/*
 *      Copyright (c) 2018-2028, Chill Zhuang All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice,
 *  this list of conditions and the following disclaimer.
 *  Redistributions in binary form must reproduce the above copyright
 *  notice, this list of conditions and the following disclaimer in the
 *  documentation and/or other materials provided with the distribution.
 *  Neither the name of the dreamlu.net developer nor the names of its
 *  contributors may be used to endorse or promote products derived from
 *  this software without specific prior written permission.
 *  Author: Chill 庄骞 (smallchill@163.com)
 */
package org.springblade.core.secure.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.reflect.MethodSignature;
import org.springblade.core.secure.annotation.PreAuth;
import org.springblade.core.secure.auth.AuthFun;
import org.springblade.core.secure.exception.SecureException;
import org.springblade.core.tool.api.ResultCode;
import org.springblade.core.tool.utils.ClassUtil;
import org.springblade.core.tool.utils.StringUtil;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.core.MethodParameter;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.lang.NonNull;

import java.lang.reflect.Method;

/**
 * AOP 鉴权
 *
 * @author Chill
 */
@Aspect
public class AuthAspect implements ApplicationContextAware {

	/**
	 * 表达式处理
	 */
	private static final ExpressionParser EXPRESSION_PARSER = new SpelExpressionParser();

	/**
	 * 切 方法 和 类上的 @PreAuth 注解
	 *
	 * @param point 切点
	 * @return Object
	 * @throws Throwable 没有权限的异常
	 */
	@Around(
		"@annotation(org.springblade.core.secure.annotation.PreAuth) || " +
			"@within(org.springblade.core.secure.annotation.PreAuth)"
	)
	public Object preAuth(ProceedingJoinPoint point) throws Throwable {
		if (handleAuth(point)) {
			return point.proceed();
		}
		throw new SecureException(ResultCode.UN_AUTHORIZED);
	}

	/**
	 * 处理权限
	 *
	 * @param point 切点
	 */
	private boolean handleAuth(ProceedingJoinPoint point) {
		MethodSignature ms = (MethodSignature) point.getSignature();
		Method method = ms.getMethod();
		// 读取权限注解，优先方法上，没有则读取类
		PreAuth preAuth = ClassUtil.getAnnotation(method, PreAuth.class);
		// 判断表达式
		String condition = preAuth.value();
		if (StringUtil.isNotBlank(condition)) {
			Expression expression = EXPRESSION_PARSER.parseExpression(condition);
			// 方法参数值
			Object[] args = point.getArgs();
			StandardEvaluationContext context = getEvaluationContext(method, args);
			return expression.getValue(context, Boolean.class);
		}
		return false;
	}

	/**
	 * 获取方法上的参数
	 *
	 * @param method 方法
	 * @param args   变量
	 * @return {SimpleEvaluationContext}
	 */
	private StandardEvaluationContext getEvaluationContext(Method method, Object[] args) {
		// 初始化Sp el表达式上下文，并设置 AuthFun
		StandardEvaluationContext context = new StandardEvaluationContext(new AuthFun());
		// 设置表达式支持spring bean
		context.setBeanResolver(new BeanFactoryResolver(applicationContext));
		for (int i = 0; i < args.length; i++) {
			// 读取方法参数
			MethodParameter methodParam = ClassUtil.getMethodParameter(method, i);
			// 设置方法 参数名和值 为sp el变量
			context.setVariable(methodParam.getParameterName(), args[i]);
		}
		return context;
	}

	private ApplicationContext applicationContext;

	@Override
	public void setApplicationContext(@NonNull ApplicationContext applicationContext) throws BeansException {
		this.applicationContext = applicationContext;
	}

}