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.triggers;
  
  import org.apache.beam.sdk.state.TimeDomain;
  
  /**
   * A trigger that is equivalent to {@code Repeatedly.forever(AfterWatermark.pastEndOfWindow())}. See
   * {@link RepeatedlyStateMachine#forever} and {@link AfterWatermarkStateMachine#pastEndOfWindow} for
   * more details.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class DefaultTriggerStateMachine extends TriggerStateMachine {
  
    private DefaultTriggerStateMachine() {
      super(null);
    }
  
    /** Returns the default trigger. */
    public static DefaultTriggerStateMachine of() {
      return new DefaultTriggerStateMachine();
    }
  
    @Override
    public void prefetchOnElement(PrefetchContext c) {}
  
    @Override
    public void onElement(OnElementContext c) throws Exception {
      // If the end of the window has already been reached, then we are already ready to fire
      // and do not need to set a wake-up timer.
      if (!endOfWindowReached(c)) {
        c.setTimer(c.window().maxTimestamp(), TimeDomain.EVENT_TIME);
      }
    }
  
    @Override
    public void prefetchOnMerge(MergingPrefetchContext c) {}
  
    @Override
    public void onMerge(OnMergeContext c) throws Exception {
      // If the end of the window has already been reached, then we are already ready to fire
      // and do not need to set a wake-up timer.
      if (!endOfWindowReached(c)) {
        c.setTimer(c.window().maxTimestamp(), TimeDomain.EVENT_TIME);
      }
    }
  
    @Override
    public void prefetchShouldFire(PrefetchContext c) {}
  
    @Override
    public void clear(TriggerContext c) throws Exception {}
  
    @Override
    public boolean isCompatible(TriggerStateMachine other) {
      // Semantically, all default triggers are identical
      return other instanceof DefaultTriggerStateMachine;
    }
  
    @Override
    public boolean shouldFire(TriggerStateMachine.TriggerContext context) throws Exception {
      return endOfWindowReached(context);
    }
  
    private boolean endOfWindowReached(TriggerStateMachine.TriggerContext context) {
      return context.currentEventTime() != null
          && context.currentEventTime().isAfter(context.window().maxTimestamp());
    }
  
    @Override
    public void onFire(TriggerStateMachine.TriggerContext context) throws Exception {}
  }
  