code: /*
   * SPDX-License-Identifier: Apache-2.0
   * Copyright 2018-2020 The Feast Authors
   *
   * 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
   *
   *     https://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 feast.serving.service;
  
  import feast.proto.serving.ServingAPIProto;
  import feast.proto.serving.TransformationServiceAPIProto.TransformFeaturesRequest;
  import feast.proto.serving.TransformationServiceAPIProto.TransformFeaturesResponse;
  import feast.proto.serving.TransformationServiceAPIProto.ValueType;
  import feast.proto.types.ValueProto;
  import java.util.List;
  import java.util.Set;
  import org.apache.commons.lang3.tuple.Pair;
  
  public interface TransformationService {
    /**
     * Apply on demand transformations for the specified ODFVs.
     *
     * @param transformFeaturesRequest proto containing the ODFV references and necessary data
     * @return a proto object containing the response
     */
    TransformFeaturesResponse transformFeatures(TransformFeaturesRequest transformFeaturesRequest);
  
    /**
     * Extract the list of on demand feature sources from a list of ODFV references.
     *
     * @param onDemandFeatureReferences list of ODFV references to be parsed
     * @return list of on demand feature sources
     */
    List<ServingAPIProto.FeatureReferenceV2> extractOnDemandFeaturesDependencies(
        List<ServingAPIProto.FeatureReferenceV2> onDemandFeatureReferences);
  
    /**
     * Process a response from the feature transformation server by augmenting the given lists of
     * field maps and status maps with the correct fields from the response.
     *
     * @param transformFeaturesResponse response to be processed
     * @param onDemandFeatureViewName name of ODFV to which the response corresponds
     * @param onDemandFeatureStringReferences set of all ODFV references that should be kept
     * @param responseBuilder {@link ServingAPIProto.GetOnlineFeaturesResponse.Builder}
     */
    void processTransformFeaturesResponse(
        TransformFeaturesResponse transformFeaturesResponse,
        String onDemandFeatureViewName,
        Set<String> onDemandFeatureStringReferences,
        ServingAPIProto.GetOnlineFeaturesResponse.Builder responseBuilder);
  
    /**
     * Serialize data into Arrow IPC format, to be sent to the Python feature transformation server.
     *
     * @param values list of field maps to be serialized
     * @return the data packaged into a ValueType proto object
     */
    ValueType serializeValuesIntoArrowIPC(List<Pair<String, List<ValueProto.Value>>> values);
  }
  