/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

// Contributors:   Mathias Bogaert

package org.apache.log4j.xml;

import org.apache.log4j.Layout;
import org.apache.log4j.helpers.Transform;
import org.apache.log4j.spi.LocationInfo;
import org.apache.log4j.spi.LoggingEvent;

import java.util.Set;
import java.util.Arrays;

/**
 * The output of the XMLLayout consists of a series of log4j:event elements as
 * defined in the <a href="log4j.dtd">log4j.dtd</a>. It does not output a
 * complete well-formed XML file. The output is designed to be included as an
 * <em>external entity</em> in a separate file to form a correct XML file.
 *
 * <p>
 * For example, if <code>abc</code> is the name of the file where the XMLLayout
 * ouput goes, then a well-formed XML file would be:
 *
 * <pre>
  &lt;?xml version="1.0" ?&gt;

 &lt;!DOCTYPE log4j:eventSet PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd" [&lt;!ENTITY data SYSTEM "abc"&gt;]&gt;

 &lt;log4j:eventSet version="1.2" xmlns:log4j="http://jakarta.apache.org/log4j/"&gt;
	&nbsp;&nbsp;&data;
 &lt;/log4j:eventSet&gt;
 * </pre>
 * 
 * <p>
 * This approach enforces the independence of the XMLLayout and the appender
 * where it is embedded.
 *
 * <p>
 * The <code>version</code> attribute helps components to correctly intrepret
 * output generated by XMLLayout. The value of this attribute should be "1.1"
 * for output generated by log4j versions prior to log4j 1.2 (final release) and
 * "1.2" for relase 1.2 and later.
 *
 * Appenders using this layout should have their encoding set to UTF-8 or
 * UTF-16, otherwise events containing non ASCII characters could result in
 * corrupted log files.
 *
 * @author Ceki G&uuml;lc&uuml;
 * @since 0.9.0
 */
public class XMLLayout extends Layout {

    private final int DEFAULT_SIZE = 256;
    private final int UPPER_LIMIT = 2048;

    private StringBuffer buf = new StringBuffer(DEFAULT_SIZE);
    private boolean locationInfo = false;
    private boolean properties = false;

    /**
     * The <b>LocationInfo</b> option takes a boolean value. By default, it is set
     * to false which means there will be no location information output by this
     * layout. If the the option is set to true, then the file name and line number
     * of the statement at the origin of the log statement will be output.
     *
     * <p>
     * If you are embedding this layout within an
     * {@link org.apache.log4j.net.SMTPAppender} then make sure to set the
     * <b>LocationInfo</b> option of that appender as well.
     */
    public void setLocationInfo(boolean flag) {
	locationInfo = flag;
    }

    /**
     * Returns the current value of the <b>LocationInfo</b> option.
     */
    public boolean getLocationInfo() {
	return locationInfo;
    }

    /**
     * Sets whether MDC key-value pairs should be output, default false.
     * 
     * @param flag new value.
     * @since 1.2.15
     */
    public void setProperties(final boolean flag) {
	properties = flag;
    }

    /**
     * Gets whether MDC key-value pairs should be output.
     * 
     * @return true if MDC key-value pairs are output.
     * @since 1.2.15
     */
    public boolean getProperties() {
	return properties;
    }

    /** No options to activate. */
    public void activateOptions() {
    }

    /**
     * Formats a {@link org.apache.log4j.spi.LoggingEvent} in conformance with the
     * log4j.dtd.
     */
    public String format(final LoggingEvent event) {

	// Reset working buffer. If the buffer is too large, then we need a new
	// one in order to avoid the penalty of creating a large array.
	if (buf.capacity() > UPPER_LIMIT) {
	    buf = new StringBuffer(DEFAULT_SIZE);
	} else {
	    buf.setLength(0);
	}

	// We yield to the \r\n heresy.

	buf.append("<log4j:event logger=\"");
	buf.append(Transform.escapeTags(event.getLoggerName()));
	buf.append("\" timestamp=\"");
	buf.append(event.timeStamp);
	buf.append("\" level=\"");
	buf.append(Transform.escapeTags(String.valueOf(event.getLevel())));
	buf.append("\" thread=\"");
	buf.append(Transform.escapeTags(event.getThreadName()));
	buf.append("\">\r\n");

	buf.append("<log4j:message><![CDATA[");
	// Append the rendered message. Also make sure to escape any
	// existing CDATA sections.
	Transform.appendEscapingCDATA(buf, event.getRenderedMessage());
	buf.append("]]></log4j:message>\r\n");

	String ndc = event.getNDC();
	if (ndc != null) {
	    buf.append("<log4j:NDC><![CDATA[");
	    Transform.appendEscapingCDATA(buf, ndc);
	    buf.append("]]></log4j:NDC>\r\n");
	}

	String[] s = event.getThrowableStrRep();
	if (s != null) {
	    buf.append("<log4j:throwable><![CDATA[");
	    for (int i = 0; i < s.length; i++) {
		Transform.appendEscapingCDATA(buf, s[i]);
		buf.append("\r\n");
	    }
	    buf.append("]]></log4j:throwable>\r\n");
	}

	if (locationInfo) {
	    LocationInfo locationInfo = event.getLocationInformation();
	    buf.append("<log4j:locationInfo class=\"");
	    buf.append(Transform.escapeTags(locationInfo.getClassName()));
	    buf.append("\" method=\"");
	    buf.append(Transform.escapeTags(locationInfo.getMethodName()));
	    buf.append("\" file=\"");
	    buf.append(Transform.escapeTags(locationInfo.getFileName()));
	    buf.append("\" line=\"");
	    buf.append(locationInfo.getLineNumber());
	    buf.append("\"/>\r\n");
	}

	if (properties) {
	    Set keySet = event.getPropertyKeySet();
	    if (keySet.size() > 0) {
		buf.append("<log4j:properties>\r\n");
		Object[] keys = keySet.toArray();
		Arrays.sort(keys);
		for (int i = 0; i < keys.length; i++) {
		    String key = keys[i].toString();
		    Object val = event.getMDC(key);
		    if (val != null) {
			buf.append("<log4j:data name=\"");
			buf.append(Transform.escapeTags(key));
			buf.append("\" value=\"");
			buf.append(Transform.escapeTags(String.valueOf(val)));
			buf.append("\"/>\r\n");
		    }
		}
		buf.append("</log4j:properties>\r\n");
	    }
	}

	buf.append("</log4j:event>\r\n\r\n");

	return buf.toString();
    }

    /**
     * The XMLLayout prints and does not ignore exceptions. Hence the return value
     * <code>false</code>.
     */
    public boolean ignoresThrowable() {
	return false;
    }
}
