/*
    *  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.mina.util;
  
  import java.util.Collection;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.locks.ReadWriteLock;
  import java.util.concurrent.locks.ReentrantReadWriteLock;
  
  /**
   * A map with expiration.  This class contains a worker thread that will 
   * periodically check this class in order to determine if any objects 
   * should be removed based on the provided time-to-live value.
   *
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   */
  public class ExpiringMap<K, V> implements Map<K, V> {
      
      /**
       * The default value, 60
       */
      public static final int DEFAULT_TIME_TO_LIVE = 60;
  
      /**
       * The default value, 1
       */
      public static final int DEFAULT_EXPIRATION_INTERVAL = 1;
  
      private static volatile int expirerCount = 1;
  
      private final ConcurrentHashMap<K, ExpiringObject> delegate;
  
      private final CopyOnWriteArrayList<ExpirationListener<V>> expirationListeners;
  
      private final Expirer expirer;
  
      /**
       * Creates a new instance of ExpiringMap using the default values 
       * DEFAULT_TIME_TO_LIVE and DEFAULT_EXPIRATION_INTERVAL
       *
       */
      public ExpiringMap() {
          this(DEFAULT_TIME_TO_LIVE, DEFAULT_EXPIRATION_INTERVAL);
      }
  
      /**
       * Creates a new instance of ExpiringMap using the supplied 
       * time-to-live value and the default value for DEFAULT_EXPIRATION_INTERVAL
       *
       * @param timeToLive
       *  The time-to-live value (seconds)
       */
      public ExpiringMap(int timeToLive) {
          this(timeToLive, DEFAULT_EXPIRATION_INTERVAL);
      }
  
      /**
       * Creates a new instance of ExpiringMap using the supplied values and 
       * a {@link ConcurrentHashMap} for the internal data structure.
       *
       * @param timeToLive
       *  The time-to-live value (seconds)
       * @param expirationInterval
       *  The time between checks to see if a value should be removed (seconds)
       */
      public ExpiringMap(int timeToLive, int expirationInterval) {
          this(new ConcurrentHashMap<K, ExpiringObject>(),
                  new CopyOnWriteArrayList<ExpirationListener<V>>(), timeToLive,
                  expirationInterval);
      }
  
      private ExpiringMap(ConcurrentHashMap<K, ExpiringObject> delegate,
              CopyOnWriteArrayList<ExpirationListener<V>> expirationListeners,
              int timeToLive, int expirationInterval) {
          this.delegate = delegate;
          this.expirationListeners = expirationListeners;
  
          this.expirer = new Expirer();
          expirer.setTimeToLive(timeToLive);
         expirer.setExpirationInterval(expirationInterval);
     }
 
     public V put(K key, V value) {
         ExpiringObject answer = delegate.put(key, new ExpiringObject(key,
                 value, System.currentTimeMillis()));
         if (answer == null) {
             return null;
         }
 
         return answer.getValue();
     }
 
     public V get(Object key) {
         ExpiringObject object = delegate.get(key);
 
         if (object != null) {
             object.setLastAccessTime(System.currentTimeMillis());
 
             return object.getValue();
         }
 
         return null;
     }
 
     public V remove(Object key) {
         ExpiringObject answer = delegate.remove(key);
         if (answer == null) {
             return null;
         }
 
         return answer.getValue();
     }
 
     public boolean containsKey(Object key) {
         return delegate.containsKey(key);
     }
 
     public boolean containsValue(Object value) {
         return delegate.containsValue(value);
     }
 
     public int size() {
         return delegate.size();
     }
 
     public boolean isEmpty() {
         return delegate.isEmpty();
     }
 
     public void clear() {
         delegate.clear();
     }
 
     @Override
     public int hashCode() {
         return delegate.hashCode();
     }
 
     public Set<K> keySet() {
         return delegate.keySet();
     }
 
     @Override
     public boolean equals(Object obj) {
         return delegate.equals(obj);
     }
 
     public void putAll(Map<? extends K, ? extends V> inMap) {
         for (Entry<? extends K, ? extends V> e : inMap.entrySet()) {
             this.put(e.getKey(), e.getValue());
         }
     }
 
     public Collection<V> values() {
         throw new UnsupportedOperationException();
     }
 
     public Set<Map.Entry<K, V>> entrySet() {
         throw new UnsupportedOperationException();
     }
 
     public void addExpirationListener(ExpirationListener<V> listener) {
         expirationListeners.add(listener);
     }
 
     public void removeExpirationListener(
             ExpirationListener<V> listener) {
         expirationListeners.remove(listener);
     }
 
     public Expirer getExpirer() {
         return expirer;
     }
 
     public int getExpirationInterval() {
         return expirer.getExpirationInterval();
     }
 
     public int getTimeToLive() {
         return expirer.getTimeToLive();
     }
 
     public void setExpirationInterval(int expirationInterval) {
         expirer.setExpirationInterval(expirationInterval);
     }
 
     public void setTimeToLive(int timeToLive) {
         expirer.setTimeToLive(timeToLive);
     }
 
     private class ExpiringObject {
         private K key;
 
         private V value;
 
         private long lastAccessTime;
 
         private final ReadWriteLock lastAccessTimeLock = new ReentrantReadWriteLock();
 
         ExpiringObject(K key, V value, long lastAccessTime) {
             if (value == null) {
                 throw new IllegalArgumentException(
                         "An expiring object cannot be null.");
             }
 
             this.key = key;
             this.value = value;
             this.lastAccessTime = lastAccessTime;
         }
 
         public long getLastAccessTime() {
             lastAccessTimeLock.readLock().lock();
 
             try {
                 return lastAccessTime;
             } finally {
                 lastAccessTimeLock.readLock().unlock();
             }
         }
 
         public void setLastAccessTime(long lastAccessTime) {
             lastAccessTimeLock.writeLock().lock();
 
             try {
                 this.lastAccessTime = lastAccessTime;
             } finally {
                 lastAccessTimeLock.writeLock().unlock();
             }
         }
 
         public K getKey() {
             return key;
         }
 
         public V getValue() {
             return value;
         }
 
         @Override
         public boolean equals(Object obj) {
             return value.equals(obj);
         }
 
         @Override
         public int hashCode() {
             return value.hashCode();
         }
     }
 
     /**
      * A Thread that monitors an {@link ExpiringMap} and will remove
      * elements that have passed the threshold.
      *
      */ 
     public class Expirer implements Runnable {
         private final ReadWriteLock stateLock = new ReentrantReadWriteLock();
 
         private long timeToLiveMillis;
 
         private long expirationIntervalMillis;
 
         private boolean running = false;
 
         private final Thread expirerThread;
 
         /**
          * Creates a new instance of Expirer.  
          *
          */
         public Expirer() {
             expirerThread = new Thread(this, "ExpiringMapExpirer-"
                     + expirerCount++);
             expirerThread.setDaemon(true);
         }
 
         public void run() {
             while (running) {
                 processExpires();
 
                 try {
                     Thread.sleep(expirationIntervalMillis);
                 } catch (InterruptedException e) {
                     // Do nothing
                 }
             }
         }
 
         private void processExpires() {
             long timeNow = System.currentTimeMillis();
 
             for (ExpiringObject o : delegate.values()) {
 
                 if (timeToLiveMillis <= 0) {
                     continue;
                 }
 
                 long timeIdle = timeNow - o.getLastAccessTime();
 
                 if (timeIdle >= timeToLiveMillis) {
                     delegate.remove(o.getKey());
 
                     for (ExpirationListener<V> listener : expirationListeners) {
                         listener.expired(o.getValue());
                     }
                 }
             }
         }
 
         /**
          * Kick off this thread which will look for old objects and remove them.
          *
          */
         public void startExpiring() {
             stateLock.writeLock().lock();
 
             try {
                 if (!running) {
                     running = true;
                     expirerThread.start();
                 }
             } finally {
                 stateLock.writeLock().unlock();
             }
         }
 
         /**
          * If this thread has not started, then start it.  
          * Otherwise just return;
          */
         public void startExpiringIfNotStarted() {
             stateLock.readLock().lock();
             try {
                 if (running) {
                     return;
                 }
             } finally {
                 stateLock.readLock().unlock();
             }
 
             stateLock.writeLock().lock();
             try {
                 if (!running) {
                     running = true;
                     expirerThread.start();
                 }
             } finally {
                 stateLock.writeLock().unlock();
             }
         }
 
         /**
          * Stop the thread from monitoring the map.
          */
         public void stopExpiring() {
             stateLock.writeLock().lock();
 
             try {
                 if (running) {
                     running = false;
                     expirerThread.interrupt();
                 }
             } finally {
                 stateLock.writeLock().unlock();
             }
         }
 
         /**
          * Checks to see if the thread is running
          *
          * @return
          *  If the thread is running, true.  Otherwise false.
          */
         public boolean isRunning() {
             stateLock.readLock().lock();
 
             try {
                 return running;
             } finally {
                 stateLock.readLock().unlock();
             }
         }
 
         /**
          * Returns the Time-to-live value.
          *
          * @return
          *  The time-to-live (seconds)
          */
         public int getTimeToLive() {
             stateLock.readLock().lock();
 
             try {
                 return (int) timeToLiveMillis / 1000;
             } finally {
                 stateLock.readLock().unlock();
             }
         }
 
         /**
          * Update the value for the time-to-live
          *
          * @param timeToLive
          *  The time-to-live (seconds)
          */
         public void setTimeToLive(long timeToLive) {
             stateLock.writeLock().lock();
 
             try {
                 this.timeToLiveMillis = timeToLive * 1000;
             } finally {
                 stateLock.writeLock().unlock();
             }
         }
 
         /**
          * Get the interval in which an object will live in the map before
          * it is removed.
          *
          * @return
          *  The time in seconds.
          */
         public int getExpirationInterval() {
             stateLock.readLock().lock();
 
             try {
                 return (int) expirationIntervalMillis / 1000;
             } finally {
                 stateLock.readLock().unlock();
             }
         }
 
         /**
          * Set the interval in which an object will live in the map before
          * it is removed.
          *
          * @param expirationInterval
          *  The time in seconds
          */
         public void setExpirationInterval(long expirationInterval) {
             stateLock.writeLock().lock();
 
             try {
                 this.expirationIntervalMillis = expirationInterval * 1000;
             } finally {
                 stateLock.writeLock().unlock();
             }
         }
     }
 }