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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.script;

import org.apache.lucene.index.LeafReaderContext;
import org.elasticsearch.common.xcontent.support.XContentMapValues;
import org.elasticsearch.search.lookup.SearchLookup;
import org.elasticsearch.search.lookup.SourceLookup;

import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.function.Function;

import static org.elasticsearch.core.TimeValue.timeValueMillis;

/**
 * Abstract base for scripts to execute to build scripted fields. Inspired by
 * {@link AggregationScript} but hopefully with less historical baggage.
 */
public abstract class AbstractFieldScript extends DocBasedScript {
    /**
     * The maximum number of values a script should be allowed to emit.
     */
    public static final int MAX_VALUES = 100;

    static  ScriptContext newContext(String name, Class factoryClass) {
        return new ScriptContext<>(
            name,
            factoryClass,
            /*
             * We rely on the script cache in two ways:
             * 1. It caches the "heavy" part of mappings generated at runtime.
             * 2. Mapping updates tend to try to compile the script twice. Not
             *    for any good reason. They just do.
             * Thus we use the default 100.
             */
            100,
            timeValueMillis(0),
            /*
             * Disable compilation rate limits for runtime fields so we
             * don't prevent mapping updates because we've performed too
             * many recently. That'd just be lame. We also compile these
             * scripts during search requests so this could totally be a
             * source of runaway script compilations. We think folks will
             * mostly reuse scripts though.
             */
            false,
            /*
             * Disable runtime fields scripts from being allowed
             * to be stored as part of the script meta data.
             */
            false
        );
    }

    private static final Map> PARAMS_FUNCTIONS = org.elasticsearch.core.Map.of(
        "_source",
        value -> ((SourceLookup) value).source()
    );

    protected final String fieldName;
    protected final SourceLookup sourceLookup;
    private final Map params;

    public AbstractFieldScript(String fieldName, Map params, SearchLookup searchLookup, LeafReaderContext ctx) {
        super(new DocValuesDocReader(searchLookup, ctx));

        this.fieldName = fieldName;
        Map docAsMap = docAsMap();
        this.sourceLookup = (SourceLookup) docAsMap.get("_source");
        params = new HashMap<>(params);
        params.put("_source", sourceLookup);
        params.put("_fields", docAsMap.get("_fields"));
        this.params = new DynamicMap(params, PARAMS_FUNCTIONS);
    }

    /**
     * Expose the {@code params} of the script to the script itself.
     */
    public final Map getParams() {
        return params;
    }

    protected List