rpc: recognize the new unused prefix address types

mock.go

@@ -226,6 +226,11 @@ func (m *mockWalletController) NewAddress(addrType lnwallet.AddressType,
 		m.rootKey.PubKey().SerializeCompressed(), &chaincfg.MainNetParams)
 	return addr, nil
 }
+func (*mockWalletController) LastUnusedAddress(addrType lnwallet.AddressType) (
+	btcutil.Address, error) {
+	return nil, nil
+}
+
 func (*mockWalletController) IsOurAddress(a btcutil.Address) bool {
 	return false
 }

rpcserver.go

@@ -932,19 +932,44 @@ func (r *rpcServer) NewAddress(ctx context.Context,
 
 	// Translate the gRPC proto address type to the wallet controller's
 	// available address types.
-	var addrType lnwallet.AddressType
+	var (
+		addr btcutil.Address
+		err  error
+	)
 	switch in.Type {
 	case lnrpc.AddressType_WITNESS_PUBKEY_HASH:
-		addrType = lnwallet.WitnessPubKey
-	case lnrpc.AddressType_NESTED_PUBKEY_HASH:
-		addrType = lnwallet.NestedWitnessPubKey
-	}
-
-	addr, err := r.server.cc.wallet.NewAddress(addrType, false)
+		addr, err = r.server.cc.wallet.NewAddress(
+			lnwallet.WitnessPubKey, false,
+		)
 		if err != nil {
 			return nil, err
 		}
 
+	case lnrpc.AddressType_NESTED_PUBKEY_HASH:
+		addr, err = r.server.cc.wallet.NewAddress(
+			lnwallet.NestedWitnessPubKey, false,
+		)
+		if err != nil {
+			return nil, err
+		}
+
+	case lnrpc.AddressType_UNUSED_WITNESS_PUBKEY_HASH:
+		addr, err = r.server.cc.wallet.LastUnusedAddress(
+			lnwallet.WitnessPubKey,
+		)
+		if err != nil {
+			return nil, err
+		}
+
+	case lnrpc.AddressType_UNUSED_NESTED_PUBKEY_HASH:
+		addr, err = r.server.cc.wallet.LastUnusedAddress(
+			lnwallet.NestedWitnessPubKey,
+		)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	rpcsLog.Infof("[newaddress] addr=%v", addr.String())
 	return &lnrpc.NewAddressResponse{Address: addr.String()}, nil
 }