/**
 * AmbientTalk/2 Project
 * NATSeconds.java created on Apr 14, 2008
 * (c) Programming Technology Lab, 2006 - 2007
 * Authors: Tom Van Cutsem & Stijn Mostinckx
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. 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.
 */
package edu.vub.at.signals.natives;

import java.util.Timer;
import java.util.TimerTask;

import edu.vub.at.exceptions.InterpreterException;
import edu.vub.at.objects.ATNumber;
import edu.vub.at.objects.grammar.ATSymbol;
import edu.vub.at.objects.natives.NATByRef;
import edu.vub.at.objects.natives.NATMethodInvocation;
import edu.vub.at.objects.natives.NATNumber;
import edu.vub.at.objects.natives.NATTable;
import edu.vub.at.objects.natives.NATText;
import edu.vub.at.objects.natives.grammar.AGSymbol;

/**
 * Seconds is the builtin behavior representing the number of seconds that have elapsed since the
 * AmbientTalk virtual machine has been started.
 *  
 * @author smostinc
 */
public class NATSeconds extends NATBehavior {

	private static final ATSymbol _TICK_ = AGSymbol.jAlloc("tick");
	private static final TimerSource _TIMER_ = new TimerSource();
	
	private static final ThreadLocal _SECONDS_ = new ThreadLocal() {
		protected Object initialValue() {
			try {
				return new NATSeconds(_TIMER_, new SecondsConsumer());
			} catch (InterpreterException e) {
				throw new RuntimeException(e);
			}
		};
	};
	
	public static NATSeconds instance() {
		return (NATSeconds) _SECONDS_.get();
	}
	
	/**
	 * TimerSource is a natively implemented event source which generates time tick events.
	 * The Event Source is shared between all actors on a single virtual machine, yet all
	 * actors have a separate seconds object, to represent the time. Due to synchronization
	 * when propagating events, the timer cannot cause concurrency within a single actor.
	 * 
	 * @author smostinc
	 */
	private static class TimerSource extends NATEventSource {
		
		private Timer 	timer_;

		public TimerSource() {
			super(0);
			
						timer_	= new Timer();
			TimerTask	task_	= new TimerTask() {
				public void run() {
					try {
						propagateNewMessage(new NATMethodInvocation(
								_TICK_,
								NATTable.EMPTY,
								NATTable.EMPTY));
					} catch (InterpreterException e) {
						// Failed to construct a <-tick() message
						e.printStackTrace();
					}
				};
			};
				
			timer_.schedule(task_, 1000, 1000);
		}
	}
		
	/**
	 * <code>
	 * def SecondsConsumer := object: {
	 *   def seconds := 0;
	 *   def tick() {
	 *     seconds := seconds.inc();
	 *   }
	 * }  
	 * </code>  
	 */
	public static class SecondsConsumer extends NATByRef {
		ATNumber seconds_ = NATNumber.ZERO;
				
		public ATNumber base_tick() throws InterpreterException {
			seconds_ = seconds_.base_inc();
			return seconds_;
		}
		
		public NATText meta_print() throws InterpreterException {
			return NATText.atValue("<object:"+this.hashCode()+">");
		}
	}
	
	NATSeconds(TimerSource theTimer, SecondsConsumer theConsumer) throws InterpreterException {
		super(theTimer, NATNumber.ZERO, theConsumer);
	}
}