/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the "Elastic License
 * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
 * Public License v 1"; you may not use this file except in compliance with, at
 * your election, the "Elastic License 2.0", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.search.rank.context;

import org.elasticsearch.core.Nullable;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.rank.RankShardResult;

/**
 * {@link RankFeaturePhaseRankShardContext} is a base class used to execute the RankFeature phase on each shard.
 * In this class, we can fetch the feature data for a given set of documents and pass them back to the coordinator
 * through the {@link RankShardResult}.
 */
public abstract class RankFeaturePhaseRankShardContext {

    protected final String field;

    public RankFeaturePhaseRankShardContext(final String field) {
        this.field = field;
    }

    public String getField() {
        return field;
    }

    /**
     * This is used to fetch the feature data for a given set of documents, using the {@link  org.elasticsearch.search.fetch.FetchPhase}
     * and the {@link org.elasticsearch.search.fetch.subphase.FetchFieldsPhase} subphase.
     * The feature data is then stored in a {@link org.elasticsearch.search.rank.feature.RankFeatureDoc} and passed back to the coordinator.
     */
    @Nullable
    public abstract RankShardResult buildRankFeatureShardResult(SearchHits hits, int shardId);
}