/*
 * Copyright 2012-2017 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 org.springframework.boot.actuate.autoconfigure.web.server;

import org.springframework.beans.factory.SmartInitializingSingleton;
import org.springframework.boot.actuate.autoconfigure.web.ManagementContextFactory;
import org.springframework.boot.actuate.autoconfigure.web.ManagementContextType;
import org.springframework.boot.autoconfigure.AutoConfigureOrder;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration;
import org.springframework.boot.context.event.ApplicationFailedEvent;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.boot.web.reactive.context.ConfigurableReactiveWebApplicationContext;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.core.Ordered;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.Environment;
import org.springframework.core.env.PropertySource;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.util.Assert;
import org.springframework.web.context.ConfigurableWebApplicationContext;

/**
 * {@link EnableAutoConfiguration Auto-configuration} for the management context. If the
 * {@code management.port} is the same as the {@code server.port} the management context
 * will be the same as the main application context. If the {@code management.port} is
 * different to the {@code server.port} the management context will be a separate context
 * that has the main application context as its parent.
 *
 * @author Andy Wilkinson
 * @since 2.0.0
 */
@Configuration
@AutoConfigureOrder(Ordered.LOWEST_PRECEDENCE)
@EnableConfigurationProperties(ManagementServerProperties.class)
public class ManagementContextAutoConfiguration {

	@Configuration
	@ConditionalOnManagementPort(ManagementPortType.SAME)
	static class SameManagementContextConfiguration
			implements SmartInitializingSingleton {

		private final Environment environment;

		SameManagementContextConfiguration(Environment environment) {
			this.environment = environment;
		}

		@Override
		public void afterSingletonsInstantiated() {
			verifySslConfiguration();
			if (this.environment instanceof ConfigurableEnvironment) {
				addLocalManagementPortPropertyAlias(
						(ConfigurableEnvironment) this.environment);
			}
		}

		private void verifySslConfiguration() {
			Boolean enabled = this.environment.getProperty("management.ssl.enabled",
					Boolean.class, false);
			Assert.state(!enabled,
					"Management-specific SSL cannot be configured as the management "
							+ "server is not listening on a separate port");
		}

		/**
		 * Add an alias for 'local.management.port' that actually resolves using
		 * 'local.server.port'.
		 * @param environment the environment
		 */
		private void addLocalManagementPortPropertyAlias(
				ConfigurableEnvironment environment) {
			environment.getPropertySources()
					.addLast(new PropertySource<Object>("Management Server") {

						@Override
						public Object getProperty(String name) {
							if ("local.management.port".equals(name)) {
								return environment.getProperty("local.server.port");
							}
							return null;
						}

					});
		}

		@EnableManagementContext(ManagementContextType.SAME)
		static class EnableSameManagementContextConfiguration {

		}

	}

	@Configuration
	@ConditionalOnManagementPort(ManagementPortType.DIFFERENT)
	static class DifferentManagementContextConfiguration
			implements SmartInitializingSingleton {

		private final ApplicationContext applicationContext;

		private final ManagementContextFactory managementContextFactory;

		DifferentManagementContextConfiguration(ApplicationContext applicationContext,
				ManagementContextFactory managementContextFactory) {
			this.applicationContext = applicationContext;
			this.managementContextFactory = managementContextFactory;
		}

		@Override
		public void afterSingletonsInstantiated() {
			ConfigurableApplicationContext managementContext = this.managementContextFactory
					.createManagementContext(this.applicationContext,
							EnableChildManagementContextConfiguration.class,
							PropertyPlaceholderAutoConfiguration.class);
			setNamespaceIfPossible(managementContext);
			managementContext.setId(this.applicationContext.getId() + ":management");
			setClassLoaderIfPossible(managementContext);
			CloseManagementContextListener.addIfPossible(this.applicationContext,
					managementContext);
			managementContext.refresh();
		}

		private void setClassLoaderIfPossible(ConfigurableApplicationContext child) {
			if (child instanceof DefaultResourceLoader) {
				((AbstractApplicationContext) child)
						.setClassLoader(this.applicationContext.getClassLoader());
			}
		}

		private void setNamespaceIfPossible(ConfigurableApplicationContext child) {
			if (child instanceof ConfigurableReactiveWebApplicationContext) {
				((ConfigurableReactiveWebApplicationContext) child)
						.setNamespace("management");
			}
			else if (child instanceof ConfigurableWebApplicationContext) {
				((ConfigurableWebApplicationContext) child).setNamespace("management");
			}
		}

	}

	/**
	 * {@link ApplicationListener} to propagate the {@link ContextClosedEvent} and
	 * {@link ApplicationFailedEvent} from a parent to a child.
	 */
	private static class CloseManagementContextListener
			implements ApplicationListener<ApplicationEvent> {

		private final ApplicationContext parentContext;

		private final ConfigurableApplicationContext childContext;

		CloseManagementContextListener(ApplicationContext parentContext,
				ConfigurableApplicationContext childContext) {
			this.parentContext = parentContext;
			this.childContext = childContext;
		}

		@Override
		public void onApplicationEvent(ApplicationEvent event) {
			if (event instanceof ContextClosedEvent) {
				onContextClosedEvent((ContextClosedEvent) event);
			}
			if (event instanceof ApplicationFailedEvent) {
				onApplicationFailedEvent((ApplicationFailedEvent) event);
			}
		}

		private void onContextClosedEvent(ContextClosedEvent event) {
			propagateCloseIfNecessary(event.getApplicationContext());
		}

		private void onApplicationFailedEvent(ApplicationFailedEvent event) {
			propagateCloseIfNecessary(event.getApplicationContext());
		}

		private void propagateCloseIfNecessary(ApplicationContext applicationContext) {
			if (applicationContext == this.parentContext) {
				this.childContext.close();
			}
		}

		public static void addIfPossible(ApplicationContext parentContext,
				ConfigurableApplicationContext childContext) {
			if (parentContext instanceof ConfigurableApplicationContext) {
				add((ConfigurableApplicationContext) parentContext, childContext);
			}
		}

		private static void add(ConfigurableApplicationContext parentContext,
				ConfigurableApplicationContext childContext) {
			parentContext.addApplicationListener(
					new CloseManagementContextListener(parentContext, childContext));
		}

	}

}
