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/*
 * 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.functionscore;

import org.elasticsearch.Version;
import org.elasticsearch.common.ParsingException;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.lucene.search.function.ScoreFunction;
import org.elasticsearch.common.lucene.search.function.ScriptScoreFunction;
import org.elasticsearch.index.query.QueryShardException;
import org.elasticsearch.index.query.SearchExecutionContext;
import org.elasticsearch.script.ScoreScript;
import org.elasticsearch.script.Script;
import org.elasticsearch.search.lookup.SearchLookup;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParser;

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

/**
 * A function that uses a script to compute or influence the score of documents
 * that match with the inner query or filter.
 */
public class ScriptScoreFunctionBuilder extends ScoreFunctionBuilder {
    public static final String NAME = "script_score";

    private final Script script;

    public ScriptScoreFunctionBuilder(Script script) {
        if (script == null) {
            throw new IllegalArgumentException("script must not be null");
        }
        this.script = script;
    }

    /**
     * Read from a stream.
     */
    public ScriptScoreFunctionBuilder(StreamInput in) throws IOException {
        super(in);
        script = new Script(in);
    }

    @Override
    protected void doWriteTo(StreamOutput out) throws IOException {
        script.writeTo(out);
    }

    public Script getScript() {
        return this.script;
    }

    @Override
    public void doXContent(XContentBuilder builder, Params params) throws IOException {
        builder.startObject(getName());
        builder.field(Script.SCRIPT_PARSE_FIELD.getPreferredName(), script);
        builder.endObject();
    }

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

    @Override
    protected boolean doEquals(ScriptScoreFunctionBuilder functionBuilder) {
        return Objects.equals(this.script, functionBuilder.script);
    }

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

    @Override
    public Version getMinimalSupportedVersion() {
        return Version.V_EMPTY;
    }

    @Override
    protected ScoreFunction doToFunction(SearchExecutionContext context) {
        try {
            ScoreScript.Factory factory = context.compile(script, ScoreScript.CONTEXT);
            SearchLookup lookup = context.lookup();
            ScoreScript.LeafFactory searchScript = factory.newFactory(script.getParams(), lookup);
            return new ScriptScoreFunction(script, searchScript, lookup, context.index().getName(), context.getShardId());
        } catch (Exception e) {
            throw new QueryShardException(context, "script_score: the script could not be loaded", e);
        }
    }

    public static ScriptScoreFunctionBuilder fromXContent(XContentParser parser) throws IOException, ParsingException {
        Script script = null;
        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 (Script.SCRIPT_PARSE_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    script = Script.parse(parser);
                } else {
                    throw new ParsingException(parser.getTokenLocation(), NAME + " query does not support [" + currentFieldName + "]");
                }
            }
        }

        if (script == null) {
            throw new ParsingException(parser.getTokenLocation(), NAME + " requires 'script' field");
        }

        return new ScriptScoreFunctionBuilder(script);
    }
}