//$Id: IdentitySet.java 8807 2005-12-09 15:27:05Z epbernard $
package org.hibernate.util;

import java.util.Set;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

/**
 * Set implementation that use == instead of equals() as its comparison mechanism
 * that base its implementation of IdentityMap
 * 
 * @author Emmanuel Bernard
 */
public class IdentitySet implements Set {
	private Map map;
	private static final Object DUMP_VALUE = new Object();

	public IdentitySet() {
		this.map = IdentityMap.instantiate( 10 );
	}

	public int size() {
		return map.size();
	}

	public boolean isEmpty() {
		return map.isEmpty();
	}

	public boolean contains(Object o) {
		return map.get( o ) == DUMP_VALUE;
	}

	public Iterator iterator() {
		return map.entrySet().iterator();
	}

	public Object[] toArray() {
		return map.entrySet().toArray();
	}

	public Object[] toArray(Object[] a) {
		return map.entrySet().toArray(a);
	}

	public boolean add(Object o) {
		return map.put( o, DUMP_VALUE) == null;
	}

	public boolean remove(Object o) {
		return map.remove( o ) == DUMP_VALUE;
	}

	public boolean containsAll(Collection c) {
		Iterator it = c.iterator();
		while ( it.hasNext() ) {
			if ( ! map.containsKey( it.next() ) ) return false;
		}
		return true;
	}

	public boolean addAll(Collection c) {
		Iterator it = c.iterator();
		boolean changed = false;
		while ( it.hasNext() ) {
			if ( this.add( it.next() ) ) changed = true;
		}
		return changed;
	}

	public boolean retainAll(Collection c) {
		//doable if needed
		throw new UnsupportedOperationException();
	}

	public boolean removeAll(Collection c) {
		Iterator it = c.iterator();
		boolean changed = false;
		while ( it.hasNext() ) {
			if ( this.remove( it.next() ) ) changed = true;
		}
		return changed;
	}

	public void clear() {
		map.clear();
	}
}