/**
 * Copyright (c) 2002-2012 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package org.neo4j.consistency.store.windowpool;

import static java.lang.String.format;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.channels.FileChannel;

import org.neo4j.graphdb.factory.GraphDatabaseSettings;
import org.neo4j.kernel.configuration.Config;
import org.neo4j.kernel.impl.nioneo.store.UnderlyingStorageException;
import org.neo4j.consistency.store.paging.Cart;
import org.neo4j.kernel.impl.nioneo.store.windowpool.WindowPool;
import org.neo4j.kernel.impl.nioneo.store.windowpool.WindowPoolFactory;
import org.neo4j.kernel.impl.util.StringLogger;

public class ScanResistantWindowPoolFactory implements WindowPoolFactory
{
    private final int targetBytesPerPage;
    private final Cart cart;
    private final int reportingInterval;
    private final MappingStatisticsListener statisticsListener;

    public ScanResistantWindowPoolFactory( Config configuration, StringLogger logger )
    {
        this.targetBytesPerPage = pageSize( configuration );
        this.cart = new Cart( mappablePages( configuration, targetBytesPerPage ) );
        this.reportingInterval = configuration.get( GraphDatabaseSettings.log_mapped_memory_stats_interval );
        this.statisticsListener = createStatisticsListener( configuration, logger );
    }

    private static int pageSize( Config configuration )
    {
        long pageSize = configuration.get( GraphDatabaseSettings.mapped_memory_page_size );
        if ( pageSize > Integer.MAX_VALUE )
        {
            throw new IllegalArgumentException( format( "configured page size [%d bytes] is too large", pageSize ) );
        }
        return (int) pageSize;
    }

    private static int mappablePages( Config configuration, int targetBytesPerPage )
    {
        long bytes = configuration.get( GraphDatabaseSettings.all_stores_total_mapped_memory_size );
        long pageCount = bytes / targetBytesPerPage;
        if ( pageCount > Integer.MAX_VALUE )
        {
            throw new IllegalArgumentException( format( "configured page size [%d bytes] and mapped memory [%d bytes]" +
                    " implies too many pages", targetBytesPerPage, bytes ) );
        }
        return (int) pageCount;
    }

    private MappingStatisticsListener createStatisticsListener( Config configuration, StringLogger logger )
    {
        if ( configuration.get( GraphDatabaseSettings.log_mapped_memory_stats ) )
        {
            try
            {
                return new LoggingStatisticsListener(
                        configuration.get( GraphDatabaseSettings.log_mapped_memory_stats_filename ) );
            }
            catch ( FileNotFoundException e )
            {
                logger.logMessage( "Unable to create logger for mapped memory statistics; will be silent", e );
            }
        }
        return new MappingStatisticsListener()
        {
            @Override
            public void onStatistics( String storeFileName, int acquiredPages, int mappedPages, long samplePeriod )
            {
                // silent
            }
        };
    }

    @Override
    public WindowPool create( String storageFileName, int recordSize, FileChannel fileChannel,
                              Config configuration, StringLogger log )
    {
        try
        {
            return new ScanResistantWindowPool( storageFileName, recordSize, targetBytesPerPage,
                    new FileMapper( fileChannel ), cart, reportingInterval, statisticsListener );
        }
        catch ( IOException e )
        {
            throw new UnderlyingStorageException( e );
        }
    }
}