/*
 * Copyright 2002-2020 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
 *
 *      https://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.aspectj;

import java.util.List;

import org.springframework.aop.Advisor;
import org.springframework.aop.PointcutAdvisor;
import org.springframework.aop.interceptor.ExposeInvocationInterceptor;
import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;

Utility methods for working with AspectJ proxies.
Author:
Rod Johnson, Ramnivas Laddad, Juergen Hoeller
Since:
2.0/**
 * Utility methods for working with AspectJ proxies.
 *
 * @author Rod Johnson
 * @author Ramnivas Laddad
 * @author Juergen Hoeller
 * @since 2.0
 */
public abstract class AspectJProxyUtils {

	
Add special advisors if necessary to work with a proxy chain that contains AspectJ advisors: concretely, ExposeInvocationInterceptor at the beginning of the list. 
This will expose the current Spring AOP invocation (necessary for some AspectJ pointcut
matching) and make available the current AspectJ JoinPoint. The call will have no effect
if there are no AspectJ advisors in the advisor chain.
Params:
advisors – the advisors available
Returns:
true if an ExposeInvocationInterceptor was added to the list, otherwise false/**
	 * Add special advisors if necessary to work with a proxy chain that contains AspectJ advisors:
	 * concretely, {@link ExposeInvocationInterceptor} at the beginning of the list.
	 * <p>This will expose the current Spring AOP invocation (necessary for some AspectJ pointcut
	 * matching) and make available the current AspectJ JoinPoint. The call will have no effect
	 * if there are no AspectJ advisors in the advisor chain.
	 * @param advisors the advisors available
	 * @return {@code true} if an {@link ExposeInvocationInterceptor} was added to the list,
	 * otherwise {@code false}
	 */
	public static boolean makeAdvisorChainAspectJCapableIfNecessary(List<Advisor> advisors) {
		// Don't add advisors to an empty list; may indicate that proxying is just not required
		if (!advisors.isEmpty()) {
			boolean foundAspectJAdvice = false;
			for (Advisor advisor : advisors) {
				// Be careful not to get the Advice without a guard, as this might eagerly
				// instantiate a non-singleton AspectJ aspect...
				if (isAspectJAdvice(advisor)) {
					foundAspectJAdvice = true;
					break;
				}
			}
			if (foundAspectJAdvice && !advisors.contains(ExposeInvocationInterceptor.ADVISOR)) {
				advisors.add(0, ExposeInvocationInterceptor.ADVISOR);
				return true;
			}
		}
		return false;
	}

	
Determine whether the given Advisor contains an AspectJ advice.
Params:
advisor – the Advisor to check/**
	 * Determine whether the given Advisor contains an AspectJ advice.
	 * @param advisor the Advisor to check
	 */
	private static boolean isAspectJAdvice(Advisor advisor) {
		return (advisor instanceof InstantiationModelAwarePointcutAdvisor ||
				advisor.getAdvice() instanceof AbstractAspectJAdvice ||
				(advisor instanceof PointcutAdvisor &&
						((PointcutAdvisor) advisor).getPointcut() instanceof AspectJExpressionPointcut));
	}

	static boolean isVariableName(@Nullable String name) {
		if (!StringUtils.hasLength(name)) {
			return false;
		}
		if (!Character.isJavaIdentifierStart(name.charAt(0))) {
			return false;
		}
		for (int i = 1; i < name.length(); i++) {
			if (!Character.isJavaIdentifierPart(name.charAt(i))) {
				return false;
			}
		}
		return true;
	}

}