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 * Copyright 2023 Google LLC
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 * 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.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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 * contributors may be used to endorse or promote products derived from
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 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package com.google.api.gax.httpjson;

import com.google.api.core.ApiFuture;
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.UnaryCallable;
import com.google.api.gax.rpc.internal.Headers;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;

/**
 * A {@code UnaryCallable} that extracts values from the fields of the request and inserts them into
 * headers.
 *
 * <p>Package-private for internal usage.
 */
class HttpJsonUnaryRequestParamCallable<RequestT, ResponseT>
    extends UnaryCallable<RequestT, ResponseT> {
  private final UnaryCallable<RequestT, ResponseT> callable;
  private final RequestUrlParamsEncoder<RequestT> paramsEncoder;

  public HttpJsonUnaryRequestParamCallable(
      UnaryCallable<RequestT, ResponseT> callable,
      RequestParamsExtractor<RequestT> paramsExtractor) {
    this.callable = Preconditions.checkNotNull(callable);
    this.paramsEncoder = new RequestUrlParamsEncoder<>(Preconditions.checkNotNull(paramsExtractor));
  }

  @Override
  public ApiFuture<ResponseT> futureCall(RequestT request, ApiCallContext context) {
    ApiCallContext newCallContext = context;
    String encodedHeader = paramsEncoder.encode(request);
    if (!encodedHeader.isEmpty()) {
      newCallContext =
          HttpJsonCallContext.createDefault()
              .nullToSelf(context)
              .withExtraHeaders(
                  ImmutableMap.of(
                      Headers.DYNAMIC_ROUTING_HEADER_KEY, ImmutableList.of(encodedHeader)));
    }
    return callable.futureCall(request, newCallContext);
  }
}
