/*
    *  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.core.session;
  
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Queue;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentLinkedQueue;
  
  import org.apache.mina.core.write.WriteRequest;
  import org.apache.mina.core.write.WriteRequestQueue;
  
  /**
   * The default {@link IoSessionDataStructureFactory} implementation
   * that creates a new {@link HashMap}-based {@link IoSessionAttributeMap}
   * instance and a new synchronized {@link ConcurrentLinkedQueue} instance per
   * {@link IoSession}.
   * 
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   */
  public class DefaultIoSessionDataStructureFactory implements IoSessionDataStructureFactory {
      /**
       * {@inheritDoc}
       */
      @Override
      public IoSessionAttributeMap getAttributeMap(IoSession session) throws Exception {
          return new DefaultIoSessionAttributeMap();
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public WriteRequestQueue getWriteRequestQueue(IoSession session) throws Exception {
          return new DefaultWriteRequestQueue();
      }
  
      private static class DefaultIoSessionAttributeMap implements IoSessionAttributeMap {
          private final ConcurrentHashMap<Object, Object> attributes = new ConcurrentHashMap<>(4);
  
          /**
           * Default constructor
           */
          public DefaultIoSessionAttributeMap() {
              super();
          }
  
          /**
           * {@inheritDoc}
           */
          @Override
          public Object getAttribute(IoSession session, Object key, Object defaultValue) {
              if (key == null) {
                  throw new IllegalArgumentException("key");
              }
  
              if (defaultValue == null) {
                  return attributes.get(key);
              }
  
              Object object = attributes.putIfAbsent(key, defaultValue);
  
              if (object == null) {
                  return defaultValue;
              } else {
                  return object;
              }
          }
  
          /**
           * {@inheritDoc}
           */
          @Override
          public Object setAttribute(IoSession session, Object key, Object value) {
              if (key == null) {
                  throw new IllegalArgumentException("key");
              }
  
              if (value == null) {
                  return attributes.remove(key);
             }
 
             return attributes.put(key, value);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public Object setAttributeIfAbsent(IoSession session, Object key, Object value) {
             if (key == null) {
                 throw new IllegalArgumentException("key");
             }
 
             if (value == null) {
                 return null;
             }
 
             return attributes.putIfAbsent(key, value);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public Object removeAttribute(IoSession session, Object key) {
             if (key == null) {
                 throw new IllegalArgumentException("key");
             }
 
             return attributes.remove(key);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean removeAttribute(IoSession session, Object key, Object value) {
             if (key == null) {
                 throw new IllegalArgumentException("key");
             }
 
             if (value == null) {
                 return false;
             }
 
             try {
                 return attributes.remove(key, value);
             } catch (NullPointerException e) {
                 return false;
             }
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean replaceAttribute(IoSession session, Object key, Object oldValue, Object newValue) {
             try {
                 return attributes.replace(key, oldValue, newValue);
             } catch (NullPointerException e) {
             }
 
             return false;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean containsAttribute(IoSession session, Object key) {
             return attributes.containsKey(key);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public Set<Object> getAttributeKeys(IoSession session) {
             synchronized (attributes) {
                 return new HashSet<>(attributes.keySet());
             }
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void dispose(IoSession session) throws Exception {
             // Do nothing
         }
     }
 
     private static class DefaultWriteRequestQueue implements WriteRequestQueue {
         /** A queue to store incoming write requests */
         private final Queue<WriteRequest> q = new ConcurrentLinkedQueue<>();
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void dispose(IoSession session) {
             // Do nothing
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void clear(IoSession session) {
             q.clear();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean isEmpty(IoSession session) {
             return q.isEmpty();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void offer(IoSession session, WriteRequest writeRequest) {
             q.offer(writeRequest);
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public WriteRequest poll(IoSession session) {
             WriteRequest answer = q.poll();
 
             if (answer == AbstractIoSession.CLOSE_REQUEST) {
                 session.closeNow();
                 dispose(session);
                 answer = null;
             }
 
             return answer;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public String toString() {
             return q.toString();
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public int size() {
             return q.size();
         }
     }
 }