/*
 * Copyright 2012-2019 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.boot.security.servlet;

import java.util.function.Supplier;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.security.web.util.matcher.RequestMatcher;
import org.springframework.util.Assert;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

ApplicationContext backed RequestMatcher. Can work directly with the ApplicationContext, obtain an existing bean or create a new bean that is autowired in the usual way. 
Author:
Phillip Webb
Type parameters:
<C> – the type of the context that the match method actually needs to use. Can be an ApplicationContext or a class of an 
existing bean.
Since:
2.0.0/**
 * {@link ApplicationContext} backed {@link RequestMatcher}. Can work directly with the
 * {@link ApplicationContext}, obtain an existing bean or
 * {@link AutowireCapableBeanFactory#createBean(Class, int, boolean) create a new bean}
 * that is autowired in the usual way.
 *
 * @param <C> the type of the context that the match method actually needs to use. Can be
 * an {@link ApplicationContext} or a class of an {@link ApplicationContext#getBean(Class)
 * existing bean}.
 * @author Phillip Webb
 * @since 2.0.0
 */
public abstract class ApplicationContextRequestMatcher<C> implements RequestMatcher {

	private final Class<? extends C> contextClass;

	private volatile boolean initialized;

	private final Object initializeLock = new Object();

	public ApplicationContextRequestMatcher(Class<? extends C> contextClass) {
		Assert.notNull(contextClass, "Context class must not be null");
		this.contextClass = contextClass;
	}

	@Override
	public final boolean matches(HttpServletRequest request) {
		WebApplicationContext webApplicationContext = WebApplicationContextUtils
				.getRequiredWebApplicationContext(request.getServletContext());
		if (ignoreApplicationContext(webApplicationContext)) {
			return false;
		}
		Supplier<C> context = () -> getContext(webApplicationContext);
		if (!this.initialized) {
			synchronized (this.initializeLock) {
				if (!this.initialized) {
					initialized(context);
					this.initialized = true;
				}
			}
		}
		return matches(request, context);
	}

	@SuppressWarnings("unchecked")
	private C getContext(WebApplicationContext webApplicationContext) {
		if (this.contextClass.isInstance(webApplicationContext)) {
			return (C) webApplicationContext;
		}
		return webApplicationContext.getBean(this.contextClass);
	}

	
Returns if the WebApplicationContext should be ignored and not used for matching. If this method returns true then the context will not be used and the matches method will return false. 
Params:
webApplicationContext – the candidate web application context
Returns:
if the application context should be ignored
Since:
2.1.8/**
	 * Returns if the {@link WebApplicationContext} should be ignored and not used for
	 * matching. If this method returns {@code true} then the context will not be used and
	 * the {@link #matches(HttpServletRequest) matches} method will return {@code false}.
	 * @param webApplicationContext the candidate web application context
	 * @return if the application context should be ignored
	 * @since 2.1.8
	 */
	protected boolean ignoreApplicationContext(WebApplicationContext webApplicationContext) {
		return false;
	}

	
Method that can be implemented by subclasses that wish to initialize items the first time that the matcher is called. This method will be called only once and only if ignoreApplicationContext(WebApplicationContext) returns false. Note that the supplied context will be based on the first request sent to the matcher.
Params:
context – a supplier for the initialized context (may throw an exception)
See Also:
ignoreApplicationContext(WebApplicationContext)/**
	 * Method that can be implemented by subclasses that wish to initialize items the
	 * first time that the matcher is called. This method will be called only once and
	 * only if {@link #ignoreApplicationContext(WebApplicationContext)} returns
	 * {@code false}. Note that the supplied context will be based on the
	 * <strong>first</strong> request sent to the matcher.
	 * @param context a supplier for the initialized context (may throw an exception)
	 * @see #ignoreApplicationContext(WebApplicationContext)
	 */
	protected void initialized(Supplier<C> context) {
	}

	
Decides whether the rule implemented by the strategy matches the supplied request.
Params:
request – the source request
context – a supplier for the initialized context (may throw an exception)
Returns:
if the request matches/**
	 * Decides whether the rule implemented by the strategy matches the supplied request.
	 * @param request the source request
	 * @param context a supplier for the initialized context (may throw an exception)
	 * @return if the request matches
	 */
	protected abstract boolean matches(HttpServletRequest request, Supplier<C> context);

}