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.connectors.redis.common;
  
  import com.google.common.hash.Hashing;
  import com.google.protobuf.InvalidProtocolBufferException;
  import com.google.protobuf.Timestamp;
  import feast.proto.serving.ServingAPIProto;
  import feast.proto.types.ValueProto;
  import feast.serving.connectors.Feature;
  import feast.serving.connectors.ProtoFeature;
  import java.nio.ByteBuffer;
  import java.nio.charset.StandardCharsets;
  import java.util.*;
  import java.util.stream.Collectors;
  
  public class RedisHashDecoder {
  
    /**
     * Converts all retrieved Redis Hash values based on EntityRows into {@link Feature}
     *
     * @param redisHashValues retrieved Redis Hash values based on EntityRows
     * @param byteToFeatureIdxMap map to decode bytes back to FeatureReference
     * @param timestampPrefix timestamp prefix
     * @return Map of {@link ServingAPIProto.FeatureReferenceV2} to {@link Feature}
     */
    public static List<Feature> retrieveFeature(
        Map<byte[], byte[]> redisHashValues,
        Map<ByteBuffer, Integer> byteToFeatureIdxMap,
        List<ServingAPIProto.FeatureReferenceV2> featureReferences,
        String timestampPrefix) {
      Map<String, Timestamp> featureTableTimestampMap =
          redisHashValues.entrySet().stream()
              .filter(e -> new String(e.getKey()).startsWith(timestampPrefix))
              .collect(
                  Collectors.toMap(
                      e -> new String(e.getKey()).substring(timestampPrefix.length() + 1),
                      e -> {
                        try {
                          return Timestamp.parseFrom(e.getValue());
                        } catch (InvalidProtocolBufferException ex) {
                          throw new RuntimeException(
                              "Couldn't parse timestamp proto while pulling data from Redis");
                        }
                      }));
      List<Feature> results = new ArrayList<>(Collections.nCopies(featureReferences.size(), null));
  
      for (Map.Entry<byte[], byte[]> entry : redisHashValues.entrySet()) {
        Integer featureIdx = byteToFeatureIdxMap.get(ByteBuffer.wrap(entry.getKey()));
        if (featureIdx == null) {
          continue;
        }
  
        ValueProto.Value v;
        try {
          v = ValueProto.Value.parseFrom(entry.getValue());
        } catch (InvalidProtocolBufferException ex) {
          throw new RuntimeException(
              "Couldn't parse feature value proto while pulling data from Redis");
        }
        results.set(
            featureIdx,
            new ProtoFeature(
                featureReferences.get(featureIdx),
                featureTableTimestampMap.get(featureReferences.get(featureIdx).getFeatureViewName()),
                v));
      }
  
      return results;
    }
  
    public static byte[] getTimestampRedisHashKeyBytes(String featureTable, String timestampPrefix) {
      String timestampRedisHashKeyStr = timestampPrefix + ":" + featureTable;
      return timestampRedisHashKeyStr.getBytes();
    }
  
    public static byte[] getFeatureReferenceRedisHashKeyBytes(
        ServingAPIProto.FeatureReferenceV2 featureReference) {
      String delimitedFeatureReference =
          featureReference.getFeatureViewName() + ":" + featureReference.getFeatureName();
      return Hashing.murmur3_32()
          .hashString(delimitedFeatureReference, StandardCharsets.UTF_8)
          .asBytes();
    }
  }
  