/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.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 <http://www.gnu.org/licenses/>.
 */
package org.neo4j.graphdb.traversal;

import org.neo4j.annotations.api.PublicApi;

/**
 * Decides "where to go next" in a traversal. It keeps state itself, f.ex. its
 * own current position. Examples of implementations are "depth first" and
 * "breadth first". This is an interface to implement if you'd like to implement
 * f.ex. a "best first" selector based on your own criteria.
 */
@PublicApi
public interface BranchSelector {
    /**
     * Decides the next position ("where to go from here") from the current
     * position, based on the {@code rules}. Since {@link TraversalBranch}
     * has the {@link TraversalBranch#endNode()} of the position and the
     * {@link TraversalBranch#lastRelationship()} to how it got there, decisions
     * can be based on the current expansion source and the given rules.
     *
     * @param metadata the context for the traversal
     * @return the next position based on the current position and the
     * {@code rules} of the traversal.
     */
    TraversalBranch next(TraversalContext metadata);
}
