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.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.Field;
  import org.apache.kafka.connect.data.Schema;
  import org.apache.kafka.connect.data.Struct;
  import org.apache.kafka.connect.transforms.field.FieldSyntaxVersion;
  import org.apache.kafka.connect.transforms.field.SingleFieldPath;
  import org.apache.kafka.connect.transforms.util.SimpleConfig;
  
  import java.util.Map;
  
  import static org.apache.kafka.connect.transforms.util.Requirements.requireMapOrNull;
  import static org.apache.kafka.connect.transforms.util.Requirements.requireStructOrNull;
  
  public abstract class ExtractField<R extends ConnectRecord<R>> implements Transformation<R>, Versioned {
  
      public static final String OVERVIEW_DOC =
              "Extract the specified field from a Struct when schema present, or a Map in the case of schemaless data. "
                      + "Any null values are passed through unmodified."
                      + "<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";
      private static final String REPLACE_NULL_WITH_DEFAULT_CONFIG = "replace.null.with.default";
  
      public static final ConfigDef CONFIG_DEF = FieldSyntaxVersion.appendConfigTo(
              new ConfigDef()
                      .define(
                              FIELD_CONFIG,
                              ConfigDef.Type.STRING,
                              ConfigDef.NO_DEFAULT_VALUE,
                              ConfigDef.Importance.MEDIUM,
                              "Field name to extract."
                      )
                      .define(REPLACE_NULL_WITH_DEFAULT_CONFIG,
                              ConfigDef.Type.BOOLEAN,
                              true,
                              ConfigDef.Importance.MEDIUM,
                              "Whether to replace fields that have a default value and that are null to the default value. When set to true, the default value is used, otherwise null is used."));
  
      private static final String PURPOSE = "field extraction";
  
      private SingleFieldPath fieldPath;
      private String originalPath;
      private boolean replaceNullWithDefault;
  
      @Override
      public String version() {
          return AppInfoParser.getVersion();
      }
  
      @Override
      public void configure(Map<String, ?> props) {
          final SimpleConfig config = new SimpleConfig(CONFIG_DEF, props);
          originalPath = config.getString(FIELD_CONFIG);
          fieldPath = new SingleFieldPath(originalPath, FieldSyntaxVersion.fromConfig(config));
          replaceNullWithDefault = config.getBoolean(REPLACE_NULL_WITH_DEFAULT_CONFIG);
      }
  
      @Override
      public R apply(R record) {
          final Schema schema = operatingSchema(record);
          if (schema == null) {
              final Map<String, Object> value = requireMapOrNull(operatingValue(record), PURPOSE);
              return newRecord(record, null, value == null ? null : fieldPath.valueFrom(value));
          } else {
              final Struct value = requireStructOrNull(operatingValue(record), PURPOSE);
              Field field = fieldPath.fieldFrom(schema);
  
              if (field == null) {
                  throw new IllegalArgumentException("Unknown field: " + originalPath);
              }
  
              return newRecord(record, field.schema(), value == null ? null : fieldPath.valueFrom(value, replaceNullWithDefault));
          }
      }
  
      @Override
      public void close() {
      }
  
      @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 ExtractField<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 ExtractField<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());
          }
      }
  
  }
  