public async Task <IBitcoinBasedTransaction> CreateSwapRefundTxAsync(
IBitcoinBasedTransaction paymentTx,
long amount,
string refundAddress,
byte[] redeemScript,
DateTimeOffset lockTime,
BitcoinBasedConfig currencyConfig)
{
var swapOutput = paymentTx.Outputs
.Cast <BitcoinBasedTxOutput>()
.FirstOrDefault(o => o.IsPayToScriptHash(redeemScript));
if (swapOutput == null)
{
throw new Exception("Can't find pay to script hash output");
}
var feeRate = await currencyConfig
.GetFeeRateAsync()
.ConfigureAwait(false);
var inputSize = new BitcoinInputToSign
{
Output = swapOutput,
Signer = new BitcoinRefundSigner()
}.SizeWithSignature();
var outputSize = new BitcoinDestination
{
AmountInSatoshi = amount,
Script = BitcoinAddress.Create(refundAddress, currencyConfig.Network).ScriptPubKey
}.Size();
var(txSize, _) = BitcoinTransactionParams.CalculateTxSize(
inputsCount: 1,
inputsSize: inputSize,
outputsCount: 1,
outputsSize: outputSize,
witnessCount: swapOutput.IsSegWit ? 1 : 0,
changeOutputSize: 0);
var feeInSatoshi = (long)(txSize * feeRate);
if (amount - feeInSatoshi < 0)
{
throw new Exception($"Insufficient funds for fee. Available {amount}, required {feeInSatoshi}");
}
return(currencyConfig.CreateP2PkhTx(
unspentOutputs: new ITxOutput[] { swapOutput },
destinationAddress: refundAddress,
changeAddress: refundAddress,
amount: amount - feeInSatoshi,
fee: feeInSatoshi,
lockTime: lockTime,
knownRedeems: new Script(redeemScript)));
}
public async Task <IBitcoinBasedTransaction> CreateSwapPaymentTxAsync(
IEnumerable <BitcoinBasedTxOutput> fromOutputs,
long amount,
string refundAddress,
string toAddress,
DateTimeOffset lockTime,
byte[] secretHash,
int secretSize,
BitcoinBasedConfig currencyConfig,
CancellationToken cancellationToken = default)
{
var availableAmountInSatoshi = fromOutputs.Sum(o => o.Value);
if (availableAmountInSatoshi <= amount)
{
throw new Exception($"Insufficient funds. Available {fromOutputs.Sum(o => o.Value)}, required: {amount}");
}
var feeRate = await currencyConfig
.GetFeeRateAsync()
.ConfigureAwait(false);
var lockScript = BitcoinBasedSwapTemplate.GenerateHtlcP2PkhSwapPayment(
aliceRefundAddress: refundAddress,
bobAddress: toAddress,
lockTimeStamp: lockTime.ToUnixTimeSeconds(),
secretHash: secretHash,
secretSize: secretSize,
expectedNetwork: currencyConfig.Network);
var feeInSatoshi = 0L;
var inputsToSign = fromOutputs
.Select(o => new BitcoinInputToSign {
Output = o
});
var destinations = new BitcoinDestination[]
{
new BitcoinDestination
{
Script = lockScript.PaymentScript,
AmountInSatoshi = amount
}
};
var txParams = await BitcoinTransactionParams.SelectTransactionParamsByFeeRateAsync(
availableInputs : inputsToSign,
destinations : destinations,
changeAddress : refundAddress,
feeRate : feeRate,
currencyConfig : currencyConfig,
cancellationToken : cancellationToken)
.ConfigureAwait(false);
if (txParams == null) // can't create tx with required feeRate => let's try to change feeRate and try again
{
var maxFeeInSatoshi = availableAmountInSatoshi - amount;
var(txSize, txSizeWithChange) = BitcoinTransactionParams.CalculateTxSize(
inputsCount: fromOutputs.Count(),
inputsSize: inputsToSign.Sum(i => i.SizeWithSignature()),
outputsCount: destinations.Length,
outputsSize: destinations.Sum(d => d.Size()),
witnessCount: fromOutputs.Sum(o => o.IsSegWit ? 1 : 0),
changeOutputSize: BitcoinTransactionParams.CalculateChangeOutputSize(
changeAddress: refundAddress,
network: currencyConfig.Network));
var estimatedFeeRate = maxFeeInSatoshi / txSizeWithChange;
if (Math.Abs(feeRate - estimatedFeeRate) / feeRate > MaxFeeRateChangePercent)
{
throw new Exception($"Insufficient funds. Available {fromOutputs.Sum(o => o.Value)}, required: {amount}. Probably feeRate has changed a lot.");
}
feeInSatoshi = maxFeeInSatoshi;
}
else
{
feeInSatoshi = (long)txParams.FeeInSatoshi;
}
var tx = currencyConfig
.CreateHtlcP2PkhScriptSwapPaymentTx(
unspentOutputs: txParams?.InputsToSign.Select(i => i.Output) ?? fromOutputs,
aliceRefundAddress: refundAddress,
bobAddress: toAddress,
lockTime: lockTime,
secretHash: secretHash,
secretSize: secretSize,
amount: amount,
fee: feeInSatoshi,
redeemScript: out _);
return(tx);
}