/**
    * Copyright 2005-2015 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.rice.krad.uif.freemarker;
  
  import java.io.IOException;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.HashSet;
  
  import javax.servlet.GenericServlet;
  import javax.servlet.ServletConfig;
  import javax.servlet.ServletContext;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  
  import org.apache.log4j.Logger;
  import org.springframework.beans.BeansException;
  import org.springframework.beans.factory.BeanInitializationException;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextAware;
  import org.springframework.web.context.ServletContextAware;
  import org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer;
  
  import freemarker.core.InlineTemplateElement;
  import freemarker.ext.jsp.TaglibFactory;
  import freemarker.ext.servlet.ServletContextHashModel;
  import freemarker.template.Configuration;
  import freemarker.template.ObjectWrapper;
  import freemarker.template.TemplateException;
  
  /**
   * Register inline template processing adaptors for high-traffic KRAD templates.
   * 
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class FreeMarkerInlineRenderBootstrap implements InitializingBean, ApplicationContextAware, ServletContextAware {
  
      private static final Logger LOG = Logger.getLogger(FreeMarkerInlineRenderBootstrap.class);
      
      /**
       * The freemarker configuration.
       */
      private static Configuration freeMarkerConfig;
  
      /**
       * The application context.
       */
      private static ApplicationContext applicationContext;
      
      /**
       * The servlet context.
       */
      private static ServletContext servletContext;
  
      /**
       * The tablib factory for use in the component rendering phase.
       */
      private static TaglibFactory taglibFactory;
  
      /**
       * The object wrapper for use in the component rendering phase.
       */
      private static ObjectWrapper objectWrapper;
  
      /**
       * Servlet context hash model for use in the component rendering phase.
       */
      private static ServletContextHashModel servletContextHashModel;
      
      /**
       * Get the FreeMarker configuration initialized for the current KRAD application. 
       * 
       * @return The FreeMarker configuration initialized for the current KRAD application.
       */
      public static Configuration getFreeMarkerConfig() {
          if (freeMarkerConfig == null) {
              throw new IllegalStateException("FreeMarker configuruation is not available, "
                      + "use krad-base-servlet.xml or define FreeMarkerInlineRenderBootstrap in servlet.xml");
          }
          
          return freeMarkerConfig;
      }
  
      /**
      * Get the servlet context initialized for the current KRAD application. 
      * 
      * @return The servlet context initialized for the current KRAD application.
      */
     public static ServletContext getServletContext() {
         if (servletContext == null) {
             throw new IllegalStateException("Servlet context is not available, "
                     + "use krad-base-servlet.xml or define FreeMarkerInlineRenderBootstrap in servlet.xml");
         }
         
         return servletContext;
     }
 
     /**
      * Get the tablib factory for use in the component rendering phase.
      * 
      * @return The tablib factory for use in the component rendering phase.
      */
     public static TaglibFactory getTaglibFactory() {
         return taglibFactory;
     }
 
     /**
      * Get the object wrapper for use in the component rendering phase.
      * 
      * @return The object wrapper for use in the component rendering phase.
      */
     public static ObjectWrapper getObjectWrapper() {
         return objectWrapper;
     }
 
     /**
      * Get the servlet context hash model for use in the component rendering phase.
      * 
      * @return The servlet context hash model for use in the component rendering phase.
      */
     public static ServletContextHashModel getServletContextHashModel() {
         return servletContextHashModel;
     }
 
     /**
      * Needed for JSP access in FreeMarker.
      * 
      * <p>Derived from Spring FreeMarkerView.</p>
      */
     private static class ServletAdapter extends GenericServlet {
 
         private static final long serialVersionUID = 8509364718276109450L;
 
         @Override
         public void service(ServletRequest servletRequest, ServletResponse servletResponse) {}
         
     }
 
     /**
      * Internal implementation of the {@link ServletConfig} interface,
      * to be passed to the servlet adapter.
      * 
      * <p>Derived from Spring FreeMarkerView.</p>
      */
     private static class DelegatingServletConfig implements ServletConfig {
 
         public String getServletName() {
             return applicationContext.getDisplayName();
         }
 
         public ServletContext getServletContext() {
             return servletContext;
         }
 
         public String getInitParameter(String paramName) {
             return null;
         }
 
         public Enumeration<String> getInitParameterNames() {
             return Collections.enumeration(new HashSet<String>());
         }
     }
 
     /**
      * Initialize FreeMarker elements after servlet context and FreeMarker configuration have both
      * been populated.
      */
     private static void finishConfig() {
         if (freeMarkerConfig != null && servletContext != null) {
             taglibFactory = new TaglibFactory(servletContext);
             
             objectWrapper = freeMarkerConfig.getObjectWrapper();
             if (objectWrapper == null) {
                 objectWrapper = ObjectWrapper.DEFAULT_WRAPPER;
             }
 
             GenericServlet servlet = new ServletAdapter();
             try {
                 servlet.init(new DelegatingServletConfig());
             } catch (ServletException ex) {
                 throw new BeanInitializationException("Initialization of GenericServlet adapter failed", ex);
             }
             
             servletContextHashModel = new ServletContextHashModel(servlet, ObjectWrapper.DEFAULT_WRAPPER);
             
             LOG.info("Freemarker configuration complete");
         }
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
         try {
             freeMarkerConfig = ((FreeMarkerConfigurer) applicationContext.getBean("freemarkerConfig"))
                     .createConfiguration();
             LOG.info("Set freemarker bootstrap " + freeMarkerConfig);
         } catch (IOException e) {
             throw new IllegalStateException("Error loading freemarker configuration", e);
         } catch (TemplateException e) {
             throw new IllegalStateException("Error loading freemarker configuration", e);
         }
         finishConfig();
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void setServletContext(ServletContext servletContext) {
         FreeMarkerInlineRenderBootstrap.servletContext = servletContext;
         finishConfig();
     }
 
     /**
      * Register high-traffic KRAD template adaptors.  
      * 
      * {@inheritDoc}
      */
     @Override
     public void afterPropertiesSet() throws Exception {
         InlineTemplateElement.registerAdaptor("script", new FreeMarkerScriptAdaptor());
         InlineTemplateElement.registerAdaptor("template", new FreeMarkerTemplateAdaptor());
         InlineTemplateElement.registerAdaptor("collectionGroup", new FreeMarkerCollectionGroupAdaptor());
         InlineTemplateElement.registerAdaptor("stacked", new FreeMarkerStackedAdaptor());
         InlineTemplateElement.registerAdaptor("groupWrap-open", new FreeMarkerOpenGroupWrapAdaptor());
         InlineTemplateElement.registerAdaptor("groupWrap-close", new FreeMarkerCloseGroupWrapAdaptor());
     }
 
 }