/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.action.search;

import org.opensearch.common.util.concurrent.AtomicArray;
import org.opensearch.search.SearchPhaseResult;

import java.util.stream.Stream;

/**
 * This class acts as a basic result collection that can be extended to do on-the-fly reduction or result processing
 *
 * @opensearch.internal
 */
public abstract class SearchPhaseResults<Result extends SearchPhaseResult> {
    private final int numShards;

    SearchPhaseResults(int numShards) {
        this.numShards = numShards;
    }

    /**
     * Returns the number of expected results this class should collect
     */
    final int getNumShards() {
        return numShards;
    }

    /**
     * A stream of all non-null (successful) shard results
     */
    abstract Stream<Result> getSuccessfulResults();

    /**
     * Consumes a single shard result
     * @param result the shards result
     * @param next a {@link Runnable} that is executed when the response has been fully consumed
     */
    abstract void consumeResult(Result result, Runnable next);

    /**
     * Returns <code>true</code> iff a result if present for the given shard ID.
     */
    abstract boolean hasResult(int shardIndex);

    void consumeShardFailure(int shardIndex) {}

    /**
     * Returns an {@link AtomicArray} of {@link Result}, which are nothing but the SearchPhaseResults
     * for shards. The {@link Result} are of type {@link SearchPhaseResult}
     *
     * @return an {@link AtomicArray} of {@link Result}
     */
    public AtomicArray<Result> getAtomicArray() {
        throw new UnsupportedOperationException();
    }

    /**
     * Reduces the collected results
     */
    SearchPhaseController.ReducedQueryPhase reduce() throws Exception {
        throw new UnsupportedOperationException("reduce is not supported");
    }
}