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 java.util.Collection;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.PaneInfo;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.apache.beam.sdk.values.TupleTag;
  import org.joda.time.Instant;
  
  /**
   * Interface that may be required by some (internal) {@link DoFn}s to implement windowing. It should
   * not be necessary for general user code to interact with this at all.
   *
   * <p>This interface should be provided by runner implementors to support windowing on their runner.
   *
   * @param <InputT> input type
   * @param <OutputT> output type
   */
  public interface WindowingInternals<InputT, OutputT> {
  
    /**
     * Unsupported state internals. The key type is unknown. It is up to the user to use the correct
     * type of key.
     */
    StateInternals stateInternals();
  
    /** Output the value at the specified timestamp in the listed windows. */
    void outputWindowedValue(
        OutputT output,
        Instant timestamp,
        Collection<? extends BoundedWindow> windows,
        PaneInfo paneInfo);
  
    /** Output the value to a tagged output at the specified timestamp in the listed windows. */
    <AdditionalOutputT> void outputWindowedValue(
        TupleTag<AdditionalOutputT> tag,
        AdditionalOutputT output,
        Instant timestamp,
        Collection<? extends BoundedWindow> windows,
        PaneInfo paneInfo);
  
    /**
     * Return the timer manager provided by the underlying system, or null if Timers need to be
     * emulated.
     */
    TimerInternals timerInternals();
  
    /** Access the windows the element is being processed in without "exploding" it. */
    Collection<? extends BoundedWindow> windows();
  
    /** Access the pane of the current window(s). */
    PaneInfo paneInfo();
  
    /** Return the value of the side input for a particular side input window. */
    <T> T sideInput(PCollectionView<T> view, BoundedWindow sideInputWindow);
  }
  