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.streams.processor.api;
  
  import org.apache.kafka.streams.processor.PunctuationType;
  import org.apache.kafka.streams.processor.Punctuator;
  import org.apache.kafka.streams.processor.StateStore;
  
  import java.time.Duration;
  
  /**
   * A processor of key-value pair records.
   *
   * @param <KIn> the type of input keys
   * @param <VIn> the type of input values
   * @param <KOut> the type of output keys
   * @param <VOut> the type of output values
   */
  @FunctionalInterface
  public interface Processor<KIn, VIn, KOut, VOut> {
  
      /**
       * Initialize this processor with the given context. The framework ensures this is called once per processor when the topology
       * that contains it is initialized. When the framework is done with the processor, {@link #close()} will be called on it; the
       * framework may later re-use the processor by calling {@code #init()} again.
       * <p>
       * The provided {@link ProcessorContext context} can be used to access topology and record meta data, to
       * {@link ProcessorContext#schedule(Duration, PunctuationType, Punctuator) schedule} a method to be
       * {@link Punctuator#punctuate(long) called periodically} and to access attached {@link StateStore}s.
       *
       * @param context the context; may not be null
       */
      default void init(final ProcessorContext<KOut, VOut> context) {}
  
      /**
       * Process the record. Note that record metadata is undefined in cases such as a forward call from a punctuator.
       *
       * @param record the record to process
       */
      void process(Record<KIn, VIn> record);
  
      /**
       * Close this processor and clean up any resources. Be aware that {@code #close()} is called after an internal cleanup.
       * Thus, it is not possible to write anything to Kafka as underlying clients are already closed. The framework may
       * later re-use this processor by calling {@code #init()} on it again.
       * <p>
       * Note: Do not close any streams managed resources, like {@link StateStore}s here, as they are managed by the library.
       */
      default void close() {}
  }
  