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.beam.runners.core;
  
  import org.apache.beam.sdk.state.TimeDomain;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Instant;
  
  /** An wrapper interface that represents the execution of a {@link DoFn}. */
  public interface DoFnRunner<InputT extends @Nullable Object, OutputT extends @Nullable Object> {
    /** Prepares and calls a {@link DoFn DoFn's} {@link DoFn.StartBundle @StartBundle} method. */
    void startBundle();
  
    /**
     * Calls a {@link DoFn DoFn's} {@link DoFn.ProcessElement @ProcessElement} method with a {@link
     * DoFn.ProcessContext} containing the provided element.
     */
    void processElement(WindowedValue<InputT> elem);
  
    /**
     * Calls a {@link DoFn DoFn's} {@link DoFn.OnTimer @OnTimer} method for the given timer in the
     * given window.
     */
    <KeyT extends @Nullable Object> void onTimer(
        String timerId,
        String timerFamilyId,
        KeyT key,
        BoundedWindow window,
        Instant timestamp,
        Instant outputTimestamp,
        TimeDomain timeDomain);
  
    /**
     * Calls a {@link DoFn DoFn's} {@link DoFn.FinishBundle @FinishBundle} method and performs
     * additional tasks, such as flushing in-memory states.
     */
    void finishBundle();
  
    /**
     * Calls a {@link DoFn DoFn's} {@link DoFn.OnWindowExpiration @OnWindowExpiration} method and
     * performs additional task, such as extracts a value saved in a state before garbage collection.
     */
    <KeyT extends @Nullable Object> void onWindowExpiration(
        BoundedWindow window, Instant timestamp, KeyT key);
  
    /**
     * @since 2.5.0
     * @return the underlying fn instance.
     */
    DoFn<InputT, OutputT> getFn();
  }
  