trying to write to snapchain w privy signer

gistfile1.txt

import { useState } from 'react';
import { ExternalEd25519Signer, HubRestAPIClient } from '@standard-crypto/farcaster-js';
import { useLogin, usePrivy, useFarcasterSigner } from '@privy-io/react-auth';

export default function Cast() {
  const [text, setText] = useState('');
  const { login } = useLogin();
  const { user } = usePrivy();
  const { getFarcasterSignerPublicKey, signFarcasterMessage, requestFarcasterSignerFromWarpcast } = useFarcasterSigner();

  const farcasterAccount = user?.linkedAccounts.find(
    (account) => account.type === 'farcaster'
  );

  async function sendCast() {
    if (!farcasterAccount) {
      console.log("No Farcaster account linked.");
      return;
    }

    const signer = new ExternalEd25519Signer(
      signFarcasterMessage,
      getFarcasterSignerPublicKey
    );

    const client = new HubRestAPIClient({
      // hubUrl: 'https://hub.pinata.cloud'
      hubUrl: 'https://snapchain-api.neynar.com',
    });

    try {
      const { hash } = await client.submitCast(
        { text },
        farcasterAccount?.fid || 4163,
        signer
      );
      console.log("Cast submitted with hash:", hash);
      setText("");
    } catch (err) {
      console.error("Error sending cast:", err);
    }
  }

  async function fetchSnapchainInfo() {
    try {
      const response = await fetch('https://snapchain-api.neynar.com/v1/info', {
        method: 'GET',
        headers: {
          'Content-Type': 'application/json',
          'x-api-key': process.env.NEXT_PUBLIC_NEYNAR_API_KEY!,
        },
      });

      const result = await response.json();
      console.log("Snapchain info:", result);
    } catch (error) {
      console.error("Failed to fetch Snapchain info:", error);
    }
  }

  return (
    <>
      <textarea value={text} onChange={(e) => setText(e.target.value)} />
      <button onClick={sendCast} disabled={!farcasterAccount}>Send Cast</button>
      <button
        onClick={() => requestFarcasterSignerFromWarpcast()}
        //disabled={!farcasterAccount || Boolean(farcasterAccount.signerPublicKey)}
      >
        Authorize my Farcaster signer from Warpcast
      </button>
      <button onClick={fetchSnapchainInfo}>Test Snapchain Info</button>
    </>
  );
}