/*
* Copyright 2008 Network Engine for Objects in Lund AB [neotechnology.com]
*
* This program 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.graphalgo.shortestpath;
import org.neo4j.graphdb.Relationship;
/**
* In order to make the solving of shortest path problems as general as
* possible, the algorithms accept objects handling all relevant tasks regarding
* costs of paths. This allows the user to represent the costs in any possible
* way, and to calculate them in any way. The usual case is numbers that we just
* add together, but what if we have for example factors we would like to
* multiply instead? This is handled by this system, which works as follows. A
* CostEvaluator is used to get the cost for a single relationship. These costs
* are then added through a CostAccumulator. Costs for alternative paths are
* compared with a common java.util.Comparator.
* @author Patrik Larsson
* @param <CostType>
* The datatype the edge weigths are represented by.
*/
public interface CostEvaluator<CostType>
{
/**
* This is the general method for looking up costs for relationships. This
* can do anything, like looking up a property or running some small
* calculation.
* @param relationship
* @param backwards
* True if an eventual path would be going in the opposite
* direction through this edge, ie from the end node to the start
* node. This will always be false when using Direction.OUTGOING
* and always true when using Direction.INCOMMING
* @return The cost for this edge/relationship
*/
CostType getCost( Relationship relationship, boolean backwards );
}