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 static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkNotNull;
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkState;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * A wrapper around a trigger used during execution. While an actual trigger may appear multiple
   * times (both in the same trigger expression and in other trigger expressions), the {@code
   * ExecutableTrigger} wrapped around them forms a tree (only one occurrence).
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class ExecutableTriggerStateMachine implements Serializable {
  
    /** Store the index assigned to this trigger. */
    private final int triggerIndex;
  
    private final int firstIndexAfterSubtree;
    private final List<ExecutableTriggerStateMachine> subTriggers = new ArrayList<>();
    private final TriggerStateMachine trigger;
  
    public static ExecutableTriggerStateMachine create(TriggerStateMachine trigger) {
      return create(trigger, 0);
    }
  
    private static ExecutableTriggerStateMachine create(
        TriggerStateMachine trigger, int nextUnusedIndex) {
  
      return new ExecutableTriggerStateMachine(trigger, nextUnusedIndex);
    }
  
    public static ExecutableTriggerStateMachine createForOnceTrigger(
        TriggerStateMachine trigger, int nextUnusedIndex) {
      return new ExecutableTriggerStateMachine(trigger, nextUnusedIndex);
    }
  
    private ExecutableTriggerStateMachine(TriggerStateMachine trigger, int nextUnusedIndex) {
      this.trigger = checkNotNull(trigger, "trigger must not be null");
      this.triggerIndex = nextUnusedIndex++;
  
      if (trigger.subTriggers() != null) {
        for (TriggerStateMachine subTrigger : trigger.subTriggers()) {
          ExecutableTriggerStateMachine subExecutable = create(subTrigger, nextUnusedIndex);
          subTriggers.add(subExecutable);
          nextUnusedIndex = subExecutable.firstIndexAfterSubtree;
        }
      }
      firstIndexAfterSubtree = nextUnusedIndex;
    }
  
    public List<ExecutableTriggerStateMachine> subTriggers() {
      return subTriggers;
    }
  
    @Override
    public String toString() {
      return trigger.toString();
    }
  
    /**
     * Return the underlying trigger specification corresponding to this {@code ExecutableTrigger}.
     */
    public TriggerStateMachine getSpec() {
      return trigger;
    }
  
    public int getTriggerIndex() {
      return triggerIndex;
    }
  
    public final int getFirstIndexAfterSubtree() {
      return firstIndexAfterSubtree;
    }
  
    public boolean isCompatible(ExecutableTriggerStateMachine other) {
      return trigger.isCompatible(other.trigger);
    }
  
    public ExecutableTriggerStateMachine getSubTriggerContaining(int index) {
      checkNotNull(subTriggers);
      checkState(
          index > triggerIndex && index < firstIndexAfterSubtree,
          "Cannot find sub-trigger containing index not in this tree.");
      ExecutableTriggerStateMachine previous = null;
      for (ExecutableTriggerStateMachine subTrigger : subTriggers) {
        if (index < subTrigger.triggerIndex) {
          return previous;
        }
        previous = subTrigger;
      }
      return previous;
    }
  
    public void invokePrefetchOnElement(TriggerStateMachine.PrefetchContext c) {
      trigger.prefetchOnElement(c.forTrigger(this));
    }
  
    /**
     * Invoke the {@link TriggerStateMachine#onElement} method for this trigger, ensuring that the
     * bits are properly updated if the trigger finishes.
     */
    public void invokeOnElement(TriggerStateMachine.OnElementContext c) throws Exception {
      trigger.onElement(c.forTrigger(this));
    }
  
    public void invokePrefetchOnMerge(TriggerStateMachine.MergingPrefetchContext c) {
      trigger.prefetchOnMerge(c.forTrigger(this));
    }
  
    /**
     * Invoke the {@link TriggerStateMachine#onMerge} method for this trigger, ensuring that the bits
     * are properly updated.
     */
    public void invokeOnMerge(TriggerStateMachine.OnMergeContext c) throws Exception {
      TriggerStateMachine.OnMergeContext subContext = c.forTrigger(this);
      trigger.onMerge(subContext);
    }
  
    public void invokePrefetchShouldFire(TriggerStateMachine.PrefetchContext c) {
      trigger.prefetchShouldFire(c.forTrigger(this));
    }
  
    public boolean invokeShouldFire(TriggerStateMachine.TriggerContext c) throws Exception {
      return trigger.shouldFire(c.forTrigger(this));
    }
  
    public void invokeOnFire(TriggerStateMachine.TriggerContext c) throws Exception {
      trigger.onFire(c.forTrigger(this));
    }
  
    /** Invoke clear for the current this trigger. */
    public void invokeClear(TriggerStateMachine.TriggerContext c) throws Exception {
      trigger.clear(c.forTrigger(this));
    }
  }
  