sweep: allow specifying starting fee rate for fee func

sweep/sweeper.go

@@ -65,6 +65,10 @@ type Params struct {
 	// without waiting for blocks to come to trigger the sweeping of
 	// inputs.
 	Immediate bool
+
+	// StartingFeeRate is an optional parameter that can be used to specify
+	// the initial fee rate to use for the fee function.
+	StartingFeeRate fn.Option[chainfee.SatPerKWeight]
 }
 
 // ParamsUpdate contains a new set of parameters to update a pending sweep with.
@@ -77,6 +81,10 @@ type ParamsUpdate struct {
 	// Immediate indicates that the input should be swept immediately
 	// without waiting for blocks to come.
 	Immediate bool
+
+	// StartingFeeRate is an optional parameter that can be used to specify
+	// the initial fee rate to use for the fee function.
+	StartingFeeRate fn.Option[chainfee.SatPerKWeight]
 }
 
 // String returns a human readable interpretation of the sweep parameters.
@@ -91,9 +99,9 @@ func (p Params) String() string {
 		exclusiveGroup = fmt.Sprintf("%d", *p.ExclusiveGroup)
 	}
 
-	return fmt.Sprintf("fee=%v, immediate=%v, exclusive_group=%v, budget=%v, "+
-		"deadline=%v", p.Fee, p.Immediate, exclusiveGroup, p.Budget,
-		deadline)
+	return fmt.Sprintf("startingFeeRate=%v, immediate=%v, "+
+		"exclusive_group=%v, budget=%v, deadline=%v", p.StartingFeeRate,
+		p.Immediate, exclusiveGroup, p.Budget, deadline)
 }
 
 // SweepState represents the current state of a pending input.
@@ -830,6 +838,7 @@ func (s *UtxoSweeper) sweep(set InputSet) error {
 		DeadlineHeight:  set.DeadlineHeight(),
 		DeliveryAddress: s.currentOutputScript,
 		MaxFeeRate:      s.cfg.MaxFeeRate.FeePerKWeight(),
+		StartingFeeRate: set.StartingFeeRate(),
 		// TODO(yy): pass the strategy here.
 	}