/*
 * GNU LESSER GENERAL PUBLIC LICENSE Copyright (C) 2006 The Lobo Project
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Contact info: lobochief@users.sourceforge.net
 */
/*
 * Created on Oct 8, 2005
 */
package com.nvarghese.beowulf.common.cobra.util;

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class WeakValueHashMap implements Map {

	private final Map map = new HashMap();
	private final ReferenceQueue queue = new ReferenceQueue();

	public WeakValueHashMap() {

		super();
	}

	public int size() {

		return this.map.size();
	}

	public boolean isEmpty() {

		return this.map.isEmpty();
	}

	public boolean containsKey(final Object key) {

		WeakReference wf = (WeakReference) this.map.get(key);
		return wf != null && wf.get() != null;
	}

	public boolean containsValue(final Object value) {

		throw new UnsupportedOperationException();
	}

	public Object get(Object key) {

		this.checkQueue();
		WeakReference wf = (WeakReference) this.map.get(key);
		return wf == null ? null : wf.get();
	}

	public Object put(final Object key, final Object value) {

		this.checkQueue();
		return this.putImpl(key, value);
	}

	private final Object putImpl(final Object key, final Object value) {

		if (value == null) {
			throw new IllegalArgumentException("null values not accepted");
		}
		Reference ref = new LocalWeakReference(key, value, this.queue);
		WeakReference oldWf = (WeakReference) this.map.put(key, ref);
		return oldWf == null ? null : oldWf.get();
	}

	public Object remove(final Object key) {

		this.checkQueue();
		WeakReference wf = (WeakReference) this.map.remove(key);
		return wf == null ? null : wf.get();
	}

	public void putAll(Map t) {

		this.checkQueue();
		Iterator i = t.entrySet().iterator();
		while (i.hasNext()) {
			Map.Entry entry = (Map.Entry) i.next();
			this.putImpl(entry.getKey(), entry.getValue());
		}
	}

	public void clear() {

		this.checkQueue();
		this.map.clear();
	}

	public Set keySet() {

		return this.map.keySet();
	}

	private final void checkQueue() {

		ReferenceQueue queue = this.queue;
		LocalWeakReference ref;
		while ((ref = (LocalWeakReference) queue.poll()) != null) {
			this.map.remove(ref.getKey());
		}
	}

	public Collection values() {

		return new FilteredCollection(this.map.values(), new LocalFilter());
	}

	public Set entrySet() {

		throw new UnsupportedOperationException();
	}

	private class LocalFilter implements ObjectFilter {

		/*
		 * (non-Javadoc)
		 * 
		 * @see org.xamjwg.util.ObjectFilter#decode(java.lang.Object)
		 */
		public Object decode(final Object source) {

			WeakReference wf = (WeakReference) source;
			return wf == null ? null : wf.get();
		}

		/*
		 * (non-Javadoc)
		 * 
		 * @see org.xamjwg.util.ObjectFilter#encode(java.lang.Object)
		 */
		public Object encode(final Object source) {

			throw new java.lang.UnsupportedOperationException("Read-only collection.");
		}
	}

	private static class LocalWeakReference extends WeakReference {

		private final Object key;

		public LocalWeakReference(final Object key, final Object target, final ReferenceQueue queue) {

			super(target, queue);
			this.key = key;
		}

		public Object getKey() {

			return key;
		}

		public boolean equals(final Object other) {

			Object target1 = this.get();
			Object target2 = other instanceof LocalWeakReference ? ((LocalWeakReference) other).get() : null;
			return Objects.equals(target1, target2);
		}

		public int hashCode() {

			Object target = this.get();
			return target == null ? 0 : target.hashCode();
		}
	}
}