package cz.cuni.amis.utils.maps;
   
   import java.util.Collection;
   import java.util.HashMap;
   import java.util.Map;
   import java.util.Map.Entry;
   import java.util.Set;
   
   /**
   * Maps whose items are initialized on demand by create(K) method.
   * @author ik
   */
  public abstract class LazyMap<K, V> implements Map<K, V> {
  
      Map<K, V> map = null;
  
      /**
       * Creates value for given key.
       * @param key
       * @return
       */
      protected abstract V create(K key);
  
      public LazyMap() {
          map = new HashMap<K, V>();
      }
  
      public LazyMap(Map<K, V> baseMap) {
          map = baseMap;
      }
  
  
      @Override
      public int size() {
          return map.size();
      }
  
      @Override
      public boolean isEmpty() {
          return map.isEmpty();
      }
  
      @Override
      public boolean containsKey(Object key) {
          return map.containsKey(key);
      }
  
      @Override
      public boolean containsValue(Object value) {
          return map.containsValue(value);
      }
  
      @Override
      public V get(Object key) {
          V val = map.get((K)key);
          if(val == null) {
          	synchronized(this) {
          		val = map.get((K)key);
          		if (val != null) return val;
  	            val = create((K)key);
  	            if(val != null) {
  	                map.put((K)key, val);
  	            }
          	}
          }
          return val;
      }
  
      @Override
      public V put(K key, V value) {
      	return map.put(key, value);
      }
  
      @Override
      public V remove(Object key) {
          return map.remove(key);
      }
  
      @Override
      public void putAll(Map<? extends K, ? extends V> m) {
          map.putAll(m);
      }
  
      @Override
      public void clear() {
          map.clear();
      }
  
      @Override
      public Set<K> keySet() {
          return map.keySet();
      }
  
      @Override
      public Collection<V> values() {
          return map.values();
      }
  
      @Override
     public Set<Entry<K, V>> entrySet() {
         return map.entrySet();
     }
 
 }