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 accord.impl.basic;
  
  import accord.utils.Invariants;
  
  public interface Pending
  {
      Pending origin();
  
      // a slightly hacky but easy way to track transitive recurring tasks
      class Global
      {
          public static final Pending NONE = () -> null;
          private static Pending activeOrigin;
  
          public static void setActiveOrigin(Pending newActive)
          {
              Invariants.require(activeOrigin == null);
              activeOrigin = newActive.origin();
              Invariants.require(activeOrigin != null);
          }
  
          public static void unsafeSetActiveOrigin(Pending newActiveOrigin)
          {
              activeOrigin = newActiveOrigin;
          }
  
          public static void clearActiveOrigin()
          {
              activeOrigin = null;
          }
  
          public static void setNoActiveOrigin()
          {
              activeOrigin = NONE;
          }
  
          public static Pending activeOrigin()
          {
              return Invariants.nonNull(activeOrigin);
          }
      }
  }
  