/*
    * Copyright 2002,2004 The Apache Software Foundation.
    *
    * Licensed 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.commons.jelly.tags.jsl;
  
  import org.apache.commons.jelly.JellyTagException;
  import org.apache.commons.jelly.XMLOutput;
  import org.apache.commons.jelly.xpath.XPathSource;
  import org.apache.commons.jelly.xpath.XPathTagSupport;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.dom4j.rule.Rule;
  import org.dom4j.rule.Stylesheet;
  import org.jaxen.JaxenException;
  import org.jaxen.XPath;
  
  
  /***
   * This tag implements a JSL stylesheet which is similar to an
   * XSLT stylesheet but can use Jelly tags inside it
   *
   * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
   * @version $Revision: 155420 $
   */
  public class StylesheetTag extends XPathTagSupport implements XPathSource {
  
      /*** The Log to which logging calls will be made. */
      private Log log = LogFactory.getLog(StylesheetTag.class);
  
  
      /*** Holds the stylesheet which will be applied to the source context. */
      private Stylesheet stylesheet;
  
      /*** Holds value of property mode. */
      private String mode;
  
      /*** The variable which the stylesheet will be output as */
      private String var;
  
      /*** The XPath expression to evaluate. */
      private XPath select;
  
      /*** The XPath source used by TemplateTag and ApplyTemplatesTag to pass XPath contexts */
      private Object xpathSource;
  
      public StylesheetTag() {
      }
  
  
      /***
       * @return the XMLOutput from the stylesheet if available
       */
      public XMLOutput getStylesheetOutput() {
          if (stylesheet instanceof JellyStylesheet) {
              JellyStylesheet jellyStyle = (JellyStylesheet) stylesheet;
              return jellyStyle.getOutput();
          }
          return null;
      }
  
      /***
       * Sets the XMLOutput to use by the current stylesheet
       */
      public void setStylesheetOutput(XMLOutput output) {
          if (stylesheet instanceof JellyStylesheet) {
              JellyStylesheet jellyStyle = (JellyStylesheet) stylesheet;
              jellyStyle.setOutput(output);
          }
      }
  
      /***
       * Adds a new template rule to this stylesheet
       */
      public void addTemplate( Rule rule ) {
          getStylesheet().addRule( rule );
      }
  
      // XPathSource interface
      //-------------------------------------------------------------------------
  
      /***
       * @return the current XPath iteration value
       *  so that any other XPath aware child tags to use
       */
      public Object getXPathSource() {
          return xpathSource;
      }
 
 
     // Tag interface
     //-------------------------------------------------------------------------
     public void doTag(XMLOutput output) throws JellyTagException {
         stylesheet = createStylesheet(output);
 
         // run the body to add the rules
         invokeBody(output);
         stylesheet.setModeName(getMode());
 
         if (var != null) {
             context.setVariable(var, stylesheet);
         }
         else {
 
             //dom4j seems to only throw generic Exceptions
             try {
                 Object source = getSource();
 
                 if (log.isDebugEnabled()) {
                     log.debug("About to evaluate stylesheet on source: " + source);
                 }
 
                 stylesheet.run(source);
             }
             catch (Exception e) {
                 throw new JellyTagException(e);
             }
 
         }
     }
 
 
     // Properties
     //-------------------------------------------------------------------------
 
     /***
      * Getter for property mode.
      * @return Value of property mode.
      */
     public String getMode() {
         return mode;
     }
 
     /***
      * Sets the mode.
      * @param mode New value of property mode.
      */
     public void setMode(String mode) {
         this.mode = mode;
     }
 
     public Stylesheet getStylesheet() {
         return stylesheet;
     }
 
     /*** Sets the variable name to define for this expression
      */
     public void setVar(String var) {
         this.var = var;
     }
 
     /*** Sets the XPath expression to evaluate. */
     public void setSelect(XPath select) {
         this.select = select;
     }
 
     // Implementation methods
     //-------------------------------------------------------------------------
 
     /*** @return the source on which the stylesheet should run
      */
     protected Object getSource() throws JaxenException {
         Object source = getXPathContext();
         if ( select != null ) {
             return select.evaluate(source);
         }
         return source;
     }
 
 
     /***
      * Factory method to create a new stylesheet
      */
     protected Stylesheet createStylesheet(final XMLOutput output) {
         JellyStylesheet answer = new JellyStylesheet();
         answer.setOutput(output);
         return answer;
     }
 
     /***
      * Sets the xpathSource.
      * @param xpathSource The xpathSource to set
      */
     void setXPathSource(Object xpathSource) {
         this.xpathSource = xpathSource;
     }
 
 }