_adaWalletTest.js

const CardanoWasm = require('@emurgo/cardano-serialization-lib-nodejs')

// This isn't the actual private key for those UTXOs
const privateKeyHex = '4841ccc9e76666ddfebe6b5648013a60d9989b4445366c6307b071d9cd4fea54fecbec6fdf120a58a520f7b00efbdeef283d599a375914550a2f30cedb7b419a'

const privateKey = CardanoWasm.PrivateKey.from_extended_bytes(Buffer.from(privateKeyHex, 'hex'))
const publicKey = privateKey.to_public()
const publicKeyHash = publicKey.hash()
const enterpriseAddress = CardanoWasm.EnterpriseAddress.new(CardanoWasm.NetworkInfo.mainnet().network_id(), CardanoWasm.StakeCredential.from_keyhash(publicKeyHash))
const address = enterpriseAddress.to_address()

const bn = n => CardanoWasm.BigNum.from_str(BigInt(Number(n).toFixed(0)).toString())

// These normally come from cardano-graphql via { cardano { currentEpoch { protocolParams { ... } } } }
const minFeeA = bn(44)
const minFeeB = bn(155381)
const minUTxOValue = bn(1000000)
const poolDeposit = bn(500000000)
const keyDeposit = bn(2000000)

const txBuilder = CardanoWasm.TransactionBuilder.new(CardanoWasm.LinearFee.new(minFeeA, minFeeB), minUTxOValue, poolDeposit, keyDeposit)
console.log('Initial min. fee:', txBuilder.min_fee().to_str())

const adaTargetAddressObject = CardanoWasm.Address.from_bech32('addr1q829m7me6rwpta7kvg8m82ez59nmefhqy0gh259wwrwjv76tw3wvum3mh0ck4vhmppq0yvltqs45tgj36x5mxlnca8vs5pn8ur')

// Output: 5 ADA
txBuilder.add_output(CardanoWasm.TransactionOutput.new(adaTargetAddressObject, CardanoWasm.Value.new(bn(5000000))))
console.log('Min. fee after output added:', txBuilder.min_fee().to_str())

const addInput = (txHash, index, value) => {
  const txHashObject = CardanoWasm.TransactionHash.from_bytes(Buffer.from(txHash, 'hex'))
  txBuilder.add_key_input(publicKeyHash, CardanoWasm.TransactionInput.new(txHashObject, index), CardanoWasm.Value.new(bn(value)))
}

// First input: 1 ADA
addInput('016da679e8757a0ba17e4de79fd3e7677fdfb38d9853d5a6fc6106498e3c8d6b', 0, 1000000)
console.log('Min. fee after 1st input added:', txBuilder.min_fee().to_str())
try {
  txBuilder.add_change_if_needed(address)
} catch (e) {
  if (e === 'Insufficient input in transaction') {
    console.log('Insufficient input as expected')
  } else {
    throw e
  }
}

// Second input: 2.5 ADA
addInput('731b9db933db3d2ca5473308873dd17dd325613d413322e6f3ac7f68ffa69659', 0, 2500000)
console.log('Min. fee after 2nd input added:', txBuilder.min_fee().to_str())
try {
  txBuilder.add_change_if_needed(address)
} catch (e) {
  if (e === 'Insufficient input in transaction') {
    console.log('Insufficient input as expected')
  } else {
    throw e
  }
}

// Third input: 11.111 ADA (yes I know this alone would suffice as sole input, but it should still work with the other inputs too, no?)
addInput('36440d14605cc9c718e842353dff013a8024c93f8801dd56694908086c5a8cdf', 0, 11111000)
console.log('Min. fee after 3rd input added:', txBuilder.min_fee().to_str())
txBuilder.add_change_if_needed(address)
console.log('Min. fee after change added:', txBuilder.min_fee().to_str())
console.log('Final fee:', txBuilder.get_fee_if_set().to_str())

// Building TX
const txBody = txBuilder.build()
const txHash = CardanoWasm.hash_transaction(txBody)
const witnesses = CardanoWasm.TransactionWitnessSet.new()
const vkeyWitnesses = CardanoWasm.Vkeywitnesses.new()
vkeyWitnesses.add(CardanoWasm.make_vkey_witness(txHash, privateKey))
witnesses.set_vkeys(vkeyWitnesses)

const transaction = CardanoWasm.Transaction.new(txBody, witnesses, undefined /* transaction metadata */)
const hex = Buffer.from(transaction.to_bytes()).toString('hex')

console.log('ADA transaction hex:', hex)

// This time the error is MissingVKeyWitnessesUTXOW because this example doesn't include the real private key.
// But the fee amounts reported are the exact same as with the real private key (with which I got FeeTooSmallUTxO).