// This Source Code is in the Public Domain per: http://unlicense.org
package org.litesoft.orsup.nonpublic;

import java.util.*;

import org.litesoft.orsup.base.*;

public abstract class AbstractPOKeyIterator extends POKeyIterator
{
    private POKeyQueryFilter mPOKeyQueryFilter;
    private PersistenceHelperRowSource mRowSource;
    private Object mPreFetchedKey = null;

    protected AbstractPOKeyIterator( POKeyQueryFilter pPOKeyQueryFilter, PersistenceHelperRowSource pRowSource )
    {
        mPOKeyQueryFilter = pPOKeyQueryFilter;
        mRowSource = PersistenceHelperRowSource.NULL.deNull( pRowSource );
        try
        {
            if ( POQueryFilter.TYPE.NoneAcceptable.equals( pPOKeyQueryFilter.getType() ) )
            {
                releaseRowSource();
                return;
            }
            mRowSource = mRowSource.prepareForGetNextRow();
            mPreFetchedKey = preFetchKey();
        }
        catch ( RuntimeException e )
        {
            releaseResources();
            throw e;
        }
    }

    private void releaseRowSource()
    {
        mRowSource.dispose();
        mRowSource = PersistenceHelperRowSource.NULL.INSTANCE;
    }

    private Object preFetchKey()
    {
        for ( Object[] row; null != (row = mRowSource.getNextRow()); )
        {
            Object zKey = row[0];
            if ( mPOKeyQueryFilter.isPO_KeyAcceptable( zKey ) )
            {
                return zKey;
            }
        }
        releaseRowSource();
        return null;
    }

    @Override
    public void releaseResources()
    {
        releaseRowSource();
        super.releaseResources();
    }

    @Override
    public final boolean hasNext()
    {
        return (mPreFetchedKey != null);
    }

    @Override
    public final Object next()
    {
        if ( !hasNext() )
        {
            throw new NoSuchElementException();
        }
        try
        {
            Object rv = mPreFetchedKey;
            mPreFetchedKey = preFetchKey();
            return rv;
        }
        catch ( RuntimeException e )
        {
            releaseResources();
            throw e;
        }
    }
}