// 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 ...cloud.ClientOption) (*Client, error) {
	httpClient, endpoint, err := transport.NewHTTPClient(ctx, append([]cloud.ClientOption{
		cloud.WithEndpoint(prodAddr),
		cloud.WithScopes(Scope),
		cloud.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
}

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

}

// NewClusterAdminClient creates a new ClusterAdminClient for a given project.
func NewClusterAdminClient(ctx context.Context, project string, opts ...cloud.ClientOption) (*ClusterAdminClient, error) {
	o := []cloud.ClientOption{
		cloud.WithEndpoint(clusterAdminAddr),
		cloud.WithScopes(ClusterAdminScope),
		cloud.WithUserAgent(clientUserAgent),
	}
	o = append(o, opts...)
	conn, err := transport.DialGRPC(ctx, o...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}
	return &ClusterAdminClient{
		conn:    conn,
		cClient: btcspb.NewBigtableClusterServiceClient(conn),

		project: project,
	}, nil
}

// DefaultClientOptions returns the default client options to use for the
// client's gRPC connection.
func DefaultClientOptions(endpoint, scope, userAgent string) ([]cloud.ClientOption, error) {
	var o []cloud.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 = []cloud.ClientOption{cloud.WithBaseGRPC(conn)}
	} else {
		o = []cloud.ClientOption{
			cloud.WithEndpoint(endpoint),
			cloud.WithScopes(scope),
			cloud.WithUserAgent(userAgent),
		}
	}
	return o, nil
}

// NewClient creates a new Google Cloud Storage client.
// The default scope is ScopeFullControl. To use a different scope, like ScopeReadOnly, use cloud.WithScopes.
func NewClient(ctx context.Context, opts ...cloud.ClientOption) (*Client, error) {
	o := []cloud.ClientOption{
		cloud.WithScopes(ScopeFullControl),
		cloud.WithUserAgent(userAgent),
	}
	opts = append(o, opts...)
	hc, _, err := transport.NewHTTPClient(ctx, opts...)
	if err != nil {
		return nil, fmt.Errorf("dialing: %v", err)
	}
	rawService, err := raw.New(hc)
	if err != nil {
		return nil, fmt.Errorf("storage client: %v", err)
	}
	return &Client{
		hc:  hc,
		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 ...cloud.ClientOption) (*Client, error) {
	var o []cloud.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 = []cloud.ClientOption{cloud.WithBaseGRPC(conn)}
	} else {
		o = []cloud.ClientOption{
			cloud.WithEndpoint(prodAddr),
			cloud.WithScopes(ScopeDatastore),
			cloud.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:  pb.NewDatastoreClient(conn),
		dataset: projectID,
	}, nil

}

// NewClient create a new PubSub client.
func NewClient(ctx context.Context, projectID string, opts ...cloud.ClientOption) (*Client, error) {
	o := []cloud.ClientOption{
		cloud.WithEndpoint(prodAddr),
		cloud.WithScopes(raw.PubsubScope, raw.CloudPlatformScope),
		cloud.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)

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

	return c, 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 ...cloud.ClientOption) (*Client, error) {
	o := []cloud.ClientOption{
		cloud.WithEndpoint(prodAddr),
		cloud.WithScopes(Scope),
		cloud.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
}

// NewClient creates a new Google Stackdriver Trace client.
func NewClient(ctx context.Context, projectID string, opts ...cloud.ClientOption) (*Client, error) {
	o := []cloud.ClientOption{
		cloud.WithScopes(cloudPlatformScope),
		cloud.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
}