package com.jclark.xsl.sax;

import java.io.IOException;
import java.io.File;
import java.io.Writer;
import java.net.URL;
import java.util.Enumeration;
import javax.servlet.*;
import javax.servlet.http.*;
import org.xml.sax.*;

public class XSLServlet extends HttpServlet {
  private XSLProcessor cached;

  public void init() throws ServletException {
    String stylesheet = getInitParameter("stylesheet");
    if (stylesheet == null)
      throw new ServletException("missing stylesheet parameter");
    cached = new XSLProcessorImpl();
    cached.setParser(createParser());
    try {
      cached.loadStylesheet(new InputSource(getServletContext().getResource(stylesheet).toString()));
    }
    catch (SAXException e) {
      throw new ServletException(e);
    }
    catch (IOException e) {
      throw new ServletException(e);
    }
  }

  public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
    File inputFile = new File(request.getPathTranslated());
    if (!inputFile.isFile()) {
      inputFile = new File(request.getPathTranslated() + ".xml");
      if (!inputFile.isFile()) {
	response.sendError(HttpServletResponse.SC_NOT_FOUND,
			   "File not found: " + request.getPathTranslated());
	return;
      }
    }
    XSLProcessor xsl = (XSLProcessor)cached.clone();
    xsl.setParser(createParser());
    for (Enumeration e = request.getParameterNames(); e.hasMoreElements();) {
      String name = (String)e.nextElement();
      // What to do about multiple values?
      xsl.setParameter(name, request.getParameter(name));
    }
    OutputMethodHandlerImpl outputMethodHandler = new OutputMethodHandlerImpl(xsl);
    xsl.setOutputMethodHandler(outputMethodHandler);
    outputMethodHandler.setDestination(new ServletDestination(response));
    try {
      xsl.parse(fileInputSource(inputFile));
    }
    catch (SAXException e) {
      throw new ServletException(e);
    }
  }

  static Parser createParser() throws ServletException {
    String parserClass = System.getProperty("com.jclark.xsl.sax.parser");
    if (parserClass == null)
      parserClass = System.getProperty("org.xml.sax.parser");
    if (parserClass == null)
      parserClass = "com.jclark.xml.sax.CommentDriver";
    try {
      return (Parser)Class.forName(parserClass).newInstance();
    }
    catch (ClassNotFoundException e) {
      throw new ServletException(e);
    }
    catch (InstantiationException e) {
      throw new ServletException(e);
    }
    catch (IllegalAccessException e) {
      throw new ServletException(e);
    }
    catch (ClassCastException e) {
      throw new ServletException(parserClass + " is not a SAX driver");
    }
  }

  /**
   * Generates an <code>InputSource</code> from a file name.
   */

  static public InputSource fileInputSource(File file) {
    String path = file.getAbsolutePath();
    String fSep = System.getProperty("file.separator");
    if (fSep != null && fSep.length() == 1)
      path = path.replace(fSep.charAt(0), '/');
    if (path.length() > 0 && path.charAt(0) != '/')
      path = '/' + path;
    try {
      return new InputSource(new URL("file", "", path).toString());
    }
    catch (java.net.MalformedURLException e) {
      /* According to the spec this could only happen if the file
	 protocol were not recognized. */
      throw new Error("unexpected MalformedURLException");
    }
  }

}