/// <summary>
/// Constructs an unsigned transaction by referencing previous unspent outputs.
/// A change output is added when necessary to return extra value back to the wallet.
/// </summary>
/// <param name="outputs">Transaction output array without change.</param>
/// <param name="changeScript">Output script to pay change to.</param>
/// <param name="fetchInputsAsync">Input selection source.</param>
/// <returns>Unsigned transaction and total input amount.</returns>
/// <exception cref="InsufficientFundsException">Input source was unable to provide enough input value.</exception>
public static async Task <Tuple <Transaction, Amount> > BuildUnsignedTransaction(Transaction.Output[] outputs,
OutputScript changeScript,
Amount feePerKb,
InputSource fetchInputsAsync)
{
if (outputs == null)
{
throw new ArgumentNullException(nameof(outputs));
}
if (changeScript == null)
{
throw new ArgumentNullException(nameof(changeScript));
}
if (fetchInputsAsync == null)
{
throw new ArgumentNullException(nameof(fetchInputsAsync));
}
var targetAmount = outputs.Sum(o => o.Amount);
var estimatedSize = Transaction.EstimateSerializeSize(1, outputs, true);
var targetFee = TransactionFees.FeeForSerializeSize(feePerKb, estimatedSize);
while (true)
{
var funding = await fetchInputsAsync(targetAmount + targetFee);
var inputAmount = funding.Item1;
var inputs = funding.Item2;
if (inputAmount < targetAmount + targetFee)
{
throw new InsufficientFundsException();
}
var unsignedTransaction = new Transaction(Transaction.SupportedVersion, inputs, outputs, 0, 0);
if (inputAmount > targetAmount + targetFee)
{
unsignedTransaction = TransactionFees.AddChange(unsignedTransaction, inputAmount,
changeScript, feePerKb);
}
if (TransactionFees.EstimatedFeePerKb(unsignedTransaction, inputAmount) < feePerKb)
{
estimatedSize = Transaction.EstimateSerializeSize(inputs.Length, outputs, true);
targetFee = TransactionFees.FeeForSerializeSize(feePerKb, estimatedSize);
}
else
{
return(Tuple.Create(unsignedTransaction, inputAmount));
}
}
}
/// <summary>
/// Constructs an unsigned transaction by referencing previous unspent outputs.
/// A change output is added when necessary to return extra value back to the wallet.
/// </summary>
/// <param name="outputs">Transaction output array without change.</param>
/// <param name="changeScript">Output script to pay change to.</param>
/// <param name="fetchInputsAsync">Input selection source.</param>
/// <returns>Unsigned transaction and total input amount.</returns>
/// <exception cref="InsufficientFundsException">Input source was unable to provide enough input value.</exception>
public static async Task <Tuple <Transaction, Amount> > BuildUnsignedTransaction(Transaction.Output[] outputs,
Amount feePerKb,
InputSource fetchInputsAsync,
ChangeSource fetchChangeAsync)
{
if (outputs == null)
{
throw new ArgumentNullException(nameof(outputs));
}
if (fetchInputsAsync == null)
{
throw new ArgumentNullException(nameof(fetchInputsAsync));
}
if (fetchChangeAsync == null)
{
throw new ArgumentNullException(nameof(fetchChangeAsync));
}
var targetAmount = outputs.Sum(o => o.Amount);
var estimatedSize = Transaction.EstimateSerializeSize(1, outputs, true);
var targetFee = TransactionFees.FeeForSerializeSize(feePerKb, estimatedSize);
while (true)
{
var funding = await fetchInputsAsync(targetAmount + targetFee);
var inputAmount = funding.Item1;
var inputs = funding.Item2;
if (inputAmount < targetAmount + targetFee)
{
throw new InsufficientFundsException();
}
var maxSignedSize = Transaction.EstimateSerializeSize(inputs.Length, outputs, true);
var maxRequiredFee = TransactionFees.FeeForSerializeSize(feePerKb, maxSignedSize);
var remainingAmount = inputAmount - targetAmount;
if (remainingAmount < maxRequiredFee)
{
targetFee = maxRequiredFee;
continue;
}
var unsignedTransaction = new Transaction(Transaction.SupportedVersion, inputs, outputs, 0, 0);
var changeAmount = inputAmount - targetAmount - maxRequiredFee;
if (changeAmount != 0 && !TransactionRules.IsDustAmount(changeAmount, Transaction.PayToPubKeyHashPkScriptSize, feePerKb))
{
var changeScript = await fetchChangeAsync();
if (changeScript.Script.Length > Transaction.PayToPubKeyHashPkScriptSize)
{
throw new Exception("Fee estimation requires change scripts no larger than P2PKH output scripts");
}
var changeOutput = new Transaction.Output(changeAmount, Transaction.Output.LatestPkScriptVersion, changeScript.Script);
var outputList = unsignedTransaction.Outputs.ToList();
outputList.Add(changeOutput);
var outputsWithChange = outputList.ToArray();
unsignedTransaction = new Transaction(unsignedTransaction.Version, unsignedTransaction.Inputs, outputsWithChange,
unsignedTransaction.LockTime, unsignedTransaction.Expiry);
}
return(Tuple.Create(unsignedTransaction, inputAmount));
}
}