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.api;
  
  import accord.local.Command;
  import accord.local.Node;
  import accord.local.SafeCommand;
  import accord.local.SafeCommandStore;
  import accord.primitives.SaveStatus;
  import accord.primitives.Status.Durability.HasDecisionOrOutcome;
  import accord.primitives.TxnId;
  
  /**
   * A collection of remote listeners awaiting some set of local responses from command stores.
   * Registrations here are permanent (don't time out) and one shot; if the reply is lost the remote listener will need to be re-registered.
   * Remote listeners may periodically poll to check the listeners are still registered.
   */
  public interface RemoteListeners
  {
      interface Factory
      {
          RemoteListeners create(Node node);
      }
  
      /**
       * An in-progress registration that collects command stores it is waiting on.
       * This may be cancelled until done() is invoked, at which point the registration is permanent.
       */
      interface Registration
      {
          // thread safe
          void add(SafeCommandStore safeStore, SafeCommand safeCommand);
  
          // thread unsafe
          int done();
      }
  
      /**
       * CallbackId must be a non-negative integer
       */
      Registration register(TxnId txnId, SaveStatus awaitSaveStatus, HasDecisionOrOutcome awaitDurability, Node.Id listener, int callbackId);
      void notify(SafeCommandStore safeStore, SafeCommand safeCommand, Command prev);
  
      class NoOpRemoteListeners implements RemoteListeners
      {
          static class NoOpRegistration implements Registration
          {
              @Override public void add(SafeCommandStore safeStore, SafeCommand safeCommand) {}
              @Override public int done() { return 0; }
          }
  
          @Override public Registration register(TxnId txnId, SaveStatus awaitSaveStatus, HasDecisionOrOutcome awaitDurability, Node.Id listener, int callbackId) { return new NoOpRegistration();}
          @Override public void notify(SafeCommandStore safeStore, SafeCommand safeCommand, Command prev) {}
      }
  }
  