/* Copyright (2007-2008) Schibsted Søk AS

  * This file is part of SESAT.

  *

  *   SESAT is free software: you can redistribute it and/or modify

  *   it under the terms of the GNU Affero General Public License as published by

  *   the Free Software Foundation, either version 3 of the License, or

  *   (at your option) any later version.

  *

  *   SESAT is distributed in the hope that it will be useful,

  *   but WITHOUT ANY WARRANTY; without even the implied warranty of

  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  *   GNU Affero General Public License for more details.

  *

  *   You should have received a copy of the GNU Affero General Public License

  *   along with SESAT.  If not, see <http://www.gnu.org/licenses/>.

  */

 package no.sesat.search.view.velocity;

 import java.io.IOException;

 import java.net.URL;

 import java.net.MalformedURLException;

 import java.io.InputStream;

 import java.util.regex.Matcher;

 import no.sesat.search.http.HTTPClient;

 import no.sesat.search.site.config.UrlResourceLoader;

 import no.sesat.search.site.Site;

 import org.apache.log4j.Logger;

 import org.apache.velocity.runtime.resource.Resource;

 import org.apache.velocity.runtime.resource.loader.ResourceLoader;

 import org.apache.velocity.exception.ResourceNotFoundException;

 import org.apache.commons.collections.ExtendedProperties;

 /**

  * This is a simple URL-based loader.

  * ORIGINAL FROM http://svn.apache.org/repos/asf/jakarta/velocity/engine/trunk/whiteboard/geir/URLResourceLoader.java

  *

  * original version Id: URLResourceLoader.java,v 1.3 2004/03/19 17:13:40 dlr Exp

  *

  *

  *

  * MODIFIED TO SUIT SCHIBSTEDSØK's NEEDS.

  * There was a choice here to implement all the URL handling stuff from scratch or to plug into the existing

  * functionality found in no.schibstedsøk.front.search.configuration.loader

  * Since this class is hidden between the velocity API it made more sense to go from scratch to best

  * meet velocity's requirements...

  *

  *

  * @version $Id: URLResourceLoader.java,v 1.3 2004/03/19 17:13:40 dlr Exp $

  */

 public class URLResourceLoader extends ResourceLoader {

     public interface Context{

         boolean doesUrlExist(final URL url);

         URL getURL(final String resource, final Site site);

     }

     // Constants -----------------------------------------------------

     private static final Logger LOG = Logger.getLogger(URLResourceLoader.class);

     private static final String ERR_RESOURCE_NOT_FOUND = "Cannot find resource ";

     private static final String DEBUG_LOOKING_FOR = "Looking for ";

     private static final String DEBUG_EXISTS = "Positive HEAD on ";

     private static final String DEBUG_FULL_URL_IS = "Real URL is ";

     private static final String DEBUG_HOST_HEADER_IS = "URL's host-header is ";

     private static final String DEBUG_DOESNT_EXIST = "Using fallback URL";

     // Attributes ----------------------------------------------------

     private Site site;

     // Static --------------------------------------------------------

     private static Context context = new DefaultContext();

     // Allows the tests to switch the Velocity ResourceLoader over to a file based one.

     static void setContext(final Context context){

         URLResourceLoader.context = context;

     }

     // Constructors --------------------------------------------------

     public URLResourceLoader(){}

     public URLResourceLoader(final Site site){

         this.site= site;

     }

     // Public --------------------------------------------------------

     /** {@inheritDoc}

      */

     public void init(final ExtendedProperties configuration) {

         // the engine's properties actually come from the RuntimeServices *not* the ExtendedProperties

         site = (Site)rsvc.getProperty(Site.NAME_KEY);

     }

     /**

      * Get an InputStream so that the Runtime can build a

      * template with it.

      *

      * @param url  url of template to fetch bytestream of

      * @return InputStream containing the template

      * @throws ResourceNotFoundException if template not found

      *         in the file template path.

      */

      public /*synchronized*/ InputStream getResourceStream(final String url) throws ResourceNotFoundException{

         LOG.trace("start getResourceStream( " + url + " )");

         try{

             synchronized( url.intern() ){

                 return getStream(findUrl(url, site));

             }

         }catch( IOException e ){

             throw new ResourceNotFoundException( ERR_RESOURCE_NOT_FOUND + url );

         }

     }

     /** {@inheritDoc}

      */

     public boolean isSourceModified(Resource resource){

         final boolean result =  getLastModified(resource) > resource.getLastModified();

         LOG.debug("isSourceModified( "+resource.getName()+" ): "+result);

         return result;

     }

     /** {@inheritDoc}

      */

     public long getLastModified(Resource resource){

         try{

             final URL url = findUrl(resource.getName(), site);

             final HTTPClient client = HTTPClient.instance(url, "localhost");

             return client.getLastModified("");

         }catch( ResourceNotFoundException e ){

             LOG.error( ERR_RESOURCE_NOT_FOUND + resource.getName() );

         }catch( IOException e ){

             LOG.error( ERR_RESOURCE_NOT_FOUND + resource.getName() );

         }

         return 0;

     }

     // Package protected ---------------------------------------------

     // Protected -----------------------------------------------------

     // Private -------------------------------------------------------

     private static URL findUrl(final String url, final Site currentSite) throws ResourceNotFoundException{

         try{

             LOG.trace(DEBUG_LOOKING_FOR + url );

             return findUrlImpl(url, currentSite);

         }catch( IOException e ){

             throw new ResourceNotFoundException( ERR_RESOURCE_NOT_FOUND + url );

         }

     }

     private static URL findUrlImpl(final String url, final Site currentSite)

             throws IOException, ResourceNotFoundException {

         final URL u = context.getURL(url, currentSite);

         if (context.doesUrlExist(u)) {

             return u;

         } else {

             final Site parent = currentSite.getParent();

             if (null == parent) {

                 throw new ResourceNotFoundException( ERR_RESOURCE_NOT_FOUND + url );

             }

             if (LOG.isTraceEnabled()) {

                 LOG.trace(DEBUG_DOESNT_EXIST + parent.getName());

             }

             // Recursively look for the resource in ancestor sites.

             return findUrlImpl(getFallbackURL(url, currentSite, parent), parent);

         }

     }

     private static String getFallbackURL(final String url, final Site currSite, final Site ancestorSite) {

         final String oldUrl = currSite.getName() + currSite.getConfigContext();

         final String newUrl = ancestorSite.getName() + ancestorSite.getConfigContext();

         return url.replaceFirst(Matcher.quoteReplacement(oldUrl), newUrl);

     }

     private static InputStream getStream(final URL url) throws IOException{

         final HTTPClient client = HTTPClient.instance(url, "localhost");

         try{

             return client.getBufferedStream("");

         }catch(IOException ioe){

             throw client.interceptIOException(ioe);

         }

     }

     // Inner classes -------------------------------------------------

     private static final class DefaultContext implements Context{

         public boolean doesUrlExist(final URL url) {

             return UrlResourceLoader.doesUrlExist(url);

         }

         public URL getURL(final String resource, final Site site) {

             try {

                 return new URL(resource);

             } catch (MalformedURLException e) {

                 throw new ResourceNotFoundException(e);

             }

         }

     }

 }