const Crypto = {};

(function(){

var base64map = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";


// Crypto utilities
var util = Crypto.util = {

	// Bit-wise rotate left
	rotl: function (n, b) {
		return (n << b) | (n >>> (32 - b));
	},

	// Bit-wise rotate right
	rotr: function (n, b) {
		return (n << (32 - b)) | (n >>> b);
	},

	// Swap big-endian to little-endian and vice versa
	endian: function (n) {

		// If number given, swap endian
		if (n.constructor == Number) {
			return util.rotl(n,  8) & 0x00FF00FF |
			       util.rotl(n, 24) & 0xFF00FF00;
		}

		// Else, assume array and swap all items
		for (var i = 0; i < n.length; i++)
			n[i] = util.endian(n[i]);
		return n;

	},

	// Generate an array of any length of random bytes
	randomBytes: function (n) {
		for (var bytes = []; n > 0; n--)
			bytes.push(Math.floor(Math.random() * 256));
		return bytes;
	},

	// Convert a string to a byte array
	stringToBytes: function (str) {
		var bytes = [];
		for (var i = 0; i < str.length; i++)
			bytes.push(str.charCodeAt(i));
		return bytes;
	},

	// Convert a byte array to a string
	bytesToString: function (bytes) {
		var str = [];
		for (var i = 0; i < bytes.length; i++)
			str.push(String.fromCharCode(bytes[i]));
		return str.join("");
	},

	// Convert a string to big-endian 32-bit words
	stringToWords: function (str) {
		var words = [];
		for (var c = 0, b = 0; c < str.length; c++, b += 8)
			words[b >>> 5] |= str.charCodeAt(c) << (24 - b % 32);
		return words;
	},

	// Convert a byte array to big-endian 32-bits words
	bytesToWords: function (bytes) {
		var words = [];
		for (var i = 0, b = 0; i < bytes.length; i++, b += 8)
			words[b >>> 5] |= bytes[i] << (24 - b % 32);
		return words;
	},

	// Convert big-endian 32-bit words to a byte array
	wordsToBytes: function (words) {
		var bytes = [];
		for (var b = 0; b < words.length * 32; b += 8)
			bytes.push((words[b >>> 5] >>> (24 - b % 32)) & 0xFF);
		return bytes;
	},

	// Convert a byte array to a hex string
	bytesToHex: function (bytes) {
		var hex = [];
		for (var i = 0; i < bytes.length; i++) {
			hex.push((bytes[i] >>> 4).toString(16));
			hex.push((bytes[i] & 0xF).toString(16));
		}
		return hex.join("");
	},

	// Convert a hex string to a byte array
	hexToBytes: function (hex) {
		var bytes = [];
		for (var c = 0; c < hex.length; c += 2)
			bytes.push(parseInt(hex.substr(c, 2), 16));
		return bytes;
	},

	// Convert a byte array to a base-64 string
	bytesToBase64: function (bytes) {

		// Use browser-native function if it exists
		// if (typeof btoa == "function") return btoa(util.bytesToString(bytes));

		var base64 = [],
		    overflow;

		for (var i = 0; i < bytes.length; i++) {
			switch (i % 3) {
				case 0:
					base64.push(base64map.charAt(bytes[i] >>> 2));
					overflow = (bytes[i] & 0x3) << 4;
					break;
				case 1:
					base64.push(base64map.charAt(overflow | (bytes[i] >>> 4)));
					overflow = (bytes[i] & 0xF) << 2;
					break;
				case 2:
					base64.push(base64map.charAt(overflow | (bytes[i] >>> 6)));
					base64.push(base64map.charAt(bytes[i] & 0x3F));
					overflow = -1;
			}
		}

		// Encode overflow bits, if there are any
		if (overflow != undefined && overflow != -1)
			base64.push(base64map.charAt(overflow));

		// Add padding
		while (base64.length % 4 != 0) base64.push("=");

		return base64.join("");

	},

	// Convert a base-64 string to a byte array
	base64ToBytes: function (base64) {

		// Use browser-native function if it exists
		if (typeof atob == "function") return util.stringToBytes(atob(base64));

		// Remove non-base-64 characters
		base64 = base64.replace(/[^A-Z0-9+\/]/ig, "");

		var bytes = [];

		for (var i = 0; i < base64.length; i++) {
			switch (i % 4) {
				case 1:
					bytes.push((base64map.indexOf(base64.charAt(i - 1)) << 2) |
					           (base64map.indexOf(base64.charAt(i)) >>> 4));
					break;
				case 2:
					bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 0xF) << 4) |
					           (base64map.indexOf(base64.charAt(i)) >>> 2));
					break;
				case 3:
					bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 0x3) << 6) |
					           (base64map.indexOf(base64.charAt(i))));
					break;
			}
		}

		return bytes;

	}

};

// Crypto mode namespace
Crypto.mode = {};

})();

module.exports = Crypto;