/*
    * 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.
   */
  package org.apache.commons.jcs3.jcache;
  
  import javax.cache.Cache;
  import javax.cache.CacheManager;
  import javax.cache.configuration.CacheEntryListenerConfiguration;
  import javax.cache.configuration.CompleteConfiguration;
  import javax.cache.configuration.Configuration;
  import javax.cache.integration.CompletionListener;
  import javax.cache.processor.EntryProcessor;
  import javax.cache.processor.EntryProcessorException;
  import javax.cache.processor.EntryProcessorResult;
  
  import static org.apache.commons.jcs3.jcache.Asserts.assertNotNull;
  
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.Map;
  import java.util.Set;
  
  // kind of transactional view for a Cache<K, V>, to use with EntryProcessor
  public class TempStateCacheView<K, V> implements Cache<K, V>
  {
      private final JCSCache<K, V> cache;
      private final Map<K, V> put = new HashMap<>();
      private final Collection<K> remove = new LinkedList<>();
      private boolean removeAll;
      private boolean clear;
  
      public TempStateCacheView(final JCSCache<K, V> entries)
      {
          this.cache = entries;
      }
  
      @Override
      public V get(final K key)
      {
          if (ignoreKey(key))
          {
              return null;
          }
  
          final V v = put.get(key);
          if (v != null)
          {
              return v;
          }
  
          // for an EntryProcessor we already incremented stats - to enhance
          // surely
          if (cache.getConfiguration(CompleteConfiguration.class).isStatisticsEnabled())
          {
              final Statistics statistics = cache.getStatistics();
              if (cache.containsKey(key))
              {
                  statistics.increaseHits(-1);
              }
              else
              {
                  statistics.increaseMisses(-1);
              }
          }
          return cache.get(key);
      }
  
      private boolean ignoreKey(final K key)
      {
          return removeAll || clear || remove.contains(key);
      }
  
      @Override
      public Map<K, V> getAll(final Set<? extends K> keys)
      {
          final Map<K, V> v = new HashMap<>(keys.size());
          final Set<K> missing = new HashSet<>();
          for (final K k : keys)
          {
              final V value = put.get(k);
              if (value != null)
             {
                 v.put(k, value);
             }
             else if (!ignoreKey(k))
             {
                 missing.add(k);
             }
         }
         if (!missing.isEmpty())
         {
             v.putAll(cache.getAll(missing));
         }
         return v;
     }
 
     @Override
     public boolean containsKey(final K key)
     {
         return !ignoreKey(key) && (put.containsKey(key) || cache.containsKey(key));
     }
 
     @Override
     public void loadAll(final Set<? extends K> keys, final boolean replaceExistingValues, final CompletionListener completionListener)
     {
         cache.loadAll(keys, replaceExistingValues, completionListener);
     }
 
     @Override
     public void put(final K key, final V value)
     {
         assertNotNull(key, "key");
         assertNotNull(value, "value");
         put.put(key, value);
         remove.remove(key);
     }
 
     @Override
     public V getAndPut(final K key, final V value)
     {
         final V v = get(key);
         put(key, value);
         return v;
     }
 
     @Override
     public void putAll(final Map<? extends K, ? extends V> map)
     {
         put.putAll(map);
         for (final K k : map.keySet())
         {
             remove.remove(k);
         }
     }
 
     @Override
     public boolean putIfAbsent(final K key, final V value)
     {
         if (!put.containsKey(key))
         {
             put.put(key, value);
             remove.remove(key);
             return true;
         }
         return false;
     }
 
     @Override
     public boolean remove(final K key)
     {
         final boolean noop = put.containsKey(key);
         put.remove(key);
         if (!ignoreKey(key))
         {
             if (!noop)
             {
                 remove.add(key);
             }
             return true;
         }
         return false;
     }
 
     @Override
     public boolean remove(final K key, final V oldValue)
     {
         put.remove(key);
         if (!ignoreKey(key) && oldValue.equals(cache.get(key)))
         {
             remove.add(key);
             return true;
         }
         return false;
     }
 
     @Override
     public V getAndRemove(final K key)
     {
         final V v = get(key);
         remove.add(key);
         put.remove(key);
         return v;
     }
 
     @Override
     public boolean replace(final K key, final V oldValue, final V newValue)
     {
         if (oldValue.equals(get(key)))
         {
             put(key, newValue);
             return true;
         }
         return false;
     }
 
     @Override
     public boolean replace(final K key, final V value)
     {
         if (containsKey(key))
         {
             remove(key);
             return true;
         }
         return false;
     }
 
     @Override
     public V getAndReplace(final K key, final V value)
     {
         if (containsKey(key))
         {
             final V oldValue = get(key);
             put(key, value);
             return oldValue;
         }
         return null;
     }
 
     @Override
     public void removeAll(final Set<? extends K> keys)
     {
         remove.addAll(keys);
         for (final K k : keys)
         {
             put.remove(k);
         }
     }
 
     @Override
     public void removeAll()
     {
         removeAll = true;
         put.clear();
         remove.clear();
     }
 
     @Override
     public void clear()
     {
         clear = true;
         put.clear();
         remove.clear();
     }
 
     @Override
     public <C extends Configuration<K, V>> C getConfiguration(final Class<C> clazz)
     {
         return cache.getConfiguration(clazz);
     }
 
     @Override
     public <T> T invoke(final K key, final EntryProcessor<K, V, T> entryProcessor, final Object... arguments) throws EntryProcessorException
     {
         return cache.invoke(key, entryProcessor, arguments);
     }
 
     @Override
     public <T> Map<K, EntryProcessorResult<T>> invokeAll(final Set<? extends K> keys, final EntryProcessor<K, V, T> entryProcessor,
             final Object... arguments)
     {
         return cache.invokeAll(keys, entryProcessor, arguments);
     }
 
     @Override
     public String getName()
     {
         return cache.getName();
     }
 
     @Override
     public CacheManager getCacheManager()
     {
         return cache.getCacheManager();
     }
 
     @Override
     public void close()
     {
         cache.close();
     }
 
     @Override
     public boolean isClosed()
     {
         return cache.isClosed();
     }
 
     @Override
     public <T> T unwrap(final Class<T> clazz)
     {
         return cache.unwrap(clazz);
     }
 
     @Override
     public void registerCacheEntryListener(final CacheEntryListenerConfiguration<K, V> cacheEntryListenerConfiguration)
     {
         cache.registerCacheEntryListener(cacheEntryListenerConfiguration);
     }
 
     @Override
     public void deregisterCacheEntryListener(final CacheEntryListenerConfiguration<K, V> cacheEntryListenerConfiguration)
     {
         cache.deregisterCacheEntryListener(cacheEntryListenerConfiguration);
     }
 
     @Override
     public Iterator<Entry<K, V>> iterator()
     {
         return cache.iterator();
     }
 
     public void merge()
     {
         if (removeAll)
         {
             cache.removeAll();
         }
         if (clear)
         {
             cache.clear();
         }
 
         for (final Map.Entry<K, V> entry : put.entrySet())
         {
             cache.put(entry.getKey(), entry.getValue());
         }
         put.clear();
         for (final K entry : remove)
         {
             cache.remove(entry);
         }
         remove.clear();
     }
 }