/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */
package org.dspace.checker;

import org.dspace.checker.factory.CheckerServiceFactory;
import org.dspace.checker.service.MostRecentChecksumService;
import org.dspace.content.Bitstream;
import org.dspace.core.Context;

import java.sql.SQLException;
import java.util.Date;

/**
 * An implementation of the selection strategy that selects bitstreams in the
 * order that they were last checked, looping endlessly.
 * 
 * @author Jim Downing
 * @author Grace Carpenter
 * @author Nathan Sarr
 * 
 */
public class SimpleDispatcher implements BitstreamDispatcher
{

    /**
     * Should this dispatcher keep on dispatching around the collection?
     */
    protected boolean loopContinuously = false;

    /**
     * Date this dispatcher started dispatching.
     */
    protected Date processStartTime = null;

    /**
     * Access for bitstream information
     */
    protected MostRecentChecksumService checksumService;

    protected Context context;

    /**
     * Creates a new SimpleDispatcher.
     * 
     * @param context Context
     * @param startTime
     *            timestamp for beginning of checker process
     * @param looping
     *            indicates whether checker should loop infinitely through
     *            most_recent_checksum table
     */
    public SimpleDispatcher(Context context, Date startTime, boolean looping)
    {
        checksumService = CheckerServiceFactory.getInstance().getMostRecentChecksumService();
        this.context = context;
        this.processStartTime = (startTime == null ? null : new Date(startTime.getTime()));
        this.loopContinuously = looping;
    }

    /**
     * Blanked off, no-op constructor. Do not use.
     */
    private SimpleDispatcher()
    {
    }

    /**
     * Selects the next candidate bitstream.
     * 
     * @throws SQLException if database error
     * @see org.dspace.checker.BitstreamDispatcher#next()
     */
    @Override
    public synchronized Bitstream next() throws SQLException {
        // should process loop infinitely through the
        // bitstreams in most_recent_checksum table?
        if (!loopContinuously && (processStartTime != null))
        {
            MostRecentChecksum oldestRecord = checksumService.findOldestRecord(context, processStartTime);
            if(oldestRecord != null)
            {
                return oldestRecord.getBitstream();
            }else{
                return null;
            }
        }
        else
        {
            MostRecentChecksum oldestRecord = checksumService.findOldestRecord(context);
            if(oldestRecord != null)
            {
                return oldestRecord.getBitstream();
            }else{
                return null;
            }
        }

    }
}