/**
 * AmbientTalk/2 Project
 * EncapsulatingReactiveComputation.java created on Jun 10, 2008 at 8:48:38 PM
 * (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.eval;

import java.util.HashSet;
import java.util.Iterator;

import edu.vub.at.signals.SignalListener;

/**
 * When creating a dependency network inside the body of a method, this network may depend implicitly
 * on other reactive computations, for instance if the method was called with another behavior as the
 * receiver or as an argument of that method.  EncapsulatingSignal instances are managed in a dynamic
 * variable by the interpreter to keep track of these implicit dependencies.
 * 
 * Hence, when the method is triggered due to changes in an argument or the receiver,  the dependency
 * network that was constructed in the previous invocation is automatically dismantled.
 * 
 * @author smostinc
 */
public class EncapsulatingSignal {

	private HashSet nestedSignalListeners_ = new HashSet();
	private int dependencyHeight_;
	
	public EncapsulatingSignal(int dependencyHeight) {
		dependencyHeight_ = dependencyHeight;
	}
	
	/**
	 * When dependent computations are created within the control flow of this encapsulating
	 * signal,  their minimal dependency height should be greater than the dependency height
	 * of the encapsulating signal.
	 */
	public int dependencyHeight() {
		return dependencyHeight_;
	}
	
	/**
	 * When the encapsulating reactive computation needs to be performed anew, all dependent
	 * computations that were constructed within its dynamic extent need need to be unhooked.
	 */
	public synchronized void unhookAllDependencies() {
		for (Iterator nestedSignalIt = nestedSignalListeners_.iterator(); nestedSignalIt.hasNext();) {
			SignalListener currentSignalListener = (SignalListener) nestedSignalIt.next();
			
			currentSignalListener.unhook();
			nestedSignalIt.remove();
		}
	}
	
	
	public synchronized void registerDependency(SignalListener theNestedListener) {
		nestedSignalListeners_.add(theNestedListener);
	}
}