export async function signMessage(
  message: string,
  secret: string
): Promise<string> {
  const encoder = new TextEncoder();
  const key = await window.crypto.subtle.importKey(
    'raw',
    encoder.encode(secret),
    { name: 'HMAC', hash: { name: 'SHA-256' } },
    false,
    ['sign']
  );

  const signature = await window.crypto.subtle.sign(
    'HMAC',
    key,
    encoder.encode(message)
  );

  return Array.prototype.map
    .call(new Uint8Array(signature), (x: any) =>
      ('00' + x.toString(16)).slice(-2)
    )
    .join('');
}