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/*
 * (c) Copyright 2018 Palantir Technologies Inc. All rights reserved.
 *
 * Licensed 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.
 */
package com.palantir.atlasdb.keyvalue.dbkvs.impl.batch;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;
import java.util.HashMap;
import java.util.Map;

public final class AccumulatorStrategies {

    private AccumulatorStrategies() {}

    @SuppressWarnings("unchecked")
    public static  BatchingTaskRunner.ResultAccumulatorStrategy> forMap() {
        return (MapAccumulatorStrategy) mapAccumulatorStrategy;
    }

    @SuppressWarnings("unchecked")
    public static  BatchingTaskRunner.ResultAccumulatorStrategy> forListMultimap() {
        return (ListMultimapAccumulatorStrategy) listMultimapAccumulatorStrategy;
    }

    private static final class MapAccumulatorStrategy
            implements BatchingTaskRunner.ResultAccumulatorStrategy> {
        @Override
        public Map createEmptyResult() {
            return new HashMap<>();
        }

        @Override
        public void accumulateResult(Map result, Map toAdd) {
            result.putAll(toAdd);
        }
    }

    private static final MapAccumulatorStrategy mapAccumulatorStrategy = new MapAccumulatorStrategy<>();

    private static final class ListMultimapAccumulatorStrategy
            implements BatchingTaskRunner.ResultAccumulatorStrategy> {
        @Override
        public Multimap createEmptyResult() {
            return ArrayListMultimap.create();
        }

        @Override
        public void accumulateResult(Multimap result, Multimap toAdd) {
            result.putAll(toAdd);
        }
    }

    private static final ListMultimapAccumulatorStrategy listMultimapAccumulatorStrategy =
            new ListMultimapAccumulatorStrategy<>();
}