//     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;
});