/*
 * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * 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.access.intercept.aopalliance;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.*;

import org.aopalliance.aop.Advice;
import org.aopalliance.intercept.MethodInterceptor;
import org.springframework.aop.Pointcut;
import org.springframework.aop.support.AbstractPointcutAdvisor;
import org.springframework.aop.support.StaticMethodMatcherPointcut;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.security.access.method.MethodSecurityMetadataSource;
import org.springframework.util.Assert;

/**
 * Advisor driven by a {@link MethodSecurityMetadataSource}, used to exclude a
 * {@link MethodInterceptor} from public (non-secure) methods.
 * <p>
 * Because the AOP framework caches advice calculations, this is normally faster than just
 * letting the <code>MethodInterceptor</code> run and find out itself that it has
 * no work to do.
 * <p>
 * This class also allows the use of Spring's {@code DefaultAdvisorAutoProxyCreator},
 * which makes configuration easier than setup a <code>ProxyFactoryBean</code> for each
 * object requiring security. Note that autoproxying is not supported for BeanFactory
 * implementations, as post-processing is automatic only for application contexts.
 * <p>
 * Based on Spring's TransactionAttributeSourceAdvisor.
 *
 * @author Ben Alex
 * @author Luke Taylor
 */
public class MethodSecurityMetadataSourceAdvisor extends AbstractPointcutAdvisor
		implements BeanFactoryAware {
	// ~ Instance fields
	// ================================================================================================

	private transient MethodSecurityMetadataSource attributeSource;
	private transient MethodInterceptor interceptor;
	private final Pointcut pointcut = new MethodSecurityMetadataSourcePointcut();
	private BeanFactory beanFactory;
	private final String adviceBeanName;
	private final String metadataSourceBeanName;
	private transient volatile Object adviceMonitor = new Object();

	// ~ Constructors
	// ===================================================================================================

	/**
	 * Alternative constructor for situations where we want the advisor decoupled from the
	 * advice. Instead the advice bean name should be set. This prevents eager
	 * instantiation of the interceptor (and hence the AuthenticationManager). See
	 * SEC-773, for example. The metadataSourceBeanName is used rather than a direct
	 * reference to support serialization via a bean factory lookup.
	 *
	 * @param adviceBeanName name of the MethodSecurityInterceptor bean
	 * @param attributeSource the SecurityMetadataSource (should be the same as the one
	 * used on the interceptor)
	 * @param attributeSourceBeanName the bean name of the attributeSource (required for
	 * serialization)
	 */
	public MethodSecurityMetadataSourceAdvisor(String adviceBeanName,
			MethodSecurityMetadataSource attributeSource, String attributeSourceBeanName) {
		Assert.notNull(adviceBeanName, "The adviceBeanName cannot be null");
		Assert.notNull(attributeSource, "The attributeSource cannot be null");
		Assert.notNull(attributeSourceBeanName,
				"The attributeSourceBeanName cannot be null");

		this.adviceBeanName = adviceBeanName;
		this.attributeSource = attributeSource;
		this.metadataSourceBeanName = attributeSourceBeanName;
	}

	// ~ Methods
	// ========================================================================================================

	public Pointcut getPointcut() {
		return pointcut;
	}

	public Advice getAdvice() {
		synchronized (this.adviceMonitor) {
			if (interceptor == null) {
				Assert.notNull(adviceBeanName,
						"'adviceBeanName' must be set for use with bean factory lookup.");
				Assert.state(beanFactory != null,
						"BeanFactory must be set to resolve 'adviceBeanName'");
				interceptor = beanFactory.getBean(this.adviceBeanName,
					MethodInterceptor.class);
			}
			return interceptor;
		}
	}

	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		this.beanFactory = beanFactory;
	}

	private void readObject(ObjectInputStream ois) throws IOException,
			ClassNotFoundException {
		ois.defaultReadObject();
		adviceMonitor = new Object();
		attributeSource = beanFactory.getBean(metadataSourceBeanName,
				MethodSecurityMetadataSource.class);
	}

	// ~ Inner Classes
	// ==================================================================================================

	class MethodSecurityMetadataSourcePointcut extends StaticMethodMatcherPointcut
			implements Serializable {
		@SuppressWarnings("unchecked")
		public boolean matches(Method m, Class targetClass) {
			Collection attributes = attributeSource.getAttributes(m, targetClass);
			return attributes != null && !attributes.isEmpty();
		}
	}
}
