/*
 * Copyright 2002-2016 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.security.config.annotation.web.configuration;

import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.aop.TargetSource;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.target.LazyInitTargetSource;
import org.springframework.beans.FatalBeanException;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.core.annotation.Order;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.AuthenticationTrustResolver;
import org.springframework.security.authentication.AuthenticationTrustResolverImpl;
import org.springframework.security.authentication.DefaultAuthenticationEventPublisher;
import org.springframework.security.config.annotation.ObjectPostProcessor;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.authentication.configuration.AuthenticationConfiguration;
import org.springframework.security.config.annotation.web.WebSecurityConfigurer;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.builders.WebSecurity;
import org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer;
import org.springframework.security.config.annotation.web.configurers.DefaultLoginPageConfigurer;
import org.springframework.security.config.annotation.web.configurers.SecurityContextConfigurer;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.security.web.access.intercept.FilterSecurityInterceptor;
import org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter;
import org.springframework.util.Assert;
import org.springframework.util.ReflectionUtils;
import org.springframework.web.accept.ContentNegotiationStrategy;
import org.springframework.web.accept.HeaderContentNegotiationStrategy;

/**
 * Provides a convenient base class for creating a {@link WebSecurityConfigurer}
 * instance. The implementation allows customization by overriding methods.
 *
 * <p>
 * Will automatically apply the result of looking up
 * {@link AbstractHttpConfigurer} from {@link SpringFactoriesLoader} to allow
 * developers to extend the defaults.
 * To do this, you must create a class that extends AbstractHttpConfigurer and then create a file in the classpath at "META-INF/spring.factories" that looks something like:
 * </p>
 * <pre>
 * org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer = sample.MyClassThatExtendsAbstractHttpConfigurer
 * </pre>
 * If you have multiple classes that should be added you can use "," to separate the values. For example:
 *
 * <pre>
 * org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer = sample.MyClassThatExtendsAbstractHttpConfigurer, sample.OtherThatExtendsAbstractHttpConfigurer
 * </pre>
 *
 * @see EnableWebSecurity
 *
 * @author Rob Winch
 */
@Order(100)
public abstract class WebSecurityConfigurerAdapter implements
		WebSecurityConfigurer<WebSecurity> {
	private final Log logger = LogFactory.getLog(WebSecurityConfigurerAdapter.class);

	private ApplicationContext context;

	private ContentNegotiationStrategy contentNegotiationStrategy = new HeaderContentNegotiationStrategy();

	private ObjectPostProcessor<Object> objectPostProcessor = new ObjectPostProcessor<Object>() {
		public <T> T postProcess(T object) {
			throw new IllegalStateException(
					ObjectPostProcessor.class.getName()
							+ " is a required bean. Ensure you have used @EnableWebSecurity and @Configuration");
		}
	};

	private AuthenticationConfiguration authenticationConfiguration;
	private AuthenticationManagerBuilder authenticationBuilder;
	private AuthenticationManagerBuilder localConfigureAuthenticationBldr;
	private boolean disableLocalConfigureAuthenticationBldr;
	private boolean authenticationManagerInitialized;
	private AuthenticationManager authenticationManager;
	private AuthenticationTrustResolver trustResolver = new AuthenticationTrustResolverImpl();
	private HttpSecurity http;
	private boolean disableDefaults;

	/**
	 * Creates an instance with the default configuration enabled.
	 */
	protected WebSecurityConfigurerAdapter() {
		this(false);
	}

	/**
	 * Creates an instance which allows specifying if the default configuration should be
	 * enabled. Disabling the default configuration should be considered more advanced
	 * usage as it requires more understanding of how the framework is implemented.
	 *
	 * @param disableDefaults true if the default configuration should be disabled, else
	 * false
	 */
	protected WebSecurityConfigurerAdapter(boolean disableDefaults) {
		this.disableDefaults = disableDefaults;
	}

	/**
	 * Used by the default implementation of {@link #authenticationManager()} to attempt
	 * to obtain an {@link AuthenticationManager}. If overridden, the
	 * {@link AuthenticationManagerBuilder} should be used to specify the
	 * {@link AuthenticationManager}.
	 *
	 * <p>
	 * The {@link #authenticationManagerBean()} method can be used to expose the resulting
	 * {@link AuthenticationManager} as a Bean. The {@link #userDetailsServiceBean()} can
	 * be used to expose the last populated {@link UserDetailsService} that is created
	 * with the {@link AuthenticationManagerBuilder} as a Bean. The
	 * {@link UserDetailsService} will also automatically be populated on
	 * {@link HttpSecurity#getSharedObject(Class)} for use with other
	 * {@link SecurityContextConfigurer} (i.e. RememberMeConfigurer )
	 * </p>
	 *
	 * <p>
	 * For example, the following configuration could be used to register in memory
	 * authentication that exposes an in memory {@link UserDetailsService}:
	 * </p>
	 *
	 * <pre>
	 * &#064;Override
	 * protected void configure(AuthenticationManagerBuilder auth) {
	 * 	auth
	 * 	// enable in memory based authentication with a user named
	 * 	// &quot;user&quot; and &quot;admin&quot;
	 * 	.inMemoryAuthentication().withUser(&quot;user&quot;).password(&quot;password&quot;).roles(&quot;USER&quot;).and()
	 * 			.withUser(&quot;admin&quot;).password(&quot;password&quot;).roles(&quot;USER&quot;, &quot;ADMIN&quot;);
	 * }
	 *
	 * // Expose the UserDetailsService as a Bean
	 * &#064;Bean
	 * &#064;Override
	 * public UserDetailsService userDetailsServiceBean() throws Exception {
	 * 	return super.userDetailsServiceBean();
	 * }
	 *
	 * </pre>
	 *
	 * @param auth the {@link AuthenticationManagerBuilder} to use
	 * @throws Exception
	 */
	protected void configure(AuthenticationManagerBuilder auth) throws Exception {
		this.disableLocalConfigureAuthenticationBldr = true;
	}

	/**
	 * Creates the {@link HttpSecurity} or returns the current instance
	 *
	 * ] * @return the {@link HttpSecurity}
	 * @throws Exception
	 */
	@SuppressWarnings({ "rawtypes", "unchecked" })
	protected final HttpSecurity getHttp() throws Exception {
		if (http != null) {
			return http;
		}

		DefaultAuthenticationEventPublisher eventPublisher = objectPostProcessor
				.postProcess(new DefaultAuthenticationEventPublisher());
		localConfigureAuthenticationBldr.authenticationEventPublisher(eventPublisher);

		AuthenticationManager authenticationManager = authenticationManager();
		authenticationBuilder.parentAuthenticationManager(authenticationManager);
		Map<Class<? extends Object>, Object> sharedObjects = createSharedObjects();

		http = new HttpSecurity(objectPostProcessor, authenticationBuilder,
				sharedObjects);
		if (!disableDefaults) {
			// @formatter:off
			http
				.csrf().and()
				.addFilter(new WebAsyncManagerIntegrationFilter())
				.exceptionHandling().and()
				.headers().and()
				.sessionManagement().and()
				.securityContext().and()
				.requestCache().and()
				.anonymous().and()
				.servletApi().and()
				.apply(new DefaultLoginPageConfigurer<HttpSecurity>()).and()
				.logout();
			// @formatter:on
			ClassLoader classLoader = this.context.getClassLoader();
			List<AbstractHttpConfigurer> defaultHttpConfigurers =
					SpringFactoriesLoader.loadFactories(AbstractHttpConfigurer.class, classLoader);

			for(AbstractHttpConfigurer configurer : defaultHttpConfigurers) {
				http.apply(configurer);
			}
		}
		configure(http);
		return http;
	}

	/**
	 * Override this method to expose the {@link AuthenticationManager} from
	 * {@link #configure(AuthenticationManagerBuilder)} to be exposed as a Bean. For
	 * example:
	 *
	 * <pre>
	 * &#064;Bean(name name="myAuthenticationManager")
	 * &#064;Override
	 * public AuthenticationManager authenticationManagerBean() throws Exception {
	 *     return super.authenticationManagerBean();
	 * }
	 * </pre>
	 *
	 * @return the {@link AuthenticationManager}
	 * @throws Exception
	 */
	public AuthenticationManager authenticationManagerBean() throws Exception {
		return new AuthenticationManagerDelegator(authenticationBuilder, context);
	}

	/**
	 * Gets the {@link AuthenticationManager} to use. The default strategy is if
	 * {@link #configure(AuthenticationManagerBuilder)} method is overridden to use the
	 * {@link AuthenticationManagerBuilder} that was passed in. Otherwise, autowire the
	 * {@link AuthenticationManager} by type.
	 *
	 * @return
	 * @throws Exception
	 */
	protected AuthenticationManager authenticationManager() throws Exception {
		if (!authenticationManagerInitialized) {
			configure(localConfigureAuthenticationBldr);
			if (disableLocalConfigureAuthenticationBldr) {
				authenticationManager = authenticationConfiguration
						.getAuthenticationManager();
			}
			else {
				authenticationManager = localConfigureAuthenticationBldr.build();
			}
			authenticationManagerInitialized = true;
		}
		return authenticationManager;
	}

	/**
	 * Override this method to expose a {@link UserDetailsService} created from
	 * {@link #configure(AuthenticationManagerBuilder)} as a bean. In general only the
	 * following override should be done of this method:
	 *
	 * <pre>
	 * &#064;Bean(name = &quot;myUserDetailsService&quot;)
	 * // any or no name specified is allowed
	 * &#064;Override
	 * public UserDetailsService userDetailsServiceBean() throws Exception {
	 * 	return super.userDetailsServiceBean();
	 * }
	 * </pre>
	 *
	 * To change the instance returned, developers should change
	 * {@link #userDetailsService()} instead
	 * @return
	 * @throws Exception
	 * @see #userDetailsService()
	 */
	public UserDetailsService userDetailsServiceBean() throws Exception {
		AuthenticationManagerBuilder globalAuthBuilder = context
				.getBean(AuthenticationManagerBuilder.class);
		return new UserDetailsServiceDelegator(Arrays.asList(
				localConfigureAuthenticationBldr, globalAuthBuilder));
	}

	/**
	 * Allows modifying and accessing the {@link UserDetailsService} from
	 * {@link #userDetailsServiceBean()} without interacting with the
	 * {@link ApplicationContext}. Developers should override this method when changing
	 * the instance of {@link #userDetailsServiceBean()}.
	 *
	 * @return
	 */
	protected UserDetailsService userDetailsService() {
		AuthenticationManagerBuilder globalAuthBuilder = context
				.getBean(AuthenticationManagerBuilder.class);
		return new UserDetailsServiceDelegator(Arrays.asList(
				localConfigureAuthenticationBldr, globalAuthBuilder));
	}

	public void init(final WebSecurity web) throws Exception {
		final HttpSecurity http = getHttp();
		web.addSecurityFilterChainBuilder(http).postBuildAction(new Runnable() {
			public void run() {
				FilterSecurityInterceptor securityInterceptor = http
						.getSharedObject(FilterSecurityInterceptor.class);
				web.securityInterceptor(securityInterceptor);
			}
		});
	}

	/**
	 * Override this method to configure {@link WebSecurity}. For example, if you wish to
	 * ignore certain requests.
	 */
	public void configure(WebSecurity web) throws Exception {
	}

	/**
	 * Override this method to configure the {@link HttpSecurity}. Typically subclasses
	 * should not invoke this method by calling super as it may override their
	 * configuration. The default configuration is:
	 *
	 * <pre>
	 * http.authorizeRequests().anyRequest().authenticated().and().formLogin().and().httpBasic();
	 * </pre>
	 *
	 * @param http the {@link HttpSecurity} to modify
	 * @throws Exception if an error occurs
	 */
	// @formatter:off
	protected void configure(HttpSecurity http) throws Exception {
		logger.debug("Using default configure(HttpSecurity). If subclassed this will potentially override subclass configure(HttpSecurity).");

		http
			.authorizeRequests()
				.anyRequest().authenticated()
				.and()
			.formLogin().and()
			.httpBasic();
	}
	// @formatter:on

	/**
	 * Gets the ApplicationContext
	 * @return the context
	 */
	protected final ApplicationContext getApplicationContext() {
		return this.context;
	}

	@Autowired
	public void setApplicationContext(ApplicationContext context) {
		this.context = context;
	}

	@Autowired(required = false)
	public void setTrustResolver(AuthenticationTrustResolver trustResolver) {
		this.trustResolver = trustResolver;
	}

	@Autowired(required = false)
	public void setContentNegotationStrategy(
			ContentNegotiationStrategy contentNegotiationStrategy) {
		this.contentNegotiationStrategy = contentNegotiationStrategy;
	}

	@Autowired
	public void setObjectPostProcessor(ObjectPostProcessor<Object> objectPostProcessor) {
		this.objectPostProcessor = objectPostProcessor;

		authenticationBuilder = new AuthenticationManagerBuilder(objectPostProcessor);
		localConfigureAuthenticationBldr = new AuthenticationManagerBuilder(
				objectPostProcessor) {
			@Override
			public AuthenticationManagerBuilder eraseCredentials(boolean eraseCredentials) {
				authenticationBuilder.eraseCredentials(eraseCredentials);
				return super.eraseCredentials(eraseCredentials);
			}

		};
	}

	@Autowired
	public void setAuthenticationConfiguration(
			AuthenticationConfiguration authenticationConfiguration) {
		this.authenticationConfiguration = authenticationConfiguration;
	}

	/**
	 * Creates the shared objects
	 *
	 * @return the shared Objects
	 */
	private Map<Class<? extends Object>, Object> createSharedObjects() {
		Map<Class<? extends Object>, Object> sharedObjects = new HashMap<Class<? extends Object>, Object>();
		sharedObjects.putAll(localConfigureAuthenticationBldr.getSharedObjects());
		sharedObjects.put(UserDetailsService.class, userDetailsService());
		sharedObjects.put(ApplicationContext.class, context);
		sharedObjects.put(ContentNegotiationStrategy.class, contentNegotiationStrategy);
		sharedObjects.put(AuthenticationTrustResolver.class, trustResolver);
		return sharedObjects;
	}

	/**
	 * Delays the use of the {@link UserDetailsService} from the
	 * {@link AuthenticationManagerBuilder} to ensure that it has been fully configured.
	 *
	 * @author Rob Winch
	 * @since 3.2
	 */
	static final class UserDetailsServiceDelegator implements UserDetailsService {
		private List<AuthenticationManagerBuilder> delegateBuilders;
		private UserDetailsService delegate;
		private final Object delegateMonitor = new Object();

		UserDetailsServiceDelegator(List<AuthenticationManagerBuilder> delegateBuilders) {
			if (delegateBuilders.contains(null)) {
				throw new IllegalArgumentException(
						"delegateBuilders cannot contain null values. Got "
								+ delegateBuilders);
			}
			this.delegateBuilders = delegateBuilders;
		}

		public UserDetails loadUserByUsername(String username)
				throws UsernameNotFoundException {
			if (delegate != null) {
				return delegate.loadUserByUsername(username);
			}

			synchronized (delegateMonitor) {
				if (delegate == null) {
					for (AuthenticationManagerBuilder delegateBuilder : delegateBuilders) {
						delegate = delegateBuilder.getDefaultUserDetailsService();
						if (delegate != null) {
							break;
						}
					}

					if (delegate == null) {
						throw new IllegalStateException("UserDetailsService is required.");
					}
					this.delegateBuilders = null;
				}
			}

			return delegate.loadUserByUsername(username);
		}
	}

	/**
	 * Delays the use of the {@link AuthenticationManager} build from the
	 * {@link AuthenticationManagerBuilder} to ensure that it has been fully configured.
	 *
	 * @author Rob Winch
	 * @since 3.2
	 */
	static final class AuthenticationManagerDelegator implements AuthenticationManager {
		private AuthenticationManagerBuilder delegateBuilder;
		private AuthenticationManager delegate;
		private final Object delegateMonitor = new Object();
		private Set<String> beanNames;

		AuthenticationManagerDelegator(AuthenticationManagerBuilder delegateBuilder,
				ApplicationContext context) {
			Assert.notNull(delegateBuilder, "delegateBuilder cannot be null");
			Field parentAuthMgrField = ReflectionUtils.findField(
					AuthenticationManagerBuilder.class, "parentAuthenticationManager");
			ReflectionUtils.makeAccessible(parentAuthMgrField);
			beanNames = getAuthenticationManagerBeanNames(context);
			validateBeanCycle(
					ReflectionUtils.getField(parentAuthMgrField, delegateBuilder),
					beanNames);
			this.delegateBuilder = delegateBuilder;
		}

		public Authentication authenticate(Authentication authentication)
				throws AuthenticationException {
			if (delegate != null) {
				return delegate.authenticate(authentication);
			}

			synchronized (delegateMonitor) {
				if (delegate == null) {
					delegate = this.delegateBuilder.getObject();
					this.delegateBuilder = null;
				}
			}

			return delegate.authenticate(authentication);
		}

		private static Set<String> getAuthenticationManagerBeanNames(
				ApplicationContext applicationContext) {
			String[] beanNamesForType = BeanFactoryUtils
					.beanNamesForTypeIncludingAncestors(applicationContext,
							AuthenticationManager.class);
			return new HashSet<String>(Arrays.asList(beanNamesForType));
		}

		private static void validateBeanCycle(Object auth, Set<String> beanNames) {
			if (auth != null && !beanNames.isEmpty()) {
				if (auth instanceof Advised) {
					Advised advised = (Advised) auth;
					TargetSource targetSource = advised.getTargetSource();
					if (targetSource instanceof LazyInitTargetSource) {
						LazyInitTargetSource lits = (LazyInitTargetSource) targetSource;
						if (beanNames.contains(lits.getTargetBeanName())) {
							throw new FatalBeanException(
									"A dependency cycle was detected when trying to resolve the AuthenticationManager. Please ensure you have configured authentication.");
						}
					}
				}
				beanNames = Collections.emptySet();
			}
		}
	}

}
