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 java.util.Arrays;
  
  /**
   * Repeat a trigger, either until some condition is met or forever.
   *
   * <p>For example, to fire after the end of the window, and every time late data arrives:
   *
   * <pre>{@code
   * Repeatedly.forever(AfterWatermark.isPastEndOfWindow());
   * }</pre>
   *
   * <p>{@code Repeatedly.forever(someTrigger)} behaves like an infinite {@code
   * AfterEach.inOrder(someTrigger, someTrigger, someTrigger, ...)}.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class RepeatedlyStateMachine extends TriggerStateMachine {
  
    private static final int REPEATED = 0;
  
    /**
     * Create a composite trigger that repeatedly executes the trigger {@code repeated}, firing each
     * time it fires and ignoring any indications to finish.
     *
     * <p>Unless used with {@link TriggerStateMachine#orFinally} the composite trigger will never
     * finish.
     *
     * @param repeated the trigger to execute repeatedly.
     */
    public static RepeatedlyStateMachine forever(TriggerStateMachine repeated) {
      return new RepeatedlyStateMachine(repeated);
    }
  
    private RepeatedlyStateMachine(TriggerStateMachine repeated) {
      super(Arrays.asList(repeated));
    }
  
    @Override
    public void prefetchOnElement(PrefetchContext c) {
      getRepeated(c).invokePrefetchOnElement(c);
    }
  
    @Override
    public void onElement(OnElementContext c) throws Exception {
      getRepeated(c).invokeOnElement(c);
    }
  
    @Override
    public void prefetchOnMerge(MergingPrefetchContext c) {
      getRepeated(c).invokePrefetchOnMerge(c);
    }
  
    @Override
    public void onMerge(OnMergeContext c) throws Exception {
      getRepeated(c).invokeOnMerge(c);
    }
  
    @Override
    public void prefetchShouldFire(PrefetchContext c) {
      getRepeated(c).invokePrefetchShouldFire(c);
    }
  
    @Override
    public boolean shouldFire(TriggerStateMachine.TriggerContext context) throws Exception {
      return getRepeated(context).invokeShouldFire(context);
    }
  
    @Override
    public void onFire(TriggerContext context) throws Exception {
      getRepeated(context).invokeOnFire(context);
  
      if (context.trigger().isFinished(REPEATED)) {
        // Reset tree will recursively clear the finished bits, and invoke clear.
        context.forTrigger(getRepeated(context)).trigger().resetTree();
      }
    }
  
    @Override
    public String toString() {
      return String.format("Repeatedly.forever(%s)", subTriggers.get(REPEATED));
    }
  
    private ExecutableTriggerStateMachine getRepeated(TriggerContext context) {
      return context.trigger().subTrigger(REPEATED);
    }
  
    private ExecutableTriggerStateMachine getRepeated(PrefetchContext context) {
      return context.trigger().subTriggers().get(REPEATED);
    }
  }
  