invoices: adding InvoiceExpryWatcher to cancel expired invoices

This commit adds InvoiceExpryWatcher which is a separate class that
receives new invoices (and existing ones upon restart) from InvoiceRegistry
and actively watches their expiry. When an invoice is expired
InvoiceExpiryWatcher will call into InvoiceRegistry to cancel the
invoice and by that notify all subscribers about the state change.

invoices/test_utils_test.go

@@ -1,6 +1,7 @@
 package invoices
 
 import (
+	"encoding/binary"
 	"encoding/hex"
 	"fmt"
 	"io/ioutil"
@@ -51,7 +52,7 @@ var (
 	testPrivKeyBytes, _ = hex.DecodeString(
 		"e126f68f7eafcc8b74f54d269fe206be715000f94dac067d1c04a8ca3b2db734")
 
-	testPrivKey, testPubKey = btcec.PrivKeyFromBytes(
+	testPrivKey, _ = btcec.PrivKeyFromBytes(
 		btcec.S256(), testPrivKeyBytes)
 
 	testInvoiceDescription = "coffee"
@@ -75,6 +76,8 @@ var (
 	)
 
 	testPayload = &mockPayload{}
+
+	testInvoiceCreationDate = testTime
 )
 
 var (
@@ -83,16 +86,20 @@ var (
 		Terms: channeldb.ContractTerm{
 			PaymentPreimage: testInvoicePreimage,
 			Value:           testInvoiceAmt,
+			Expiry:          time.Hour,
 			Features:        testFeatures,
 		},
+		CreationDate: testInvoiceCreationDate,
 	}
 
 	testHodlInvoice = &channeldb.Invoice{
 		Terms: channeldb.ContractTerm{
 			PaymentPreimage: channeldb.UnknownPreimage,
 			Value:           testInvoiceAmt,
+			Expiry:          time.Hour,
 			Features:        testFeatures,
 		},
+		CreationDate: testInvoiceCreationDate,
 	}
 )
 
@@ -120,6 +127,7 @@ func newTestChannelDB() (*channeldb.DB, func(), error) {
 }
 
 type testContext struct {
+	cdb      *channeldb.DB
 	registry *InvoiceRegistry
 	clock    *clock.TestClock
 
@@ -136,13 +144,15 @@ func newTestContext(t *testing.T) *testContext {
 	}
 	cdb.Now = clock.Now
 
+	expiryWatcher := NewInvoiceExpiryWatcher(clock)
+
 	// Instantiate and start the invoice ctx.registry.
 	cfg := RegistryConfig{
 		FinalCltvRejectDelta: testFinalCltvRejectDelta,
 		HtlcHoldDuration:     30 * time.Second,
 		Clock:                clock,
 	}
-	registry := NewRegistry(cdb, &cfg)
+	registry := NewRegistry(cdb, expiryWatcher, &cfg)
 
 	err = registry.Start()
 	if err != nil {
@@ -151,6 +161,7 @@ func newTestContext(t *testing.T) *testContext {
 	}
 
 	ctx := testContext{
+		cdb:      cdb,
 		registry: registry,
 		clock:    clock,
 		t:        t,
@@ -172,7 +183,7 @@ func getCircuitKey(htlcID uint64) channeldb.CircuitKey {
 	}
 }
 
-func newTestInvoice(t *testing.T,
+func newTestInvoice(t *testing.T, preimage lntypes.Preimage,
 	timestamp time.Time, expiry time.Duration) *channeldb.Invoice {
 
 	if expiry == 0 {
@@ -181,7 +192,7 @@ func newTestInvoice(t *testing.T,
 
 	rawInvoice, err := zpay32.NewInvoice(
 		testNetParams,
-		testInvoicePaymentHash,
+		preimage.Hash(),
 		timestamp,
 		zpay32.Amount(testInvoiceAmount),
 		zpay32.Description(testInvoiceDescription),
@@ -199,7 +210,7 @@ func newTestInvoice(t *testing.T,
 
 	return &channeldb.Invoice{
 		Terms: channeldb.ContractTerm{
-			PaymentPreimage: testInvoicePreimage,
+			PaymentPreimage: preimage,
 			Value:           testInvoiceAmount,
 			Expiry:          expiry,
 			Features:        testFeatures,
@@ -229,3 +240,41 @@ func timeout() func() {
 		close(done)
 	}
 }
+
+// invoiceExpiryTestData simply holds generated expired and pending invoices.
+type invoiceExpiryTestData struct {
+	expiredInvoices map[lntypes.Hash]*channeldb.Invoice
+	pendingInvoices map[lntypes.Hash]*channeldb.Invoice
+}
+
+// generateInvoiceExpiryTestData generates the specified number of fake expired
+// and pending invoices anchored to the passed now timestamp.
+func generateInvoiceExpiryTestData(
+	t *testing.T, now time.Time,
+	offset, numExpired, numPending int) invoiceExpiryTestData {
+
+	var testData invoiceExpiryTestData
+
+	testData.expiredInvoices = make(map[lntypes.Hash]*channeldb.Invoice)
+	testData.pendingInvoices = make(map[lntypes.Hash]*channeldb.Invoice)
+
+	expiredCreationDate := now.Add(-24 * time.Hour)
+
+	for i := 1; i <= numExpired; i++ {
+		var preimage lntypes.Preimage
+		binary.BigEndian.PutUint32(preimage[:4], uint32(offset+i))
+		expiry := time.Duration((i+offset)%24) * time.Hour
+		invoice := newTestInvoice(t, preimage, expiredCreationDate, expiry)
+		testData.expiredInvoices[preimage.Hash()] = invoice
+	}
+
+	for i := 1; i <= numPending; i++ {
+		var preimage lntypes.Preimage
+		binary.BigEndian.PutUint32(preimage[4:], uint32(offset+i))
+		expiry := time.Duration((i+offset)%24) * time.Hour
+		invoice := newTestInvoice(t, preimage, now, expiry)
+		testData.pendingInvoices[preimage.Hash()] = invoice
+	}
+
+	return testData
+}