package routing

import (
	"crypto/rand"
	"crypto/sha256"
	"fmt"
	"io"
	"io/ioutil"
	"reflect"
	"testing"
	"time"

	"github.com/btcsuite/btcd/btcec"
	"github.com/davecgh/go-spew/spew"
	"github.com/lightningnetwork/lnd/channeldb"
	"github.com/lightningnetwork/lnd/lntypes"
	"github.com/lightningnetwork/lnd/routing/route"
)

var (
	priv, _ = btcec.NewPrivateKey(btcec.S256())
	pub     = priv.PubKey()

	testHop = &route.Hop{
		PubKeyBytes:      route.NewVertex(pub),
		ChannelID:        12345,
		OutgoingTimeLock: 111,
		AmtToForward:     555,
		LegacyPayload:    true,
	}

	testRoute = route.Route{
		TotalTimeLock: 123,
		TotalAmount:   1234567,
		SourcePubKey:  route.NewVertex(pub),
		Hops: []*route.Hop{
			testHop,
			testHop,
		},
	}

	testTimeout = 5 * time.Second
)

// TestControlTowerSubscribeUnknown tests that subscribing to an unknown
// payment fails.
func TestControlTowerSubscribeUnknown(t *testing.T) {
	t.Parallel()

	db, err := initDB()
	if err != nil {
		t.Fatalf("unable to init db: %v", err)
	}

	pControl := NewControlTower(channeldb.NewPaymentControl(db))

	// Subscription should fail when the payment is not known.
	_, err = pControl.SubscribePayment(lntypes.Hash{1})
	if err != channeldb.ErrPaymentNotInitiated {
		t.Fatal("expected subscribe to fail for unknown payment")
	}
}

// TestControlTowerSubscribeSuccess tests that payment updates for a
// successful payment are properly sent to subscribers.
func TestControlTowerSubscribeSuccess(t *testing.T) {
	t.Parallel()

	db, err := initDB()
	if err != nil {
		t.Fatalf("unable to init db: %v", err)
	}

	pControl := NewControlTower(channeldb.NewPaymentControl(db))

	// Initiate a payment.
	info, attempt, preimg, err := genInfo()
	if err != nil {
		t.Fatal(err)
	}

	err = pControl.InitPayment(info.PaymentHash, info)
	if err != nil {
		t.Fatal(err)
	}

	// Subscription should succeed and immediately report the InFlight
	// status.
	subscriber1, err := pControl.SubscribePayment(info.PaymentHash)
	if err != nil {
		t.Fatalf("expected subscribe to succeed, but got: %v", err)
	}

	// Register an attempt.
	err = pControl.RegisterAttempt(info.PaymentHash, attempt)
	if err != nil {
		t.Fatal(err)
	}

	// Register a second subscriber after the first attempt has started.
	subscriber2, err := pControl.SubscribePayment(info.PaymentHash)
	if err != nil {
		t.Fatalf("expected subscribe to succeed, but got: %v", err)
	}

	// Mark the payment as successful.
	err = pControl.SettleAttempt(
		info.PaymentHash, attempt.AttemptID,
		&channeldb.HTLCSettleInfo{
			Preimage: preimg,
		},
	)
	if err != nil {
		t.Fatal(err)
	}

	// Register a third subscriber after the payment succeeded.
	subscriber3, err := pControl.SubscribePayment(info.PaymentHash)
	if err != nil {
		t.Fatalf("expected subscribe to succeed, but got: %v", err)
	}

	// We expect all subscribers to now report the final outcome followed by
	// no other events.
	subscribers := []*ControlTowerSubscriber{
		subscriber1, subscriber2, subscriber3,
	}

	for _, s := range subscribers {
		var result *channeldb.MPPayment
		for result == nil || result.Status == channeldb.StatusInFlight {
			select {
			case item := <-s.Updates:
				result = item.(*channeldb.MPPayment)
			case <-time.After(testTimeout):
				t.Fatal("timeout waiting for payment result")
			}
		}

		if result.Status != channeldb.StatusSucceeded {
			t.Fatal("unexpected payment state")
		}
		settle, _ := result.TerminalInfo()
		if settle.Preimage != preimg {
			t.Fatal("unexpected preimage")
		}
		if len(result.HTLCs) != 1 {
			t.Fatalf("expected one htlc, got %d", len(result.HTLCs))
		}
		htlc := result.HTLCs[0]
		if !reflect.DeepEqual(htlc.Route, attempt.Route) {
			t.Fatalf("unexpected htlc route: %v vs %v",
				spew.Sdump(htlc.Route),
				spew.Sdump(attempt.Route))
		}

		// After the final event, we expect the channel to be closed.
		select {
		case _, ok := <-s.Updates:
			if ok {
				t.Fatal("expected channel to be closed")
			}
		case <-time.After(testTimeout):
			t.Fatal("timeout waiting for result channel close")
		}
	}
}

// TestPaymentControlSubscribeFail tests that payment updates for a
// failed payment are properly sent to subscribers.
func TestPaymentControlSubscribeFail(t *testing.T) {
	t.Parallel()

	t.Run("register attempt", func(t *testing.T) {
		testPaymentControlSubscribeFail(t, true)
	})
	t.Run("no register attempt", func(t *testing.T) {
		testPaymentControlSubscribeFail(t, false)
	})
}

func testPaymentControlSubscribeFail(t *testing.T, registerAttempt bool) {
	db, err := initDB()
	if err != nil {
		t.Fatalf("unable to init db: %v", err)
	}

	pControl := NewControlTower(channeldb.NewPaymentControl(db))

	// Initiate a payment.
	info, attempt, _, err := genInfo()
	if err != nil {
		t.Fatal(err)
	}

	err = pControl.InitPayment(info.PaymentHash, info)
	if err != nil {
		t.Fatal(err)
	}

	// Subscription should succeed.
	subscriber1, err := pControl.SubscribePayment(info.PaymentHash)
	if err != nil {
		t.Fatalf("expected subscribe to succeed, but got: %v", err)
	}

	// Conditionally register the attempt based on the test type. This
	// allows us to simulate failing after attempting with an htlc or before
	// making any attempts at all.
	if registerAttempt {
		// Register an attempt.
		err = pControl.RegisterAttempt(info.PaymentHash, attempt)
		if err != nil {
			t.Fatal(err)
		}

		// Fail the payment attempt.
		err := pControl.FailAttempt(
			info.PaymentHash, attempt.AttemptID,
			&channeldb.HTLCFailInfo{},
		)
		if err != nil {
			t.Fatalf("unable to fail htlc: %v", err)
		}
	}

	// Mark the payment as failed.
	if err := pControl.Fail(info.PaymentHash, channeldb.FailureReasonTimeout); err != nil {
		t.Fatal(err)
	}

	// Register a second subscriber after the payment failed.
	subscriber2, err := pControl.SubscribePayment(info.PaymentHash)
	if err != nil {
		t.Fatalf("expected subscribe to succeed, but got: %v", err)
	}

	// We expect all subscribers to now report the final outcome followed by
	// no other events.
	subscribers := []*ControlTowerSubscriber{
		subscriber1, subscriber2,
	}

	for _, s := range subscribers {
		var result *channeldb.MPPayment
		for result == nil || result.Status == channeldb.StatusInFlight {
			select {
			case item := <-s.Updates:
				result = item.(*channeldb.MPPayment)
			case <-time.After(testTimeout):
				t.Fatal("timeout waiting for payment result")
			}
		}

		if result.Status == channeldb.StatusSucceeded {
			t.Fatal("unexpected payment state")
		}

		// There will either be one or zero htlcs depending on whether
		// or not the attempt was registered. Assert the correct number
		// is present, and the route taken if the attempt was
		// registered.
		if registerAttempt {
			if len(result.HTLCs) != 1 {
				t.Fatalf("expected 1 htlc, got: %d",
					len(result.HTLCs))
			}

			htlc := result.HTLCs[0]
			if !reflect.DeepEqual(htlc.Route, testRoute) {
				t.Fatalf("unexpected htlc route: %v vs %v",
					spew.Sdump(htlc.Route),
					spew.Sdump(testRoute))
			}
		} else if len(result.HTLCs) != 0 {
			t.Fatalf("expected 0 htlcs, got: %d",
				len(result.HTLCs))
		}

		if *result.FailureReason != channeldb.FailureReasonTimeout {
			t.Fatal("unexpected failure reason")
		}

		// After the final event, we expect the channel to be closed.
		select {
		case _, ok := <-s.Updates:
			if ok {
				t.Fatal("expected channel to be closed")
			}
		case <-time.After(testTimeout):
			t.Fatal("timeout waiting for result channel close")
		}
	}
}

func initDB() (*channeldb.DB, error) {
	tempPath, err := ioutil.TempDir("", "routingdb")
	if err != nil {
		return nil, err
	}

	db, err := channeldb.Open(tempPath)
	if err != nil {
		return nil, err
	}

	return db, err
}

func genInfo() (*channeldb.PaymentCreationInfo, *channeldb.HTLCAttemptInfo,
	lntypes.Preimage, error) {

	preimage, err := genPreimage()
	if err != nil {
		return nil, nil, preimage, fmt.Errorf("unable to "+
			"generate preimage: %v", err)
	}

	rhash := sha256.Sum256(preimage[:])
	return &channeldb.PaymentCreationInfo{
			PaymentHash:    rhash,
			Value:          testRoute.ReceiverAmt(),
			CreationTime:   time.Unix(time.Now().Unix(), 0),
			PaymentRequest: []byte("hola"),
		},
		&channeldb.HTLCAttemptInfo{
			AttemptID:  1,
			SessionKey: priv,
			Route:      testRoute,
		}, preimage, nil
}

func genPreimage() ([32]byte, error) {
	var preimage [32]byte
	if _, err := io.ReadFull(rand.Reader, preimage[:]); err != nil {
		return preimage, err
	}
	return preimage, nil
}