lib/pubsub.dart - third_party/gcloud - Git at Google

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';

 import 'package:googleapis/pubsub/v1.dart' as pubsub;
 import 'package:http/http.dart' as http;

 import 'common.dart';
 import 'service_scope.dart' as ss;
 import 'src/common_utils.dart';

 export 'common.dart';

 part 'src/pubsub_impl.dart';

 const Symbol _pubsubKey = #gcloud.pubsub;

 /// Access the [PubSub] object available in the current service scope.
 ///
 /// The returned object will be the one which was previously registered with
 /// [registerPubSubService] within the current (or a parent) service scope.
 ///
 /// Accessing this getter outside of a service scope will result in an error.
 /// See the `package:gcloud/service_scope.dart` library for more information.
 PubSub get pubsubService => ss.lookup(_pubsubKey) as PubSub;

 /// Registers the [pubsub] object within the current service scope.
 ///
 /// The provided `pubsub` object will be available via the top-level
 /// `pubsubService` getter.
 ///
 /// Calling this function outside of a service scope will result in an error.
 /// Calling this function more than once inside the same service scope is not
 /// allowed.
 void registerPubSubService(PubSub pubsub) {
   ss.register(_pubsubKey, pubsub);
 }

 /// A Cloud Pub/Sub client.
 ///
 /// Connects to the Cloud Pub/Sub service and gives access to its operations.
 ///
 /// Google Cloud Pub/Sub is a reliable, many-to-many, asynchronous messaging
 /// service from Google Cloud Platform. A detailed overview is available on
 /// [Pub/Sub docs](https://developers.google.com/pubsub/overview).
 ///
 /// To access Pub/Sub, an authenticate HTTP client is required. This client
 /// should as a minimum provide access to the scopes `PubSub.Scopes`.
 ///
 /// The following example shows how to access Pub/Sub using a service account
 /// and pull a message from a subscription.
 ///
 ///     import 'package:http/http.dart' as http;
 ///     import 'package:googleapis_auth/auth_io.dart' as auth;
 ///     import 'package:gcloud/pubsub.dart';
 ///
 ///     Future<http.Client> createClient() {
 ///       // Service account credentials retrieved from Cloud Console.
 ///       String creds =
 ///           r'''
 ///           {
 ///             "private_key_id": ...,
 ///             "private_key": ...,
 ///             "client_email": ...,
 ///             "client_id": ...,
 ///             "type": "service_account"
 ///           }''';
 ///       return auth.clientViaServiceAccount(
 ///           new auth.ServiceAccountCredentials.fromJson(creds),
 ///           PubSub.Scopes);
 ///     }
 ///
 ///     main() {
 ///       var project = 'my-project';
 ///       var client;
 ///       var pubsub;
 ///       createClient().then((c) {
 ///         client = c;
 ///         pubsub = new PubSub(client, project);
 ///         return pubsub.lookupSubscription('my-subscription');
 ///       })
 ///       .then((Subscription subscription) => subscription.pull())
 ///       .then((PullEvent event) => print('Message ${event.message.asString}'))
 ///       .whenComplete(() => client.close());
 ///     }
 ///
 /// When working with topics and subscriptions they are referred to using
 /// names. These names can be either relative names or absolute names.
 ///
 /// An absolute name of a topic starts with `projects/` and has the form:
 ///
 ///     projects/<project-id>/topics/<relative-name>
 ///
 /// When a relative topic name is used, its absolute name is generated by
 /// pre-pending `projects/<project-id>/topics/`, where `<project-id>` is the
 /// project id passed to the constructor.
 ///
 /// An absolute name of a subscription starts with `projects/` and has the
 /// form:
 ///
 ///     projects/<project-id>/subscriptions/<relative-name>
 ///
 /// When a relative subscription name is used, its absolute name is
 /// generated by pre-pending `projects/<project-id>/subscriptions/`, where
 /// `<project-id>` is the project id passed to the constructor.
 ///
 abstract class PubSub {
   /// List of required OAuth2 scopes for Pub/Sub operation.
   // ignore: constant_identifier_names
   static const SCOPES = [pubsub.PubsubApi.pubsubScope];

   /// Access Pub/Sub using an authenticated client.
   ///
   /// The [client] is an authenticated HTTP client. This client must
   /// provide access to at least the scopes in `PubSub.Scopes`.
   ///
   /// The [project] is the name of the Google Cloud project.
   ///
   /// Returns an object providing access to Pub/Sub. The passed-in [client] will
   /// not be closed automatically. The caller is responsible for closing it.
   factory PubSub(http.Client client, String project) {
     var emulator = Platform.environment['PUBSUB_EMULATOR_HOST'];
     return emulator == null
         ? _PubSubImpl(client, project)
         : _PubSubImpl.rootUrl(client, project, 'http://$emulator/');
   }

   /// The name of the project.
   String get project;

   /// Create a new topic named [name].
   ///
   /// The [name] can be either an absolute name or a relative name.
   ///
   /// Returns a `Future` which completes with the newly created topic.
   Future<Topic> createTopic(String name);

   /// Delete topic named [name].
   ///
   /// The [name] can be either an absolute name or a relative name.
   ///
   /// Returns a `Future` which completes with `null` when the operation
   /// is finished.
   Future deleteTopic(String name);

   /// Look up topic named [name].
   ///
   /// The [name] can be either an absolute name or a relative name.
   ///
   /// Returns a `Future` which completes with the topic.
   Future<Topic> lookupTopic(String name);

   /// Lists all topics.
   ///
   /// Returns a `Stream` of topics.
   Stream<Topic> listTopics();

   /// Start paging through all topics.
   ///
   /// The maximum number of topics in each page is specified in [pageSize].
   ///
   /// Returns a `Future` which completes with a `Page` object holding the
   /// first page. Use the `Page` object to move to the next page of topics.
   Future<Page<Topic>> pageTopics({int pageSize = 50});

   /// Create a new subscription named [name] listening on topic [topic].
   ///
   /// If [endpoint] is passed this will create a push subscription.
   ///
   /// Otherwise this will create a pull subscription.
   ///
   /// The [name] can be either an absolute name or a relative name.
   ///
   /// Returns a `Future` which completes with the newly created subscription.
   Future<Subscription> createSubscription(String name, String topic,
       {Uri endpoint});

   /// Delete subscription named [name].
   ///
   /// The [name] can be either an absolute name or a relative name.
   ///
   /// Returns a `Future` which completes with the subscription.
   Future deleteSubscription(String name);

   /// Lookup subscription with named [name].
   ///
   /// The [name] can be either an absolute name or a relative name.
   ///
   /// Returns a `Future` which completes with the subscription.
   Future<Subscription> lookupSubscription(String name);

   /// List subscriptions.
   ///
   /// If [query] is passed this will list all subscriptions matching the query.
   ///
   /// Otherwise this will list all subscriptions.
   ///
   /// The only supported query string is the name of a topic. If a name of a
   /// topic is passed as [query], this will list all subscriptions on that
   /// topic.
   ///
   /// Returns a `Stream` of subscriptions.
   Stream<Subscription> listSubscriptions([String query]);

   /// Start paging through subscriptions.
   ///
   /// If [topic] is passed this will list all subscriptions to that topic.
   ///
   /// Otherwise this will list all subscriptions.
   ///
   /// The maximum number of subscriptions in each page is specified in
   /// [pageSize]
   ///
   /// Returns a `Future` which completes with a `Page` object holding the
   /// first page. Use the `Page` object to move to the next page of
   /// subscriptions.
   Future<Page<Subscription>> pageSubscriptions(
       {String topic, int pageSize = 50});
 }

 /// A Pub/Sub topic.
 ///
 /// A topic is used by a publisher to publish (send) messages.
 abstract class Topic {
   /// The relative name of this topic.
   String get name;

   /// The name of the project for this topic.
   String get project;

   /// The absolute name of this topic.
   String get absoluteName;

   /// Delete this topic.
   ///
   /// Returns a `Future` which completes with `null` when the operation
   /// is finished.
   Future delete();

   /// Publish a message.
   ///
   /// Returns a `Future` which completes with `null` when the operation
   /// is finished.
   Future publish(Message message);

   /// Publish a string as a message.
   ///
   /// The message will get the attributes specified in [attributes].
   ///
   /// The [attributes] are passed together with the message to the receiver.
   ///
   /// Returns a `Future` which completes with `null` when the operation
   /// is finished.
   Future publishString(String message, {Map<String, String> attributes});

   /// Publish bytes as a message.
   ///
   /// The message will get the attributes specified in [attributes].
   ///
   /// The [attributes] are passed together with the message to the receiver.
   ///
   /// Returns a `Future` which completes with `null` when the operation
   /// is finished.
   Future publishBytes(List<int> message, {Map<String, String> attributes});
 }

 /// A Pub/Sub subscription
 ///
 /// A subscription is used to receive messages. A subscriber application
 /// create a subscription on a topic to receive messages from it.
 ///
 /// Subscriptions can be either pull subscriptions or push subscriptions.
 ///
 /// For a pull subscription the receiver calls the `Subscription.pull`
 /// method on the subscription object to get the next message.
 ///
 /// For a push subscription a HTTPS endpoint is configured. This endpoint get
 /// POST requests with the messages.
 abstract class Subscription {
   /// The relative name of this subscription.
   String get name;

   /// The name of the project for this subscription.
   String get project;

   /// The absolute name of this subscription.
   String get absoluteName;

   /// The topic subscribed to.
   Topic get topic;

   /// Whether this is a push subscription.
   ///
   /// A push subscription is configured with an endpoint URI, and messages
   /// are automatically sent to this endpoint without needing to call [pull].
   bool get isPush;

   /// Whether this is a pull subscription.
   ///
   /// A subscription without a configured endpoint URI is a pull subscription.
   /// Messages are not delivered automatically, but must instead be requested
   /// using [pull].
   bool get isPull;

   /// The URI for the push endpoint.
   ///
   /// If this is a pull subscription this is `null`.
   Uri? get endpoint;

   /// Update the push configuration with a new endpoint.
   ///
   /// if [endpoint] is `null`, the subscription stops delivering messages
   /// automatically, and becomes a pull subscription, if it isn't already.
   ///
   /// If [endpoint] is not `null`, the subscription will be a push
   /// subscription, if it wasn't already, and Pub/Sub will start automatically
   /// delivering message to the endpoint URI.
   ///
   /// Returns a `Future` which completes when the operation completes.
   Future updatePushConfiguration(Uri endpoint);

   /// Delete this subscription.
   ///
   /// Returns a `Future` which completes when the operation completes.
   Future delete();

   /// Pull a message from the subscription.
   ///
   /// If `wait` is `true` (the default), the method will wait for a message
   /// to become available, and will then complete the `Future` with a
   /// `PullEvent` containing the message.
   ///
   /// If [wait] is `false`, the method will complete the returned `Future`
   /// with `null` if it finds that there are no messages available.
   Future<PullEvent?> pull({bool wait = true});
 }

 /// The content of a Pub/Sub message.
 ///
 /// All Pub/Sub messages consist of a body of binary data and has an optional
 /// set of attributes (key-value pairs) associated with it.
 ///
 /// A `Message` contains the message body a list of bytes. The message body can
 /// be read and written as a String, in which case the string is converted to
 /// or from UTF-8 automatically.
 abstract class Message {
   /// Creates a new message with a String for the body. The String will
   /// be UTF-8 encoded to create the actual binary body for the message.
   ///
   /// Message attributes can be passed in the [attributes] map.
   factory Message.withString(String message, {Map<String, String> attributes}) =
       _MessageImpl.withString;

   /// Creates a new message with a binary body.
   ///
   /// Message attributes can be passed in the [attributes] Map.
   factory Message.withBytes(List<int> message,
       {Map<String, String> attributes}) = _MessageImpl.withBytes;

   /// The message body as a String.
   ///
   /// The binary body is decoded into a String using an UTF-8 decoder.
   ///
   /// If the body is not UTF-8 encoded use the [asBytes] getter and manually
   /// apply the correct decoding.
   String get asString;

   /// The message body as bytes.
   List<int> get asBytes;

   /// The attributes for this message.
   Map<String, String> get attributes;
 }

 /// A Pub/Sub pull event.
 ///
 /// Instances of this class are returned when pulling messages with
 /// [Subscription.pull].
 abstract class PullEvent {
   /// The message content.
   Message get message;

   /// Acknowledge reception of this message.
   ///
   /// Returns a `Future` which completes with `null` when the acknowledge has
   /// been processed.
   Future acknowledge();
 }

 /// Pub/Sub push event.
 ///
 /// This class can be used in a HTTP server for decoding messages pushed to
 /// an endpoint.
 ///
 /// When a message is received on a push endpoint use the [PushEvent.fromJson]
 /// constructor with the HTTP body to decode the received message.
 ///
 /// E.g. with a `dart:io` HTTP handler:
 ///
 ///     void pushHandler(HttpRequest request) {
 ///       // Decode the JSON body.
 ///       request.transform(UTF8.decoder).join('').then((body) {
 ///         // Decode the JSON into a push message.
 ///         var message = new PushMessage.fromJson(body)
 ///
 ///         // Process the message...
 ///
 ///         // Respond with status code 20X to acknowledge the message.
 ///         response.statusCode = statusCode;
 ///         response.close();
 ///       });
 ///     }
 ////
 abstract class PushEvent {
   /// The message content.
   Message get message;

   /// The absolute name of the subscription.
   String get subscriptionName;

   /// Create a `PushMessage` from JSON received on a Pub/Sub push endpoint.
   factory PushEvent.fromJson(String json) = _PushEventImpl.fromJson;
 }
	// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	import 'dart:async';
	import 'dart:collection';
	import 'dart:convert';
	import 'dart:io';

	import 'package:googleapis/pubsub/v1.dart' as pubsub;
	import 'package:http/http.dart' as http;

	import 'common.dart';
	import 'service_scope.dart' as ss;
	import 'src/common_utils.dart';

	export 'common.dart';

	part 'src/pubsub_impl.dart';

	const Symbol _pubsubKey = #gcloud.pubsub;

	/// Access the [PubSub] object available in the current service scope.
	///
	/// The returned object will be the one which was previously registered with
	/// [registerPubSubService] within the current (or a parent) service scope.
	///
	/// Accessing this getter outside of a service scope will result in an error.
	/// See the `package:gcloud/service_scope.dart` library for more information.
	PubSub get pubsubService => ss.lookup(_pubsubKey) as PubSub;

	/// Registers the [pubsub] object within the current service scope.
	///
	/// The provided `pubsub` object will be available via the top-level
	/// `pubsubService` getter.
	///
	/// Calling this function outside of a service scope will result in an error.
	/// Calling this function more than once inside the same service scope is not
	/// allowed.
	void registerPubSubService(PubSub pubsub) {
	ss.register(_pubsubKey, pubsub);
	}

	/// A Cloud Pub/Sub client.
	///
	/// Connects to the Cloud Pub/Sub service and gives access to its operations.
	///
	/// Google Cloud Pub/Sub is a reliable, many-to-many, asynchronous messaging
	/// service from Google Cloud Platform. A detailed overview is available on
	/// [Pub/Sub docs](https://developers.google.com/pubsub/overview).
	///
	/// To access Pub/Sub, an authenticate HTTP client is required. This client
	/// should as a minimum provide access to the scopes `PubSub.Scopes`.
	///
	/// The following example shows how to access Pub/Sub using a service account
	/// and pull a message from a subscription.
	///
	/// import 'package:http/http.dart' as http;
	/// import 'package:googleapis_auth/auth_io.dart' as auth;
	/// import 'package:gcloud/pubsub.dart';
	///
	/// Future<http.Client> createClient() {
	/// // Service account credentials retrieved from Cloud Console.
	/// String creds =
	/// r'''
	/// {
	/// "private_key_id": ...,
	/// "private_key": ...,
	/// "client_email": ...,
	/// "client_id": ...,
	/// "type": "service_account"
	/// }''';
	/// return auth.clientViaServiceAccount(
	/// new auth.ServiceAccountCredentials.fromJson(creds),
	/// PubSub.Scopes);
	/// }
	///
	/// main() {
	/// var project = 'my-project';
	/// var client;
	/// var pubsub;
	/// createClient().then((c) {
	/// client = c;
	/// pubsub = new PubSub(client, project);
	/// return pubsub.lookupSubscription('my-subscription');
	/// })
	/// .then((Subscription subscription) => subscription.pull())
	/// .then((PullEvent event) => print('Message ${event.message.asString}'))
	/// .whenComplete(() => client.close());
	/// }
	///
	/// When working with topics and subscriptions they are referred to using
	/// names. These names can be either relative names or absolute names.
	///
	/// An absolute name of a topic starts with `projects/` and has the form:
	///
	/// projects/<project-id>/topics/<relative-name>
	///
	/// When a relative topic name is used, its absolute name is generated by
	/// pre-pending `projects/<project-id>/topics/`, where `<project-id>` is the
	/// project id passed to the constructor.
	///
	/// An absolute name of a subscription starts with `projects/` and has the
	/// form:
	///
	/// projects/<project-id>/subscriptions/<relative-name>
	///
	/// When a relative subscription name is used, its absolute name is
	/// generated by pre-pending `projects/<project-id>/subscriptions/`, where
	/// `<project-id>` is the project id passed to the constructor.
	///
	abstract class PubSub {
	/// List of required OAuth2 scopes for Pub/Sub operation.
	// ignore: constant_identifier_names
	static const SCOPES = [pubsub.PubsubApi.pubsubScope];

	/// Access Pub/Sub using an authenticated client.
	///
	/// The [client] is an authenticated HTTP client. This client must
	/// provide access to at least the scopes in `PubSub.Scopes`.
	///
	/// The [project] is the name of the Google Cloud project.
	///
	/// Returns an object providing access to Pub/Sub. The passed-in [client] will
	/// not be closed automatically. The caller is responsible for closing it.
	factory PubSub(http.Client client, String project) {
	var emulator = Platform.environment['PUBSUB_EMULATOR_HOST'];
	return emulator == null
	? _PubSubImpl(client, project)
	: _PubSubImpl.rootUrl(client, project, 'http://$emulator/');
	}

	/// The name of the project.
	String get project;

	/// Create a new topic named [name].
	///
	/// The [name] can be either an absolute name or a relative name.
	///
	/// Returns a `Future` which completes with the newly created topic.
	Future<Topic> createTopic(String name);

	/// Delete topic named [name].
	///
	/// The [name] can be either an absolute name or a relative name.
	///
	/// Returns a `Future` which completes with `null` when the operation
	/// is finished.
	Future deleteTopic(String name);

	/// Look up topic named [name].
	///
	/// The [name] can be either an absolute name or a relative name.
	///
	/// Returns a `Future` which completes with the topic.
	Future<Topic> lookupTopic(String name);

	/// Lists all topics.
	///
	/// Returns a `Stream` of topics.
	Stream<Topic> listTopics();

	/// Start paging through all topics.
	///
	/// The maximum number of topics in each page is specified in [pageSize].
	///
	/// Returns a `Future` which completes with a `Page` object holding the
	/// first page. Use the `Page` object to move to the next page of topics.
	Future<Page<Topic>> pageTopics({int pageSize = 50});

	/// Create a new subscription named [name] listening on topic [topic].
	///
	/// If [endpoint] is passed this will create a push subscription.
	///
	/// Otherwise this will create a pull subscription.
	///
	/// The [name] can be either an absolute name or a relative name.
	///
	/// Returns a `Future` which completes with the newly created subscription.
	Future<Subscription> createSubscription(String name, String topic,
	{Uri endpoint});

	/// Delete subscription named [name].
	///
	/// The [name] can be either an absolute name or a relative name.
	///
	/// Returns a `Future` which completes with the subscription.
	Future deleteSubscription(String name);

	/// Lookup subscription with named [name].
	///
	/// The [name] can be either an absolute name or a relative name.
	///
	/// Returns a `Future` which completes with the subscription.
	Future<Subscription> lookupSubscription(String name);

	/// List subscriptions.
	///
	/// If [query] is passed this will list all subscriptions matching the query.
	///
	/// Otherwise this will list all subscriptions.
	///
	/// The only supported query string is the name of a topic. If a name of a
	/// topic is passed as [query], this will list all subscriptions on that
	/// topic.
	///
	/// Returns a `Stream` of subscriptions.
	Stream<Subscription> listSubscriptions([String query]);

	/// Start paging through subscriptions.
	///
	/// If [topic] is passed this will list all subscriptions to that topic.
	///
	/// Otherwise this will list all subscriptions.
	///
	/// The maximum number of subscriptions in each page is specified in
	/// [pageSize]
	///
	/// Returns a `Future` which completes with a `Page` object holding the
	/// first page. Use the `Page` object to move to the next page of
	/// subscriptions.
	Future<Page<Subscription>> pageSubscriptions(
	{String topic, int pageSize = 50});
	}

	/// A Pub/Sub topic.
	///
	/// A topic is used by a publisher to publish (send) messages.
	abstract class Topic {
	/// The relative name of this topic.
	String get name;

	/// The name of the project for this topic.
	String get project;

	/// The absolute name of this topic.
	String get absoluteName;

	/// Delete this topic.
	///
	/// Returns a `Future` which completes with `null` when the operation
	/// is finished.
	Future delete();

	/// Publish a message.
	///
	/// Returns a `Future` which completes with `null` when the operation
	/// is finished.
	Future publish(Message message);

	/// Publish a string as a message.
	///
	/// The message will get the attributes specified in [attributes].
	///
	/// The [attributes] are passed together with the message to the receiver.
	///
	/// Returns a `Future` which completes with `null` when the operation
	/// is finished.
	Future publishString(String message, {Map<String, String> attributes});

	/// Publish bytes as a message.
	///
	/// The message will get the attributes specified in [attributes].
	///
	/// The [attributes] are passed together with the message to the receiver.
	///
	/// Returns a `Future` which completes with `null` when the operation
	/// is finished.
	Future publishBytes(List<int> message, {Map<String, String> attributes});
	}

	/// A Pub/Sub subscription
	///
	/// A subscription is used to receive messages. A subscriber application
	/// create a subscription on a topic to receive messages from it.
	///
	/// Subscriptions can be either pull subscriptions or push subscriptions.
	///
	/// For a pull subscription the receiver calls the `Subscription.pull`
	/// method on the subscription object to get the next message.
	///
	/// For a push subscription a HTTPS endpoint is configured. This endpoint get
	/// POST requests with the messages.
	abstract class Subscription {
	/// The relative name of this subscription.
	String get name;

	/// The name of the project for this subscription.
	String get project;

	/// The absolute name of this subscription.
	String get absoluteName;

	/// The topic subscribed to.
	Topic get topic;

	/// Whether this is a push subscription.
	///
	/// A push subscription is configured with an endpoint URI, and messages
	/// are automatically sent to this endpoint without needing to call [pull].
	bool get isPush;

	/// Whether this is a pull subscription.
	///
	/// A subscription without a configured endpoint URI is a pull subscription.
	/// Messages are not delivered automatically, but must instead be requested
	/// using [pull].
	bool get isPull;

	/// The URI for the push endpoint.
	///
	/// If this is a pull subscription this is `null`.
	Uri? get endpoint;

	/// Update the push configuration with a new endpoint.
	///
	/// if [endpoint] is `null`, the subscription stops delivering messages
	/// automatically, and becomes a pull subscription, if it isn't already.
	///
	/// If [endpoint] is not `null`, the subscription will be a push
	/// subscription, if it wasn't already, and Pub/Sub will start automatically
	/// delivering message to the endpoint URI.
	///
	/// Returns a `Future` which completes when the operation completes.
	Future updatePushConfiguration(Uri endpoint);

	/// Delete this subscription.
	///
	/// Returns a `Future` which completes when the operation completes.
	Future delete();

	/// Pull a message from the subscription.
	///
	/// If `wait` is `true` (the default), the method will wait for a message
	/// to become available, and will then complete the `Future` with a
	/// `PullEvent` containing the message.
	///
	/// If [wait] is `false`, the method will complete the returned `Future`
	/// with `null` if it finds that there are no messages available.
	Future<PullEvent?> pull({bool wait = true});
	}

	/// The content of a Pub/Sub message.
	///
	/// All Pub/Sub messages consist of a body of binary data and has an optional
	/// set of attributes (key-value pairs) associated with it.
	///
	/// A `Message` contains the message body a list of bytes. The message body can
	/// be read and written as a String, in which case the string is converted to
	/// or from UTF-8 automatically.
	abstract class Message {
	/// Creates a new message with a String for the body. The String will
	/// be UTF-8 encoded to create the actual binary body for the message.
	///
	/// Message attributes can be passed in the [attributes] map.
	factory Message.withString(String message, {Map<String, String> attributes}) =
	_MessageImpl.withString;

	/// Creates a new message with a binary body.
	///
	/// Message attributes can be passed in the [attributes] Map.
	factory Message.withBytes(List<int> message,
	{Map<String, String> attributes}) = _MessageImpl.withBytes;

	/// The message body as a String.
	///
	/// The binary body is decoded into a String using an UTF-8 decoder.
	///
	/// If the body is not UTF-8 encoded use the [asBytes] getter and manually
	/// apply the correct decoding.
	String get asString;

	/// The message body as bytes.
	List<int> get asBytes;

	/// The attributes for this message.
	Map<String, String> get attributes;
	}

	/// A Pub/Sub pull event.
	///
	/// Instances of this class are returned when pulling messages with
	/// [Subscription.pull].
	abstract class PullEvent {
	/// The message content.
	Message get message;

	/// Acknowledge reception of this message.
	///
	/// Returns a `Future` which completes with `null` when the acknowledge has
	/// been processed.
	Future acknowledge();
	}

	/// Pub/Sub push event.
	///
	/// This class can be used in a HTTP server for decoding messages pushed to
	/// an endpoint.
	///
	/// When a message is received on a push endpoint use the [PushEvent.fromJson]
	/// constructor with the HTTP body to decode the received message.
	///
	/// E.g. with a `dart:io` HTTP handler:
	///
	/// void pushHandler(HttpRequest request) {
	/// // Decode the JSON body.
	/// request.transform(UTF8.decoder).join('').then((body) {
	/// // Decode the JSON into a push message.
	/// var message = new PushMessage.fromJson(body)
	///
	/// // Process the message...
	///
	/// // Respond with status code 20X to acknowledge the message.
	/// response.statusCode = statusCode;
	/// response.close();
	/// });
	/// }
	////
	abstract class PushEvent {
	/// The message content.
	Message get message;

	/// The absolute name of the subscription.
	String get subscriptionName;

	/// Create a `PushMessage` from JSON received on a Pub/Sub push endpoint.
	factory PushEvent.fromJson(String json) = _PushEventImpl.fromJson;
	}