/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.core5.reactor;
  
  import java.net.SocketAddress;
  import java.nio.channels.ByteChannel;
  import java.util.concurrent.locks.Lock;
  
  import org.apache.hc.core5.annotation.Internal;
  import org.apache.hc.core5.http.SocketModalCloseable;
  import org.apache.hc.core5.util.Identifiable;
  import org.apache.hc.core5.util.Timeout;
  
  /**
   * IOSession interface represents a sequence of logically related data exchanges
   * between two end points.
   * <p>
   * The channel associated with implementations of this interface can be used to
   * read data from and write data to the session.
   * <p>
   * I/O sessions are not bound to an execution thread, therefore one cannot use
   * the context of the thread to store a session's state. All details about
   * a particular session must be stored within the session itself, usually
   * using execution context associated with it.
   * <p>
   * Implementations of this interface are expected to be threading safe.
   *
   * @since 4.0
   */
  @Internal
  public interface IOSession extends ByteChannel, SocketModalCloseable, Identifiable {
  
      /**
       * This enum represents a set of states I/O session transitions through
       * during its life-span.
       */
      enum Status {
  
          ACTIVE,
          CLOSING,
          CLOSED
  
      }
  
      /**
       * Returns event handler associated with the session.
       *
       * @since 5.0
       */
      IOEventHandler getHandler();
  
      /**
       * Upgrades event handler associated with the session.
       *
       * @since 5.0
       */
      void upgrade(IOEventHandler handler);
  
      /**
       * Returns session lock that should be used by I/O event handlers
       * to synchronize access to the session.
       *
       * @since 5.0
       */
      Lock getLock();
  
      /**
       * Inserts {@link Command} at the end of the command queue.
       *
       * @since 5.0
       */
      void enqueue(Command command, Command.Priority priority);
  
      /**
      * Tests if there enqueued commands pending execution.
      *
      * @since 5.0
      */
     boolean hasCommands();
 
     /**
      * Removes first {@link Command} from the command queue if available.
      *
      * @since 5.0
      */
     Command poll();
 
     /**
      * Returns the underlying I/O channel associated with this session.
      *
      * @return the I/O channel.
      */
     ByteChannel channel();
 
     /**
      * Returns address of the remote peer.
      *
      * @return socket address.
      */
     SocketAddress getRemoteAddress();
 
     /**
      * Returns local address.
      *
      * @return socket address.
      */
     SocketAddress getLocalAddress();
 
     /**
      * Returns mask of I/O evens this session declared interest in.
      *
      * @return I/O event mask.
      */
     int getEventMask();
 
     /**
      * Declares interest in I/O event notifications by setting the event mask
      * associated with the session
      *
      * @param ops new I/O event mask.
      */
     void setEventMask(int ops);
 
     /**
      * Declares interest in a particular I/O event type by updating the event
      * mask associated with the session.
      *
      * @param op I/O event type.
      */
     void setEvent(int op);
 
     /**
      * Clears interest in a particular I/O event type by updating the event
      * mask associated with the session.
      *
      * @param op I/O event type.
      */
     void clearEvent(int op);
 
     /**
      * Terminates the session gracefully and closes the underlying I/O channel.
      * This method ensures that session termination handshake, such as the one
      * used by the SSL/TLS protocol, is correctly carried out.
      */
     @Override
     void close();
 
     /**
      * Returns status of the session:
      * <p>
      * {@link Status#ACTIVE}: session is active.
      * <p>
      * {@link Status#CLOSING}: session is being closed.
      * <p>
      * {@link Status#CLOSED}: session has been terminated.
      *
      * @return session status.
      */
     Status getStatus();
 
     /**
      * Returns value of the socket timeout in milliseconds. The value of
      * {@code 0} signifies the session cannot time out.
      *
      * @return socket timeout.
      */
     @Override
     Timeout getSocketTimeout();
 
     /**
      * Sets value of the socket timeout in milliseconds. The value of
      * {@code 0} signifies the session cannot time out.
      * <p>
      * Please note this operation may affect the last event time.
      *
      * @see #getLastEventTime()
      *
      * @param timeout socket timeout.
      */
     @Override
     void setSocketTimeout(Timeout timeout);
 
     /**
      * Returns timestamp of the last read event.
      *
      * @return timestamp.
      */
     long getLastReadTime();
 
     /**
      * Returns timestamp of the last write event.
      *
      * @return timestamp.
      */
     long getLastWriteTime();
 
     /**
      * Returns timestamp of the last I/O event including socket timeout reset.
      *
      * @see #getSocketTimeout()
      *
      * @return timestamp.
      */
     long getLastEventTime();
 
     /**
      * Updates the timestamp of the last read event
      */
     void updateReadTime();
 
     /**
      * Updates the timestamp of the last write event
      */
     void updateWriteTime();
 
 }