/**
 * Copyright 2005-2018 The Kuali Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
 *
 * 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.kuali.rice.krad.util;

import java.util.Iterator;

import org.apache.commons.collections.IteratorUtils;

/**
 * This class provides utility methods to support the operation of transactional services
 */
public final class TransactionalServiceUtils {
	
	private TransactionalServiceUtils() {
		throw new UnsupportedOperationException("do not call");
	}
    /**
     * Copys iterators so that they may be used outside of this class.  Often, the DAO may
     * return iterators that may not be used outside of this class because the transaction/
     * connection may be automatically closed by Spring.
     * 
     * This method copies all of the elements in the OJB backed iterators into list-based iterators
     * by placing the returned BOs into a list
     * 
     * @param iter an OJB backed iterator to copy
     * @return an Iterator that may be used outside of this class
     */
    public static <E> Iterator<E> copyToExternallyUsuableIterator(Iterator<E> iter) {
        return IteratorUtils.toList(iter).iterator();
    }
    
    /**
     * Returns the first element and exhausts an iterator
     * 
     * @param <E> the type of elements in the iterator
     * @param iterator the iterator to exhaust
     * @return the first element of the iterator; null if the iterator's empty
     */
    public static <E> E retrieveFirstAndExhaustIterator(Iterator<E> iterator) {
        E returnVal = null;
        if (iterator.hasNext()) {
            returnVal = iterator.next();
        }
        exhaustIterator(iterator);
        return returnVal;
    }
    
    /**
     * Exhausts (i.e. complete iterates through) an iterator
     * 
     * @param iterator
     */
    public static void exhaustIterator(Iterator<?> iterator) {
        while (iterator.hasNext()) {
            iterator.next();
        }
    }
}
