/**
 * Copyright (c) 2002-2011 "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.kernel.ha;

import java.util.Collection;
import java.util.Iterator;

import org.neo4j.helpers.Triplet;
import org.neo4j.helpers.collection.PrefetchingIterator;

/**
 * Represents a stream of the data of one or more consecutive transactions.
 */
public abstract class TransactionStream extends
        PrefetchingIterator<Triplet<String/*datasource*/, Long/*txid*/, TxExtractor>>
{
    public static final TransactionStream EMPTY = new TransactionStream()
    {
        @Override
        protected Triplet<String, Long, TxExtractor> fetchNextOrNull()
        {
            return null;
        }
    };
    private final String[] datasources;

    public TransactionStream( String... datasources )
    {
        this.datasources = datasources;
    }

    public String[] dataSourceNames()
    {
        return datasources.clone();
    }

    public static TransactionStream create( Collection<String> datasources,
            Iterable<Triplet<String, Long, TxExtractor>> streamSource )
    {
        final Iterator<Triplet<String, Long, TxExtractor>> stream = streamSource.iterator();
        return new TransactionStream( datasources.toArray( new String[datasources.size()] ) )
        {
            @Override
            protected Triplet<String, Long, TxExtractor> fetchNextOrNull()
            {
                if ( stream.hasNext() ) return stream.next();
                return null;
            }
        };
    }
}