channeldb: split cancel and add htlc updates

Previously the cancel and add actions were combined in a single map.
Nil values implictly signaled cancel actions. This wasn't very obvious.
Furthermore this split prepares for processing the adds and cancels
separately, which is more efficient if there are already two maps.

channeldb/invoice_test.go

@@ -686,7 +686,7 @@ func getUpdateInvoice(amt lnwire.MilliSatoshi) InvoiceUpdateCallback {
 		update := &InvoiceUpdateDesc{
 			Preimage: invoice.Terms.PaymentPreimage,
 			State:    ContractSettled,
-			Htlcs: map[CircuitKey]*HtlcAcceptDesc{
+			AddHtlcs: map[CircuitKey]*HtlcAcceptDesc{
 				{}: {
 					Amt: amt,
 				},

channeldb/invoices.go

@@ -316,10 +316,12 @@ type InvoiceUpdateDesc struct {
 	// State is the new state that this invoice should progress to.
 	State ContractState
 
-	// Htlcs describes the changes that need to be made to the invoice htlcs
+	// CancelHtlcs describes the htlcs that need to be canceled.
-	// in the database. Htlc map entries with their value set should be
+	CancelHtlcs map[CircuitKey]struct{}
-	// added. If the map value is nil, the htlc should be canceled.
+
-	Htlcs map[CircuitKey]*HtlcAcceptDesc
+	// AddHtlcs describes the newly accepted htlcs that need to be added to
+	// the invoice.
+	AddHtlcs map[CircuitKey]*HtlcAcceptDesc
 
 	// Preimage must be set to the preimage when state is settled.
 	Preimage lntypes.Preimage
@@ -1251,12 +1253,9 @@ func (d *DB) updateInvoice(hash lntypes.Hash, invoices, settleIndex *bbolt.Bucke
 
 	now := d.Now()
 
-	// Update htlc set.
+	// Process cancel actions from update descriptor.
-	for key, htlcUpdate := range update.Htlcs {
+	for key := range update.CancelHtlcs {
 		htlc, ok := invoice.Htlcs[key]
-
-		// No update means the htlc needs to be canceled.
-		if htlcUpdate == nil {
 		if !ok {
 			return nil, fmt.Errorf("unknown htlc %v", key)
 		}
@@ -1268,10 +1267,12 @@ func (d *DB) updateInvoice(hash lntypes.Hash, invoices, settleIndex *bbolt.Bucke
 		htlc.State = HtlcStateCanceled
 		htlc.ResolveTime = now
 		invoice.AmtPaid -= htlc.Amt
-
-			continue
 	}
 
+	// Process add actions from update descriptor.
+	for key, htlcUpdate := range update.AddHtlcs {
+		htlc, ok := invoice.Htlcs[key]
+
 		// Add new htlc paying to the invoice.
 		if ok {
 			return nil, fmt.Errorf("htlc %v already exists", key)

invoices/invoiceregistry.go

@@ -598,7 +598,7 @@ func (i *InvoiceRegistry) CancelInvoice(payHash lntypes.Hash) error {
 
 		// Mark individual held htlcs as canceled.
 		canceledHtlcs := make(
-			map[channeldb.CircuitKey]*channeldb.HtlcAcceptDesc,
+			map[channeldb.CircuitKey]struct{},
 		)
 		for key, htlc := range invoice.Htlcs {
 			switch htlc.State {
@@ -615,12 +615,12 @@ func (i *InvoiceRegistry) CancelInvoice(payHash lntypes.Hash) error {
 				continue
 			}
 
-			canceledHtlcs[key] = nil
+			canceledHtlcs[key] = struct{}{}
 		}
 
 		// Move invoice to the canceled state.
 		return &channeldb.InvoiceUpdateDesc{
-			Htlcs: canceledHtlcs,
+			CancelHtlcs: canceledHtlcs,
 			State:       channeldb.ContractCanceled,
 		}, nil
 	}

invoices/update.go

@@ -130,7 +130,9 @@ func updateInvoice(ctx *invoiceUpdateCtx, inv *channeldb.Invoice) (
 		},
 	}
 
-	update := channeldb.InvoiceUpdateDesc{Htlcs: newHtlcs}
+	update := channeldb.InvoiceUpdateDesc{
+		AddHtlcs: newHtlcs,
+	}
 
 	// Don't update invoice state if we are accepting a duplicate payment.
 	// We do accept or settle the HTLC.