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/*
 *  Copyright (c) 2017 Otávio Santana and others
 *   All rights reserved. This program and the accompanying materials
 *   are made available under the terms of the Eclipse Public License v1.0
 *   and Apache License v2.0 which accompanies this distribution.
 *   The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 *   and the Apache License v2.0 is available at http://www.opensource.org/licenses/apache2.0.php.
 *
 *   You may elect to redistribute this code under either of these licenses.
 *
 *   Contributors:
 *
 *   Otavio Santana
 */
package org.jnosql.artemis.graph;

import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversal;
import org.apache.tinkerpop.gremlin.structure.Vertex;
import org.jnosql.diana.api.NonUniqueResultException;

import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Stream;

import static java.util.Collections.emptyMap;
import static java.util.stream.Collectors.toList;

/**
 * The default implementation of {@link ValueMapTraversal}
 */
class DefaultValueMapTraversal implements ValueMapTraversal {

    private final Supplier> supplier;
    private final Function, GraphTraversal>> flow;

    DefaultValueMapTraversal(Supplier> supplier, Function,
            GraphTraversal>> flow) {
        this.supplier = supplier;
        this.flow = flow;
    }


    @Override
    public Stream> stream() {
        return flow.apply(supplier.get()).toList().stream();
    }

    @Override
    public Stream> next(int limit) {
        return flow.apply(supplier.get()).next(limit).stream();
    }

    @Override
    public Map next() {
        return flow.apply(supplier.get()).tryNext().orElse(emptyMap());
    }

    @Override
    public Optional> getSingleResult() {
        List> result = getResultList();
        if (result.isEmpty()) {
            return Optional.empty();
        }
        if (result.size() == 1) {
            return Optional.of(result.get(0));
        }
        throw new NonUniqueResultException("The Edge traversal query returns more than one result");
    }

    @Override
    public List> getResultList() {
        return stream().collect(toList());
    }

    @Override
    public long count() {
        return flow.apply(supplier.get()).count().tryNext().orElse(0L);
    }
}