/*
 * Copyright 2012-2024 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.autoconfigure.web.servlet;

import java.util.Arrays;
import java.util.List;

import jakarta.servlet.MultipartConfigElement;
import jakarta.servlet.ServletRegistration;

import org.springframework.beans.factory.ObjectProvider;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.boot.autoconfigure.AutoConfiguration;
import org.springframework.boot.autoconfigure.AutoConfigureOrder;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionMessage;
import org.springframework.boot.autoconfigure.condition.ConditionMessage.Style;
import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.servlet.DispatcherServlet;

/**
 * {@link EnableAutoConfiguration Auto-configuration} for the Spring
 * {@link DispatcherServlet}. Should work for a standalone application where an embedded
 * web server is already present and also for a deployable application using
 * {@link SpringBootServletInitializer}.
 *
 * @author Phillip Webb
 * @author Dave Syer
 * @author Stephane Nicoll
 * @author Brian Clozel
 * @since 2.0.0
 */
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@AutoConfiguration(after = ServletWebServerFactoryAutoConfiguration.class)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass(DispatcherServlet.class)
public class DispatcherServletAutoConfiguration {

	/**
	 * The bean name for a DispatcherServlet that will be mapped to the root URL "/".
	 */
	public static final String DEFAULT_DISPATCHER_SERVLET_BEAN_NAME = "dispatcherServlet";

	/**
	 * The bean name for a ServletRegistrationBean for the DispatcherServlet "/".
	 */
	public static final String DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME = "dispatcherServletRegistration";

	@Configuration(proxyBeanMethods = false)
	@Conditional(DefaultDispatcherServletCondition.class)
	@ConditionalOnClass(ServletRegistration.class)
	@EnableConfigurationProperties(WebMvcProperties.class)
	protected static class DispatcherServletConfiguration {

		@Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
		public DispatcherServlet dispatcherServlet(WebMvcProperties webMvcProperties) {
			DispatcherServlet dispatcherServlet = new DispatcherServlet();
			dispatcherServlet.setDispatchOptionsRequest(webMvcProperties.isDispatchOptionsRequest());
			dispatcherServlet.setDispatchTraceRequest(webMvcProperties.isDispatchTraceRequest());
			dispatcherServlet.setPublishEvents(webMvcProperties.isPublishRequestHandledEvents());
			dispatcherServlet.setEnableLoggingRequestDetails(webMvcProperties.isLogRequestDetails());
			return dispatcherServlet;
		}

		@Bean
		@ConditionalOnBean(MultipartResolver.class)
		@ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
		public MultipartResolver multipartResolver(MultipartResolver resolver) {
			// Detect if the user has created a MultipartResolver but named it incorrectly
			return resolver;
		}

	}

	@Configuration(proxyBeanMethods = false)
	@Conditional(DispatcherServletRegistrationCondition.class)
	@ConditionalOnClass(ServletRegistration.class)
	@EnableConfigurationProperties(WebMvcProperties.class)
	@Import(DispatcherServletConfiguration.class)
	protected static class DispatcherServletRegistrationConfiguration {

		@Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
		@ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
		public DispatcherServletRegistrationBean dispatcherServletRegistration(DispatcherServlet dispatcherServlet,
				WebMvcProperties webMvcProperties, ObjectProvider<MultipartConfigElement> multipartConfig) {
			DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet,
					webMvcProperties.getServlet().getPath());
			registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
			registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());
			multipartConfig.ifAvailable(registration::setMultipartConfig);
			return registration;
		}

	}

	@Order(Ordered.LOWEST_PRECEDENCE - 10)
	private static final class DefaultDispatcherServletCondition extends SpringBootCondition {

		@Override
		public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
			ConditionMessage.Builder message = ConditionMessage.forCondition("Default DispatcherServlet");
			ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
			List<String> dispatchServletBeans = Arrays
				.asList(beanFactory.getBeanNamesForType(DispatcherServlet.class, false, false));
			if (dispatchServletBeans.contains(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
				return ConditionOutcome
					.noMatch(message.found("dispatcher servlet bean").items(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
			}
			if (beanFactory.containsBean(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
				return ConditionOutcome
					.noMatch(message.found("non dispatcher servlet bean").items(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
			}
			if (dispatchServletBeans.isEmpty()) {
				return ConditionOutcome.match(message.didNotFind("dispatcher servlet beans").atAll());
			}
			return ConditionOutcome.match(message.found("dispatcher servlet bean", "dispatcher servlet beans")
				.items(Style.QUOTE, dispatchServletBeans)
				.append("and none is named " + DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
		}

	}

	@Order(Ordered.LOWEST_PRECEDENCE - 10)
	private static final class DispatcherServletRegistrationCondition extends SpringBootCondition {

		@Override
		public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
			ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
			ConditionOutcome outcome = checkDefaultDispatcherName(beanFactory);
			if (!outcome.isMatch()) {
				return outcome;
			}
			return checkServletRegistration(beanFactory);
		}

		private ConditionOutcome checkDefaultDispatcherName(ConfigurableListableBeanFactory beanFactory) {
			boolean containsDispatcherBean = beanFactory.containsBean(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
			if (!containsDispatcherBean) {
				return ConditionOutcome.match();
			}
			List<String> servlets = Arrays
				.asList(beanFactory.getBeanNamesForType(DispatcherServlet.class, false, false));
			if (!servlets.contains(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)) {
				return ConditionOutcome.noMatch(
						startMessage().found("non dispatcher servlet").items(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME));
			}
			return ConditionOutcome.match();
		}

		private ConditionOutcome checkServletRegistration(ConfigurableListableBeanFactory beanFactory) {
			ConditionMessage.Builder message = startMessage();
			List<String> registrations = Arrays
				.asList(beanFactory.getBeanNamesForType(ServletRegistrationBean.class, false, false));
			boolean containsDispatcherRegistrationBean = beanFactory
				.containsBean(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME);
			if (registrations.isEmpty()) {
				if (containsDispatcherRegistrationBean) {
					return ConditionOutcome.noMatch(message.found("non servlet registration bean")
						.items(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
				}
				return ConditionOutcome.match(message.didNotFind("servlet registration bean").atAll());
			}
			if (registrations.contains(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)) {
				return ConditionOutcome.noMatch(message.found("servlet registration bean")
					.items(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
			}
			if (containsDispatcherRegistrationBean) {
				return ConditionOutcome.noMatch(message.found("non servlet registration bean")
					.items(DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
			}
			return ConditionOutcome.match(message.found("servlet registration beans")
				.items(Style.QUOTE, registrations)
				.append("and none is named " + DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME));
		}

		private ConditionMessage.Builder startMessage() {
			return ConditionMessage.forCondition("DispatcherServlet Registration");
		}

	}

}
