/*
 * 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 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 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.index.query;

import org.apache.lucene.search.ConstantScoreQuery;
import org.apache.lucene.search.Query;
import org.elasticsearch.TransportVersion;
import org.elasticsearch.common.ParsingException;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParser;

import java.io.IOException;
import java.util.Map;
import java.util.Objects;

/**
 * A query that wraps a filter and simply returns a constant score equal to the
 * query boost for every document in the filter.
 */
public class ConstantScoreQueryBuilder extends AbstractQueryBuilder<ConstantScoreQueryBuilder> {
    public static final String NAME = "constant_score";

    private static final ParseField INNER_QUERY_FIELD = new ParseField("filter");

    private final QueryBuilder filterBuilder;

    /**
     * A query that wraps another query and simply returns a constant score equal to the
     * query boost for every document in the query.
     *
     * @param filterBuilder The query to wrap in a constant score query
     */
    public ConstantScoreQueryBuilder(QueryBuilder filterBuilder) {
        if (filterBuilder == null) {
            throw new IllegalArgumentException("inner clause [filter] cannot be null.");
        }
        this.filterBuilder = filterBuilder;
    }

    /**
     * Read from a stream.
     */
    public ConstantScoreQueryBuilder(StreamInput in) throws IOException {
        super(in);
        filterBuilder = in.readNamedWriteable(QueryBuilder.class);
    }

    @Override
    protected void doWriteTo(StreamOutput out) throws IOException {
        out.writeNamedWriteable(filterBuilder);
    }

    /**
     * @return the query that was wrapped in this constant score query
     */
    public QueryBuilder innerQuery() {
        return this.filterBuilder;
    }

    @Override
    protected void doXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject(NAME);
        builder.field(INNER_QUERY_FIELD.getPreferredName());
        filterBuilder.toXContent(builder, params);
        printBoostAndQueryName(builder);
        builder.endObject();
    }

    public static ConstantScoreQueryBuilder fromXContent(XContentParser parser) throws IOException {
        QueryBuilder query = null;
        boolean queryFound = false;
        String queryName = null;
        float boost = AbstractQueryBuilder.DEFAULT_BOOST;

        String currentFieldName = null;
        XContentParser.Token token;
        while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
            if (token == XContentParser.Token.FIELD_NAME) {
                currentFieldName = parser.currentName();
            } else if (token == XContentParser.Token.START_OBJECT) {
                if (INNER_QUERY_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    query = parseInnerQueryBuilder(parser);
                    queryFound = true;
                } else {
                    throw new ParsingException(
                        parser.getTokenLocation(),
                        "[constant_score] query does not support [" + currentFieldName + "]"
                    );
                }
            } else if (token.isValue()) {
                if (AbstractQueryBuilder.NAME_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    queryName = parser.text();
                } else if (AbstractQueryBuilder.BOOST_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    boost = parser.floatValue();
                } else {
                    throw new ParsingException(
                        parser.getTokenLocation(),
                        "[constant_score] query does not support [" + currentFieldName + "]"
                    );
                }
            } else {
                throw new ParsingException(parser.getTokenLocation(), "unexpected token [" + token + "]");
            }
        }
        if (queryFound == false) {
            throw new ParsingException(parser.getTokenLocation(), "[constant_score] requires a 'filter' element");
        }

        ConstantScoreQueryBuilder constantScoreBuilder = new ConstantScoreQueryBuilder(query);
        constantScoreBuilder.boost(boost);
        constantScoreBuilder.queryName(queryName);
        return constantScoreBuilder;
    }

    @Override
    protected Query doToQuery(SearchExecutionContext context) throws IOException {
        Query innerFilter = filterBuilder.toQuery(context);
        return new ConstantScoreQuery(innerFilter);
    }

    @Override
    public String getWriteableName() {
        return NAME;
    }

    @Override
    protected int doHashCode() {
        return Objects.hash(filterBuilder);
    }

    @Override
    protected boolean doEquals(ConstantScoreQueryBuilder other) {
        return Objects.equals(filterBuilder, other.filterBuilder);
    }

    @Override
    protected QueryBuilder doRewrite(QueryRewriteContext queryRewriteContext) throws IOException {
        QueryBuilder rewrite = filterBuilder.rewrite(queryRewriteContext);
        if (rewrite instanceof MatchNoneQueryBuilder) {
            return rewrite; // we won't match anyway
        }
        if (rewrite != filterBuilder) {
            return new ConstantScoreQueryBuilder(rewrite);
        }
        return this;
    }

    @Override
    protected void extractInnerHitBuilders(Map<String, InnerHitContextBuilder> innerHits) {
        InnerHitContextBuilder.extractInnerHits(filterBuilder, innerHits);
    }

    @Override
    public TransportVersion getMinimalSupportedVersion() {
        return TransportVersion.ZERO;
    }
}
