/*
 * Copyright (c) 2010 by Intevation GmbH
 *
 * This program is free software under the LGPL (>=v2.1)
 * Read the file LGPL.txt coming with the software for details
 * or visit http://www.gnu.org/licenses/ if it does not exist.
 */

package de.intevation.gnv.util;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Map;

import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerFactoryConfigurationError;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.apache.log4j.Logger;
import org.w3c.dom.Node;

/**
 * This xsl transformer is used to transform incoming xml documents with the
 * help of templates into a html representation.
 *
 * @author <a href="mailto:tim.englich@intevation.de">Tim Englich</a>
 */
public class XSLTransformer {

    /**
     * the logger, used to log exceptions and additonaly information
     */
    private static Logger log = Logger.getLogger(XSLTransformer.class);

    /**
     * The parameter that is required in the XSL sheet.
     */
    private Map<String, String> params;

    /**
     * Constructor
     */
    public XSLTransformer() {
        super();
    }

    /**
     * Turns <i>toTransform</i> into another format using the template <i>
     * templateFileName</i> with the <i>encoding</i>. The parameters added in
     * {@link #addParameter(java.lang.String, java.lang.String)} are available
     * in the transformer.
     *
     * @param toTransform The node to be transformed.
     * @param encoding The encoding to be used.
     * @param templateFileName The template used for transformation.
     * @return the transformed document as string.
     */
    public String transform(Node toTransform, String encoding,
                            String templateFileName) {
        String resultValue = null;
        try {
            Source templateSource = new StreamSource(new File(templateFileName));
            TransformerFactory xformFactory = TransformerFactory.newInstance();
            Transformer transformer = xformFactory
                    .newTransformer(templateSource);

            if (params != null) {
                for(Map.Entry<String, String> entry: params.entrySet()) {
                    transformer.setParameter(entry.getKey(), entry.getValue());
                }
            }

            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            StreamResult scrResult = new StreamResult(baos);
            // log.debug(xmlUtils.writeNode2String(toTransform));
            DOMSource source = new DOMSource(toTransform);
            transformer.transform(source, scrResult);
            resultValue = new String(baos.toByteArray(), encoding);
        } catch (TransformerConfigurationException e) {
            log.error(e, e);
        } catch (UnsupportedEncodingException e) {
            log.error(e, e);
        } catch (TransformerFactoryConfigurationError e) {
            log.error(e, e);
        } catch (TransformerException e) {
            log.error(e, e);
        }

        return resultValue;
    }


    /**
     * Add a parameter that is required in the XSL sheet.
     *
     * @param name The name of the parameter.
     * @param value The value of the parameter.
     */
    public void addParameter(String name, String value) {
        if (params == null) {
            params = new HashMap<String, String>(3);
        }

        params.put(name, value);
    }
}
// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :