function arrayToHex(iv) {
  let hexStr = '';
  for (const i in iv) {
    if (iv[i] < 16) {
      hexStr += '0' + iv[i].toString(16);
    } else {
      hexStr += iv[i].toString(16);
    }
  }
  return hexStr;
}

function hexToArray(str) {
  const iv = new Uint8Array(str.length / 2);
  for (let i = 0; i < str.length; i += 2) {
    iv[i / 2] = parseInt(str.charAt(i) + str.charAt(i + 1), 16);
  }

  return iv;
}

function notify(str) {
  if (!('Notification' in window)) {
    return;
  } else if (Notification.permission === 'granted') {
    new Notification(str);
  } else if (Notification.permission !== 'denied') {
    Notification.requestPermission(function(permission) {
      if (permission === 'granted') new Notification(str);
    });
  }
}

function gcmCompliant() {
  try {
    return window.crypto.subtle.generateKey(
      {
        name: 'AES-GCM',
        length: 128
      },
      true,
      ['encrypt', 'decrypt']
    ).then(key => {
      return window.crypto.subtle.encrypt(
        {
          name: 'AES-GCM',
          iv: window.crypto.getRandomValues(new Uint8Array(12)),
          additionalData: window.crypto.getRandomValues(new Uint8Array(6)),
          tagLength: 128
        },
        key,
        new ArrayBuffer(8)
      )
      .then(() => {
        return Promise.resolve()
      })
      .catch(err => {
        return Promise.reject()
      })
    }).catch(err => {
      return Promise.reject();
    })
  } catch(err) {
    return Promise.reject();
  }
}

module.exports = {
  arrayToHex,
  hexToArray,
  notify,
  gcmCompliant
};