/**

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

  *

  * Copyright 2013-2014 Oracle and/or its affiliates. All rights reserved.

  *

  * Oracle and Java are registered trademarks of Oracle and/or its affiliates.

  * Other names may be trademarks of their respective owners.

  *

  * The contents of this file are subject to the terms of either the GNU

  * General Public License Version 2 only ("GPL") or the Common

  * Development and Distribution License("CDDL") (collectively, the

  * "License"). You may not use this file except in compliance with the

  * License. You can obtain a copy of the License at

  * http://www.netbeans.org/cddl-gplv2.html

  * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the

  * specific language governing permissions and limitations under the

  * License.  When distributing the software, include this License Header

  * Notice in each file and include the License file at

  * nbbuild/licenses/CDDL-GPL-2-CP.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the GPL Version 2 section of the License file that

  * accompanied this code. If applicable, add the following below the

  * License Header, with the fields enclosed by brackets [] replaced by

  * your own identifying information:

  * "Portions Copyrighted [year] [name of copyright owner]"

  *

  * Contributor(s):

  *

  * The Original Software is NetBeans. The Initial Developer of the Original

  * Software is Oracle. Portions Copyright 2013-2014 Oracle. All Rights Reserved.

  *

  * If you wish your version of this file to be governed by only the CDDL

  * or only the GPL Version 2, indicate your decision by adding

  * "[Contributor] elects to include this software in this distribution

  * under the [CDDL or GPL Version 2] license." If you do not indicate a

  * single choice of license, a recipient has the option to distribute

  * your version of this file under either the CDDL, the GPL Version 2 or

  * to extend the choice of license to its licensees as provided above.

  * However, if you add GPL Version 2 code and therefore, elected the GPL

  * Version 2 license, then the option applies only if the new code is

  * made subject to such option by the copyright holder.

  */

 package org.netbeans.html.json.spi;

 import java.lang.ref.WeakReference;

 import java.util.ArrayList;

 import java.util.Iterator;

 import java.util.LinkedList;

 import java.util.List;

 /**

  *

  * @author Jaroslav Tulach

  */

 final class Observers {

     private static final LinkedList<Watcher> GLOBAL = new LinkedList<Watcher>();

     private final List<Watcher> watchers = new ArrayList<Watcher>();

     private final List<Ref> observers = new ArrayList<Ref>();

     Observers() {

         assert Thread.holdsLock(GLOBAL);

     }

     static void beginComputing(Proto p, String name) {

         synchronized (GLOBAL) {

             verifyUnlocked(p);

             final Watcher nw = new Watcher(p, name);

             GLOBAL.push(nw);

         }

     }

     static void verifyUnlocked(Proto p) {

         synchronized (GLOBAL) {

             for (Watcher w : GLOBAL) {

                 if (w.proto == p) {

                     throw new IllegalStateException("Re-entrant attempt to access " + p);

                 }

             }

         }        

     }

     static void accessingValue(Proto p, String propName) {

         synchronized (GLOBAL) {

             verifyUnlocked(p);

             for (Watcher w : GLOBAL) {

                 Observers mine = p.observers(true);

                 mine.add(w, new Ref(w, propName));

             }

         }

     }

     static void finishComputing(Proto p) {

         synchronized (GLOBAL) {

             Watcher w = GLOBAL.pop();

             if (w.proto != p) {

                 throw new IllegalStateException("Inconsistency: " + w.proto + " != " + p);

             }

             if (w.prop != null) {

                 Observers mine = p.observers(true);

                 mine.add(w);

             }

         }

     }

     private static final class Ref extends WeakReference<Watcher> {

         private final String prop;

         public Ref(Watcher ref, String prop) {

             super(ref);

             this.prop = prop;

         }

         final Watcher watcher() {

             Watcher w = get();

             if (w == null) {

                 return null;

             }

             final Observers o = w.proto.observers(false);

             if (o == null) {

                 return null;

             }

             if (o.find(w.prop) == w) {

                 return w;

             }

             return null;

         }

     }

     private Watcher find(String prop) {

         if (prop == null) {

             return null;

         }

         for (Watcher w : watchers) {

             if (prop.equals(w.prop)) {

                 return w;

             }

         }

         return null;

     }

         final void add(Watcher w) {

         for (int i = 0; i < watchers.size(); i++) {

             Watcher ith = watchers.get(i);

             if (w.prop == null) {

                 if (ith.prop == null) {

                     watchers.set(i, w);

                     return;

                 }

             } else if (w.prop.equals(ith.prop)) {

                 watchers.set(i, w);

                 return;

             }

         }

         watchers.add(w);

     }

     static final void valueHasMutated(Proto p, String propName) {

         List<Watcher> mutated = new LinkedList<Watcher>();

         synchronized (GLOBAL) {

             Observers mine = p.observers(false);

             if (mine == null) {

                 return;

             }

             Iterator<Ref> it = mine.observers.iterator();

             while (it.hasNext()) {

                 Ref ref = it.next();

                 if (ref.get() == null) {

                     it.remove();

                     continue;

                 }

                 if (ref.prop.equals(propName)) {

                     Watcher w = ref.watcher();

                     if (w != null) {

                         mutated.add(w);

                     }

                 }

             }

         }

         for (Watcher w : mutated) {

             w.proto.valueHasMutated(w.prop);

         }

     }

     void add(Watcher w, Ref r) {

         Thread.holdsLock(GLOBAL);

         if (w == null) {

             return;

         }

         Iterator<Ref> it = observers.iterator();

         while (it.hasNext()) {

             Ref ref = it.next();

             if (r == ref) {

                 return;

             }

             final Watcher rw = ref.get();

             if (rw == null) {

                 it.remove();

                 continue;

             }

             if (rw == w && r.prop.equals(r.prop)) {

                 return;

             }

         }

         observers.add(r);

     }

     private static final class Watcher {

         final Proto proto;

         final String prop;

         Watcher(Proto proto, String prop) {

             this.proto = proto;

             this.prop = prop;

         }

         @Override

         public String toString() {

             return "Watcher: " + proto + ", " + prop;

         }

     }

 }