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.arrow.flight;
  
  import io.grpc.stub.StreamObserver;
  import java.util.function.Consumer;
  import java.util.function.Function;
  import org.apache.arrow.flight.FlightProducer.StreamListener;
  import org.apache.arrow.flight.grpc.StatusUtils;
  import org.apache.arrow.util.AutoCloseables;
  
  /**
   * Shim listener to avoid exposing GRPC internals.
   *
   * @param <FROM> From Type
   * @param <TO> To Type
   */
  class StreamPipe<FROM, TO> implements StreamListener<FROM> {
  
    private final StreamObserver<TO> delegate;
    private final Function<FROM, TO> mapFunction;
    private final Consumer<Throwable> errorHandler;
    private AutoCloseable resource;
    private boolean closed = false;
  
    /**
     * Wrap the given gRPC StreamObserver with a transformation function.
     *
     * @param delegate The {@link StreamObserver} to wrap.
     * @param func The transformation function.
     * @param errorHandler A handler for uncaught exceptions (e.g. if something tries to double-close
     *     this stream).
     * @param <FROM> The source type.
     * @param <TO> The output type.
     * @return A wrapped listener.
     */
    public static <FROM, TO> StreamPipe<FROM, TO> wrap(
        StreamObserver<TO> delegate, Function<FROM, TO> func, Consumer<Throwable> errorHandler) {
      return new StreamPipe<>(delegate, func, errorHandler);
    }
  
    public StreamPipe(
        StreamObserver<TO> delegate, Function<FROM, TO> func, Consumer<Throwable> errorHandler) {
      super();
      this.delegate = delegate;
      this.mapFunction = func;
      this.errorHandler = errorHandler;
      this.resource = null;
    }
  
    /** Set an AutoCloseable resource to be cleaned up when the gRPC observer is to be completed. */
    void setAutoCloseable(AutoCloseable ac) {
      resource = ac;
    }
  
    @Override
    public void onNext(FROM val) {
      delegate.onNext(mapFunction.apply(val));
    }
  
    @Override
    public void onError(Throwable t) {
      if (closed) {
        errorHandler.accept(t);
        return;
      }
      try {
        AutoCloseables.close(resource);
      } catch (Exception e) {
        errorHandler.accept(e);
      } finally {
        // Set closed to true in case onError throws, so that we don't try to close again
        closed = true;
        delegate.onError(StatusUtils.toGrpcException(t));
      }
    }
  
    @Override
    public void onCompleted() {
      if (closed) {
        errorHandler.accept(new IllegalStateException("Tried to complete already-completed call"));
        return;
      }
      try {
        AutoCloseables.close(resource);
      } catch (Exception e) {
        errorHandler.accept(e);
      } finally {
        // Set closed to true in case onCompleted throws, so that we don't try to close again
        closed = true;
        delegate.onCompleted();
      }
    }
  
    /** Ensure this stream has been completed. */
    void ensureCompleted() {
      if (!closed) {
        onCompleted();
      }
    }
  }
  