/* 
 * Copyright (c) 2008 Stiftung Deutsches Elektronen-Synchrotron, 
 * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY.
 *
 * THIS SOFTWARE IS PROVIDED UNDER THIS LICENSE ON AN "../AS IS" BASIS. 
 * WITHOUT WARRANTY OF ANY KIND, EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED 
 * TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR PARTICULAR PURPOSE AND 
 * NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE 
 * FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR 
 * THE USE OR OTHER DEALINGS IN THE SOFTWARE. SHOULD THE SOFTWARE PROVE DEFECTIVE 
 * IN ANY RESPECT, THE USER ASSUMES THE COST OF ANY NECESSARY SERVICING, REPAIR OR 
 * CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE. 
 * NO USE OF ANY SOFTWARE IS AUTHORIZED HEREUNDER EXCEPT UNDER THIS DISCLAIMER.
 * DESY HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, 
 * OR MODIFICATIONS.
 * THE FULL LICENSE SPECIFYING FOR THE SOFTWARE THE REDISTRIBUTION, MODIFICATION, 
 * USAGE AND OTHER RIGHTS AND OBLIGATIONS IS INCLUDED WITH THE DISTRIBUTION OF THIS 
 * PROJECT IN THE FILE LICENSE.HTML. IF THE LICENSE IS NOT INCLUDED YOU MAY FIND A COPY 
 * AT HTTP://WWW.DESY.DE/LEGAL/LICENSE.HTM
 */
package org.csstudio.platform.simpledal;


import org.csstudio.dal.CssApplicationContext;
import org.csstudio.platform.internal.simpledal.ConnectorFactory;
import org.csstudio.platform.internal.simpledal.ProcessVariableConnectionService;
import org.csstudio.dal.simple.SimpleDALBroker;

/**
 * Factory of
 * {@link IProcessVariableConnectionService ProcessVariableConnectionService}s,
 * 
 * @author C1 WPS / KM, MZ, Xihui Chen
 */
public class ProcessVariableConnectionServiceFactory {

	private static ProcessVariableConnectionServiceFactory sharedInstance;

	private IProcessVariableConnectionService _mainProcessVariableConnectionService;

	private SimpleDALBroker broker;

	/**
	 * Returns the singleton instance of this factory.
	 * 
	 * @return the singleton instance of this factory
	 */
	public static synchronized ProcessVariableConnectionServiceFactory getDefault() {	
	
		if (ProcessVariableConnectionServiceFactory.sharedInstance == null) {		
			ProcessVariableConnectionServiceFactory.sharedInstance = new ProcessVariableConnectionServiceFactory();
		}
		return ProcessVariableConnectionServiceFactory.sharedInstance;
	}

	/**
	 * Returns the main {@link IProcessVariableConnectionService} for the
	 * control system studio.
	 * 
	 * In general, this service should be used by all CSS applications to save
	 * resources and ensure maximum channel reuse.
	 * 
	 * @return the main {@link IProcessVariableConnectionService} for the
	 *         control system studio
	 */
	public IProcessVariableConnectionService getProcessVariableConnectionService() {
		return getMainProcessVariableConnectionService();
	}

	/**
	 * Returns a named {@link IProcessVariableConnectionService}. If no service
	 * exists for the specified name, a new service is created.
	 * 
	 * @return a {@link IProcessVariableConnectionService}
	 */
	public IProcessVariableConnectionService createProcessVariableConnectionService() {
		// TODO: Implement storage for named services and enhance the Connector
		// Overview View to display channels for different connection services
		return getMainProcessVariableConnectionService();
	}
	

	/**
	 * Returns the {@link SimpleDALBroker} which is a narrow interface to the DAL layer.
	 * @return the {@link SimpleDALBroker}
	 */
	// FIXME: 15.03.2010: swende: Eventuell n Broker-Instanzen betreiben - pro Display eine!
	public SimpleDALBroker getSimpleDALBroker() {
		if (broker == null) {
			broker = SimpleDALBroker.newInstance(new CssApplicationContext("CSS"));
		}
		return broker;
	}

	private synchronized IProcessVariableConnectionService getMainProcessVariableConnectionService() {
			if (_mainProcessVariableConnectionService == null) {
				_mainProcessVariableConnectionService = new ProcessVariableConnectionService(new ConnectorFactory());
			}
		return _mainProcessVariableConnectionService;
	}

	
}