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/*
 * 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.
 */

package org.elasticsearch.index.query;

import org.elasticsearch.common.xcontent.XContentBuilder;

import java.io.IOException;
import java.util.ArrayList;

/**
 * A query that generates the union of documents produced by its sub-queries, and that scores each document
 * with the maximum score for that document as produced by any sub-query, plus a tie breaking increment for any
 * additional matching sub-queries.
 */
public class DisMaxQueryBuilder extends QueryBuilder implements BoostableQueryBuilder {

    private ArrayList queries = new ArrayList<>();

    private float boost = -1;

    private float tieBreaker = -1;

    private String queryName;

    /**
     * Add a sub-query to this disjunction.
     */
    public DisMaxQueryBuilder add(QueryBuilder queryBuilder) {
        queries.add(queryBuilder);
        return this;
    }

    /**
     * Sets the boost for this query.  Documents matching this query will (in addition to the normal
     * weightings) have their score multiplied by the boost provided.
     */
    @Override
    public DisMaxQueryBuilder boost(float boost) {
        this.boost = boost;
        return this;
    }

    /**
     * The score of each non-maximum disjunct for a document is multiplied by this weight
     * and added into the final score.  If non-zero, the value should be small, on the order of 0.1, which says that
     * 10 occurrences of word in a lower-scored field that is also in a higher scored field is just as good as a unique
     * word in the lower scored field (i.e., one that is not in any higher scored field.
     */
    public DisMaxQueryBuilder tieBreaker(float tieBreaker) {
        this.tieBreaker = tieBreaker;
        return this;
    }

    /**
     * Sets the query name for the filter that can be used when searching for matched_filters per hit.
     */
    public DisMaxQueryBuilder queryName(String queryName) {
        this.queryName = queryName;
        return this;
    }

    @Override
    protected void doXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject(DisMaxQueryParser.NAME);
        if (tieBreaker != -1) {
            builder.field("tie_breaker", tieBreaker);
        }
        if (boost != -1) {
            builder.field("boost", boost);
        }
        if (queryName != null) {
            builder.field("_name", queryName);
        }
        builder.startArray("queries");
        for (QueryBuilder queryBuilder : queries) {
            queryBuilder.toXContent(builder, params);
        }
        builder.endArray();
        builder.endObject();
    }
}