/*
 * Copyright 1999-2005 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 org.apache.fop.servlet;

import java.io.File;
import java.io.InputStream;
import java.io.PrintWriter;

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

// XML
import org.apache.commons.logging.impl.SimpleLog;
import org.apache.fop.apps.Fop;
import org.apache.fop.apps.MimeConstants;


/**
 * Example servlet to generate a fop printout from a servlet.
 * Printing goes to the default printer on host where the servlet executes.
 * Servlet param is:
 * <ul>
 *   <li>fo: the path to a XSL-FO file to render
 * </ul>
 * or
 * <ul>
 *   <li>xml: the path to an XML file to render</li>
 *   <li>xslt: the path to an XSLT file that can transform the above XML to XSL-FO</li>
 * </ul>
 * <br/>
 * Example URL: http://servername/fop/servlet/FopPrintServlet?fo=readme.fo
 * <br/>
 * Example URL: http://servername/fop/servlet/FopPrintServlet?xml=data.xml&xsl=format.xsl
 *
 * @author <a href="mailto:fop-dev@xml.apache.org">Apache XML FOP Development Team</a>
 * @version $Id$
 * (todo) Doesn't work since there's no AWTRenderer at the moment. Revisit when
 * available.
 * (todo) Ev. add caching mechanism for Templates objects
 */
public class FopPrintServlet extends HttpServlet {

    /** Name of the parameter used for the XSL-FO file */
    protected static final String FO_REQUEST_PARAM = "fo";
    /** Name of the parameter used for the XML file */
    protected static final String XML_REQUEST_PARAM = "xml";
    /** Name of the parameter used for the XSLT file */
    protected static final String XSLT_REQUEST_PARAM = "xslt";

    /** Logger to give to FOP */
    protected SimpleLog log = null;
    
    /** The TransformerFactory to use to create Transformer instances */
    protected TransformerFactory transFactory = null;

    /**
     * @see javax.servlet.GenericServlet#init()
     */
    public void init() throws ServletException {
        this.log = new SimpleLog("FOP/Print Servlet");
        log.setLevel(SimpleLog.LOG_LEVEL_WARN);
        this.transFactory = TransformerFactory.newInstance();
    }

    /**
     * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest, HttpServletResponse)
     */
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response) throws ServletException {
        if (log == null) {
            log = new SimpleLog("FOP/Print Servlet");
            log.setLevel(SimpleLog.LOG_LEVEL_WARN);
        }

        try {
            String foParam = request.getParameter(FO_REQUEST_PARAM);
            String xmlParam = request.getParameter(XML_REQUEST_PARAM);
            String xsltParam = request.getParameter(XSLT_REQUEST_PARAM);

            if (foParam != null) {
                InputStream file = new java.io.FileInputStream(foParam);
                renderFO(file, response);
            } else if ((xmlParam != null) && (xsltParam != null)) {
                renderXML(new File(xmlParam), new File(xsltParam), response);
            } else {
                response.setContentType("text/html");

                PrintWriter out = response.getWriter();
                out.println("<html><title>Error</title>\n"
                        + "<body><h1>FopServlet Error</h1>\n"
                        + "<h3>No 'fo' or 'xml/xsl' "
                        + "request param given.</h3></body>\n</html>");
            }
        } catch (ServletException ex) {
            throw ex;
        } catch (Exception ex) {
            throw new ServletException(ex);
        }
    }

    /**
     * Renders an FO inputsource to the default printer.
     * @param foFile The XSL-FO file
     * @param response Response to write to
     * @throws ServletException In case of a problem
     */
    public void renderFO(InputStream foFile,
                         HttpServletResponse response) throws ServletException {
        try {
            Fop fop = new Fop(MimeConstants.MIME_FOP_PRINT);

            // Setup JAXP
            TransformerFactory factory = TransformerFactory.newInstance();
            Transformer transformer = factory.newTransformer(); //identity transformer
            
            // Setup input for XSLT transformation
            Source src = new StreamSource(foFile);
            
            // Resulting SAX events (the generated FO) must be piped through to FOP
            Result res = new SAXResult(fop.getDefaultHandler());
            
            // Start XSLT transformation and FOP processing
            transformer.transform(src, res);
            
            reportOK (response);
        } catch (Exception ex) {
            throw new ServletException(ex);
        }
    }

    /**
     * Renders an FO generated using an XML and a stylesheet to the default printer.
     * @param xmlfile XML file object
     * @param xsltfile XSLT stylesheet 
     * @param response HTTP response object
     * @throws ServletException In case of a problem
     */
    public void renderXML(File xmlfile, File xsltfile,
                          HttpServletResponse response) throws ServletException {
        try {
            Fop fop = new Fop(MimeConstants.MIME_FOP_PRINT);

            // Setup XSLT
            TransformerFactory factory = TransformerFactory.newInstance();
            Transformer transformer = factory.newTransformer(new StreamSource(xsltfile));
            
            // Setup input for XSLT transformation
            Source src = new StreamSource(xmlfile);
        
            // Resulting SAX events (the generated FO) must be piped through to FOP
            Result res = new SAXResult(fop.getDefaultHandler());

            // Start XSLT transformation and FOP processing
            transformer.transform(src, res);

            reportOK (response);
        } catch (Exception ex) {
            throw new ServletException(ex);
        }
    }

    // private helper, tell (browser) user that file printed
    private void reportOK(HttpServletResponse response)
                throws ServletException {
        String sMsg = "<html><title>Success</title>\n"
                + "<body><h1>FopPrintServlet: </h1>"
                + "<h3>The requested data was printed</h3></body></html>";

        response.setContentType("text/html");
        response.setContentLength(sMsg.length());

        try {
            PrintWriter out = response.getWriter();
            out.println(sMsg);
            out.flush();
        } catch (Exception ex) {
            throw new ServletException(ex);
        }
    }
}