/*
* Copyright (c) 2002-2009 "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;
/**
* Encapsulates information about the current traversal position.
*/
public interface TraversalPosition
{
/**
* Return the current node.
*
* @return The current node
*/
public Node currentNode();
/**
* Returns the previous node, may be null.
*
* @return The previous node
*/
// null if start node
public Node previousNode();
/**
* Return the last relationship traversed, may be null.
*
* @return The last relationship traversed
*/
// null if start node
public Relationship lastRelationshipTraversed();
/**
* Returns the current traversal depth.
*
* @return The current traversal depth
*/
public int depth();
/**
* Returns the number of nodes returned by traverser so far.
*
* @return The number of returned nodes.
*/
public int returnedNodesCount();
/**
* Returns <code>true</code> if the current position is anywhere except on
* the start node, <code>false</code> if it is on the start node. This is
* useful because code in {@link StopEvaluator the}
* {@link ReturnableEvaluator evaluators} usually have to treat the edge
* case of the start node separately and using this method makes that code a
* lot cleaner. For example, old code would be:
*
* <pre>
* <code>
* public boolean isReturnableNode( TraversalPosition currentPos )
* {
* if ( currentPos.lastRelationshipTraversed() == null )
* {
* return false;
* }
* else
* {
* return currentPos.lastRelationshipTraversed().isType(
* MyRelationshipTypes.SOME_REL );
* }
* }
* </code>
* </pre>
*
* But using <code>notStartNode()</code>:
*
* <pre>
* <code>
* public boolean isReturnableNode( TraversalPosition currentPos )
* {
* return currentPos.notStartNode()
* && currentPos.lastRelationshipTraversed().isType(
* MyRelationshipTypes.SOME_REL );
* }
* </code>
* </pre>
*
* @return <code>true</code> if the traversal is not currently positioned
* on the start node, <code>false</code> if it is
*/
public boolean notStartNode();
/**
* Returns <code>true</code> if the current position is the start node,
* <code>false</code> otherwise. This is useful because code in
* {@link StopEvaluator the} {@link ReturnableEvaluator evaluators} usually
* have to treat the edge case of the start node separately and using this
* method makes that code a lot cleaner. For example, old code would be:
*
* <pre>
* <code>
* public boolean isReturnableNode( TraversalPosition currentPos )
* {
* if ( currentPos.lastRelationshipTraversed() == null )
* {
* return false;
* }
* else
* {
* return currentPos.lastRelationshipTraversed().isType(
* MyRelationshipTypes.SOME_REL );
* }
* }
* </code>
* </pre>
*
* But using <code>notStartNode()</code>:
*
* <pre>
* <code>
* public boolean isReturnableNode( TraversalPosition currentPos )
* {
* return !currentPos.isStartNode()
* && currentPos.lastRelationshipTraversed().isType(
* MyRelationshipTypes.SOME_REL );
* }
* </code>
* </pre>
*
* @return <code>true</code> if the traversal is on the start node,
* <code>false</code> otherwise.
*/
public boolean isStartNode();
}