/*******************************************************************************

  * Copyright (c) 2008 Ketan Padegaonkar and others.

  * All rights reserved. This program and the accompanying materials

  * are made available under the terms of the Eclipse Public License v1.0

  * which accompanies this distribution, and is available at

  * http://www.eclipse.org/legal/epl-v10.html

  *

  * Contributors:

  *     Ketan Padegaonkar - initial API and implementation

  *     Hans Schwaebli - http://swtbot.org/bugzilla/show_bug.cgi?id=112

  *******************************************************************************/

 package org.eclipse.swtbot.swt.finder.utils;

 import java.util.Arrays;

 import java.util.LinkedHashMap;

 import java.util.Map;

 import java.util.Map.Entry;

 /**

  * Message formatter to optimize logging performance. The cost of logging is mostly in the string concatenation and

  * parameter evaluation of arguments. Log4j logs the object by invoking {@link #toString()} on the object being logged.

  * This class performs lazy evaluation of the message, only when {@link #toString()} is invoked, which happens at the

  * time of logging.

  * <p>

  * <b>Note:</b> This class uses a ThreadLocal cache instead of a single cache, since the cache would then need to be

  * synchronized since multiple threads would access it.

  * </p>

  * 

  * @author Ketan Padegaonkar <KetanPadegaonkar [at] gmail [dot] com>

  * @version $Id$

  */

 public class MessageFormat {

         private final String                                                                                                        pattern;

         private final Object[]                                                                                                        args;

         private static final ThreadLocal<Map<String, java.text.MessageFormat>>        threadLocal        = new ThreadLocal<Map<String, java.text.MessageFormat>>() {

                                                                                                                                                                                         protected java.util.Map<String, java.text.MessageFormat> initialValue() {

                                                                                                                                                                                                 return new LRUMap<String, java.text.MessageFormat>();

                                                                                                                                                                                         };

                                                                                                                                                                                 };

         private MessageFormat(String pattern, Object... args) {

                 this.pattern = pattern;

                 this.args = args;

         }

         public static MessageFormat format(String s, Object... args) {

                 return new MessageFormat(s, args);

         }

         public String toString() {

                 try {

                         java.text.MessageFormat formatter = formatter(pattern);

                         return formatter.format(args);

                 } catch (Exception e) {

                         return "MessageFormat: Could not translate message: '" + pattern + "' using arguments " + Arrays.asList(args); //$NON-NLS-1$ //$NON-NLS-2$

                 }

         }

         private java.text.MessageFormat formatter(String pattern) {

                 java.text.MessageFormat formatter = threadLocal.get().get(pattern);

                 if (formatter == null) {

                         formatter = new java.text.MessageFormat(pattern);

                         threadLocal.get().put(pattern, formatter);

                 }

                 return formatter;

         }

         private static final class LRUMap<K, V> extends LinkedHashMap<K, V> {

                 private static final int        MAX_SIZE        = 512;

                 protected boolean removeEldestEntry(Entry<K, V> eldest) {

                         return size() > MAX_SIZE;

                 }

         }

 }