/*
 * Copyright 2002-2016 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.security.core.parameters;

import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.core.LocalVariableTableParameterNameDiscoverer;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.core.PrioritizedParameterNameDiscoverer;
import org.springframework.security.access.method.P;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * Spring Security's default {@link ParameterNameDiscoverer} which tries a number of
 * {@link ParameterNameDiscoverer} depending on what is found on the classpath.
 *
 * <ul>
 * <li>Will use an instance of {@link AnnotationParameterNameDiscoverer} with {@link P} as
 * a valid annotation. If, Spring Data is on the classpath will also add Param annotation.
 * </li>
 * <li>If Spring 4 is on the classpath, then DefaultParameterNameDiscoverer is added. This
 * attempts to use JDK 8 information first and falls back to
 * {@link LocalVariableTableParameterNameDiscoverer}.</li>
 * <li>If Spring 4 is not on the classpath, then
 * {@link LocalVariableTableParameterNameDiscoverer} is added directly.</li>
 * </ul>
 *
 * @see AnnotationParameterNameDiscoverer
 *
 * @author Rob Winch
 * @since 3.2
 */
public class DefaultSecurityParameterNameDiscoverer extends
		PrioritizedParameterNameDiscoverer {

	private final Log logger = LogFactory.getLog(getClass());

	private static final String DATA_PARAM_CLASSNAME = "org.springframework.data.repository.query.Param";
	private static final boolean DATA_PARAM_PRESENT = ClassUtils.isPresent(
			DATA_PARAM_CLASSNAME,
			DefaultSecurityParameterNameDiscoverer.class.getClassLoader());

	/**
	 * Creates a new instance with only the default {@link ParameterNameDiscoverer}
	 * instances.
	 */
	public DefaultSecurityParameterNameDiscoverer() {
		this(Collections.<ParameterNameDiscoverer> emptyList());
	}

	/**
	 * Creates a new instance that first tries the passed in
	 * {@link ParameterNameDiscoverer} instances.
	 * @param parameterNameDiscovers the {@link ParameterNameDiscoverer} before trying the
	 * defaults. Cannot be null.
	 */
	@SuppressWarnings("unchecked")
	public DefaultSecurityParameterNameDiscoverer(
			List<? extends ParameterNameDiscoverer> parameterNameDiscovers) {
		Assert.notNull(parameterNameDiscovers, "parameterNameDiscovers cannot be null");
		for (ParameterNameDiscoverer discover : parameterNameDiscovers) {
			addDiscoverer(discover);
		}

		Set<String> annotationClassesToUse = new HashSet<String>(2);
		annotationClassesToUse.add(P.class.getName());
		if (DATA_PARAM_PRESENT) {
			annotationClassesToUse.add(DATA_PARAM_CLASSNAME);
		}

		addDiscoverer(new AnnotationParameterNameDiscoverer(annotationClassesToUse));
		addDiscoverer(new DefaultParameterNameDiscoverer());
	}
}