/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe 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 General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.common.xsl;
  
  import java.io.IOException;
  import java.net.URL;
  
  import javax.xml.parsers.ParserConfigurationException;
  import javax.xml.transform.sax.SAXSource;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.mycore.common.MCRCache;
  import org.mycore.common.MCRClassTools;
  import org.mycore.common.config.MCRConfigurationDir;
  import org.mycore.common.xml.MCREntityResolver;
  import org.mycore.common.xml.MCRXMLParserFactory;
  import org.mycore.common.xml.MCRXMLResource;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  
  /**
   * Represents an XSL file that will be used in XSL transformation and which is loaded
   * as a resource. The object provides helper methods to support caching of the compiled 
   * templates file.
   * 
   * @author Thomas Scheffler (yagee) 
   * @author Frank L\u00FCtzenkirchen
   */
  public class MCRTemplatesSource {
  
      private static final Logger LOGGER = LogManager.getLogger(MCRTemplatesSource.class);
  
      /** The path to the XSL resource */
      private String resource;
  
      /**
       * @param resource the path to the XSL file, which will be loaded as a resource
       */
      public MCRTemplatesSource(String resource) {
          this.resource = resource;
      }
  
      /** Have to use SAX here to resolve entities */
      public SAXSource getSource() throws SAXException, ParserConfigurationException {
          XMLReader reader = MCRXMLParserFactory.getNonValidatingParser().getXMLReader();
          reader.setEntityResolver(MCREntityResolver.instance());
          URL resourceURL = MCRConfigurationDir.getConfigResource(resource);
          if (resourceURL == null) {
              throw new SAXException("Could not find resource: " + resource);
          }
          InputSource input = new InputSource(resourceURL.toString());
          return new SAXSource(reader, input);
      }
  
      /** Returns the path to the XSL file, for use as a caching key */
      public String getKey() {
          return resource;
      }
  
      @Override
      public String toString() {
          return resource;
      }
  
      public URL getURL() {
          try {
              return MCRXMLResource.instance().getURL(resource, MCRClassTools.getClassLoader());
          } catch (IOException e) {
              LOGGER.warn("Could not determine URL of resource {}", resource, e);
              return null;
          }
      }
  
      /** Returns the timestamp the XSL file was last modified on the filesystem. */
      public long getLastModified() {
          try {
              return MCRXMLResource.instance().getLastModified(resource, MCRClassTools.getClassLoader());
          } catch (IOException e) {
              LOGGER.warn("Could not determine last modified date of resource {}", resource);
              return -1;
          }
     }
 
     public MCRCache.ModifiedHandle getModifiedHandle(long checkPeriod) {
         return MCRXMLResource.instance().getModifiedHandle(resource, MCRClassTools.getClassLoader(),
             checkPeriod);
     }
 }