/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.myfaces.shared.application;
  
  import java.net.MalformedURLException;
  import java.util.Map;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import javax.faces.application.ViewHandler;
  import javax.faces.context.ExternalContext;
  import javax.faces.context.FacesContext;
  import javax.faces.render.ResponseStateManager;
  import javax.faces.view.ViewDeclarationLanguage;
  
  import org.apache.myfaces.shared.renderkit.html.util.SharedStringBuilder;
  import org.apache.myfaces.shared.util.ExternalContextUtils;
  import org.apache.myfaces.shared.util.StringUtils;
  import org.apache.myfaces.shared.util.ViewProtectionUtils;
  
  /**
   * A ViewHandlerSupport implementation for use with standard Java Servlet engines,
   * ie an engine that supports javax.servlet, and uses a standard web.xml file.
   */
  public class DefaultViewHandlerSupport implements ViewHandlerSupport
  {
      /**
       * Identifies the FacesServlet mapping in the current request map.
       */
      private static final String CACHED_SERVLET_MAPPING =
          DefaultViewHandlerSupport.class.getName() + ".CACHED_SERVLET_MAPPING";
  
      //private static final Log log = LogFactory.getLog(DefaultViewHandlerSupport.class);
      private static final Logger log = Logger.getLogger(DefaultViewHandlerSupport.class.getName());
      
      private static final String VIEW_HANDLER_SUPPORT_SB = "oam.viewhandler.SUPPORT_SB";
      
      private final String[] _faceletsViewMappings;
      private final String[] _contextSuffixes;
      private final String _faceletsContextSufix;
      private final boolean _initialized;
      private CheckedViewIdsCache checkedViewIdsCache = null;
      
      public DefaultViewHandlerSupport()
      {
          _faceletsViewMappings = null;
          _contextSuffixes = null;
          _faceletsContextSufix = null;
          _initialized = false;
      }
      
      public DefaultViewHandlerSupport(FacesContext facesContext)
      {
          _faceletsViewMappings = getFaceletsViewMappings(facesContext);
          _contextSuffixes = getContextSuffix(facesContext);
          _faceletsContextSufix = getFaceletsContextSuffix(facesContext);
          _initialized = true;
      }
  
      public String calculateViewId(FacesContext context, String viewId)
      {
          //If no viewId found, don't try to derive it, just continue.
          if (viewId == null)
          {
              return null;
          }
          FacesServletMapping mapping = getFacesServletMapping(context);
          if (mapping == null || mapping.isExtensionMapping())
          {
              viewId = handleSuffixMapping(context, viewId);
          }
          else if (mapping.isExactMapping())
          {
              // if the current request is a exact mapping and the viewId equals the exact viewId
              if (viewId.equals(mapping.getExact()))
              {
                  viewId = handleSuffixMapping(context, viewId + ".jsf");
              }
          }
          else if(mapping.isPrefixMapping())
          {
              viewId = handlePrefixMapping(viewId,mapping.getPrefix());
              
             // A viewId that is equals to the prefix mapping on servlet mode is
             // considered invalid, because jsp vdl will use RequestDispatcher and cause
             // a loop that ends in a exception. Note in portlet mode the view
             // could be encoded as a query param, so the viewId could be valid.
             if (viewId != null && viewId.equals(mapping.getPrefix()) &&
                 !ExternalContextUtils.isPortlet(context.getExternalContext()))
             {
                 throw new InvalidViewIdException();
             }
             
             // In JSF 2.3 some changes were done in the VDL to avoid the jsp vdl
             // RequestDispatcher redirection (only accept viewIds with jsp extension).
             // If we have this case
             if (viewId != null && viewId.equals(mapping.getPrefix()))
             {
                 viewId = handleSuffixMapping(context, viewId+".jsf");
             }
         }
         else if (mapping.getUrlPattern().startsWith(viewId))
         {
             throw new InvalidViewIdException(viewId);
         }
 
         //if(viewId != null)
         //{
         //    return (checkResourceExists(context,viewId) ? viewId : null);
         //}
 
         return viewId;    // return null if no physical resource exists
     }
     
     public String calculateAndCheckViewId(FacesContext context, String viewId)
     {
         //If no viewId found, don't try to derive it, just continue.
         if (viewId == null)
         {
             return null;
         }
         FacesServletMapping mapping = getFacesServletMapping(context);
         if (mapping == null || mapping.isExtensionMapping())
         {
             viewId = handleSuffixMapping(context, viewId);
         }
         else if (mapping.isExactMapping())
         {
             // if the current request is a exact mapping and the viewId equals the exact viewId
             if (viewId.equals(mapping.getExact()))
             {
                 viewId = handleSuffixMapping(context, viewId + ".jsf");
             }
         }
         else if(mapping.isPrefixMapping())
         {
             viewId = handlePrefixMapping(viewId,mapping.getPrefix());
 
             if(viewId != null)
             {
                 // A viewId that is equals to the prefix mapping on servlet mode is
                 // considered invalid, because jsp vdl will use RequestDispatcher and cause
                 // a loop that ends in a exception. Note in portlet mode the view
                 // could be encoded as a query param, so the viewId could be valid.
                 //if (viewId.equals(mapping.getPrefix()) &&
                 //    !ExternalContextUtils.isPortlet(context.getExternalContext()))
                 //{
                 //    throw new InvalidViewIdException();
                 //}
             
                 // In JSF 2.3 some changes were done in the VDL to avoid the jsp vdl
                 // RequestDispatcher redirection (only accept viewIds with jsp extension).
                 // If we have this case
                 if (viewId != null && viewId.equals(mapping.getPrefix()))
                 {
                     viewId = handleSuffixMapping(context, viewId+".jsf");
                 }
 
                 return (checkResourceExists(context,viewId) ? viewId : null);
             }
         }
         else if (mapping.getUrlPattern().startsWith(viewId))
         {
             throw new InvalidViewIdException(viewId);
         }
         else
         {
             if(viewId != null)
             {
                 return (checkResourceExists(context,viewId) ? viewId : null);
             }
         }
 
         return viewId;    // return null if no physical resource exists
     }
 
     public String calculateActionURL(FacesContext context, String viewId)
     {
         if (viewId == null || !viewId.startsWith("/"))
         {
             throw new IllegalArgumentException("ViewId must start with a '/': " + viewId);
         }
 
         FacesServletMapping mapping = getFacesServletMapping(context);
         ExternalContext externalContext = context.getExternalContext();
         String contextPath = externalContext.getRequestContextPath();
         //StringBuilder builder = new StringBuilder(contextPath);
         StringBuilder builder = SharedStringBuilder.get(context, VIEW_HANDLER_SUPPORT_SB);
         // If the context path is root, it is not necessary to append it, otherwise
         // and extra '/' will be set.
         if (contextPath != null && !(contextPath.length() == 1 && contextPath.charAt(0) == '/') )
         {
             builder.append(contextPath);
         }
         
         // In JSF 2.3 we could have cases where the viewId can be bound to an url-pattern that is not
         // prefix or suffix, but exact mapping. In this part we need to take the viewId and check if
         // the viewId is bound or not with a mapping.
         if (mapping != null && mapping.isExactMapping())
         {
             String exactMappingViewId = calculatePrefixedExactMapping(context, viewId);
             if (exactMappingViewId != null && !exactMappingViewId.isEmpty())
             {
                 // if the current exactMapping already matches the requested viewId -> same view, skip....
                 if (!mapping.getExact().equals(exactMappingViewId))
                 {
                     // different viewId -> lets try to lookup a exact mapping
                     mapping = FacesServletMappingUtils.getExactMapping(context, exactMappingViewId);
 
                     // no exactMapping for the requested viewId available BUT the current view is a exactMapping
                     // we need a to search for a prefix or extension mapping
                     if (mapping == null)
                     {
                         mapping = FacesServletMappingUtils.getGenericPrefixOrSuffixMapping(context);
                         if (mapping == null)
                         {
                             throw new IllegalStateException(
                                     "No generic (either prefix or suffix) servlet-mapping found for FacesServlet."
                                     + "This is required serve views, that are not exact mapped.");
                         }
                     }
                 }
             }
         }
         
         if (mapping != null)
         {
             if (mapping.isExactMapping())
             {
                 builder.append(mapping.getExact());
             }
             else if (mapping.isExtensionMapping())
             {
                 //See JSF 2.0 section 7.5.2 
                 String[] contextSuffixes = _initialized ? _contextSuffixes : getContextSuffix(context); 
                 boolean founded = false;
                 for (String contextSuffix : contextSuffixes)
                 {
                     if (viewId.endsWith(contextSuffix))
                     {
                         builder.append(viewId.substring(0, viewId.indexOf(contextSuffix)));
                         builder.append(mapping.getExtension());
                         founded = true;
                         break;
                     }
                 }
                 if (!founded)
                 {   
                     //See JSF 2.0 section 7.5.2
                     // - If the argument viewId has an extension, and this extension is mapping, 
                     // the result is contextPath + viewId
                     //
                     // -= Leonardo Uribe =- It is evident that when the page is generated, the derived 
                     // viewId will end with the 
                     // right contextSuffix, and a navigation entry on faces-config.xml should use such id,
                     // this is just a workaroud
                     // for usability. There is a potential risk that change the mapping in a webapp make 
                     // the same application fail,
                     // so use viewIds ending with mapping extensions is not a good practice.
                     if (viewId.endsWith(mapping.getExtension()))
                     {
                         builder.append(viewId);
                     }
                     else if(viewId.lastIndexOf('.') != -1 )
                     {
                         builder.append(viewId.substring(0, viewId.lastIndexOf('.')));
                         builder.append(contextSuffixes[0]);
                     }
                     else
                     {
                         builder.append(viewId);
                         builder.append(contextSuffixes[0]);
                     }
                 }
             }
             else if (mapping.isPrefixMapping())
             {
                 builder.append(mapping.getPrefix());
                 builder.append(viewId);
             }
         }
         else
         {
             builder.append(viewId);
         }
         
         //JSF 2.2 check view protection.
         if (ViewProtectionUtils.isViewProtected(context, viewId))
         {
             int index = builder.indexOf("?");
             if (index >= 0)
             {
                 builder.append("&");
             }
             else
             {
                 builder.append("?");
             }
             builder.append(ResponseStateManager.NON_POSTBACK_VIEW_TOKEN_PARAM);
             builder.append("=");
             ResponseStateManager rsm = context.getRenderKit().getResponseStateManager();
             builder.append(rsm.getCryptographicallyStrongTokenFromSession(context));
         }
         
         String calculatedActionURL = builder.toString();
         if (log.isLoggable(Level.FINEST))
         {
             log.finest("Calculated actionURL: '" + calculatedActionURL + "' for viewId: '" + viewId + "'");
         }
         return calculatedActionURL;
     }
     
     private String calculatePrefixedExactMapping(FacesContext context, String viewId)
     {
         String[] contextSuffixes = _initialized ? _contextSuffixes : getContextSuffix(context); 
         String prefixedExactMapping = null;
         for (String contextSuffix : contextSuffixes)
         {
             if (viewId.endsWith(contextSuffix))
             {
                 prefixedExactMapping = viewId.substring(0, viewId.length() - contextSuffix.length());
                 break;
             }
         }
         return prefixedExactMapping == null ? viewId : prefixedExactMapping;
     }
             
 
     /**
      * Read the web.xml file that is in the classpath and parse its internals to
      * figure out how the FacesServlet is mapped for the current webapp.
      */
     protected FacesServletMapping getFacesServletMapping(FacesContext context)
     {
         Map<Object, Object> attributes = context.getAttributes();
 
         // Has the mapping already been determined during this request?
         FacesServletMapping mapping = (FacesServletMapping) attributes.get(CACHED_SERVLET_MAPPING);
         if (mapping == null)
         {
             ExternalContext externalContext = context.getExternalContext();
             mapping = FacesServletMappingUtils.calculateFacesServletMapping(
                     context, externalContext.getRequestServletPath(),
                     externalContext.getRequestPathInfo(),
                     true);
 
             attributes.put(CACHED_SERVLET_MAPPING, mapping);
         }
         return mapping;
     }
 
     protected String[] getContextSuffix(FacesContext context)
     {
         String defaultSuffix = context.getExternalContext().getInitParameter(ViewHandler.DEFAULT_SUFFIX_PARAM_NAME);
         if (defaultSuffix == null)
         {
             defaultSuffix = ViewHandler.DEFAULT_SUFFIX;
         }
         return StringUtils.splitShortString(defaultSuffix, ' ');
     }
     
     protected String getFaceletsContextSuffix(FacesContext context)
     {
         String defaultSuffix = context.getExternalContext().getInitParameter(ViewHandler.FACELETS_SUFFIX_PARAM_NAME);
         if (defaultSuffix == null)
         {
             defaultSuffix = ViewHandler.DEFAULT_FACELETS_SUFFIX;
         }
         return defaultSuffix;
     }
     
     
     
     protected String[] getFaceletsViewMappings(FacesContext context)
     {
         String faceletsViewMappings= context.getExternalContext().getInitParameter(
                 ViewHandler.FACELETS_VIEW_MAPPINGS_PARAM_NAME);
         if(faceletsViewMappings == null)    //consider alias facelets.VIEW_MAPPINGS
         {
             faceletsViewMappings= context.getExternalContext().getInitParameter("facelets.VIEW_MAPPINGS");
         }
         
         return faceletsViewMappings == null ? null : StringUtils.splitShortString(faceletsViewMappings, ';');
     }
 
     /**
      * Return the normalized viewId according to the algorithm specified in 7.5.2 
      * by stripping off any number of occurrences of the prefix mapping from the viewId.
      * <p>
      * For example, both /faces/view.xhtml and /faces/faces/faces/view.xhtml would both return view.xhtml
      * </p>
      */
     protected String handlePrefixMapping(String viewId, String prefix)
     {
         // If prefix mapping (such as "/faces/*") is used for FacesServlet, 
         // normalize the viewId according to the following
         // algorithm, or its semantic equivalent, and return it.
                
         // Remove any number of occurrences of the prefix mapping from the viewId. 
         // For example, if the incoming value was /faces/faces/faces/view.xhtml 
         // the result would be simply view.xhtml.
         
         if ("".equals(prefix))
         {
             // if prefix is an empty string (Spring environment), we let it be "//"
             // in order to prevent an infinite loop in uri.startsWith(-emptyString-).
             // Furthermore a prefix of "//" is just another double slash prevention.
             prefix = "//";
         }
         else
         {
             // need to make sure its really /faces/* and not /facesPage.xhtml
             prefix = prefix + '/'; 
         }
         
         String uri = viewId;
         while (uri.startsWith(prefix) || uri.startsWith("//")) 
         {
             if (uri.startsWith(prefix))
             {
                 // cut off only /faces, leave the trailing '/' char for the next iteration
                 uri = uri.substring(prefix.length() - 1);
             }
             else
             {
                 // uri starts with '//' --> cut off the leading slash, leaving
                 // the second slash to compare for the next iteration
                 uri = uri.substring(1);
             }
         }
         
         //now delete any remaining leading '/'
         // TODO: CJH: I don't think this is correct, considering that getActionURL() expects everything to
         // start with '/', and in the suffix case we only mess with the suffix and leave leading
         // slashes alone.  Please review...
         /*if(uri.startsWith("/"))
         {
             uri = uri.substring(1);
         }*/
         
         return uri;
     }
     
     /**
      * Return the viewId with any non-standard suffix stripped off and replaced with
      * the default suffix configured for the specified context.
      * <p>
      * For example, an input parameter of "/foo.jsf" may return "/foo.jsp".
      * </p>
      */
     protected String handleSuffixMapping(FacesContext context, String requestViewId)
     {
         String[] faceletsViewMappings = _initialized ? _faceletsViewMappings : getFaceletsViewMappings(context);
         String[] jspDefaultSuffixes = _initialized ? _contextSuffixes : getContextSuffix(context);
         
         int slashPos = requestViewId.lastIndexOf('/');
         int extensionPos = requestViewId.lastIndexOf('.');
         
         StringBuilder builder = SharedStringBuilder.get(context, VIEW_HANDLER_SUPPORT_SB);
         
         //Try to locate any resource that match with the expected id
         for (String defaultSuffix : jspDefaultSuffixes)
         {
             //StringBuilder builder = new StringBuilder(requestViewId);
             builder.setLength(0);
             builder.append(requestViewId);
            
             if (extensionPos > -1 && extensionPos > slashPos)
             {
                 builder.replace(extensionPos, requestViewId.length(), defaultSuffix);
             }
             else
             {
                 builder.append(defaultSuffix);
             }
             String candidateViewId = builder.toString();
             
             if( faceletsViewMappings != null && faceletsViewMappings.length > 0 )
             {
                 for (String mapping : faceletsViewMappings)
                 {
                     if(mapping.startsWith("/"))
                     {
                         continue;   //skip this entry, its a prefix mapping
                     }
                     if(mapping.equals(candidateViewId))
                     {
                         return candidateViewId;
                     }
                     if(mapping.startsWith(".")) //this is a wildcard entry
                     {
                         builder.setLength(0); //reset/reuse the builder object 
                         builder.append(candidateViewId); 
                         builder.replace(candidateViewId.lastIndexOf('.'), candidateViewId.length(), mapping);
                         String tempViewId = builder.toString();
                         if(checkResourceExists(context,tempViewId))
                         {
                             return tempViewId;
                         }
                     }
                 }
             }
 
             // forced facelets mappings did not match or there were no entries in faceletsViewMappings array
             if(checkResourceExists(context,candidateViewId))
             {
                 return candidateViewId;
             }
         
         }
         
         //jsp suffixes didn't match, try facelets suffix
         String faceletsDefaultSuffix = _initialized ? _faceletsContextSufix : this.getFaceletsContextSuffix(context);
         if (faceletsDefaultSuffix != null)
         {
             for (String defaultSuffix : jspDefaultSuffixes)
             {
                 if (faceletsDefaultSuffix.equals(defaultSuffix))
                 {
                     faceletsDefaultSuffix = null;
                     break;
                 }
             }
         }
         if (faceletsDefaultSuffix != null)
         {
             //StringBuilder builder = new StringBuilder(requestViewId);
             builder.setLength(0);
             builder.append(requestViewId);
             
             if (extensionPos > -1 && extensionPos > slashPos)
             {
                 builder.replace(extensionPos, requestViewId.length(), faceletsDefaultSuffix);
             }
             else
             {
                 builder.append(faceletsDefaultSuffix);
             }
             
             String candidateViewId = builder.toString();
             if(checkResourceExists(context,candidateViewId))
             {
                 return candidateViewId;
             }
         }
 
         // Otherwise, if a physical resource exists with the name requestViewId let that value be viewId.
         if(checkResourceExists(context,requestViewId))
         {
             return requestViewId;
         }
         
         //Otherwise return null.
         return null;
     }
     
     protected boolean checkResourceExists(FacesContext facesContext, String viewId)
     {
         if (checkedViewIdsCache == null)
         {
             checkedViewIdsCache = CheckedViewIdsCache.getInstance(facesContext);
         }
 
         try
         {
             Boolean resourceExists = null;
             if (checkedViewIdsCache.isEnabled())
             {
                 resourceExists = checkedViewIdsCache.getCache().get(viewId);
             }
 
             if (resourceExists == null)
             {
                 ViewDeclarationLanguage vdl = facesContext.getApplication().getViewHandler()
                         .getViewDeclarationLanguage(facesContext, viewId);
                 if (vdl != null)
                 {
                     resourceExists = vdl.viewExists(facesContext, viewId);
                 }
                 else
                 {
                     // Fallback to default strategy
                     resourceExists = facesContext.getExternalContext().getResource(viewId) != null;
                 }
 
                 if (checkedViewIdsCache.isEnabled())
                 {
                     checkedViewIdsCache.getCache().put(viewId, resourceExists);
                 }
             }
 
             return resourceExists;
         }
         catch (MalformedURLException e)
         {
             //ignore and move on
         }     
         return false;
     }
 
 }