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Wicket is a Java web application framework that takes simplicity, separation of concerns and ease of development to a whole new level. Wicket pages can be mocked up, previewed and later revised using standard WYSIWYG HTML design tools. Dynamic content processing and form handling is all handled in Java code using a first-class component model backed by POJO data beans that can easily be persisted using your favorite technology.

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/*
 * 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.parser.filter;

import java.text.ParseException;
import java.util.Stack;

import org.apache.wicket.Component;
import org.apache.wicket.MarkupContainer;
import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.MarkupElement;
import org.apache.wicket.markup.MarkupResourceStream;
import org.apache.wicket.markup.MarkupStream;
import org.apache.wicket.markup.WicketParseException;
import org.apache.wicket.markup.WicketTag;
import org.apache.wicket.markup.html.internal.Enclosure;
import org.apache.wicket.markup.parser.AbstractMarkupFilter;
import org.apache.wicket.markup.resolver.IComponentResolver;


/**
 * This is a markup inline filter. It identifies <wicket:enclosure> tags. If the 'child'
 * attribute is empty it determines the wicket:id of the child component automatically by analyzing
 * the wicket component (in this case on one wicket component is allowed) in between the open and
 * close tags. If the enclosure tag has a 'child' attribute like
 * <wicket:enclosure child="xxx"> than more than just one wicket component inside
 * the enclosure tags are allowed and the child component which determines the visibility of the
 * enclosure is identified by the 'child' attribute value which must be equal to the relative child
 * id path.
 * 
 * @see EnclosureResolver
 * @see Enclosure
 * 
 * @author Juergen Donnerstag
 */
public final class EnclosureHandler extends AbstractMarkupFilter implements IComponentResolver
{
	private static final long serialVersionUID = 1L;

	/** */
	public static final String ENCLOSURE = "enclosure";

	/** The child attribute */
	public static final String CHILD_ATTRIBUTE = "child";

	/** Stack of  tags */
	private Stack stack;

	/** The id of the first wicket tag inside the enclosure */
	private String childId;

	/**
	 * Construct.
	 */
	public EnclosureHandler()
	{
		this(null);
	}

	public EnclosureHandler(MarkupResourceStream resourceStream)
	{
		super(resourceStream);
	}

	@Override
	protected final MarkupElement onComponentTag(ComponentTag tag) throws ParseException
	{
		final boolean isWicketTag = tag instanceof WicketTag;
		final boolean isEnclosureTag = isWicketTag && ((WicketTag)tag).isEnclosureTag();

		// If wicket:enclosure
		if (isEnclosureTag)
		{
			// If open tag, than put the tag onto the stack
			if (tag.isOpen())
			{
				if (stack == null)
				{
					stack = new Stack();
				}
				stack.push(tag);
			}
			// If close tag, then remove the tag from the stack and update
			// the child attribute of the open tag if required
			else if (tag.isClose())
			{
				if (stack == null)
				{
					throw new WicketParseException("Missing open tag for Enclosure:", tag);
				}

				// Remove the open tag from the stack
				ComponentTag lastEnclosure = stack.pop();

				// If the child attribute has not been given by the user,
				// then ...
				if (childId != null)
				{
					lastEnclosure.put(CHILD_ATTRIBUTE, childId);
					lastEnclosure.setModified(true);
					childId = null;
				}

				if (stack.size() == 0)
				{
					stack = null;
				}
			}
			else
			{
				throw new WicketParseException("Open-close tag not allowed for Enclosure:", tag);
			}
		}
		// Are we inside a wicket:enclosure tag?
		else if (stack != null)
		{
			ComponentTag lastEnclosure = stack.lastElement();

			// If the enclosure tag has NO child attribute, then ...
			if (lastEnclosure.getAttribute(CHILD_ATTRIBUTE) == null)
			{
				String id = tag.getAttribute(getWicketNamespace() + ":id");
				if (id != null)
				{
					// We encountered more than one child component inside
					// the enclosure and are not able to automatically
					// determine the child component to delegate the
					// isVisible() to => Exception
					if (childId != null)
					{
						throw new WicketParseException("Use <" + getWicketNamespace() +
							":enclosure child='xxx'> to name the child component:", tag);
					}
					// Remember the child id. The open tag will be updated
					// once the close tag is found. See above.
					childId = id;
				}
			}
		}

		return tag;
	}

	@Override
	public Component resolve(final MarkupContainer container, final MarkupStream markupStream,
		final ComponentTag tag)
	{
		if ((tag instanceof WicketTag) && ((WicketTag)tag).isEnclosureTag())
		{
			// Yes, we handled the tag
			return new Enclosure(tag.getId() + container.getPage().getAutoIndex(),
				tag.getAttribute(EnclosureHandler.CHILD_ATTRIBUTE));
		}

		// We were not able to handle the tag
		return null;
	}
}