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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.script;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Scorer;
import org.elasticsearch.index.fielddata.ScriptDocValues;
import org.elasticsearch.search.lookup.LeafSearchLookup;
import org.elasticsearch.search.lookup.SearchLookup;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.function.DoubleSupplier;

/**
 * A script used for adjusting the score on a per document basis.
 */
public abstract class ScoreScript {

    private static final Map DEPRECATIONS;
    static {
        Map deprecations = new HashMap<>();
        deprecations.put(
            "doc",
            "Accessing variable [doc] via [params.doc] from within a score script " +
                "is deprecated in favor of directly accessing [doc]."
        );
        deprecations.put(
            "_doc",
            "Accessing variable [doc] via [params._doc] from within a score script " +
                "is deprecated in favor of directly accessing [doc]."
        );
        DEPRECATIONS = Collections.unmodifiableMap(deprecations);
    }

    public static final String[] PARAMETERS = new String[]{};
    
    /** The generic runtime parameters for the script. */
    private final Map params;
    
    /** A leaf lookup for the bound segment this script will operate on. */
    private final LeafSearchLookup leafLookup;
    
    private DoubleSupplier scoreSupplier = () -> 0.0;
    
    public ScoreScript(Map params, SearchLookup lookup, LeafReaderContext leafContext) {
        // null check needed b/c of expression engine subclass
        if (lookup == null) {
            assert params == null;
            assert leafContext == null;
            this.params = null;
            this.leafLookup = null;
        } else {
            this.leafLookup = lookup.getLeafSearchLookup(leafContext);
            params = new HashMap<>(params);
            params.putAll(leafLookup.asMap());
            this.params = new DeprecationMap(params, DEPRECATIONS);
        }
    }
    
    public abstract double execute();
    
    /** Return the parameters for this script. */
    public Map getParams() {
        return params;
    }
    
    /** The doc lookup for the Lucene segment this script was created for. */
    public final Map> getDoc() {
        return leafLookup.doc();
    }
    
    /** Set the current document to run the script on next. */
    public void setDocument(int docid) {
        leafLookup.setDocument(docid);
    }
    
    public void setScorer(Scorer scorer) {
        this.scoreSupplier = () -> {
            try {
                return scorer.score();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        };
    }
    
    public double get_score() {
        return scoreSupplier.getAsDouble();
    }
    
    /** A factory to construct {@link ScoreScript} instances. */
    public interface LeafFactory {
    
        /**
         * Return {@code true} if the script needs {@code _score} calculated, or {@code false} otherwise.
         */
        boolean needs_score();
        
        ScoreScript newInstance(LeafReaderContext ctx) throws IOException;
    }
    
    /** A factory to construct stateful {@link ScoreScript} factories for a specific index. */
    public interface Factory {
        
        ScoreScript.LeafFactory newFactory(Map params, SearchLookup lookup);
        
    }
    
    public static final ScriptContext CONTEXT = new ScriptContext<>("score", ScoreScript.Factory.class);
}