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/*
 * Copyright © 1996-2009 GlobalMentor, Inc. 
 *
 * Licensed 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 com.globalmentor.swing.text;

import java.util.List;
import javax.swing.text.Element;
import javax.swing.text.View;
import javax.swing.text.ViewFactory;

import com.globalmentor.java.Objects;

/**
 * A default implementation of a view factory that allows a fallback view factory to be invoked if this view factory doesn't know how to create a particular
 * view.
 * 
 * As this class implements {@link ViewsFactory}, which allows multiple views to be created, one should usually override {@link #create(Element, boolean)} and
 * use the default implementation of the other methods.
 * 
 * @author Garret Wilson
 */
public abstract class DefaultViewFactory implements ViewsFactory //TODO maybe use this as a basis for XMLViewFactory
{

	/**
	 * The view factory to use as a fallback in case this view factory cannot create a view for the given element.
	 */
	private final ViewFactory fallbackViewFactory;

	/**
	 * @return The view factory to use as a fallback in case this view factory cannot create a view for the given element.
	 */
	protected ViewFactory getFallbackViewFactory() {
		return fallbackViewFactory;
	}

	/** Creates a view factory with no fallback view factory. */
	public DefaultViewFactory() {
		this(null); //create a view factory with no default
	}

	/**
	 * Creates a view factory with a fallback view factory.
	 * @param fallback The view factory to be used as a fallback if this view factory cannnot create a view.
	 */
	public DefaultViewFactory(final ViewFactory fallback) {
		fallbackViewFactory = fallback; //save the fallback view factory
	}

	/**
	 * Creates a view for the given element..
	 * @param element The element this view will represent.
	 * @return A view to represent the given element.
	 */
	public View create(final Element element) {
		return create(element, false); //return a single view to represent the given view, giving no indication if multiple views are needed
	}

	/**
	 * Creates one or more views for the given element, storing the views in the given list. This method allows one element (such as a nested inline element
	 * within a paragraph) to be represented by one level of multiple views rather than a hierarchy of views.
	 * @param element The element the view or views will represent.
	 * @param addViewList The list of views to which the views should be added.
	 */
	public void create(final Element element, final List addViewList) {
		final View view = create(element, true); //create a view for the element, if we can, but get an indication of if there should be several views
		if(view != null) { //if there is only one view
			addViewList.add(view); //add the list to the view, mimicking the normal functionality
		} else { //if there should be multiple views
			int childElementCount = element.getElementCount(); //see how many child elements there are
			for(int i = 0; i < childElementCount; ++i)
				//look at each child element
				create(element.getElement(i), addViewList); //create one or more views for this child element
		}
	}

	/**
	 * Creates a view for the given element. If the element specifies a namespace and a view factory has been registered for the given namespace, the view
	 * creation will be delegated to the designated view factory. As this class implements ViewsFactory, which allows multiple views to be created,
	 * this method can optionally indicate multiple views are needed by returning null.
	 * 
	 * The default implementation of this class attempts to call the corresponding method in the fallback view factory if the fallback view factory is a
	 * ViewFactory. If not, the fallback view's normal create() method is called. If there is no fallback view factory, an illegal
	 * argument exception is thrown.
	 * 
	 * @param element The element this view will represent.
	 * @param indicateMultipleViews Whether null should be returned to indicate multiple views should represent the given element.
	 * @return A view to represent the given element, or null indicating the element should be represented by multiple views.
	 * @throws IllegalArgumentException Thrown if the element is not recognized and there is no fallback view factory.
	 * @see com.globalmentor.swing.text.ViewsFactory
	 */
	public View create(final Element element, final boolean indicateMultipleViews) {
		final ViewFactory fallbackViewFactory = getFallbackViewFactory(); //get the fallback view factory
		if(fallbackViewFactory != null) { //if we have a fallback view factory
			if(fallbackViewFactory instanceof ViewsFactory) //if the fallback view factory knows how to create multiple views
				return ((ViewsFactory)fallbackViewFactory).create(element, indicateMultipleViews); //allow the fallback view factory to indicate it needs to create multiple views, if it wishes
			else
				//if the fallback view factory is a normal view factory
				return getFallbackViewFactory().create(element); //let the fallback view factory create the view normally
		} else
			//if we have no fallback view factory
			throw new IllegalArgumentException(Objects.toString(element)); //show that we don't know what to do with the element
			//TODO del			return new XMLInlineView(element);	//everything we don't know what to do with gets to be an inline view TODO should this be the default?
	}

}