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    /*
 * 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.openide.util.lookup;

import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import org.openide.util.Lookup;
import org.openide.util.LookupEvent;
import org.openide.util.LookupListener;

import java.util.*;


/**
 * Simple proxy lookup. Keeps reference to a lookup it delegates to and
 * forwards all requests.
 *
 * @author Jaroslav Tulach
 */
final class SimpleProxyLookup extends org.openide.util.Lookup {
    /** the provider to check for the status */
    private Provider provider;

    /** the lookup we currently delegate to */
    private Lookup delegate;

    /** map of all templates to Reference (results) associated to this lookup */
    private WeakHashMap,Reference>> results;

    /**
     * @param provider provider to delegate to
     */
    SimpleProxyLookup(Provider provider) {
        this.provider = provider;
    }

    /** Checks whether we still delegate to the same lookup */
    private Lookup checkLookup() {
        Lookup l = provider.getLookup();

        // iterator over Reference (ProxyResult)
        Iterator>> toCheck = null;

        synchronized (this) {
            if (l != delegate) {
                this.delegate = l;

                if (results != null) {
                    toCheck = new ArrayList>>(results.values()).iterator();
                }
            }
        }

        if (toCheck != null) {
            // update
            ArrayList evAndListeners = new ArrayList();
            for (Iterator>> it = toCheck; it.hasNext(); ) {
                java.lang.ref.Reference> ref = it.next();
                if (ref == null) {
                    continue;
                }

                ProxyResult p = ref.get();

                if (p != null && p.updateLookup(null, null)) {
                    p.collectFires(evAndListeners);
                }
            }

            for (Iterator it = evAndListeners.iterator(); it.hasNext(); ) {
                LookupEvent ev = (LookupEvent)it.next();
                LookupListener ll = (LookupListener)it.next();
                ll.resultChanged(ev);
            }
        }
        return l;
    }

    final synchronized Lookup getLookupDelegate() {
        return delegate;
    }

    @SuppressWarnings("unchecked")
    private static  ProxyResult cast(ProxyResult p) {
        return (ProxyResult)p;
    }

    public  Result lookup(Template template) {
        ProxyResult newP;
        synchronized (this) {
            if (results == null) {
                results = new WeakHashMap,Reference>>();
            } else {
                Reference> ref = results.get(template);

                if (ref != null) {
                    ProxyResult p = ref.get();

                    if (p != null) {
                        return cast(p);
                    }
                }
            }

            newP = new ProxyResult(template);
            Reference> ref = new WeakReference>(newP);
            results.put(template, ref);
        }
        newP.checkResult();
        return newP;
    }

    public  T lookup(Class clazz) {
        if (clazz == null) {
            checkLookup();
            return null;
        }
        return checkLookup().lookup(clazz);
    }

    public  Item lookupItem(Template template) {
        return checkLookup().lookupItem(template);
    }

    /**
     * Result used in SimpleLookup. It holds a reference to the collection
     * passed in constructor. As the contents of this lookup result never
     * changes the addLookupListener and removeLookupListener are empty.
     */
    private final class ProxyResult extends WaitableResult implements LookupListener {
        /** Template used for this result. It is never null.*/
        private final Template template;

        /** result to delegate to */
        private Lookup.Result delegate;

        /** listeners set */
        private LookupListenerList listeners;
        private WeakResult lastListener;

        /** Just remembers the supplied argument in variable template.*/
        ProxyResult(Template template) {
            this.template = template;
        }

        /** Checks state of the result
         */
        private Result checkResult() {
            Lookup.Result lkp;
            synchronized (this) {
                lkp = getDelegate();
            }
            checkLookup();
            Lookup.Result[] used = { null };
            updateLookup(lkp, used);
            return used[0];
        }

        /** Updates the state of the lookup.
         * @return true if the lookup really changed
         */
        public boolean updateLookup(Lookup.Result prev, Lookup.Result[] used) {
            Collection> oldPairs = null;
            LookupListener prevListener;
            Result toAdd;
            WeakResult listenerToAdd;
            for (;;) {
                Lookup l;
                Result del;
                synchronized (this) {
                    l = getLookupDelegate();
                    del = getDelegate();
                    if ((del != null) && (getLastListener() != null)) {
                        prevListener = getLastListener();
                        del.removeLookupListener(getLastListener());
                    } else {
                        prevListener = null;
                    }
                }
                if (oldPairs == null) {
                    if (prev != null) {
                        oldPairs = prev.allItems();
                    } else if (used == null && del != null) {
                        oldPairs = del.allItems();
                    }
                }

                // cannot call to foreign code
                toAdd = l.lookup(template);

                synchronized (this) {
                    WeakResult ll = getLastListener();
                    if (prevListener == ll) {
                        if (ll != null && ll.source == toAdd && ll.result.get() == this) {
                            listenerToAdd = ll;
                        } else {
                            listenerToAdd = new WeakResult(this, toAdd);
                        }
                        setLastListener(listenerToAdd);
                        setDelegate(toAdd);
                        if (used != null) {
                            used[0] = toAdd;
                        }
                        break;
                    }
                }
            }
            toAdd.addLookupListener(listenerToAdd);

            if (oldPairs == null) {
                // nobody knows about a change
                return false;
            }

            Collection> newPairs = toAdd.allItems();

            // See #34961 for explanation.
            if (!(oldPairs instanceof List)) {
                if (oldPairs == Collections.EMPTY_SET) {
                    // avoid allocation
                    oldPairs = Collections.emptyList();
                } else {
                    oldPairs = new ArrayList>(oldPairs);
                }
            }

            if (!(newPairs instanceof List)) {
                newPairs = new ArrayList>(newPairs);
            }

            return !oldPairs.equals(newPairs);
        }

        @Override
        public void addLookupListener(LookupListener l) {
            getListeners(l, null);
        }

        @Override
        public void removeLookupListener(LookupListener l) {
            getListeners(null, l);
        }

        public java.util.Collection allInstances() {
            return checkResult().allInstances();
        }

        public Set> allClasses() {
            return checkResult().allClasses();
        }

        public Collection> allItems() {
            return checkResult().allItems();
        }

        protected void beforeLookup(Lookup.Template t) {
            Lookup.Result r = checkResult();

            if (r instanceof WaitableResult) {
                ((WaitableResult) r).beforeLookup(t);
            }
        }

        /** A change in lookup occured.
         * @param ev event describing the change
         *
         */
        public void resultChanged(LookupEvent anEvent) {
            collectFires(null);
        }

        @Override
        protected void collectFires(Collection evAndListeners) {
            LookupListenerList l = this.getListeners(null, null);

            if (l == null) {
                return;
            }

            Object[] listeners = l.getListenerList();

            if (listeners.length == 0) {
                return;
            }

            LookupEvent ev = new LookupEvent(this);
            AbstractLookup.notifyListeners(listeners, ev, evAndListeners);
        }

        @Override
        protected Collection allInstances(boolean callBeforeLookup) {
            return allInstances();
        }

        @Override
        protected Collection> allItems(boolean callBeforeLookup) {
            return allItems();
        }

        /** Access to listeners. Initializes the listeners field if needed -
         * e.g. if adding a listener and listeners are null.
         *
         * @return the listeners
         */
        private synchronized LookupListenerList getListeners(LookupListener toAdd, LookupListener toRemove) {
            if (toAdd == null && listeners == null) {
                return null;
            }
            if (listeners == null) {
                listeners = new LookupListenerList();
            }
            if (toAdd != null) {
                listeners.add(toAdd);
            }
            if (toRemove != null) {
                listeners.remove(toRemove);
            }
            return listeners;
        }

        private Lookup.Result getDelegate() {
            assert Thread.holdsLock(this);
            return delegate;
        }

        private void setDelegate(Lookup.Result delegate) {
            assert Thread.holdsLock(this);
            this.delegate = delegate;
        }

        private WeakResult getLastListener() {
            assert Thread.holdsLock(this);
            return lastListener;
        }

        private void setLastListener(WeakResult lastListener) {
            assert Thread.holdsLock(this);
            this.lastListener = lastListener;
        }
    }
     // end of ProxyResult
    private final class WeakResult extends WaitableResult implements LookupListener {
        final Lookup.Result source;
        final Reference> result;

        WeakResult(ProxyResult r, Lookup.Result s) {
            this.result = new WeakReference>(r);
            this.source = s;
        }

        protected void beforeLookup(Lookup.Template t) {
            ProxyResult r = (ProxyResult)result.get();
            if (r != null) {
                r.beforeLookup(t);
            } else {
                source.removeLookupListener(this);
            }
        }

        protected void collectFires(Collection evAndListeners) {
            ProxyResult r = result.get();
            if (r != null) {
                r.collectFires(evAndListeners);
            } else {
                source.removeLookupListener(this);
            }
        }

        public void addLookupListener(LookupListener l) {
            assert false;
        }

        public void removeLookupListener(LookupListener l) {
            assert false;
        }

        public Collection allInstances() {
            assert false;
            return null;
        }

        public void resultChanged(LookupEvent ev) {
            ProxyResult r = (ProxyResult)result.get();
            if (r != null) {
                r.resultChanged(ev);
            } else {
                source.removeLookupListener(this);
            }
        }

        public Collection> allItems() {
            assert false;
            return null;
        }
        @Override
        protected Collection> allItems(boolean callBeforeLookup) {
            return allItems();
        }

        public Set> allClasses() {
            assert false;
            return null;
        }

        @Override
        protected Collection allInstances(boolean callBeforeLookup) {
            return allInstances();
        }

        @Override
        public String toString() {
            return "SimpleProxy$WeakResult[source=" + source + "]";
        }
    } // end of WeakResult
}
    
    
    
    

    




    
    
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