/* 
 * Copyright (c) 2006 Stiftung Deutsches Elektronen-Synchroton, 
 * 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.internal.simpledal.local;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.csstudio.platform.ExecutionService;
import org.csstudio.platform.model.pvs.IProcessVariableAddress;

/**
 * Represents a local channel.
 * 
 * @author Sven Wende
 * 
 * @version $Revision$
 */
public final class LocalChannel {
	private ScheduledFuture _scheduledFuture;

	private AbstractDataGenerator _dataGenerator;

	/**
	 * The current value.
	 */
	private Object _currentValue;

	private List<ILocalChannelListener> _listeners;

	public LocalChannel(IProcessVariableAddress pv) {
		assert pv != null;
		_currentValue = null;
		_listeners = new ArrayList<ILocalChannelListener>();

		// find data generator using regular expressions
		boolean found = false;
		for (DataGeneratorInfos dgInfo : DataGeneratorInfos.values()) {
			if (!found) {
				Pattern p = dgInfo.getPattern();
				Matcher m = p.matcher(pv.getProperty());

				if (m.find()) {
					found = true; // we apply only the first data generator
					// that fits

					// get the options that are encoded in the name of the
					// process variable
					final String[] options = new String[m.groupCount()];

					for (int i = 0; i < m.groupCount(); i++) {
						options[i] = m.group(i+1);
					}

					// create and init the generator
					_dataGenerator = dgInfo.getDataGeneratorFactory()
							.createGenerator(this, 1000, options);

					// init the current value
					_currentValue = _dataGenerator.generateNextValue();

					schedule();
				}
			}
		}
	}

	public Object getValue() {
		return _currentValue;
	}

	public void setValue(Object value) {
		_currentValue = value;
		fireValueChangeEvent();
	}

	public void addListener(ILocalChannelListener listener) {
		if (!_listeners.contains(listener)) {
			_listeners.add(listener);
			schedule();
		}
	}

	public void removeListener(ILocalChannelListener listener) {
		boolean removed = _listeners.remove(listener);
		if (removed) {
			schedule();
		}
	}

	private void fireValueChangeEvent() {
		for (ILocalChannelListener listener : _listeners) {
			listener.valueChanged(_currentValue);
		}
	}

	private void schedule() {
		// we need a data generator
		if (_dataGenerator != null) {
			// if nobody listens, we do not need to generate any random data
			if (_listeners.size() == 0) {
				// we cancel all scheduled jobs
				if (_scheduledFuture != null) {
					_scheduledFuture.cancel(false);
					_scheduledFuture = null;
				}
			} else {
				// we schedule the job if necessary
				if (_scheduledFuture == null) {
					_scheduledFuture = ExecutionService.getInstance()
							.getScheduledExecutorService().scheduleAtFixedRate(
									_dataGenerator, 1000,
									_dataGenerator.getPeriod(),
									TimeUnit.MILLISECONDS);
				}
			}
		}
	}

}