/*
 * Copyright 1999-2004 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.
 */

/* $Id$ */

package servlets;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.StringReader;
import java.net.URL;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.URIResolver;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.stream.StreamSource;

import org.apache.commons.logging.impl.SimpleLog;
import org.apache.commons.logging.Log;

//FOP
import org.apache.fop.apps.FOUserAgent;
import org.apache.fop.apps.FOPException;
import org.apache.fop.apps.Fop;
import org.apache.fop.apps.FopFactory;
import org.apache.fop.apps.MimeConstants;
import org.apache.fop.servlet.ServletContextURIResolver;

/**
 * @author <a href="mailto:fop-dev@xml.apache.org">Apache XML FOP Development Team</a>
 * @version $Id: FopServlet.java,v 1.2 2003/03/07 09:48:05 jeremias Exp $
 * (todo) Ev. add caching mechanism for Templates objects
 */
public class GeneratePDF extends HttpServlet
{
    /** The TransformerFactory to use to create Transformer instances */
    protected TransformerFactory transFactory = null;

    /** The FopFactory used to create Fop instances */
    protected FopFactory fopFactory = null;

    /**
     * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest, HttpServletResponse)
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException
    {
        HttpSession session = request.getSession();

        try
        {
            // Get parameters
            String xml = session.getAttribute("xml").toString();
            String xslUrl = session.getAttribute("xslUrl").toString();

            // Analyze parameters and decide with method to use
            byte[] content = null;

            if ((xml != null) && (xslUrl != null))
            {
                content = renderXML(xml, xslUrl);
            }
            else
            {
                PrintWriter out = response.getWriter();
                out.println("<html><head><title>Error</title></head>\n"
                          + "<body><h1>FopServlet Error</h1><h3>No 'fo' "
                          + "request param given.</body></html>");
            }

            if (content != null)
            {
                //Send the result back to the client
                response.setContentType("application/pdf");
                response.setContentLength(content.length);
                response.getOutputStream().write(content);
                response.getOutputStream().flush();
                response.getOutputStream().close();
            }
        }
        catch (Exception ex)
        {
            throw new ServletException(ex);
        }
    }

    /**
     * Renders an XML file into a PDF file by applying a stylesheet
     * that converts the XML to XSL-FO. The PDF is written to a byte array
     * that is returned as the method's result.
     * @param xml the XML file
     * @param xslt the XSLT file
     * @throws FOPException If an error occurs during the rendering of the
     * XSL-FO
     * @throws TransformerException If an error occurs during XSL
     * transformation
     * @throws IOException In case of an I/O problem
     */
    protected byte[] renderXML(String xml, String xslt) throws FOPException, TransformerException, IOException
    {
        //Setup the XSL transformation
        StreamSource xslSrc = new StreamSource(xslt);
        System.out.println(xslSrc.toString());
        StreamSource xslSrc2 = new StreamSource(new StringReader(xslt));
        System.out.println(xslSrc2.toString());

        byte buf[] = null;
        URL xslUrl = new URL(xslt);
        InputStream in = new BufferedInputStream(xslUrl.openStream());
        ByteArrayOutputStream xslOut = new ByteArrayOutputStream();
        byte[] buffer = new byte[4096];
        for (int read=0; (read=in.read(buffer)) != -1; xslOut.write(buffer, 0, read));
        System.out.println(xslOut.toString());
        xslOut.close();
        in.close();

        TransformerFactory factory = TransformerFactory.newInstance();
        Transformer transformer = factory.newTransformer();

        FOUserAgent userAgent = fopFactory.newFOUserAgent();

        //Setup output
        ByteArrayOutputStream out = new ByteArrayOutputStream();

        //Setup FOP
        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, userAgent, out);
        fop.setOutputStream(out);

        Source src = new StreamSource(new StringReader(xml));

        //Make sure the XSL transformation's result is piped through to FOP
        Result res = new SAXResult(fop.getDefaultHandler());

        //Start the transformation and rendering process
        transformer.transform(src, res);

        return out.toByteArray();
    }
}