(function (exports) {
'use strict';

var Unibabel = exports.Unibabel;

// Generate a key
function generateOtpKey() {
  // 20 cryptographically random binary bytes (160-bit key)
  var key = window.crypto.getRandomValues(new Uint8Array(20));

  return key;
}

// Text-encode the key as base32 (in the style of Google Authenticator - same as Facebook, Microsoft, etc)
function encodeGoogleAuthKey(bin) {
  // 32 ascii characters without trailing '='s
  var base32 = Unibabel.bufferToBase32(bin).replace(/=/g, '');

  // lowercase with a space every 4 characters
  var key = base32.toLowerCase().replace(/(\w{4})/g, "$1 ").trim();

  return key;
}

function generateGoogleAuthKey() {
  return encodeGoogleAuthKey(generateOtpKey());
}

// Binary-decode the key from base32 (Google Authenticator, FB, M$, etc)
function decodeGoogleAuthKey(key) {
  // decode base32 google auth key to binary
  var unformatted = key.replace(/\W+/g, '').toUpperCase();
  var bin = Unibabel.base32ToBuffer(unformatted);

  return bin;
}

// Generate a Google Auth Token
function generateGoogleAuthToken(key) {
  var bin = decodeGoogleAuthKey(key);
  var totp = exports.totp || require('notp').totp;

  return totp.gen(bin);
}

// Verify a Google Auth Token
function verifyGoogleAuthToken(key, token) {
  var bin = decodeGoogleAuthKey(key);
  var totp = exports.totp || require('notp').totp;

  token = token.replace(/\W+/g, '');

  // window is +/- 1 period of 30 seconds
  return totp.verify(token, bin, { window: 1, time: 30 });
}

exports.generateKey = generateGoogleAuthKey;
exports.generateToken = generateGoogleAuthToken;
exports.verifyToken = verifyGoogleAuthToken;

//var key = exports.generateKey();
var key = 'hxdm vjec jjws rb3h wizr 4ifu gftm xboz';
console.log('key', key);
exports.generateToken(key).then(function (token) {
  console.log('token', token);

  exports.verifyToken(key, token).then(function (result) {
    console.log('verify', result);
  });
});

}(
  'undefined' !== typeof window ? window : module.exports
));