ReplacingResourceModel

/*
 * 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.
 */
package org.apache.wicket.model;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.wicket.Application;
import org.apache.wicket.Component;

/**
 * The ReplacingResourceModel is used to replaced other keys marked up like ${key} with their
 * corresponding values in the given key.The replacing mechanism also uses the default way to get
 * the localized String.<br>
 * <br>
 *
 * Example:<br>
 * <br>
 *
 * <pre>
 * key1=value of key1
 * key2=value of key2 contains ${key1}
 *
 * Label label = new Label("label",new ReplacingResourceModel("key2"));
 *
 * &lt;span wicket:id="label"&gt;&lt;span&gt;
 *
 * Output: value of key2 contains value of key1
 * </pre>
 *
 *
 * @author Tobias Soloschenko
 */
public class ReplacingResourceModel extends AbstractReadOnlyModel<String> implements
    IComponentAssignedModel<String>
{
    private static final long serialVersionUID = 1L;

    private final String resourceKey;


    public ReplacingResourceModel(String resourceKey)
    {
        this.resourceKey = resourceKey;
    }

    /**
     * @see org.apache.wicket.model.AbstractReadOnlyModel#getObject()
     */
    @Override
    public String getObject()
    {
        // this shouldn't be called always wrapped!
        return getReplacedResourceString(null);
    }

    /**
     * @see org.apache.wicket.model.IComponentAssignedModel#wrapOnAssignment(org.apache.wicket.Component)
     */
    @Override
    public IWrapModel<String> wrapOnAssignment(final Component component)
    {
        return new AssignmentWrapper(component);
    }

    /**
     *
     */
    private class AssignmentWrapper extends LoadableDetachableModel<String> implements
        IWrapModel<String>
    {
        private static final long serialVersionUID = 1L;

        private final Component component;

        /**
         * Construct.
         *
         * @param component
         */
        public AssignmentWrapper(Component component)
        {
            this.component = component;
        }

        /**
         * @see org.apache.wicket.model.IWrapModel#getWrappedModel()
         */
        @Override
        public IModel<String> getWrappedModel()
        {
            return ReplacingResourceModel.this;
        }

        @Override
        protected String load()
        {
            return getReplacedResourceString(component);
        }

        @Override
        protected void onDetach()
        {
            ReplacingResourceModel.this.detach();
        }

    }

    // The pattern to find keys in the given key value
    private static final Pattern PLACEHOLDER_PATTERN = Pattern.compile("\\$\\{(.*?)\\}");

    /**
     * Replaces all resource keys found in the given resourceKey with their localized values
     *
     * @param component
     *            the component to look for the resourceKey and all relating resource keys
     * @return the localized String
     */
    private String getReplacedResourceString(Component component)
    {
        String resourceKeyValue = Application.get()
            .getResourceSettings()
            .getLocalizer()
            .getString(resourceKey, component, null, null, null, (IModel<String>)null);

        StringBuffer output = new StringBuffer();

        Matcher matcher = ReplacingResourceModel.PLACEHOLDER_PATTERN.matcher(resourceKeyValue);
        // Search for placeholder to replace
        while (matcher.find())
        {
            String replacedPlaceHolder = Application.get()
                .getResourceSettings()
                .getLocalizer()
                .getString(matcher.group(1), component, null, null, null, (IModel<String>)null);
            matcher.appendReplacement(output, replacedPlaceHolder);
        }
        matcher.appendTail(output);
        return output.toString();
    }
}