lnwallet: pack commit chains into Dual

This commit packs the LightningChannel's localCommitmentChain and
remoteCommitmentChain into a Dual structure for better symmetric
access. This will be leveraged by an upcoming commit where we want
to more concisely express how we compute the number of pending
updates.

lnwallet/channel_test.go

@@ -1435,12 +1435,12 @@ func TestHTLCDustLimit(t *testing.T) {
 	// while Bob's should not, because the value falls beneath his dust
 	// limit. The amount of the HTLC should be applied to fees in Bob's
 	// commitment transaction.
-	aliceCommitment := aliceChannel.localCommitChain.tip()
+	aliceCommitment := aliceChannel.commitChains.Local.tip()
 	if len(aliceCommitment.txn.TxOut) != 3 {
 		t.Fatalf("incorrect # of outputs: expected %v, got %v",
 			3, len(aliceCommitment.txn.TxOut))
 	}
-	bobCommitment := bobChannel.localCommitChain.tip()
+	bobCommitment := bobChannel.commitChains.Local.tip()
 	if len(bobCommitment.txn.TxOut) != 2 {
 		t.Fatalf("incorrect # of outputs: expected %v, got %v",
 			2, len(bobCommitment.txn.TxOut))
@@ -1465,7 +1465,7 @@ func TestHTLCDustLimit(t *testing.T) {
 
 	// At this point, for Alice's commitment chains, the value of the HTLC
 	// should have been added to Alice's balance and TotalSatoshisSent.
-	commitment := aliceChannel.localCommitChain.tip()
+	commitment := aliceChannel.commitChains.Local.tip()
 	if len(commitment.txn.TxOut) != 2 {
 		t.Fatalf("incorrect # of outputs: expected %v, got %v",
 			2, len(commitment.txn.TxOut))
@@ -1698,7 +1698,7 @@ func TestChannelBalanceDustLimit(t *testing.T) {
 	// output for Alice's balance should have been removed as dust, leaving
 	// only a single output that will send the remaining funds in the
 	// channel to Bob.
-	commitment := bobChannel.localCommitChain.tip()
+	commitment := bobChannel.commitChains.Local.tip()
 	if len(commitment.txn.TxOut) != 1 {
 		t.Fatalf("incorrect # of outputs: expected %v, got %v",
 			1, len(commitment.txn.TxOut))
@@ -1816,25 +1816,25 @@ func TestStateUpdatePersistence(t *testing.T) {
 
 	// After the state transition the fee update is fully locked in, and
 	// should've been removed from both channels' update logs.
-	if aliceChannel.localCommitChain.tail().feePerKw != fee {
+	if aliceChannel.commitChains.Local.tail().feePerKw != fee {
 		t.Fatalf("fee not locked in")
 	}
-	if bobChannel.localCommitChain.tail().feePerKw != fee {
+	if bobChannel.commitChains.Local.tail().feePerKw != fee {
 		t.Fatalf("fee not locked in")
 	}
 	assertNumLogUpdates(3, 1)
 
 	// The latest commitment from both sides should have all the HTLCs.
-	numAliceOutgoing := aliceChannel.localCommitChain.tail().outgoingHTLCs
-	numAliceIncoming := aliceChannel.localCommitChain.tail().incomingHTLCs
+	numAliceOutgoing := aliceChannel.commitChains.Local.tail().outgoingHTLCs
+	numAliceIncoming := aliceChannel.commitChains.Local.tail().incomingHTLCs
 	if len(numAliceOutgoing) != 3 {
 		t.Fatalf("expected %v htlcs, instead got %v", 3, numAliceOutgoing)
 	}
 	if len(numAliceIncoming) != 1 {
 		t.Fatalf("expected %v htlcs, instead got %v", 1, numAliceIncoming)
 	}
-	numBobOutgoing := bobChannel.localCommitChain.tail().outgoingHTLCs
-	numBobIncoming := bobChannel.localCommitChain.tail().incomingHTLCs
+	numBobOutgoing := bobChannel.commitChains.Local.tail().outgoingHTLCs
+	numBobIncoming := bobChannel.commitChains.Local.tail().incomingHTLCs
 	if len(numBobOutgoing) != 1 {
 		t.Fatalf("expected %v htlcs, instead got %v", 1, numBobOutgoing)
 	}
@@ -2090,20 +2090,24 @@ func TestCancelHTLC(t *testing.T) {
 
 	// Now HTLCs should be present on the commitment transaction for either
 	// side.
-	if len(aliceChannel.localCommitChain.tip().outgoingHTLCs) != 0 ||
-		len(aliceChannel.remoteCommitChain.tip().outgoingHTLCs) != 0 {
+	if len(aliceChannel.commitChains.Local.tip().outgoingHTLCs) != 0 ||
+		len(aliceChannel.commitChains.Remote.tip().outgoingHTLCs) != 0 {
+
 		t.Fatalf("htlc's still active from alice's POV")
 	}
-	if len(aliceChannel.localCommitChain.tip().incomingHTLCs) != 0 ||
-		len(aliceChannel.remoteCommitChain.tip().incomingHTLCs) != 0 {
+	if len(aliceChannel.commitChains.Local.tip().incomingHTLCs) != 0 ||
+		len(aliceChannel.commitChains.Remote.tip().incomingHTLCs) != 0 {
+
 		t.Fatalf("htlc's still active from alice's POV")
 	}
-	if len(bobChannel.localCommitChain.tip().outgoingHTLCs) != 0 ||
-		len(bobChannel.remoteCommitChain.tip().outgoingHTLCs) != 0 {
+	if len(bobChannel.commitChains.Local.tip().outgoingHTLCs) != 0 ||
+		len(bobChannel.commitChains.Remote.tip().outgoingHTLCs) != 0 {
+
 		t.Fatalf("htlc's still active from bob's POV")
 	}
-	if len(bobChannel.localCommitChain.tip().incomingHTLCs) != 0 ||
-		len(bobChannel.remoteCommitChain.tip().incomingHTLCs) != 0 {
+	if len(bobChannel.commitChains.Local.tip().incomingHTLCs) != 0 ||
+		len(bobChannel.commitChains.Remote.tip().incomingHTLCs) != 0 {
+
 		t.Fatalf("htlc's still active from bob's POV")
 	}
 
@@ -5207,7 +5211,9 @@ func TestChanCommitWeightDustHtlcs(t *testing.T) {
 	// When sending htlcs we enforce the feebuffer on the commitment
 	// transaction.
 	remoteCommitWeight := func(lc *LightningChannel) lntypes.WeightUnit {
-		remoteACKedIndex := lc.localCommitChain.tip().theirMessageIndex
+		remoteACKedIndex :=
+			lc.commitChains.Local.tip().theirMessageIndex
+
 		htlcView := lc.fetchHTLCView(remoteACKedIndex,
 			lc.localUpdateLog.logIndex)
 
@@ -5830,7 +5836,7 @@ func TestChannelUnilateralClosePendingCommit(t *testing.T) {
 	// At this point, Alice's commitment chain should have a new pending
 	// commit for Bob. We'll extract it so we can simulate Bob broadcasting
 	// the commitment due to an issue.
-	bobCommit := aliceChannel.remoteCommitChain.tip().txn
+	bobCommit := aliceChannel.commitChains.Remote.tip().txn
 	bobTxHash := bobCommit.TxHash()
 	spendDetail := &chainntnfs.SpendDetail{
 		SpenderTxHash: &bobTxHash,
@@ -7523,7 +7529,7 @@ func TestForceCloseBorkedState(t *testing.T) {
 
 	// We manually advance the commitment tail here since the above
 	// ReceiveRevocation call will fail before it's actually advanced.
-	aliceChannel.remoteCommitChain.advanceTail()
+	aliceChannel.commitChains.Remote.advanceTail()
 	_, err = aliceChannel.SignNextCommitment()
 	if err != channeldb.ErrChanBorked {
 		t.Fatalf("sign commitment should have failed: %v", err)
@@ -7739,7 +7745,7 @@ func TestIdealCommitFeeRate(t *testing.T) {
 		maxFeeAlloc float64) chainfee.SatPerKWeight {
 
 		balance, weight := c.availableBalance(AdditionalHtlc)
-		feeRate := c.localCommitChain.tip().feePerKw
+		feeRate := c.commitChains.Local.tip().feePerKw
 		currentFee := feeRate.FeeForWeight(weight)
 
 		maxBalance := balance.ToSatoshis() + currentFee
@@ -7756,7 +7762,7 @@ func TestIdealCommitFeeRate(t *testing.T) {
 	// currentFeeRate calculates the current fee rate of the channel. The
 	// ideal fee rate is floored at the current fee rate of the channel.
 	currentFeeRate := func(c *LightningChannel) chainfee.SatPerKWeight {
-		return c.localCommitChain.tip().feePerKw
+		return c.commitChains.Local.tip().feePerKw
 	}
 
 	// testCase definies the test cases when calculating the ideal fee rate
@@ -11099,7 +11105,7 @@ func TestBlindingPointPersistence(t *testing.T) {
 	require.NoError(t, err, "unable to restart alice")
 
 	// Assert that the blinding point is restored from disk.
-	remoteCommit := aliceChannel.remoteCommitChain.tip()
+	remoteCommit := aliceChannel.commitChains.Remote.tip()
 	require.Len(t, remoteCommit.outgoingHTLCs, 1)
 	require.Equal(t, blinding,
 		remoteCommit.outgoingHTLCs[0].BlindingPoint.UnwrapOrFailV(t))
@@ -11116,7 +11122,7 @@ func TestBlindingPointPersistence(t *testing.T) {
 	require.NoError(t, err, "unable to restart bob's channel")
 
 	// Assert that Bob is able to recover the blinding point from disk.
-	bobCommit := bobChannel.localCommitChain.tip()
+	bobCommit := bobChannel.commitChains.Local.tip()
 	require.Len(t, bobCommit.incomingHTLCs, 1)
 	require.Equal(t, blinding,
 		bobCommit.incomingHTLCs[0].BlindingPoint.UnwrapOrFailV(t))