continue loop-in

Author: hieblmi

loopdb/sqlc/migrations/000021_static_change_address.down.sql

@@ -0,0 +1 @@
+ALTER TABLE static_address_swaps DROP COLUMN change_address;

loopdb/sqlc/migrations/000021_static_change_address.up.sql

@@ -0,0 +1,3 @@
+-- change_address stores the change output address for the HTLC transaction of a
+-- static address loop-in swap.
+ALTER TABLE static_address_swaps ADD change_address TEXT NOT NULL DEFAULT '';

loopdb/sqlc/models.go

@@ -7,6 +7,7 @@ INSERT INTO static_address_swaps (
     quoted_swap_fee_satoshis,
     deposit_outpoints,
     selected_amount,
+    change_address,
     htlc_tx_fee_rate_sat_kw,
     htlc_timeout_sweep_tx_id,
     htlc_timeout_sweep_address
@@ -20,7 +21,8 @@ INSERT INTO static_address_swaps (
     $7,
     $8,
     $9,
-    $10
+    $10,
+    $11
 );
 
 -- name: UpdateStaticAddressLoopIn :exec

loopdb/sqlc/queries/static_address_loopin.sql

@@ -16,6 +16,7 @@ import (
 	"github.com/lightninglabs/lndclient"
 	"github.com/lightninglabs/loop"
 	"github.com/lightninglabs/loop/fsm"
+	"github.com/lightninglabs/loop/staticaddr/address"
 	"github.com/lightninglabs/loop/staticaddr/deposit"
 	"github.com/lightninglabs/loop/staticaddr/version"
 	"github.com/lightninglabs/loop/swap"
@@ -63,15 +64,53 @@ func (f *FSM) InitHtlcAction(ctx context.Context,
 
 	// Calculate the swap invoice amount. The server needs to pay us the
 	// swap amount minus the fees that the server charges for the swap. The
-	// swap amount is either the total value of the selected deposits, or
-	// the selected amount if a specific amount was requested.
-	swapAmount := f.loopIn.TotalDepositAmount()
-	var hasChange bool
+	// swap amount is either the total value of the selected deposits or the
+	// selected amount if a specific amount was requested. If the selection
+	// results in change, we create a new static address for it.
+	var (
+		swapAmount       = f.loopIn.TotalDepositAmount()
+		hasChange        bool
+		changeAddrParams *address.Parameters
+	)
 	if f.loopIn.SelectedAmount > 0 {
 		swapAmount = f.loopIn.SelectedAmount
 		remainingAmount := f.loopIn.TotalDepositAmount() - swapAmount
 		hasChange = remainingAmount > 0 && remainingAmount <
 			f.loopIn.TotalDepositAmount()
+
+		if hasChange {
+			changeAddrParams, err = f.cfg.AddressManager.NewAddress(
+				ctx,
+			)
+			if err != nil {
+				err = fmt.Errorf("unable to create change "+
+					"address: %w", err)
+
+				return f.HandleError(err)
+			}
+
+			taprootAddress, err := changeAddrParams.TaprootAddress(
+				f.cfg.ChainParams,
+			)
+			if err != nil {
+				err = fmt.Errorf("unable to create taproot "+
+					"address: %w", err)
+
+				return f.HandleError(err)
+			}
+
+			changeAddress, err := btcutil.DecodeAddress(
+				taprootAddress, f.cfg.ChainParams,
+			)
+			if err != nil {
+				err = fmt.Errorf("unable to decode change "+
+					"address: %w", err)
+
+				return f.HandleError(err)
+			}
+
+			f.loopIn.ChangeAddress = changeAddress
+		}
 	}
 	swapInvoiceAmt := swapAmount - f.loopIn.QuotedSwapFee
 
@@ -124,6 +163,7 @@ func (f *FSM) InitHtlcAction(ctx context.Context,
 		SwapHash:              f.loopIn.SwapHash[:],
 		DepositOutpoints:      f.loopIn.DepositOutpoints,
 		Amount:                uint64(f.loopIn.SelectedAmount),
+		ChangeAddress:         f.loopIn.ChangeAddress.String(),
 		HtlcClientPubKey:      f.loopIn.ClientPubkey.SerializeCompressed(),
 		SwapInvoice:           f.loopIn.SwapInvoice,
 		ProtocolVersion:       version.CurrentRPCProtocolVersion(),

loopdb/sqlc/static_address_loopin.sql.go

@@ -6,6 +6,7 @@ import (
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/lightninglabs/loop"
 	"github.com/lightninglabs/loop/fsm"
+	"github.com/lightninglabs/loop/staticaddr/address"
 	"github.com/lightninglabs/loop/staticaddr/deposit"
 	"github.com/lightninglabs/loop/swapserverrpc"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -21,6 +22,9 @@ type (
 
 // AddressManager handles fetching of address parameters.
 type AddressManager interface {
+	// NewAddress returns a new static address.
+	NewAddress(ctx context.Context) (*address.Parameters, error)
+
 	// IsOutPkScript returns true if the given pkScript is our static
 	// address script.
 	IsOutPkScript(pkScript []byte) (bool, error)

staticaddr/loopin/actions.go

@@ -277,6 +277,7 @@ func (s *SqlStore) CreateLoopIn(ctx context.Context,
 		HtlcTxFeeRateSatKw:      int64(loopIn.HtlcTxFeeRate),
 		DepositOutpoints:        joinedOutpoints,
 		SelectedAmount:          int64(loopIn.SelectedAmount),
+		ChangeAddress:           loopIn.ChangeAddress.String(),
 		PaymentTimeoutSeconds:   int32(loopIn.PaymentTimeoutSeconds),
 	}
 
@@ -564,6 +565,11 @@ func toStaticAddressLoopIn(_ context.Context, network *chaincfg.Params,
 		depositList = append(depositList, deposit)
 	}
 
+	changeAddress, err := btcutil.DecodeAddress(swap.ChangeAddress, network)
+	if err != nil {
+		return nil, err
+	}
+
 	loopIn := &StaticAddressLoopIn{
 		SwapHash:         swapHash,
 		SwapPreimage:     swapPreImage,
@@ -587,6 +593,7 @@ func toStaticAddressLoopIn(_ context.Context, network *chaincfg.Params,
 		QuotedSwapFee:         btcutil.Amount(swap.QuotedSwapFeeSatoshis),
 		DepositOutpoints:      depositOutpoints,
 		SelectedAmount:        btcutil.Amount(swap.SelectedAmount),
+		ChangeAddress:         changeAddress,
 		HtlcTxFeeRate: chainfee.SatPerKWeight(
 			swap.HtlcTxFeeRateSatKw,
 		),