lnd/channeldb/invoice_test.go

package channeldb

import (
	"crypto/rand"
	mrand "math/rand"
	"reflect"
	"testing"
	"time"

	"github.com/davecgh/go-spew/spew"
	"github.com/lightningnetwork/lnd/lntypes"
	"github.com/lightningnetwork/lnd/lnwire"
	"github.com/lightningnetwork/lnd/record"
)

var (
	emptyFeatures = lnwire.NewFeatureVector(nil, lnwire.Features)
)

func randInvoice(value lnwire.MilliSatoshi) (*Invoice, error) {
	var pre [32]byte
	if _, err := rand.Read(pre[:]); err != nil {
		return nil, err
	}

	i := &Invoice{
		// Use single second precision to avoid false positive test
		// failures due to the monotonic time component.
		CreationDate: time.Unix(time.Now().Unix(), 0),
		Terms: ContractTerm{
			Expiry:          4000,
			PaymentPreimage: pre,
			Value:           value,
			Features:        emptyFeatures,
		},
		Htlcs: map[CircuitKey]*InvoiceHTLC{},
	}
	i.Memo = []byte("memo")

	// Create a random byte slice of MaxPaymentRequestSize bytes to be used
	// as a dummy paymentrequest, and  determine if it should be set based
	// on one of the random bytes.
	var r [MaxPaymentRequestSize]byte
	if _, err := rand.Read(r[:]); err != nil {
		return nil, err
	}
	if r[0]&1 == 0 {
		i.PaymentRequest = r[:]
	} else {
		i.PaymentRequest = []byte("")
	}

	return i, nil
}

func TestInvoiceWorkflow(t *testing.T) {
	t.Parallel()

	db, cleanUp, err := makeTestDB()
	defer cleanUp()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}

	// Create a fake invoice which we'll use several times in the tests
	// below.
	fakeInvoice := &Invoice{
		// Use single second precision to avoid false positive test
		// failures due to the monotonic time component.
		CreationDate: time.Unix(time.Now().Unix(), 0),
		Htlcs:        map[CircuitKey]*InvoiceHTLC{},
	}
	fakeInvoice.Memo = []byte("memo")
	fakeInvoice.PaymentRequest = []byte("")
	copy(fakeInvoice.Terms.PaymentPreimage[:], rev[:])
	fakeInvoice.Terms.Value = lnwire.NewMSatFromSatoshis(10000)
	fakeInvoice.Terms.Features = emptyFeatures

	paymentHash := fakeInvoice.Terms.PaymentPreimage.Hash()

	// Add the invoice to the database, this should succeed as there aren't
	// any existing invoices within the database with the same payment
	// hash.
	if _, err := db.AddInvoice(fakeInvoice, paymentHash); err != nil {
		t.Fatalf("unable to find invoice: %v", err)
	}

	// Attempt to retrieve the invoice which was just added to the
	// database. It should be found, and the invoice returned should be
	// identical to the one created above.
	dbInvoice, err := db.LookupInvoice(paymentHash)
	if err != nil {
		t.Fatalf("unable to find invoice: %v", err)
	}
	if !reflect.DeepEqual(*fakeInvoice, dbInvoice) {
		t.Fatalf("invoice fetched from db doesn't match original %v vs %v",
			spew.Sdump(fakeInvoice), spew.Sdump(dbInvoice))
	}

	// The add index of the invoice retrieved from the database should now
	// be fully populated. As this is the first index written to the DB,
	// the addIndex should be 1.
	if dbInvoice.AddIndex != 1 {
		t.Fatalf("wrong add index: expected %v, got %v", 1,
			dbInvoice.AddIndex)
	}

	// Settle the invoice, the version retrieved from the database should
	// now have the settled bit toggle to true and a non-default
	// SettledDate
	payAmt := fakeInvoice.Terms.Value * 2
	_, err = db.UpdateInvoice(paymentHash, getUpdateInvoice(payAmt))
	if err != nil {
		t.Fatalf("unable to settle invoice: %v", err)
	}
	dbInvoice2, err := db.LookupInvoice(paymentHash)
	if err != nil {
		t.Fatalf("unable to fetch invoice: %v", err)
	}
	if dbInvoice2.State != ContractSettled {
		t.Fatalf("invoice should now be settled but isn't")
	}
	if dbInvoice2.SettleDate.IsZero() {
		t.Fatalf("invoice should have non-zero SettledDate but isn't")
	}

	// Our 2x payment should be reflected, and also the settle index of 1
	// should also have been committed for this index.
	if dbInvoice2.AmtPaid != payAmt {
		t.Fatalf("wrong amt paid: expected %v, got %v", payAmt,
			dbInvoice2.AmtPaid)
	}
	if dbInvoice2.SettleIndex != 1 {
		t.Fatalf("wrong settle index: expected %v, got %v", 1,
			dbInvoice2.SettleIndex)
	}

	// Attempt to insert generated above again, this should fail as
	// duplicates are rejected by the processing logic.
	if _, err := db.AddInvoice(fakeInvoice, paymentHash); err != ErrDuplicateInvoice {
		t.Fatalf("invoice insertion should fail due to duplication, "+
			"instead %v", err)
	}

	// Attempt to look up a non-existent invoice, this should also fail but
	// with a "not found" error.
	var fakeHash [32]byte
	if _, err := db.LookupInvoice(fakeHash); err != ErrInvoiceNotFound {
		t.Fatalf("lookup should have failed, instead %v", err)
	}

	// Add 10 random invoices.
	const numInvoices = 10
	amt := lnwire.NewMSatFromSatoshis(1000)
	invoices := make([]*Invoice, numInvoices+1)
	invoices[0] = &dbInvoice2
	for i := 1; i < len(invoices)-1; i++ {
		invoice, err := randInvoice(amt)
		if err != nil {
			t.Fatalf("unable to create invoice: %v", err)
		}

		hash := invoice.Terms.PaymentPreimage.Hash()
		if _, err := db.AddInvoice(invoice, hash); err != nil {
			t.Fatalf("unable to add invoice %v", err)
		}

		invoices[i] = invoice
	}

	// Perform a scan to collect all the active invoices.
	dbInvoices, err := db.FetchAllInvoices(false)
	if err != nil {
		t.Fatalf("unable to fetch all invoices: %v", err)
	}

	// The retrieve list of invoices should be identical as since we're
	// using big endian, the invoices should be retrieved in ascending
	// order (and the primary key should be incremented with each
	// insertion).
	for i := 0; i < len(invoices)-1; i++ {
		if !reflect.DeepEqual(*invoices[i], dbInvoices[i]) {
			t.Fatalf("retrieved invoices don't match %v vs %v",
				spew.Sdump(invoices[i]),
				spew.Sdump(dbInvoices[i]))
		}
	}
}

// TestInvoiceCancelSingleHtlc tests that a single htlc can be canceled on the
// invoice.
func TestInvoiceCancelSingleHtlc(t *testing.T) {
	t.Parallel()

	db, cleanUp, err := makeTestDB()
	defer cleanUp()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}

	testInvoice := &Invoice{
		Htlcs: map[CircuitKey]*InvoiceHTLC{},
	}
	testInvoice.Terms.Value = lnwire.NewMSatFromSatoshis(10000)
	testInvoice.Terms.Features = emptyFeatures

	var paymentHash lntypes.Hash
	if _, err := db.AddInvoice(testInvoice, paymentHash); err != nil {
		t.Fatalf("unable to find invoice: %v", err)
	}

	// Accept an htlc on this invoice.
	key := CircuitKey{ChanID: lnwire.NewShortChanIDFromInt(1), HtlcID: 4}
	htlc := HtlcAcceptDesc{
		Amt:           500,
		CustomRecords: make(record.CustomSet),
	}
	invoice, err := db.UpdateInvoice(paymentHash,
		func(invoice *Invoice) (*InvoiceUpdateDesc, error) {
			return &InvoiceUpdateDesc{
				AddHtlcs: map[CircuitKey]*HtlcAcceptDesc{
					key: &htlc,
				},
			}, nil
		})
	if err != nil {
		t.Fatalf("unable to add invoice htlc: %v", err)
	}
	if len(invoice.Htlcs) != 1 {
		t.Fatalf("expected the htlc to be added")
	}
	if invoice.Htlcs[key].State != HtlcStateAccepted {
		t.Fatalf("expected htlc in state accepted")
	}

	// Cancel the htlc again.
	invoice, err = db.UpdateInvoice(paymentHash, func(invoice *Invoice) (*InvoiceUpdateDesc, error) {
		return &InvoiceUpdateDesc{
			CancelHtlcs: map[CircuitKey]struct{}{
				key: {},
			},
		}, nil
	})
	if err != nil {
		t.Fatalf("unable to cancel htlc: %v", err)
	}
	if len(invoice.Htlcs) != 1 {
		t.Fatalf("expected the htlc to be present")
	}
	if invoice.Htlcs[key].State != HtlcStateCanceled {
		t.Fatalf("expected htlc in state canceled")
	}
}

// TestInvoiceTimeSeries tests that newly added invoices invoices, as well as
// settled invoices are added to the database are properly placed in the add
// add or settle index which serves as an event time series.
func TestInvoiceAddTimeSeries(t *testing.T) {
	t.Parallel()

	db, cleanUp, err := makeTestDB()
	defer cleanUp()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}

	// We'll start off by creating 20 random invoices, and inserting them
	// into the database.
	const numInvoices = 20
	amt := lnwire.NewMSatFromSatoshis(1000)
	invoices := make([]Invoice, numInvoices)
	for i := 0; i < len(invoices); i++ {
		invoice, err := randInvoice(amt)
		if err != nil {
			t.Fatalf("unable to create invoice: %v", err)
		}

		paymentHash := invoice.Terms.PaymentPreimage.Hash()

		if _, err := db.AddInvoice(invoice, paymentHash); err != nil {
			t.Fatalf("unable to add invoice %v", err)
		}

		invoices[i] = *invoice
	}

	// With the invoices constructed, we'll now create a series of queries
	// that we'll use to assert expected return values of
	// InvoicesAddedSince.
	addQueries := []struct {
		sinceAddIndex uint64

		resp []Invoice
	}{
		// If we specify a value of zero, we shouldn't get any invoices
		// back.
		{
			sinceAddIndex: 0,
		},

		// If we specify a value well beyond the number of inserted
		// invoices, we shouldn't get any invoices back.
		{
			sinceAddIndex: 99999999,
		},

		// Using an index of 1 should result in all values, but the
		// first one being returned.
		{
			sinceAddIndex: 1,
			resp:          invoices[1:],
		},

		// If we use an index of 10, then we should retrieve the
		// reaming 10 invoices.
		{
			sinceAddIndex: 10,
			resp:          invoices[10:],
		},
	}

	for i, query := range addQueries {
		resp, err := db.InvoicesAddedSince(query.sinceAddIndex)
		if err != nil {
			t.Fatalf("unable to query: %v", err)
		}

		if !reflect.DeepEqual(query.resp, resp) {
			t.Fatalf("test #%v: expected %v, got %v", i,
				spew.Sdump(query.resp), spew.Sdump(resp))
		}
	}

	// We'll now only settle the latter half of each of those invoices.
	for i := 10; i < len(invoices); i++ {
		invoice := &invoices[i]

		paymentHash := invoice.Terms.PaymentPreimage.Hash()

		_, err := db.UpdateInvoice(
			paymentHash, getUpdateInvoice(0),
		)
		if err != nil {
			t.Fatalf("unable to settle invoice: %v", err)
		}
	}

	invoices, err = db.FetchAllInvoices(false)
	if err != nil {
		t.Fatalf("unable to fetch invoices: %v", err)
	}

	// We'll slice off the first 10 invoices, as we only settled the last
	// 10.
	invoices = invoices[10:]

	// We'll now prepare an additional set of queries to ensure the settle
	// time series has properly been maintained in the database.
	settleQueries := []struct {
		sinceSettleIndex uint64

		resp []Invoice
	}{
		// If we specify a value of zero, we shouldn't get any settled
		// invoices back.
		{
			sinceSettleIndex: 0,
		},

		// If we specify a value well beyond the number of settled
		// invoices, we shouldn't get any invoices back.
		{
			sinceSettleIndex: 99999999,
		},

		// Using an index of 1 should result in the final 10 invoices
		// being returned, as we only settled those.
		{
			sinceSettleIndex: 1,
			resp:             invoices[1:],
		},
	}

	for i, query := range settleQueries {
		resp, err := db.InvoicesSettledSince(query.sinceSettleIndex)
		if err != nil {
			t.Fatalf("unable to query: %v", err)
		}

		if !reflect.DeepEqual(query.resp, resp) {
			t.Fatalf("test #%v: expected %v, got %v", i,
				spew.Sdump(query.resp), spew.Sdump(resp))
		}
	}
}

// Tests that FetchAllInvoicesWithPaymentHash returns all invoices with their
// corresponding payment hashes.
func TestFetchAllInvoicesWithPaymentHash(t *testing.T) {
	t.Parallel()

	db, cleanup, err := makeTestDB()
	defer cleanup()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}

	// With an empty DB we expect to return no error and an empty list.
	empty, err := db.FetchAllInvoicesWithPaymentHash(false)
	if err != nil {
		t.Fatalf("failed to call FetchAllInvoicesWithPaymentHash on empty DB: %v",
			err)
	}

	if len(empty) != 0 {
		t.Fatalf("expected empty list as a result, got: %v", empty)
	}

	// Now populate the DB and check if we can get all invoices with their
	// payment hashes as expected.
	const numInvoices = 20
	testPendingInvoices := make(map[lntypes.Hash]*Invoice)
	testAllInvoices := make(map[lntypes.Hash]*Invoice)

	states := []ContractState{
		ContractOpen, ContractSettled, ContractCanceled, ContractAccepted,
	}

	for i := lnwire.MilliSatoshi(1); i <= numInvoices; i++ {
		invoice, err := randInvoice(i)
		if err != nil {
			t.Fatalf("unable to create invoice: %v", err)
		}

		invoice.State = states[mrand.Intn(len(states))]
		paymentHash := invoice.Terms.PaymentPreimage.Hash()

		if invoice.State != ContractSettled && invoice.State != ContractCanceled {
			testPendingInvoices[paymentHash] = invoice
		}

		testAllInvoices[paymentHash] = invoice

		if _, err := db.AddInvoice(invoice, paymentHash); err != nil {
			t.Fatalf("unable to add invoice: %v", err)
		}
	}

	pendingInvoices, err := db.FetchAllInvoicesWithPaymentHash(true)
	if err != nil {
		t.Fatalf("can't fetch invoices with payment hash: %v", err)
	}

	if len(testPendingInvoices) != len(pendingInvoices) {
		t.Fatalf("expected %v pending invoices, got: %v",
			len(testPendingInvoices), len(pendingInvoices))
	}

	allInvoices, err := db.FetchAllInvoicesWithPaymentHash(false)
	if err != nil {
		t.Fatalf("can't fetch invoices with payment hash: %v", err)
	}

	if len(testAllInvoices) != len(allInvoices) {
		t.Fatalf("expected %v invoices, got: %v",
			len(testAllInvoices), len(allInvoices))
	}

	for i := range pendingInvoices {
		expected, ok := testPendingInvoices[pendingInvoices[i].PaymentHash]
		if !ok {
			t.Fatalf("coulnd't find invoice with hash: %v",
				pendingInvoices[i].PaymentHash)
		}

		// Zero out add index to not confuse DeepEqual.
		pendingInvoices[i].Invoice.AddIndex = 0
		expected.AddIndex = 0

		if !reflect.DeepEqual(*expected, pendingInvoices[i].Invoice) {
			t.Fatalf("expected: %v, got: %v",
				spew.Sdump(expected), spew.Sdump(pendingInvoices[i].Invoice))
		}
	}

	for i := range allInvoices {
		expected, ok := testAllInvoices[allInvoices[i].PaymentHash]
		if !ok {
			t.Fatalf("coulnd't find invoice with hash: %v",
				allInvoices[i].PaymentHash)
		}

		// Zero out add index to not confuse DeepEqual.
		allInvoices[i].Invoice.AddIndex = 0
		expected.AddIndex = 0

		if !reflect.DeepEqual(*expected, allInvoices[i].Invoice) {
			t.Fatalf("expected: %v, got: %v",
				spew.Sdump(expected), spew.Sdump(allInvoices[i].Invoice))
		}
	}

}

// TestDuplicateSettleInvoice tests that if we add a new invoice and settle it
// twice, then the second time we also receive the invoice that we settled as a
// return argument.
func TestDuplicateSettleInvoice(t *testing.T) {
	t.Parallel()

	db, cleanUp, err := makeTestDB()
	defer cleanUp()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}
	db.Now = func() time.Time { return time.Unix(1, 0) }

	// We'll start out by creating an invoice and writing it to the DB.
	amt := lnwire.NewMSatFromSatoshis(1000)
	invoice, err := randInvoice(amt)
	if err != nil {
		t.Fatalf("unable to create invoice: %v", err)
	}

	payHash := invoice.Terms.PaymentPreimage.Hash()

	if _, err := db.AddInvoice(invoice, payHash); err != nil {
		t.Fatalf("unable to add invoice %v", err)
	}

	// With the invoice in the DB, we'll now attempt to settle the invoice.
	dbInvoice, err := db.UpdateInvoice(
		payHash, getUpdateInvoice(amt),
	)
	if err != nil {
		t.Fatalf("unable to settle invoice: %v", err)
	}

	// We'll update what we expect the settle invoice to be so that our
	// comparison below has the correct assumption.
	invoice.SettleIndex = 1
	invoice.State = ContractSettled
	invoice.AmtPaid = amt
	invoice.SettleDate = dbInvoice.SettleDate
	invoice.Htlcs = map[CircuitKey]*InvoiceHTLC{
		{}: {
			Amt:           amt,
			AcceptTime:    time.Unix(1, 0),
			ResolveTime:   time.Unix(1, 0),
			State:         HtlcStateSettled,
			CustomRecords: make(record.CustomSet),
		},
	}

	// We should get back the exact same invoice that we just inserted.
	if !reflect.DeepEqual(dbInvoice, invoice) {
		t.Fatalf("wrong invoice after settle, expected %v got %v",
			spew.Sdump(invoice), spew.Sdump(dbInvoice))
	}

	// If we try to settle the invoice again, then we should get the very
	// same invoice back, but with an error this time.
	dbInvoice, err = db.UpdateInvoice(
		payHash, getUpdateInvoice(amt),
	)
	if err != ErrInvoiceAlreadySettled {
		t.Fatalf("expected ErrInvoiceAlreadySettled")
	}

	if dbInvoice == nil {
		t.Fatalf("invoice from db is nil after settle!")
	}

	invoice.SettleDate = dbInvoice.SettleDate
	if !reflect.DeepEqual(dbInvoice, invoice) {
		t.Fatalf("wrong invoice after second settle, expected %v got %v",
			spew.Sdump(invoice), spew.Sdump(dbInvoice))
	}
}

// TestQueryInvoices ensures that we can properly query the invoice database for
// invoices using different types of queries.
func TestQueryInvoices(t *testing.T) {
	t.Parallel()

	db, cleanUp, err := makeTestDB()
	defer cleanUp()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}

	// To begin the test, we'll add 50 invoices to the database. We'll
	// assume that the index of the invoice within the database is the same
	// as the amount of the invoice itself.
	const numInvoices = 50
	for i := lnwire.MilliSatoshi(1); i <= numInvoices; i++ {
		invoice, err := randInvoice(i)
		if err != nil {
			t.Fatalf("unable to create invoice: %v", err)
		}

		paymentHash := invoice.Terms.PaymentPreimage.Hash()

		if _, err := db.AddInvoice(invoice, paymentHash); err != nil {
			t.Fatalf("unable to add invoice: %v", err)
		}

		// We'll only settle half of all invoices created.
		if i%2 == 0 {
			_, err := db.UpdateInvoice(
				paymentHash, getUpdateInvoice(i),
			)
			if err != nil {
				t.Fatalf("unable to settle invoice: %v", err)
			}
		}
	}

	// We'll then retrieve the set of all invoices and pending invoices.
	// This will serve useful when comparing the expected responses of the
	// query with the actual ones.
	invoices, err := db.FetchAllInvoices(false)
	if err != nil {
		t.Fatalf("unable to retrieve invoices: %v", err)
	}
	pendingInvoices, err := db.FetchAllInvoices(true)
	if err != nil {
		t.Fatalf("unable to retrieve pending invoices: %v", err)
	}

	// The test will consist of several queries along with their respective
	// expected response. Each query response should match its expected one.
	testCases := []struct {
		query    InvoiceQuery
		expected []Invoice
	}{
		// Fetch all invoices with a single query.
		{
			query: InvoiceQuery{
				NumMaxInvoices: numInvoices,
			},
			expected: invoices,
		},
		// Fetch all invoices with a single query, reversed.
		{
			query: InvoiceQuery{
				Reversed:       true,
				NumMaxInvoices: numInvoices,
			},
			expected: invoices,
		},
		// Fetch the first 25 invoices.
		{
			query: InvoiceQuery{
				NumMaxInvoices: numInvoices / 2,
			},
			expected: invoices[:numInvoices/2],
		},
		// Fetch the first 10 invoices, but this time iterating
		// backwards.
		{
			query: InvoiceQuery{
				IndexOffset:    11,
				Reversed:       true,
				NumMaxInvoices: numInvoices,
			},
			expected: invoices[:10],
		},
		// Fetch the last 40 invoices.
		{
			query: InvoiceQuery{
				IndexOffset:    10,
				NumMaxInvoices: numInvoices,
			},
			expected: invoices[10:],
		},
		// Fetch all but the first invoice.
		{
			query: InvoiceQuery{
				IndexOffset:    1,
				NumMaxInvoices: numInvoices,
			},
			expected: invoices[1:],
		},
		// Fetch one invoice, reversed, with index offset 3. This
		// should give us the second invoice in the array.
		{
			query: InvoiceQuery{
				IndexOffset:    3,
				Reversed:       true,
				NumMaxInvoices: 1,
			},
			expected: invoices[1:2],
		},
		// Same as above, at index 2.
		{
			query: InvoiceQuery{
				IndexOffset:    2,
				Reversed:       true,
				NumMaxInvoices: 1,
			},
			expected: invoices[0:1],
		},
		// Fetch one invoice, at index 1, reversed. Since invoice#1 is
		// the very first, there won't be any left in a reverse search,
		// so we expect no invoices to be returned.
		{
			query: InvoiceQuery{
				IndexOffset:    1,
				Reversed:       true,
				NumMaxInvoices: 1,
			},
			expected: nil,
		},
		// Same as above, but don't restrict the number of invoices to
		// 1.
		{
			query: InvoiceQuery{
				IndexOffset:    1,
				Reversed:       true,
				NumMaxInvoices: numInvoices,
			},
			expected: nil,
		},
		// Fetch one invoice, reversed, with no offset set. We expect
		// the last invoice in the response.
		{
			query: InvoiceQuery{
				Reversed:       true,
				NumMaxInvoices: 1,
			},
			expected: invoices[numInvoices-1:],
		},
		// Fetch one invoice, reversed, the offset set at numInvoices+1.
		// We expect this to return the last invoice.
		{
			query: InvoiceQuery{
				IndexOffset:    numInvoices + 1,
				Reversed:       true,
				NumMaxInvoices: 1,
			},
			expected: invoices[numInvoices-1:],
		},
		// Same as above, at offset numInvoices.
		{
			query: InvoiceQuery{
				IndexOffset:    numInvoices,
				Reversed:       true,
				NumMaxInvoices: 1,
			},
			expected: invoices[numInvoices-2 : numInvoices-1],
		},
		// Fetch one invoice, at no offset (same as offset 0). We
		// expect the first invoice only in the response.
		{
			query: InvoiceQuery{
				NumMaxInvoices: 1,
			},
			expected: invoices[:1],
		},
		// Same as above, at offset 1.
		{
			query: InvoiceQuery{
				IndexOffset:    1,
				NumMaxInvoices: 1,
			},
			expected: invoices[1:2],
		},
		// Same as above, at offset 2.
		{
			query: InvoiceQuery{
				IndexOffset:    2,
				NumMaxInvoices: 1,
			},
			expected: invoices[2:3],
		},
		// Same as above, at offset numInvoices-1. Expect the last
		// invoice to be returned.
		{
			query: InvoiceQuery{
				IndexOffset:    numInvoices - 1,
				NumMaxInvoices: 1,
			},
			expected: invoices[numInvoices-1:],
		},
		// Same as above, at offset numInvoices. No invoices should be
		// returned, as there are no invoices after this offset.
		{
			query: InvoiceQuery{
				IndexOffset:    numInvoices,
				NumMaxInvoices: 1,
			},
			expected: nil,
		},
		// Fetch all pending invoices with a single query.
		{
			query: InvoiceQuery{
				PendingOnly:    true,
				NumMaxInvoices: numInvoices,
			},
			expected: pendingInvoices,
		},
		// Fetch the first 12 pending invoices.
		{
			query: InvoiceQuery{
				PendingOnly:    true,
				NumMaxInvoices: numInvoices / 4,
			},
			expected: pendingInvoices[:len(pendingInvoices)/2],
		},
		// Fetch the first 5 pending invoices, but this time iterating
		// backwards.
		{
			query: InvoiceQuery{
				IndexOffset:    10,
				PendingOnly:    true,
				Reversed:       true,
				NumMaxInvoices: numInvoices,
			},
			// Since we seek to the invoice with index 10 and
			// iterate backwards, there should only be 5 pending
			// invoices before it as every other invoice within the
			// index is settled.
			expected: pendingInvoices[:5],
		},
		// Fetch the last 15 invoices.
		{
			query: InvoiceQuery{
				IndexOffset:    20,
				PendingOnly:    true,
				NumMaxInvoices: numInvoices,
			},
			// Since we seek to the invoice with index 20, there are
			// 30 invoices left. From these 30, only 15 of them are
			// still pending.
			expected: pendingInvoices[len(pendingInvoices)-15:],
		},
	}

	for i, testCase := range testCases {
		response, err := db.QueryInvoices(testCase.query)
		if err != nil {
			t.Fatalf("unable to query invoice database: %v", err)
		}

		if !reflect.DeepEqual(response.Invoices, testCase.expected) {
			t.Fatalf("test #%d: query returned incorrect set of "+
				"invoices: expcted %v, got %v", i,
				spew.Sdump(response.Invoices),
				spew.Sdump(testCase.expected))
		}
	}
}

// getUpdateInvoice returns an invoice update callback that, when called,
// settles the invoice with the given amount.
func getUpdateInvoice(amt lnwire.MilliSatoshi) InvoiceUpdateCallback {
	return func(invoice *Invoice) (*InvoiceUpdateDesc, error) {
		if invoice.State == ContractSettled {
			return nil, ErrInvoiceAlreadySettled
		}

		noRecords := make(record.CustomSet)

		update := &InvoiceUpdateDesc{
			State: &InvoiceStateUpdateDesc{
				Preimage: invoice.Terms.PaymentPreimage,
				NewState: ContractSettled,
			},
			AddHtlcs: map[CircuitKey]*HtlcAcceptDesc{
				{}: {
					Amt:           amt,
					CustomRecords: noRecords,
				},
			},
		}

		return update, nil
	}
}

// TestCustomRecords tests that custom records are properly recorded in the
// invoice database.
func TestCustomRecords(t *testing.T) {
	t.Parallel()

	db, cleanUp, err := makeTestDB()
	defer cleanUp()
	if err != nil {
		t.Fatalf("unable to make test db: %v", err)
	}

	testInvoice := &Invoice{
		Htlcs: map[CircuitKey]*InvoiceHTLC{},
	}
	testInvoice.Terms.Value = lnwire.NewMSatFromSatoshis(10000)
	testInvoice.Terms.Features = emptyFeatures

	var paymentHash lntypes.Hash
	if _, err := db.AddInvoice(testInvoice, paymentHash); err != nil {
		t.Fatalf("unable to find invoice: %v", err)
	}

	// Accept an htlc with custom records on this invoice.
	key := CircuitKey{ChanID: lnwire.NewShortChanIDFromInt(1), HtlcID: 4}

	records := record.CustomSet{
		100000: []byte{},
		100001: []byte{1, 2},
	}

	_, err = db.UpdateInvoice(paymentHash,
		func(invoice *Invoice) (*InvoiceUpdateDesc, error) {
			return &InvoiceUpdateDesc{
				AddHtlcs: map[CircuitKey]*HtlcAcceptDesc{
					key: {
						Amt:           500,
						CustomRecords: records,
					},
				},
			}, nil
		},
	)
	if err != nil {
		t.Fatalf("unable to add invoice htlc: %v", err)
	}

	// Retrieve the invoice from that database and verify that the custom
	// records are present.
	dbInvoice, err := db.LookupInvoice(paymentHash)
	if err != nil {
		t.Fatalf("unable to lookup invoice: %v", err)
	}

	if len(dbInvoice.Htlcs) != 1 {
		t.Fatalf("expected the htlc to be added")
	}
	if !reflect.DeepEqual(records, dbInvoice.Htlcs[key].CustomRecords) {
		t.Fatalf("invalid custom records")
	}
}