/* Formatter.java
   -- a class for formatting log messages by localizing message texts
      and performing substitution of parameters
 
Copyright (C) 2002 Free Software Foundation, Inc.
 
This file is part of GNU Classpath.
 
GNU Classpath 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 2, or (at your option)
any later version.
 
GNU Classpath 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 GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.
 
Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
 
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version.
 
*/

package java.util.logging;

import java.util.ResourceBundle;
import java.text.MessageFormat;

/**
 * A <code>Formatter</code> supports LoggingHandlers by localizing
 * message texts and by subsituting parameter values for their
 * placeholders.
 *
 * <p>FIXME: Missing Javadoc.
 *
 * @author Sascha Brawer (brawer@acm.org)
 */
public abstract class Formatter
{
  /**
   * Constructs a new Formatter.
   */
  protected Formatter()
  {}

  public abstract String format(LogRecord record);

  public String getHead(Handler h)
  {
    return "";
  }

  public String getTail(Handler h)
  {
    return "";
  }

  /**
   * Formats the message part of a log record.
   *
   * <p>First, the Formatter localizes the record message to the
   * default locale by looking up the message in the record's
   * localization resource bundle.  If this step fails because there
   * is no resource bundle associated with the record, or because the
   * record message is not a key in the bundle, the raw message is
   * used instead.
   *
   * <p>Second, the Formatter substitutes appropriate strings for
   * the message parameters. If the record returns a non-empty
   * array for <code>getParameters()</code> and the localized
   * message string contains the character sequence "{0", the
   * formatter uses <code>java.text.MessageFormat</code> to format
   * the message.  Otherwise, no parameter substitution is performed.
   *
   * @param record the log record to be localized and formatted.
   *
   * @return the localized message text where parameters have been
   *         substituted by suitable strings.
   *
   * @throws NullPointerException if <code>record</code>
   *         is <code>null</code>.
   */
  public String formatMessage(LogRecord record)
  {
    String          msg;
    ResourceBundle  bundle;
    Object[]        params;

    /* This will throw a NullPointerExceptionif record is null. */
    msg = record.getMessage();
    if (msg == null)
      msg = "";

    /* Try to localize the message. */
    bundle = record.getResourceBundle();
    if (bundle != null)
    {
      try
      {
        msg = bundle.getString(msg);
      }
      catch (java.util.MissingResourceException _)
      {}
    }

    /* Format the message if there are parameters. */
    params = record.getParameters();
    if ((params != null)
        && (params.length > 0)
        && (msg.indexOf("{0") >= 0))
    {
      msg = MessageFormat.format(msg, params);
    }

    return msg;
  }
}