cnct: add resolver report output type

This commit prepares for the commit sweep resolver to report on its
state.

contractcourt/channel_arbitrator.go

@@ -129,13 +129,27 @@ type ChannelArbitratorConfig struct {
 	ChainArbitratorConfig
 }
 
+// ReportOutputType describes the type of output that is being reported
+// on.
+type ReportOutputType uint8
+
+const (
+	// ReportOutputIncomingHtlc is an incoming hash time locked contract on
+	// the commitment tx.
+	ReportOutputIncomingHtlc ReportOutputType = iota
+
+	// ReportOutputOutgoingHtlc is an outgoing hash time locked contract on
+	// the commitment tx.
+	ReportOutputOutgoingHtlc
+)
+
 // ContractReport provides a summary of a commitment tx output.
 type ContractReport struct {
 	// Outpoint is the final output that will be swept back to the wallet.
 	Outpoint wire.OutPoint
 
-	// Incoming indicates whether the htlc was incoming to this channel.
-	Incoming bool
+	// Type indicates the type of the reported output.
+	Type ReportOutputType
 
 	// Amount is the final value that will be swept in back to the wallet.
 	Amount btcutil.Amount

contractcourt/htlc_incoming_contest_resolver.go

@@ -293,7 +293,7 @@ func (h *htlcIncomingContestResolver) report() *ContractReport {
 
 	return &ContractReport{
 		Outpoint:       h.htlcResolution.ClaimOutpoint,
-		Incoming:       true,
+		Type:           ReportOutputIncomingHtlc,
 		Amount:         finalAmt,
 		MaturityHeight: h.htlcExpiry,
 		LimboBalance:   finalAmt,

contractcourt/htlc_outgoing_contest_resolver.go

@@ -166,7 +166,7 @@ func (h *htlcOutgoingContestResolver) report() *ContractReport {
 
 	return &ContractReport{
 		Outpoint:       h.htlcResolution.ClaimOutpoint,
-		Incoming:       false,
+		Type:           ReportOutputOutgoingHtlc,
 		Amount:         finalAmt,
 		MaturityHeight: h.htlcResolution.Expiry,
 		LimboBalance:   finalAmt,

rpcserver.go

@@ -34,6 +34,7 @@ import (
 	"github.com/lightningnetwork/lnd/chanbackup"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channelnotifier"
+	"github.com/lightningnetwork/lnd/contractcourt"
 	"github.com/lightningnetwork/lnd/discovery"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/input"
@@ -2451,8 +2452,10 @@ func (r *rpcServer) arbitratorPopulateForceCloseResp(chanPoint *wire.OutPoint,
 	reports := arbitrator.Report()
 
 	for _, report := range reports {
+		incoming := report.Type == contractcourt.ReportOutputIncomingHtlc
+
 		htlc := &lnrpc.PendingHTLC{
-			Incoming:       report.Incoming,
+			Incoming:       incoming,
 			Amount:         int64(report.Amount),
 			Outpoint:       report.Outpoint.String(),
 			MaturityHeight: report.MaturityHeight,