package invoices

import (
	"sync"
	"testing"
	"time"

	"github.com/lightningnetwork/lnd/chainntnfs"
	"github.com/lightningnetwork/lnd/clock"
	"github.com/lightningnetwork/lnd/lntypes"
)

// invoiceExpiryWatcherTest holds a test fixture and implements checks
// for InvoiceExpiryWatcher tests.
type invoiceExpiryWatcherTest struct {
	t                *testing.T
	wg               sync.WaitGroup
	watcher          *InvoiceExpiryWatcher
	testData         invoiceExpiryTestData
	canceledInvoices []lntypes.Hash
}

type mockChainNotifier struct {
	chainntnfs.ChainNotifier

	blockChan chan *chainntnfs.BlockEpoch
}

func newMockNotifier() *mockChainNotifier {
	return &mockChainNotifier{
		blockChan: make(chan *chainntnfs.BlockEpoch),
	}
}

// RegisterBlockEpochNtfn mocks a block epoch notification, using the mock's
// block channel to deliver blocks to the client.
func (m *mockChainNotifier) RegisterBlockEpochNtfn(*chainntnfs.BlockEpoch) (
	*chainntnfs.BlockEpochEvent, error) {

	return &chainntnfs.BlockEpochEvent{
		Epochs: m.blockChan,
		Cancel: func() {},
	}, nil
}

// newInvoiceExpiryWatcherTest creates a new InvoiceExpiryWatcher test fixture
// and sets up the test environment.
func newInvoiceExpiryWatcherTest(t *testing.T, now time.Time,
	numExpiredInvoices, numPendingInvoices int) *invoiceExpiryWatcherTest {

	mockNotifier := newMockNotifier()
	test := &invoiceExpiryWatcherTest{
		watcher: NewInvoiceExpiryWatcher(
			clock.NewTestClock(testTime), 0,
			uint32(testCurrentHeight), nil, mockNotifier,
		),
		testData: generateInvoiceExpiryTestData(
			t, now, 0, numExpiredInvoices, numPendingInvoices,
		),
	}

	test.wg.Add(numExpiredInvoices)

	err := test.watcher.Start(func(paymentHash lntypes.Hash,
		force bool) error {

		test.canceledInvoices = append(
			test.canceledInvoices, paymentHash,
		)
		test.wg.Done()
		return nil
	})

	if err != nil {
		t.Fatalf("cannot start InvoiceExpiryWatcher: %v", err)
	}

	return test
}

func (t *invoiceExpiryWatcherTest) waitForFinish(timeout time.Duration) {
	done := make(chan struct{})

	// Wait for all cancels.
	go func() {
		t.wg.Wait()
		close(done)
	}()

	select {
	case <-done:
	case <-time.After(timeout):
		t.t.Fatalf("test timeout")
	}
}

func (t *invoiceExpiryWatcherTest) checkExpectations() {
	// Check that invoices that got canceled during the test are the ones
	// that expired.
	if len(t.canceledInvoices) != len(t.testData.expiredInvoices) {
		t.t.Fatalf("expected %v cancellations, got %v",
			len(t.testData.expiredInvoices),
			len(t.canceledInvoices))
	}

	for i := range t.canceledInvoices {
		if _, ok := t.testData.expiredInvoices[t.canceledInvoices[i]]; !ok {
			t.t.Fatalf("wrong invoice canceled")
		}
	}
}

// Tests that InvoiceExpiryWatcher can be started and stopped.
func TestInvoiceExpiryWatcherStartStop(t *testing.T) {
	watcher := NewInvoiceExpiryWatcher(
		clock.NewTestClock(testTime), 0, uint32(testCurrentHeight), nil,
		newMockNotifier(),
	)
	cancel := func(lntypes.Hash, bool) error {
		t.Fatalf("unexpected call")
		return nil
	}

	if err := watcher.Start(cancel); err != nil {
		t.Fatalf("unexpected error upon start: %v", err)
	}

	if err := watcher.Start(cancel); err == nil {
		t.Fatalf("expected error upon second start")
	}

	watcher.Stop()

	if err := watcher.Start(cancel); err != nil {
		t.Fatalf("unexpected error upon start: %v", err)
	}
}

// Tests that no invoices will expire from an empty InvoiceExpiryWatcher.
func TestInvoiceExpiryWithNoInvoices(t *testing.T) {
	t.Parallel()

	test := newInvoiceExpiryWatcherTest(t, testTime, 0, 0)

	test.waitForFinish(testTimeout)
	test.watcher.Stop()
	test.checkExpectations()
}

// Tests that if all add invoices are expired, then all invoices
// will be canceled.
func TestInvoiceExpiryWithOnlyExpiredInvoices(t *testing.T) {
	t.Parallel()

	test := newInvoiceExpiryWatcherTest(t, testTime, 0, 5)

	for paymentHash, invoice := range test.testData.pendingInvoices {
		test.watcher.AddInvoices(makeInvoiceExpiry(paymentHash, invoice))
	}

	test.waitForFinish(testTimeout)
	test.watcher.Stop()
	test.checkExpectations()
}

// Tests that if some invoices are expired, then those invoices
// will be canceled.
func TestInvoiceExpiryWithPendingAndExpiredInvoices(t *testing.T) {
	t.Parallel()

	test := newInvoiceExpiryWatcherTest(t, testTime, 5, 5)

	for paymentHash, invoice := range test.testData.expiredInvoices {
		test.watcher.AddInvoices(makeInvoiceExpiry(paymentHash, invoice))
	}

	for paymentHash, invoice := range test.testData.pendingInvoices {
		test.watcher.AddInvoices(makeInvoiceExpiry(paymentHash, invoice))
	}

	test.waitForFinish(testTimeout)
	test.watcher.Stop()
	test.checkExpectations()
}

// Tests adding multiple invoices at once.
func TestInvoiceExpiryWhenAddingMultipleInvoices(t *testing.T) {
	t.Parallel()

	test := newInvoiceExpiryWatcherTest(t, testTime, 5, 5)
	var invoices []invoiceExpiry

	for hash, invoice := range test.testData.expiredInvoices {
		invoices = append(invoices, makeInvoiceExpiry(hash, invoice))
	}

	for hash, invoice := range test.testData.pendingInvoices {
		invoices = append(invoices, makeInvoiceExpiry(hash, invoice))
	}

	test.watcher.AddInvoices(invoices...)
	test.waitForFinish(testTimeout)
	test.watcher.Stop()
	test.checkExpectations()
}