Generating PreSignTxHashes for p2tr transaction

[shreyank4444]

Hi,
I am trying to generate preSignTxHashes for taproot transactions.
I am getting "Incorrect input parameter\nContext:\n0. Error creating UTXO from Protobuf" error for preImageOutput. Any help would be appreciated.

export const generateTaprootPreSignHashes = async (txObject: any) => {
  const walletCore = await initWasm()
  const { utxos, fromAddress, toAddress, outputAmmount, feeRate } = txObject

  const pubKey = localStorageService.generatedPublicKey.get()
  if (!pubKey) throw new Error('No public key found')
  const toXOnlyPubKey = pubKey.slice(2)

  const totalInputValue = utxos.reduce((sum, utxo) => sum + utxo.value, 0)
  const estimatedFee = feeRate * 250 // Estimate tx size
  const changeAmount = totalInputValue - outputAmmount - estimatedFee

  // Build UTXO inputs with correct scriptBuilder format
  const utxoInputs = utxos.map((utxo) =>
    TW.BitcoinV2.Proto.Input.create({
      outPoint: {
        hash: Buffer.from(utxo.txid, 'hex').reverse(),
        vout: utxo.vout,
      },
      value: new Long(utxo.value),
      sequence: {
        sequence: 4294967295,
      },
      scriptBuilder: {
        p2trKeyPath: Buffer.from(toXOnlyPubKey, 'hex'),
      },
    })
  )

  // Construct main output to recipient address
  const mainOutput = TW.BitcoinV2.Proto.Output.create({
    toAddress: toAddress,
    value: new Long(outputAmmount),
  })

  // Create change output
  const changeOutput = TW.BitcoinV2.Proto.Output.create({
    builder: {
      p2trKeyPath: Buffer.from(toXOnlyPubKey, 'hex'),
    },
  })

  // Create signing input with corrected structure
  const txInput = TW.BitcoinV2.Proto.SigningInput.create({
    builder: {
      version: TW.BitcoinV2.Proto.TransactionVersion.V2,
      inputs: [...utxoInputs],
      outputs: [mainOutput],
      changeOutput: changeOutput,
      feePerVb: new Long(feeRate),
      inputSelector: TW.BitcoinV2.Proto.InputSelector.SelectDescending,
      fixedDustThreshold: new Long(546),
    },
    chainInfo: {
      p2pkhPrefix: 0,
      p2shPrefix: 5,
    },
    dangerousUseFixedSchnorrRng: true,
  })

  const legacySigningInput = TW.Bitcoin.Proto.SigningInput.create({
    signingV2: txInput,
  })

  console.log('legacySigningInput', legacySigningInput)

  const encodedTx =
    TW.Bitcoin.Proto.SigningInput.encode(legacySigningInput).finish()

  console.log('encodedTx', encodedTx)

  const preimageOutputData = walletCore.TransactionCompiler.preImageHashes(
    walletCore.CoinType.bitcoin,
    encodedTx
  )

  console.log('preimageOutputData', preimageOutputData)

  const preimageOutput =
    TW.Bitcoin.Proto.PreSigningOutput.decode(preimageOutputData)

  console.log('preimageOutput', preimageOutput)

  if (preimageOutput.error || preimageOutput.errorMessage) {
    throw new Error(
      `Error generating pre-sign hashes: ${
        preimageOutput.errorMessage || `Code ${preimageOutput.error}`
      }`
    )
  }

  const preSignHashes = preimageOutput.hashPublicKeys.map(
    (hashPublicKey: any) => walletCore.HexCoding.encode(hashPublicKey.dataHash)
  )

  console.log('preSignHashes', preSignHashes)

  return preSignHashes
}