//     uuid.js
//
//     Copyright (c) 2010-2012 Robert Kieffer
//     MIT License - http://opensource.org/licenses/mit-license.php
define(
    [],
    function () {
        'use strict';

        var _window = 'undefined' !== typeof window ? window : null;

        // Unique ID creation requires a high quality random # generator. We
        // feature
        // detect to determine the best RNG source, normalizing to a function
        // that
        // returns 128-bits of randomness, since that's what's usually required
        var _rng, _mathRNG, _nodeRNG, _whatwgRNG, _previousRoot;

        function setupBrowser() {
            // Allow for MSIE11 msCrypto
            var _crypto = _window.crypto || _window.msCrypto;

            if (!_rng && _crypto && _crypto.getRandomValues) {
                // WHATWG crypto-based RNG - http://wiki.whatwg.org/wiki/Crypto
                //
                // Moderately fast, high quality
                try {
                    var _rnds8 = new Uint8Array(16);
                    _whatwgRNG = _rng = function whatwgRNG() {
                        _crypto.getRandomValues(_rnds8);
                        return _rnds8;
                    };
                    _rng();
                } catch (e) {}
            }

            if (!_rng) {
                // Math.random()-based (RNG)
                //
                // If all else fails, use Math.random(). It's fast, but is of
                // unspecified
                // quality.
                var _rnds = new Array(16);
                _mathRNG = _rng = function () {
                    for (var i = 0, r; i < 16; i++) {
                        if ((i & 0x03) === 0) {
                            r = Math.random() * 0x100000000;
                        }
                        _rnds[i] = r >>> ((i & 0x03) << 3) & 0xff;
                    }

                    return _rnds;
                };
                if ('undefined' !== typeof console && console.warn) {
                    console
                        .warn("[SECURITY] node-uuid: crypto not usable, falling back to insecure Math.random()");
                }
            }
        }

        function setupNode() {
            // Node.js crypto-based RNG -
            // http://nodejs.org/docs/v0.6.2/api/crypto.html
            //
            // Moderately fast, high quality
            if ('function' === typeof require) {
                try {
                    var _rb = require('crypto').randomBytes;
                    _nodeRNG = _rng = _rb && function () {
                        return _rb(16);
                    };
                    _rng();
                } catch (e) {}
            }
        }

        if (_window) {
            setupBrowser();
        } else {
            setupNode();
        }

        // Buffer class to use
        var BufferClass = ('function' === typeof Buffer) ? Buffer : Array;

        // Maps for number <-> hex string conversion
        var _byteToHex = [];
        var _hexToByte = {};
        for (var i = 0; i < 256; i++) {
            _byteToHex[i] = (i + 0x100).toString(16).substr(1);
            _hexToByte[_byteToHex[i]] = i;
        }

        // **`parse()` - Parse a UUID into it's component bytes**
        function parse(s, buf, offset) {
            var i = (buf && offset) || 0,
                ii = 0;

            buf = buf || [];
            s.toLowerCase().replace(/[0-9a-f]{2}/g, function (oct) {
                if (ii < 16) { // Don't overflow!
                    buf[i + ii++] = _hexToByte[oct];
                }
            });

            // Zero out remaining bytes if string was short
            while (ii < 16) {
                buf[i + ii++] = 0;
            }

            return buf;
        }

        // **`unparse()` - Convert UUID byte array (ala parse()) into a string**
        function unparse(buf, offset) {
            var i = offset || 0,
                bth = _byteToHex;
            return bth[buf[i++]] + bth[buf[i++]] + bth[buf[i++]] +
                bth[buf[i++]] + '-' + bth[buf[i++]] + bth[buf[i++]] + '-' +
                bth[buf[i++]] + bth[buf[i++]] + '-' + bth[buf[i++]] +
                bth[buf[i++]] + '-' + bth[buf[i++]] + bth[buf[i++]] +
                bth[buf[i++]] + bth[buf[i++]] + bth[buf[i++]] + bth[buf[i++]];
        }

        // **`v1()` - Generate time-based UUID**
        //
        // Inspired by https://github.com/LiosK/UUID.js
        // and http://docs.python.org/library/uuid.html

        // random #'s we need to init node and clockseq
        var _seedBytes = _rng();

        // Per 4.5, create and 48-bit node id, (47 random bits + multicast bit =
        // 1)
        var _nodeId = [
            _seedBytes[0] | 0x01,
            _seedBytes[1],
            _seedBytes[2],
            _seedBytes[3],
            _seedBytes[4],
            _seedBytes[5]
        ];

        // Per 4.2.2, randomize (14 bit) clockseq
        var _clockseq = (_seedBytes[6] << 8 | _seedBytes[7]) & 0x3fff;

        // Previous uuid creation time
        var _lastMSecs = 0,
            _lastNSecs = 0;

        // See https://github.com/broofa/node-uuid for API details
        function v1(options, buf, offset) {
            var i = buf && offset || 0;
            var b = buf || [];

            options = options || {};

            var clockseq = (options.clockseq != null) ? options.clockseq : _clockseq;

            // UUID timestamps are 100 nano-second units since the Gregorian
            // epoch,
            // (1582-10-15 00:00). JSNumbers aren't precise enough for this, so
            // time is handled internally as 'msecs' (integer milliseconds) and
            // 'nsecs'
            // (100-nanoseconds offset from msecs) since unix epoch, 1970-01-01
            // 00:00.
            var msecs = (options.msecs != null) ? options.msecs : new Date()
                .getTime();

            // Per 4.2.1.2, use count of uuid's generated during the current
            // clock
            // cycle to simulate higher resolution clock
            var nsecs = (options.nsecs != null) ? options.nsecs : _lastNSecs + 1;

            // Time since last uuid creation (in msecs)
            var dt = (msecs - _lastMSecs) + (nsecs - _lastNSecs) / 10000;

            // Per 4.2.1.2, Bump clockseq on clock regression
            if (dt < 0 && options.clockseq == null) {
                clockseq = clockseq + 1 & 0x3fff;
            }

            // Reset nsecs if clock regresses (new clockseq) or we've moved onto
            // a new
            // time interval
            if ((dt < 0 || msecs > _lastMSecs) && options.nsecs == null) {
                nsecs = 0;
            }

            // Per 4.2.1.2 Throw error if too many uuids are requested
            if (nsecs >= 10000) {
                throw new Error(
                    'uuid.v1(): Can\'t create more than 10M uuids/sec');
            }

            _lastMSecs = msecs;
            _lastNSecs = nsecs;
            _clockseq = clockseq;

            // Per 4.1.4 - Convert from unix epoch to Gregorian epoch
            msecs += 12219292800000;

            // `time_low`
            var tl = ((msecs & 0xfffffff) * 10000 + nsecs) % 0x100000000;
            b[i++] = tl >>> 24 & 0xff;
            b[i++] = tl >>> 16 & 0xff;
            b[i++] = tl >>> 8 & 0xff;
            b[i++] = tl & 0xff;

            // `time_mid`
            var tmh = (msecs / 0x100000000 * 10000) & 0xfffffff;
            b[i++] = tmh >>> 8 & 0xff;
            b[i++] = tmh & 0xff;

            // `time_high_and_version`
            b[i++] = tmh >>> 24 & 0xf | 0x10; // include version
            b[i++] = tmh >>> 16 & 0xff;

            // `clock_seq_hi_and_reserved` (Per 4.2.2 - include variant)
            b[i++] = clockseq >>> 8 | 0x80;

            // `clock_seq_low`
            b[i++] = clockseq & 0xff;

            // `node`
            var node = options.node || _nodeId;
            for (var n = 0; n < 6; n++) {
                b[i + n] = node[n];
            }

            return buf ? buf : unparse(b);
        }

        // **`v4()` - Generate random UUID**

        // See https://github.com/broofa/node-uuid for API details
        function v4(options, buf, offset) {
            // Deprecated - 'format' argument, as supported in v1.2
            var i = buf && offset || 0;

            if (typeof (options) === 'string') {
                buf = (options === 'binary') ? new BufferClass(16) : null;
                options = null;
            }
            options = options || {};

            var rnds = options.random || (options.rng || _rng)();

            // Per 4.4, set bits for version and `clock_seq_hi_and_reserved`
            rnds[6] = (rnds[6] & 0x0f) | 0x40;
            rnds[8] = (rnds[8] & 0x3f) | 0x80;

            // Copy bytes to buffer, if provided
            if (buf) {
                for (var ii = 0; ii < 16; ii++) {
                    buf[i + ii] = rnds[ii];
                }
            }

            return buf || unparse(rnds);
        }

        // Export public API
        var uuid = function() {
            return new String(v4());
        };
        uuid.v1 = v1;
        uuid.v4 = v4;
        uuid.create = v4;
        uuid.empty = "00000000-0000-0000-0000-000000000000";
        uuid.parse = parse;
        uuid.unparse = unparse;
        uuid.BufferClass = BufferClass;
        uuid._rng = _rng;
        uuid._mathRNG = _mathRNG;
        uuid._nodeRNG = _nodeRNG;
        uuid._whatwgRNG = _whatwgRNG;

        return uuid;
    });