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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.

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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [https://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 .
 */
package org.neo4j.kernel.impl.traversal;

import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Path;
import org.neo4j.graphdb.PathExpander;
import org.neo4j.graphdb.traversal.BranchOrderingPolicy;
import org.neo4j.graphdb.traversal.BranchSelector;
import org.neo4j.graphdb.traversal.BranchState;
import org.neo4j.graphdb.traversal.Evaluation;
import org.neo4j.graphdb.traversal.InitialBranchState;
import org.neo4j.graphdb.traversal.PathEvaluator;
import org.neo4j.graphdb.traversal.TraversalBranch;
import org.neo4j.graphdb.traversal.UniquenessFactory;
import org.neo4j.graphdb.traversal.UniquenessFilter;

class MonoDirectionalTraverserIterator extends AbstractTraverserIterator {
    private final BranchSelector selector;
    private final PathEvaluator evaluator;
    private final UniquenessFilter uniqueness;

    MonoDirectionalTraverserIterator(
            UniquenessFilter uniqueness,
            PathExpander expander,
            BranchOrderingPolicy order,
            PathEvaluator evaluator,
            Iterable startNodes,
            InitialBranchState initialState,
            UniquenessFactory uniquenessFactory) {
        this.uniqueness = uniqueness;
        this.evaluator = evaluator;
        this.selector = order.create(new AsOneStartBranch(this, startNodes, initialState, uniquenessFactory), expander);
    }

    @Override
    public Evaluation evaluate(TraversalBranch branch, BranchState state) {
        return evaluator.evaluate(branch, state);
    }

    @Override
    protected Path fetchNextOrNull() {
        TraversalBranch result;
        while (true) {
            result = selector.next(this);
            if (result == null) {
                return null;
            }
            if (result.includes()) {
                numberOfPathsReturned++;
                return result;
            }
        }
    }

    @Override
    public boolean isUniqueFirst(TraversalBranch branch) {
        return uniqueness.checkFirst(branch);
    }

    @Override
    public boolean isUnique(TraversalBranch branch) {
        return uniqueness.check(branch);
    }
}