package cz.cuni.amis.utils.maps;
   
   import java.util.Collections;
   import java.util.HashMap;
   import java.util.Map;
   import java.util.WeakHashMap;
   
   
   /**
   * Three-level hash map, where the PRIMARY_KEY maps are implemented using
   * {@link WeakHashMap}.
   * This means, that the PRIMARY_KEY maps, may be garbage collected unless there is a direct reference to the PRIMARY_KEY.
   * @author srlok
   *
   * @param <PRIMARY_KEY>
   * @param <SECONDARY_KEY>
   * @param <TERTIARY_KEY> 
   * @param <ITEM>
   */
  public class WeakHashTriMap<PRIMARY_KEY,SECONDARY_KEY,TERTIARY_KEY,ITEM>
  	extends WeakHashMap<PRIMARY_KEY,Map<SECONDARY_KEY,Map<TERTIARY_KEY,ITEM>>> 
  {
  
  	/**
  	 * 
  	 */
  	private static final long serialVersionUID = 1L;
  
  	private int secondaryCapacity;
  	private int tertiaryCapacity;
  	
  	/**
  	 * Creates a WeakHashTriMap with default loadFactor(0.75) and default starting capacities (16,16,16)
  	 */
  	public WeakHashTriMap()
  	{
  		secondaryCapacity = 16;
  		tertiaryCapacity = 16;
  	}
  	
  	/**
  	 * Creates a new WeakHashTriMap with the default loadFactor (0.75) for all levels and the provided starting capacties for different levels.
  	 * @param primaryCapacity
  	 * @param secondaryCapacity
  	 * @param tertiaryCapacity
  	 */
  	public WeakHashTriMap( int primaryCapacity, int secondaryCapacity, int tertiaryCapacity)
  	{
  		super(primaryCapacity);
  		this.secondaryCapacity = secondaryCapacity;
  		this.tertiaryCapacity = tertiaryCapacity;
  	}
  	
  	/**
  	 * Returns a HashMap<SECONDARY_KEY,HashMap<TERTIARY_KEY,ITEM>>
  	 * Never returns null, if the map under primary key doesn't exist, an empty one is added and returned.
  	 * @param primaryKey
  	 * @return
  	 */
  	@SuppressWarnings("unchecked")
  	@Override
  	public Map<SECONDARY_KEY, Map<TERTIARY_KEY,ITEM>> get(Object primaryKey)
  	{
  		Map<SECONDARY_KEY, Map<TERTIARY_KEY,ITEM>> result = super.get(primaryKey);
  		if (result != null) { return result; };
  		result = Collections.synchronizedMap( new HashMapMap<SECONDARY_KEY,TERTIARY_KEY,ITEM>(secondaryCapacity, tertiaryCapacity) );
  		super.put( (PRIMARY_KEY)primaryKey,result);
  		return result;
  	}
  	
  	/**
  	 * Returns the requested map, never returns null.
  	 * If the map does not exist an empty map is created and returned.
  	 * @param primaryKey
  	 * @param secondaryKey
  	 * @return
  	 */
  	public Map<TERTIARY_KEY,ITEM> get(PRIMARY_KEY primaryKey, SECONDARY_KEY secondaryKey)
  	{
  		Map<TERTIARY_KEY, ITEM> result = get(primaryKey).get(secondaryKey);
  		if (result != null) { return result; };
  		result = Collections.synchronizedMap( new HashMap<TERTIARY_KEY,ITEM>( tertiaryCapacity ));
  		get(primaryKey).put(secondaryKey, result);
  		return result;
  	}
  	
  	/**
  	 * Returns item specified, returns null if item does not appear in the map.
  	 * @param primaryKey
  	 * @param secondaryKey
  	 * @param tertiaryKey
  	 * @return
  	 */
  	public ITEM get(PRIMARY_KEY primaryKey, SECONDARY_KEY secondaryKey, TERTIARY_KEY tertiaryKey)
  	{
  		return get(primaryKey,secondaryKey).get(tertiaryKey);
  	}
  	
  	/**
 	 * Puts the item into the map.
 	 * @param primaryKey
 	 * @param secondaryKey
 	 * @param tertiaryKey
 	 * @param item
 	 */
 	public void put(PRIMARY_KEY primaryKey, SECONDARY_KEY secondaryKey, TERTIARY_KEY tertiaryKey, ITEM item)
 	{
 		get(primaryKey,secondaryKey).put(tertiaryKey, item);
 	}
 	
 	/**
 	 * Removes the requested map. If the map doesn't exist, returns an empty map.
 	 */
 	@Override
 	public Map<SECONDARY_KEY, Map<TERTIARY_KEY,ITEM>> remove(Object primaryKey)
 	{
 		Map<SECONDARY_KEY, Map<TERTIARY_KEY,ITEM>> result = super.remove(primaryKey);
 		if (result != null) { return result; };
 		return Collections.synchronizedMap( new HashMapMap<SECONDARY_KEY, TERTIARY_KEY,ITEM>(secondaryCapacity, tertiaryCapacity) );
 	}
 	
 	/**
 	 * removes the map under primary and secondary key, if the map does not exist,
 	 * the data structure is not changed and a new map is returned.
 	 * @param primaryKey
 	 * @param secondaryKey
 	 * @return
 	 */
 	public Map<TERTIARY_KEY,ITEM> remove(PRIMARY_KEY primaryKey, SECONDARY_KEY secondaryKey)
 	{
 		Map<TERTIARY_KEY,ITEM> result = get(primaryKey).remove(secondaryKey);
 		if ( result != null) { return result; };
 		return Collections.synchronizedMap( new HashMap<TERTIARY_KEY, ITEM> (tertiaryCapacity));
 	}
 	
 	/**
 	 * Returns the item under specified keys and removes it from the map,
 	 * returns null if item is not present in the map.
 	 * @param primaryKey
 	 * @param secondaryKey
 	 * @param tertiaryKey
 	 * @return
 	 */
 	public ITEM remove(PRIMARY_KEY primaryKey, SECONDARY_KEY secondaryKey, TERTIARY_KEY tertiaryKey)
 	{
 		return get(primaryKey,secondaryKey).remove(tertiaryKey);
 	}
 
 }