package org.apache.cocoon.transformation;

import java.util.Map;
import java.io.IOException;
import javax.xml.parsers.ParserConfigurationException;
import org.apache.cocoon.Constants;
import org.apache.cocoon.Roles;
import org.apache.cocoon.environment.Session;
import org.apache.cocoon.environment.Request;
import org.apache.cocoon.environment.SourceResolver;
import org.apache.cocoon.ProcessingException;
import org.apache.cocoon.transformation.AbstractTransformer;
import org.apache.cocoon.xml.dom.DOMBuilder;
import org.apache.cocoon.components.parser.Parser;
import org.apache.avalon.framework.component.Composable;
import org.apache.avalon.framework.component.ComponentManager;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.avalon.excalibur.pool.Poolable;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;


/**
 * Make a DOM object from SAX events and write it to the session.
 *
 * Usage in sitemap:
 *    <map:transform type="writeDOMsession">
 *      <map:parameter name="dom-name" value="content"/>
 *      <map:parameter name="dom-root-element" value="companies"/>
 *    </map:transform>
 *
 * Where:
 *   dom-name is the name for the DOM object in the session
 *   dom-root-element is the trigger that will be the root element of the DOM
 *
 * @author <a href="mailto:sven.beauprez@the-ecorp.com">Sven Beauprez</a>
 * @version CVS $Revision: 1.6 $ $Date: 2001/06/18 09:11:59 $ $Author: sbeaupre $
 */

public class WriteDOMSessionTransformer extends AbstractTransformer implements Poolable, Composable {

    public static final String DOM_NAME = "dom-name";
    public static final String DOM_ROOT_ELEMENT = "dom-root-element";

    private boolean buildDom = false;
    private boolean sessionAvailable = false;

    private Session session;
    private Parameters parameters;
    private DOMBuilder builder;

    Parser parser;

    private String DOMName;
    private String rootElement;

    /** BEGIN SitemapComponent methods **/

    public void setup(SourceResolver resolver, Map objectModel,
                      String source, Parameters parameters)
    throws ProcessingException, SAXException, IOException {
      getLogger().debug("WriteSessionTransformer: setup");
      Request request = (Request)(objectModel.get(Constants.REQUEST_OBJECT));
      session = request.getSession(false);
      if (session != null) {
        DOMName = parameters.getParameter(WriteDOMSessionTransformer.DOM_NAME,null);
        rootElement = parameters.getParameter(WriteDOMSessionTransformer.DOM_ROOT_ELEMENT,null);
        if (DOMName!=null && rootElement!=null)  {
          //only now we know it is usefull to store something in the session
          getLogger().debug("WriteSessionTransformer: "+WriteDOMSessionTransformer.DOM_NAME + "=" +
                            DOMName + "; " + WriteDOMSessionTransformer.DOM_ROOT_ELEMENT + "=" +
                            rootElement);
          sessionAvailable = true;
        } else  {
          getLogger().error("WriteSessionTransformer: need " + WriteDOMSessionTransformer.DOM_NAME +
                            " and " + WriteDOMSessionTransformer.DOM_ROOT_ELEMENT + " parameters");
        }
      } else  {
        getLogger().error("WriteSessionTransformer: no session object");
      }
    }

    /** END SitemapComponent methods **/

    public void compose(ComponentManager manager) {
        try {
            getLogger().debug("Looking up " + Roles.PARSER);
            parser = (Parser)manager.lookup(Roles.PARSER);
        } catch (Exception e) {
            getLogger().error("Could not find component", e);
        }
    }


    /** BEGIN SAX ContentHandler handlers **/

    public void startPrefixMapping(String prefix, String uri)
    throws SAXException {
      super.startPrefixMapping(prefix,uri);
      if (buildDom)  {
        builder.startPrefixMapping(prefix,uri);
      }
    }

    public void startElement(String uri, String name, String raw, Attributes attributes)
    throws SAXException {
        //only build the DOM tree if session is available
        if (name.equalsIgnoreCase(rootElement) && sessionAvailable)  {
          getLogger().debug("WriteSessionTransformer: start building DOM tree");
          buildDom = true;
          builder = new DOMBuilder(parser);
          builder.startDocument();
          builder.startElement(uri,name,raw,attributes);
        } else if (buildDom)  {
          builder.startElement(uri,name,raw,attributes);
        } 
        super.contentHandler.startElement(uri,name,raw,attributes);
    }

    public void endElement(String uri, String name, String raw)
    throws SAXException {
        if (name.equalsIgnoreCase(rootElement) && sessionAvailable) {
          buildDom = false;
          builder.endElement(uri,name,raw);
          builder.endDocument();
          getLogger().debug("WriteSessionTransformer: putting DOM tree in session object");
          session.setAttribute(DOMName,builder.getDocument().getFirstChild());
          getLogger().debug("WriteSessionTransformer: DOM tree is in session object");
        } else if (buildDom)  {
          builder.endElement(uri,name,raw);
        }
        super.contentHandler.endElement(uri,name,raw);
    }


    public void characters(char c[], int start, int len)
    throws SAXException {
        if (buildDom)  {
          builder.characters(c,start,len);
        } 
        super.contentHandler.characters(c,start,len);
    }

    public void startCDATA()
    throws SAXException  {
      if (buildDom)  { 
        builder.startCDATA();
      }
      super.lexicalHandler.startCDATA();
    }
    
    public void endCDATA()  
    throws SAXException {
      if (buildDom)  {
        builder.endCDATA();
      }
      super.lexicalHandler.endCDATA();
    }

    /** END SAX ContentHandler handlers **/



}