/*
    *  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.future;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.mina.core.polling.AbstractPollingIoProcessor;
  import org.apache.mina.core.service.IoProcessor;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.util.ExceptionMonitor;
  
  
  /**
   * A default implementation of {@link IoFuture} associated with
   * an {@link IoSession}.
   * 
   * @author The Apache MINA Project (dev@mina.apache.org)
   */
  public class DefaultIoFuture implements IoFuture {
  
      /** A number of seconds to wait between two deadlock controls ( 5 seconds ) */
      private static final long DEAD_LOCK_CHECK_INTERVAL = 5000L;
  
      /** The associated session */
      private final IoSession session;
      
      /** A lock used by the wait() method */
      private final Object lock;
      private IoFutureListener<?> firstListener;
      private List<IoFutureListener<?>> otherListeners;
      private Object result;
      private boolean ready;
      private int waiters;
  
      /**
       * Creates a new instance associated with an {@link IoSession}.
       *
       * @param session an {@link IoSession} which is associated with this future
       */
      public DefaultIoFuture(IoSession session) {
          this.session = session;
          this.lock = this;
      }
  
      /**
       * {@inheritDoc}
       */
      public IoSession getSession() {
          return session;
      }
  
      /**
       * @deprecated Replaced with {@link #awaitUninterruptibly()}.
       */
      @Deprecated
      public void join() {
          awaitUninterruptibly();
      }
  
      /**
       * @deprecated Replaced with {@link #awaitUninterruptibly(long)}.
       */
      @Deprecated
      public boolean join(long timeoutMillis) {
          return awaitUninterruptibly(timeoutMillis);
      }
  
      /**
       * {@inheritDoc}
       */
      public IoFuture await() throws InterruptedException {
          synchronized (lock) {
              while (!ready) {
                  waiters++;
                  try {
                      // Wait for a notify, or if no notify is called,
                      // assume that we have a deadlock and exit the 
                      // loop to check for a potential deadlock.
                      lock.wait(DEAD_LOCK_CHECK_INTERVAL);
                  } finally {
                     waiters--;
                     if (!ready) {
                         checkDeadLock();
                     }
                 }
             }
         }
         return this;
     }
 
     /**
      * {@inheritDoc}
      */
     public boolean await(long timeout, TimeUnit unit)
             throws InterruptedException {
         return await(unit.toMillis(timeout));
     }
 
     /**
      * {@inheritDoc}
      */
     public boolean await(long timeoutMillis) throws InterruptedException {
         return await0(timeoutMillis, true);
     }
 
     /**
      * {@inheritDoc}
      */
     public IoFuture awaitUninterruptibly() {
         try {
             await0(Long.MAX_VALUE, false);
         } catch ( InterruptedException ie) {
             // Do nothing : this catch is just mandatory by contract
         }
         
         return this;
     }
 
     /**
      * {@inheritDoc}
      */
     public boolean awaitUninterruptibly(long timeout, TimeUnit unit) {
         return awaitUninterruptibly(unit.toMillis(timeout));
     }
 
     /**
      * {@inheritDoc}
      */
     public boolean awaitUninterruptibly(long timeoutMillis) {
         try {
             return await0(timeoutMillis, false);
         } catch (InterruptedException e) {
             throw new InternalError();
         }
     }
 
     /**
      * Wait for the Future to be ready. If the requested delay is 0 or 
      * negative, this method immediately returns the value of the 
      * 'ready' flag. 
      * Every 5 second, the wait will be suspended to be able to check if 
      * there is a deadlock or not.
      * 
      * @param timeoutMillis The delay we will wait for the Future to be ready
      * @param interruptable Tells if the wait can be interrupted or not
      * @return <code>true</code> if the Future is ready
      * @throws InterruptedException If the thread has been interrupted
      * when it's not allowed.
      */
     private boolean await0(long timeoutMillis, boolean interruptable) throws InterruptedException {
         long endTime = System.currentTimeMillis() + timeoutMillis;
 
         synchronized (lock) {
             if (ready) {
                 return ready;
             } else if (timeoutMillis <= 0) {
                 return ready;
             }
 
             waiters++;
             try {
                 for (;;) {
                     try {
                         long timeOut = Math.min(timeoutMillis, DEAD_LOCK_CHECK_INTERVAL);
                         lock.wait(timeOut);
                     } catch (InterruptedException e) {
                         if (interruptable) {
                             throw e;
                         }
                     }
 
                     if (ready) {
                         return true;
                     } else {
                         if (endTime < System.currentTimeMillis()) {
                             return ready;
                         }
                     }
                 }
             } finally {
                 waiters--;
                 if (!ready) {
                     checkDeadLock();
                 }
             }
         }
     }
 
     
     /**
      * 
      * TODO checkDeadLock.
      *
      */
     private void checkDeadLock() {
         // Only read / write / connect / write future can cause dead lock. 
         if (!(this instanceof CloseFuture || this instanceof WriteFuture ||
               this instanceof ReadFuture || this instanceof ConnectFuture)) {
             return;
         }
         
         // Get the current thread stackTrace. 
         // Using Thread.currentThread().getStackTrace() is the best solution,
         // even if slightly less efficient than doing a new Exception().getStackTrace(),
         // as internally, it does exactly the same thing. The advantage of using
         // this solution is that we may benefit some improvement with some
         // future versions of Java.
         StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
 
         // Simple and quick check.
         for (StackTraceElement s: stackTrace) {
             if (AbstractPollingIoProcessor.class.getName().equals(s.getClassName())) {
                 IllegalStateException e = new IllegalStateException( "t" );
                 e.getStackTrace();
                 throw new IllegalStateException(
                     "DEAD LOCK: " + IoFuture.class.getSimpleName() +
                     ".await() was invoked from an I/O processor thread.  " +
                     "Please use " + IoFutureListener.class.getSimpleName() +
                     " or configure a proper thread model alternatively.");
             }
         }
 
         // And then more precisely.
         for (StackTraceElement s: stackTrace) {
             try {
                 Class<?> cls = DefaultIoFuture.class.getClassLoader().loadClass(s.getClassName());
                 if (IoProcessor.class.isAssignableFrom(cls)) {
                     throw new IllegalStateException(
                         "DEAD LOCK: " + IoFuture.class.getSimpleName() +
                         ".await() was invoked from an I/O processor thread.  " +
                         "Please use " + IoFutureListener.class.getSimpleName() +
                         " or configure a proper thread model alternatively.");
                 }
             } catch (Exception cnfe) {
                 // Ignore
             }
         }
     }
 
     /**
      * {@inheritDoc}
      */
     public boolean isDone() {
         synchronized (lock) {
             return ready;
         }
     }
 
     /**
      * Sets the result of the asynchronous operation, and mark it as finished.
      */
     public void setValue(Object newValue) {
         synchronized (lock) {
             // Allow only once.
             if (ready) {
                 return;
             }
 
             result = newValue;
             ready = true;
             if (waiters > 0) {
                 lock.notifyAll();
             }
         }
 
         notifyListeners();
     }
 
     /**
      * Returns the result of the asynchronous operation.
      */
     protected Object getValue() {
         synchronized (lock) {
             return result;
         }
     }
 
     /**
      * {@inheritDoc}
      */
     public IoFuture addListener(IoFutureListener<?> listener) {
         if (listener == null) {
             throw new NullPointerException("listener");
         }
 
         boolean notifyNow = false;
         synchronized (lock) {
             if (ready) {
                 notifyNow = true;
             } else {
                 if (firstListener == null) {
                     firstListener = listener;
                 } else {
                     if (otherListeners == null) {
                         otherListeners = new ArrayList<IoFutureListener<?>>(1);
                     }
                     otherListeners.add(listener);
                 }
             }
         }
 
         if (notifyNow) {
             notifyListener(listener);
         }
         return this;
     }
 
     /**
      * {@inheritDoc}
      */
     public IoFuture removeListener(IoFutureListener<?> listener) {
         if (listener == null) {
             throw new NullPointerException("listener");
         }
 
         synchronized (lock) {
             if (!ready) {
                 if (listener == firstListener) {
                     if (otherListeners != null && !otherListeners.isEmpty()) {
                         firstListener = otherListeners.remove(0);
                     } else {
                         firstListener = null;
                     }
                 } else if (otherListeners != null) {
                     otherListeners.remove(listener);
                 }
             }
         }
 
         return this;
     }
 
     private void notifyListeners() {
         // There won't be any visibility problem or concurrent modification
         // because 'ready' flag will be checked against both addListener and
         // removeListener calls.
         if (firstListener != null) {
             notifyListener(firstListener);
             firstListener = null;
 
             if (otherListeners != null) {
                 for (IoFutureListener<?> l : otherListeners) {
                     notifyListener(l);
                 }
                 otherListeners = null;
             }
         }
     }
 
     @SuppressWarnings("unchecked")
     private void notifyListener(IoFutureListener l) {
         try {
             l.operationComplete(this);
         } catch (Throwable t) {
             ExceptionMonitor.getInstance().exceptionCaught(t);
         }
     }
 }