PSBT signing with BitcoinUTXOSpendingInfoSingle

docs/core/psbts.md

@@ -16,6 +16,7 @@ creation, updating, combining, signing, finalizing,
 and transaction extraction.
 
 An example on a typical PSBT workflow:
+
 ```scala mdoc:invisible
 import org.bitcoins.core.crypto.ECPrivateKey
 import org.bitcoins.core.protocol.script.ScriptPubKey
@@ -26,7 +27,7 @@ import scodec.bits._
 import scala.concurrent.{ExecutionContext, ExecutionContextExecutor}
 ```
 
-```scala mdoc:to-string
+```scala mdoc:compile-only
 implicit val ec: ExecutionContextExecutor = ExecutionContext.global
 
 // First you need an unsigned transaction,
@@ -105,6 +106,33 @@ val psbtFirstSigF =
       .sign(inputIndex = 0, signer = privKey0)
       .flatMap(_.sign(inputIndex = 0, signer = privKey1))
 
+// Alternatively, you can use produce a signature with a BitcoinUTXOSpendingInfoSingle
+// using the BitcoinSingleSigner will return a PartialSignature that can be added to a PSBT
+
+// First we need to declare out spendingInfoSingle
+val outPoint = unsignedTransaction.inputs.head.previousOutput
+val output = utxo0.outputs(outPoint.vout.toInt)
+
+val spendingInfoSingle = BitcoinUTXOSpendingInfoSingle(
+      outPoint = outPoint,
+      output = output,
+      signer = privKey0,
+      redeemScriptOpt = Some(redeemScript0),
+      scriptWitnessOpt = None,
+      hashType = HashType.sigHashAll,
+      conditionalPath = ConditionalPath.NoConditionsLeft
+    )
+
+// Then we can sign the transaction
+val signatureF = BitcoinSignerSingle.signSingle(spendingInfo = spendingInfoSingle,
+                                                               unsignedTx = unsignedTransaction,
+                                                               isDummySignature = false)
+
+// We can then add the signature to the PSBT
+// Note: this signature could be produced by us or another party
+signatureF.map(sig => psbtWithSigHashFlags.addSignature(sig, inputIndex = 0)
+
+// With our first input signed we can now move on to showing how another party could sign our second input
 psbtFirstSigF.map { psbtFirstSig =>
     // In this scenario, let's say that the second input does not belong to us and we need
     // another party to sign it. In this case we would need to send the PSBT to the other party.