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.metamodel.services.objectlifecycle;
  
  import java.util.Objects;
  
  import lombok.Getter;
  
  public final class PreAndPostValue {
  
      /**
       * The object that was referenced before this object was changed.
       *
       * @implNote this referenced object itself could end up being deleted in the course of the
       * transaction; in which case use
       * {@link #getPreString()} which is the eagerly cached <tt>toString</tt> of said object.
       */
      @Getter private final Object pre;
  
      /**
       * Eagerly calculated because it could be that the object referenced ends up being deleted
       * by the time that the transaction completes.
       */
      @Getter private final String preString;
  
      @Getter private final Object post;
      @Getter private final String postString;
  
      public static PreAndPostValue pre(final Object preValue) {
          return new PreAndPostValue(preValue);
      }
  
      private PreAndPostValue(final Object pre) {
          this.pre = pre;
          this.preString = asString(pre);
          this.post = null;
          this.postString = null;
      }
  
      private PreAndPostValue(final PreAndPostValue pre, final Object post) {
          this.pre = pre.getPre();
          this.preString = pre.getPreString();
          this.post = post;
          this.postString = asString(post);
      }
  
      public PreAndPostValue withPost(final Object post) {
          return new PreAndPostValue(this, post);
      }
  
      @Override
      public String toString() {
          return getPre() + " -> " + getPost();
      }
  
      public boolean shouldPublish() {
          // don't audit objects that were created and then immediately deleted within the same xactn
          if (getPre() == PropertyValuePlaceholder.NEW
                  && getPost() == PropertyValuePlaceholder.DELETED) {
              return false;
          }
          // but do always audit objects that have just been created or deleted
          if (getPre() == PropertyValuePlaceholder.NEW
                  || getPost() == PropertyValuePlaceholder.DELETED) {
              return true;
          }
          // else - for updated objects - audit only if the property value has changed
          return !Objects.equals(getPre(), getPost());
      }
  
      // -- HELPER
  
      private static String asString(final Object object) {
          return object != null
                  ? object.toString()
                  : null;
      }
  
  }
  