/*
 * 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.markup.html.panel;

import org.apache.wicket.IQueueRegion;
import org.apache.wicket.markup.IMarkupFragment;
import org.apache.wicket.markup.html.MarkupUtil;
import org.apache.wicket.markup.html.WebMarkupContainer;
import org.apache.wicket.model.IModel;

/**
 * A panel is a reusable component that holds markup and other components.
 * <p>
 * Whereas WebMarkupContainer is an inline container like
 * 
 * <pre>
 *  ...
 *  <span wicket:id="xxx">
 *    <span wicket:id="mylabel">My label</span>
 *    ....
 *  </span>
 *  ...
 * </pre>
 * 
 * a Panel has its own associated markup file and the container content is taken from that file,
 * like:
 * 
 * <pre>
 *  <span wicket:id="mypanel"/>
 * 
 *  TestPanel.html
 *  <wicket:panel>
 *    <span wicket:id="mylabel">My label</span>
 *    ....
 *  </wicket:panel>
 * </pre>
 * 
 * @author Jonathan Locke
 * @author Juergen Donnerstag
 */
public abstract class Panel extends WebMarkupContainer implements IQueueRegion
{
	private static final long serialVersionUID = 1L;

	/** */
	public static final String PANEL = "panel";

	/**
	 * @see org.apache.wicket.Component#Component(String)
	 */
	public Panel(final String id)
	{
		super(id);
	}

	/**
	 * @see org.apache.wicket.Component#Component(String, IModel)
	 */
	public Panel(final String id, final IModel<?> model)
	{
		super(id, model);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	protected IMarkupSourcingStrategy newMarkupSourcingStrategy()
	{
		return new PanelMarkupSourcingStrategy(false);
	}
	
	/**
	 * Returns the markup inside <wicket:panel> tag.
	 * If such tag is not found, all the markup is returned.
	 * 
	 * @see IQueueRegion#getRegionMarkup() 
	 */
	@Override
	public IMarkupFragment getRegionMarkup()
	{
		IMarkupFragment markup = super.getRegionMarkup();
		
		if (markup == null)
		{
			return markup;
		}
		
		IMarkupFragment panelMarkup = MarkupUtil.findStartTag(markup, PANEL);
		
		return panelMarkup != null ? panelMarkup : markup;
	}
}