/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.cassandra.db.rows;

import org.apache.cassandra.utils.AbstractIterator;

import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.db.*;

Abstract class to create UnfilteredRowIterator that lazily initialize themselves. This is used during partition range queries when we know the partition key but want to defer the initialization of the rest of the UnfilteredRowIterator until we need those informations. See KeyScanningIterator for instance. /**
 * Abstract class to create UnfilteredRowIterator that lazily initialize themselves.
 *
 * This is used during partition range queries when we know the partition key but want
 * to defer the initialization of the rest of the UnfilteredRowIterator until we need those informations.
 * See {@link org.apache.cassandra.io.sstable.format.big.BigTableScanner.KeyScanningIterator} for instance.
 */
public abstract class LazilyInitializedUnfilteredRowIterator extends AbstractIterator<Unfiltered> implements UnfilteredRowIterator
{
    private final DecoratedKey partitionKey;

    private UnfilteredRowIterator iterator;

    public LazilyInitializedUnfilteredRowIterator(DecoratedKey partitionKey)
    {
        this.partitionKey = partitionKey;
    }

    protected abstract UnfilteredRowIterator initializeIterator();

    protected void maybeInit()
    {
        if (iterator == null)
            iterator = initializeIterator();
    }

    public boolean initialized()
    {
        return iterator != null;
    }

    public CFMetaData metadata()
    {
        maybeInit();
        return iterator.metadata();
    }

    public PartitionColumns columns()
    {
        maybeInit();
        return iterator.columns();
    }

    public boolean isReverseOrder()
    {
        maybeInit();
        return iterator.isReverseOrder();
    }

    public DecoratedKey partitionKey()
    {
        return partitionKey;
    }

    public DeletionTime partitionLevelDeletion()
    {
        maybeInit();
        return iterator.partitionLevelDeletion();
    }

    public Row staticRow()
    {
        maybeInit();
        return iterator.staticRow();
    }

    public EncodingStats stats()
    {
        maybeInit();
        return iterator.stats();
    }

    protected Unfiltered computeNext()
    {
        maybeInit();
        return iterator.hasNext() ? iterator.next() : endOfData();
    }

    public void close()
    {
        if (iterator != null)
            iterator.close();
    }
}