/*
    * $Id: Template.java 1419 2010-11-01 14:12:17Z hoheisel $
    *
    * Copyright (c) 2007
    * Fraunhofer Institute for Computer Architecture and Software Technology
    * See http://www.first.fraunhofer.de for more details.
    */
   
   package net.kwfgrid.gwes.servlet;
  
  import org.antlr.stringtemplate.StringTemplateGroup;
  import org.antlr.stringtemplate.StringTemplateGroupLoader;
  import org.antlr.stringtemplate.CommonGroupLoader;
  import org.antlr.stringtemplate.StringTemplateErrorListener;
  import org.antlr.stringtemplate.language.DefaultTemplateLexer;
  import org.apache.log4j.Logger;
  
  import java.util.Map;
  import java.util.HashMap;
  
  /**
   * Caches String template groups.
   * @author Andreas Hoheisel
   *         (<a href="http://www.andreas-hoheisel.de">www.andreas-hoheisel.de</a>)
   * @version $Id: Template.java 1419 2010-11-01 14:12:17Z hoheisel $
   */
  public class Template {
  
      final static Logger logger = Logger.getLogger(Template.class);
  
      private static Map<String,StringTemplateGroup> stringTemplateGroups;
  
      public static StringTemplateGroup getStringTemplateGroup(String templateFilename) {
          StringTemplateGroup ret;
          if (stringTemplateGroups == null) {
              stringTemplateGroups = new HashMap<String,StringTemplateGroup>();
          }
  
          ret = stringTemplateGroups.get(templateFilename);
          if (ret == null) {
              ret = loadSTGFileFromClasspath(templateFilename);
              stringTemplateGroups.put(templateFilename,ret);
          }
  
          return ret;
      }
  
  
      private static StringTemplateGroup loadSTGFileFromClasspath(String templateFilename) {
          logger.debug("Reading string template "+templateFilename);
          String location = "templates";
          StringTemplateGroupLoader loader = new CommonGroupLoader(location, new LogStringTemplateErrorListener());
          StringTemplateGroup.registerGroupLoader(loader);
          StringTemplateGroup.registerDefaultLexer(DefaultTemplateLexer.class);
          return StringTemplateGroup.loadGroup(templateFilename);
      }
  
      private static class LogStringTemplateErrorListener implements StringTemplateErrorListener {
  
          public void error(String msg, Throwable e) {
              logger.error(msg, e);
          }
  
          public void warning(String msg) {
              logger.warn(msg);
          }
      }
  
  
  
  }