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A graph pattern matcher for Neo4j.
There is a newer version: 3.2.0-alpha02
/*
 * Copyright (c) 2002-2017 "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 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.graphmatching;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;

/**
 * Represents a position were we are in the pattern itself. So the
 * {@link PatternMatcher} starts matching from a starting point, on a
 * {@link PatternNode} and when trying to find a complete match (a complete
 * match is a graph) it uses the PatternPosition to know where in the matching
 * pattern we are at the moment.
 */
@Deprecated
class PatternPosition
{
    private Node currentNode;
    private PatternNode pNode;
    private Iterator itr;
    private PatternRelationship nextPRel = null;
    private PatternRelationship previous = null;
    private PatternRelationship returnPrevious = null;
    private boolean optional = false;
    private PatternRelationship fromPRel = null;
    private Relationship fromRel = null;

    PatternPosition( Node currentNode, PatternNode pNode, boolean optional )
    {
        this.currentNode = currentNode;
        this.pNode = pNode;
        itr = pNode.getRelationships( optional ).iterator();
        this.optional = optional;
    }

    PatternPosition( Node currentNode, PatternNode pNode,
        PatternRelationship fromPRel, Relationship fromRel, boolean optional )
    {
        this.currentNode = currentNode;
        this.pNode = pNode;
        itr = pNode.getRelationships( optional ).iterator();
        this.optional = optional;
        this.fromPRel = fromPRel;
        this.fromRel = fromRel;
    }

    Node getCurrentNode()
    {
        return currentNode;
    }

    private void setNextQRel()
    {
        while ( itr.hasNext() )
        {
            nextPRel = itr.next();
            if ( !nextPRel.isMarked() )
            {
                return;
            }
            nextPRel = null;
        }
    }

    PatternNode getPatternNode()
    {
        return pNode;
    }

    boolean hasNext()
    {
        if ( returnPrevious != null )
        {
            return true;
        }
        if ( nextPRel == null )
        {
            setNextQRel();
        }
        return nextPRel != null;
    }

    PatternRelationship next()
    {
        if ( returnPrevious != null )
        {
            PatternRelationship relToReturn = returnPrevious;
            returnPrevious = null;
            return relToReturn;
        }
        if ( nextPRel == null )
        {
            setNextQRel();
        }
        else
        {
            return resetNextPRel();
        }
        if ( nextPRel == null )
        {
            throw new NoSuchElementException();
        }
        return resetNextPRel();
    }

    private PatternRelationship resetNextPRel()
    {
        PatternRelationship relToReturn = nextPRel;
        previous = nextPRel;
        nextPRel = null;
        return relToReturn;
    }

    void reset()
    {
        returnPrevious = null;
        previous = null;
        nextPRel = null;
        itr = pNode.getRelationships( optional ).iterator();
    }

    public void returnPreviousAgain()
    {
        returnPrevious = previous;
    }

    @Override
    public String toString()
    {
        return pNode.toString();
    }

    public PatternRelationship fromPatternRel()
    {
        return fromPRel;
    }

    public Relationship fromRelationship()
    {
        return fromRel;
    }
}