/*
 * Copyright (C) 2018 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
 *
 *      http://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 com.alibaba.cloud.sentinel;

import java.util.Collections;
import java.util.List;
import java.util.Optional;

import javax.annotation.PostConstruct;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.http.codec.ServerCodecConfigurer;
import org.springframework.web.reactive.result.view.ViewResolver;

import com.alibaba.csp.sentinel.adapter.reactor.SentinelReactorTransformer;
import com.alibaba.csp.sentinel.adapter.spring.webflux.SentinelWebFluxFilter;
import com.alibaba.csp.sentinel.adapter.spring.webflux.callback.BlockRequestHandler;
import com.alibaba.csp.sentinel.adapter.spring.webflux.callback.WebFluxCallbackManager;
import com.alibaba.csp.sentinel.adapter.spring.webflux.exception.SentinelBlockExceptionHandler;

/**
 * @author <a href="mailto:fangjian0423@gmail.com">Jim</a>
 */
@Configuration
@ConditionalOnWebApplication(type = Type.REACTIVE)
@ConditionalOnClass(SentinelReactorTransformer.class)
@ConditionalOnProperty(name = "spring.cloud.sentinel.enabled", matchIfMissing = true)
@EnableConfigurationProperties(SentinelProperties.class)
public class SentinelWebFluxAutoConfiguration {

	private static final Logger log = LoggerFactory
			.getLogger(SentinelWebFluxAutoConfiguration.class);

	private final List<ViewResolver> viewResolvers;
	private final ServerCodecConfigurer serverCodecConfigurer;

	@Autowired
	private Optional<BlockRequestHandler> blockRequestHandler;

	public SentinelWebFluxAutoConfiguration(
			ObjectProvider<List<ViewResolver>> viewResolvers,
			ServerCodecConfigurer serverCodecConfigurer) {
		this.viewResolvers = viewResolvers.getIfAvailable(Collections::emptyList);
		this.serverCodecConfigurer = serverCodecConfigurer;
	}

	@PostConstruct
	public void init() {
		blockRequestHandler.ifPresent(WebFluxCallbackManager::setBlockHandler);
	}

	@Bean
	@Order(-2)
	@ConditionalOnProperty(name = "spring.cloud.sentinel.filter.enabled", matchIfMissing = true)
	public SentinelBlockExceptionHandler sentinelBlockExceptionHandler() {
		return new SentinelBlockExceptionHandler(viewResolvers, serverCodecConfigurer);
	}

	@Bean
	@Order(-1)
	@ConditionalOnProperty(name = "spring.cloud.sentinel.filter.enabled", matchIfMissing = true)
	public SentinelWebFluxFilter sentinelWebFluxFilter() {
		log.info("[Sentinel Starter] register Sentinel SentinelWebFluxFilter");
		return new SentinelWebFluxFilter();
	}

}