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.kafka.common.feature;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Objects;
  import java.util.stream.Collectors;
  
  import static java.util.stream.Collectors.joining;
  
  /**
   * Represents an immutable dictionary with key being feature name, and value being <VersionRangeType>.
   * Also provides API to convert the features and their version ranges to/from a map.
   *
   * This class can be instantiated only using its factory functions, with the important ones being:
   * Features.supportedFeatures(...) and Features.finalizedFeatures(...).
   *
   * @param <VersionRangeType> is the type of version range.
   * @see SupportedVersionRange
   */
  public class Features<VersionRangeType extends BaseVersionRange> {
      private final Map<String, VersionRangeType> features;
  
      /**
       * Constructor is made private, as for readability it is preferred the caller uses one of the
       * static factory functions for instantiation (see below).
       *
       * @param features   Map of feature name to a type of VersionRange.
       */
      private Features(Map<String, VersionRangeType> features) {
          Objects.requireNonNull(features, "Provided features can not be null.");
          this.features = features;
      }
  
      /**
       * @param features   Map of feature name to SupportedVersionRange.
       *
       * @return           Returns a new Features object representing supported features.
       */
      public static Features<SupportedVersionRange> supportedFeatures(Map<String, SupportedVersionRange> features) {
          return new Features<>(features);
      }
  
      public static Features<SupportedVersionRange> emptySupportedFeatures() {
          return new Features<>(new HashMap<>());
      }
  
      public Map<String, VersionRangeType> features() {
          return features;
      }
  
      public boolean empty() {
          return features.isEmpty();
      }
  
      /**
       * @param  feature   name of the feature
       *
       * @return           the VersionRangeType corresponding to the feature name, or null if the
       *                   feature is absent
       */
      public VersionRangeType get(String feature) {
          return features.get(feature);
      }
  
      public String toString() {
          return String.format(
              "Features{%s}",
              features
                  .entrySet()
                  .stream()
                  .map(entry -> String.format("(%s -> %s)", entry.getKey(), entry.getValue()))
                  .collect(joining(", "))
          );
      }
  
      /**
       * @return   A map representation of the underlying features. The returned value can be converted
       *           back to Features using one of the from*FeaturesMap() APIs of this class.
       */
      public Map<String, Map<String, Short>> toMap() {
          return features.entrySet().stream().collect(
              Collectors.toMap(
                  Map.Entry::getKey,
                  entry -> entry.getValue().toMap()));
      }
  
      /**
       * An interface that defines behavior to convert from a Map to an object of type BaseVersionRange.
       */
      private interface MapToBaseVersionRangeConverter<V extends BaseVersionRange> {
  
          /**
           * Convert the map representation of an object of type <V>, to an object of type <V>.
           *
           * @param  baseVersionRangeMap   the map representation of a BaseVersionRange object.
           *
           * @return                       the object of type <V>
           */
          V fromMap(Map<String, Short> baseVersionRangeMap);
      }
  
      private static <V extends BaseVersionRange> Features<V> fromFeaturesMap(
          Map<String, Map<String, Short>> featuresMap, MapToBaseVersionRangeConverter<V> converter) {
          return new Features<>(featuresMap.entrySet().stream().collect(
              Collectors.toMap(
                  Map.Entry::getKey,
                  entry -> converter.fromMap(entry.getValue()))));
      }
  
      /**
       * Converts from a map to Features<SupportedVersionRange>.
       *
       * @param featuresMap  the map representation of a Features<SupportedVersionRange> object,
       *                     generated using the toMap() API.
       *
       * @return             the Features<SupportedVersionRange> object
       */
      public static Features<SupportedVersionRange> fromSupportedFeaturesMap(
          Map<String, Map<String, Short>> featuresMap) {
          return fromFeaturesMap(featuresMap, SupportedVersionRange::fromMap);
      }
  
      @Override
      public boolean equals(Object other) {
          if (this == other) {
              return true;
          }
          if (!(other instanceof Features)) {
              return false;
          }
  
          final Features<?> that = (Features<?>) other;
          return Objects.equals(this.features, that.features);
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(features);
      }
  }
  