package org.neo4j.kernel;
import org.neo4j.graphdb.traversal.TraversalBranch;
import org.neo4j.graphdb.traversal.BranchSelector;
/**
* Selects {@link TraversalBranch}s according to preorder depth first pattern,
* the most natural ordering in a depth first search, see
* http://en.wikipedia.org/wiki/Depth-first_search
*/
class PreorderDepthFirstSelector implements BranchSelector
{
private TraversalBranch current;
PreorderDepthFirstSelector( TraversalBranch startSource )
{
this.current = startSource;
}
public TraversalBranch next()
{
TraversalBranch result = null;
while ( result == null )
{
if ( current == null )
{
return null;
}
TraversalBranch next = current.next();
if ( next == null )
{
current = current.parent();
continue;
}
else
{
current = next;
}
if ( current != null )
{
result = current;
}
}
return result;
}
}