/*
    * The Kuali Financial System, a comprehensive financial management system for higher education.
    * 
    * Copyright 2005-2014 The Kuali Foundation
    * 
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Affero General Public License as
    * published by the Free Software Foundation, either version 3 of the
    * License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU Affero General Public License for more details.
   * 
   * You should have received a copy of the GNU Affero General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  package org.kuali.kfs.sys.util;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * A Map which wraps another Map, presumably one which is read-only (such as org.kuali.kfs.sys.util.ReflectionMap).  This Map holds a secondary Map which can be written to and read from; but if, in get, the key
   * is not present in the internally maintained Map, then the get falls back to the wrapped read-only Map to find the value
   */
  public class FallbackMap<K, V> implements Map<K, V> {
      protected Map<K, V> frontMap;
      protected Map<K, V> backMap;
  
      public FallbackMap(Map<K,V> backMap) {
          frontMap = new HashMap<>();
          this.backMap = backMap;
      }
  
      @Override
      public int size() {
          return frontMap.size() + backMap.size();
      }
  
      @Override
      public boolean isEmpty() {
          return frontMap.isEmpty() && backMap.isEmpty();
      }
  
      @Override
      public boolean containsKey(Object key) {
          if (frontMap.containsKey(key)) {
              return true;
          }
          return backMap.containsKey(key);
      }
  
      @Override
      public boolean containsValue(Object value) {
          if (frontMap.containsValue(value)) {
              return true;
          }
          return backMap.containsValue(value);
      }
  
      @Override
      public V get(Object key) {
          if (frontMap.containsKey(key)) {
              return frontMap.get(key);
          }
          return backMap.get(key);
      }
  
      @Override
      public V put(K key, V value) {
          return frontMap.put(key, value);
      }
  
      @Override
      public V remove(Object key) {
          if (frontMap.containsKey(key)) {
              return frontMap.remove(key);
          }
          return backMap.remove(key);
      }
  
      @Override
      public void putAll(Map<? extends K, ? extends V> m) {
          frontMap.putAll(m);
      }
  
      @Override
      public void clear() {
          frontMap.clear();
          backMap.clear();
      }
  
     @Override
     public Set<K> keySet() {
         Set<K> keys = new HashSet<>();
         keys.addAll(frontMap.keySet());
         keys.addAll(backMap.keySet());
         return keys;
     }
 
     @Override
     public Collection<V> values() {
         List<V> values = new ArrayList<>();
         values.addAll(frontMap.values());
         values.addAll(backMap.values());
         return values;
     }
 
     @Override
     public Set<java.util.Map.Entry<K, V>> entrySet() {
         Set<java.util.Map.Entry<K, V>> entries = new HashSet<>();
         entries.addAll(frontMap.entrySet());
         entries.addAll(backMap.entrySet());
         return entries;
     }
 
 }