/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.security.access.expression.method

import groovy.transform.CompileStatic

import org.aopalliance.intercept.MethodInvocation

import org.springframework.expression.EvaluationContext
import org.springframework.expression.ExpressionParser
import org.springframework.expression.spel.standard.SpelExpressionParser
import org.springframework.expression.spel.support.StandardEvaluationContext
import org.springframework.security.access.AccessDeniedException
import org.springframework.security.access.PermissionEvaluator
import org.springframework.security.access.prepost.ExpressionBasedAnnotationConfigAttribute
import org.springframework.security.core.Authentication

@CompileStatic
class ExpressionBasedPostInvocationAdvice {

	final DefaultMethodSecurityExpressionHandler expressionHandler

	private final ExpressionParser expressionParser = new SpelExpressionParser()

	ExpressionBasedPostInvocationAdvice(DefaultMethodSecurityExpressionHandler expressionHandler) {
		this.expressionHandler = expressionHandler
	}

	Object after(Authentication authentication, MethodInvocation invocation, Object attribute, Object returnedObject) {
		if (!(attribute instanceof ExpressionBasedAnnotationConfigAttribute)) {
			return returnedObject
		}

		def expressionAttribute = attribute as ExpressionBasedAnnotationConfigAttribute
		def filteredObject = applyPostFilter(authentication, expressionAttribute, returnedObject)
		applyPostAuthorize(authentication, expressionAttribute, filteredObject)
		filteredObject
	}

	private Object applyPostFilter(
			Authentication authentication,
			ExpressionBasedAnnotationConfigAttribute expressionAttribute,
			Object returnedObject
	) {
		if (expressionAttribute.postFilterExpression == null || !(returnedObject instanceof Collection)) {
			return returnedObject
		}

		def collection = returnedObject as Collection<?>
		List<Object> filtered = []
		for (def candidate : collection) {
			def context = createEvaluationContext(authentication, candidate, returnedObject)
			def allowed = expressionParser.parseExpression(expressionAttribute.postFilterExpression)
					.getValue(context, Boolean)
			if (Boolean.TRUE == allowed) {
				filtered << candidate
			}
		}
		filtered
	}

	private void applyPostAuthorize(
			Authentication authentication,
			ExpressionBasedAnnotationConfigAttribute expressionAttribute,
			Object returnedObject
	) {
		if (expressionAttribute.postAuthorizeExpression == null) {
			return
		}

		def context = createEvaluationContext(authentication, null, returnedObject)
		def allowed = expressionParser.parseExpression(expressionAttribute.postAuthorizeExpression)
				.getValue(context, Boolean)
		if (Boolean.TRUE != allowed) {
			throw new AccessDeniedException('Access is denied')
		}
	}

	private EvaluationContext createEvaluationContext(Authentication authentication, Object filterObject, Object returnObject) {
		def permissionEvaluator = resolvePermissionEvaluator()
		def root = new MethodSecurityExpressionRoot(authentication, permissionEvaluator).tap {
			it.filterObject = filterObject
			it.returnObject = returnObject
		}
		new StandardEvaluationContext(root)
	}

	private PermissionEvaluator resolvePermissionEvaluator() {
		if (expressionHandler == null) {
			return null
		}

		def current = expressionHandler.class
		while (current != null) {
			try {
				def method = current.getDeclaredMethod('getPermissionEvaluator').tap {
					accessible = true
				}
				return (PermissionEvaluator) method.invoke(expressionHandler)
			}
			catch (NoSuchMethodException ignored) {
			}

			try {
				def field = current.getDeclaredField('permissionEvaluator').tap {
					accessible = true
				}
				return (PermissionEvaluator) field.get(expressionHandler)
			}
			catch (NoSuchFieldException ignored) {
			}

			current = current.superclass
		}

		return null
	}

	private static class MethodSecurityExpressionRoot {

		final Authentication authentication
		final PermissionEvaluator permissionEvaluator
		final Object read = 1
		final Object write = 2
		final Object create = 4
		final Object delete = 8
		final Object admin = 16

		Object filterObject
		Object returnObject

		MethodSecurityExpressionRoot(Authentication authentication, PermissionEvaluator permissionEvaluator) {
			this.authentication = authentication
			this.permissionEvaluator = permissionEvaluator
		}

		boolean hasPermission(Object target, Object permission) {
			permissionEvaluator != null && authentication != null &&
					permissionEvaluator.hasPermission(authentication, target, permission)
		}

		boolean hasPermission(Object targetId, String targetType, Object permission) {
			permissionEvaluator != null && authentication != null &&
					permissionEvaluator.hasPermission(authentication, (Serializable) targetId, targetType, permission)
		}
	}
}
