package cz.cuni.amis.utils.collections;
   
   import java.util.Collection;
   import java.util.Iterator;
   
   import cz.cuni.amis.utils.maps.AbstractLazyMap;
   
   /**
    * Read-only Collection used for lazy implementation of Map.values().
   * The items in this collection are backed by the map and Map.get() is used if an object is required.
   * @author srlok
   *
   */
  public class LazyMapValuesCollection<VALUE,KEY> implements Collection<VALUE> {
  
  	private AbstractLazyMap<KEY,VALUE> map;
  	
  	public AbstractLazyMap<KEY,VALUE> getBaseMap()
  	{
  		return map;
  	}
  	
  	public LazyMapValuesCollection(AbstractLazyMap<KEY,VALUE> sourceMap)
  	{
  		map = sourceMap;
  	}
  	
  	@Override
  	public boolean add(VALUE e) {
  		return false;
  	}
  
  	@Override
  	public boolean addAll(Collection<? extends VALUE> c) {		
  		return false;
  	}
  
  	@Override
  	public void clear() {
  	}
  
  	@Override
  	/**
  	 * Warning! may have - O(N) complexity!
  	 */
  	public boolean contains(Object o) {
  		for ( Object key : map.keySet() )
  		{
  			if ( map.get(key).equals(o))
  			{
  				return true;
  			}
  		}
  		return false;
  	}
  
  	@Override
  	/**
  	 * Warning! O(N)*M complexity!
  	 */
  	public boolean containsAll(Collection<?> c) {
  		for ( Object o : c)
  		{
  			if ( !contains(o))
  			{
  				return false;
  			}
  		}
  		return true;
  	}
  
  	@Override
  	public boolean isEmpty() {
  		return map.isEmpty();
  	}
  
  	@Override
  	public Iterator<VALUE> iterator() {
  		return new Iterator<VALUE>()
  		{
  			Iterator<KEY> it = null;
  			KEY value = null;
  			
  			{
  				it = getBaseMap().keySet().iterator();
  			}
  			
  			@Override
  			public boolean hasNext() {
  				return it.hasNext();
  			}
  
  			@Override
  			public VALUE next() {
  				value = it.next();
  				return getBaseMap().get(value);
  			}
  
  			@Override
 			public void remove() {
 				getBaseMap().remove(value);
 				
 			}
 			
 		};
 	}
 
 	@Override
 	public boolean remove(Object o) {
 		return false;
 	}
 
 	@Override
 	public boolean removeAll(Collection<?> c) {
 		return false;
 	}
 
 	@Override
 	public boolean retainAll(Collection<?> c) {
 		return false;
 	}
 
 	@Override
 	public int size() {
 		return map.size();
 	}
 
 	@Override
 	public Object[] toArray() {
 		Object[] arr = new Object[ map.size()];
 		int i = 0;
 		for ( Object key : map.keySet() )
 		{
 			arr[i] = map.get(key);
 		}
 		return arr;
 	}
 
 	@Override
 	public <T> T[] toArray(T[] a) {
 		Object[] arr = new Object[ map.size()];
 		int i = 0;
 		for ( Object key : map.keySet() )
 		{
 			arr[i] = map.get(key);
 		}
 		return (T[])arr;
 	}
 
 }