >> 6),
						0x80 | (charcode & 0x3f));
			} else if (charcode < 0xd800 || charcode >= 0xe000) {
				utf8.push(0xe0 | (charcode >> 12),
						0x80 | ((charcode>>6) & 0x3f),
						0x80 | (charcode & 0x3f));
			} else { // surrogate pair
				i++;
				// UTF-16 encodes 0x10000-0x10FFFF by
				// subtracting 0x10000 and splitting the
				// 20 bits of 0x0-0xFFFFF into two halves
				charcode = 0x10000 + (((charcode & 0x3ff)<<10)
						| (str.charCodeAt(i) & 0x3ff));
				utf8.push(0xf0 | (charcode >>18),
						0x80 | ((charcode>>12) & 0x3f),
						0x80 | ((charcode>>6) & 0x3f),
						0x80 | (charcode & 0x3f));
			}
		}
		return new Uint8Array(utf8);
	}

	// convert from UTF-8 to JavaScript's internal UTF-16 strings
	// ripped from https://github.com/coolaj86/TextEncoderLite
	// credit: AJ ONeal (coolaj86) && Feross Aboukhadijeh (feross)
	function fromUTF8Array (arr) {
		var utf16 = '', tmp = '';
		for (var i = 0, ij = arr.length; i < ij; i++) {
			if (arr[i] <= 0x7F) {
				utf16 += decodeUtf8Char(tmp) + String.fromCharCode(arr[i]);
				tmp = '';
			} else {
				tmp += '%' + arr[i].toString(16);
			}
		};

		return utf16 + decodeUtf8Char(tmp);
	}

	function decodeUtf8Char (str) {
		try {
			return decodeURIComponent(str);
		} catch (err) {
			return String.fromCharCode(0xFFFD); // UTF 8 invalid char
		}
	}

	function toHex (raw) {
		var t = [];
		for (var i=0, il=raw.length; i<il; ++i) {
		    t[i] = raw[i].toString(16); t[i] = t[i].length%2 ? '0'+t[i] : t[i];
		}
		return t.join('');
	}

	function fromHex (hex) {
		var t = new Uint8Array(hex.length/2);
		for (var i=0, j=0, il=hex.length; i<il; ++i, ++j) {
		    t[j] = parseInt(hex[i] + hex[++i], 16);
		}
		return t;
	}
};