watchtower: make use of the new AddressIterator

This commit upgrades the wtclient package to make use of the new
`AddressIterator`. It does so by first creating new `Tower` and
`ClientSession` types. The new `Tower` type has an `AddressIterator`
instead of a list of addresses. The `ClientSession` type contains a
`Tower`.

watchtower/wtclient/candidate_iterator_test.go

@@ -33,31 +33,38 @@ func randAddr(t *testing.T) net.Addr {
 	}
 }
 
-func randTower(t *testing.T) *wtdb.Tower {
+func randTower(t *testing.T) *Tower {
 	t.Helper()
 
 	priv, err := btcec.NewPrivateKey()
 	require.NoError(t, err, "unable to create private key")
 	pubKey := priv.PubKey()
-	return &wtdb.Tower{
+	addrs, err := newAddressIterator(randAddr(t))
+	require.NoError(t, err)
+
+	return &Tower{
 		ID:          wtdb.TowerID(rand.Uint64()),
 		IdentityKey: pubKey,
-		Addresses:   []net.Addr{randAddr(t)},
+		Addresses:   addrs,
 	}
 }
 
-func copyTower(tower *wtdb.Tower) *wtdb.Tower {
-	t := &wtdb.Tower{
+func copyTower(t *testing.T, tower *Tower) *Tower {
+	t.Helper()
+
+	addrs := tower.Addresses.GetAll()
+	addrIterator, err := newAddressIterator(addrs...)
+	require.NoError(t, err)
+
+	return &Tower{
 		ID:          tower.ID,
 		IdentityKey: tower.IdentityKey,
-		Addresses:   make([]net.Addr, len(tower.Addresses)),
+		Addresses:   addrIterator,
 	}
-	copy(t.Addresses, tower.Addresses)
-	return t
 }
 
-func assertActiveCandidate(t *testing.T, i TowerCandidateIterator,
-	c *wtdb.Tower, active bool) {
+func assertActiveCandidate(t *testing.T, i TowerCandidateIterator, c *Tower,
+	active bool) {
 
 	t.Helper()
 
@@ -71,12 +78,14 @@ func assertActiveCandidate(t *testing.T, i TowerCandidateIterator,
 		c.ID)
 }
 
-func assertNextCandidate(t *testing.T, i TowerCandidateIterator, c *wtdb.Tower) {
+func assertNextCandidate(t *testing.T, i TowerCandidateIterator, c *Tower) {
 	t.Helper()
 
 	tower, err := i.Next()
 	require.NoError(t, err)
-	require.Equal(t, c, tower)
+	require.True(t, tower.IdentityKey.IsEqual(c.IdentityKey))
+	require.Equal(t, tower.ID, c.ID)
+	require.Equal(t, tower.Addresses.GetAll(), c.Addresses.GetAll())
 }
 
 // TestTowerCandidateIterator asserts the internal state of a
@@ -88,13 +97,13 @@ func TestTowerCandidateIterator(t *testing.T) {
 	// towers. We'll use copies of these towers within the iterator to
 	// ensure the iterator properly updates the state of its candidates.
 	const numTowers = 4
-	towers := make([]*wtdb.Tower, 0, numTowers)
+	towers := make([]*Tower, 0, numTowers)
 	for i := 0; i < numTowers; i++ {
 		towers = append(towers, randTower(t))
 	}
-	towerCopies := make([]*wtdb.Tower, 0, numTowers)
+	towerCopies := make([]*Tower, 0, numTowers)
 	for _, tower := range towers {
-		towerCopies = append(towerCopies, copyTower(tower))
+		towerCopies = append(towerCopies, copyTower(t, tower))
 	}
 	towerIterator := newTowerListIterator(towerCopies...)
 
@@ -112,13 +121,13 @@ func TestTowerCandidateIterator(t *testing.T) {
 	towerIterator.Reset()
 
 	// We'll then attempt to test the RemoveCandidate behavior of the
-	// iterator. We'll remove the address of the first tower, which should
-	// result in it not having any addresses left, but still being an active
-	// candidate.
+	// iterator. We'll attempt to remove the address of the first tower,
+	// which should result in an error due to it being the last address of
+	// the tower.
 	firstTower := towers[0]
-	firstTowerAddr := firstTower.Addresses[0]
-	firstTower.RemoveAddress(firstTowerAddr)
-	towerIterator.RemoveCandidate(firstTower.ID, firstTowerAddr)
+	firstTowerAddr := firstTower.Addresses.Peek()
+	err = towerIterator.RemoveCandidate(firstTower.ID, firstTowerAddr)
+	require.ErrorIs(t, err, wtdb.ErrLastTowerAddr)
 	assertActiveCandidate(t, towerIterator, firstTower, true)
 	assertNextCandidate(t, towerIterator, firstTower)
 
@@ -126,7 +135,8 @@ func TestTowerCandidateIterator(t *testing.T) {
 	// not providing the optional address. Since it's been removed, we
 	// should expect to see the third tower next.
 	secondTower, thirdTower := towers[1], towers[2]
-	towerIterator.RemoveCandidate(secondTower.ID, nil)
+	err = towerIterator.RemoveCandidate(secondTower.ID, nil)
+	require.NoError(t, err)
 	assertActiveCandidate(t, towerIterator, secondTower, false)
 	assertNextCandidate(t, towerIterator, thirdTower)
 
@@ -135,7 +145,7 @@ func TestTowerCandidateIterator(t *testing.T) {
 	// iterator, but the new address should be.
 	fourthTower := towers[3]
 	assertActiveCandidate(t, towerIterator, fourthTower, true)
-	fourthTower.AddAddress(randAddr(t))
+	fourthTower.Addresses.Add(randAddr(t))
 	towerIterator.AddCandidate(fourthTower)
 	assertNextCandidate(t, towerIterator, fourthTower)