graph/db: version highest chan id

diff --git a/discovery/chan_series.go b/discovery/chan_series.go
index 9ba9607..ed64453 100644
--- a/discovery/chan_series.go
+++ b/discovery/chan_series.go
@@ -73,12 +73,12 @@ type ChannelGraphTimeSeries interface {
 // in-protocol channel range queries to quickly and efficiently synchronize our
 // channel state with all peers.
 type ChanSeries struct {
-	graph *graphdb.ChannelGraph
+	graph *graphdb.VersionedGraph
 }
 
 // NewChanSeries constructs a new ChanSeries backed by a channeldb.ChannelGraph.
 // The returned ChanSeries implements the ChannelGraphTimeSeries interface.
-func NewChanSeries(graph *graphdb.ChannelGraph) *ChanSeries {
+func NewChanSeries(graph *graphdb.VersionedGraph) *ChanSeries {
 	return &ChanSeries{
 		graph: graph,
 	}
diff --git a/graph/db/graph.go b/graph/db/graph.go
index 4579f16..f963286 100644
--- a/graph/db/graph.go
+++ b/graph/db/graph.go
@@ -688,8 +688,10 @@ func (c *ChannelGraph) AddEdgeProof(chanID lnwire.ShortChannelID,
 }
 
 // HighestChanID returns the "highest" known channel ID in the channel graph.
-func (c *ChannelGraph) HighestChanID(ctx context.Context) (uint64, error) {
-	return c.db.HighestChanID(ctx)
+func (c *ChannelGraph) HighestChanID(ctx context.Context,
+	v lnwire.GossipVersion) (uint64, error) {
+
+	return c.db.HighestChanID(ctx, v)
 }
 
 // ChanUpdatesInHorizon returns all known channel edges with updates in the
@@ -950,6 +952,11 @@ func (c *VersionedGraph) DisabledChannelIDs() ([]uint64, error) {
 	return c.db.DisabledChannelIDs(c.v)
 }
 
+// HighestChanID returns the "highest" known channel ID in the channel graph.
+func (c *VersionedGraph) HighestChanID(ctx context.Context) (uint64, error) {
+	return c.db.HighestChanID(ctx, c.v)
+}
+
 // ChannelID attempts to lookup the 8-byte compact channel ID.
 func (c *VersionedGraph) ChannelID(chanPoint *wire.OutPoint) (uint64, error) {
 	return c.db.ChannelID(c.v, chanPoint)
diff --git a/graph/db/graph_test.go b/graph/db/graph_test.go
index d56c42d..6516489 100644
--- a/graph/db/graph_test.go
+++ b/graph/db/graph_test.go
@@ -198,6 +198,10 @@ var versionedTests = []versionedTest{
 		name: "graph cache for each node channel",
 		test: testGraphCacheForEachNodeChannel,
 	},
+	{
+		name: "highest chan id",
+		test: testHighestChanID,
+	},
 }
 
 // TestVersionedDBs runs various tests against both v1 and v2 versioned
@@ -2484,41 +2488,32 @@ func TestGraphPruning(t *testing.T) {
 
 // TestHighestChanID tests that we're able to properly retrieve the highest
 // known channel ID in the database.
-func TestHighestChanID(t *testing.T) {
+func testHighestChanID(t *testing.T, v lnwire.GossipVersion) {
 	t.Parallel()
 	ctx := t.Context()
 
-	graph := MakeTestGraph(t)
+	graph := NewVersionedGraph(MakeTestGraph(t), v)
 
 	// If we don't yet have any channels in the database, then we should
 	// get a channel ID of zero if we ask for the highest channel ID.
 	bestID, err := graph.HighestChanID(ctx)
 	require.NoError(t, err, "unable to get highest ID")
 	if bestID != 0 {
-		t.Fatalf("best ID w/ no chan should be zero, is instead: %v",
-			bestID)
+		require.Equal(t, uint64(0), bestID)
 	}
 
 	// Next, we'll insert two channels into the database, with each channel
 	// connecting the same two nodes.
-	node1 := createTestVertex(t, lnwire.GossipVersion1)
-	node2 := createTestVertex(t, lnwire.GossipVersion1)
+	node1 := createTestVertex(t, v)
+	node2 := createTestVertex(t, v)
 
 	// The first channel with be at height 10, while the other will be at
 	// height 100.
-	edge1, _ := createEdge(
-		lnwire.GossipVersion1, 10, 0, 0, 0, node1, node2,
-	)
-	edge2, chanID2 := createEdge(
-		lnwire.GossipVersion1, 100, 0, 0, 0, node1, node2,
-	)
+	edge1, _ := createEdge(v, 10, 0, 0, 0, node1, node2)
+	edge2, chanID2 := createEdge(v, 100, 0, 0, 0, node1, node2)
 
-	if err := graph.AddChannelEdge(ctx, edge1); err != nil {
-		t.Fatalf("unable to create channel edge: %v", err)
-	}
-	if err := graph.AddChannelEdge(ctx, edge2); err != nil {
-		t.Fatalf("unable to create channel edge: %v", err)
-	}
+	require.NoError(t, graph.AddChannelEdge(ctx, edge1))
+	require.NoError(t, graph.AddChannelEdge(ctx, edge2))
 
 	// Now that the edges has been inserted, we'll query for the highest
 	// known channel ID in the database.
@@ -2526,25 +2521,17 @@ func TestHighestChanID(t *testing.T) {
 	require.NoError(t, err, "unable to get highest ID")
 
 	if bestID != chanID2.ToUint64() {
-		t.Fatalf("expected %v got %v for best chan ID: ",
-			chanID2.ToUint64(), bestID)
+		require.Equal(t, chanID2.ToUint64(), bestID)
 	}
 
 	// If we add another edge, then the current best chan ID should be
 	// updated as well.
-	edge3, chanID3 := createEdge(
-		lnwire.GossipVersion1, 1000, 0, 0, 0, node1, node2,
-	)
-	if err := graph.AddChannelEdge(ctx, edge3); err != nil {
-		t.Fatalf("unable to create channel edge: %v", err)
-	}
+	edge3, chanID3 := createEdge(v, 1000, 0, 0, 0, node1, node2)
+	require.NoError(t, graph.AddChannelEdge(ctx, edge3))
 	bestID, err = graph.HighestChanID(ctx)
 	require.NoError(t, err, "unable to get highest ID")
 
-	if bestID != chanID3.ToUint64() {
-		t.Fatalf("expected %v got %v for best chan ID: ",
-			chanID3.ToUint64(), bestID)
-	}
+	require.Equal(t, chanID3.ToUint64(), bestID)
 }
 
 // TestChanUpdatesInHorizon tests the we're able to properly retrieve all known
@@ -5210,6 +5197,7 @@ func BenchmarkForEachChannel(b *testing.B) {
 // method works as expected, and is able to handle nil self edges.
 func testGraphCacheForEachNodeChannel(t *testing.T,
 	v lnwire.GossipVersion) {
+
 	t.Parallel()
 	ctx := t.Context()
 
diff --git a/graph/db/interfaces.go b/graph/db/interfaces.go
index 9613ff6..752473e 100644
--- a/graph/db/interfaces.go
+++ b/graph/db/interfaces.go
@@ -246,7 +246,8 @@ type Store interface { //nolint:interfacebloat
 	// graph. This represents the "newest" channel from the PoV of the
 	// chain. This method can be used by peers to quickly determine if
 	// they're graphs are in sync.
-	HighestChanID(ctx context.Context) (uint64, error)
+	HighestChanID(ctx context.Context, v lnwire.GossipVersion) (
+		uint64, error)
 
 	// ChanUpdatesInHorizon returns all the known channel edges which have
 	// at least one edge that has an update timestamp within the specified
diff --git a/graph/db/kv_store.go b/graph/db/kv_store.go
index d61713a..2d3fdf8 100644
--- a/graph/db/kv_store.go
+++ b/graph/db/kv_store.go
@@ -2056,7 +2056,13 @@ func getChanID(tx kvdb.RTx, chanPoint *wire.OutPoint) (uint64, error) {
 // HighestChanID returns the "highest" known channel ID in the channel graph.
 // This represents the "newest" channel from the PoV of the chain. This method
 // can be used by peers to quickly determine if they're graphs are in sync.
-func (c *KVStore) HighestChanID(_ context.Context) (uint64, error) {
+func (c *KVStore) HighestChanID(_ context.Context,
+	v lnwire.GossipVersion) (uint64, error) {
+
+	if v != lnwire.GossipVersion1 {
+		return 0, ErrVersionNotSupportedForKVDB
+	}
+
 	var cid uint64
 
 	err := kvdb.View(c.db, func(tx kvdb.RTx) error {
diff --git a/graph/db/sql_store.go b/graph/db/sql_store.go
index 4c64e2e..9bfb851 100644
--- a/graph/db/sql_store.go
+++ b/graph/db/sql_store.go
@@ -786,10 +786,16 @@ func (s *SQLStore) AddChannelEdge(ctx context.Context,
 // can be used by peers to quickly determine if their graphs are in sync.
 //
 // NOTE: This is part of the Store interface.
-func (s *SQLStore) HighestChanID(ctx context.Context) (uint64, error) {
+func (s *SQLStore) HighestChanID(ctx context.Context,
+	v lnwire.GossipVersion) (uint64, error) {
+
 	var highestChanID uint64
 	err := s.db.ExecTx(ctx, sqldb.ReadTxOpt(), func(db SQLQueries) error {
-		chanID, err := db.HighestSCID(ctx, int16(lnwire.GossipVersion1))
+		if !isKnownGossipVersion(v) {
+			return fmt.Errorf("unsupported gossip version: %d", v)
+		}
+
+		chanID, err := db.HighestSCID(ctx, int16(v))
 		if errors.Is(err, sql.ErrNoRows) {
 			return nil
 		} else if err != nil {
diff --git a/server.go b/server.go
index a91d266..91b6624 100644
--- a/server.go
+++ b/server.go
@@ -1042,7 +1042,9 @@ func newServer(ctx context.Context, cfg *Config, listenAddrs []net.Addr,
 		return nil, fmt.Errorf("can't create router: %w", err)
 	}
 
-	chanSeries := discovery.NewChanSeries(s.graphDB)
+	chanSeries := discovery.NewChanSeries(
+		graphdb.NewVersionedGraph(s.graphDB, lnwire.GossipVersion1),
+	)
 	gossipMessageStore, err := discovery.NewMessageStore(dbs.ChanStateDB)
 	if err != nil {
 		return nil, err