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  package org.apache.cayenne.commitlog;
  
  import org.apache.cayenne.ObjectId;
  import org.apache.cayenne.graph.ArcId;
  import org.apache.cayenne.graph.GraphChangeHandler;
  import org.apache.cayenne.commitlog.model.MutableChangeMap;
  import org.apache.cayenne.commitlog.model.MutableObjectChange;
  import org.apache.cayenne.commitlog.model.ObjectChangeType;
  import org.apache.cayenne.map.EntityResolver;
  import org.apache.cayenne.map.ObjEntity;
  import org.apache.cayenne.map.ObjRelationship;
  
  /**
   * Records changes in a given transaction to a {@link MutableChangeMap} object.
   * 
   * @since 4.0
   */
  class DiffProcessor implements GraphChangeHandler {
  
  	private EntityResolver entityResolver;
  	private MutableChangeMap changeSet;
  
  	DiffProcessor(MutableChangeMap changeSet, EntityResolver entityResolver) {
  		this.changeSet = changeSet;
  		this.entityResolver = entityResolver;
  	}
  
  	@Override
  	public void nodeRemoved(Object nodeId) {
  		// do nothing... deletes are processed pre-commit
  	}
  
  	@Override
  	public void nodePropertyChanged(Object nodeId, String property, Object oldValue, Object newValue) {
  		changeSet.getOrCreate((ObjectId) nodeId, ObjectChangeType.UPDATE).attributeChanged(property, oldValue,
  				newValue);
  	}
  
  	@Override
  	public void nodeIdChanged(Object nodeId, Object newId) {
  		changeSet.aliasId((ObjectId) nodeId, (ObjectId) newId);
  	}
  
  	@Override
  	public void nodeCreated(Object nodeId) {
  		changeSet.getOrCreate((ObjectId) nodeId, ObjectChangeType.INSERT);
  	}
  
  	@Override
  	public void arcDeleted(Object nodeId, Object targetNodeId, ArcId arcId) {
  		ObjectId id = (ObjectId) nodeId;
  		String relationshipName = arcId.toString();
  
  		ObjEntity entity = entityResolver.getObjEntity(id.getEntityName());
  		ObjRelationship relationship = entity.getRelationship(relationshipName);
  
  		MutableObjectChange c = changeSet.getOrCreate(id, ObjectChangeType.UPDATE);
  
  		ObjectId tid = (ObjectId) targetNodeId;
  
  		if (relationship.isToMany()) {
  			c.toManyRelationshipDisconnected(relationshipName, tid);
  		} else {
  			c.toOneRelationshipDisconnected(relationshipName, tid);
  		}
  	}
  
  	@Override
  	public void arcCreated(Object nodeId, Object targetNodeId, ArcId arcId) {
  
  		ObjectId id = (ObjectId) nodeId;
  		String relationshipName = arcId.toString();
  
  		ObjEntity entity = entityResolver.getObjEntity(id.getEntityName());
  		ObjRelationship relationship = entity.getRelationship(relationshipName);
  
  		MutableObjectChange c = changeSet.getOrCreate(id, ObjectChangeType.UPDATE);
  
  		ObjectId tid = (ObjectId) targetNodeId;
  
  		if (relationship.isToMany()) {
  			c.toManyRelationshipConnected(relationshipName, tid);
  		} else {
  			c.toOneRelationshipConnected(relationshipName, tid);
  		}
  	}
  }
  