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.causeway.applib.services.iactnlayer;
  
  import java.util.Optional;
  
  import org.apache.causeway.applib.services.iactn.Interaction;
  import org.apache.causeway.applib.services.iactn.InteractionProvider;
  import org.apache.causeway.commons.internal.exceptions._Exceptions;
  
  /**
   * Provides access to the current {@link InteractionLayer}.
   *
   * <p>
   *     The bottom-most interaction &quot;layer&quot; can be thought of as a short-lived session with the database.
   *     A new layer can be started, for example using the {@link org.apache.causeway.applib.services.sudo.SudoService},
   *     or the {@link InteractionService}.  These allow the user (or the clock or other environmental aspects) to be
   *     temporarily altered - similar to a &quot;su&quot; command in Unix.
   * </p>
   *
   * @see Interaction
   * @see InteractionLayer
   * @see InteractionService
   * @see InteractionProvider
   * @see org.apache.causeway.applib.services.sudo.SudoService
   * @see org.apache.causeway.applib.services.clock.ClockService
   *
   * @since 2.0 {@index}
   */
  public interface InteractionLayerTracker
  extends InteractionProvider {
  
      /** @return the AuthenticationLayer that sits on top of the current
       * request- or test-scoped InteractionSession's stack*/
      Optional<InteractionLayer> currentInteractionLayer();
  
      default InteractionLayer currentInteractionLayerElseFail() {
          return currentInteractionLayer()
                  .orElseThrow(()->_Exceptions
                          .illegalState("No InteractionLayer available on current thread"));
      }
  
      // -- INTERACTION CONTEXT
  
      /**
       * Returns the {@link InteractionContext} wrapped by the {@link #currentInteractionLayer()}
       * (if within an {@link InteractionLayer}).
       */
      @Override
      default Optional<InteractionContext> currentInteractionContext() {
          return currentInteractionLayer()
                  .map(InteractionLayer::interactionContext);
      }
  
      // -- INTERACTION
  
      /**
       * Returns the {@link Interaction} wrapped by the {@link #currentInteractionLayer()}
       * (if within an {@link InteractionLayer}).
       */
      @Override
      default Optional<Interaction> currentInteraction(){
      	return currentInteractionLayer()
      	        .map(InteractionLayer::interaction);
      }
  
  }
  