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/*
 * This file is part of ***  M y C o R e  ***
 * See http://www.mycore.de/ for details.
 *
 * MyCoRe is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MyCoRe is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MyCoRe.  If not, see .
 */

package org.mycore.common.xsl;

import java.util.StringTokenizer;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.xalan.templates.ElemTemplate;
import org.apache.xalan.templates.ElemTemplateElement;
import org.apache.xalan.trace.GenerateEvent;
import org.apache.xalan.trace.SelectionEvent;
import org.apache.xalan.trace.TraceListener;
import org.apache.xalan.trace.TracerEvent;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

/**
 * Traces the execution of xsl stylesheet elements in debug mode. The trace
 * is written to the log, and in parallel as comment elements to the output
 * html.
 *
 * @author Frank L\u00FCtzenkirchen
 */
public class MCRTraceListener implements TraceListener {

    private static final Logger LOGGER = LogManager.getLogger(MCRTraceListener.class);

    /**
     * Traces the execution of xsl stylesheet elements in debug mode. The trace
     * is written to the log, and in parallel as comment elements to the output
     * html.
     */
    @Override
    public void trace(TracerEvent ev) {
        if (LOGGER.isDebugEnabled()) {
            ElemTemplateElement ete = ev.m_styleNode; // Current position in
            // stylesheet

            StringBuilder log = new StringBuilder();

            // Find the name of the stylesheet file currently processed
            try {
                StringTokenizer st = new StringTokenizer(ete.getBaseIdentifier(), "/\\");
                String stylesheet = null;
                while (st.hasMoreTokens()) {
                    stylesheet = st.nextToken();
                }
                if (stylesheet != null) {
                    log.append(" ").append(stylesheet);
                }
            } catch (Exception ignored) {
            }

            // Output current line number and column number
            log.append(" line ").append(ete.getLineNumber()).append(" col ").append(ete.getColumnNumber());

            // Find the name of the xsl:template currently processed
            try {
                ElemTemplate et = ev.m_processor.getCurrentTemplate();
                log.append(" in ');
            } catch (Exception ignored) {
            }

            // Output name of the xsl or html element currently processed
            log.append(' ').append(ete.getTagName());
            LOGGER.debug("Trace{}", log);

            // Output xpath of current xml source node in context
            StringBuilder path = new StringBuilder();
            Node node = ev.m_sourceNode;
            if (node != null) {
                path.append(node.getLocalName());
                while ((node = node.getParentNode()) != null) {
                    path.insert(0, node.getLocalName() + "/");
                }
            }
            if (path.length() > 0) {
                LOGGER.debug("Source {}", path);
            }
            try {
                if ("true".equals(ev.m_processor.getParameter("DEBUG"))) {
                    ev.m_processor.getResultTreeHandler().comment(log + " ");
                    if (path.length() > 0) {
                        ev.m_processor.getResultTreeHandler().comment(" source " + path + " ");
                    }
                }
            } catch (Exception ignored) {
            }
        }
    }

    /**
     * When a stylesheet generates characters, they will be logged in debug
     * mode.
     */
    @Override
    public void generated(GenerateEvent ev) {
        if (LOGGER.isDebugEnabled() && ev.m_eventtype == 12) {
            LOGGER.debug("Output {}", new String(ev.m_characters, ev.m_start, ev.m_length).trim());
        }
    }

    /**
     * When a stylesheet does a selection, like in <xsl:value-of /> or
     * similar elements, the selection element and xpath is logged in debug
     * mode.
     */
    @Override
    public void selected(SelectionEvent ev) {
        if (LOGGER.isDebugEnabled()) {
            String log = "Selection ";
            LOGGER.debug(log);
            try {
                if ("true".equals(ev.m_processor.getParameter("DEBUG"))) {
                    ev.m_processor.getResultTreeHandler().comment(" " + log + " ");
                }
            } catch (SAXException ignored) {
            }
        }
    }
}