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 com.alibaba.jstorm.window;
  
  /**
   * Result type for trigger methods. This determines what happens with the window,
   * for example whether the window function should be called, or the window
   * should be discarded.
   */
  public enum TriggerResult {
  
      /**
       * No action is taken on the window.
       */
      CONTINUE(false, false),
  
      /**
       * {@code FIRE_AND_PURGE} evaluates the window function and emits the window
       * result.
       */
      FIRE_AND_PURGE(true, true),
  
      /**
       * On {@code FIRE}, the window is evaluated and results are emitted.
       * The window is not purged, though, all elements are retained.
       */
      FIRE(true, false),
  
      /**
       * All elements in the window are cleared and the window is discarded,
       * without evaluating the window function or emitting any elements.
       */
      PURGE(false, true);
  
      // ------------------------------------------------------------------------
  
      private final boolean fire;
      private final boolean purge;
  
      TriggerResult(boolean fire, boolean purge) {
          this.purge = purge;
          this.fire = fire;
      }
  
      public boolean isFire() {
          return fire;
      }
  
      public boolean isPurge() {
          return purge;
      }
  
      // ------------------------------------------------------------------------
  
      /**
       * Merges two {@code TriggerResults}. This specifies what should happen if we have
       * two results from a Trigger, for example as a result from
       * {@link Trigger#onElement(Object, long, TimeWindow, Trigger.TriggerContext)} and
       * {@link Trigger#onEventTime(long, TimeWindow, Trigger.TriggerContext)}.
       *
       * <p>
       * For example, if one result says {@code CONTINUE} while the other says {@code FIRE}
       * then {@code FIRE} is the combined result;
       */
      public static TriggerResult merge(TriggerResult a, TriggerResult b) {
          if (a.purge || b.purge) {
              if (a.fire || b.fire) {
                  return FIRE_AND_PURGE;
              } else {
                  return PURGE;
              }
          } else if (a.fire || b.fire) {
              return FIRE;
          } else {
              return CONTINUE;
          }
      }
  }
  