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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.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.wicket.css.ICssCompressor;
import org.apache.wicket.javascript.IJavaScriptCompressor;
import org.apache.wicket.markup.head.CssHeaderItem;
import org.apache.wicket.markup.head.CssReferenceHeaderItem;
import org.apache.wicket.markup.head.HeaderItem;
import org.apache.wicket.markup.head.IReferenceHeaderItem;
import org.apache.wicket.markup.head.JavaScriptHeaderItem;
import org.apache.wicket.markup.head.JavaScriptReferenceHeaderItem;
import org.apache.wicket.request.resource.CssResourceReference;
import org.apache.wicket.request.resource.JavaScriptResourceReference;
import org.apache.wicket.request.resource.ResourceReference;
import org.apache.wicket.request.resource.ResourceReferenceRegistry;
import org.apache.wicket.resource.bundles.ConcatResourceBundleReference;
import org.apache.wicket.util.lang.Args;

/**
 * Contains all resource bundles that are registered in the application. Resource bundles provide a
 * way to combine multiple resources into one, reducing the number of requests needed to load a
 * page. The code using the resources does not need to know about the registered resources, making
 * it possible to create resource bundles for 3rd party libraries. When a single resource from a
 * resource bundle is requested, the bundle is rendered instead. All other resources from the bundle
 * are marked as rendered. A specific resource can only be part of one bundle.
 * 
 * @author papegaaij
 */
public class ResourceBundles
{
	private final ResourceReferenceRegistry registry;

	private final Map providedResourcesToBundles;

	/**
	 * Construct.
	 * 
	 * @param registry
	 *      the registry that keeps all referenced resources
	 */
	public ResourceBundles(final ResourceReferenceRegistry registry)
	{
		this.registry = Args.notNull(registry, "registry");
		this.providedResourcesToBundles = new HashMap();
	}

	/**
	 * Adds a javascript bundle that is automatically generated by concatenating the given package
	 * resources. If the given resources depend on each other, you should make sure that the
	 * resources are provided in the order they need to be concatenated. If the resources depend on
	 * other resources, that are not part of the bundle, the bundle will inherit these dependencies.
	 * 
	 * This method is equivalent to {@link #addBundle(HeaderItem)} with a
	 * {@link JavaScriptHeaderItem} for a {@link ConcatResourceBundleReference}.
	 * 
	 * @param scope
	 *            The {@linkplain ResourceReference#getScope() scope} of the bundle
	 * @param name
	 *            The name of the resource. This will show up as the filename in the markup.
	 * @param references
	 *            The resources this bundle will consist of.
	 * @return the newly created bundle
	 */
	public JavaScriptReferenceHeaderItem addJavaScriptBundle(Class scope, String name,
		JavaScriptResourceReference... references)
	{
		return addJavaScriptBundle(scope, name, false, references);
	}

	/**
	 * Adds a javascript bundle that is automatically generated by concatenating the given package
	 * resources. If the given resources depend on each other, you should make sure that the
	 * resources are provided in the order they need to be concatenated. If the resources depend on
	 * other resources, that are not part of the bundle, the bundle will inherit these dependencies.
	 *
	 * This method is equivalent to {@link #addBundle(HeaderItem)} with a
	 * {@link JavaScriptHeaderItem} for a {@link ConcatResourceBundleReference}.
	 *
	 * @param scope
	 *            The {@linkplain ResourceReference#getScope() scope} of the bundle
	 * @param defer
	 *            specifies that the execution of a script should be deferred (delayed) until after
	 *            the page has been loaded.
	 * @param name
	 *            The name of the resource. This will show up as the filename in the markup.
	 * @param references
	 *            The resources this bundle will consist of.
	 * @return the newly created bundle
	 */
	public JavaScriptReferenceHeaderItem addJavaScriptBundle(Class scope, String name, boolean defer,
		JavaScriptResourceReference... references)
	{
		List items = new ArrayList<>();

		for (JavaScriptResourceReference curReference : references)
		{
			items.add(JavaScriptHeaderItem.forReference(curReference));
		}

		ConcatResourceBundleReference bundleReference =
				newBundleResourceReference(scope, name, items);

		if (Application.exists())
		{
			IJavaScriptCompressor javaScriptCompressor = Application.get().getResourceSettings().getJavaScriptCompressor();
			bundleReference.setCompressor(javaScriptCompressor);
		}

		JavaScriptReferenceHeaderItem item = JavaScriptHeaderItem.forReference(bundleReference);
		item.setDefer(defer);
		return addBundle(item);
	}

	/**
	 * Adds a css bundle that is automatically generated by concatenating the given package
	 * resources. If the given resources depend on each other, you should make sure that the
	 * resources are provided in the order they need to be concatenated. If the resources depend on
	 * other resources, that are not part of the bundle, the bundle will inherit these dependencies.
	 * 
	 * This method is equivalent to {@link #addBundle(HeaderItem)} with a {@link CssHeaderItem} for
	 * a {@link ConcatResourceBundleReference}.
	 * 
	 * @param scope
	 *            The {@linkplain ResourceReference#getScope() scope} of the bundle
	 * @param name
	 *            The name of the resource. This will show up as the filename in the markup.
	 * @param references
	 *            The resources this bundle will consist of.
	 * @return the newly created bundle
	 */
	public CssReferenceHeaderItem addCssBundle(Class scope, String name,
		CssResourceReference... references)
	{
		List items = new ArrayList();
		for (CssResourceReference curReference : references)
		{
			items.add(CssHeaderItem.forReference(curReference));
		}
		ConcatResourceBundleReference bundleReference =
				newBundleResourceReference(scope, name, items);
		if (Application.exists())
		{
			ICssCompressor cssCompressor = Application.get().getResourceSettings().getCssCompressor();
			bundleReference.setCompressor(cssCompressor);
		}
		return addBundle(CssHeaderItem.forReference(bundleReference));
	}

	/**
	 * Creates a ResourceReference that will point to the bundle with the items
	 *
	 * @param scope
	 *            The {@linkplain ResourceReference#getScope() scope} of the bundle
	 * @param name
	 *            The name of the resource. This will show up as the filename in the markup.
	 * @param items
	 *            The HeaderItems for the resource references for the bundle
	 * @param 
	 *            The type of the header items
	 * @return A ResourceReference that will point to the bundle with the items
	 */
	protected  ConcatResourceBundleReference newBundleResourceReference(Class scope, String name, List items)
	{
		return new ConcatResourceBundleReference(scope, name, items);
	}

	/**
	 * Adds a bundle to the registry.
	 * 
	 * @param bundle
	 *            The bundle to register
	 * @return the bundle
	 * @throws IllegalArgumentException
	 *             if any of the provided resources of the given bundle is already provided by a
	 *             different bundle.
	 */
	public  T addBundle(T bundle)
	{
		for (HeaderItem curProvidedResource : bundle.getProvidedResources())
		{
			if (providedResourcesToBundles.containsKey(curProvidedResource))
			{
				throw new IllegalArgumentException(
					"Only one bundle can provide a certain resource. " +
						providedResourcesToBundles.get(curProvidedResource) +
						" already provides the resource " + curProvidedResource);
			}
			providedResourcesToBundles.put(curProvidedResource, bundle);
		}
		if (bundle instanceof IReferenceHeaderItem)
		{
			ResourceReference reference = ((IReferenceHeaderItem) bundle).getReference();
			if (reference.canBeRegistered())
			{
				registry.registerResourceReference(reference);
			}
		}
		return bundle;
	}

	/**
	 * Finds a bundle that provides the given item.
	 * 
	 * @param item
	 *            The item that should be provided by the bundle.
	 * @return The bundle that provides the given item or null if no bundle is found.
	 */
	public HeaderItem findBundle(HeaderItem item)
	{
		return providedResourcesToBundles.get(item);
	}
}