package org.csc.phynixx.common.utils;
   
   /*
    * #%L
    * phynixx-common
    * %%
    * Copyright (C) 2014 Christoph Schmidt-Casdorff
    * %%
    * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   * #L%
   */
  
  
  import java.util.*;
  
  /**
   * Associations betweeen Instances of X and Y can be grouped. To join a group  you have to give an assoc you want to share the group. You can assign a group Value to a group
   * Created by christoph on 09.02.14.
   */
  public class GroupingAssociation<X, Y, A> {
  
  
      private final Map<X, Set<Y>> mapA = new HashMap<X, Set<Y>>();
  
      private final Map<Y, Set<X>> mapB = new HashMap<Y, Set<X>>();
  
  
      public void associate(X x, Y y) {
          assertSet(mapA, x).add(y);
          assertSet(mapB, y).add(x);
      }
  
  
      public Set<Y> getX(X x) {
          return getEndpoints(x, mapA);
      }
  
      public Set<X> getY(Y y) {
          return getEndpoints(y, mapB);
      }
  
  
      public void removeX(X x) {
          removeDependents(x, mapA, mapB);
          mapA.remove(x);
      }
  
  
      public void removeY(Y y) {
          removeDependents(y, mapB, mapA);
          mapB.remove(y);
      }
  
  
      public void disassociate(X x, Y y) {
          removeDependent(x, y, mapA);
          removeDependent(y, x, mapB);
      }
  
  
      static <K, V> Set<V> getEndpoints(K k, Map<K, Set<V>> map) {
          Set<V> value = map.get(k);
          if (value == null) {
              return Collections.emptySet();
          }
          return Collections.unmodifiableSet(value);
      }
  
  
      static <K, V> void removeDependents(K key, Map<K, Set<V>> map, Map<V, Set<K>> inverseMap) {
          Set<V> value = map.get(key);
          if (value != null && !value.isEmpty()) {
              for (V v : value) {
                  Set<K> keys = inverseMap.get(v);
                  if (keys != null && !keys.isEmpty()) {
                      keys.remove(key);
                  }
              }
          }
      }
  
      static <K, V> void removeDependent(K k, V v, Map<K, Set<V>> map) {
          Set<V> value = map.get(k);
          if (value != null && !value.isEmpty()) {
              value.remove(v);
          }
      }
  
  
     static <K, V> Set<V> assertSet(Map<K, Set<V>> map, K key) {
         Set<V> value = map.get(key);
         if (value == null) {
             value = new HashSet<V>();
             map.put(key, value);
         }
         return value;
     }
 
 
 }