From d4a4233e96aa76b25812c573140140b7b5fa3ffb Mon Sep 17 00:00:00 2001
From: Keagan McClelland <keagan.mcclelland@gmail.com>
Date: Mon, 11 Dec 2023 19:18:57 -0800
Subject: [PATCH] lnwallet+htlcswitch: define expanded NumPendingUpdates

This commit squashes the below operations for a net result where
we have an expanded capability of assessing pending updates. This
is made possible by packing the components into Duals in the prior
commits. We squash the operations to simplify review.

htlcswitch+lnwallet: rename PendingLocalUpdateCount

lnwallet: complete pending update queries API for LightningChannel

lnwallet+htlcswitch: consolidate NumPendingUpdates using ChannelParty

This commit makes the observation that we can cleanly define the
NumPendingUpdates function using a single expression by taking
advantage of the relevant fields being properly packed into Duals.
---
 htlcswitch/link.go  | 24 ++++++++++++++----------
 lnwallet/channel.go | 14 ++++++++------
 2 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/htlcswitch/link.go b/htlcswitch/link.go
index c459ef997..81c82cfa2 100644
--- a/htlcswitch/link.go
+++ b/htlcswitch/link.go
@@ -958,7 +958,7 @@ func (l *channelLink) resolveFwdPkgs() error {
 
 	// If any of our reprocessing steps require an update to the commitment
 	// txn, we initiate a state transition to capture all relevant changes.
-	if l.channel.PendingLocalUpdateCount() > 0 {
+	if l.channel.NumPendingUpdates(lntypes.Local, lntypes.Remote) > 0 {
 		return l.updateCommitTx()
 	}
 
@@ -1286,15 +1286,19 @@ func (l *channelLink) htlcManager() {
 		// the batch ticker so that it can be cleared. Otherwise pause
 		// the ticker to prevent waking up the htlcManager while the
 		// batch is empty.
-		if l.channel.PendingLocalUpdateCount() > 0 {
+		numUpdates := l.channel.NumPendingUpdates(
+			lntypes.Local, lntypes.Remote,
+		)
+		if numUpdates > 0 {
 			l.cfg.BatchTicker.Resume()
 			l.log.Tracef("BatchTicker resumed, "+
-				"PendingLocalUpdateCount=%d",
-				l.channel.PendingLocalUpdateCount())
+				"NumPendingUpdates(Local, Remote)=%d",
+				numUpdates,
+			)
 		} else {
 			l.cfg.BatchTicker.Pause()
 			l.log.Trace("BatchTicker paused due to zero " +
-				"PendingLocalUpdateCount")
+				"NumPendingUpdates(Local, Remote)")
 		}
 
 		select {
@@ -1652,7 +1656,7 @@ func (l *channelLink) handleDownstreamUpdateAdd(pkt *htlcPacket) error {
 	l.log.Tracef("received downstream htlc: payment_hash=%x, "+
 		"local_log_index=%v, pend_updates=%v",
 		htlc.PaymentHash[:], index,
-		l.channel.PendingLocalUpdateCount())
+		l.channel.NumPendingUpdates(lntypes.Local, lntypes.Remote))
 
 	pkt.outgoingChanID = l.ShortChanID()
 	pkt.outgoingHTLCID = index
@@ -1858,7 +1862,8 @@ func (l *channelLink) handleDownstreamPkt(pkt *htlcPacket) {
 // tryBatchUpdateCommitTx updates the commitment transaction if the batch is
 // full.
 func (l *channelLink) tryBatchUpdateCommitTx() {
-	if l.channel.PendingLocalUpdateCount() < uint64(l.cfg.BatchSize) {
+	pending := l.channel.NumPendingUpdates(lntypes.Local, lntypes.Remote)
+	if pending < uint64(l.cfg.BatchSize) {
 		return
 	}
 
@@ -1934,7 +1939,6 @@ func (l *channelLink) cleanupSpuriousResponse(pkt *htlcPacket) {
 // direct channel with, updating our respective commitment chains.
 func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 	switch msg := msg.(type) {
-
 	case *lnwire.UpdateAddHTLC:
 		if l.IsFlushing(Incoming) {
 			// This is forbidden by the protocol specification.
@@ -2592,9 +2596,9 @@ func (l *channelLink) updateCommitTx() error {
 		l.cfg.PendingCommitTicker.Resume()
 		l.log.Trace("PendingCommitTicker resumed")
 
+		n := l.channel.NumPendingUpdates(lntypes.Local, lntypes.Remote)
 		l.log.Tracef("revocation window exhausted, unable to send: "+
-			"%v, pend_updates=%v, dangling_closes%v",
-			l.channel.PendingLocalUpdateCount(),
+			"%v, pend_updates=%v, dangling_closes%v", n,
 			lnutils.SpewLogClosure(l.openedCircuits),
 			lnutils.SpewLogClosure(l.closedCircuits))
 
diff --git a/lnwallet/channel.go b/lnwallet/channel.go
index 9bd72e4de..8dba07973 100644
--- a/lnwallet/channel.go
+++ b/lnwallet/channel.go
@@ -5389,16 +5389,18 @@ func (lc *LightningChannel) oweCommitment(issuer lntypes.ChannelParty) bool {
 	return oweCommitment
 }
 
-// PendingLocalUpdateCount returns the number of local updates that still need
-// to be applied to the remote commitment tx.
-func (lc *LightningChannel) PendingLocalUpdateCount() uint64 {
+// NumPendingUpdates returns the number of updates originated by whoseUpdates
+// that have not been committed to the *tip* of whoseCommit's commitment chain.
+func (lc *LightningChannel) NumPendingUpdates(whoseUpdates lntypes.ChannelParty,
+	whoseCommit lntypes.ChannelParty) uint64 {
+
 	lc.RLock()
 	defer lc.RUnlock()
 
-	lastRemoteCommit := lc.commitChains.Remote.tip()
+	lastCommit := lc.commitChains.GetForParty(whoseCommit).tip()
+	updateIndex := lc.updateLogs.GetForParty(whoseUpdates).logIndex
 
-	return lc.updateLogs.Local.logIndex -
-		lastRemoteCommit.messageIndices.Local
+	return updateIndex - lastCommit.messageIndices.GetForParty(whoseUpdates)
 }
 
 // RevokeCurrentCommitment revokes the next lowest unrevoked commitment