/*
* Copyright (c) 2002-2010 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.graphdb;
/**
* A client hook for evaluating whether the traverser should traverse beyond a
* specific node. This is used for pruning the traversal.
* <p>
* When a traverser is created, the client parameterizes it with a
* StopEvaluator. The traverser then invokes the {@link #isStopNode
* isStopNode()} operation just before traversing the relationships of a node,
* allowing the client to either approve or disapprove of traversing beyond that
* node.
* <p>
* When implementing a StopEvaluator, the client investigates the information
* encapsulated in a {@link TraversalPosition} to decide whether to block
* traversal beyond a node or not. For example, here's a snippet detailing a
* StopEvaluator that blocks traversal beyond a node if it has a certain
* property value:
*
* <pre>
* <code>
* StopEvaluator stopEvaluator = new StopEvaluator()
* {
* // Block traversal if the node has a property with key 'key' and value
* // 'someValue'
* public boolean {@link #isStopNode(TraversalPosition) isStopNode}( {@link TraversalPosition} position )
* {
* if ( position.{@link TraversalPosition#isStartNode() isStartNode}() )
* {
* return false;
* }
* {@link Node} node = position.{@link TraversalPosition#currentNode() currentNode}();
* Object someProp = node.{@link Node#getProperty(String, Object) getProperty}( "key", null );
* return someProp instanceof String &&
* ((String) someProp).equals( "someValue" );
* }
* };
* </code>
* </pre>
*/
/*
* @deprecated because of the introduction of a new traversal framework,
* see more information at {@link TraversalDescription} and
* {@link Traversal} and the new traversal framework's equivalent
* {@link PruneEvaluator}.
*/
// @Deprecated
public interface StopEvaluator
{
/**
* Traverse until the end of the graph. This evaluator returns
* <code>false</code> all the time.
*/
public static final StopEvaluator END_OF_GRAPH = new StopEvaluator()
{
public boolean isStopNode( final TraversalPosition currentPosition )
{
return false;
}
};
/**
* Traverses to depth 1.
*/
public static final StopEvaluator DEPTH_ONE = new StopEvaluator()
{
public boolean isStopNode( final TraversalPosition currentPosition )
{
return currentPosition.depth() >= 1;
}
};
/**
* Method invoked by traverser to see if current position is a stop node.
*
* @param currentPos the traversal position
* @return True if current position is a stop node
*/
public boolean isStopNode( TraversalPosition currentPos );
}