/*******************************************************************************
 * Copyright (c) 2000, 2010 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.gef.ui.palette.customize;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Iterator;
import java.util.List;

import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.viewers.Viewer;

import org.eclipse.gef.palette.PaletteContainer;
import org.eclipse.gef.palette.PaletteEntry;
import org.eclipse.gef.palette.PaletteRoot;

/**
 * This is the {@link org.eclipse.jface.viewers.IContentProvider} for the
 * {@link org.eclipse.jface.viewers.TreeViewer} used in
 * {@link org.eclipse.gef.ui.palette.customize.PaletteCustomizerDialog}.
 * 
 * @author Pratik Shah
 * @see org.eclipse.jface.viewer.TreeViewer
 * @see org.eclipse.gef.ui.palette.customize.PaletteCustomizerDialog
 */
class PaletteTreeProvider implements ITreeContentProvider {

	private TreeViewer viewer;
	private PaletteRoot root;
	private PropertyChangeListener modelListener = new PropertyChangeListener() {
		public void propertyChange(PropertyChangeEvent evt) {
			handlePropertyChanged(evt);
		}
	};

	/**
	 * Constructor
	 * 
	 * @param treeviewer
	 *            The TreeViewer whose ContentProvider this PaletteTreeProvider
	 *            is
	 */
	public PaletteTreeProvider(TreeViewer treeviewer) {
		this.viewer = treeviewer;
	}

	/**
	 * Stops listening to the model
	 * 
	 * @see org.eclipse.jface.viewers.IContentProvider#dispose()
	 */
	public void dispose() {
		traverseModel(root, false);
	}

	/**
	 * If the given element does not have any children, this method should
	 * return <code>null</code>. This fixes the problem where a "+" sign is
	 * incorrectly placed next to an empty container in the tree.
	 * 
	 * @see org.eclipse.jface.viewers.ITreeContentProvider#getChildren(Object)
	 */
	public Object[] getChildren(Object parentElement) {
		if (parentElement instanceof PaletteContainer) {
			List children = ((PaletteContainer) parentElement).getChildren();
			if (!children.isEmpty()) {
				return children.toArray();
			}
		}
		return null;
	}

	/**
	 * @see org.eclipse.jface.viewers.ITreeContentProvider#hasChildren(Object)
	 */
	public boolean hasChildren(Object element) {
		return getChildren(element) != null;
	}

	/**
	 * This method should not return <code>null</code>.
	 * 
	 * @see org.eclipse.jface.viewers.IStructuredContentProvider#getElements(Object)
	 */
	public Object[] getElements(Object inputElement) {
		Object[] elements = getChildren(inputElement);
		if (elements == null) {
			elements = new Object[0];
		}
		return elements;
	}

	/**
	 * @see org.eclipse.jface.viewers.ITreeContentProvider#getParent(Object)
	 */
	public Object getParent(Object element) {
		return ((PaletteEntry) element).getParent();
	}

	/**
	 * This method is invoked whenever there is any change in the model. It
	 * updates the viewer with the changes that were made to the model.
	 * Sub-classes may override this method to change or extend its
	 * functionality.
	 * 
	 * @param evt
	 *            The {@link PropertyChangeEvent} that was fired from the model
	 */
	protected void handlePropertyChanged(PropertyChangeEvent evt) {
		PaletteEntry entry = ((PaletteEntry) evt.getSource());
		String property = evt.getPropertyName();
		if (property.equals(PaletteEntry.PROPERTY_LABEL)
				|| property.equals(PaletteEntry.PROPERTY_SMALL_ICON)) {
			viewer.update(entry, null);
		} else if (property.equals(PaletteEntry.PROPERTY_VISIBLE)) {
			viewer.refresh(entry);
		} else if (property.equals(PaletteContainer.PROPERTY_CHILDREN)) {
			viewer.refresh(entry);
			List oldChildren = (List) evt.getOldValue();
			for (Iterator iter = oldChildren.iterator(); iter.hasNext();) {
				PaletteEntry child = (PaletteEntry) iter.next();
				traverseModel(child, false);
			}
			traverseModel(entry, true);
		}
	}

	/**
	 * @see org.eclipse.jface.viewers.IContentProvider#inputChanged(Viewer,
	 *      Object, Object)
	 */
	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
		if (root != null)
			traverseModel(root, false);
		if (newInput != null) {
			root = (PaletteRoot) newInput;
			traverseModel(root, true);
		}
	}

	private void traverseModel(PaletteEntry entry, boolean isHook) {
		if (isHook) {
			entry.addPropertyChangeListener(modelListener);
		} else {
			entry.removePropertyChangeListener(modelListener);
		}

		if (hasChildren(entry)) {
			Object[] children = getChildren(entry);
			for (int i = 0; i < children.length; i++) {
				traverseModel((PaletteEntry) children[i], isHook);
			}
		}
	}

}