/*
    * 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.resource;
  
  import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import javax.faces.FacesException;
  import javax.faces.application.Resource;
  import javax.faces.context.FacesContext;
  import org.apache.myfaces.application.ResourceHandlerImpl;
  import org.apache.myfaces.shared.resource.ContractResourceLoader;
  import org.apache.myfaces.shared.resource.ContractResourceLoaderWrapper;
  import org.apache.myfaces.shared.resource.ResourceMeta;
  import org.apache.myfaces.shared.util.WebConfigParamUtils;
  
  /**
   * ResourceLoader that uses a temporal folder to cache resources, avoiding the problem
   * described on  MYFACES-3586 (Performance improvement in Resource loading - 
   * HIGH CPU inflating bytes in ResourceHandlerImpl.handleResourceRequest).
   *
   * @author Leonardo Uribe
   */
  public class TempDirFileCacheContractResourceLoader extends ContractResourceLoaderWrapper
  {
      
      public final static String TEMP_FILES_LOCK_MAP = "oam.rh.con.TEMP_FILES_LOCK_MAP";
      
      /**
       * Subdir of the ServletContext tmp dir to store temporal resources.
       */
      private static final String TEMP_FOLDER_BASE_DIR = "oam-rh-cache/";
  
      /**
       * Suffix for temporal files.
       */
      private static final String TEMP_FILE_SUFFIX = ".tmp";
      
      private final ContractResourceLoader delegate;
      
      private volatile File _tempDir;
      
      private int _resourceBufferSize = -1;
      
      public TempDirFileCacheContractResourceLoader(ContractResourceLoader delegate)
      {
          this.delegate = delegate;
          initialize();
      }
      
      protected void initialize()
      {
          //Get startup FacesContext
          FacesContext facesContext = FacesContext.getCurrentInstance();
      
          //1. Create temporal directory for temporal resources
          Map<String, Object> applicationMap = facesContext.getExternalContext().getApplicationMap();
          File tempdir = (File) applicationMap.get("javax.servlet.context.tempdir");
          File imagesDir = new File(tempdir, TEMP_FOLDER_BASE_DIR);
          if (!imagesDir.exists())
          {
              imagesDir.mkdirs();
          }
          else
          {
              //Clear the cache
              deleteDir(imagesDir);
              imagesDir.mkdirs();
          }
          _tempDir = imagesDir;
  
          //2. Create map for register temporal resources
          Map<String, FileProducer> temporalFilesLockMap = new ConcurrentHashMap<String, FileProducer>();
          facesContext.getExternalContext().getApplicationMap().put(TEMP_FILES_LOCK_MAP, temporalFilesLockMap);
     }
 
     private static boolean deleteDir(File dir)
     {
         if (dir.isDirectory())
         {
             String[] children = dir.list();
             for (int i = 0; i < children.length; i++)
             {
                 boolean success = deleteDir(new File(dir, children[i]));
                 if (!success)
                 {
                     return false;
                 }
             }
         }
         return dir.delete();
     }
     
     @Override
     public URL getResourceURL(ResourceMeta resourceMeta)
     {
         FacesContext facesContext = FacesContext.getCurrentInstance();
 
         if (resourceExists(resourceMeta))
         {
             File file = createOrGetTempFile(facesContext, resourceMeta);
             
             try
             {
                 return file.toURL();
             }
             catch (MalformedURLException e)
             {
                 throw new FacesException(e);
             }
         }
         else
         {
             return null;
         }
     }    
     
     public InputStream getResourceInputStream(ResourceMeta resourceMeta, Resource resource)
     {
         FacesContext facesContext = FacesContext.getCurrentInstance();
 
         if (resourceExists(resourceMeta))
         {
             File file = createOrGetTempFile(facesContext, resourceMeta);
             
             try
             {
                 return new BufferedInputStream(new FileInputStream(file));
             }
             catch (FileNotFoundException e)
             {
                 throw new FacesException(e);
             }
         }
         else
         {
             return null;
         }
     }
 
     @Override
     public InputStream getResourceInputStream(ResourceMeta resourceMeta)
     {
         return getResourceInputStream(resourceMeta, null);
     }
     
     @Override
     public boolean resourceExists(ResourceMeta resourceMeta)
     {
         return super.resourceExists(resourceMeta);
     }
 
     @SuppressWarnings("unchecked")
     private File createOrGetTempFile(FacesContext facesContext, ResourceMeta resourceMeta)
     {
         String identifier = resourceMeta.getResourceIdentifier()+"_"+resourceMeta.getContractName();
         File file = getTemporalFile(resourceMeta);
         if (!file.exists())
         {
             Map<String, FileProducer> map = (Map<String, FileProducer>) 
                 facesContext.getExternalContext().getApplicationMap().get(TEMP_FILES_LOCK_MAP);
 
             FileProducer creator = map.get(identifier);
             
             if (creator == null)
             {
                 synchronized(this)
                 {
                     creator = map.get(identifier);
                     
                     if (creator == null)
                     {
                         creator = new FileProducer();
                         map.put(identifier, creator);
                     }
                 }
             }
             
             if (!creator.isCreated())
             {
                 creator.createFile(facesContext, resourceMeta, file, this);
             }
         }
         return file;
     }    
     
     private File getTemporalFile(ResourceMeta resourceMeta)
     {
         return new File(_tempDir, 
             resourceMeta.getResourceIdentifier()+"_"+ resourceMeta.getContractName() + TEMP_FILE_SUFFIX);
     }
 
     protected void createTemporalFileVersion(FacesContext facesContext, ResourceMeta resourceMeta, File target)
     {
         target.mkdirs();  // ensure necessary directories exist
         target.delete();  // remove any existing file
 
         InputStream inputStream = null;
         FileOutputStream fileOutputStream;
         try
         {
             inputStream = getWrapped().getResourceInputStream(resourceMeta);
             fileOutputStream = new FileOutputStream(target);
             byte[] buffer = new byte[this.getResourceBufferSize()];
 
             pipeBytes(inputStream, fileOutputStream, buffer);
         }
         catch (FileNotFoundException e)
         {
             throw new FacesException("Unexpected exception while create file:", e);
         }
         catch (IOException e)
         {
             throw new FacesException("Unexpected exception while create file:", e);
         }
         finally
         {
             if (inputStream != null)
             {
                 try
                 {
                     inputStream.close();
                 }
                 catch (IOException e)
                 {
                     // Ignore
                 }
             }
         }
     }
     
     /**
      * Reads the specified input stream into the provided byte array storage and
      * writes it to the output stream.
      */
     private static void pipeBytes(InputStream in, OutputStream out, byte[] buffer) throws IOException
     {
         int length;
 
         while ((length = (in.read(buffer))) >= 0)
         {
             out.write(buffer, 0, length);
         }
     }
     
     public static class FileProducer 
     {
         
         public volatile boolean created = false;
         
         public FileProducer()
         {
             super();
         }
 
         public boolean isCreated()
         {
             return created;
         }
 
         public synchronized void createFile(FacesContext facesContext, 
             ResourceMeta resourceMeta, File file, TempDirFileCacheContractResourceLoader loader)
         {
             if (!created)
             {
                 loader.createTemporalFileVersion(facesContext, resourceMeta, file);
                 created = true;
             }
         }
     }
     
     protected int getResourceBufferSize()
     {
         if (_resourceBufferSize == -1)
         {
             _resourceBufferSize = WebConfigParamUtils.getIntegerInitParameter(
                 FacesContext.getCurrentInstance().getExternalContext(),
                 ResourceHandlerImpl.INIT_PARAM_RESOURCE_BUFFER_SIZE,
                 ResourceHandlerImpl.INIT_PARAM_RESOURCE_BUFFER_SIZE_DEFAULT);
         }
         return _resourceBufferSize;
     }
     
     public ContractResourceLoader getWrapped()
     {
         return delegate;
     }
 }