/**
 * AES Cipher function: encrypt 'input' state with Rijndael algorithm
 *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage
 *
 * @param {Number[]} input 16-byte (128-bit) input state array
 * @param {Number[][]} w   Key schedule as 2D byte-array (Nr+1 x Nb bytes)
 * @returns {Number[]}     Encrypted output state array
 */

const Aes = {};

Aes.cipher = function (input, w) {
	let i;
	// main Cipher function [§5.1]
	const Nb = 4;               // block size (in words): no of columns in state (fixed at 4 for AES)
	const Nr = w.length/Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys

	let state = [[],[],[],[]];  // initialise 4xNb byte-array 'state' with input [§3.4]

	for (i = 0; i<4*Nb; i++) state[i%4][Math.floor(i/4)] = input[i];

	state = Aes.addRoundKey(state, w, 0, Nb);

	for (let round=1; round<Nr; round++) {
		state = Aes.subBytes(state, Nb);
		state = Aes.shiftRows(state, Nb);
		state = Aes.mixColumns(state, Nb);
		state = Aes.addRoundKey(state, w, round, Nb);
	}

	state = Aes.subBytes(state, Nb);
	state = Aes.shiftRows(state, Nb);
	state = Aes.addRoundKey(state, w, Nr, Nb);

	const output = new Array(4*Nb);  // convert state to 1-d array before returning [§3.4]

	for (i = 0; i<4*Nb; i++) output[i] = state[i%4][Math.floor(i/4)];
	return output;
};

/**
 * Perform Key Expansion to generate a Key Schedule
 *
 * @param {Number[]} key Key as 16/24/32-byte array
 * @returns {Number[][]} Expanded key schedule as 2D byte-array (Nr+1 x Nb bytes)
 */
Aes.keyExpansion = function (key) {
	let i;
	// generate Key Schedule (byte-array Nr+1 x Nb) from Key [§5.2]
	const Nb = 4;            // block size (in words): no of columns in state (fixed at 4 for AES)
	const Nk = key.length/4;  // key length (in words): 4/6/8 for 128/192/256-bit keys
	const Nr = Nk + 6;       // no of rounds: 10/12/14 for 128/192/256-bit keys

	const w = new Array(Nb*(Nr+1));
	let temp = new Array(4);

	for (i = 0; i<Nk; i++) {
		const r = [key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]];

		w[i] = r;
	}

	for (i = Nk; i<(Nb*(Nr+1)); i++) {
		let t;

		w[i] = new Array(4);
		for (t = 0; t<4; t++) temp[t] = w[i-1][t];

		if (i % Nk === 0) {
			temp = Aes.subWord(Aes.rotWord(temp));
			for (t = 0; t<4; t++) temp[t] ^= Aes.rCon[i/Nk][t];
		} else if (Nk > 6 && i%Nk === 4) {
			temp = Aes.subWord(temp);
		}

		for (t = 0; t<4; t++) w[i][t] = w[i-Nk][t] ^ temp[t];
	}

	return w;
};

/*
 * ---- remaining routines are private, not called externally ----
 */

Aes.subBytes = function (s, Nb) {    // apply SBox to state S [§5.1.1]
	for (let r=0; r<4; r++) {
		for (let c=0; c<Nb; c++) s[r][c] = Aes.sBox[s[r][c]];
	}
	return s;
};

Aes.shiftRows = function (s, Nb) {    // shift row r of state S left by r bytes [§5.1.2]
	const t = new Array(4);

	for (let r=1; r<4; r++) {
		let c;

		for (c = 0; c<4; c++) t[c] = s[r][(c+r)%Nb];  // shift into temp copy
		for (c = 0; c<4; c++) s[r][c] = t[c];         // and copy back
	}          // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
	return s;  // see asmaes.sourceforge.net/rijndael/rijndaelImplementation.pdf
};

Aes.mixColumns = function (s, Nb) {   // combine bytes of each col of state S [§5.1.3]
	for (let c=0; c<4; c++) {
		const a = new Array(4);  // 'a' is a copy of the current column from 's'
		const b = new Array(4);  // 'b' is a•{02} in GF(2^8)

		for (let i=0; i<4; i++) {
			a[i] = s[i][c];
			b[i] = s[i][c]&0x80 ? s[i][c]<<1 ^ 0x011b : s[i][c]<<1;

		}
		// a[n] ^ b[n] is a•{03} in GF(2^8)
		s[0][c] = b[0] ^ a[1] ^ b[1] ^ a[2] ^ a[3]; // 2*a0 + 3*a1 + a2 + a3
		s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]; // a0 * 2*a1 + 3*a2 + a3
		s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]; // a0 + a1 + 2*a2 + 3*a3
		s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]; // 3*a0 + a1 + a2 + 2*a3
	}
	return s;
};

Aes.addRoundKey = function (state, w, rnd, Nb) {  // xor Round Key into state S [§5.1.4]
	for (let r=0; r<4; r++) {
		for (let c=0; c<Nb; c++) state[r][c] ^= w[rnd*4+c][r];
	}
	return state;
};

Aes.subWord = function (w) {    // apply SBox to 4-byte word w
	for (let i=0; i<4; i++) w[i] = Aes.sBox[w[i]];
	return w;
};

Aes.rotWord = function (w) {    // rotate 4-byte word w left by one byte
	const tmp = w[0];

	for (let i=0; i<3; i++) w[i] = w[i+1];
	w[3] = tmp;
	return w;
};

// sBox is pre-computed multiplicative inverse in GF(2^8) used in subBytes and keyExpansion [§5.1.1]
Aes.sBox =  [0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
	0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
	0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
	0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
	0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
	0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
	0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
	0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
	0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
	0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
	0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
	0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
	0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
	0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
	0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
	0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16];

// rCon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
Aes.rCon = [ [0x00, 0x00, 0x00, 0x00],
	[0x01, 0x00, 0x00, 0x00],
	[0x02, 0x00, 0x00, 0x00],
	[0x04, 0x00, 0x00, 0x00],
	[0x08, 0x00, 0x00, 0x00],
	[0x10, 0x00, 0x00, 0x00],
	[0x20, 0x00, 0x00, 0x00],
	[0x40, 0x00, 0x00, 0x00],
	[0x80, 0x00, 0x00, 0x00],
	[0x1b, 0x00, 0x00, 0x00],
	[0x36, 0x00, 0x00, 0x00] ];


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  AES Counter-mode implementation in JavaScript (c) Chris Veness 2005-2012                      */
/*   - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf                       */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

Aes.Ctr = {};  // Aes.Ctr namespace: a subclass or extension of Aes

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  Base64 class: Base 64 encoding / decoding (c) Chris Veness 2002-2012                          */
/*    note: depends on Utf8 class                                                                 */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
const Base64 = {};  // Base64 namespace

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  Utf8 class: encode / decode between multi-byte Unicode characters and UTF-8 multiple          */
/*              single-byte character encoding (c) Chris Veness 2002-2012                         */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
const Utf8 = {};  // Utf8 namespace
/**
 * Encrypt a text using AES encryption in Counter mode of operation
 *
 * Unicode multi-byte character safe
 *
 * @param {String} plaintext Source text to be encrypted
 * @param {String} password  The password to use to generate a key
 * @param {Number} nBits     Number of bits to be used in the key (128, 192, or 256)
 * @returns {string}         Encrypted text
 */

Aes.Ctr.encrypt = function (plaintext, password, nBits) {
	let i;
	const blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES

	if (!(nBits===128 || nBits===192 || nBits===256)) return '';  // standard allows 128/192/256 bit keys

	plaintext = Utf8.encode(plaintext);
	password = Utf8.encode(password);
	//var t = new Date();  // timer

	// use AES itself to encrypt password to get cipher key (using plain password as source for key
	// expansion) - gives us well encrypted key (though hashed key might be preferred for prod'n use)
	const nBytes = nBits/8;  // no bytes in key (16/24/32)
	const pwBytes = new Array(nBytes);

	for (i = 0; i<nBytes; i++) {  // use 1st 16/24/32 chars of password for key
		pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
	}
	let key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes));  // gives us 16-byte key

	key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

	// initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A §B.2): [0-1] = millisec,
	// [2-3] = random, [4-7] = seconds, together giving full sub-millisec uniqueness up to Feb 2106
	const counterBlock = new Array(blockSize);

	const nonce = (new Date()).getTime();  // timestamp: milliseconds since 1-Jan-1970
	const nonceMs = nonce%1000;
	const nonceSec = Math.floor(nonce/1000);
	const nonceRnd = Math.floor(Math.random()*0xffff);

	for (i = 0; i<2; i++) counterBlock[i]   = (nonceMs  >>> i*8) & 0xff;
	for (i = 0; i<2; i++) counterBlock[i+2] = (nonceRnd >>> i*8) & 0xff;
	for (i = 0; i<4; i++) counterBlock[i+4] = (nonceSec >>> i*8) & 0xff;

	// and convert it to a string to go on the front of the ciphertext
	let ctrTxt = '';

	for (i = 0; i<8; i++) ctrTxt += String.fromCharCode(counterBlock[i]);

	// generate key schedule - an expansion of the key into distinct Key Rounds for each round
	const keySchedule = Aes.keyExpansion(key);

	const blockCount = Math.ceil(plaintext.length/blockSize);
	const ciphertxt = new Array(blockCount);  // ciphertext as array of strings

	for (let b=0; b<blockCount; b++) {
		// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
		let c;
		// done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)

		for (c = 0; c<4; c++) counterBlock[15-c] = (b >>> c*8) & 0xff;
		for (c = 0; c<4; c++) counterBlock[15-c-4] = (b/0x100000000 >>> c*8);

		const cipherCntr = Aes.cipher(counterBlock, keySchedule);  // -- encrypt counter block --

		// block size is reduced on final block
		const blockLength = b<blockCount-1 ? blockSize : (plaintext.length-1)%blockSize+1;
		const cipherChar = new Array(blockLength);

		for (i = 0; i<blockLength; i++) {  // -- xor plaintext with ciphered counter char-by-char --
			cipherChar[i] = cipherCntr[i] ^ plaintext.charCodeAt(b*blockSize+i);
			cipherChar[i] = String.fromCharCode(cipherChar[i]);
		}
		ciphertxt[b] = cipherChar.join('');
	}

	// Array.join is more efficient than repeated string concatenation in IE
	let ciphertext = ctrTxt + ciphertxt.join('');

	ciphertext = Base64.encode(ciphertext);  // encode in base64

	//alert((new Date()) - t);
	return ciphertext;
};

/**
 * Decrypt a text encrypted by AES in counter mode of operation
 *
 * @param {String} ciphertext Source text to be encrypted
 * @param {String} password   The password to use to generate a key
 * @param {Number} nBits      Number of bits to be used in the key (128, 192, or 256)
 * @returns {String}          Decrypted text
 */
Aes.Ctr.decrypt = function (ciphertext, password, nBits) {
	let b;
	let i;
	const blockSize = 16;  // block size fixed at 16 bytes / 128 bits (Nb=4) for AES

	if (!(nBits===128 || nBits===192 || nBits===256)) return '';  // standard allows 128/192/256 bit keys

	ciphertext = Base64.decode(ciphertext);
	password = Utf8.encode(password);
	//var t = new Date();  // timer

	// use AES to encrypt password (mirroring encrypt routine)
	const nBytes = nBits/8;  // no bytes in key
	const pwBytes = new Array(nBytes);

	for (i = 0; i<nBytes; i++) {
		pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
	}
	let key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes));

	key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

	// recover nonce from 1st 8 bytes of ciphertext
	const counterBlock = new Array(8);

	let ctrTxt = ciphertext.slice(0, 8);
	for (i = 0; i<8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);

	// generate key schedule
	const keySchedule = Aes.keyExpansion(key);

	// separate ciphertext into blocks (skipping past initial 8 bytes)
	const nBlocks = Math.ceil((ciphertext.length-8) / blockSize);
	const ct = new Array(nBlocks);

	for (b = 0; b<nBlocks; b++) ct[b] = ciphertext.slice(8+b*blockSize, 8+b*blockSize+blockSize);
	ciphertext = ct;  // ciphertext is now array of block-length strings

	// plaintext will get generated block-by-block into array of block-length strings
	const plaintxt = new Array(ciphertext.length);

	for (b = 0; b<nBlocks; b++) {
		let c;
		// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)

		for (c = 0; c<4; c++) counterBlock[15-c] = ((b) >>> c*8) & 0xff;
		for (c = 0; c<4; c++) counterBlock[15-c-4] = (((b+1)/0x100000000-1) >>> c*8) & 0xff;

		const cipherCntr = Aes.cipher(counterBlock, keySchedule);  // encrypt counter block

		const plaintxtByte = new Array(ciphertext[b].length);

		for (i = 0; i<ciphertext[b].length; i++) {
			// -- xor plaintxt with ciphered counter byte-by-byte --
			plaintxtByte[i] = cipherCntr[i] ^ ciphertext[b].charCodeAt(i);
			plaintxtByte[i] = String.fromCharCode(plaintxtByte[i]);
		}
		plaintxt[b] = plaintxtByte.join('');
	}

	// join array of blocks into single plaintext string
	let plaintext = plaintxt.join('');

	plaintext = Utf8.decode(plaintext);  // decode from UTF8 back to Unicode multi-byte chars

	//alert((new Date()) - t);
	return plaintext;
};

Base64.code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

/**
 * Encode string into Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
 * (instance method extending String object). As per RFC 4648, no newlines are added.
 *
 * @param {String} str The string to be encoded as base-64
 * @param {Boolean} [utf8encode=false] Flag to indicate whether str is Unicode string to be encoded
 *   to UTF8 before conversion to base64; otherwise string is assumed to be 8-bit characters
 * @returns {String} Base64-encoded string
 */
Base64.encode = function (str, utf8encode) {  // http://tools.ietf.org/html/rfc4648
	utf8encode =  (typeof utf8encode === 'undefined') ? false : utf8encode;
	let o1; let o2; let o3; let bits; let h1; let h2; let h3; let h4; const e=[]; let pad = ''; let c; let plain; let coded;
	const b64 = Base64.code;

	plain = utf8encode ? str.encodeUTF8() : str;

	c = plain.length % 3;  // pad string to length of multiple of 3

	if (c > 0) {
		while (c++ < 3) {
			pad += '='; plain += '\0';
		}
	}
	// note: doing padding here saves us doing special-case packing for trailing 1 or 2 chars

	for (c=0; c<plain.length; c+=3) {  // pack three octets into four hexets
		o1 = plain.charCodeAt(c);
		o2 = plain.charCodeAt(c+1);
		o3 = plain.charCodeAt(c+2);

		bits = o1<<16 | o2<<8 | o3;

		h1 = bits>>18 & 0x3f;
		h2 = bits>>12 & 0x3f;
		h3 = bits>>6 & 0x3f;
		h4 = bits & 0x3f;

		// use hextets to index into code string
		e[c/3] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
	}
	coded = e.join('');  // join() is far faster than repeated string concatenation in IE

	// replace 'A's from padded nulls with '='s
	coded = coded.slice(0, coded.length-pad.length) + pad;

	return coded;
};

/**
 * Decode string from Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
 * (instance method extending String object). As per RFC 4648, newlines are not catered for.
 *
 * @param {String} str The string to be decoded from base-64
 * @param {Boolean} [utf8decode=false] Flag to indicate whether str is Unicode string to be decoded
 *   from UTF8 after conversion from base64
 * @returns {String} decoded string
 */
Base64.decode = function (str, utf8decode) {
	utf8decode =  (typeof utf8decode === 'undefined') ? false : utf8decode;
	let o1; let o2; let o3; let h1; let h2; let h3; let h4; let bits; const d=[]; let plain; let coded;
	const b64 = Base64.code;

	coded = utf8decode ? str.decodeUTF8() : str;


	for (let c=0; c<coded.length; c+=4) {  // unpack four hexets into three octets
		h1 = b64.indexOf(coded.charAt(c));
		h2 = b64.indexOf(coded.charAt(c+1));
		h3 = b64.indexOf(coded.charAt(c+2));
		h4 = b64.indexOf(coded.charAt(c+3));

		bits = h1<<18 | h2<<12 | h3<<6 | h4;

		o1 = bits>>>16 & 0xff;
		o2 = bits>>>8 & 0xff;
		o3 = bits & 0xff;

		d[c/4] = String.fromCharCode(o1, o2, o3);

		// check for padding
		if (h4 === 0x40) d[c/4] = String.fromCharCode(o1, o2);

		if (h3 === 0x40) d[c/4] = String.fromCharCode(o1);
	}
	plain = d.join('');  // join() is far faster than repeated string concatenation in IE

	return utf8decode ? plain.decodeUTF8() : plain;
};

/**
 * Encode multi-byte Unicode string into utf-8 multiple single-byte characters
 * (BMP / basic multilingual plane only)
 *
 * Chars in range U+0080 - U+07FF are encoded in 2 chars, U+0800 - U+FFFF in 3 chars
 *
 * @param {String} strUni Unicode string to be encoded as UTF-8
 * @returns {String} encoded string
 */
Utf8.encode = function (strUni) {
	// use regular expressions & String.replace callback function for better efficiency
	// than procedural approaches
	let strUtf = strUni.replace(
		/[\u0080-\u07ff]/g,  // U+0080 - U+07FF => 2 bytes 110yyyyy, 10zzzzzz
		function (c) {
			const cc = c.charCodeAt(0);

			return String.fromCharCode(0xc0 | cc>>6, 0x80 | cc&0x3f);
		}
	);

	strUtf = strUtf.replace(
		/[\u0800-\uffff]/g,  // U+0800 - U+FFFF => 3 bytes 1110xxxx, 10yyyyyy, 10zzzzzz
		function (c) {
			const cc = c.charCodeAt(0);

			return String.fromCharCode(0xe0 | cc>>12, 0x80 | cc>>6&0x3F, 0x80 | cc&0x3f);
		}
	);
	return strUtf;
};

/**
 * Decode utf-8 encoded string back into multi-byte Unicode characters
 *
 * @param {String} strUtf UTF-8 string to be decoded back to Unicode
 * @returns {String} decoded string
 */
Utf8.decode = function (strUtf) {
	// note: decode 3-byte chars first as decoded 2-byte strings could appear to be 3-byte char!
	let strUni = strUtf.replace(
		/[\u00e0-\u00ef][\u0080-\u00bf][\u0080-\u00bf]/g,  // 3-byte chars
		function (c) {  // (note parentheses for precence)
			const cc = ((c.charCodeAt(0)&0x0f)<<12) | ((c.charCodeAt(1)&0x3f)<<6) | (c.charCodeAt(2)&0x3f);

			return String.fromCharCode(cc);
		}
	);

	strUni = strUni.replace(
		/[\u00c0-\u00df][\u0080-\u00bf]/g,                 // 2-byte chars
		function (c) {  // (note parentheses for precence)
			const cc = (c.charCodeAt(0)&0x1f)<<6 | c.charCodeAt(1)&0x3f;

			return String.fromCharCode(cc);
		}
	);
	return strUni;
};

export {Aes, Base64, Utf8};