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

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

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

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 * 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

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 * 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

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 *

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

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

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

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

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

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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;

        }

    }

}