package org.apache.jcs.utils.struct;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.
   */
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Hashtable;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Set;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.jcs.engine.control.group.GroupAttrName;
  import org.apache.jcs.engine.stats.StatElement;
  import org.apache.jcs.engine.stats.Stats;
  import org.apache.jcs.engine.stats.behavior.IStatElement;
  import org.apache.jcs.engine.stats.behavior.IStats;
  
  /**
   * This is a simple LRUMap. It implements most of the map methods. It is not recommended that you
   * use any but put, get, remove, and clear.
   * <p>
   * Children can implement the processRemovedLRU method if they want to handle the removal of the
   * lest recently used item.
   * <p>
   * This class was abstracted out of the LRU Memory cache. Put, remove, and get should be thread
   * safe. It uses a hashtable and our own double linked list.
   * <p>
   * Locking is done on the instance.
   * <p>
   * @author aaron smuts
   */
  public class LRUMap<K, V>
      implements Map<K, V>
  {
      /** The logger */
      private final static Log log = LogFactory.getLog( LRUMap.class );
  
      /** double linked list for lru */
      private final DoubleLinkedList<LRUElementDescriptor<K, V>> list;
  
      /** Map where items are stored by key. */
      protected Map<K, LRUElementDescriptor<K, V>> map;
  
      /** stats */
      int hitCnt = 0;
  
      /** stats */
      int missCnt = 0;
  
      /** stats */
      int putCnt = 0;
  
      /** if the max is less than 0, there is no limit! */
      int maxObjects = -1;
  
      /** make configurable */
      private int chunkSize = 1;
  
      /**
       * This creates an unbounded version. Setting the max objects will result in spooling on
       * subsequent puts.
       */
      public LRUMap()
      {
          list = new DoubleLinkedList<LRUElementDescriptor<K, V>>();
  
          // normal hshtable is faster for
          // sequential keys.
          map = new Hashtable<K, LRUElementDescriptor<K, V>>();
          // map = new ConcurrentHashMap();
      }
  
      /**
       * This sets the size limit.
       * <p>
       * @param maxObjects
      */
     public LRUMap( int maxObjects )
     {
         this();
         this.maxObjects = maxObjects;
     }
 
     /**
      * This simply returned the number of elements in the map.
      * <p>
      * @see java.util.Map#size()
      */
     public int size()
     {
         return map.size();
     }
 
     /**
      * This removes all the items. It clears the map and the double linked list.
      * <p>
      * @see java.util.Map#clear()
      */
     public void clear()
     {
         map.clear();
         list.removeAll();
     }
 
     /**
      * Returns true if the map is empty.
      * <p>
      * @see java.util.Map#isEmpty()
      */
     public boolean isEmpty()
     {
         return map.size() == 0;
     }
 
     /**
      * Returns true if the map contains an element for the supplied key.
      * <p>
      * @see java.util.Map#containsKey(java.lang.Object)
      */
     public boolean containsKey( Object key )
     {
         return map.containsKey( key );
     }
 
     /**
      * This is an expensive operation that determines if the object supplied is mapped to any key.
      * <p>
      * @see java.util.Map#containsValue(java.lang.Object)
      */
     public boolean containsValue( Object value )
     {
         return map.containsValue( value );
     }
 
     /**
      * @return map.values();
      */
     public Collection<V> values()
     {
         List<V> valueList = new ArrayList<V>(map.size());
 
         for (LRUElementDescriptor<K, V> value : map.values())
         {
             valueList.add(value.getPayload());
         }
 
         return valueList;
     }
 
     /**
      * @param source
      */
     public void putAll( Map<? extends K, ? extends V> source )
     {
         if ( source != null )
         {
             for (Map.Entry<? extends K, ? extends V> entry : source.entrySet())
             {
                 this.put( entry.getKey(), entry.getValue() );
             }
         }
     }
 
     /**
      * @param key
      * @return Object
      */
     public V get( Object key )
     {
         V retVal = null;
 
         if ( log.isDebugEnabled() )
         {
             log.debug( "getting item  for key " + key );
         }
 
         LRUElementDescriptor<K, V> me = map.get( key );
 
         if ( me != null )
         {
             hitCnt++;
             if ( log.isDebugEnabled() )
             {
                 log.debug( "LRUMap hit for " + key );
             }
 
             retVal = me.getPayload();
 
             list.makeFirst( me );
         }
         else
         {
             missCnt++;
             log.debug( "LRUMap miss for " + key );
         }
 
         // verifyCache();
         return retVal;
     }
 
     /**
      * This gets an element out of the map without adjusting it's posisiton in the LRU. In other
      * words, this does not count as being used. If the element is the last item in the list, it
      * will still be the last itme in the list.
      * <p>
      * @param key
      * @return Object
      */
     public V getQuiet( Object key )
     {
         V ce = null;
 
         LRUElementDescriptor<K, V> me = map.get( key );
         if ( me != null )
         {
             if ( log.isDebugEnabled() )
             {
                 log.debug( "LRUMap quiet hit for " + key );
             }
 
             ce = me.getPayload();
         }
         else if ( log.isDebugEnabled() )
         {
             log.debug( "LRUMap quiet miss for " + key );
         }
 
         return ce;
     }
 
     /**
      * @param key
      * @return Object removed
      */
     public V remove( Object key )
     {
         if ( log.isDebugEnabled() )
         {
             log.debug( "removing item for key: " + key );
         }
 
         // remove single item.
         LRUElementDescriptor<K, V> me = map.remove( key );
 
         if ( me != null )
         {
             list.remove( me );
             return me.getPayload();
         }
 
         return null;
     }
 
     /**
      * @param key
      * @param value
      * @return Object
      */
     public V put(K key, V value)
     {
         putCnt++;
 
         LRUElementDescriptor<K, V> old = null;
         synchronized ( this )
         {
             // TODO address double synchronization of addFirst, use write lock
             addFirst( key, value );
             // this must be synchronized
             old = map.put(list.getFirst().getKey(), list.getFirst());
 
             // If the node was the same as an existing node, remove it.
             if ( old != null && list.getFirst().getKey().equals(old.getKey()))
             {
                 list.remove( old );
             }
         }
 
         int size = map.size();
         // If the element limit is reached, we need to spool
 
         if ( this.maxObjects >= 0 && size > this.maxObjects )
         {
             if ( log.isDebugEnabled() )
             {
                 log.debug( "In memory limit reached, removing least recently used." );
             }
 
             // Write the last 'chunkSize' items to disk.
             int chunkSizeCorrected = Math.min( size, getChunkSize() );
 
             if ( log.isDebugEnabled() )
             {
                 log.debug( "About to remove the least recently used. map size: " + size + ", max objects: "
                     + this.maxObjects + ", items to spool: " + chunkSizeCorrected );
             }
 
             // The spool will put them in a disk event queue, so there is no
             // need to pre-queue the queuing. This would be a bit wasteful
             // and wouldn't save much time in this synchronous call.
 
             for ( int i = 0; i < chunkSizeCorrected; i++ )
             {
                 synchronized ( this )
                 {
                     if ( list.getLast() != null )
                     {
                         if (list.getLast() != null )
                         {
                             processRemovedLRU(list.getLast().getKey(), list.getLast().getPayload());
                             if ( !map.containsKey(list.getLast().getKey()))
                             {
                                 log.error( "update: map does not contain key: "
                                     + list.getLast().getKey() );
                                 verifyCache();
                             }
                             if ( map.remove( list.getLast().getKey() ) == null )
                             {
                                 log.warn( "update: remove failed for key: "
                                     + list.getLast().getKey() );
                                 verifyCache();
                             }
                         }
                         else
                         {
                             throw new Error( "update: last.ce is null!" );
                         }
                         list.removeLast();
                     }
                     else
                     {
                         verifyCache();
                         throw new Error( "update: last is null!" );
                     }
                 }
             }
 
             if ( log.isDebugEnabled() )
             {
                 log.debug( "update: After spool map size: " + map.size() );
             }
             if ( map.size() != dumpCacheSize() )
             {
                 log.error( "update: After spool, size mismatch: map.size() = " + map.size() + ", linked list size = "
                     + dumpCacheSize() );
             }
         }
 
         if ( old != null )
         {
             return old.getPayload();
         }
         return null;
     }
 
     /**
      * Adds a new node to the start of the link list.
      * <p>
      * @param key
      * @param val The feature to be added to the First
      */
     private synchronized void addFirst(K key, V val)
     {
         LRUElementDescriptor<K, V> me = new LRUElementDescriptor<K, V>(key, val);
         list.addFirst( me );
     }
 
     /**
      * Returns the size of the list.
      * <p>
      * @return int
      */
     private int dumpCacheSize()
     {
         return list.size();
     }
 
     /**
      * Dump the cache entries from first to list for debugging.
      */
     @SuppressWarnings("unchecked") // No generics for public fields
     public void dumpCacheEntries()
     {
         log.debug( "dumpingCacheEntries" );
         for ( LRUElementDescriptor<K, V> me = list.getFirst(); me != null; me = (LRUElementDescriptor<K, V>) me.next )
         {
             if ( log.isDebugEnabled() )
             {
                 log.debug( "dumpCacheEntries> key=" + me.getKey() + ", val=" + me.getPayload() );
             }
         }
     }
 
     /**
      * Dump the cache map for debugging.
      */
     public void dumpMap()
     {
         log.debug( "dumpingMap" );
         for (Map.Entry<K, LRUElementDescriptor<K, V>> e : map.entrySet())
         {
             LRUElementDescriptor<K, V> me = e.getValue();
             if ( log.isDebugEnabled() )
             {
                 log.debug( "dumpMap> key=" + e.getKey() + ", val=" + me.getPayload() );
             }
         }
     }
 
     /**
      * Checks to see if all the items that should be in the cache are. Checks consistency between
      * List and map.
      */
     @SuppressWarnings("unchecked") // No generics for public fields
     protected void verifyCache()
     {
         if ( !log.isDebugEnabled() )
         {
             return;
         }
 
         boolean found = false;
         log.debug( "verifycache: mapContains " + map.size() + " elements, linked list contains " + dumpCacheSize()
             + " elements" );
         log.debug( "verifycache: checking linked list by key " );
         for (LRUElementDescriptor<K, V> li = list.getFirst(); li != null; li = (LRUElementDescriptor<K, V>) li.next )
         {
             K key = li.getKey();
             if ( !map.containsKey( key ) )
             {
                 log.error( "verifycache: map does not contain key : " + li.getKey() );
                 log.error( "li.hashcode=" + li.getKey().hashCode() );
                 log.error( "key class=" + key.getClass() );
                 log.error( "key hashcode=" + key.hashCode() );
                 log.error( "key toString=" + key.toString() );
                 if ( key instanceof GroupAttrName )
                 {
                     GroupAttrName<?> name = (GroupAttrName<?>) key;
                     log.error( "GroupID hashcode=" + name.groupId.hashCode() );
                     log.error( "GroupID.class=" + name.groupId.getClass() );
                     log.error( "AttrName hashcode=" + name.attrName.hashCode() );
                     log.error( "AttrName.class=" + name.attrName.getClass() );
                 }
                 dumpMap();
             }
             else if ( map.get( li.getKey() ) == null )
             {
                 log.error( "verifycache: linked list retrieval returned null for key: " + li.getKey() );
             }
         }
 
         log.debug( "verifycache: checking linked list by value " );
         for (LRUElementDescriptor<K, V> li3 = list.getFirst(); li3 != null; li3 = (LRUElementDescriptor<K, V>) li3.next )
         {
             if ( map.containsValue( li3 ) == false )
             {
                 log.error( "verifycache: map does not contain value : " + li3 );
                 dumpMap();
             }
         }
 
         log.debug( "verifycache: checking via keysets!" );
         for (Iterator<K> itr2 = map.keySet().iterator(); itr2.hasNext(); )
         {
             found = false;
             Serializable val = null;
             try
             {
                 val = (Serializable) itr2.next();
             }
             catch ( NoSuchElementException nse )
             {
                 log.error( "verifycache: no such element exception" );
                 continue;
             }
 
             for (LRUElementDescriptor<K, V> li2 = list.getFirst(); li2 != null; li2 = (LRUElementDescriptor<K, V>) li2.next )
             {
                 if ( val.equals( li2.getKey() ) )
                 {
                     found = true;
                     break;
                 }
             }
             if ( !found )
             {
                 log.error( "verifycache: key not found in list : " + val );
                 dumpCacheEntries();
                 if ( map.containsKey( val ) )
                 {
                     log.error( "verifycache: map contains key" );
                 }
                 else
                 {
                     log.error( "verifycache: map does NOT contain key, what the HECK!" );
                 }
             }
         }
     }
 
     /**
      * Logs an error is an element that should be in the cache is not.
      * <p>
      * @param key
      */
     @SuppressWarnings("unchecked") // No generics for public fields
     protected void verifyCache( Object key )
     {
         if ( !log.isDebugEnabled() )
         {
             return;
         }
 
         boolean found = false;
 
         // go through the linked list looking for the key
         for (LRUElementDescriptor<K, V> li = list.getFirst(); li != null; li = (LRUElementDescriptor<K, V>) li.next )
         {
             if ( li.getKey() == key )
             {
                 found = true;
                 log.debug( "verifycache(key) key match: " + key );
                 break;
             }
         }
         if ( !found )
         {
             log.error( "verifycache(key), couldn't find key! : " + key );
         }
     }
 
     /**
      * This is called when an item is removed from the LRU. We just log some information.
      * <p>
      * Children can implement this method for special behavior.
      * @param key
      * @param value
      */
     protected void processRemovedLRU(K key, V value )
     {
         if ( log.isDebugEnabled() )
         {
             log.debug( "Removing key: [" + key + "] from LRUMap store, value = [" + value + "]" );
             log.debug( "LRUMap store size: '" + this.size() + "'." );
         }
     }
 
     /**
      * The chunk size is the number of items to remove when the max is reached. By default it is 1.
      * <p>
      * @param chunkSize The chunkSize to set.
      */
     public void setChunkSize( int chunkSize )
     {
         this.chunkSize = chunkSize;
     }
 
     /**
      * @return Returns the chunkSize.
      */
     public int getChunkSize()
     {
         return chunkSize;
     }
 
     /**
      * @return IStats
      */
     public IStats getStatistics()
     {
         IStats stats = new Stats();
         stats.setTypeName( "LRUMap" );
 
         ArrayList<IStatElement> elems = new ArrayList<IStatElement>();
 
         IStatElement se = null;
 
         se = new StatElement();
         se.setName( "List Size" );
         se.setData( "" + list.size() );
         elems.add( se );
 
         se = new StatElement();
         se.setName( "Map Size" );
         se.setData( "" + map.size() );
         elems.add( se );
 
         se = new StatElement();
         se.setName( "Put Count" );
         se.setData( "" + putCnt );
         elems.add( se );
 
         se = new StatElement();
         se.setName( "Hit Count" );
         se.setData( "" + hitCnt );
         elems.add( se );
 
         se = new StatElement();
         se.setName( "Miss Count" );
         se.setData( "" + missCnt );
         elems.add( se );
 
         // get an array and put them in the Stats object
         IStatElement[] ses = elems.toArray( new StatElement[0] );
         stats.setStatElements( ses );
 
         return stats;
     }
 
     /**
      * This returns a set of entries. Our LRUMapEntry is used since the value stored in the
      * underlying map is a node in the double linked list. We wouldn't want to return this to the
      * client, so we construct a new entry with the payload of the node.
      * <p>
      * TODO we should return out own set wrapper, so we can avoid the extra object creation if it
      * isn't necessary.
      * <p>
      * @see java.util.Map#entrySet()
      */
     public synchronized Set<Map.Entry<K, V>> entrySet()
     {
         // todo, we should return a defensive copy
         Set<Map.Entry<K, LRUElementDescriptor<K, V>>> entries = map.entrySet();
 
         Set<Map.Entry<K, V>> unWrapped = new HashSet<Map.Entry<K, V>>();
 
         for (Map.Entry<K, LRUElementDescriptor<K, V>> pre : entries )
         {
             Map.Entry<K, V> post = new LRUMapEntry<K, V>(pre.getKey(), pre.getValue().getPayload());
             unWrapped.add(post);
         }
 
         return unWrapped;
     }
 
     /**
      * @return map.keySet();
      */
     public Set<K> keySet()
     {
         // TODO fix this, it needs to return the keys inside the wrappers.
         return map.keySet();
     }
 
     /**
      * @return the max objects size.
      */
     public int getMaxObjects()
     {
         return maxObjects;
     }
 }