// Load modules

var Crypto = require('crypto'); var Boom = require('boom');

// Declare internals

var internals = {};

// Generate a cryptographically strong pseudo-random data

exports.randomString = function (size) {

var buffer = exports.randomBits((size + 1) * 6);
if (buffer instanceof Error) {
    return buffer;
}

var string = buffer.toString('base64').replace(/\+/g, '-').replace(/\//g, '_').replace(/\=/g, '');
return string.slice(0, size);

};

exports.randomBits = function (bits) {

if (!bits ||
    bits < 0) {

    return Boom.internal('Invalid random bits count');
}

var bytes = Math.ceil(bits / 8);
try {
    return Crypto.randomBytes(bytes);
}
catch (err) {
    return Boom.internal('Failed generating random bits: ' + err.message);
}

};

// Compare two strings using fixed time algorithm (to prevent time-based analysis of MAC digest match)

exports.fixedTimeComparison = function (a, b) {

if (typeof a !== 'string' ||
    typeof b !== 'string') {

    return false;
}

var mismatch = (a.length === b.length ? 0 : 1);
if (mismatch) {
    b = a;
}

for (var i = 0, il = a.length; i < il; ++i) {
    var ac = a.charCodeAt(i);
    var bc = b.charCodeAt(i);
    mismatch |= (ac ^ bc);
}

return (mismatch === 0);

};