/*
 * 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.index.engine;

import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.search.ReferenceManager;
import org.apache.lucene.search.SearcherManager;
import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
import org.elasticsearch.core.SuppressForbidden;

import java.io.IOException;

/**
 * Utility class to safely share {@link ElasticsearchDirectoryReader} instances across
 * multiple threads, while periodically reopening. This class ensures each
 * reader is closed only once all threads have finished using it.
 *
 * @see SearcherManager
 *
 */
@SuppressForbidden(reason = "reference counting is required here")
public class ElasticsearchReaderManager extends ReferenceManager<ElasticsearchDirectoryReader> {

    /**
     * Creates and returns a new ElasticsearchReaderManager from the given
     * already-opened {@link ElasticsearchDirectoryReader}, stealing
     * the incoming reference.
     *
     * @param reader            the directoryReader to use for future reopens
     */
    public ElasticsearchReaderManager(ElasticsearchDirectoryReader reader) {
        this.current = reader;
    }

    @Override
    protected void decRef(ElasticsearchDirectoryReader reference) throws IOException {
        reference.decRef();
    }

    @Override
    protected ElasticsearchDirectoryReader refreshIfNeeded(ElasticsearchDirectoryReader referenceToRefresh) throws IOException {
        return (ElasticsearchDirectoryReader) DirectoryReader.openIfChanged(referenceToRefresh);
    }

    @Override
    protected boolean tryIncRef(ElasticsearchDirectoryReader reference) {
        return reference.tryIncRef();
    }

    @Override
    protected int getRefCount(ElasticsearchDirectoryReader reference) {
        return reference.getRefCount();
    }
}