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.connect.transforms;
  
  import org.apache.kafka.common.cache.Cache;
  import org.apache.kafka.common.cache.LRUCache;
  import org.apache.kafka.common.cache.SynchronizedCache;
  import org.apache.kafka.common.config.ConfigDef;
  import org.apache.kafka.common.utils.AppInfoParser;
  import org.apache.kafka.connect.components.Versioned;
  import org.apache.kafka.connect.connector.ConnectRecord;
  import org.apache.kafka.connect.data.Schema;
  import org.apache.kafka.connect.data.SchemaBuilder;
  import org.apache.kafka.connect.data.Struct;
  import org.apache.kafka.connect.transforms.util.SimpleConfig;
  
  import java.util.HashMap;
  import java.util.Map;
  
  public abstract class HoistField<R extends ConnectRecord<R>> implements Transformation<R>, Versioned {
  
      public static final String OVERVIEW_DOC =
              "Wrap data using the specified field name in a Struct when schema present, or a Map in the case of schemaless data."
                      + "<p/>Use the concrete transformation type designed for the record key (<code>" + Key.class.getName() + "</code>) "
                      + "or value (<code>" + Value.class.getName() + "</code>).";
  
      private static final String FIELD_CONFIG = "field";
  
      public static final ConfigDef CONFIG_DEF = new ConfigDef()
              .define(FIELD_CONFIG, ConfigDef.Type.STRING, ConfigDef.NO_DEFAULT_VALUE, ConfigDef.Importance.MEDIUM,
                      "Field name for the single field that will be created in the resulting Struct or Map.");
  
      private Cache<Schema, Schema> schemaUpdateCache;
  
      private String fieldName;
  
      @Override
      public void configure(Map<String, ?> props) {
          final SimpleConfig config = new SimpleConfig(CONFIG_DEF, props);
          fieldName = config.getString("field");
          schemaUpdateCache = new SynchronizedCache<>(new LRUCache<>(16));
      }
  
      @Override
      public R apply(R record) {
          final Schema schema = operatingSchema(record);
          final Object value = operatingValue(record);
  
          if (schema == null) {
              Map<String, Object> updatedValue = new HashMap<>();
              updatedValue.put(fieldName, value);
              return newRecord(record, null, updatedValue);
          } else {
              Schema updatedSchema = schemaUpdateCache.get(schema);
              if (updatedSchema == null) {
                  updatedSchema = SchemaBuilder.struct().field(fieldName, schema).build();
                  schemaUpdateCache.put(schema, updatedSchema);
              }
  
              final Struct updatedValue = new Struct(updatedSchema).put(fieldName, value);
  
              return newRecord(record, updatedSchema, updatedValue);
          }
      }
  
      @Override
      public String version() {
          return AppInfoParser.getVersion();
      }
  
      @Override
      public void close() {
          schemaUpdateCache = null;
      }
  
      @Override
      public ConfigDef config() {
          return CONFIG_DEF;
      }
  
      protected abstract Schema operatingSchema(R record);
  
      protected abstract Object operatingValue(R record);
  
      protected abstract R newRecord(R record, Schema updatedSchema, Object updatedValue);
  
      public static class Key<R extends ConnectRecord<R>> extends HoistField<R> {
          @Override
          protected Schema operatingSchema(R record) {
              return record.keySchema();
          }
  
          @Override
          protected Object operatingValue(R record) {
              return record.key();
          }
  
          @Override
          protected R newRecord(R record, Schema updatedSchema, Object updatedValue) {
              return record.newRecord(record.topic(), record.kafkaPartition(), updatedSchema, updatedValue, record.valueSchema(), record.value(), record.timestamp());
          }
      }
  
      public static class Value<R extends ConnectRecord<R>> extends HoistField<R> {
          @Override
          protected Schema operatingSchema(R record) {
              return record.valueSchema();
          }
  
          @Override
          protected Object operatingValue(R record) {
              return record.value();
          }
  
          @Override
          protected R newRecord(R record, Schema updatedSchema, Object updatedValue) {
              return record.newRecord(record.topic(), record.kafkaPartition(), record.keySchema(), record.key(), updatedSchema, updatedValue, record.timestamp());
          }
      }
  
  }
  