/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  SHA-256 implementation in JavaScript                              (c) Chris Veness 2002-2014  */
/*                                                                                                */
/*  - see http://csrc.nist.gov/groups/ST/toolkit/secure_hashing.html                              */
/*        http://csrc.nist.gov/groups/ST/toolkit/examples.html                                    */
/*                                                                                                */
/* @source http://www.movable-type.co.uk/scripts/sha256.html                                      */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/**
 *  @umd AMD, Browser, CommonJs, noDeps
 */
(function(name, root, String, Array, Math) {
    /* jshint node:true *//* global define, escape, unescape */
    'use strict';

    (typeof define !== 'function' || !define.amd
        ? typeof module == 'undefined' || !module.exports
            ? function (deps, factory) { root[name] = factory(); } // Browser
            : function (deps, factory) { module.exports = factory(); } // CommonJs
        : define // AMD
    )
    /*define*/(/*name, */[], function factory() {

        /**
         * SHA-256 hash function reference implementation.
         *
         * @namespace
         */
        var Sha256 = function sha256(str, isByteStream) { return Sha256.hash(str, isByteStream); };

        /** Extend String object with method to encode multi-byte string to utf8
         *  - http://monsur.hossa.in/2012/07/20/utf-8-in-javascript.html */
        var utf8Encode = function(str) { return unescape( encodeURIComponent( str ) ); };

        var hasMultibyteRE = /[^\x00-\xFF]/;

        /**
         * Generates SHA-256 hash of string.
         *
         * @param   {string} msg - String to be hashed
         * @returns {string} Hash of msg as hex character string
         */
        Sha256.hash = function(msg, isByteStream) {
            if(isByteStream == undefined) {
                isByteStream = !hasMultibyteRE.test(msg);
            }

            // if msg has multi-byte chars, convert it to UTF-8, as SHA only deals with byte-streams
            msg = isByteStream ? msg : utf8Encode(msg);

            // constants [§4.2.2]
            var K = [
                0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
                0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
                0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
                0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
                0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
                0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
                0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
                0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
            ];
            // initial hash value [§5.3.1]
            var H = [
                0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
            ];

            // PREPROCESSING

            msg += String.fromCharCode(0x80);  // add trailing '1' bit (+ 0's padding) to string [§5.1.1]

            // convert string msg into 512-bit/16-integer blocks arrays of ints [§5.2.1]
            var l = msg.length/4 + 2; // length (in 32-bit integers) of msg + ‘1’ + appended length
            var N = Math.ceil(l/16);  // number of 16-integer-blocks required to hold 'l' ints
            var M = new Array(N);

            for (var i=0; i<N; i++) {
                M[i] = new Array(16);
                for (var j=0; j<16; j++) {  // encode 4 chars per integer, big-endian encoding
                    M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) |
                              (msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));
                } // note running off the end of msg is ok 'cos bitwise ops on NaN return 0
            }
            // add length (in bits) into final pair of 32-bit integers (big-endian) [§5.1.1]
            // note: most significant word would be (len-1)*8 >>> 32, but since JS converts
            // bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
            M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14]);
            M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;


            // HASH COMPUTATION [§6.1.2]

            var W = new Array(64); var a, b, c, d, e, f, g, h;
            for (var i=0; i<N; i++) {

                // 1 - prepare message schedule 'W'
                for (var t=0;  t<16; t++) W[t] = M[i][t];
                for (var t=16; t<64; t++) W[t] = (Sha256.σ1(W[t-2]) + W[t-7] + Sha256.σ0(W[t-15]) + W[t-16]) & 0xffffffff;

                // 2 - initialise working variables a, b, c, d, e, f, g, h with previous hash value
                a = H[0]; b = H[1]; c = H[2]; d = H[3]; e = H[4]; f = H[5]; g = H[6]; h = H[7];

                // 3 - main loop (note 'addition modulo 2^32')
                for (var t=0; t<64; t++) {
                    var T1 = h + Sha256.Σ1(e) + Sha256.Ch(e, f, g) + K[t] + W[t];
                    var T2 =     Sha256.Σ0(a) + Sha256.Maj(a, b, c);
                    h = g;
                    g = f;
                    f = e;
                    e = (d + T1) & 0xffffffff;
                    d = c;
                    c = b;
                    b = a;
                    a = (T1 + T2) & 0xffffffff;
                }
                 // 4 - compute the new intermediate hash value (note 'addition modulo 2^32')
                H[0] = (H[0]+a) & 0xffffffff;
                H[1] = (H[1]+b) & 0xffffffff;
                H[2] = (H[2]+c) & 0xffffffff;
                H[3] = (H[3]+d) & 0xffffffff;
                H[4] = (H[4]+e) & 0xffffffff;
                H[5] = (H[5]+f) & 0xffffffff;
                H[6] = (H[6]+g) & 0xffffffff;
                H[7] = (H[7]+h) & 0xffffffff;
            }

            return Sha256.toHexStr(H[0]) + Sha256.toHexStr(H[1]) + Sha256.toHexStr(H[2]) + Sha256.toHexStr(H[3]) +
                   Sha256.toHexStr(H[4]) + Sha256.toHexStr(H[5]) + Sha256.toHexStr(H[6]) + Sha256.toHexStr(H[7]);
        };


        /**
         * Rotates right (circular right shift) value x by n positions [§3.2.4].
         * @private
         */
        Sha256.ROTR = function(n, x) {
            return (x >>> n) | (x << (32-n));
        };

        /**
         * Logical functions [§4.1.2].
         * @private
         */
        Sha256.Σ0  = function(x) { return Sha256.ROTR(2,  x) ^ Sha256.ROTR(13, x) ^ Sha256.ROTR(22, x); };
        Sha256.Σ1  = function(x) { return Sha256.ROTR(6,  x) ^ Sha256.ROTR(11, x) ^ Sha256.ROTR(25, x); };
        Sha256.σ0  = function(x) { return Sha256.ROTR(7,  x) ^ Sha256.ROTR(18, x) ^ (x>>>3);  };
        Sha256.σ1  = function(x) { return Sha256.ROTR(17, x) ^ Sha256.ROTR(19, x) ^ (x>>>10); };
        Sha256.Ch  = function(x, y, z) { return (x & y) ^ (~x & z); };
        Sha256.Maj = function(x, y, z) { return (x & y) ^ (x & z) ^ (y & z); };


        /**
         * Hexadecimal representation of a number.
         * @private
         */
        Sha256.toHexStr = function(n) {
            // note can't use toString(16) as it is implementation-dependant,
            // and in IE returns signed numbers when used on full words
            var s="", v;
            for (var i=7; i>=0; i--) { v = (n>>>(i*4)) & 0xf; s += v.toString(16); }
            return s;
        };


        /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
        // String.prototype.sha256()
        Sha256._proto_ =
        String.prototype.sha256 = function (isByteStream) { return Sha256.hash(this, isByteStream) }

        return Sha256;
    });

    /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
}
('sha256', this, String, Array, Math));

