From 51258af02572a9f201a69994f9b2b40c5dc68ca1 Mon Sep 17 00:00:00 2001
From: Slyghtning <hieblmi@protonmail.com>
Date: Wed, 1 Oct 2025 08:49:32 +0200
Subject: [PATCH] staticaddr: fast-flag support

--fast allows the client to expedite the publishing
of on-chain swap transactions with change, e.g. if --amount was specified.
---
 interface.go                   | 11 +++++++++++
 staticaddr/loopin/actions.go   |  1 +
 staticaddr/loopin/interface.go |  4 ++--
 staticaddr/loopin/loopin.go    |  4 ++++
 staticaddr/loopin/manager.go   |  7 ++++---
 staticaddr/loopin/sql_store.go |  2 ++
 6 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/interface.go b/interface.go
index 1ca1fda3..67b9f831 100644
--- a/interface.go
+++ b/interface.go
@@ -343,6 +343,11 @@ type StaticAddressLoopInRequest struct {
 	// the user did not select an amount, the amount of the selected
 	// deposits is used.
 	SelectedAmount btcutil.Amount
+
+	// Fast indicates whether the user requested a fast static loop-in. If
+	// set, the flag is passed to the server which may alter its behavior
+	// (for example, publish sooner) and is stored in the database.
+	Fast bool
 }
 
 // LoopInTerms are the server terms on which it executes loop in swaps.
@@ -405,6 +410,12 @@ type LoopInQuoteRequest struct {
 	// per-input service fee. This is to cover for the increased on-chain
 	// fee the server has to pay when the sweeping transaction is broadcast.
 	NumDeposits uint32
+
+	// Fast indicates whether the user requested a fast static loop-in
+	// publication on-chain. This is helpful if swap change needs to get
+	// confirmed fast. This comes at a higher swap cost since the server has
+	// to pay more on-chain fees.
+	Fast bool
 }
 
 // LoopInQuote contains estimates for the fees making up the total swap cost
diff --git a/staticaddr/loopin/actions.go b/staticaddr/loopin/actions.go
index 1cd7d509..bf896330 100644
--- a/staticaddr/loopin/actions.go
+++ b/staticaddr/loopin/actions.go
@@ -135,6 +135,7 @@ func (f *FSM) InitHtlcAction(ctx context.Context,
 		ProtocolVersion:       version.CurrentRPCProtocolVersion(),
 		UserAgent:             loop.UserAgent(f.loopIn.Initiator),
 		PaymentTimeoutSeconds: f.loopIn.PaymentTimeoutSeconds,
+		Fast:                  f.loopIn.Fast,
 	}
 	if f.loopIn.LastHop != nil {
 		loopInReq.LastHop = f.loopIn.LastHop
diff --git a/staticaddr/loopin/interface.go b/staticaddr/loopin/interface.go
index 7efdf7e3..c4582730 100644
--- a/staticaddr/loopin/interface.go
+++ b/staticaddr/loopin/interface.go
@@ -91,8 +91,8 @@ type QuoteGetter interface {
 	// GetLoopInQuote returns a quote for a loop-in swap.
 	GetLoopInQuote(ctx context.Context, amt btcutil.Amount,
 		pubKey route.Vertex, lastHop *route.Vertex,
-		routeHints [][]zpay32.HopHint,
-		initiator string, numDeposits uint32) (*loop.LoopInQuote, error)
+		routeHints [][]zpay32.HopHint, initiator string,
+		numDeposits uint32, fast bool) (*loop.LoopInQuote, error)
 }
 
 type NotificationManager interface {
diff --git a/staticaddr/loopin/loopin.go b/staticaddr/loopin/loopin.go
index 1e198f4f..cca73bab 100644
--- a/staticaddr/loopin/loopin.go
+++ b/staticaddr/loopin/loopin.go
@@ -101,6 +101,10 @@ type StaticAddressLoopIn struct {
 	// used.
 	SelectedAmount btcutil.Amount
 
+	// Fast indicates whether the client requested fast publication behavior
+	// on the server side for this static loop in.
+	Fast bool
+
 	// state is the current state of the swap.
 	state fsm.StateType
 
diff --git a/staticaddr/loopin/manager.go b/staticaddr/loopin/manager.go
index 44c1343b..478b85f4 100644
--- a/staticaddr/loopin/manager.go
+++ b/staticaddr/loopin/manager.go
@@ -743,14 +743,14 @@ func (m *Manager) initiateLoopIn(ctx context.Context,
 	numDeposits := uint32(len(selectedDeposits))
 	quote, err := m.cfg.QuoteGetter.GetLoopInQuote(
 		ctx, swapAmount, m.cfg.NodePubkey, req.LastHop, req.RouteHints,
-		req.Initiator, numDeposits,
+		req.Initiator, numDeposits, req.Fast,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("unable to get loop in quote: %w", err)
 	}
 
-	// If the previously accepted quote fee is lower than what is quoted now
-	// we abort the swap.
+	// If the previously accepted quote fee is lower than what is quoted, we
+	// abort the swap.
 	if quote.SwapFee > req.MaxSwapFee {
 		log.Warnf("Swap fee %v exceeding maximum of %v",
 			quote.SwapFee, req.MaxSwapFee)
@@ -774,6 +774,7 @@ func (m *Manager) initiateLoopIn(ctx context.Context,
 		QuotedSwapFee:         quote.SwapFee,
 		MaxSwapFee:            req.MaxSwapFee,
 		PaymentTimeoutSeconds: paymentTimeoutSeconds,
+		Fast:                  req.Fast,
 	}
 	if req.LastHop != nil {
 		swap.LastHop = req.LastHop[:]
diff --git a/staticaddr/loopin/sql_store.go b/staticaddr/loopin/sql_store.go
index e291680d..da4c9298 100644
--- a/staticaddr/loopin/sql_store.go
+++ b/staticaddr/loopin/sql_store.go
@@ -278,6 +278,7 @@ func (s *SqlStore) CreateLoopIn(ctx context.Context,
 		DepositOutpoints:        joinedOutpoints,
 		SelectedAmount:          int64(loopIn.SelectedAmount),
 		PaymentTimeoutSeconds:   int32(loopIn.PaymentTimeoutSeconds),
+		Fast:                    loopIn.Fast,
 	}
 
 	updateArgs := sqlc.InsertStaticAddressMetaUpdateParams{
@@ -581,6 +582,7 @@ func toStaticAddressLoopIn(_ context.Context, network *chaincfg.Params,
 		QuotedSwapFee:         btcutil.Amount(swap.QuotedSwapFeeSatoshis),
 		DepositOutpoints:      depositOutpoints,
 		SelectedAmount:        btcutil.Amount(swap.SelectedAmount),
+		Fast:                  swap.Fast,
 		HtlcTxFeeRate: chainfee.SatPerKWeight(
 			swap.HtlcTxFeeRateSatKw,
 		),