package com.planet_ink.coffee_mud.core.collections;
import java.lang.ref.WeakReference;
import java.util.*;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
/*
Copyright 2016-2019 Bo Zimmerman
Licensed 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.
*/
public class WeakArrayList<T> extends AbstractList<T>
{
private final ArrayList<WeakReference<T>> list;
private final AtomicBoolean needsCleaning = new AtomicBoolean(false);
private final AtomicLong lastCleaning = new AtomicLong(0);
private static final long cleanIntervalMs = 30000;
public WeakArrayList()
{
list = new ArrayList<WeakReference<T>>();
}
public WeakArrayList(final Collection<T> c)
{
list = new ArrayList<WeakReference<T>>();
addAll(0, c);
}
@Override
public synchronized boolean add(final T element)
{
if(this.needsCleaning.get() && ((System.currentTimeMillis() - this.lastCleaning.get()) > cleanIntervalMs))
cleanReleased();
return list.add(new WeakReference<T>(element));
}
@Override
public synchronized boolean remove(final Object element)
{
if(this.needsCleaning.get() && ((System.currentTimeMillis() - this.lastCleaning.get()) > cleanIntervalMs))
cleanReleased();
return super.remove(element);
}
@Override
public synchronized T remove(final int index)
{
if(this.needsCleaning.get() && ((System.currentTimeMillis() - this.lastCleaning.get()) > cleanIntervalMs))
cleanReleased();
return super.remove(index);
}
@Override
public synchronized void add(final int index, final T element)
{
if(this.needsCleaning.get() && ((System.currentTimeMillis() - this.lastCleaning.get()) > cleanIntervalMs))
cleanReleased();
list.add(index, new WeakReference<T>(element));
}
@Override
public synchronized Iterator<T> iterator()
{
if(this.needsCleaning.get() && ((System.currentTimeMillis() - this.lastCleaning.get()) > cleanIntervalMs))
cleanReleased();
return new FilteredIterator<T>(new ConvertingIterator<WeakReference<T>,T>(list.iterator(), WeakConverter), WeakFilterer);
}
@Override
public synchronized int size()
{
if(this.needsCleaning.get())
cleanReleased();
return list.size();
}
@Override
public synchronized T get(final int index)
{
if(this.needsCleaning.get() && ((System.currentTimeMillis() - this.lastCleaning.get()) > cleanIntervalMs))
cleanReleased();
return list.get(index).get();
}
private synchronized void cleanReleased()
{
for (final Iterator<WeakReference<T>> it = list.iterator(); it.hasNext();)
{
final WeakReference<T> ref =it.next();
if (ref.get() == null)
it.remove();
}
this.needsCleaning.set(false);
this.lastCleaning.set(System.currentTimeMillis());
}
private final Filterer<T> WeakFilterer = new Filterer<T>()
{
@Override
public boolean passesFilter(final T obj)
{
return (obj != null);
}
};
private final Converter<WeakReference<T>, T> WeakConverter = new Converter<WeakReference<T>, T>()
{
@Override
public T convert(final WeakReference<T> obj)
{
if(obj == null)
return null;
if(obj.get() == null)
{
needsCleaning.set(true);
}
return obj.get();
}
};
}
