/**
 * Copyright (c) 2002-2011 "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.kernel.impl.traversal;

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Path;
import org.neo4j.graphdb.Relationship;
import org.neo4j.graphdb.traversal.Evaluation;
import org.neo4j.graphdb.traversal.TraversalBranch;
import org.neo4j.kernel.impl.traversal.TraverserImpl.TraverserIterator;

class TraversalBranchImpl implements TraversalBranch
{
    private final TraversalBranch parent;
    private final Node source;
    private Iterator<Relationship> relationships;
    private final Relationship howIGotHere;
    private final int depth;
    final TraverserIterator traverser;
    private Map<Object, Object> state;
    private Path path;
    private int expandedCount;
    private Evaluation evaluation;

    TraversalBranchImpl( TraverserIterator traverser, TraversalBranch parent, int depth,
                         Node source, Relationship toHere, Map<Object, Object> state )
    {
        this.traverser = traverser;
        this.parent = parent;
        this.source = source;
        this.howIGotHere = toHere;
        this.depth = depth;
        this.state = state;
    }

    protected void expandRelationships( boolean doChecks )
    {
        boolean okToExpand = !doChecks || evaluation.continues();
        relationships = okToExpand ?
                traverser.description.expander.expand( source ).iterator() :
                Collections.<Relationship>emptyList().iterator();
    }

    protected boolean hasExpandedRelationships()
    {
        return relationships != null;
    }

    public void initialize()
    {
        evaluatePosition();
        expandRelationships( true );
    }

    protected void evaluatePosition()
    {
        evaluation = traverser.description.evaluator.evaluate( position(), state );
    }

    public TraversalBranch next()
    {
        while ( relationships.hasNext() )
        {
            Relationship relationship = relationships.next();
            if ( relationship.equals( howIGotHere ) )
            {
                continue;
            }
            expandedCount++;
            Node node = relationship.getOtherNode( source );
            TraversalBranch next = new TraversalBranchImpl( traverser, this, depth + 1, node, relationship, new HashMap<Object, Object>( state ) );
            if ( traverser.okToProceed( next ) )
            {
                next.initialize();
                return next;
            }
        }
        return null;
    }

    public Path position()
    {
        return ensurePathInstantiated();
    }

    private Path ensurePathInstantiated()
    {
        if ( this.path == null )
        {
            this.path = new TraversalPath( this );
        }
        return this.path;
    }

    public int depth()
    {
        return depth;
    }

    public Relationship relationship()
    {
        return howIGotHere;
    }

    public Node node()
    {
        return source;
    }

    public TraversalBranch parent()
    {
        return this.parent;
    }

    public int expanded()
    {
        return expandedCount;
    }

    public Evaluation evaluation()
    {
        return evaluation;
    }

    @Override
    public String toString()
    {
        return "TraversalBranch[source=" + source + ",howIGotHere=" + howIGotHere + ",depth=" + depth + "]";
    }
}