Cognito presignup lambda function for Polkadot authentication

PolkaPresignupLambda.js

const aws = require("aws-sdk");
const Sentry = require("@sentry/node");
const { signatureVerify } = require('@polkadot/util-crypto');
const { decodeAddress, encodeAddress } = require('@polkadot/keyring');
const { hexToU8a, isHex } = require('@polkadot/util');

exports.handler = async (event) => {
  event.response.autoConfirmUser = true;
  try {
    console.log('Verifying address format')
    const isAddressValid = isValidAddressPolkadotAddress(event.userName)
    if (!isAddressValid) {
      const e = new Error("Invalid address")
      handleError(e)
    }
    console.log('Verifying signed key')
    const { isValid } = signatureVerify(key, signedKey, event.userName);
    if (!isValid) {
      const e = new Error("Invalid signature")
    }
  } catch (e) {
    console.error(e)
    throw e
  }
  return event;
};

function isValidAddressPolkadotAddress(address) {
  try {
    encodeAddress(
      isHex(address)
        ? hexToU8a(address)
        : decodeAddress(address)
    );
    return true;

  } catch (error) {
    return false;
  }
}