/*
 * Copyright 2012-2020 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.boot.security.reactive;

import java.util.function.Supplier;

import reactor.core.publisher.Mono;

import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.security.web.server.util.matcher.ServerWebExchangeMatcher;
import org.springframework.util.Assert;
import org.springframework.web.server.ServerWebExchange;

ApplicationContext backed ServerWebExchangeMatcher. Can work directly with the ApplicationContext, obtain an existing bean or create a new bean that is autowired in the usual way. 
Author:
Madhura Bhave
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 ServerWebExchangeMatcher}. 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 Madhura Bhave
 * @since 2.0.0
 */
public abstract class ApplicationContextServerWebExchangeMatcher<C> implements ServerWebExchangeMatcher {

	private final Class<? extends C> contextClass;

	private volatile Supplier<C> context;

	private final Object contextLock = new Object();

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

	@Override
	public final Mono<MatchResult> matches(ServerWebExchange exchange) {
		if (ignoreApplicationContext(exchange.getApplicationContext())) {
			return MatchResult.notMatch();
		}
		return matches(exchange, getContext(exchange));
	}

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

	
Returns if the ApplicationContext 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:
applicationContext – the candidate application context
Returns:
if the application context should be ignored
Since:
2.2.5/**
	 * Returns if the {@link ApplicationContext} 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(ServerWebExchange) matches} method will return {@code false}.
	 * @param applicationContext the candidate application context
	 * @return if the application context should be ignored
	 * @since 2.2.5
	 */
	protected boolean ignoreApplicationContext(ApplicationContext applicationContext) {
		return false;
	}

	protected Supplier<C> getContext(ServerWebExchange exchange) {
		if (this.context == null) {
			synchronized (this.contextLock) {
				if (this.context == null) {
					Supplier<C> createdContext = createContext(exchange);
					initialized(createdContext);
					this.context = createdContext;
				}
			}
		}
		return this.context;
	}

	
Called once the context has been initialized.
Params:
context – a supplier for the initialized context (may throw an exception)/**
	 * Called once the context has been initialized.
	 * @param context a supplier for the initialized context (may throw an exception)
	 */
	protected void initialized(Supplier<C> context) {
	}

	@SuppressWarnings("unchecked")
	private Supplier<C> createContext(ServerWebExchange exchange) {
		ApplicationContext context = exchange.getApplicationContext();
		Assert.state(context != null, "No ApplicationContext found on ServerWebExchange.");
		if (this.contextClass.isInstance(context)) {
			return () -> (C) context;
		}
		return () -> context.getBean(this.contextClass);
	}

}