/*
 * Copyright (C) The Apache Software Foundation. All rights reserved.
 *
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.txt file.  */

// Contributors:   Mathias Bogaert

package org.apache.log4j.xml;

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

/**
 * The output of the XMLLayout consists of a series of log4j:event
 * elements as defined in the log4j.dtd. It does not output a
 * complete well-formed XML file. The output is designed to be
 * included as an external entity in a separate file to form
 * a correct XML file.
 *
 * 
For example, if abc is the name of the file where
 * the XMLLayout ouput goes, then a well-formed XML file would be:
 *
  
   <?xml version="1.0" ?>
 
  <!DOCTYPE log4j:eventSet SYSTEM "log4j.dtd" [<!ENTITY data SYSTEM "abc">]>
 
  <log4j:eventSet version="1.2" xmlns:log4j="http://jakarta.apache.org/log4j/">
 	  &data;
  </log4j:eventSet>
  
 
 * 
This approach enforces the independence of the XMLLayout and the
 * appender where it is embedded.
 *
 * 
The version 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.
 *
 * @author Ceki  Gülcü
 * @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;
 
  /**
   * The LocationInfo 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.
   *
   * 
If you are embedding this layout within an {@link
   * org.apache.log4j.net.SMTPAppender} then make sure to set the
   * LocationInfo option of that appender as well.
   * */
  public void setLocationInfo(boolean flag) {
    locationInfo = flag;
  }
  
  /**
     Returns the current value of the LocationInfo option.
   */
  public boolean getLocationInfo() {
    return locationInfo;
  }
  
  /** No options to activate. */
  public void activateOptions() {
  }


  /**
   * Formats a {@link LoggingEvent} in conformance with the log4j.dtd.
   * */
  public String format(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("\r\n");

    buf.append("\r\n");       
    
    String ndc = event.getNDC();
    if(ndc != null) {
      buf.append("\r\n");       
    }
    
    String[] s = event.getThrowableStrRep();
    if(s != null) {
      buf.append("\r\n");
    }
    
    if(locationInfo) { 
      LocationInfo locationInfo = event.getLocationInformation();	
      buf.append("\r\n");
    }
    
    buf.append("\r\n\r\n");
    
    return buf.toString();
  }
  
  /**
     The XMLLayout prints and does not ignore exceptions. Hence the
     return value false.
  */
  public boolean ignoresThrowable() {
    return false;
  }
}