liquidity: simplify suggest swap to return swap amount

liquidity/liquidity.go

@@ -713,10 +713,10 @@ func (m *Manager) SuggestSwaps(ctx context.Context, autoloop bool) (
 			continue
 		}
 
-		// We can have nil suggestions in the case where no action is
+		// We can have zero amount in the case where no action is
 		// required, so we skip over them.
-		suggestion := rule.suggestSwap(balance, restrictions)
-		if suggestion == nil {
+		amount := rule.swapAmount(balance, restrictions)
+		if amount == 0 {
 			disqualified[balance.channelID] = ReasonLiquidityOk
 			continue
 		}
@@ -724,7 +724,7 @@ func (m *Manager) SuggestSwaps(ctx context.Context, autoloop bool) (
 		// Get a quote for a swap of this amount.
 		quote, err := m.cfg.LoopOutQuote(
 			ctx, &loop.LoopOutQuoteRequest{
-				Amount:                  suggestion.Amount,
+				Amount:                  amount,
 				SweepConfTarget:         m.params.SweepConfTarget,
 				SwapPublicationDeadline: m.cfg.Clock.Now(),
 			},
@@ -734,19 +734,19 @@ func (m *Manager) SuggestSwaps(ctx context.Context, autoloop bool) (
 		}
 
 		log.Debugf("quote for suggestion: %v, swap fee: %v, "+
-			"miner fee: %v, prepay: %v", suggestion, quote.SwapFee,
+			"miner fee: %v, prepay: %v", amount, quote.SwapFee,
 			quote.MinerFee, quote.PrepayAmount)
 
 		// Check that the estimated fees for the suggested swap are
 		// below the fee limits configured by the manager.
-		feeReason := m.checkFeeLimits(quote, suggestion.Amount)
+		feeReason := m.checkFeeLimits(quote, amount)
 		if feeReason != ReasonNone {
 			disqualified[balance.channelID] = feeReason
 			continue
 		}
 
 		outRequest, err := m.makeLoopOutRequest(
-			ctx, suggestion, quote, autoloop,
+			ctx, amount, balance, quote, autoloop,
 		)
 		if err != nil {
 			return nil, err
@@ -871,21 +871,19 @@ func (m *Manager) getSwapRestrictions(ctx context.Context, swapType swap.Type) (
 // dispatched, and decides whether we set a sweep address (we don't bother for
 // non-auto requests, because the client api will set it anyway).
 func (m *Manager) makeLoopOutRequest(ctx context.Context,
-	suggestion *LoopOutRecommendation, quote *loop.LoopOutQuote,
+	amount btcutil.Amount, balance *balances, quote *loop.LoopOutQuote,
 	autoloop bool) (loop.OutRequest, error) {
 
 	prepayMaxFee := ppmToSat(
 		quote.PrepayAmount, m.params.MaximumPrepayRoutingFeePPM,
 	)
 
-	routeMaxFee := ppmToSat(
-		suggestion.Amount, m.params.MaximumRoutingFeePPM,
-	)
+	routeMaxFee := ppmToSat(amount, m.params.MaximumRoutingFeePPM)
 
 	request := loop.OutRequest{
-		Amount: suggestion.Amount,
+		Amount: amount,
 		OutgoingChanSet: loopdb.ChannelSet{
-			suggestion.Channel.ToUint64(),
+			balance.channelID.ToUint64(),
 		},
 		MaxPrepayRoutingFee: prepayMaxFee,
 		MaxSwapRoutingFee:   routeMaxFee,

liquidity/suggestions.go

@@ -1,34 +0,0 @@
-package liquidity
-
-import (
-	"fmt"
-
-	"github.com/btcsuite/btcutil"
-	"github.com/lightningnetwork/lnd/lnwire"
-)
-
-// LoopOutRecommendation contains the information required to recommend a loop
-// out.
-type LoopOutRecommendation struct {
-	// Amount is the total amount to swap.
-	Amount btcutil.Amount
-
-	// Channel is the target outgoing channel.
-	Channel lnwire.ShortChannelID
-}
-
-// String returns a string representation of a loop out recommendation.
-func (l *LoopOutRecommendation) String() string {
-	return fmt.Sprintf("loop out: %v over %v", l.Amount,
-		l.Channel.ToUint64())
-}
-
-// newLoopOutRecommendation creates a new loop out swap.
-func newLoopOutRecommendation(amount btcutil.Amount,
-	channelID lnwire.ShortChannelID) *LoopOutRecommendation {
-
-	return &LoopOutRecommendation{
-		Amount:  amount,
-		Channel: channelID,
-	}
-}

liquidity/threshold_rule.go

@@ -62,10 +62,10 @@ func (r *ThresholdRule) validate() error {
 	return nil
 }
 
-// suggestSwap suggests a swap based on the liquidity thresholds configured,
-// returning nil if no swap is recommended.
-func (r *ThresholdRule) suggestSwap(channel *balances,
-	outRestrictions *Restrictions) *LoopOutRecommendation {
+// swapAmount suggests a swap based on the liquidity thresholds configured,
+// returning zero if no swap is recommended.
+func (r *ThresholdRule) swapAmount(channel *balances,
+	outRestrictions *Restrictions) btcutil.Amount {
 
 	// Examine our total balance and required ratios to decide whether we
 	// need to swap.
@@ -76,17 +76,13 @@ func (r *ThresholdRule) suggestSwap(channel *balances,
 	// Limit our swap amount by the minimum/maximum thresholds set.
 	switch {
 	case amount < outRestrictions.Minimum:
-		return nil
+		return 0
 
 	case amount > outRestrictions.Maximum:
-		return newLoopOutRecommendation(
-			outRestrictions.Maximum, channel.channelID,
-		)
+		return outRestrictions.Maximum
 
 	default:
-		return newLoopOutRecommendation(
-			amount, channel.channelID,
-		)
+		return amount
 	}
 }
 

liquidity/threshold_rule_test.go

@@ -184,7 +184,7 @@ func TestSuggestSwap(t *testing.T) {
 		rule            *ThresholdRule
 		channel         *balances
 		outRestrictions *Restrictions
-		swap            *LoopOutRecommendation
+		swap            btcutil.Amount
 	}{
 		{
 			name:            "liquidity ok",
@@ -205,7 +205,7 @@ func TestSuggestSwap(t *testing.T) {
 				incoming: 0,
 				outgoing: 100,
 			},
-			swap: &LoopOutRecommendation{Amount: 50},
+			swap: 50,
 		},
 		{
 			name:            "amount below minimum",
@@ -216,7 +216,7 @@ func TestSuggestSwap(t *testing.T) {
 				incoming: 0,
 				outgoing: 100,
 			},
-			swap: nil,
+			swap: 0,
 		},
 		{
 			name:            "amount above maximum",
@@ -227,7 +227,7 @@ func TestSuggestSwap(t *testing.T) {
 				incoming: 0,
 				outgoing: 100,
 			},
-			swap: &LoopOutRecommendation{Amount: 20},
+			swap: 20,
 		},
 		{
 			name:            "loop in",
@@ -238,7 +238,7 @@ func TestSuggestSwap(t *testing.T) {
 				incoming: 100,
 				outgoing: 0,
 			},
-			swap: nil,
+			swap: 0,
 		},
 	}
 
@@ -246,7 +246,7 @@ func TestSuggestSwap(t *testing.T) {
 		test := test
 
 		t.Run(test.name, func(t *testing.T) {
-			swap := test.rule.suggestSwap(
+			swap := test.rule.swapAmount(
 				test.channel, test.outRestrictions,
 			)
 			require.Equal(t, test.swap, swap)