package org.neo4j.rdf.sail.rmi;

import info.aduna.iteration.CloseableIteration;

import java.rmi.RemoteException;
import java.rmi.server.RMIClientSocketFactory;
import java.rmi.server.RMIServerSocketFactory;
import java.rmi.server.UnicastRemoteObject;
import java.rmi.server.Unreferenced;
import java.util.Collection;
import java.util.LinkedList;
import java.util.List;

/**
 * A buffering iterator which sits on the server side, fetching a bunch of
 * items in an iteration each time to minimize the network overhead.
 *
 * @param <E> the type of items in the iteration.
 * @param <X> the type of exception thrown if something goes wrong.
 */
class IterationBufferer<E, X extends Exception> extends UnicastRemoteObject
    implements RmiIterationBuffer<E, X>, Unreferenced
{
    private static final int CHUNK_SIZE = 10;
    private final CloseableIteration<E, X> iter;
    private boolean open = true;
    
    IterationBufferer( CloseableIteration<E, X> iter ) throws RemoteException
    {
        super();
        this.iter = iter;
    }
    
    IterationBufferer( CloseableIteration<E, X> iter, int port )
        throws RemoteException
    {
        super( port );
        this.iter = iter;
    }
    
    IterationBufferer( CloseableIteration<E, X> iter, int port,
        RMIClientSocketFactory csf, RMIServerSocketFactory ssf )
        throws RemoteException
    {
        super( port, csf, ssf );
        this.iter = iter;
    }
    
    public void close() throws X
    {
        open = false;
        iter.close();
    }
    
    public void unreferenced() {
        if (open)
        {
            try
            {
                close();
            }
            catch (Exception ex)
            {
                // Nothing we can do about it
            }
        }
    }
    
    public Collection<E> getChunk() throws X, RemoteException
    {
        if ( !open ) return null;
        List<E> data = new LinkedList<E>();
        for ( int count = CHUNK_SIZE; count > 0 && iter.hasNext(); count-- )
        {
            data.add( iter.next() );
        }
        return data;
    }
}