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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;

import java.util.Arrays;

/**
 * Manages the component queue.
 * 
 * @author igor
 */
class ComponentQueue
{
	private static final int INITIAL = 8;
	private static final int ADDITIONAL = 8;

	private Component[] queue;
	private int queueSize = 0;
	private boolean dirty = false;
	private String[] seen;
	private int seenSize = 0;

	void add(Component... components)
	{
		// TODO queueing this can be a more efficient implementation since we know the size of the
		// array
		for (Component component : components)
		{
			add(component);
		}
	}

	void add(Component component)
	{
		if (component == null)
		{
			throw new IllegalArgumentException("component cannot be null");
		}

		if (seen != null)
		{
			for (int i = 0; i < seenSize; i++)
			{
				if (seen[i].equals(component.getId()))
				{
					throw new WicketRuntimeException("A component with id: " + component.getId()
						+ " has already been queued");
				}
			}
		}

		if (dirty)
		{
			if (queueSize == 0)
			{
				queue = null;
			}
			else
			{
				Component[] replacement = new Component[queueSize + ADDITIONAL];
				int pos = 0;
				for (int i = 0; i < queue.length; i++)
				{
					if (queue[i] != null)
					{
						replacement[pos++] = queue[i];
					}
				}
				queue = replacement;
			}
		}

		if (queue == null)
		{
			queue = new Component[INITIAL];
		}
		else if (queue.length == queueSize)
		{
			queue = Arrays.copyOf(queue, queue.length + ADDITIONAL);
		}
		queue[queueSize] = component;
		queueSize++;

		if (seen == null)
		{
			seen = new String[INITIAL];
		}
		else if (seenSize == seen.length)
		{
			seen = Arrays.copyOf(seen, seen.length + ADDITIONAL);
		}
		seen[seenSize] = component.getId();
		seenSize++;
	}

	Component remove(String id)
	{
		int seen = 0;
		for (int i = 0; i < queue.length && seen < queueSize; i++)
		{
			Component component = queue[i];
			if (component != null)
			{
				seen++;
				if (component.getId().equals(id))
				{
					queue[i] = null;
					dirty = true;
					queueSize--;
					return component;
				}
			}
		}
		return null;
	}

	public boolean isEmpty()
	{
		return queueSize == 0;
	}

	public Component get(String id)
	{
		for (Component component : queue)
		{
			if (component != null && component.getId().equals(id))
			{
				return component;
			}
		}
		return null;
	}

	@Override
	public String toString()
	{
		return "ComponentQueue{" +
				"queueSize=" + queueSize +
				", queue=" + Arrays.toString(queue) +
				'}';
	}
}