/*
 *
 * Copyright 2019 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package clusterresolver

import (
	"context"
	"fmt"
	"testing"
	"time"

	"github.com/google/go-cmp/cmp"
	"google.golang.org/grpc/balancer"
	"google.golang.org/grpc/connectivity"
	"google.golang.org/grpc/internal/grpctest"
	"google.golang.org/grpc/internal/testutils"
	"google.golang.org/grpc/resolver"
	"google.golang.org/grpc/xds/internal"
	"google.golang.org/grpc/xds/internal/testutils/fakeclient"
	"google.golang.org/grpc/xds/internal/xdsclient"
	"google.golang.org/grpc/xds/internal/xdsclient/xdsresource"

	_ "google.golang.org/grpc/xds/internal/xdsclient/controller/version/v2" // V2 client registration.
)

const (
	defaultTestTimeout      = 1 * time.Second
	defaultTestShortTimeout = 10 * time.Millisecond
	testEDSServcie          = "test-eds-service-name"
	testClusterName         = "test-cluster-name"
)

var (
	// A non-empty endpoints update which is expected to be accepted by the EDS
	// LB policy.
	defaultEndpointsUpdate = xdsresource.EndpointsUpdate{
		Localities: []xdsresource.Locality{
			{
				Endpoints: []xdsresource.Endpoint{{Address: "endpoint1"}},
				ID:        internal.LocalityID{Zone: "zone"},
				Priority:  1,
				Weight:    100,
			},
		},
	}
)

func init() {
	balancer.Register(bb{})
}

type s struct {
	grpctest.Tester

	cleanup func()
}

func (ss s) Teardown(t *testing.T) {
	xdsclient.ClearAllCountersForTesting()
	ss.Tester.Teardown(t)
	if ss.cleanup != nil {
		ss.cleanup()
	}
}

func Test(t *testing.T) {
	grpctest.RunSubTests(t, s{})
}

const testBalancerNameFooBar = "foo.bar"

func newNoopTestClientConn() *noopTestClientConn {
	return &noopTestClientConn{}
}

// noopTestClientConn is used in EDS balancer config update tests that only
// cover the config update handling, but not SubConn/load-balancing.
type noopTestClientConn struct {
	balancer.ClientConn
}

func (t *noopTestClientConn) NewSubConn([]resolver.Address, balancer.NewSubConnOptions) (balancer.SubConn, error) {
	return nil, nil
}

func (noopTestClientConn) Target() string { return testEDSServcie }

type scStateChange struct {
	sc    balancer.SubConn
	state balancer.SubConnState
}

type fakeChildBalancer struct {
	cc              balancer.ClientConn
	subConnState    *testutils.Channel
	clientConnState *testutils.Channel
	resolverError   *testutils.Channel
}

func (f *fakeChildBalancer) UpdateClientConnState(state balancer.ClientConnState) error {
	f.clientConnState.Send(state)
	return nil
}

func (f *fakeChildBalancer) ResolverError(err error) {
	f.resolverError.Send(err)
}

func (f *fakeChildBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
	f.subConnState.Send(&scStateChange{sc: sc, state: state})
}

func (f *fakeChildBalancer) Close() {}

func (f *fakeChildBalancer) ExitIdle() {}

func (f *fakeChildBalancer) waitForClientConnStateChange(ctx context.Context) error {
	_, err := f.clientConnState.Receive(ctx)
	if err != nil {
		return err
	}
	return nil
}

func (f *fakeChildBalancer) waitForResolverError(ctx context.Context) error {
	_, err := f.resolverError.Receive(ctx)
	if err != nil {
		return err
	}
	return nil
}

func (f *fakeChildBalancer) waitForSubConnStateChange(ctx context.Context, wantState *scStateChange) error {
	val, err := f.subConnState.Receive(ctx)
	if err != nil {
		return err
	}
	gotState := val.(*scStateChange)
	if !cmp.Equal(gotState, wantState, cmp.AllowUnexported(scStateChange{})) {
		return fmt.Errorf("got subconnStateChange %v, want %v", gotState, wantState)
	}
	return nil
}

func newFakeChildBalancer(cc balancer.ClientConn) balancer.Balancer {
	return &fakeChildBalancer{
		cc:              cc,
		subConnState:    testutils.NewChannelWithSize(10),
		clientConnState: testutils.NewChannelWithSize(10),
		resolverError:   testutils.NewChannelWithSize(10),
	}
}

type fakeSubConn struct{}

func (*fakeSubConn) UpdateAddresses([]resolver.Address) { panic("implement me") }
func (*fakeSubConn) Connect()                           { panic("implement me") }

// waitForNewChildLB makes sure that a new child LB is created by the top-level
// clusterResolverBalancer.
func waitForNewChildLB(ctx context.Context, ch *testutils.Channel) (*fakeChildBalancer, error) {
	val, err := ch.Receive(ctx)
	if err != nil {
		return nil, fmt.Errorf("error when waiting for a new edsLB: %v", err)
	}
	return val.(*fakeChildBalancer), nil
}

// setup overrides the functions which are used to create the xdsClient and the
// edsLB, creates fake version of them and makes them available on the provided
// channels. The returned cancel function should be called by the test for
// cleanup.
func setup(childLBCh *testutils.Channel) (*fakeclient.Client, func()) {
	xdsC := fakeclient.NewClientWithName(testBalancerNameFooBar)

	origNewChildBalancer := newChildBalancer
	newChildBalancer = func(_ balancer.Builder, cc balancer.ClientConn, _ balancer.BuildOptions) balancer.Balancer {
		childLB := newFakeChildBalancer(cc)
		defer func() { childLBCh.Send(childLB) }()
		return childLB
	}
	return xdsC, func() {
		newChildBalancer = origNewChildBalancer
		xdsC.Close()
	}
}

// TestSubConnStateChange verifies if the top-level clusterResolverBalancer passes on
// the subConnState to appropriate child balancer.
func (s) TestSubConnStateChange(t *testing.T) {
	edsLBCh := testutils.NewChannel()
	xdsC, cleanup := setup(edsLBCh)
	defer cleanup()

	builder := balancer.Get(Name)
	edsB := builder.Build(newNoopTestClientConn(), balancer.BuildOptions{})
	if edsB == nil {
		t.Fatalf("builder.Build(%s) failed and returned nil", Name)
	}
	defer edsB.Close()

	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS(testEDSServcie),
	}); err != nil {
		t.Fatalf("edsB.UpdateClientConnState() failed: %v", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
	defer cancel()
	if _, err := xdsC.WaitForWatchEDS(ctx); err != nil {
		t.Fatalf("xdsClient.WatchEndpoints failed with error: %v", err)
	}
	xdsC.InvokeWatchEDSCallback("", defaultEndpointsUpdate, nil)
	edsLB, err := waitForNewChildLB(ctx, edsLBCh)
	if err != nil {
		t.Fatal(err)
	}

	fsc := &fakeSubConn{}
	state := balancer.SubConnState{ConnectivityState: connectivity.Ready}
	edsB.UpdateSubConnState(fsc, state)
	if err := edsLB.waitForSubConnStateChange(ctx, &scStateChange{sc: fsc, state: state}); err != nil {
		t.Fatal(err)
	}
}

// TestErrorFromXDSClientUpdate verifies that an error from xdsClient update is
// handled correctly.
//
// If it's resource-not-found, watch will NOT be canceled, the EDS impl will
// receive an empty EDS update, and new RPCs will fail.
//
// If it's connection error, nothing will happen. This will need to change to
// handle fallback.
func (s) TestErrorFromXDSClientUpdate(t *testing.T) {
	edsLBCh := testutils.NewChannel()
	xdsC, cleanup := setup(edsLBCh)
	defer cleanup()

	builder := balancer.Get(Name)
	edsB := builder.Build(newNoopTestClientConn(), balancer.BuildOptions{})
	if edsB == nil {
		t.Fatalf("builder.Build(%s) failed and returned nil", Name)
	}
	defer edsB.Close()

	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
	defer cancel()
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS(testEDSServcie),
	}); err != nil {
		t.Fatal(err)
	}
	if _, err := xdsC.WaitForWatchEDS(ctx); err != nil {
		t.Fatalf("xdsClient.WatchEndpoints failed with error: %v", err)
	}
	xdsC.InvokeWatchEDSCallback("", xdsresource.EndpointsUpdate{}, nil)
	edsLB, err := waitForNewChildLB(ctx, edsLBCh)
	if err != nil {
		t.Fatal(err)
	}
	if err := edsLB.waitForClientConnStateChange(ctx); err != nil {
		t.Fatalf("EDS impl got unexpected update: %v", err)
	}

	connectionErr := xdsresource.NewErrorf(xdsresource.ErrorTypeConnection, "connection error")
	xdsC.InvokeWatchEDSCallback("", xdsresource.EndpointsUpdate{}, connectionErr)

	sCtx, sCancel := context.WithTimeout(context.Background(), defaultTestShortTimeout)
	defer sCancel()
	if _, err := xdsC.WaitForCancelEDSWatch(sCtx); err != context.DeadlineExceeded {
		t.Fatal("watch was canceled, want not canceled (timeout error)")
	}

	sCtx, sCancel = context.WithTimeout(context.Background(), defaultTestShortTimeout)
	defer sCancel()
	if err := edsLB.waitForClientConnStateChange(sCtx); err != context.DeadlineExceeded {
		t.Fatal(err)
	}
	if err := edsLB.waitForResolverError(ctx); err != nil {
		t.Fatalf("want resolver error, got %v", err)
	}

	resourceErr := xdsresource.NewErrorf(xdsresource.ErrorTypeResourceNotFound, "clusterResolverBalancer resource not found error")
	xdsC.InvokeWatchEDSCallback("", xdsresource.EndpointsUpdate{}, resourceErr)
	// Even if error is resource not found, watch shouldn't be canceled, because
	// this is an EDS resource removed (and xds client actually never sends this
	// error, but we still handles it).
	sCtx, sCancel = context.WithTimeout(context.Background(), defaultTestShortTimeout)
	defer sCancel()
	if _, err := xdsC.WaitForCancelEDSWatch(sCtx); err != context.DeadlineExceeded {
		t.Fatal("watch was canceled, want not canceled (timeout error)")
	}
	if err := edsLB.waitForClientConnStateChange(sCtx); err != context.DeadlineExceeded {
		t.Fatal(err)
	}
	if err := edsLB.waitForResolverError(ctx); err != nil {
		t.Fatalf("want resolver error, got %v", err)
	}

	// An update with the same service name should not trigger a new watch.
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS(testEDSServcie),
	}); err != nil {
		t.Fatal(err)
	}
	sCtx, sCancel = context.WithTimeout(context.Background(), defaultTestShortTimeout)
	defer sCancel()
	if _, err := xdsC.WaitForWatchEDS(sCtx); err != context.DeadlineExceeded {
		t.Fatal("got unexpected new EDS watch")
	}
}

// TestErrorFromResolver verifies that resolver errors are handled correctly.
//
// If it's resource-not-found, watch will be canceled, the EDS impl will receive
// an empty EDS update, and new RPCs will fail.
//
// If it's connection error, nothing will happen. This will need to change to
// handle fallback.
func (s) TestErrorFromResolver(t *testing.T) {
	edsLBCh := testutils.NewChannel()
	xdsC, cleanup := setup(edsLBCh)
	defer cleanup()

	builder := balancer.Get(Name)
	edsB := builder.Build(newNoopTestClientConn(), balancer.BuildOptions{})
	if edsB == nil {
		t.Fatalf("builder.Build(%s) failed and returned nil", Name)
	}
	defer edsB.Close()

	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
	defer cancel()
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS(testEDSServcie),
	}); err != nil {
		t.Fatal(err)
	}

	if _, err := xdsC.WaitForWatchEDS(ctx); err != nil {
		t.Fatalf("xdsClient.WatchEndpoints failed with error: %v", err)
	}
	xdsC.InvokeWatchEDSCallback("", xdsresource.EndpointsUpdate{}, nil)
	edsLB, err := waitForNewChildLB(ctx, edsLBCh)
	if err != nil {
		t.Fatal(err)
	}
	if err := edsLB.waitForClientConnStateChange(ctx); err != nil {
		t.Fatalf("EDS impl got unexpected update: %v", err)
	}

	connectionErr := xdsresource.NewErrorf(xdsresource.ErrorTypeConnection, "connection error")
	edsB.ResolverError(connectionErr)

	sCtx, sCancel := context.WithTimeout(context.Background(), defaultTestShortTimeout)
	defer sCancel()
	if _, err := xdsC.WaitForCancelEDSWatch(sCtx); err != context.DeadlineExceeded {
		t.Fatal("watch was canceled, want not canceled (timeout error)")
	}

	sCtx, sCancel = context.WithTimeout(context.Background(), defaultTestShortTimeout)
	defer sCancel()
	if err := edsLB.waitForClientConnStateChange(sCtx); err != context.DeadlineExceeded {
		t.Fatal("eds impl got EDS resp, want timeout error")
	}
	if err := edsLB.waitForResolverError(ctx); err != nil {
		t.Fatalf("want resolver error, got %v", err)
	}

	resourceErr := xdsresource.NewErrorf(xdsresource.ErrorTypeResourceNotFound, "clusterResolverBalancer resource not found error")
	edsB.ResolverError(resourceErr)
	if _, err := xdsC.WaitForCancelEDSWatch(ctx); err != nil {
		t.Fatalf("want watch to be canceled, waitForCancel failed: %v", err)
	}
	if err := edsLB.waitForClientConnStateChange(sCtx); err != context.DeadlineExceeded {
		t.Fatal(err)
	}
	if err := edsLB.waitForResolverError(ctx); err != nil {
		t.Fatalf("want resolver error, got %v", err)
	}

	// An update with the same service name should trigger a new watch, because
	// the previous watch was canceled.
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS(testEDSServcie),
	}); err != nil {
		t.Fatal(err)
	}
	if _, err := xdsC.WaitForWatchEDS(ctx); err != nil {
		t.Fatalf("xdsClient.WatchEndpoints failed with error: %v", err)
	}
}

// Given a list of resource names, verifies that EDS requests for the same are
// sent by the EDS balancer, through the fake xDS client.
func verifyExpectedRequests(ctx context.Context, fc *fakeclient.Client, resourceNames ...string) error {
	for _, name := range resourceNames {
		if name == "" {
			// ResourceName empty string indicates a cancel.
			if _, err := fc.WaitForCancelEDSWatch(ctx); err != nil {
				return fmt.Errorf("timed out when expecting resource %q", name)
			}
			continue
		}

		resName, err := fc.WaitForWatchEDS(ctx)
		if err != nil {
			return fmt.Errorf("timed out when expecting resource %q, %p", name, fc)
		}
		if resName != name {
			return fmt.Errorf("got EDS request for resource %q, expected: %q", resName, name)
		}
	}
	return nil
}

// TestClientWatchEDS verifies that the xdsClient inside the top-level EDS LB
// policy registers an EDS watch for expected resource upon receiving an update
// from gRPC.
func (s) TestClientWatchEDS(t *testing.T) {
	edsLBCh := testutils.NewChannel()
	xdsC, cleanup := setup(edsLBCh)
	defer cleanup()

	builder := balancer.Get(Name)
	edsB := builder.Build(newNoopTestClientConn(), balancer.BuildOptions{})
	if edsB == nil {
		t.Fatalf("builder.Build(%s) failed and returned nil", Name)
	}
	defer edsB.Close()

	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
	defer cancel()
	// If eds service name is not set, should watch for cluster name.
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS("cluster-1"),
	}); err != nil {
		t.Fatal(err)
	}
	if err := verifyExpectedRequests(ctx, xdsC, "cluster-1"); err != nil {
		t.Fatal(err)
	}

	// Update with an non-empty edsServiceName should trigger an EDS watch for
	// the same.
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS("foobar-1"),
	}); err != nil {
		t.Fatal(err)
	}
	if err := verifyExpectedRequests(ctx, xdsC, "", "foobar-1"); err != nil {
		t.Fatal(err)
	}

	// Also test the case where the edsServerName changes from one non-empty
	// name to another, and make sure a new watch is registered. The previously
	// registered watch will be cancelled, which will result in an EDS request
	// with no resource names being sent to the server.
	if err := edsB.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  xdsclient.SetClient(resolver.State{}, xdsC),
		BalancerConfig: newLBConfigWithOneEDS("foobar-2"),
	}); err != nil {
		t.Fatal(err)
	}
	if err := verifyExpectedRequests(ctx, xdsC, "", "foobar-2"); err != nil {
		t.Fatal(err)
	}
}

func newLBConfigWithOneEDS(edsServiceName string) *LBConfig {
	return &LBConfig{
		DiscoveryMechanisms: []DiscoveryMechanism{{
			Cluster:        testClusterName,
			Type:           DiscoveryMechanismTypeEDS,
			EDSServiceName: edsServiceName,
		}},
	}
}
