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   *  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
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   *    https://www.apache.org/licenses/LICENSE-2.0
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  package org.apache.cayenne.util;
  
  import java.util.Collection;
  
  import org.apache.cayenne.map.DataMap;
  import org.apache.cayenne.map.DeleteRule;
  import org.apache.cayenne.map.ObjAttribute;
  import org.apache.cayenne.map.ObjEntity;
  import org.apache.cayenne.map.ObjRelationship;
  
  /**
   * DeleteRuleUpdater is responsible for auto-setting delete rules for object relationships
   */
  public class DeleteRuleUpdater implements EntityMergeListener {
      /**
       * Singleton object to for defining EntityMergeListener instance
       */
      private static DeleteRuleUpdater instance;
      
      /**
       * Updates delete rules for all obj entities in a datamap
       */
      public static void updateDataMap(DataMap map) {
          Collection<ObjEntity> entities = map.getObjEntities();
          for (ObjEntity ent : entities) {
              updateObjEntity(ent);
          }
      }
      
      /**
       * Updates delete rules for all relationships in a objentity
       */
      public static void updateObjEntity(ObjEntity e) {
          Collection<ObjRelationship> rels = e.getRelationships();
          for (ObjRelationship rel : rels) {
              updateObjRelationship(rel);
          }
      }
      
      /**
       * Updates delete rules for specified relationship
       */
      public static void updateObjRelationship(ObjRelationship rel) {
          rel.setDeleteRule(rel.isToMany() ? DeleteRule.DEFAULT_DELETE_RULE_TO_MANY :
              DeleteRule.DEFAULT_DELETE_RULE_TO_ONE);
      }
  
      public void objAttributeAdded(ObjAttribute attr) {
      }
  
      public void objRelationshipAdded(ObjRelationship rel) {
          updateObjRelationship(rel);
      }
      
      /**
       * Returns EntityMergeListener instance, which can set delete rule at relationship change
       */
      public static EntityMergeListener getEntityMergeListener() {
          if (instance == null) {
              instance = new DeleteRuleUpdater();
          }
          
          return instance;
      }
  }
  