/*******************************************************************************
 * Copyright (c) 2010, 2011 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.server.core.internal;

import java.io.File;
import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.eclipse.core.runtime.preferences.IEclipsePreferences;
import org.eclipse.core.runtime.preferences.InstanceScope;
import org.eclipse.core.runtime.preferences.PreferenceModifyListener;
import org.osgi.service.prefs.Preferences;
import org.w3c.dom.*;
import org.xml.sax.InputSource;

public class ServerPreferenceModifyListener extends PreferenceModifyListener {

	private static final String LOCKED_ATTRIBUTE_NAME = "locked"; //$NON-NLS-1$
	private static final String RUNTIMES_PREFERENCE_NAME = "runtimes"; //$NON-NLS-1$
	private static final String RUNTIME_NODE_NAME = "runtime"; //$NON-NLS-1$
	
	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.preferences.PreferenceModifyListener#preApply(org.eclipse.core.runtime.preferences.IEclipsePreferences)
	 */
	public IEclipsePreferences preApply(IEclipsePreferences node) {
		Preferences instance = node.node(InstanceScope.SCOPE);
		Preferences runtimes = instance.node(ServerPlugin.PLUGIN_ID);
		if (runtimes != null)
			removeLockedServerRuntimePreference(runtimes); //$NON-NLS-1$
		return super.preApply(node);
	}

	private void removeLockedServerRuntimePreference(Preferences preferences) {
		try {
			File prefFile = new File(preferences.get(RUNTIMES_PREFERENCE_NAME, ""));
			if (!prefFile.exists()){
				return; 
			}
			
			Document doc = DocumentBuilderFactory.newInstance()
					.newDocumentBuilder().parse(new InputSource(new StringReader(prefFile.toString()))); //$NON-NLS-1$
			NodeList nodeList = doc.getElementsByTagName(RUNTIME_NODE_NAME);
			for (int s = 0; s < nodeList.getLength(); s++) {
				Node node = nodeList.item(s);
				if (node.getNodeType() == Node.ELEMENT_NODE) {
					NamedNodeMap attributes = node.getAttributes();
					Node locked = attributes.getNamedItem(LOCKED_ATTRIBUTE_NAME);
					if (locked != null && Boolean.parseBoolean(locked.getNodeValue()))
						node.getParentNode().removeChild(node);
				}
			}
			StringWriter runtimes = new StringWriter();
            TransformerFactory.newInstance().newTransformer().transform(new DOMSource(doc), new StreamResult(runtimes));        
            preferences.remove(RUNTIMES_PREFERENCE_NAME);
            preferences.put(RUNTIMES_PREFERENCE_NAME, runtimes.toString());
		  } catch (Exception e) {
		    //there is no defined runtime environment 
			  return;
		  }
		  
	}

}