/**
    * This file Copyright (c) 2012-2018 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.rest;
  
  import info.magnolia.cms.beans.config.ServerConfiguration;
  import info.magnolia.config.registry.DefinitionMetadata;
  import info.magnolia.config.registry.DefinitionMetadataBuilder;
  import info.magnolia.config.registry.DefinitionProvider;
  import info.magnolia.config.registry.DefinitionProviderBuilder;
  import info.magnolia.event.EventBus;
  import info.magnolia.event.HandlerRegistration;
  import info.magnolia.event.SystemEventBus;
  import info.magnolia.objectfactory.ComponentProvider;
  import info.magnolia.objectfactory.Components;
  import info.magnolia.rest.provider.AdditionalProviderDefinition;
  import info.magnolia.rest.registry.EndpointDefinitionRegistry;
  import info.magnolia.rest.registry.EndpointDefinitionRegistryEvent;
  import info.magnolia.rest.registry.EndpointDefinitionRegistryEventHandler;
  
  import java.io.File;
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.stream.Collectors;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.servlet.ServletConfig;
  import javax.servlet.ServletException;
  import javax.ws.rs.core.Application;
  
  import org.apache.commons.beanutils.BeanUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.jboss.resteasy.plugins.server.servlet.ConfigurationBootstrap;
  import org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher;
  import org.jboss.resteasy.plugins.server.servlet.ServletBootstrap;
  import org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher;
  import org.jboss.resteasy.spi.ResteasyDeployment;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Dispatcher of the rest requests to the dynamically registered endpoints.
   */
  public class RestDispatcherServlet extends HttpServletDispatcher implements EndpointDefinitionRegistryEventHandler {
  
      private static final Logger log = LoggerFactory.getLogger(RestDispatcherServlet.class);
  
      private final RestIntegrationModule restIntegrationModule;
      private final EndpointDefinitionRegistry endpointRegistry;
      private final EventBus systemEventBus;
      private final Map<String, Object> endpoints = new ConcurrentHashMap<>();
      private final ComponentProvider componentProvider;
      private final ServerConfiguration serverConfiguration;
  
      private Application application = new Application() {
          @Override
          public Set<Object> getSingletons() {
              HashSet<Object> singletons = new HashSet<>();
              singletons.addAll(endpoints.values());
              return singletons;
          }
      };
      private ServletConfig servletConfig;
      private HandlerRegistration registerHandler;
 
     @Inject
     public RestDispatcherServlet(final RestIntegrationModule restIntegrationModule, EndpointDefinitionRegistry endpointRegistry, @Named(SystemEventBus.NAME) EventBus systemEventBus, ComponentProvider componentProvider, ServerConfiguration serverConfiguration) {
         this.restIntegrationModule = restIntegrationModule;
         this.endpointRegistry = endpointRegistry;
         this.systemEventBus = systemEventBus;
         this.componentProvider = componentProvider;
         this.serverConfiguration = serverConfiguration;
     }
 
     @Deprecated
     public RestDispatcherServlet(final RestIntegrationModule restIntegrationModule, EndpointDefinitionRegistry endpointRegistry, @Named(SystemEventBus.NAME) EventBus systemEventBus) {
         this(restIntegrationModule, endpointRegistry, systemEventBus, Components.getComponentProvider(), Components.getComponent(ServerConfiguration.class));
     }
 
     @Override
     public void init(ServletConfig servletConfig) throws ServletException {
         this.servletConfig = servletConfig;
 
         // Initialise the ServletContainerDispatcher
         servletContainerDispatcher = new ServletContainerDispatcher(servletConfig);
         ConfigurationBootstrap bootstrap = createBootstrap(servletConfig);
         servletContainerDispatcher.init(servletConfig.getServletContext(), bootstrap, this, this);
 
         // Register configured additional providers
         restIntegrationModule.getAdditionalProviders().stream()
                 .map(AdditionalProviderDefinition::getProviderClass)
                 .filter(Objects::nonNull)
                 .peek(providerClass -> log.debug("Registering additional provider [{}]", providerClass))
                 .forEach(providerClass -> super.getDispatcher().getProviderFactory().registerProvider(providerClass));
 
         // Register all currently registered endpoints
         for (DefinitionProvider<EndpointDefinition> provider : endpointRegistry.getAllProviders()) {
             try {
                 registerEndpoint(provider);
             } catch (Exception e) {
                 log.error("Failed to register endpoint [{}]", provider.getMetadata().getReferenceId(), e);
                 // Others should continue to be registered.
             }
         }
 
         // Listen for changes to the registry to observe endpoints being added or removed
         registerHandler = systemEventBus.addHandler(EndpointDefinitionRegistryEvent.class, this);
     }
 
     private void registerPreviewEndpoint(final DefinitionProvider<EndpointDefinition> provider) {
         final EndpointDefinition deliveryEndpointDefinition = provider.get();
         final DefinitionMetadata deliveryMetadata = provider.getMetadata();
         final String endpointReferenceId = deliveryMetadata.getReferenceId().replace("delivery", "preview");
         final String path = deliveryEndpointDefinition.getEndpointPath();
         try {
             final DefinitionMetadata previewEndpointMetadata = DefinitionMetadataBuilder.usingNameAsId()
                     .name(endpointReferenceId)
                     .configurationSourceType(deliveryMetadata.getConfigurationSourceType())
                     .deprecation(deliveryMetadata.getDeprecation().isPresent() ? deliveryMetadata.getDeprecation().get() : null)
                     .location(deliveryMetadata.getLocation())
                     .module(deliveryMetadata.getModule())
                     .relativeLocation(deliveryMetadata.getRelativeLocation())
                     .type(deliveryMetadata.getType())
                     .build();
             final EndpointDefinitionpointDefinition.html#EndpointDefinition">EndpointDefinition previewEndpointDefinition = (EndpointDefinition) BeanUtils.cloneBean(deliveryEndpointDefinition);
             if (path != null) {
                 BeanUtils.setProperty(previewEndpointDefinition, "endpointPath", path.replace("delivery", "preview"));
             }
             final DefinitionProvider<EndpointDefinition> previewProvider = DefinitionProviderBuilder.<EndpointDefinition>newBuilder()
                     .metadata(previewEndpointMetadata)
                     .rawView(provider.getRaw())
                     .definition(previewEndpointDefinition)
                     .build();
             registerEndpoint(previewProvider);
 
         } catch (Exception e) {
             log.warn("Unable register preview endpoint for {}", deliveryMetadata.getReferenceId(), e);
         }
     }
 
     private boolean isDeliveryEndpoint(final DefinitionProvider<EndpointDefinition> provider) {
         return getPath(provider).startsWith("delivery");
     }
 
     private String getPath(final DefinitionProvider<EndpointDefinition> provider) {
         final EndpointDefinition endpointDefinition = provider.get();
         String endpointReferenceId = provider.getMetadata().getReferenceId();
         if (StringUtils.isNotEmpty(endpointDefinition.getEndpointPath())) {
             return truncatePath(endpointDefinition.getEndpointPath());
         } else {
             return getBasePath(endpointReferenceId);
         }
     }
 
     // need to override this because we're not calling init(ServletConfig) on the super class
     @Override
     public ServletConfig getServletConfig() {
         return servletConfig;
     }
 
     @Override
     public void destroy() {
         registerHandler.removeHandler();
         super.destroy();
         endpoints.clear();
     }
 
     // EVENT HANDLING
 
     @Override
     public void onEndpointRegistered(EndpointDefinitionRegistryEvent event) {
         DefinitionProvider<EndpointDefinition> provider = event.getEndpointDefinitionProvider();
         final String referenceId = provider.getMetadata().getReferenceId();
         if (endpoints.containsKey(referenceId)) {
             unregisterEndpoint(referenceId);
         }
         registerEndpoint(provider);
     }
 
     @Override
     public void onEndpointReregistered(EndpointDefinitionRegistryEvent event) {
         DefinitionProvider<EndpointDefinition> provider = event.getEndpointDefinitionProvider();
         unregisterEndpoint(provider.getMetadata().getReferenceId());
         registerEndpoint(provider);
     }
 
     @Override
     public void onEndpointUnregistered(EndpointDefinitionRegistryEvent event) {
         unregisterEndpoint(event.getEndpointName());
     }
 
     protected Object registerEndpoint(DefinitionProvider<EndpointDefinition> provider) {
         if (!provider.isValid()) {
             return null;
         }
 
         EndpointDefinition endpointDefinition = provider.get();
         String endpointReferenceId = provider.getMetadata().getReferenceId();
 
         if (!endpointDefinition.isEnabled()) {
             log.info("Endpoint {} is disabled, skipping registration", endpointReferenceId);
             return null;
         } else if (endpointDefinition.getImplementationClass() == null) {
             log.warn("Endpoint {} is missing implementationClass, skipping registration", endpointReferenceId);
             return null;
         }
 
         Object endpoint = instantiateEndpoint(endpointDefinition);
 
         if (supportDynamicPath(endpointDefinition.getImplementationClass())) {
             String path = getPath(provider);
             super.getDispatcher().getRegistry().addSingletonResource(endpoint, path);
             log.info("Endpoint {} is registered with base path: [context]/{}", endpointReferenceId, path);
         } else {
             super.getDispatcher().getRegistry().addSingletonResource(endpoint);
         }
         endpoints.put(endpointReferenceId, endpoint);
         // Register preview endpoint
         if (isDeliveryEndpoint(provider) && serverConfiguration.isAdmin()) {
             registerPreviewEndpoint(provider);
         }
 
         return endpoint;
     }
 
     /**
      * Allows an endpoint to be registered for the servlet without actually being in the registry.
      * This is used for REST Tools in particular; otherwise {@link #registerEndpoint(DefinitionProvider)} should be preferred.
      */
     protected Object registerEndpoint(EndpointDefinition endpointDefinition) {
         if (!endpointDefinition.isEnabled()) {
             return null;
         }
         Object endpoint = instantiateEndpoint(endpointDefinition);
         endpoints.put(endpointDefinition.getName(), endpoint);
         super.getDispatcher().getRegistry().addSingletonResource(endpoint);
         return endpoint;
     }
 
     protected void unregisterEndpoint(String endpointReferenceId) {
         Object endpoint = endpoints.remove(endpointReferenceId);
         if (endpoint != null) {
             Class<?> endpointClass = endpoint.getClass();
             if (supportDynamicPath(endpointClass) && endpoint instanceof AbstractEndpoint) {
                 String configuredPath = ((AbstractEndpoint) endpoint).getEndpointDefinition().getEndpointPath();
                 String path = StringUtils.isEmpty(configuredPath) ? getBasePath(endpointReferenceId) : truncatePath(configuredPath);
                 super.getDispatcher().getRegistry().removeRegistrations(endpointClass, path);
                 log.debug("Unregister endpoint {} with base path {} from registry.", endpointReferenceId, path);
             } else {
                 super.getDispatcher().getRegistry().removeRegistrations(endpointClass);
                 log.debug("Unregister endpoint which has reference id: {} from registry.", endpointReferenceId);
             }
 
         }
         // Unregister preview endpoint
         if (endpointReferenceId.startsWith("delivery")) {
             unregisterEndpoint(endpointReferenceId.replace("delivery", "preview"));
         }
     }
 
     protected Object instantiateEndpoint(EndpointDefinition endpointDefinition) {
         return componentProvider.newInstance(endpointDefinition.getImplementationClass(), endpointDefinition);
     }
 
     // DEPLOYMENT
 
     protected Application getApplication() {
         return application;
     }
 
     protected ConfigurationBootstrap createBootstrap(ServletConfig servletConfig) {
         return new ServletBootstrap(servletConfig) {
             @Override
             public ResteasyDeployment createDeployment() {
                 return configureDeployment(super.createDeployment());
             }
         };
     }
 
     protected ResteasyDeployment configureDeployment(ResteasyDeployment deployment) {
         deployment.setApplicationClass(null);
         deployment.setApplication(getApplication());
         return deployment;
     }
 
     /**
      * Extract base path from preference id and definition path.
      * Only applicable for {@linkplain DynamicPath} annotated endpoint class.
      * Convention:
      * /module_name/restEndpoints/p1/p2/p3/def_v1.yaml -> {context}/p1/p2/p3/def/v1
      * /module_name/restEndpoints/p1/p2/p3/defv1.yaml -> {context}/p1/p2/p3/defv1
      * /module_name/restEndpoints/def_v1.yaml -> {context}/def/v1
      * /module_name/restEndpoints/defv1.yaml -> {context}/defv1
      *
      * @return base path
      */
     protected String getBasePath(String endpointReferenceId) {
         final String[] endpointPaths = StringUtils.split(endpointReferenceId, File.separator);
         endpointPaths[endpointPaths.length - 1] = endpointPaths[endpointPaths.length - 1].replace('_', '/');
         return Arrays.stream(endpointPaths).collect(Collectors.joining("/"));
     }
 
     private boolean supportDynamicPath(final Class<?> implementationClass) {
         return implementationClass != null && implementationClass.getAnnotation(DynamicPath.class) != null;
     }
 
     private String truncatePath(String configuredPath) {
         String path = StringUtils.removeEnd(configuredPath, "/");
         path = StringUtils.removeStart(path, "/");
         return path;
     }
 }