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;