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Spring Framework on Google Cloud Pub/Sub Module
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/*
 * Copyright 2017-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      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.
 */

package com.google.cloud.spring.pubsub.support;

import com.google.cloud.pubsub.v1.MessageReceiver;
import com.google.cloud.pubsub.v1.Subscriber;
import com.google.cloud.pubsub.v1.stub.SubscriberStub;
import com.google.pubsub.v1.PullRequest;

/**
 * Interface used by the {@link com.google.cloud.spring.pubsub.core.PubSubTemplate} to create
 * supporting objects for consuming messages from Pub/Sub subscriptions.
 */
public interface SubscriberFactory {

  /**
   * Method to get the project id.
   *
   * @return the project id
   * @since 1.1
   */
  String getProjectId();

  /**
   * Create a {@link Subscriber} for the specified subscription name and wired it up to
   * asynchronously deliver messages to the provided {@link MessageReceiver}.
   *
   * @param subscriptionName the name of the subscription
   * @param receiver the callback for receiving messages asynchronously
   * @return the {@link Subscriber} that was created to bind the receiver to the subscription
   */
  Subscriber createSubscriber(String subscriptionName, MessageReceiver receiver);

  /**
   * Create a {@link PullRequest} for synchronously pulling a number of messages from a Google Cloud
   * Pub/Sub subscription.
   *
   * @param subscriptionName the name of the subscription
   * @param maxMessages the maximum number of pulled messages; must be greater than zero. If null is
   *     passed in, then up to Integer.MAX_VALUE messages will be requested.
   * @param returnImmediately causes the pull request to return immediately even if subscription
   *     doesn't contain enough messages to satisfy {@code maxMessages}. Setting this parameter to
   *     {@code true} is not recommended as it may result in long delays in message delivery.
   * @return the pull request that can be executed using a {@link SubscriberStub}
   */
  PullRequest createPullRequest(
      String subscriptionName, Integer maxMessages, Boolean returnImmediately);

  /**
   * Create a {@link SubscriberStub} that is needed to execute {@link PullRequest}s.
   *
   * @param subscriptionName the subscription name
   * @return the {@link SubscriberStub} used for executing {@link PullRequest}s
   */
  SubscriberStub createSubscriberStub(String subscriptionName);
}