content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.beam.sdk.fn.stream;
  
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.ClientCallStreamObserver;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.ClientResponseObserver;
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.StreamObserver;
  
  /**
   * A {@link ClientResponseObserver} which delegates all {@link StreamObserver} calls.
   *
   * <p>Used to wrap existing {@link StreamObserver}s to be able to install an {@link
   * ClientCallStreamObserver#setOnReadyHandler(Runnable) onReadyHandler} and a handler invoked when
   * the stream terminates.
   *
   * <p>This is as thread-safe as the underlying stream observer that is being wrapped.
   */
  public final class ForwardingClientResponseObserver<ReqT, RespT>
      implements ClientResponseObserver<RespT, ReqT> {
    public static <ReqT, RespT> ForwardingClientResponseObserver<ReqT, RespT> create(
        StreamObserver<ReqT> inbound, Runnable onReadyHandler) {
      return new ForwardingClientResponseObserver<>(inbound, onReadyHandler, () -> {});
    }
  
    public static <ReqT, RespT> ForwardingClientResponseObserver<ReqT, RespT> create(
        StreamObserver<ReqT> inbound, Runnable onReadyHandler, Runnable onDoneHandler) {
      return new ForwardingClientResponseObserver<>(inbound, onReadyHandler, onDoneHandler);
    }
  
    private final Runnable onReadyHandler;
    private final Runnable onDoneHandler;
    private final StreamObserver<ReqT> inboundObserver;
  
    private ForwardingClientResponseObserver(
        StreamObserver<ReqT> inboundObserver, Runnable onReadyHandler, Runnable onDoneHandler) {
      this.inboundObserver = inboundObserver;
      this.onReadyHandler = onReadyHandler;
      this.onDoneHandler = onDoneHandler;
    }
  
    @Override
    public void onNext(ReqT value) {
      inboundObserver.onNext(value);
    }
  
    @Override
    public void onError(Throwable t) {
      onDoneHandler.run();
      inboundObserver.onError(t);
    }
  
    @Override
    public void onCompleted() {
      onDoneHandler.run();
      inboundObserver.onCompleted();
    }
  
    @Override
    public void beforeStart(ClientCallStreamObserver<RespT> stream) {
      stream.setOnReadyHandler(onReadyHandler);
    }
  }
  