#ifndef __VolumeWeightedDataNodes_h_
#define __VolumeWeightedDataNodes_h_

#include "../misc_framework/DataNodes.h"
#include "GenericTosData.h"
#include "VolumeWeightedData.h"

/* Currently these only accumulate blocks.  They never discard blocks.  
 * GetBlocks returns a list which is identical to the previous call, or it
 * contains all the previous data plus one or more new blocks on the right
 * hand side.
 *
 * Potentially one of these data nodes should have the ability to reset
 * themselves when better data is available.  Although this may never happen,
 * we still have a contract for that, because if it ever happened, it could
 * effect a lot of code.
 *
 * The rule is that this data node can only do one of two things.  It can
 * present an empty list, or it can present a list which is identical to the
 * previous list, with something optionally added to the right hand side.
 *
 * If one of these had 10 items, then it decided to reset itself, and the new
 * version has only 5 items, it must do this in two steps.  First it signals
 * all listeners, and presents the empty list.  Then it presents the new list
 * with 5 members.
 *
 * Changing existing data, although now allowed, is still very disruptive, and
 * should be avoided.
 */

class VolumeWeightedDataNode : public DataNode
{
private:
  VolumeBlockFactory _volumeBlockFactory;
  GenericTosDataNode *_tosData;
  void onWakeup(int msgId);
  static bool getHistoryValid();

  VolumeWeightedDataNode(DataNodeArgument const &args);
  friend class DataNode;

public:
  VolumeBlocks const &getBlocks() const 
  { return _volumeBlockFactory.getBlocks(); }
  VolumeBlocks::size_type getBlockCount() const 
  { return _volumeBlockFactory.getBlockCount(); }
  DataNode::Integer getGroupBy() const 
  { return _volumeBlockFactory.getGroupBy(); }

  static DataNodeLink *find(DataNodeListener *listener, int msgId,
                            VolumeWeightedDataNode *&node,
                            std::string const &symbol, Integer groupBy);
};

#endif