/*
 * Copyright (c) 2011-2014 Pivotal Software, Inc.
 *
 *  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 reactor.bus.filter;

import java.util.Collections;
import java.util.List;

/**
 * A {@link Filter} implementation that returns the first item.
 *
 * @author Stephane Maldini
 *
 */
public final class FirstFilter extends AbstractFilter {

	@Override
	public <T> List<T> doFilter(List<T> items, Object key) {
		if (items.isEmpty()) {
			return items;
		} else {
			return Collections.singletonList(items.get(0));
		}
	}
}
