/*
 * Copyright 2002-2015 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.aop.framework;

import java.lang.reflect.Proxy;
import java.util.Arrays;

import org.springframework.aop.SpringProxy;
import org.springframework.aop.TargetClassAware;
import org.springframework.aop.TargetSource;
import org.springframework.aop.support.AopUtils;
import org.springframework.aop.target.SingletonTargetSource;
import org.springframework.util.Assert;

/**
 * Utility methods for AOP proxy factories.
 * Mainly for internal use within the AOP framework.
 *
 * <p>See {@link org.springframework.aop.support.AopUtils} for a collection of
 * generic AOP utility methods which do not depend on AOP framework internals.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see org.springframework.aop.support.AopUtils
 */
public abstract class AopProxyUtils {

	/**
	 * Determine the ultimate target class of the given bean instance, traversing
	 * not only a top-level proxy but any number of nested proxies as well &mdash;
	 * as long as possible without side effects, that is, just for singleton targets.
	 * @param candidate the instance to check (might be an AOP proxy)
	 * @return the ultimate target class (or the plain class of the given
	 * object as fallback; never {@code null})
	 * @see org.springframework.aop.TargetClassAware#getTargetClass()
	 * @see Advised#getTargetSource()
	 */
	public static Class<?> ultimateTargetClass(Object candidate) {
		Assert.notNull(candidate, "Candidate object must not be null");
		Object current = candidate;
		Class<?> result = null;
		while (current instanceof TargetClassAware) {
			result = ((TargetClassAware) current).getTargetClass();
			Object nested = null;
			if (current instanceof Advised) {
				TargetSource targetSource = ((Advised) current).getTargetSource();
				if (targetSource instanceof SingletonTargetSource) {
					nested = ((SingletonTargetSource) targetSource).getTarget();
				}
			}
			current = nested;
		}
		if (result == null) {
			result = (AopUtils.isCglibProxy(candidate) ? candidate.getClass().getSuperclass() : candidate.getClass());
		}
		return result;
	}

	/**
	 * Determine the complete set of interfaces to proxy for the given AOP configuration.
	 * <p>This will always add the {@link Advised} interface unless the AdvisedSupport's
	 * {@link AdvisedSupport#setOpaque "opaque"} flag is on. Always adds the
	 * {@link org.springframework.aop.SpringProxy} marker interface.
	 * @return the complete set of interfaces to proxy
	 * @see Advised
	 * @see org.springframework.aop.SpringProxy
	 */
	public static Class<?>[] completeProxiedInterfaces(AdvisedSupport advised) {
		Class<?>[] specifiedInterfaces = advised.getProxiedInterfaces();
		if (specifiedInterfaces.length == 0) {
			// No user-specified interfaces: check whether target class is an interface.
			Class<?> targetClass = advised.getTargetClass();
			if (targetClass != null) {
				if (targetClass.isInterface()) {
					advised.setInterfaces(targetClass);
				}
				else if (Proxy.isProxyClass(targetClass)) {
					advised.setInterfaces(targetClass.getInterfaces());
				}
				specifiedInterfaces = advised.getProxiedInterfaces();
			}
		}
		boolean addSpringProxy = !advised.isInterfaceProxied(SpringProxy.class);
		boolean addAdvised = !advised.isOpaque() && !advised.isInterfaceProxied(Advised.class);
		int nonUserIfcCount = 0;
		if (addSpringProxy) {
			nonUserIfcCount++;
		}
		if (addAdvised) {
			nonUserIfcCount++;
		}
		Class<?>[] proxiedInterfaces = new Class<?>[specifiedInterfaces.length + nonUserIfcCount];
		System.arraycopy(specifiedInterfaces, 0, proxiedInterfaces, 0, specifiedInterfaces.length);
		if (addSpringProxy) {
			proxiedInterfaces[specifiedInterfaces.length] = SpringProxy.class;
		}
		if (addAdvised) {
			proxiedInterfaces[proxiedInterfaces.length - 1] = Advised.class;
		}
		return proxiedInterfaces;
	}

	/**
	 * Extract the user-specified interfaces that the given proxy implements,
	 * i.e. all non-Advised interfaces that the proxy implements.
	 * @param proxy the proxy to analyze (usually a JDK dynamic proxy)
	 * @return all user-specified interfaces that the proxy implements,
	 * in the original order (never {@code null} or empty)
	 * @see Advised
	 */
	public static Class<?>[] proxiedUserInterfaces(Object proxy) {
		Class<?>[] proxyInterfaces = proxy.getClass().getInterfaces();
		int nonUserIfcCount = 0;
		if (proxy instanceof SpringProxy) {
			nonUserIfcCount++;
		}
		if (proxy instanceof Advised) {
			nonUserIfcCount++;
		}
		Class<?>[] userInterfaces = new Class<?>[proxyInterfaces.length - nonUserIfcCount];
		System.arraycopy(proxyInterfaces, 0, userInterfaces, 0, userInterfaces.length);
		Assert.notEmpty(userInterfaces, "JDK proxy must implement one or more interfaces");
		return userInterfaces;
	}

	/**
	 * Check equality of the proxies behind the given AdvisedSupport objects.
	 * Not the same as equality of the AdvisedSupport objects:
	 * rather, equality of interfaces, advisors and target sources.
	 */
	public static boolean equalsInProxy(AdvisedSupport a, AdvisedSupport b) {
		return (a == b ||
				(equalsProxiedInterfaces(a, b) && equalsAdvisors(a, b) && a.getTargetSource().equals(b.getTargetSource())));
	}

	/**
	 * Check equality of the proxied interfaces behind the given AdvisedSupport objects.
	 */
	public static boolean equalsProxiedInterfaces(AdvisedSupport a, AdvisedSupport b) {
		return Arrays.equals(a.getProxiedInterfaces(), b.getProxiedInterfaces());
	}

	/**
	 * Check equality of the advisors behind the given AdvisedSupport objects.
	 */
	public static boolean equalsAdvisors(AdvisedSupport a, AdvisedSupport b) {
		return Arrays.equals(a.getAdvisors(), b.getAdvisors());
	}

}
