lntypes+routing: add generic Min/Max functions

lntypes/comparison.go

@@ -0,0 +1,26 @@
+package lntypes
+
+import "golang.org/x/exp/constraints"
+
+// Number defines a type constraint for numbers.
+type Number interface {
+	constraints.Integer | constraints.Float
+}
+
+// Max returns the greater of the two inputs.
+func Max[N Number](op1 N, op2 N) N {
+	if op1 > op2 {
+		return op1
+	}
+
+	return op2
+}
+
+// Min returns the lesser of the two inputs.
+func Min[N Number](op1 N, op2 N) N {
+	if op1 < op2 {
+		return op1
+	}
+
+	return op2
+}

lntypes/comparison_test.go

@@ -0,0 +1,25 @@
+package lntypes
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestMin tests getting correct minimal numbers.
+func TestMin(t *testing.T) {
+	t.Parallel()
+
+	require.Equal(t, 1, Min(1, 1))
+	require.Equal(t, 1, Min(1, 2))
+	require.Equal(t, 1.5, Min(1.5, 2.5))
+}
+
+// TestMax tests getting correct maximal numbers.
+func TestMax(t *testing.T) {
+	t.Parallel()
+
+	require.Equal(t, 1, Max(1, 1))
+	require.Equal(t, 2, Max(1, 2))
+	require.Equal(t, 2.5, Max(1.5, 2.5))
+}

routing/unified_edges.go

@@ -3,6 +3,7 @@ package routing
 import (
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 )
@@ -223,9 +224,9 @@ func (u *edgeUnifier) getEdgeNetwork(amt lnwire.MilliSatoshi) *unifiedEdge {
 
 		// Track the maximum time lock of all channels that are
 		// candidate for non-strict forwarding at the routing node.
-		if edge.policy.TimeLockDelta > maxTimelock {
+		maxTimelock = lntypes.Max(
-			maxTimelock = edge.policy.TimeLockDelta
+			maxTimelock, edge.policy.TimeLockDelta,
-		}
+		)
 
 		// Use the policy that results in the highest fee for this
 		// specific amount.
@@ -264,9 +265,7 @@ func (u *edgeUnifier) getEdgeNetwork(amt lnwire.MilliSatoshi) *unifiedEdge {
 func (u *edgeUnifier) minAmt() lnwire.MilliSatoshi {
 	min := lnwire.MaxMilliSatoshi
 	for _, edge := range u.edges {
-		if edge.policy.MinHTLC < min {
+		min = lntypes.Min(min, edge.policy.MinHTLC)
-			min = edge.policy.MinHTLC
-		}
 	}
 
 	return min