swap_server_client: let the SwapPublicationDeadline be set during LoopOuts

interface.go

@@ -66,6 +66,10 @@ type OutRequest struct {
 	// LoopOutChannel optionally specifies the short channel id of the
 	// channel to loop out.
 	LoopOutChannel *uint64
+
+	// SwapPublicationDeadline can be set by the client to allow the server
+	// delaying publication of the swap HTLC to save on chain fees.
+	SwapPublicationDeadline time.Time
 }
 
 // Out contains the full details of a loop out request. This includes things

loopout.go

@@ -79,29 +79,36 @@ func newLoopOutSwap(globalCtx context.Context, cfg *swapConfig,
 	// the server revocation key and the swap and prepay invoices.
 	log.Infof("Initiating swap request at height %v", currentHeight)
 
-	swapResp, err := cfg.server.NewLoopOutSwap(globalCtx, swapHash,
-		request.Amount, receiverKey,
+	// The swap deadline will be given to the server for it to use as the
+	// latest swap publication time.
+	swapResp, err := cfg.server.NewLoopOutSwap(
+		globalCtx, swapHash, request.Amount, receiverKey,
+		request.SwapPublicationDeadline,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("cannot initiate swap: %v", err)
 	}
 
-	err = validateLoopOutContract(cfg.lnd, currentHeight, request, swapHash, swapResp)
+	err = validateLoopOutContract(
+		cfg.lnd, currentHeight, request, swapHash, swapResp,
+	)
 	if err != nil {
 		return nil, err
 	}
 
-	// Instantiate a struct that contains all required data to start the swap.
+	// Instantiate a struct that contains all required data to start the
+	// swap.
 	initiationTime := time.Now()
 
 	contract := loopdb.LoopOutContract{
-		SwapInvoice:         swapResp.swapInvoice,
-		DestAddr:            request.DestAddr,
-		MaxSwapRoutingFee:   request.MaxSwapRoutingFee,
-		SweepConfTarget:     request.SweepConfTarget,
-		UnchargeChannel:     request.LoopOutChannel,
-		PrepayInvoice:       swapResp.prepayInvoice,
-		MaxPrepayRoutingFee: request.MaxPrepayRoutingFee,
+		SwapInvoice:             swapResp.swapInvoice,
+		DestAddr:                request.DestAddr,
+		MaxSwapRoutingFee:       request.MaxSwapRoutingFee,
+		SweepConfTarget:         request.SweepConfTarget,
+		UnchargeChannel:         request.LoopOutChannel,
+		PrepayInvoice:           swapResp.prepayInvoice,
+		MaxPrepayRoutingFee:     request.MaxPrepayRoutingFee,
+		SwapPublicationDeadline: request.SwapPublicationDeadline,
 		SwapContract: loopdb.SwapContract{
 			InitiationHeight: currentHeight,
 			InitiationTime:   initiationTime,

server_mock_test.go

@@ -53,7 +53,7 @@ func newServerMock() *serverMock {
 
 func (s *serverMock) NewLoopOutSwap(ctx context.Context,
 	swapHash lntypes.Hash, amount btcutil.Amount,
-	receiverKey [33]byte) (
+	receiverKey [33]byte, _ time.Time) (
 	*newLoopOutResponse, error) {
 
 	_, senderKey := test.CreateKey(100)

swap_server_client.go

@@ -6,6 +6,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"time"
 
 	"github.com/lightninglabs/loop/looprpc"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -31,7 +32,8 @@ type swapServerClient interface {
 
 	NewLoopOutSwap(ctx context.Context,
 		swapHash lntypes.Hash, amount btcutil.Amount,
-		receiverKey [33]byte) (
+		receiverKey [33]byte,
+		swapPublicationDeadline time.Time) (
 		*newLoopOutResponse, error)
 
 	NewLoopInSwap(ctx context.Context,
@@ -153,15 +155,17 @@ func (s *grpcSwapServerClient) GetLoopInQuote(ctx context.Context,
 
 func (s *grpcSwapServerClient) NewLoopOutSwap(ctx context.Context,
 	swapHash lntypes.Hash, amount btcutil.Amount,
-	receiverKey [33]byte) (*newLoopOutResponse, error) {
+	receiverKey [33]byte, swapPublicationDeadline time.Time) (
+	*newLoopOutResponse, error) {
 
 	rpcCtx, rpcCancel := context.WithTimeout(ctx, serverRPCTimeout)
 	defer rpcCancel()
 	swapResp, err := s.server.NewLoopOutSwap(rpcCtx,
 		&looprpc.ServerLoopOutRequest{
-			SwapHash:    swapHash[:],
-			Amt:         uint64(amount),
-			ReceiverKey: receiverKey[:],
+			SwapHash:                swapHash[:],
+			Amt:                     uint64(amount),
+			ReceiverKey:             receiverKey[:],
+			SwapPublicationDeadline: swapPublicationDeadline.Unix(),
 		},
 	)
 	if err != nil {