tapchannel: PaymentBandwidth uses AuxHtlcView

We now make use of the AuxHtlcView to calculate a more precise value of
our local balance. This is using the ComputeView helper in order to
manually process HTLC adds from our side, providing us with the correct
value of local balance. We also add the DecodedView as a return value of
the helper function, but this will only be used in the next commit for
verbose logging.

Author: GeorgeTsagk

tapchannel/aux_traffic_shaper.go

@@ -14,6 +14,7 @@ import (
 	"github.com/lightninglabs/taproot-assets/rfqmsg"
 	cmsg "github.com/lightninglabs/taproot-assets/tapchannelmsg"
 	lfn "github.com/lightningnetwork/lnd/fn/v2"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/tlv"
@@ -111,7 +112,7 @@ func (s *AuxTrafficShaper) ShouldHandleTraffic(_ lnwire.ShortChannelID,
 func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 	commitmentBlob lfn.Option[tlv.Blob], linkBandwidth,
 	htlcAmt lnwire.MilliSatoshi,
-	_ lnwallet.AuxHtlcView) (lnwire.MilliSatoshi, error) {
+	htlcView lnwallet.AuxHtlcView) (lnwire.MilliSatoshi, error) {
 
 	// If the commitment or HTLC blob is not set, we don't have any
 	// information about the channel and cannot determine the available
@@ -179,7 +180,10 @@ func (s *AuxTrafficShaper) PaymentBandwidth(htlcBlob,
 	// never be settled. Other HTLCs that may also call into this method are
 	// not yet registered to the commitment, so we need to account for them
 	// manually.
-	computedLocal := ComputeLocalBalance(*commitment)
+	computedLocal, _, err := ComputeLocalBalance(*commitment, htlcView)
+	if err != nil {
+		return 0, err
+	}
 
 	// If the HTLC carries asset units (keysend, forwarding), then there's
 	// no need to do any RFQ related math. We can directly compare the asset
@@ -305,12 +309,34 @@ func (s *AuxTrafficShaper) paymentBandwidth(htlc *rfqmsg.Htlc,
 
 // ComputeLocalBalance combines the given commitment state with the HtlcView to
 // produce the available local balance with accuracy.
-func ComputeLocalBalance(commitment cmsg.Commitment) uint64 {
-	// Let's get the current local asset balance of the channel as reported
-	// by the latest commitment.
+func ComputeLocalBalance(commitment cmsg.Commitment,
+	htlcView lnwallet.AuxHtlcView) (uint64, *DecodedView, error) {
+
+	// Set the htlcView next height to 0. This is needed because the
+	// following helper `ComputeLocalBalance` will use that height to add or
+	// remove HTLCs that have a matching addHeight. The HTLCs that are not
+	// yet part of the commitment have an addHeight of 0, so that's the
+	// height we want to filter by here.
+	htlcView.NextHeight = 0
+
+	// Let's get the current local and remote asset balances of the channel
+	// as reported by the latest commitment.
 	localBalance := cmsg.OutputSum(commitment.LocalOutputs())
+	remoteBalance := cmsg.OutputSum(commitment.RemoteOutputs())
+
+	// With the help of the latest HtlcView, let's calculate a more precise
+	// local balance. This is useful in order to not forward HTLCs that may
+	// never be settled. Other HTLCs that may also call into this method are
+	// not yet registered to the commitment, so we need to account for them
+	// manually.
+	computedLocal, _, decodedView, _, err := ComputeView(
+		localBalance, remoteBalance, lntypes.Local, htlcView,
+	)
+	if err != nil {
+		return 0, nil, err
+	}
 
-	return localBalance
+	return computedLocal, decodedView, nil
 }
 
 // ProduceHtlcExtraData is a function that, based on the previous custom record