/*******************************************************************************
 * Copyright (c) 2004, 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.sse.core;

import org.eclipse.core.runtime.Platform;
import org.eclipse.wst.sse.core.internal.SSECorePlugin;
import org.eclipse.wst.sse.core.internal.model.ModelManagerImpl;
import org.eclipse.wst.sse.core.internal.provisional.IModelManager;
import org.osgi.framework.Bundle;

/**
 * Class to allow access to properly configured implementors of IModelManager.
 * 
 * @since  1.5  org.eclipse.wst.sse.core
 */
final public class StructuredModelManager {
	/**
	 * Do not allow instances to be created.
	 */
	private StructuredModelManager() {
		super();
	}

	/**
	 * Provides access to the instance of IModelManager. Returns null if model
	 * manager can not be created or is not valid (such as, when workbench is
	 * shutting down).
	 * 
	 * @return IModelManager - returns the one model manager for structured
	 *         models or null if the owning bundle is neither active nor
	 *         starting.
	 */
	public static IModelManager getModelManager() {
		boolean isReady = false;
		IModelManager modelManager = null;
		boolean interrupted = false;
		try {
			while (!isReady) {
				Bundle localBundle = Platform.getBundle(SSECorePlugin.ID);
				int state = localBundle.getState();
				if (state == Bundle.ACTIVE) {
					isReady = true;
					// getInstance is a synchronized static method.
					modelManager = ModelManagerImpl.getInstance();
				}
				else if (state == Bundle.STARTING) {
					try {
						Thread.sleep(100);
					}
					catch (InterruptedException e) {
						// ignore, just loop again
						interrupted = true;
					}
				}
				else if (state == Bundle.STOPPING || state == Bundle.UNINSTALLED) {
					isReady = true;
					modelManager = null;
				}
				else {
					// not sure about other states, 'resolved', 'installed'
					isReady = true;
					modelManager = null;
				}
			}
		}
		finally {
			if (interrupted) {
				Thread.currentThread().interrupt();
			}
		}
		return modelManager;
	}
}