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package com.ericsson.research.trap.utils;

/*
 * ##_BEGIN_LICENSE_##
 * Transport Abstraction Package (trap)
 * ----------
 * Copyright (C) 2014 Ericsson AB
 * ----------
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * 3. Neither the name of the Ericsson AB nor the names of its contributors
 *    may be used to endorse or promote products derived from this software without
 *    specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ##_END_LICENSE_##
 */

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.ConcurrentSkipListMap;

/**
 * Provides a map with a weak binding of its values. Backed by ConcurrentSkipListMap and RefQueues. Thread safe, OK performance. Mainly intended for NIO-style objects where we want the
 * objects to be GC-able unless referenced by the application. Keys are strongly bound (generally assumed to be an identifier belonging to the object anyway).
 * 
 * @author evlakat
 */
public class WeakMap implements Map
{
	
	ConcurrentSkipListMap>	values		= new ConcurrentSkipListMap>();
	ReferenceQueue										refQueue	= new ReferenceQueue();
	
	public int size()
	{
		return this.values.size();
	}
	
	public boolean isEmpty()
	{
		return this.values.isEmpty();
	}
	
	public boolean containsKey(Object key)
	{
		this.flushExpiredValues();
		return this.values.containsKey(key);
	}
	
	private void flushExpiredValues()
	{
		for (;;)
		{
			Reference ref = this.refQueue.poll();
			
			if (ref == null)
				return;
			
			this.values.remove(((EqualMappedWeakReference) ref).key);
		}
	}
	
	public boolean containsValue(Object value)
	{
		return this.values.containsValue(new EqualWeakReference(value));
	}
	
	public V get(Object key)
	{
		
		this.flushExpiredValues();
		EqualWeakReference ref = this.values.get(key);
		
		if (ref != null)
			return ref.get();
		else
			return null;
	}
	
	public V put(K key, V value)
	{
		this.flushExpiredValues();
		this.values.put(key, new EqualMappedWeakReference(value, key, this.refQueue));
		return value;
	}
	
	public V remove(Object key)
	{
		this.flushExpiredValues();
		EqualWeakReference ref = this.values.remove(key);
		
		if (ref != null)
			return ref.get();
		
		return null;
	}
	
	public void putAll(Map m)
	{
		Set entrySet = m.entrySet();
		
		for (Object o : entrySet)
		{
			@SuppressWarnings("unchecked")
			Entry e = (Entry) o;
			this.put(e.getKey(), e.getValue());
		}
	}
	
	public void clear()
	{
		this.values.clear();
	}
	
	public Set keySet()
	{
		this.flushExpiredValues();
		return this.values.keySet();
	}
	
	public Collection values()
	{
		Collection> vs = this.values.values();
		
		HashSet rv = new HashSet();
		
		for (EqualWeakReference v : vs)
		{
			V val = v.get();
			
			if (val != null)
				rv.add(val);
		}
		
		this.flushExpiredValues();
		return rv;
	}
	
	public Set> entrySet()
	{
		this.flushExpiredValues();
		
		Set>> entries = this.values.entrySet();
		Set> rv = new HashSet>();
		
		for (Entry> entry : entries)
		{
			V v = entry.getValue().get();
			if (v != null)
			{
				Entry e = new ReturnedEntry(entry.getKey(), entry.getValue().get(), this);
				rv.add(e);
			}
		}
		return rv;
	}
	
}

class EqualWeakReference extends WeakReference
{
	
	public EqualWeakReference(T referent, ReferenceQueue q)
	{
		super(referent, q);
	}
	
	public EqualWeakReference(T value)
	{
		super(value);
	}
	
	@Override
	public int hashCode()
	{
		T t = this.get();
		return t != null ? t.hashCode() : 0;
	}
	
	@Override
	public boolean equals(Object obj)
	{
		T t = this.get();
		return t != null ? t.equals(obj) : false;
	}
	
	@Override
	public String toString()
	{
		T t = this.get();
		
		if (t != null)
			return t.toString();
		else
			return "WeakReference " + super.toString() + " with null referent.";
	}
	
}

class EqualMappedWeakReference extends EqualWeakReference
{
	
	final Object	key;
	
	public EqualMappedWeakReference(T referent, Object key, ReferenceQueue q)
	{
		super(referent, q);
		this.key = key;
	}

    @Override
    public boolean equals(Object obj)
    {
        return super.equals(obj);
    }

    @Override
    public int hashCode()
    {
        return super.hashCode();
    }
	
}

class ReturnedEntry implements Entry
{
	
	K			key;
	V			value;
	Map	map;
	
	ReturnedEntry(K key, V value, Map map)
	{
		this.key = key;
		this.value = value;
		this.map = map;
	}
	
	public K getKey()
	{
		return this.key;
	}
	
	public V getValue()
	{
		return this.value;
	}
	
	public V setValue(V value)
	{
		this.map.put(this.key, value);
		this.value = value;
		return value;
	}
	
}
    

    

    

            

    

            



    
    






    
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