// Copyright 2021 Google LLC
//
// 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
//
//     https://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.

// Code generated by protoc-gen-go_gapic. DO NOT EDIT.

package pubsub

import (
	"context"
	"fmt"
	"math"
	"net/url"
	"time"

	gax "github.com/googleapis/gax-go/v2"
	"google.golang.org/api/iterator"
	"google.golang.org/api/option"
	"google.golang.org/api/option/internaloption"
	gtransport "google.golang.org/api/transport/grpc"
	iampb "google.golang.org/genproto/googleapis/iam/v1"
	pubsubpb "google.golang.org/genproto/googleapis/pubsub/v1"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/protobuf/proto"
)

var newSubscriberClientHook clientHook

// SubscriberCallOptions contains the retry settings for each method of SubscriberClient.
type SubscriberCallOptions struct {
	CreateSubscription []gax.CallOption
	GetSubscription    []gax.CallOption
	UpdateSubscription []gax.CallOption
	ListSubscriptions  []gax.CallOption
	DeleteSubscription []gax.CallOption
	ModifyAckDeadline  []gax.CallOption
	Acknowledge        []gax.CallOption
	Pull               []gax.CallOption
	StreamingPull      []gax.CallOption
	ModifyPushConfig   []gax.CallOption
	GetSnapshot        []gax.CallOption
	ListSnapshots      []gax.CallOption
	CreateSnapshot     []gax.CallOption
	UpdateSnapshot     []gax.CallOption
	DeleteSnapshot     []gax.CallOption
	Seek               []gax.CallOption
	GetIamPolicy       []gax.CallOption
	SetIamPolicy       []gax.CallOption
	TestIamPermissions []gax.CallOption
}

func defaultSubscriberGRPCClientOptions() []option.ClientOption {
	return []option.ClientOption{
		internaloption.WithDefaultEndpoint("pubsub.googleapis.com:443"),
		internaloption.WithDefaultMTLSEndpoint("pubsub.mtls.googleapis.com:443"),
		internaloption.WithDefaultAudience("https://pubsub.googleapis.com/"),
		internaloption.WithDefaultScopes(DefaultAuthScopes()...),
		internaloption.EnableJwtWithScope(),
		option.WithGRPCDialOption(grpc.WithDisableServiceConfig()),
		option.WithGRPCDialOption(grpc.WithDefaultCallOptions(
			grpc.MaxCallRecvMsgSize(math.MaxInt32))),
	}
}

func defaultSubscriberCallOptions() *SubscriberCallOptions {
	return &SubscriberCallOptions{
		CreateSubscription: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		GetSubscription: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		UpdateSubscription: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		ListSubscriptions: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		DeleteSubscription: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		ModifyAckDeadline: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		Acknowledge: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		Pull: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		StreamingPull: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.DeadlineExceeded,
					codes.ResourceExhausted,
					codes.Aborted,
					codes.Internal,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		ModifyPushConfig: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		GetSnapshot: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		ListSnapshots: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		CreateSnapshot: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		UpdateSnapshot: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		DeleteSnapshot: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		Seek: []gax.CallOption{
			gax.WithRetry(func() gax.Retryer {
				return gax.OnCodes([]codes.Code{
					codes.Unknown,
					codes.Aborted,
					codes.Unavailable,
				}, gax.Backoff{
					Initial:    100 * time.Millisecond,
					Max:        60000 * time.Millisecond,
					Multiplier: 1.30,
				})
			}),
		},
		GetIamPolicy:       []gax.CallOption{},
		SetIamPolicy:       []gax.CallOption{},
		TestIamPermissions: []gax.CallOption{},
	}
}

// internalSubscriberClient is an interface that defines the methods availaible from Cloud Pub/Sub API.
type internalSubscriberClient interface {
	Close() error
	setGoogleClientInfo(...string)
	Connection() *grpc.ClientConn
	CreateSubscription(context.Context, *pubsubpb.Subscription, ...gax.CallOption) (*pubsubpb.Subscription, error)
	GetSubscription(context.Context, *pubsubpb.GetSubscriptionRequest, ...gax.CallOption) (*pubsubpb.Subscription, error)
	UpdateSubscription(context.Context, *pubsubpb.UpdateSubscriptionRequest, ...gax.CallOption) (*pubsubpb.Subscription, error)
	ListSubscriptions(context.Context, *pubsubpb.ListSubscriptionsRequest, ...gax.CallOption) *SubscriptionIterator
	DeleteSubscription(context.Context, *pubsubpb.DeleteSubscriptionRequest, ...gax.CallOption) error
	ModifyAckDeadline(context.Context, *pubsubpb.ModifyAckDeadlineRequest, ...gax.CallOption) error
	Acknowledge(context.Context, *pubsubpb.AcknowledgeRequest, ...gax.CallOption) error
	Pull(context.Context, *pubsubpb.PullRequest, ...gax.CallOption) (*pubsubpb.PullResponse, error)
	StreamingPull(context.Context, ...gax.CallOption) (pubsubpb.Subscriber_StreamingPullClient, error)
	ModifyPushConfig(context.Context, *pubsubpb.ModifyPushConfigRequest, ...gax.CallOption) error
	GetSnapshot(context.Context, *pubsubpb.GetSnapshotRequest, ...gax.CallOption) (*pubsubpb.Snapshot, error)
	ListSnapshots(context.Context, *pubsubpb.ListSnapshotsRequest, ...gax.CallOption) *SnapshotIterator
	CreateSnapshot(context.Context, *pubsubpb.CreateSnapshotRequest, ...gax.CallOption) (*pubsubpb.Snapshot, error)
	UpdateSnapshot(context.Context, *pubsubpb.UpdateSnapshotRequest, ...gax.CallOption) (*pubsubpb.Snapshot, error)
	DeleteSnapshot(context.Context, *pubsubpb.DeleteSnapshotRequest, ...gax.CallOption) error
	Seek(context.Context, *pubsubpb.SeekRequest, ...gax.CallOption) (*pubsubpb.SeekResponse, error)
	GetIamPolicy(context.Context, *iampb.GetIamPolicyRequest, ...gax.CallOption) (*iampb.Policy, error)
	SetIamPolicy(context.Context, *iampb.SetIamPolicyRequest, ...gax.CallOption) (*iampb.Policy, error)
	TestIamPermissions(context.Context, *iampb.TestIamPermissionsRequest, ...gax.CallOption) (*iampb.TestIamPermissionsResponse, error)
}

// SubscriberClient is a client for interacting with Cloud Pub/Sub API.
// Methods, except Close, may be called concurrently. However, fields must not be modified concurrently with method calls.
//
// The service that an application uses to manipulate subscriptions and to
// consume messages from a subscription via the Pull method or by
// establishing a bi-directional stream using the StreamingPull method.
type SubscriberClient struct {
	// The internal transport-dependent client.
	internalClient internalSubscriberClient

	// The call options for this service.
	CallOptions *SubscriberCallOptions
}

// Wrapper methods routed to the internal client.

// Close closes the connection to the API service. The user should invoke this when
// the client is no longer required.
func (c *SubscriberClient) Close() error {
	return c.internalClient.Close()
}

// setGoogleClientInfo sets the name and version of the application in
// the `x-goog-api-client` header passed on each request. Intended for
// use by Google-written clients.
func (c *SubscriberClient) setGoogleClientInfo(keyval ...string) {
	c.internalClient.setGoogleClientInfo(keyval...)
}

// Connection returns a connection to the API service.
//
// Deprecated.
func (c *SubscriberClient) Connection() *grpc.ClientConn {
	return c.internalClient.Connection()
}

// CreateSubscription creates a subscription to a given topic. See the [resource name rules]
// (https://cloud.google.com/pubsub/docs/admin#resource_names (at https://cloud.google.com/pubsub/docs/admin#resource_names)).
// If the subscription already exists, returns ALREADY_EXISTS.
// If the corresponding topic doesn’t exist, returns NOT_FOUND.
//
// If the name is not provided in the request, the server will assign a random
// name for this subscription on the same project as the topic, conforming
// to the [resource name format]
// (https://cloud.google.com/pubsub/docs/admin#resource_names (at https://cloud.google.com/pubsub/docs/admin#resource_names)). The generated
// name is populated in the returned Subscription object. Note that for REST
// API requests, you must specify a name in the request.
func (c *SubscriberClient) CreateSubscription(ctx context.Context, req *pubsubpb.Subscription, opts ...gax.CallOption) (*pubsubpb.Subscription, error) {
	return c.internalClient.CreateSubscription(ctx, req, opts...)
}

// GetSubscription gets the configuration details of a subscription.
func (c *SubscriberClient) GetSubscription(ctx context.Context, req *pubsubpb.GetSubscriptionRequest, opts ...gax.CallOption) (*pubsubpb.Subscription, error) {
	return c.internalClient.GetSubscription(ctx, req, opts...)
}

// UpdateSubscription updates an existing subscription. Note that certain properties of a
// subscription, such as its topic, are not modifiable.
func (c *SubscriberClient) UpdateSubscription(ctx context.Context, req *pubsubpb.UpdateSubscriptionRequest, opts ...gax.CallOption) (*pubsubpb.Subscription, error) {
	return c.internalClient.UpdateSubscription(ctx, req, opts...)
}

// ListSubscriptions lists matching subscriptions.
func (c *SubscriberClient) ListSubscriptions(ctx context.Context, req *pubsubpb.ListSubscriptionsRequest, opts ...gax.CallOption) *SubscriptionIterator {
	return c.internalClient.ListSubscriptions(ctx, req, opts...)
}

// DeleteSubscription deletes an existing subscription. All messages retained in the subscription
// are immediately dropped. Calls to Pull after deletion will return
// NOT_FOUND. After a subscription is deleted, a new one may be created with
// the same name, but the new one has no association with the old
// subscription or its topic unless the same topic is specified.
func (c *SubscriberClient) DeleteSubscription(ctx context.Context, req *pubsubpb.DeleteSubscriptionRequest, opts ...gax.CallOption) error {
	return c.internalClient.DeleteSubscription(ctx, req, opts...)
}

// ModifyAckDeadline modifies the ack deadline for a specific message. This method is useful
// to indicate that more time is needed to process a message by the
// subscriber, or to make the message available for redelivery if the
// processing was interrupted. Note that this does not modify the
// subscription-level ackDeadlineSeconds used for subsequent messages.
func (c *SubscriberClient) ModifyAckDeadline(ctx context.Context, req *pubsubpb.ModifyAckDeadlineRequest, opts ...gax.CallOption) error {
	return c.internalClient.ModifyAckDeadline(ctx, req, opts...)
}

// Acknowledge acknowledges the messages associated with the ack_ids in the
// AcknowledgeRequest. The Pub/Sub system can remove the relevant messages
// from the subscription.
//
// Acknowledging a message whose ack deadline has expired may succeed,
// but such a message may be redelivered later. Acknowledging a message more
// than once will not result in an error.
func (c *SubscriberClient) Acknowledge(ctx context.Context, req *pubsubpb.AcknowledgeRequest, opts ...gax.CallOption) error {
	return c.internalClient.Acknowledge(ctx, req, opts...)
}

// Pull pulls messages from the server. The server may return UNAVAILABLE if
// there are too many concurrent pull requests pending for the given
// subscription.
func (c *SubscriberClient) Pull(ctx context.Context, req *pubsubpb.PullRequest, opts ...gax.CallOption) (*pubsubpb.PullResponse, error) {
	return c.internalClient.Pull(ctx, req, opts...)
}

// StreamingPull establishes a stream with the server, which sends messages down to the
// client. The client streams acknowledgements and ack deadline modifications
// back to the server. The server will close the stream and return the status
// on any error. The server may close the stream with status UNAVAILABLE to
// reassign server-side resources, in which case, the client should
// re-establish the stream. Flow control can be achieved by configuring the
// underlying RPC channel.
func (c *SubscriberClient) StreamingPull(ctx context.Context, opts ...gax.CallOption) (pubsubpb.Subscriber_StreamingPullClient, error) {
	return c.internalClient.StreamingPull(ctx, opts...)
}

// ModifyPushConfig modifies the PushConfig for a specified subscription.
//
// This may be used to change a push subscription to a pull one (signified by
// an empty PushConfig) or vice versa, or change the endpoint URL and other
// attributes of a push subscription. Messages will accumulate for delivery
// continuously through the call regardless of changes to the PushConfig.
func (c *SubscriberClient) ModifyPushConfig(ctx context.Context, req *pubsubpb.ModifyPushConfigRequest, opts ...gax.CallOption) error {
	return c.internalClient.ModifyPushConfig(ctx, req, opts...)
}

// GetSnapshot gets the configuration details of a snapshot. Snapshots are used in
// Seek (at https://cloud.google.com/pubsub/docs/replay-overview)
// operations, which allow you to manage message acknowledgments in bulk. That
// is, you can set the acknowledgment state of messages in an existing
// subscription to the state captured by a snapshot.
func (c *SubscriberClient) GetSnapshot(ctx context.Context, req *pubsubpb.GetSnapshotRequest, opts ...gax.CallOption) (*pubsubpb.Snapshot, error) {
	return c.internalClient.GetSnapshot(ctx, req, opts...)
}

// ListSnapshots lists the existing snapshots. Snapshots are used in Seek (at https://cloud.google.com/pubsub/docs/replay-overview) operations, which
// allow you to manage message acknowledgments in bulk. That is, you can set
// the acknowledgment state of messages in an existing subscription to the
// state captured by a snapshot.
func (c *SubscriberClient) ListSnapshots(ctx context.Context, req *pubsubpb.ListSnapshotsRequest, opts ...gax.CallOption) *SnapshotIterator {
	return c.internalClient.ListSnapshots(ctx, req, opts...)
}

// CreateSnapshot creates a snapshot from the requested subscription. Snapshots are used in
// Seek (at https://cloud.google.com/pubsub/docs/replay-overview) operations,
// which allow you to manage message acknowledgments in bulk. That is, you can
// set the acknowledgment state of messages in an existing subscription to the
// state captured by a snapshot.
// If the snapshot already exists, returns ALREADY_EXISTS.
// If the requested subscription doesn’t exist, returns NOT_FOUND.
// If the backlog in the subscription is too old – and the resulting snapshot
// would expire in less than 1 hour – then FAILED_PRECONDITION is returned.
// See also the Snapshot.expire_time field. If the name is not provided in
// the request, the server will assign a random
// name for this snapshot on the same project as the subscription, conforming
// to the [resource name format]
// (https://cloud.google.com/pubsub/docs/admin#resource_names (at https://cloud.google.com/pubsub/docs/admin#resource_names)). The
// generated name is populated in the returned Snapshot object. Note that for
// REST API requests, you must specify a name in the request.
func (c *SubscriberClient) CreateSnapshot(ctx context.Context, req *pubsubpb.CreateSnapshotRequest, opts ...gax.CallOption) (*pubsubpb.Snapshot, error) {
	return c.internalClient.CreateSnapshot(ctx, req, opts...)
}

// UpdateSnapshot updates an existing snapshot. Snapshots are used in
// Seek (at https://cloud.google.com/pubsub/docs/replay-overview)
// operations, which allow
// you to manage message acknowledgments in bulk. That is, you can set the
// acknowledgment state of messages in an existing subscription to the state
// captured by a snapshot.
func (c *SubscriberClient) UpdateSnapshot(ctx context.Context, req *pubsubpb.UpdateSnapshotRequest, opts ...gax.CallOption) (*pubsubpb.Snapshot, error) {
	return c.internalClient.UpdateSnapshot(ctx, req, opts...)
}

// DeleteSnapshot removes an existing snapshot. Snapshots are used in [Seek]
// (https://cloud.google.com/pubsub/docs/replay-overview (at https://cloud.google.com/pubsub/docs/replay-overview)) operations, which
// allow you to manage message acknowledgments in bulk. That is, you can set
// the acknowledgment state of messages in an existing subscription to the
// state captured by a snapshot.
// When the snapshot is deleted, all messages retained in the snapshot
// are immediately dropped. After a snapshot is deleted, a new one may be
// created with the same name, but the new one has no association with the old
// snapshot or its subscription, unless the same subscription is specified.
func (c *SubscriberClient) DeleteSnapshot(ctx context.Context, req *pubsubpb.DeleteSnapshotRequest, opts ...gax.CallOption) error {
	return c.internalClient.DeleteSnapshot(ctx, req, opts...)
}

// Seek seeks an existing subscription to a point in time or to a given snapshot,
// whichever is provided in the request. Snapshots are used in [Seek]
// (https://cloud.google.com/pubsub/docs/replay-overview (at https://cloud.google.com/pubsub/docs/replay-overview)) operations, which
// allow you to manage message acknowledgments in bulk. That is, you can set
// the acknowledgment state of messages in an existing subscription to the
// state captured by a snapshot. Note that both the subscription and the
// snapshot must be on the same topic.
func (c *SubscriberClient) Seek(ctx context.Context, req *pubsubpb.SeekRequest, opts ...gax.CallOption) (*pubsubpb.SeekResponse, error) {
	return c.internalClient.Seek(ctx, req, opts...)
}

// GetIamPolicy gets the access control policy for a resource. Returns an empty policy
// if the resource exists and does not have a policy set.
func (c *SubscriberClient) GetIamPolicy(ctx context.Context, req *iampb.GetIamPolicyRequest, opts ...gax.CallOption) (*iampb.Policy, error) {
	return c.internalClient.GetIamPolicy(ctx, req, opts...)
}

// SetIamPolicy sets the access control policy on the specified resource. Replaces
// any existing policy.
//
// Can return NOT_FOUND, INVALID_ARGUMENT, and PERMISSION_DENIED
// errors.
func (c *SubscriberClient) SetIamPolicy(ctx context.Context, req *iampb.SetIamPolicyRequest, opts ...gax.CallOption) (*iampb.Policy, error) {
	return c.internalClient.SetIamPolicy(ctx, req, opts...)
}

// TestIamPermissions returns permissions that a caller has on the specified resource. If the
// resource does not exist, this will return an empty set of
// permissions, not a NOT_FOUND error.
//
// Note: This operation is designed to be used for building
// permission-aware UIs and command-line tools, not for authorization
// checking. This operation may “fail open” without warning.
func (c *SubscriberClient) TestIamPermissions(ctx context.Context, req *iampb.TestIamPermissionsRequest, opts ...gax.CallOption) (*iampb.TestIamPermissionsResponse, error) {
	return c.internalClient.TestIamPermissions(ctx, req, opts...)
}

// subscriberGRPCClient is a client for interacting with Cloud Pub/Sub API over gRPC transport.
//
// Methods, except Close, may be called concurrently. However, fields must not be modified concurrently with method calls.
type subscriberGRPCClient struct {
	// Connection pool of gRPC connections to the service.
	connPool gtransport.ConnPool

	// flag to opt out of default deadlines via GOOGLE_API_GO_EXPERIMENTAL_DISABLE_DEFAULT_DEADLINE
	disableDeadlines bool

	// Points back to the CallOptions field of the containing SubscriberClient
	CallOptions **SubscriberCallOptions

	// The gRPC API client.
	subscriberClient pubsubpb.SubscriberClient

	iamPolicyClient iampb.IAMPolicyClient

	// The x-goog-* metadata to be sent with each request.
	xGoogMetadata metadata.MD
}

// NewSubscriberClient creates a new subscriber client based on gRPC.
// The returned client must be Closed when it is done being used to clean up its underlying connections.
//
// The service that an application uses to manipulate subscriptions and to
// consume messages from a subscription via the Pull method or by
// establishing a bi-directional stream using the StreamingPull method.
func NewSubscriberClient(ctx context.Context, opts ...option.ClientOption) (*SubscriberClient, error) {
	clientOpts := defaultSubscriberGRPCClientOptions()
	if newSubscriberClientHook != nil {
		hookOpts, err := newSubscriberClientHook(ctx, clientHookParams{})
		if err != nil {
			return nil, err
		}
		clientOpts = append(clientOpts, hookOpts...)
	}

	disableDeadlines, err := checkDisableDeadlines()
	if err != nil {
		return nil, err
	}

	connPool, err := gtransport.DialPool(ctx, append(clientOpts, opts...)...)
	if err != nil {
		return nil, err
	}
	client := SubscriberClient{CallOptions: defaultSubscriberCallOptions()}

	c := &subscriberGRPCClient{
		connPool:         connPool,
		disableDeadlines: disableDeadlines,
		subscriberClient: pubsubpb.NewSubscriberClient(connPool),
		CallOptions:      &client.CallOptions,
		iamPolicyClient:  iampb.NewIAMPolicyClient(connPool),
	}
	c.setGoogleClientInfo()

	client.internalClient = c

	return &client, nil
}

// Connection returns a connection to the API service.
//
// Deprecated.
func (c *subscriberGRPCClient) Connection() *grpc.ClientConn {
	return c.connPool.Conn()
}

// setGoogleClientInfo sets the name and version of the application in
// the `x-goog-api-client` header passed on each request. Intended for
// use by Google-written clients.
func (c *subscriberGRPCClient) setGoogleClientInfo(keyval ...string) {
	kv := append([]string{"gl-go", versionGo()}, keyval...)
	kv = append(kv, "gapic", versionClient, "gax", gax.Version, "grpc", grpc.Version)
	c.xGoogMetadata = metadata.Pairs("x-goog-api-client", gax.XGoogHeader(kv...))
}

// Close closes the connection to the API service. The user should invoke this when
// the client is no longer required.
func (c *subscriberGRPCClient) Close() error {
	return c.connPool.Close()
}

func (c *subscriberGRPCClient) CreateSubscription(ctx context.Context, req *pubsubpb.Subscription, opts ...gax.CallOption) (*pubsubpb.Subscription, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "name", url.QueryEscape(req.GetName())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).CreateSubscription[0:len((*c.CallOptions).CreateSubscription):len((*c.CallOptions).CreateSubscription)], opts...)
	var resp *pubsubpb.Subscription
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.CreateSubscription(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) GetSubscription(ctx context.Context, req *pubsubpb.GetSubscriptionRequest, opts ...gax.CallOption) (*pubsubpb.Subscription, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).GetSubscription[0:len((*c.CallOptions).GetSubscription):len((*c.CallOptions).GetSubscription)], opts...)
	var resp *pubsubpb.Subscription
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.GetSubscription(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) UpdateSubscription(ctx context.Context, req *pubsubpb.UpdateSubscriptionRequest, opts ...gax.CallOption) (*pubsubpb.Subscription, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription.name", url.QueryEscape(req.GetSubscription().GetName())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).UpdateSubscription[0:len((*c.CallOptions).UpdateSubscription):len((*c.CallOptions).UpdateSubscription)], opts...)
	var resp *pubsubpb.Subscription
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.UpdateSubscription(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) ListSubscriptions(ctx context.Context, req *pubsubpb.ListSubscriptionsRequest, opts ...gax.CallOption) *SubscriptionIterator {
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "project", url.QueryEscape(req.GetProject())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).ListSubscriptions[0:len((*c.CallOptions).ListSubscriptions):len((*c.CallOptions).ListSubscriptions)], opts...)
	it := &SubscriptionIterator{}
	req = proto.Clone(req).(*pubsubpb.ListSubscriptionsRequest)
	it.InternalFetch = func(pageSize int, pageToken string) ([]*pubsubpb.Subscription, string, error) {
		var resp *pubsubpb.ListSubscriptionsResponse
		req.PageToken = pageToken
		if pageSize > math.MaxInt32 {
			req.PageSize = math.MaxInt32
		} else {
			req.PageSize = int32(pageSize)
		}
		err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
			var err error
			resp, err = c.subscriberClient.ListSubscriptions(ctx, req, settings.GRPC...)
			return err
		}, opts...)
		if err != nil {
			return nil, "", err
		}

		it.Response = resp
		return resp.GetSubscriptions(), resp.GetNextPageToken(), nil
	}
	fetch := func(pageSize int, pageToken string) (string, error) {
		items, nextPageToken, err := it.InternalFetch(pageSize, pageToken)
		if err != nil {
			return "", err
		}
		it.items = append(it.items, items...)
		return nextPageToken, nil
	}
	it.pageInfo, it.nextFunc = iterator.NewPageInfo(fetch, it.bufLen, it.takeBuf)
	it.pageInfo.MaxSize = int(req.GetPageSize())
	it.pageInfo.Token = req.GetPageToken()
	return it
}

func (c *subscriberGRPCClient) DeleteSubscription(ctx context.Context, req *pubsubpb.DeleteSubscriptionRequest, opts ...gax.CallOption) error {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).DeleteSubscription[0:len((*c.CallOptions).DeleteSubscription):len((*c.CallOptions).DeleteSubscription)], opts...)
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		_, err = c.subscriberClient.DeleteSubscription(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	return err
}

func (c *subscriberGRPCClient) ModifyAckDeadline(ctx context.Context, req *pubsubpb.ModifyAckDeadlineRequest, opts ...gax.CallOption) error {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).ModifyAckDeadline[0:len((*c.CallOptions).ModifyAckDeadline):len((*c.CallOptions).ModifyAckDeadline)], opts...)
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		_, err = c.subscriberClient.ModifyAckDeadline(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	return err
}

func (c *subscriberGRPCClient) Acknowledge(ctx context.Context, req *pubsubpb.AcknowledgeRequest, opts ...gax.CallOption) error {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).Acknowledge[0:len((*c.CallOptions).Acknowledge):len((*c.CallOptions).Acknowledge)], opts...)
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		_, err = c.subscriberClient.Acknowledge(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	return err
}

func (c *subscriberGRPCClient) Pull(ctx context.Context, req *pubsubpb.PullRequest, opts ...gax.CallOption) (*pubsubpb.PullResponse, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).Pull[0:len((*c.CallOptions).Pull):len((*c.CallOptions).Pull)], opts...)
	var resp *pubsubpb.PullResponse
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.Pull(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) StreamingPull(ctx context.Context, opts ...gax.CallOption) (pubsubpb.Subscriber_StreamingPullClient, error) {
	ctx = insertMetadata(ctx, c.xGoogMetadata)
	var resp pubsubpb.Subscriber_StreamingPullClient
	opts = append((*c.CallOptions).StreamingPull[0:len((*c.CallOptions).StreamingPull):len((*c.CallOptions).StreamingPull)], opts...)
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.StreamingPull(ctx, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) ModifyPushConfig(ctx context.Context, req *pubsubpb.ModifyPushConfigRequest, opts ...gax.CallOption) error {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).ModifyPushConfig[0:len((*c.CallOptions).ModifyPushConfig):len((*c.CallOptions).ModifyPushConfig)], opts...)
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		_, err = c.subscriberClient.ModifyPushConfig(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	return err
}

func (c *subscriberGRPCClient) GetSnapshot(ctx context.Context, req *pubsubpb.GetSnapshotRequest, opts ...gax.CallOption) (*pubsubpb.Snapshot, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "snapshot", url.QueryEscape(req.GetSnapshot())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).GetSnapshot[0:len((*c.CallOptions).GetSnapshot):len((*c.CallOptions).GetSnapshot)], opts...)
	var resp *pubsubpb.Snapshot
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.GetSnapshot(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) ListSnapshots(ctx context.Context, req *pubsubpb.ListSnapshotsRequest, opts ...gax.CallOption) *SnapshotIterator {
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "project", url.QueryEscape(req.GetProject())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).ListSnapshots[0:len((*c.CallOptions).ListSnapshots):len((*c.CallOptions).ListSnapshots)], opts...)
	it := &SnapshotIterator{}
	req = proto.Clone(req).(*pubsubpb.ListSnapshotsRequest)
	it.InternalFetch = func(pageSize int, pageToken string) ([]*pubsubpb.Snapshot, string, error) {
		var resp *pubsubpb.ListSnapshotsResponse
		req.PageToken = pageToken
		if pageSize > math.MaxInt32 {
			req.PageSize = math.MaxInt32
		} else {
			req.PageSize = int32(pageSize)
		}
		err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
			var err error
			resp, err = c.subscriberClient.ListSnapshots(ctx, req, settings.GRPC...)
			return err
		}, opts...)
		if err != nil {
			return nil, "", err
		}

		it.Response = resp
		return resp.GetSnapshots(), resp.GetNextPageToken(), nil
	}
	fetch := func(pageSize int, pageToken string) (string, error) {
		items, nextPageToken, err := it.InternalFetch(pageSize, pageToken)
		if err != nil {
			return "", err
		}
		it.items = append(it.items, items...)
		return nextPageToken, nil
	}
	it.pageInfo, it.nextFunc = iterator.NewPageInfo(fetch, it.bufLen, it.takeBuf)
	it.pageInfo.MaxSize = int(req.GetPageSize())
	it.pageInfo.Token = req.GetPageToken()
	return it
}

func (c *subscriberGRPCClient) CreateSnapshot(ctx context.Context, req *pubsubpb.CreateSnapshotRequest, opts ...gax.CallOption) (*pubsubpb.Snapshot, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "name", url.QueryEscape(req.GetName())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).CreateSnapshot[0:len((*c.CallOptions).CreateSnapshot):len((*c.CallOptions).CreateSnapshot)], opts...)
	var resp *pubsubpb.Snapshot
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.CreateSnapshot(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) UpdateSnapshot(ctx context.Context, req *pubsubpb.UpdateSnapshotRequest, opts ...gax.CallOption) (*pubsubpb.Snapshot, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "snapshot.name", url.QueryEscape(req.GetSnapshot().GetName())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).UpdateSnapshot[0:len((*c.CallOptions).UpdateSnapshot):len((*c.CallOptions).UpdateSnapshot)], opts...)
	var resp *pubsubpb.Snapshot
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.UpdateSnapshot(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) DeleteSnapshot(ctx context.Context, req *pubsubpb.DeleteSnapshotRequest, opts ...gax.CallOption) error {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "snapshot", url.QueryEscape(req.GetSnapshot())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).DeleteSnapshot[0:len((*c.CallOptions).DeleteSnapshot):len((*c.CallOptions).DeleteSnapshot)], opts...)
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		_, err = c.subscriberClient.DeleteSnapshot(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	return err
}

func (c *subscriberGRPCClient) Seek(ctx context.Context, req *pubsubpb.SeekRequest, opts ...gax.CallOption) (*pubsubpb.SeekResponse, error) {
	if _, ok := ctx.Deadline(); !ok && !c.disableDeadlines {
		cctx, cancel := context.WithTimeout(ctx, 60000*time.Millisecond)
		defer cancel()
		ctx = cctx
	}
	md := metadata.Pairs("x-goog-request-params", fmt.Sprintf("%s=%v", "subscription", url.QueryEscape(req.GetSubscription())))
	ctx = insertMetadata(ctx, c.xGoogMetadata, md)
	opts = append((*c.CallOptions).Seek[0:len((*c.CallOptions).Seek):len((*c.CallOptions).Seek)], opts...)
	var resp *pubsubpb.SeekResponse
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.subscriberClient.Seek(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) GetIamPolicy(ctx context.Context, req *iampb.GetIamPolicyRequest, opts ...gax.CallOption) (*iampb.Policy, error) {
	ctx = insertMetadata(ctx, c.xGoogMetadata)
	opts = append((*c.CallOptions).GetIamPolicy[0:len((*c.CallOptions).GetIamPolicy):len((*c.CallOptions).GetIamPolicy)], opts...)
	var resp *iampb.Policy
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.iamPolicyClient.GetIamPolicy(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) SetIamPolicy(ctx context.Context, req *iampb.SetIamPolicyRequest, opts ...gax.CallOption) (*iampb.Policy, error) {
	ctx = insertMetadata(ctx, c.xGoogMetadata)
	opts = append((*c.CallOptions).SetIamPolicy[0:len((*c.CallOptions).SetIamPolicy):len((*c.CallOptions).SetIamPolicy)], opts...)
	var resp *iampb.Policy
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.iamPolicyClient.SetIamPolicy(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func (c *subscriberGRPCClient) TestIamPermissions(ctx context.Context, req *iampb.TestIamPermissionsRequest, opts ...gax.CallOption) (*iampb.TestIamPermissionsResponse, error) {
	ctx = insertMetadata(ctx, c.xGoogMetadata)
	opts = append((*c.CallOptions).TestIamPermissions[0:len((*c.CallOptions).TestIamPermissions):len((*c.CallOptions).TestIamPermissions)], opts...)
	var resp *iampb.TestIamPermissionsResponse
	err := gax.Invoke(ctx, func(ctx context.Context, settings gax.CallSettings) error {
		var err error
		resp, err = c.iamPolicyClient.TestIamPermissions(ctx, req, settings.GRPC...)
		return err
	}, opts...)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

// SnapshotIterator manages a stream of *pubsubpb.Snapshot.
type SnapshotIterator struct {
	items    []*pubsubpb.Snapshot
	pageInfo *iterator.PageInfo
	nextFunc func() error

	// Response is the raw response for the current page.
	// It must be cast to the RPC response type.
	// Calling Next() or InternalFetch() updates this value.
	Response interface{}

	// InternalFetch is for use by the Google Cloud Libraries only.
	// It is not part of the stable interface of this package.
	//
	// InternalFetch returns results from a single call to the underlying RPC.
	// The number of results is no greater than pageSize.
	// If there are no more results, nextPageToken is empty and err is nil.
	InternalFetch func(pageSize int, pageToken string) (results []*pubsubpb.Snapshot, nextPageToken string, err error)
}

// PageInfo supports pagination. See the google.golang.org/api/iterator package for details.
func (it *SnapshotIterator) PageInfo() *iterator.PageInfo {
	return it.pageInfo
}

// Next returns the next result. Its second return value is iterator.Done if there are no more
// results. Once Next returns Done, all subsequent calls will return Done.
func (it *SnapshotIterator) Next() (*pubsubpb.Snapshot, error) {
	var item *pubsubpb.Snapshot
	if err := it.nextFunc(); err != nil {
		return item, err
	}
	item = it.items[0]
	it.items = it.items[1:]
	return item, nil
}

func (it *SnapshotIterator) bufLen() int {
	return len(it.items)
}

func (it *SnapshotIterator) takeBuf() interface{} {
	b := it.items
	it.items = nil
	return b
}

// SubscriptionIterator manages a stream of *pubsubpb.Subscription.
type SubscriptionIterator struct {
	items    []*pubsubpb.Subscription
	pageInfo *iterator.PageInfo
	nextFunc func() error

	// Response is the raw response for the current page.
	// It must be cast to the RPC response type.
	// Calling Next() or InternalFetch() updates this value.
	Response interface{}

	// InternalFetch is for use by the Google Cloud Libraries only.
	// It is not part of the stable interface of this package.
	//
	// InternalFetch returns results from a single call to the underlying RPC.
	// The number of results is no greater than pageSize.
	// If there are no more results, nextPageToken is empty and err is nil.
	InternalFetch func(pageSize int, pageToken string) (results []*pubsubpb.Subscription, nextPageToken string, err error)
}

// PageInfo supports pagination. See the google.golang.org/api/iterator package for details.
func (it *SubscriptionIterator) PageInfo() *iterator.PageInfo {
	return it.pageInfo
}

// Next returns the next result. Its second return value is iterator.Done if there are no more
// results. Once Next returns Done, all subsequent calls will return Done.
func (it *SubscriptionIterator) Next() (*pubsubpb.Subscription, error) {
	var item *pubsubpb.Subscription
	if err := it.nextFunc(); err != nil {
		return item, err
	}
	item = it.items[0]
	it.items = it.items[1:]
	return item, nil
}

func (it *SubscriptionIterator) bufLen() int {
	return len(it.items)
}

func (it *SubscriptionIterator) takeBuf() interface{} {
	b := it.items
	it.items = nil
	return b
}