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package cn.lead2success.ddlutils.platform;

/*
 * 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.
 */

import cn.lead2success.ddlutils.alteration.*;
import cn.lead2success.ddlutils.model.Table;

import java.util.Iterator;
import java.util.List;

/**
 * This is the default predicate for filtering supported table definition changes
 * in the {@link ModelComparator}. It is also useful as the base class for platform
 * specific implementations.
 * 
 * @version $Revision: $
 */
public class DefaultTableDefinitionChangesPredicate implements TableDefinitionChangesPredicate
{
    /**
     * {@inheritDoc}
     */
    public boolean areSupported(Table intermediateTable, List changes)
    {
        for (Iterator changeIt = changes.iterator(); changeIt.hasNext();)
        {
            TableChange change = (TableChange)changeIt.next();

            if (!isSupported(intermediateTable, change))
            {
                return false;
            }
        }
        return true;
    }

    /**
     * Checks whether the given change is suppored.
     * 
     * @param intermediateTable The current table to which this change would be applied
     * @param change            The table change
     * @return true if the change is supported
     */
    protected boolean isSupported(Table intermediateTable, TableChange change)
    {
        if (change instanceof AddColumnChange)
        {
            AddColumnChange addColumnChange = (AddColumnChange)change; 

            return addColumnChange.isAtEnd() &&
                   (!addColumnChange.getNewColumn().isRequired() ||
                    (addColumnChange.getNewColumn().getDefaultValue() != null) ||
                    addColumnChange.getNewColumn().isAutoIncrement());
        }
        else if (change instanceof AddPrimaryKeyChange)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}