//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.util.resource;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.net.URLConnection;
  import java.nio.channels.ReadableByteChannel;
  import java.security.Permission;
  
  import org.eclipse.jetty.util.URIUtil;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /* ------------------------------------------------------------ */
  /** Abstract resource class.
   */
  public class URLResource extends Resource
  {
      private static final Logger LOG = Log.getLogger(URLResource.class);
      protected final URL _url;
      protected final String _urlString;
      
      protected URLConnection _connection;
      protected InputStream _in=null;
      transient boolean _useCaches = Resource.__defaultUseCaches;
      
      /* ------------------------------------------------------------ */
      protected URLResource(URL url, URLConnection connection)
      {
          _url = url;
          _urlString=_url.toExternalForm();
          _connection=connection;
      }
      
      /* ------------------------------------------------------------ */
      protected URLResource (URL url, URLConnection connection, boolean useCaches)
      {
          this (url, connection);
          _useCaches = useCaches;
      }
  
      /* ------------------------------------------------------------ */
      protected synchronized boolean checkConnection()
      {
          if (_connection==null)
          {
              try{
                  _connection=_url.openConnection();
                  _connection.setUseCaches(_useCaches);
              }
              catch(IOException e)
              {
                  LOG.ignore(e);
              }
          }
          return _connection!=null;
      }
  
      /* ------------------------------------------------------------ */
      /** Release any resources held by the resource.
       */
      @Override
      public synchronized void close()
      {
          if (_in!=null)
          {
              try{_in.close();}catch(IOException e){LOG.ignore(e);}
              _in=null;
          }
  
          if (_connection!=null)
              _connection=null;
      }
  
      /* ------------------------------------------------------------ */
      /**
       * Returns true if the represented resource exists.
       */
      @Override
     public boolean exists()
     {
         try
         {
             synchronized(this)
             {
                 if (checkConnection() && _in==null )
                     _in = _connection.getInputStream();
             }
         }
         catch (IOException e)
         {
             LOG.ignore(e);
         }
         return _in!=null;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Returns true if the represented resource is a container/directory.
      * If the resource is not a file, resources ending with "/" are
      * considered directories.
      */
     @Override
     public boolean isDirectory()
     {
         return exists() && _urlString.endsWith("/");
     }
 
 
     /* ------------------------------------------------------------ */
     /**
      * Returns the last modified time
      */
     @Override
     public long lastModified()
     {
         if (checkConnection())
             return _connection.getLastModified();
         return -1;
     }
 
 
     /* ------------------------------------------------------------ */
     /**
      * Return the length of the resource
      */
     @Override
     public long length()
     {
         if (checkConnection())
             return _connection.getContentLength();
         return -1;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Returns an URL representing the given resource
      */
     @Override
     public URL getURL()
     {
         return _url;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Returns an File representing the given resource or NULL if this
      * is not possible.
      */
     @Override
     public File getFile()
         throws IOException
     {
         // Try the permission hack
         if (checkConnection())
         {
             Permission perm = _connection.getPermission();
             if (perm instanceof java.io.FilePermission)
                 return new File(perm.getName());
         }
 
         // Try the URL file arg
         try {return new File(_url.getFile());}
         catch(Exception e) {LOG.ignore(e);}
 
         // Don't know the file
         return null;    
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Returns the name of the resource
      */
     @Override
     public String getName()
     {
         return _url.toExternalForm();
     }
 
     
     /* ------------------------------------------------------------ */
     /**
      * Returns an input stream to the resource. The underlying 
      * url connection will be nulled out to prevent re-use.
      */
     @Override
     public synchronized InputStream getInputStream()
         throws java.io.IOException
     {
         return getInputStream (true); //backwards compatibility
     }
     
     
  
     /* ------------------------------------------------------------ */
     /**
      * Returns an input stream to the resource, optionally nulling
      * out the underlying url connection. If the connection is not
      * nulled out, a subsequent call to getInputStream() may return
      * an existing and already in-use input stream - this depends on
      * the url protocol. Eg JarURLConnection does not reuse inputstreams.
      * 
      * @param resetConnection if true the connection field is set to null
      * @return the inputstream for this resource
      * @throws IOException if unable to open the input stream
      */
     protected synchronized InputStream getInputStream(boolean resetConnection)
         throws IOException
     {
         if (!checkConnection())
             throw new IOException( "Invalid resource");
 
         try
         {    
             if( _in != null)
             {
                 InputStream in = _in;
                 _in=null;
                 return in;
             }
             return _connection.getInputStream();
         }
         finally
         {
             if (resetConnection)
             {
                 _connection=null;
                 if (LOG.isDebugEnabled()) LOG.debug("Connection nulled");
             }
         }
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public ReadableByteChannel getReadableByteChannel() throws IOException
     {
         return null;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Deletes the given resource
      */
     @Override
     public boolean delete()
         throws SecurityException
     {
         throw new SecurityException( "Delete not supported");
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Rename the given resource
      */
     @Override
     public boolean renameTo( Resource dest)
         throws SecurityException
     {
         throw new SecurityException( "RenameTo not supported");
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Returns a list of resource names contained in the given resource
      */
     @Override
     public String[] list()
     {
         return null;
     }
 
     /* ------------------------------------------------------------ */
     /**
      * Returns the resource contained inside the current resource with the
      * given name
      */
     @Override
     public Resource addPath(String path)
         throws IOException,MalformedURLException
     {
         if (path==null)
             return null;
 
         path = URIUtil.canonicalPath(path);
 
         return newResource(URIUtil.addPaths(_url.toExternalForm(),URIUtil.encodePath(path)), _useCaches);
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public String toString()
     {
         return _urlString;
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public int hashCode()
     {
         return _urlString.hashCode();
     }
     
     /* ------------------------------------------------------------ */
     @Override
     public boolean equals( Object o)
     {
         return o instanceof URLResource && _urlString.equals(((URLResource)o)._urlString);
     }
 
     /* ------------------------------------------------------------ */
     public boolean getUseCaches ()
     {
         return _useCaches;
     }
 
     /* ------------------------------------------------------------ */
     @Override
     public boolean isContainedIn (Resource containingResource) throws MalformedURLException
     {
         return false;
     }
 }