/*******************************************************************************
 * Copyright (c) 2008 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.wst.xml.ui.internal.handlers;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.ui.IEditorPart;
import org.eclipse.ui.handlers.HandlerUtil;
import org.eclipse.ui.texteditor.ITextEditor;
import org.w3c.dom.Attr;
import org.w3c.dom.Node;

/**
 * Provides navigation to next/previous DOM sibling Nodes
 */
abstract public class AbstractSiblingNavigationHandler extends AbstractHandler {

	public Object execute(ExecutionEvent event) throws ExecutionException {
		IEditorPart editor = HandlerUtil.getActiveEditor(event);
		ITextEditor textEditor = null;
		if (editor instanceof ITextEditor)
			textEditor = (ITextEditor) editor;
		else {
			Object o = editor.getAdapter(ITextEditor.class);
			if (o != null)
				textEditor = (ITextEditor) o;
		}
		if (textEditor != null) {

			ISelection selection = textEditor.getSelectionProvider().getSelection();
			if (!selection.isEmpty() && selection instanceof IStructuredSelection) {
				Object o = ((IStructuredSelection) selection).getFirstElement();
				if (o instanceof Node) {
					Node sibling = null;

					if (((Node) o).getNodeType() == Node.ATTRIBUTE_NODE) {
						o = ((Attr) o).getOwnerElement();
					}
					if (moveForward()) {
						sibling = ((Node) o).getNextSibling();
						while (sibling != null && sibling.getNodeType() == Node.TEXT_NODE && sibling.getNodeValue().trim().length() == 0) {
							sibling = sibling.getNextSibling();
						}
						if (sibling == null) {
							sibling = ((Node) o).getParentNode().getFirstChild();
							while (sibling != null && sibling.getNodeType() == Node.TEXT_NODE && sibling.getNodeValue().trim().length() == 0) {
								sibling = sibling.getNextSibling();
							}
						}
					}
					else {
						sibling = ((Node) o).getPreviousSibling();
						while (sibling != null && sibling.getNodeType() == Node.TEXT_NODE && sibling.getNodeValue().trim().length() == 0) {
							sibling = sibling.getPreviousSibling();
						}
						if (sibling == null) {
							sibling = ((Node) o).getParentNode().getLastChild();
							while (sibling != null && sibling.getNodeType() == Node.TEXT_NODE && sibling.getNodeValue().trim().length() == 0) {
								sibling = sibling.getPreviousSibling();
							}
						}
					}

					// The only child is a Text Node, go to the parent Node
					if (((Node) o).getNodeType() == Node.TEXT_NODE && o.equals(sibling)) {
						sibling = ((Node) o).getParentNode();
					}


					if (sibling != null) {
						textEditor.getSelectionProvider().setSelection(new StructuredSelection(sibling));
					}
				}
			}
		}
		return null;
	}

	abstract protected boolean moveForward();
}