/*
 * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */
package org.elasticsearch.search.suggest.phrase;

import org.apache.lucene.codecs.TermStats;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.search.suggest.phrase.DirectCandidateGenerator.Candidate;
import org.elasticsearch.search.suggest.phrase.DirectCandidateGenerator.CandidateSet;

import java.io.IOException;
import java.util.Arrays;

//TODO public for tests
public final class MultiCandidateGeneratorWrapper extends CandidateGenerator {

    private final CandidateGenerator[] candidateGenerator;
    private final int numCandidates;

    public MultiCandidateGeneratorWrapper(int numCandidates, CandidateGenerator... candidateGenerators) {
        this.candidateGenerator = candidateGenerators;
        this.numCandidates = numCandidates;
    }

    @Override
    public TermStats termStats(BytesRef term) throws IOException {
        return candidateGenerator[0].termStats(term);
    }

    @Override
    public CandidateSet drawCandidates(CandidateSet set) throws IOException {
        for (CandidateGenerator generator : candidateGenerator) {
            generator.drawCandidates(set);
        }
        return reduce(set, numCandidates);
    }

    private static CandidateSet reduce(CandidateSet set, int numCandidates) {
        if (set.candidates.length > numCandidates) {
            Candidate[] candidates = set.candidates;
            Arrays.sort(candidates, (left, right) -> Double.compare(right.score, left.score));
            Candidate[] newSet = new Candidate[numCandidates];
            System.arraycopy(candidates, 0, newSet, 0, numCandidates);
            set.candidates = newSet;
        }

        return set;
    }

    @Override
    public Candidate createCandidate(BytesRef term, TermStats termStats, double channelScore, boolean userInput) throws IOException {
        return candidateGenerator[0].createCandidate(term, termStats, channelScore, userInput);
    }

}