/*
 * Licensed to CRATE Technology GmbH ("Crate") under one or more contributor
 * license agreements.  See the NOTICE file distributed with this work for
 * additional information regarding copyright ownership.  Crate licenses
 * this file to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.  You may
 * obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * However, if you have executed another commercial license agreement
 * with Crate these terms will supersede the license and you may use the
 * software solely pursuant to the terms of the relevant commercial agreement.
 */

package io.crate.operation.projectors;

import io.crate.data.*;
import io.crate.operation.collect.CollectExpression;

import java.util.Collection;
import java.util.Comparator;

public class SortingTopNProjector implements Projector {

    private final SortingTopNCollector collector;

    /**
     * @param inputs             contains output {@link Input}s and orderBy {@link Input}s
     * @param collectExpressions gathered from outputs and orderBy inputs
     * @param numOutputs         <code>inputs</code> contains this much output {@link Input}s starting form index 0
     * @param ordering           ordering that is used to compare the rows
     * @param limit              the number of rows to gather, pass to upStream
     * @param offset             the initial offset, this number of rows are skipped
     */
    public SortingTopNProjector(Collection<? extends Input<?>> inputs,
                                Iterable<? extends CollectExpression<Row, ?>> collectExpressions,
                                int numOutputs,
                                Comparator<Object[]> ordering,
                                int limit,
                                int offset) {
        collector = new SortingTopNCollector(
            inputs,
            collectExpressions,
            numOutputs,
            ordering,
            limit,
            offset
        );
    }

    @Override
    public BatchIterator apply(BatchIterator batchIterator) {
        return CollectingBatchIterator.newInstance(batchIterator, collector, collector.numOutputs());
    }

    @Override
    public boolean providesIndependentScroll() {
        return true;
    }
}