/*
 * Copyright 2006-2007 the original author or authors.
 *
 * Licensed 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.springframework.batch.item.file.transform;

import java.util.Collection;
import java.util.Map;

/**
 * {@link FieldExtractor} that just returns the original item. If the item is an
 * array or collection it will be returned as is, otherwise it is wrapped in a
 * single element array.
 * 
 * @author Dave Syer
 * 
 */
public class PassThroughFieldExtractor<T> implements FieldExtractor<T> {

	/**
	 * Get an array of fields as close as possible to the input. The result
	 * depends on the type of the input:
	 * <ul>
	 * <li>A {@link FieldSet} or array will be returned as is</li>
	 * <li>For a Collection the <code>toArray()</code> method will be used</li>
	 * <li>For a Map the <code>values()</code> will be returned as an array</li>
	 * <li>Otherwise it is wrapped in a single element array.</li>
	 * </ul>
	 * Note that no attempt is made to sort the values, so passing in an
	 * unordered collection or map is probably a bad idea. Spring often gives
	 * you an ordered Map (e.g. if extracting data from a generic query using
	 * JDBC), so check the documentation for whatever is being used to generate
	 * the input.
	 * 
	 * @param item the object to convert
	 * @return an array of objects as close as possible to the original item
	 */
    @Override
	public Object[] extract(T item) {

		if (item.getClass().isArray()) {
			return (Object[]) item;
		}

		if (item instanceof Collection<?>) {
			return ((Collection<?>) item).toArray();
		}

		if (item instanceof Map<?, ?>) {
			return ((Map<?, ?>) item).values().toArray();
		}

		if (item instanceof FieldSet) {
			return ((FieldSet) item).getValues();
		}

		return new Object[] { item };

	}

}