/*
    Copyright (C) 2004  [Jörg Rüdenauer]
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.
    
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
    
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
    
*/
package tokenring;

import fdda.algorithm.Node;
import fdda.algorithm.Message;
import fdda.algorithm.WrongStateException;

import java.util.List;
import java.util.Iterator;

/**
 * Abstract superclass for nodes in a token ring.
 */
public abstract class TokenRingNode extends Node {

  /**
   * Returns the following node in the ring.
   * @return the next node
   */
  protected final Node getFollowingNode() {
    List neighbours = this.getNeighbours();
    for (Iterator it = neighbours.iterator(); it.hasNext(); ) {
      Node neighbour = (Node) it.next();
      if (this.canSendMessageTo(neighbour)) {
        return neighbour;
      }
    }
    return null;
  }
  
  /**
   * Creates a message to the following node in the ring.
   * @param payload the payload
   * @param label the label
   * @return the message, or null if no working outgoing connection exists
   * @throws WrongStateException
   */
  protected final Message createMessageToNextNode(Object payload, String label) 
  throws WrongStateException {
    Node neighbour = getFollowingNode();
    if (neighbour != null) {
      Message message = this.createMessage(neighbour, payload);
      message.setLabel(label);
      return message;
    }
    else {
      return null;
    }
  }
  
  /**
   * Sends a message to the following node in the ring, if it is possible.
   * @param payload the payload
   * @param label the label
   * @throws WrongStateException
   */
  protected final void sendMessageToNextNode(Object payload, String label) 
  throws WrongStateException {
    Node neighbour = getFollowingNode();
    if (neighbour != null) this.sendMessage(neighbour, payload, label);
  }

}