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JPPF, the open source grid computing solution
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/*
 * JPPF.
 * Copyright (C) 2005-2015 JPPF Team.
 * http://www.jppf.org
 *
 * Licensed 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.jppf.nio;

import org.jppf.utils.*;
import org.slf4j.*;

/**
 * Instances of this class perform the transition of a channel from one state to another.
 * They extend the Runnable interface so they can be executed concurrently by a pool of threads.
 * @param  the type of the states to use.
 * @param  the type of the transitions to use.
 * @author Laurent Cohen
 */
public class StateTransitionTask, T extends Enum> implements Runnable {
  /**
   * Logger for this class.
   */
  private static Logger log = LoggerFactory.getLogger(StateTransitionTask.class);
  /**
   * Determines whether DEBUG logging level is enabled.
   */
  private static boolean debugEnabled = LoggingUtils.isDebugEnabled(log);
  /**
   * Determines whether TRACE logging level is enabled.
   */
  private static boolean traceEnabled = log.isTraceEnabled();
  /**
   * The channel whose state is changing.
   */
  private final ChannelWrapper channel;
  /**
   * The factory ofr the server that runs this task.
   */
  private final NioServerFactory factory;

  /**
   * Initialize this task with the specified key and factory.
   * @param channel the channel whose state is changing.
   * @param factory the factory for the server that runs this task.
   */
  public StateTransitionTask(final ChannelWrapper channel, final NioServerFactory factory) {
    this.channel = channel;
    this.factory = factory;
  }

  /**
   * Perform the state transition, basically a read or write operation with corresponding state changes.
   */
  @Override
  @SuppressWarnings("unchecked")
  public void run() {
    StateTransitionManager transitionManager = factory.getServer().getTransitionManager();
    NioContext ctx = (NioContext) channel.getContext();
    try {
      T transition = null;
      synchronized(channel) {
        try {
          S s = ctx.getState();
          NioState state = factory.getState(s);
          if (traceEnabled) log.trace("performing transition to state {} for {}", s, channel);
          transition = state.performTransition(channel);
          if (transition != null) transitionManager.transitionChannel(channel, transition, transitionManager.checkSubmitTransition(channel, transition));
          else if (traceEnabled) log.trace("no further transition from {} for {}", s, channel);
        } catch (Exception|Error  e) {
          ctx.setEnabled(false);
          throw e;
        }
      }
    } catch(Exception|Error e) {
      try {
        if (debugEnabled) log.debug("error on channel {} :\n{}", channel, ExceptionUtils.getStackTrace(e));
        else log.warn("error on channel {} : {}", channel, ExceptionUtils.getMessage(e));
      } catch (Exception e2) {
        if (debugEnabled) log.debug("error on channel: {}", ExceptionUtils.getStackTrace(e));
        else log.warn("error on channel: {}", ExceptionUtils.getMessage(e));
      }
      if (e instanceof Exception) ctx.handleException(channel, (Exception) e);
      else throw (Error) e;
    }
  }
}