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.config.ConfigException;
  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.ConnectSchema;
  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.util.SimpleConfig;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Map;
  
  import static org.apache.kafka.connect.transforms.util.Requirements.requireSchema;
  
  public abstract class SetSchemaMetadata<R extends ConnectRecord<R>> implements Transformation<R>, Versioned {
      private static final Logger log = LoggerFactory.getLogger(SetSchemaMetadata.class);
  
      public static final String OVERVIEW_DOC =
              "Set the schema name, version or both on the record's key (<code>" + Key.class.getName() + "</code>)"
                      + " or value (<code>" + Value.class.getName() + "</code>) schema.";
  
      private interface ConfigName {
          String SCHEMA_NAME = "schema.name";
          String SCHEMA_VERSION = "schema.version";
          String REPLACE_NULL_WITH_DEFAULT = "replace.null.with.default";
      }
  
      public static final ConfigDef CONFIG_DEF = new ConfigDef()
              .define(ConfigName.SCHEMA_NAME, ConfigDef.Type.STRING, null, ConfigDef.Importance.HIGH, "Schema name to set.")
              .define(ConfigName.SCHEMA_VERSION, ConfigDef.Type.INT, null, ConfigDef.Importance.HIGH, "Schema version to set.")
              .define(ConfigName.REPLACE_NULL_WITH_DEFAULT, 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 String schemaName;
      private Integer schemaVersion;
      private boolean replaceNullWithDefault;
  
      @Override
      public String version() {
          return AppInfoParser.getVersion();
      }
  
      @Override
      public void configure(Map<String, ?> configs) {
          final SimpleConfig config = new SimpleConfig(CONFIG_DEF, configs);
          schemaName = config.getString(ConfigName.SCHEMA_NAME);
          schemaVersion = config.getInt(ConfigName.SCHEMA_VERSION);
          replaceNullWithDefault = config.getBoolean(ConfigName.REPLACE_NULL_WITH_DEFAULT);
  
          if (schemaName == null && schemaVersion == null) {
              throw new ConfigException("Neither schema name nor version configured");
          }
      }
  
      @Override
      public R apply(R record) {
          final Object value = operatingValue(record);
          final Schema schema = operatingSchema(record);
          if (value == null && schema == null) {
              return record;
          }
          requireSchema(schema, "updating schema metadata");
          final boolean isArray = schema.type() == Schema.Type.ARRAY;
          final boolean isMap = schema.type() == Schema.Type.MAP;
          final Schema updatedSchema = new ConnectSchema(
                  schema.type(),
                  schema.isOptional(),
                  schema.defaultValue(),
                  schemaName != null ? schemaName : schema.name(),
                  schemaVersion != null ? schemaVersion : schema.version(),
                  schema.doc(),
                  schema.parameters(),
                  schema.fields(),
                  isMap ? schema.keySchema() : null,
                  isMap || isArray ? schema.valueSchema() : null
          );
          log.trace("Applying SetSchemaMetadata SMT. Original schema: {}, updated schema: {}",
              schema, updatedSchema);
          return newRecord(record, updatedSchema);
      }
  
      private Object getFieldValue(Struct value, Field field) {
          if (replaceNullWithDefault) {
              return value.get(field);
          }
          return value.getWithoutDefault(field.name());
      }
  
      @Override
      public ConfigDef config() {
          return CONFIG_DEF;
      }
  
      @Override
      public void close() {
      }
  
      protected abstract Schema operatingSchema(R record);
  
      protected abstract Object operatingValue(R record);
  
      protected abstract R newRecord(R record, Schema updatedSchema);
  
      /**
       * Set the schema name, version or both on the record's key schema.
       */
      public static class Key<R extends ConnectRecord<R>> extends SetSchemaMetadata<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 updatedKey = updateSchemaIn(record.key(), updatedSchema);
              return record.newRecord(record.topic(), record.kafkaPartition(), updatedSchema, updatedKey, record.valueSchema(), record.value(), record.timestamp());
          }
      }
  
      /**
       * Set the schema name, version or both on the record's value schema.
       */
      public static class Value<R extends ConnectRecord<R>> extends SetSchemaMetadata<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 = updateSchemaIn(record.value(), updatedSchema);
              return record.newRecord(record.topic(), record.kafkaPartition(), record.keySchema(), record.key(), updatedSchema, updatedValue, record.timestamp());
          }
      }
  
      /**
       * Utility to check the supplied key or value for references to the old Schema,
       * and if so to return an updated key or value object that references the new Schema.
       * Note that this method assumes that the new Schema may have a different name and/or version,
       * but has fields that exactly match those of the old Schema.
       * <p>
       * Currently only {@link Struct} objects have references to the {@link Schema}.
       *
       * @param keyOrValue    the key or value object; may be null
       * @param updatedSchema the updated schema that has been potentially renamed
       * @return the original key or value object if it does not reference the old schema, or
       * a copy of the key or value object with updated references to the new schema.
       */
      protected Object updateSchemaIn(Object keyOrValue, Schema updatedSchema) {
          if (keyOrValue instanceof Struct origStruct) {
              Struct newStruct = new Struct(updatedSchema);
              for (Field field : updatedSchema.fields()) {
                  // assume both schemas have exact same fields with same names and schemas ...
                  newStruct.put(field, getFieldValue(origStruct, field));
              }
              return newStruct;
          }
          return keyOrValue;
      }
  }
  