/*
 * 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.graphalgo.impl.util;

import static org.neo4j.graphdb.Direction.OUTGOING;

import org.neo4j.graphalgo.CostEvaluator;
import org.neo4j.graphdb.traversal.TraversalBranch;

public class DijkstraSelectorFactory extends BestFirstSelectorFactory<Double, Double> {
    private final CostEvaluator<Double> evaluator;

    public DijkstraSelectorFactory(PathInterest<Double> interest, CostEvaluator<Double> evaluator) {
        super(interest);
        this.evaluator = evaluator;
    }

    @Override
    protected Double calculateValue(TraversalBranch next) {
        return next.length() == 0 ? 0d : evaluator.getCost(next.lastRelationship(), OUTGOING);
    }

    @Override
    protected Double addPriority(TraversalBranch source, Double currentAggregatedValue, Double value) {
        return withDefault(currentAggregatedValue, 0d) + withDefault(value, 0d);
    }

    private static <T> T withDefault(T valueOrNull, T valueIfNull) {
        return valueOrNull != null ? valueOrNull : valueIfNull;
    }

    @Override
    protected Double getStartData() {
        return 0d;
    }
}
