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Google Api eXtensions for Java (gRPC)
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/*
 * Copyright 2017 Google LLC
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google LLC nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.google.api.gax.grpc;

import com.google.api.gax.rpc.ApiCallContext;
import com.google.api.gax.rpc.RequestParamsExtractor;
import com.google.api.gax.rpc.RequestUrlParamsEncoder;
import com.google.api.gax.rpc.ResponseObserver;
import com.google.api.gax.rpc.ServerStreamingCallable;
import com.google.common.base.Preconditions;

/**
 * A {@code ServerStreamingCallable} that extracts values from the fields of the request and inserts
 * them into headers.
 *
 * Package-private for internal usage.
 */
class GrpcServerStreamingRequestParamCallable
    extends ServerStreamingCallable {
  private final ServerStreamingCallable callable;
  private final RequestUrlParamsEncoder paramsEncoder;

  GrpcServerStreamingRequestParamCallable(
      ServerStreamingCallable callable,
      RequestParamsExtractor paramsExtractor) {
    this.callable = Preconditions.checkNotNull(callable);
    this.paramsEncoder = new RequestUrlParamsEncoder<>(Preconditions.checkNotNull(paramsExtractor));
  }

  @Override
  public void call(
      RequestT request, ResponseObserver responseObserver, ApiCallContext context) {
    callable.call(request, responseObserver, contextWithParamsEncoder(request, context));
  }

  private ApiCallContext contextWithParamsEncoder(RequestT request, ApiCallContext inputContext) {
    ApiCallContext newCallContext = inputContext;
    String encodedHeader = paramsEncoder.encode(request);
    if (!encodedHeader.isEmpty()) {
      newCallContext =
          GrpcCallContext.createDefault()
              .nullToSelf(inputContext)
              .withRequestParamsDynamicHeaderOption(encodedHeader);
    }
    return newCallContext;
  }
}