watchtower: start using the new channel max heights

This commit also adds tests for the DB changes made in the previous
commit since we can now read the new field with the FetchChanInfos
method.

The commit following this one does the backfill migration.

watchtower/wtdb/client_db_test.go

@@ -156,13 +156,13 @@ func (h *clientDBHarness) loadTowerByID(id wtdb.TowerID,
 	return tower
 }
 
-func (h *clientDBHarness) fetchChanSummaries() map[lnwire.ChannelID]wtdb.ClientChanSummary {
+func (h *clientDBHarness) fetchChanInfos() wtdb.ChannelInfos {
 	h.t.Helper()
 
-	summaries, err := h.db.FetchChanSummaries()
+	infos, err := h.db.FetchChanInfos()
 	require.NoError(h.t, err)
 
-	return summaries
+	return infos
 }
 
 func (h *clientDBHarness) registerChan(chanID lnwire.ChannelID,
@@ -552,7 +552,7 @@ func testRemoveTower(h *clientDBHarness) {
 func testChanSummaries(h *clientDBHarness) {
 	// First, assert that this channel is not already registered.
 	var chanID lnwire.ChannelID
-	_, ok := h.fetchChanSummaries()[chanID]
+	_, ok := h.fetchChanInfos()[chanID]
 	require.Falsef(h.t, ok, "pkscript for channel %x should not exist yet",
 		chanID)
 
@@ -565,7 +565,7 @@ func testChanSummaries(h *clientDBHarness) {
 
 	// Assert that the channel exists and that its sweep pkscript matches
 	// the one we registered.
-	summary, ok := h.fetchChanSummaries()[chanID]
+	summary, ok := h.fetchChanInfos()[chanID]
 	require.Truef(h.t, ok, "pkscript for channel %x should not exist yet",
 		chanID)
 	require.Equal(h.t, expPkScript, summary.SweepPkScript)
@@ -767,6 +767,58 @@ func testRogueUpdates(h *clientDBHarness) {
 	require.Len(h.t, closableSessionsMap, 1)
 }
 
+// testMaxCommitmentHeights tests that the max known commitment height of a
+// channel is properly persisted.
+func testMaxCommitmentHeights(h *clientDBHarness) {
+	const maxUpdates = 5
+	t := h.t
+
+	// Initially, we expect no channels.
+	infos := h.fetchChanInfos()
+	require.Empty(t, infos)
+
+	// Create a new tower.
+	tower := h.newTower()
+
+	// Create and insert a new session.
+	session1 := h.randSession(t, tower.ID, maxUpdates)
+	h.insertSession(session1, nil)
+
+	// Create a new channel and register it.
+	chanID1 := randChannelID(t)
+	h.registerChan(chanID1, nil, nil)
+
+	// At this point, we expect one channel to be returned from
+	// fetchChanInfos but with an unset max height.
+	infos = h.fetchChanInfos()
+	require.Len(t, infos, 1)
+
+	info, ok := infos[chanID1]
+	require.True(t, ok)
+	require.True(t, info.MaxHeight.IsNone())
+
+	// Commit and ACK some updates for this channel.
+	for i := 1; i <= maxUpdates; i++ {
+		update := randCommittedUpdateForChanWithHeight(
+			t, chanID1, uint16(i), uint64(i-1),
+		)
+		lastApplied := h.commitUpdate(&session1.ID, update, nil)
+		h.ackUpdate(&session1.ID, uint16(i), lastApplied, nil)
+	}
+
+	// Assert that the max height has now been set accordingly for this
+	// channel.
+	infos = h.fetchChanInfos()
+	require.Len(t, infos, 1)
+
+	info, ok = infos[chanID1]
+	require.True(t, ok)
+	require.True(t, info.MaxHeight.IsSome())
+	info.MaxHeight.WhenSome(func(u uint64) {
+		require.EqualValues(t, maxUpdates-1, u)
+	})
+}
+
 // testMarkChannelClosed asserts the behaviour of MarkChannelClosed.
 func testMarkChannelClosed(h *clientDBHarness) {
 	tower := h.newTower()
@@ -1097,6 +1149,10 @@ func TestClientDB(t *testing.T) {
 			name: "rogue updates",
 			run:  testRogueUpdates,
 		},
+		{
+			name: "max commitment heights",
+			run:  testMaxCommitmentHeights,
+		},
 	}
 
 	for _, database := range dbs {