FakePublisherServiceImpl.java

/*
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * 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
 *
 *       http://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.pubsub;

import com.google.common.base.Optional;
import com.google.pubsub.v1.PublishRequest;
import com.google.pubsub.v1.PublishResponse;
import com.google.pubsub.v1.PublisherGrpc.PublisherImplBase;
import io.grpc.stub.StreamObserver;
import java.util.Queue;
import java.util.concurrent.LinkedBlockingQueue;

/**
 * A fake implementation of {@link PublisherImplBase}, that can be used to test clients of a 
 * Cloud Pub/Sub Publisher.
 */
class FakePublisherServiceImpl extends PublisherImplBase {

  private final Queue<Response> publishResponses = new LinkedBlockingQueue<>();

  /**
   * Class used to save the state of a possible response. 
   */
  private static class Response {
    Optional<PublishResponse> publishResponse;
    Optional<Throwable> error;
  
    public Response(PublishResponse publishResponse) {
      this.publishResponse = Optional.of(publishResponse);
      this.error = Optional.absent();
    }
  
    public Response(Throwable exception) {
      this.publishResponse = Optional.absent();
      this.error = Optional.of(exception);
    }
  
    public PublishResponse getPublishResponse() {
      return publishResponse.get();
    }
  
    public Throwable getError() {
      return error.get();
    }
  
    boolean isError() {
      return error.isPresent();
    }
  }

  @Override
  public void publish(PublishRequest request, StreamObserver<PublishResponse> responseObserver) {
    Response response = null;
    synchronized (publishResponses) {
      response = publishResponses.poll();
      try {
        if (response.isError()) {
          responseObserver.onError(response.getError());
          return;
        }

        responseObserver.onNext(response.getPublishResponse());
        responseObserver.onCompleted();
      } finally {
        publishResponses.notifyAll();
      }
    }
  }

  public FakePublisherServiceImpl addPublishResponse(PublishResponse publishResponse) {
    synchronized (publishResponses) {
      publishResponses.add(new Response(publishResponse));
    }
    return this;
  }

  public FakePublisherServiceImpl addPublishResponse(
      PublishResponse.Builder publishResponseBuilder) {
    addPublishResponse(publishResponseBuilder.build());
    return this;
  }

  public FakePublisherServiceImpl addPublishError(Throwable error) {
    synchronized (publishResponses) {
      publishResponses.add(new Response(error));
    }
    return this;
  }

  public void reset() {
    synchronized (publishResponses) {
      publishResponses.clear();
      publishResponses.notifyAll();
    }
  }

  public void waitForNoOutstandingResponses() throws InterruptedException {
    synchronized (publishResponses) {
      while (!publishResponses.isEmpty()) {
        publishResponses.wait();
      }
    }
  }
}