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/*
 Modified by Yan Huang 

 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.factcenter.fastgc.YaoGC;

import java.util.ArrayList;
import java.util.List;
import java.util.Observer;

/**
 * Observable is used to notify a group of Observer objects when a change
 * occurs. On creation, the set of observers is empty. After a change occurred,
 * the application can call the {@link #notifyObservers()} method. This will
 * cause the invocation of the {@code update()} method of all registered
 * Observers. The order of invocation is not specified. This implementation will
 * call the Observers in the order they registered. Subclasses are completely
 * free in what order they call the update methods.
 *
 * @see Observer
 */
public class TransitiveObservable {

	List observers = new ArrayList();

	boolean changed = false;


    /**
     * The serial number of the latest execution to have changed this observable.
     *
     * This lets us do sanity checking to see where inputs have percolated to.
     */
    int execSerial = 0;


    public int getExecSerial() {
        return execSerial;
    }

	List exports = new ArrayList();
	public static class Socket {
		Wire[] wires;
		int    idx;

		public Socket(Wire[] ws, int i) {
			wires = ws;
			idx = i;
		}

		public void updateSocket(Wire w) {
			wires[idx] = w;
		}

		public boolean equals(Socket sock) {
			if (this == sock)
				return true;

			if (sock != null) {
				return (wires == sock.wires) && (idx == sock.idx);
			}

			return false;
		}
	}

	/**
	 * Constructs a new {@code Observable} object.
	 */
	public TransitiveObservable() {
		super();
	}

	/**
	 * Adds the specified observer to the list of observers. If it is already
	 * registered, it is not added a second time.
	 * 
	 * @param observer
	 *            the Observer to add.
	 */
	public void addObserver(TransitiveObserver observer, Socket sock) {
		if (observer == null) {
			throw new NullPointerException();
		}
		synchronized (this) {
			// if (!observers.contains(observer))
			observers.add(observer);
			exports.add(sock);
		}
	}

	/**
	 * Clears the changed flag for this {@code Observable}. After calling
	 * {@code clearChanged()}, {@code hasChanged()} will return {@code false}.
	 */
	protected void clearChanged() {
		changed = false;
	}

	/**
	 * Returns the number of observers registered to this {@code Observable}.
	 * 
	 * @return the number of observers.
	 */
	public int countObservers() {
		return observers.size();
	}

	/**
	 * Removes the specified observer from the list of observers. Passing null
	 * won't do anything.
	 * 
	 * @param observer
	 *            the observer to remove.
	 */
	public synchronized void deleteObserver(TransitiveObserver observer, Socket sock) {
		observers.remove(observer);
		exports.remove(sock);
	}

	/**
	 * Removes all observers from the list of observers.
	 */
	public synchronized void deleteObservers() {
		observers.clear();
		exports.clear();
	}

	/**
	 * Returns the changed flag for this {@code Observable}.
	 * 
	 * @return {@code true} when the changed flag for this {@code Observable} is
	 *         set, {@code false} otherwise.
	 */
	public boolean hasChanged() {
		return changed;
	}

	/**
	 * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
	 * method for every observer in the list of observers using null as the
	 * argument. Afterwards, calls {@code clearChanged()}.
	 * 
	 * Equivalent to calling {@code notifyObservers(null)}.
	 */
	public void notifyObservers() {
		notifyObservers(null);
	}

	/**
	 * If {@code hasChanged()} returns {@code true}, calls the {@code update()}
	 * method for every Observer in the list of observers using the specified
	 * argument. Afterwards calls {@code clearChanged()}.
	 * 
	 * @param data
	 *            the argument passed to {@code update()}.
	 */
	public void notifyObservers(Object data) {
		int size = 0;
		TransitiveObserver[] arrays = null;
		synchronized (this) {
			if (hasChanged()) {
				clearChanged();
				size = observers.size();
				arrays = new TransitiveObserver[size];
				observers.toArray(arrays);
			}
		}
		if (arrays != null) {
			for (TransitiveObserver observer : arrays) {
				observer.update(this, data);
			}
		}
	}

	/**
	 * Sets the changed flag for this {@code Observable}. After calling
	 * {@code setChanged()}, {@code hasChanged()} will return {@code true}.
	 */
	protected void setChanged(int execSerial) {
		changed = true;
        this.execSerial = execSerial;
	}
}