itest: add new testCustomChannelsHtlcForceClose itest

In this commit, we add a new itest that tests the 4 sweeping cases for
HTLCs:
  * local success
  * remote success
  * local timeout
  * remote timeout

To test this, we have Alice load up her commitment transaction with 4
HTLCs (2 incoming, 2 outgoing) using hodl invoices. Then we force close
her commitment transaction. In this scenario, she needs to broadcast a
second level transaction to ultimately timeout, while Bob can sweep
directly from the commitment transaction.

go.mod

@@ -36,6 +36,7 @@ require (
 	github.com/urfave/cli v1.22.9
 	go.etcd.io/bbolt v1.3.11
 	golang.org/x/crypto v0.25.0
+	golang.org/x/exp v0.0.0-20240325151524-a685a6edb6d8
 	golang.org/x/net v0.27.0
 	golang.org/x/sync v0.8.0
 	google.golang.org/grpc v1.65.0
@@ -201,7 +202,6 @@ require (
 	go.uber.org/mock v0.4.0 // indirect
 	go.uber.org/multierr v1.6.0 // indirect
 	go.uber.org/zap v1.23.0 // indirect
-	golang.org/x/exp v0.0.0-20240325151524-a685a6edb6d8 // indirect
 	golang.org/x/mod v0.17.0 // indirect
 	golang.org/x/sys v0.22.0 // indirect
 	golang.org/x/term v0.22.0 // indirect

itest/assertions.go

@@ -3,11 +3,13 @@ package itest
 import (
 	"context"
 	"fmt"
+	"testing"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
 	"github.com/lightningnetwork/lnd/lntest"
 	"github.com/lightningnetwork/lnd/lntest/wait"
 	"github.com/stretchr/testify/require"
@@ -205,3 +207,27 @@ func assertChannelClosed(ctx context.Context, t *harnessTest,
 
 	return closingTxid
 }
+
+func assertSweepExists(t *testing.T, node *HarnessNode,
+	witnessType walletrpc.WitnessType) {
+
+	ctxb := context.Background()
+	err := wait.NoError(func() error {
+		pendingSweeps, err := node.WalletKitClient.PendingSweeps(
+			ctxb, &walletrpc.PendingSweepsRequest{},
+		)
+		if err != nil {
+			return err
+		}
+
+		for _, sweep := range pendingSweeps.PendingSweeps {
+			if sweep.WitnessType == witnessType {
+				return nil
+			}
+		}
+
+		return fmt.Errorf("failed to find second level sweep: %v",
+			toProtoJSON(t, pendingSweeps))
+	}, defaultTimeout)
+	require.NoError(t, err)
+}

itest/assets_test.go

@@ -1868,3 +1868,91 @@ func toProtoJSON(t *testing.T, resp proto.Message) string {
 
 	return string(jsonBytes)
 }
+
+func assertNumHtlcs(t *testing.T, node *HarnessNode, expected int) {
+	t.Helper()
+
+	ctxb := context.Background()
+
+	err := wait.NoError(func() error {
+		listChansRequest := &lnrpc.ListChannelsRequest{}
+		listChansResp, err := node.ListChannels(ctxb, listChansRequest)
+		if err != nil {
+			return err
+		}
+
+		var numHtlcs int
+		for _, channel := range listChansResp.Channels {
+			numHtlcs += len(channel.PendingHtlcs)
+		}
+
+		if numHtlcs != expected {
+			return fmt.Errorf("expected %v HTLCs, got %v, %v", expected, numHtlcs, spew.Sdump(toProtoJSON(t, listChansResp)))
+		}
+
+		return nil
+	}, defaultTimeout)
+	require.NoError(t, err)
+}
+
+type forceCloseExpiryInfo struct {
+	currentHeight uint32
+	csvDelay      uint32
+
+	cltvDelays map[lntypes.Hash]uint32
+
+	localAssetBalance  uint64
+	remoteAssetBalance uint64
+
+	t *testing.T
+
+	node *HarnessNode
+}
+
+func (f *forceCloseExpiryInfo) blockTillExpiry(hash lntypes.Hash) uint32 {
+	ctxb := context.Background()
+	nodeInfo, err := f.node.GetInfo(ctxb, &lnrpc.GetInfoRequest{})
+	require.NoError(f.t, err)
+
+	cltv, ok := f.cltvDelays[hash]
+	require.True(f.t, ok)
+
+	f.t.Logf("current_height=%v, expiry=%v, mining %v blocks",
+		nodeInfo.BlockHeight, cltv, cltv-nodeInfo.BlockHeight)
+
+	return cltv - nodeInfo.BlockHeight
+}
+
+func newCloseExpiryInfo(t *testing.T, node *HarnessNode) forceCloseExpiryInfo {
+	ctxb := context.Background()
+
+	listChansRequest := &lnrpc.ListChannelsRequest{}
+	listChansResp, err := node.ListChannels(ctxb, listChansRequest)
+	require.NoError(t, err)
+
+	mainChan := listChansResp.Channels[0]
+
+	nodeInfo, err := node.GetInfo(ctxb, &lnrpc.GetInfoRequest{})
+	require.NoError(t, err)
+
+	cltvs := make(map[lntypes.Hash]uint32)
+	for _, htlc := range mainChan.PendingHtlcs {
+		var payHash lntypes.Hash
+		copy(payHash[:], htlc.HashLock)
+		cltvs[payHash] = htlc.ExpirationHeight
+	}
+
+	var assetData rfqmsg.JsonAssetChannel
+	err = json.Unmarshal(mainChan.CustomChannelData, &assetData)
+	require.NoError(t, err)
+
+	return forceCloseExpiryInfo{
+		csvDelay:           mainChan.CsvDelay,
+		currentHeight:      nodeInfo.BlockHeight,
+		cltvDelays:         cltvs,
+		localAssetBalance:  assetData.Assets[0].LocalBalance,
+		remoteAssetBalance: assetData.Assets[0].RemoteBalance,
+		t:                  t,
+		node:               node,
+	}
+}