tapfreighter: add SendStateBroadcastComplete state

Introduce a new send state to act as a threshold for transfer
cancellation handling. After this state, the anchor transaction may
already be in the mempool or confirmed on-chain. Before reaching this
point, however, the broadcast may have failed, requiring different
handling.

Author: ffranr

itest/assertions.go

@@ -963,7 +963,7 @@ func AssertSendEventsComplete(t *testing.T, scriptKey []byte,
 	stream *EventSubscription[*taprpc.SendEvent]) {
 
 	AssertSendEvents(
-		t, scriptKey, stream, tapfreighter.SendStateWaitTxConf,
+		t, scriptKey, stream, tapfreighter.SendStateBroadcastComplete,
 		tapfreighter.SendStateComplete,
 	)
 }

itest/psbt_test.go

@@ -1388,7 +1388,7 @@ func testPsbtMultiSend(t *harnessTest) {
 
 	AssertSendEvents(
 		t.t, scriptKey1Bytes, sendEvents,
-		tapfreighter.SendStateWaitTxConf,
+		tapfreighter.SendStateBroadcastComplete,
 		tapfreighter.SendStateComplete,
 	)
 

tapfreighter/chain_porter.go

@@ -1395,6 +1395,16 @@ func (p *ChainPorter) stateStep(currentPkg sendPackage) (*sendPackage, error) {
 				"transaction %v: %w", txHash, err)
 		}
 
+		// Set send state to the next state to evaluate.
+		currentPkg.SendState = SendStateBroadcastComplete
+		return &currentPkg, nil
+
+	// At this stage, the transaction has been broadcast to the network.
+	// From this point forward, the transfer cancellation methodology
+	// changes.
+	case SendStateBroadcastComplete:
+		log.Infof("Transfer tx broadcast complete")
+
 		// With the transaction broadcast, we'll deliver a
 		// notification via the transaction broadcast response channel.
 		currentPkg.deliverTxBroadcastResp()

tapfreighter/parcel.go

@@ -47,6 +47,12 @@ const (
 	// ensure it properly tracks the coins allocated to the anchor output.
 	SendStateBroadcast
 
+	// SendStateBroadcastComplete represents the state where the transfer
+	// transaction has been broadcast and is either in the mempool or
+	// confirmed on-chain. At this stage, cancellation cannot rely solely
+	// on naive coin unlocking.
+	SendStateBroadcastComplete
+
 	// SendStateWaitTxConf is a state in which we will wait for the transfer
 	// transaction to confirm on-chain.
 	SendStateWaitTxConf
@@ -85,6 +91,9 @@ func (s SendState) String() string {
 	case SendStateBroadcast:
 		return "SendStateBroadcast"
 
+	case SendStateBroadcastComplete:
+		return "SendStateBroadcastComplete"
+
 	case SendStateWaitTxConf:
 		return "SendStateWaitTxConf"