Go into the off-chain folder

cd off-chain

Install dependencies

npm i

Run the tests. Make sure you are running Node Version 19 and above

npm run test

To ensure that only the owner of the UTxO can consume it we need to check if the transaction is signed by the owner. We will store it in the datum of the UTxO and the smart contract simply needs to check that the signature is in the transaction to approve it.

The validator looks for the signtures in the transaction and compares it with the owner pub key hash in the datum

let must_be_signed_by_owner =
    list.has(ctx.transaction.extra_signatories, datum.owner_address_hash)
must_be_signed_by_owner

Create a function that gets all available UTxOs locked up in the contract by the owner.

export async function getOwnerUTxOsAtScript(
  ownerPubKeyHash: string,
  lucid: Lucid
) {
  const { validatorAddress } = getValidators(lucid);
  const utxos = await lucid.utxosAt(validatorAddress);

  const availableOffers = utxos.filter((utxo) => {
    try {
      const datum = Data.castFrom(
        Data.from(utxo.datum as string),
        OwnerConsumeDatum
      );
      return datum.ownerPubKeyHash === ownerPubKeyHash;
    } catch (error) {
      return false;
    }
  });

  return availableOffers;
}

The function to consume the transaction will take in two parameters. One of the UTxOs that can be consumed and the other owner public key hash. The function needs to make sure it has added the owner's signature to the transaction.