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.core.runtimeservices.publish;
  
  import java.util.List;
  import java.util.Optional;
  
  import jakarta.annotation.PostConstruct;
  import jakarta.annotation.Priority;
  import jakarta.inject.Inject;
  import jakarta.inject.Named;
  
  import org.springframework.beans.factory.annotation.Qualifier;
  import org.jspecify.annotations.Nullable;
  import org.springframework.stereotype.Service;
  
  import org.apache.causeway.applib.annotation.PriorityPrecedence;
  import org.apache.causeway.applib.services.clock.ClockService;
  import org.apache.causeway.applib.services.iactnlayer.InteractionLayerTracker;
  import org.apache.causeway.applib.services.publishing.spi.EntityChanges;
  import org.apache.causeway.applib.services.publishing.spi.EntityChangesSubscriber;
  import org.apache.causeway.applib.services.user.UserService;
  import org.apache.causeway.commons.collections.Can;
  import org.apache.causeway.commons.having.HasEnabling;
  import org.apache.causeway.core.runtimeservices.CausewayModuleCoreRuntimeServices;
  import org.apache.causeway.core.transaction.changetracking.EntityChangesPublisher;
  import org.apache.causeway.core.transaction.changetracking.HasEnlistedEntityChanges;
  
  import org.jspecify.annotations.NonNull;
  import lombok.RequiredArgsConstructor;
  
  /**
   * Default implementation of {@link EntityChangesPublisher}
   *
   * @since 2.0 {@index}
   */
  @Service
  @Named(CausewayModuleCoreRuntimeServices.NAMESPACE + ".EntityChangesPublisherDefault")
  @Priority(PriorityPrecedence.EARLY)
  @Qualifier("Default")
  @RequiredArgsConstructor(onConstructor_ = {@Inject})
  public class EntityChangesPublisherDefault implements EntityChangesPublisher {
  
      private final List<EntityChangesSubscriber> subscribers;
      private final ClockService clockService;
      private final UserService userService;
      private final InteractionLayerTracker iaTracker;
  
      private Can<EntityChangesSubscriber> enabledSubscribers = Can.empty();
  
      @PostConstruct
      public void init() {
          enabledSubscribers = Can.ofCollection(subscribers)
                  .filter(HasEnabling::isEnabled);
      }
  
      @Override
      public void publishChangingEntities(HasEnlistedEntityChanges hasEnlistedEntityChanges) {
  
          var payload = getPayload(hasEnlistedEntityChanges);
          var handle = _Xray.enterEntityChangesPublishing(
                  iaTracker,
                  payload,
                  enabledSubscribers,
                  ()->getCannotPublishReason(payload));
  
          payload.ifPresent(entityChanges->{
              for (var subscriber : enabledSubscribers) {
                  subscriber.onChanging(entityChanges);
              }
          });
  
          _Xray.exitPublishing(handle);
      }
  
      // -- HELPER
  
      private Optional<EntityChanges> getPayload(final @NonNull HasEnlistedEntityChanges hasEnlistedEntityChanges) {
          if (enabledSubscribers.isEmpty()) {
              return Optional.empty();
          }
  
          return hasEnlistedEntityChanges.getEntityChanges(
                  clockService.getClock().nowAsJavaSqlTimestamp(), // current time
                  userService.currentUserNameElseNobody()          // current user
          );
      }
  
      // x-ray support
      private @Nullable String getCannotPublishReason(final @NonNull Optional<EntityChanges> payload) {
          return enabledSubscribers.isEmpty()
                  ? "no subscribers"
                  : !payload.isPresent()
                          ? "no changes had been enlisted"
                          : null;
      }
  
  }
  