// NewClient creates a new PubSub client.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	var o []option.ClientOption
	// Environment variables for gcloud emulator:
	// https://option.google.com/sdk/gcloud/reference/beta/emulators/pubsub/
	if addr := os.Getenv("PUBSUB_EMULATOR_HOST"); addr != "" {
		o = []option.ClientOption{
			option.WithEndpoint("http://" + addr + "/"),
			option.WithHTTPClient(http.DefaultClient),
		}
	} else {
		o = []option.ClientOption{
			option.WithEndpoint(prodAddr),
			option.WithScopes(raw.PubsubScope, raw.CloudPlatformScope),
			option.WithUserAgent(userAgent),
		}
	}
	o = append(o, opts...)
	httpClient, endpoint, err := transport.NewHTTPClient(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}

	s, err := newPubSubService(httpClient, endpoint)
	if err != nil {
		return nil, fmt.Errorf("constructing pubsub client: %v", err)
	}

	c := &Client{
		projectID: projectID,
		s:         s,
	}

	return c, nil
}

// NewClient creates a new Google Container Engine client.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	o := []option.ClientOption{
		option.WithEndpoint(prodAddr),
		option.WithScopes(raw.CloudPlatformScope),
		option.WithUserAgent(userAgent),
	}
	o = append(o, opts...)
	httpClient, endpoint, err := transport.NewHTTPClient(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}

	svc, err := raw.New(httpClient)
	if err != nil {
		return nil, fmt.Errorf("constructing container client: %v", err)
	}
	svc.BasePath = endpoint

	c := &Client{
		projectID: projectID,
		svc:       svc,
	}

	return c, nil
}

// NewClient returns a new log client, logging to the named log in the
// provided project.
//
// The exported fields on the returned client may be modified before
// the client is used for logging. Once log entries are in flight,
// the fields must not be modified.
func NewClient(ctx context.Context, projectID, logName string, opts ...option.ClientOption) (*Client, error) {
	httpClient, endpoint, err := transport.NewHTTPClient(ctx, append([]option.ClientOption{
		option.WithEndpoint(prodAddr),
		option.WithScopes(Scope),
		option.WithUserAgent(userAgent),
	}, opts...)...)
	if err != nil {
		return nil, err
	}
	svc, err := api.New(httpClient)
	if err != nil {
		return nil, err
	}
	svc.BasePath = endpoint
	c := &Client{
		svc:     svc,
		logs:    api.NewProjectsLogsEntriesService(svc),
		logName: logName,
		projID:  projectID,
	}
	for i := range c.writer {
		level := Level(i)
		c.writer[level] = levelWriter{level, c}
		c.logger[level] = log.New(c.writer[level], "", 0)
	}
	return c, nil
}

func defaultClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("speech.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
		),
	}
}

func defaultImageAnnotatorClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("vision.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
		),
	}
}

func defaultReportErrorsClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("clouderrorreporting.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
		),
	}
}

func defaultController2ClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("clouddebugger.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
			"https://www.googleapis.com/auth/cloud_debugger",
		),
	}
}

func defaultSubscriberClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("pubsub.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
			"https://www.googleapis.com/auth/pubsub",
		),
	}
}

func defaultClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("cloudtrace.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
			"https://www.googleapis.com/auth/trace.append",
			"https://www.googleapis.com/auth/trace.readonly",
		),
	}
}

func defaultMetricClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("monitoring.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
			"https://www.googleapis.com/auth/monitoring",
			"https://www.googleapis.com/auth/monitoring.read",
			"https://www.googleapis.com/auth/monitoring.write",
		),
	}
}

func defaultClientOptions() []option.ClientOption {
	return []option.ClientOption{
		option.WithEndpoint("logging.googleapis.com:443"),
		option.WithScopes(
			"https://www.googleapis.com/auth/cloud-platform",
			"https://www.googleapis.com/auth/cloud-platform.read-only",
			"https://www.googleapis.com/auth/logging.admin",
			"https://www.googleapis.com/auth/logging.read",
			"https://www.googleapis.com/auth/logging.write",
		),
	}
}

// NewClient returns a new logging client associated with the provided project ID.
//
// By default NewClient uses WriteScope. To use a different scope, call
// NewClient using a WithScopes option.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	// Check for '/' in project ID to reserve the ability to support various owning resources,
	// in the form "{Collection}/{Name}", for instance "organizations/my-org".
	if strings.ContainsRune(projectID, '/') {
		return nil, errors.New("logging: project ID contains '/'")
	}
	opts = append([]option.ClientOption{option.WithEndpoint(prodAddr), option.WithScopes(WriteScope)},
		opts...)
	lc, err := vkit.NewClient(ctx, opts...)
	if err != nil {
		return nil, err
	}
	// TODO(jba): pass along any client options that should be provided to all clients.
	sc, err := vkit.NewConfigClient(ctx, option.WithGRPCConn(lc.Connection()))
	if err != nil {
		return nil, err
	}
	mc, err := vkit.NewMetricsClient(ctx, option.WithGRPCConn(lc.Connection()))
	if err != nil {
		return nil, err
	}
	lc.SetGoogleClientInfo("logging", version)
	sc.SetGoogleClientInfo("logging", version)
	mc.SetGoogleClientInfo("logging", version)
	client := &Client{
		lClient:   lc,
		sClient:   sc,
		mClient:   mc,
		projectID: projectID,
		errc:      make(chan error, defaultErrorCapacity), // create a small buffer for errors
		donec:     make(chan struct{}),
		OnError:   func(e error) { log.Printf("logging client: %v", e) },
	}
	// Call the user's function synchronously, to make life easier for them.
	go func() {
		for err := range client.errc {
			// This reference to OnError is memory-safe if the user sets OnError before
			// calling any client methods. The reference happens before the first read from
			// client.errc, which happens before the first write to client.errc, which
			// happens before any call, which happens before the user sets OnError.
			if fn := client.OnError; fn != nil {
				fn(err)
			} else {
				log.Printf("logging (project ID %q): %v", projectID, err)
			}
		}
	}()
	return client, nil
}

// NewClient constructs a new Client that can perform Translate operations.
//
// You can find or create API key for your project from the Credentials page of
// the Developers Console (console.developers.google.com).
func NewClient(ctx context.Context, opts ...option.ClientOption) (*Client, error) {
	o := []option.ClientOption{
		option.WithEndpoint(prodAddr),
		option.WithScopes(Scope),
		option.WithUserAgent(userAgent),
	}
	o = append(o, opts...)
	httpClient, endpoint, err := transport.NewHTTPClient(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}
	rawService, err := raw.New(httpClient)
	if err != nil {
		return nil, fmt.Errorf("translate client: %v", err)
	}
	rawService.BasePath = endpoint
	return &Client{raw: rawService}, nil
}

// NewClient creates a new Client for a given dataset.
// If the project ID is empty, it is derived from the DATASTORE_PROJECT_ID environment variable.
// If the DATASTORE_EMULATOR_HOST environment variable is set, client will use its value
// to connect to a locally-running datastore emulator.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	var o []option.ClientOption
	// Environment variables for gcd emulator:
	// https://cloud.google.com/datastore/docs/tools/datastore-emulator
	// If the emulator is available, dial it directly (and don't pass any credentials).
	if addr := os.Getenv("DATASTORE_EMULATOR_HOST"); addr != "" {
		conn, err := grpc.Dial(addr, grpc.WithInsecure())
		if err != nil {
			return nil, fmt.Errorf("grpc.Dial: %v", err)
		}
		o = []option.ClientOption{option.WithGRPCConn(conn)}
	} else {
		o = []option.ClientOption{
			option.WithEndpoint(prodAddr),
			option.WithScopes(ScopeDatastore),
			option.WithUserAgent(userAgent),
		}
	}
	// Warn if we see the legacy emulator environment variables.
	if os.Getenv("DATASTORE_HOST") != "" && os.Getenv("DATASTORE_EMULATOR_HOST") == "" {
		log.Print("WARNING: legacy environment variable DATASTORE_HOST is ignored. Use DATASTORE_EMULATOR_HOST instead.")
	}
	if os.Getenv("DATASTORE_DATASET") != "" && os.Getenv("DATASTORE_PROJECT_ID") == "" {
		log.Print("WARNING: legacy environment variable DATASTORE_DATASET is ignored. Use DATASTORE_PROJECT_ID instead.")
	}
	if projectID == "" {
		projectID = os.Getenv("DATASTORE_PROJECT_ID")
	}
	if projectID == "" {
		return nil, errors.New("datastore: missing project/dataset id")
	}
	o = append(o, opts...)
	conn, err := transport.DialGRPC(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}
	return &Client{
		conn:    conn,
		client:  newDatastoreClient(conn, projectID),
		dataset: projectID,
	}, nil

}

// DefaultClientOptions returns the default client options to use for the
// client's gRPC connection.
func DefaultClientOptions(endpoint, scope, userAgent string) ([]option.ClientOption, error) {
	var o []option.ClientOption
	// Check the environment variables for the bigtable emulator.
	// Dial it directly and don't pass any credentials.
	if addr := os.Getenv("BIGTABLE_EMULATOR_HOST"); addr != "" {
		conn, err := grpc.Dial(addr, grpc.WithInsecure())
		if err != nil {
			return nil, fmt.Errorf("emulator grpc.Dial: %v", err)
		}
		o = []option.ClientOption{option.WithGRPCConn(conn)}
	} else {
		o = []option.ClientOption{
			option.WithEndpoint(endpoint),
			option.WithScopes(scope),
			option.WithUserAgent(userAgent),
		}
	}
	return o, nil
}

// NewClient creates a new Google Stackdriver Trace client.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	o := []option.ClientOption{
		option.WithScopes(cloudPlatformScope),
		option.WithUserAgent(userAgent),
	}
	o = append(o, opts...)
	hc, basePath, err := transport.NewHTTPClient(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("creating HTTP client for Google Stackdriver Trace API: %v", err)
	}
	apiService, err := api.New(hc)
	if err != nil {
		return nil, fmt.Errorf("creating Google Stackdriver Trace API client: %v", err)
	}
	if basePath != "" {
		// An option set a basepath, so override api.New's default.
		apiService.BasePath = basePath
	}
	c := &Client{
		service:   apiService,
		projectID: projectID,
	}
	bundler := bundler.NewBundler((*api.Trace)(nil), func(bundle interface{}) {
		traces := bundle.([]*api.Trace)
		err := c.upload(traces)
		if err != nil {
			log.Printf("failed to upload %d traces to the Cloud Trace server.", len(traces))
		}
	})
	bundler.DelayThreshold = 2 * time.Second
	bundler.BundleCountThreshold = 100
	// We're not measuring bytes here, we're counting traces and spans as one "byte" each.
	bundler.BundleByteThreshold = 1000
	bundler.BundleByteLimit = 1000
	bundler.BufferedByteLimit = 10000
	c.bundler = bundler
	return c, nil
}

// NewClient creates a new Google Stackdriver Trace client.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	o := []option.ClientOption{
		option.WithScopes(cloudPlatformScope),
		option.WithUserAgent(userAgent),
	}
	o = append(o, opts...)
	hc, basePath, err := transport.NewHTTPClient(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("creating HTTP client for Google Stackdriver Trace API: %v", err)
	}
	apiService, err := api.New(hc)
	if err != nil {
		return nil, fmt.Errorf("creating Google Stackdriver Trace API client: %v", err)
	}
	if basePath != "" {
		// An option set a basepath, so override api.New's default.
		apiService.BasePath = basePath
	}
	return &Client{
		service:   apiService,
		projectID: projectID,
	}, nil
}

// NewClient constructs a new Client which can perform BigQuery operations.
// Operations performed via the client are billed to the specified GCP project.
func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (*Client, error) {
	o := []option.ClientOption{
		option.WithEndpoint(prodAddr),
		option.WithScopes(Scope),
		option.WithUserAgent(userAgent),
	}
	o = append(o, opts...)
	httpClient, endpoint, err := transport.NewHTTPClient(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}

	s, err := newBigqueryService(httpClient, endpoint)
	if err != nil {
		return nil, fmt.Errorf("constructing bigquery client: %v", err)
	}

	c := &Client{
		service:   s,
		projectID: projectID,
	}
	return c, nil
}

	ProjectID          string              // GCP Project ID.
	AppModule          string              // Module name for the debugged program.
	AppVersion         string              // Version number for this module.
	SourceContexts     []*cd.SourceContext // Description of source.
	Verbose            bool
	ServiceAccountFile string // File containing service account credentials.
}

type serviceInterface interface {
	Register(req *cd.RegisterDebuggeeRequest) (*cd.RegisterDebuggeeResponse, error)
	Update(debuggeeID, breakpointID string, req *cd.UpdateActiveBreakpointRequest) (*cd.UpdateActiveBreakpointResponse, error)
	List(debuggeeID, waitToken string) (*cd.ListActiveBreakpointsResponse, error)
}

var newService = func(serviceAccountFile string) (serviceInterface, error) {
	opts := []option.ClientOption{option.WithScopes(cd.CloudDebuggerScope)}
	if serviceAccountFile != "" {
		opts = append(opts, option.WithServiceAccountFile(serviceAccountFile))
	}
	httpClient, endpoint, err := transport.NewHTTPClient(context.Background(), opts...)
	if err != nil {
		return nil, err
	}
	s, err := cd.New(httpClient)
	if err != nil {
		return nil, err
	}
	if endpoint != "" {
		s.BasePath = endpoint
	}
	return &service{s: s}, nil

// WithScopes returns a ClientOption that overrides the default OAuth2 scopes
// to be used for a service.
func WithScopes(scope ...string) ClientOption {
	return wrapOpt{option.WithScopes(scope...)}
}