domotz-remote-pawn/src/utils/random.js

Domotz Agent

/** This file is part of Domotz Agent.
 * Copyright (C) 2016  Domotz Ltd
 *
 * Domotz Agent is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Domotz Agent is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Domotz Agent.  If not, see <http://www.gnu.org/licenses/>.
 **/
/**
 * Created by Tommaso Latini <tommaso@domotz.com> on 28/12/15.
 */

const MODULE = 'RANDOM';
var factory = function (crypto) {

    function md5(data) {
        return crypto.createHash('md5').update(data).digest("hex");
    }

    function getRandomBytes(n, encoding) {
        var randomStr;
        try {
            var rnd = crypto.randomBytes(n);
            randomStr = rnd.toString(encoding);
            console.debug('%s - Have %d bytes of random data', MODULE, rnd.length, rnd);
        } catch (ex) {
            console.error(ex.stack); // most likely, entropy sources are drained
            throw(ex);
        }
        return randomStr;
    }

    function randomNumberFromString(str, start, end){
        var currentVal,
            res = start,
            range = end - start + 1,
            input = md5(str);

        console.verbose('%s - Input: %s. Original String: %s. Range: %s', MODULE, input, str, range);

        for(var i = 0; range >= 1.0; i++) {
            currentVal = parseInt(input.charAt(i), 16);
            range  = range/16.0;
            res += currentVal * range;
            console.silly('%s -   %s] Range: %s. Current Value: %s', MODULE, i+1, range, currentVal);
        }

        var number = Math.round(res);

        console.debug('%s - Obtain pseudo random number %s from %s to %s', MODULE, number, start, end);

        return number;
    }

    return {
        md5: md5,
        getRandomBytes: getRandomBytes,
        randomNumberFromString: randomNumberFromString
    };

};

module.exports.factory = factory;