001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.wicket;
018
019import java.io.Serializable;
020import java.util.Collections;
021import java.util.Set;
022import java.util.TreeSet;
023import java.util.regex.Pattern;
024
025import org.apache.wicket.behavior.AttributeAppender;
026import org.apache.wicket.util.string.Strings;
027
028/**
029 * An AttributeModifier specialized in managing the <em>CSS class</em>
030 * attribute
031 */
032public abstract class ClassAttributeModifier extends AttributeAppender
033{
034        private static final Pattern SPLITTER = Pattern.compile("\\s+");
035
036        /**
037         * Constructor.
038         */
039        public ClassAttributeModifier()
040        {
041                super("class", null, " ");
042        }
043
044        @Override
045        protected Serializable newValue(String currentValue, String appendValue)
046        {
047                String[] classes;
048                if (Strings.isEmpty(currentValue))
049                {
050                        classes = new String[0];
051                }
052                else
053                {
054                        classes = SPLITTER.split(currentValue.trim());
055                }
056                Set<String> oldClasses = new TreeSet<>();
057                Collections.addAll(oldClasses, classes);
058
059                Set<String> newClasses = update(oldClasses);
060
061                String separator = getSeparator();
062                StringBuilder result = new StringBuilder();
063                for (String cls : newClasses)
064                {
065                        if (result.length() > 0)
066                        {
067                                result.append(separator);
068                        }
069                        result.append(cls);
070                }
071                return result.length() > 0 ? result.toString() : VALUELESS_ATTRIBUTE_REMOVE;
072        }
073
074        /**
075         * Callback to update the CSS class values for a tag.
076         *
077         * @param oldClasses
078         *          A set with the old class values
079         * @return A set with the new class values
080         */
081        protected abstract Set<String> update(Set<String> oldClasses);
082}