/*
 * Copyright (c) 2001, DecisionSoft Limited All rights reserved.
 * Please see LICENSE.TXT for more information.
 */

#ifndef _DataItemNav_HPP
#define _DataItemNav_HPP

#include <pathan/Pathan.hpp>

#include <pathan/dataItem/DataItemImpl.hpp>
#include <pathan/Sequence.hpp>
#include <vector>

class NavStepImpl;

///this class calculates a node list based on a context
class PATHAN_EXPORT DataItemNav : public DataItemImpl
{
public:
  DataItemNav(XPath2MemoryManager* memMgr);
  virtual ~DataItemNav();
	

  /** Add a new NavigationStep to the sequence of navigation steps to
      be performed. This operation is used by parse tree classes to
      turn themselves into an optimised, reusable navigation. **/
  void addStep(DataItem* step);

  /** Add a new NavigationStep to the sequence of navigation steps to
      be performed. This operation is used by parse tree classes to
      turn themselves into an optimised, reusable navigation. **/
  void addStep(NavStepImpl* step);

  /** Add a new NavigationStep to the start of the sequence of
      navigation steps to be performed.**/
  void addStepFront(DataItem* step);

  ///set the "go to root of tree first" flag.
  void setGotoRootFirst(bool gotoRoot);

  //collapase the compiled expression based on context
  virtual Sequence collapseTreeInternal(DynamicContext* context, int flags=0) const;

  virtual DataItem* staticResolution(StaticContext *context, StaticResolutionContext *src);
	
  bool getGotoRootFirst() const;
  const VectorOfDataItems &getSteps() const;

protected:
  void stepIteration(const DataItem *step, Sequence &candidateList, DynamicContext *context, int flags) const;
  ///returns a node list that has no duplicates in
  Sequence removeDuplicates(const Sequence &nodeList, DynamicContext* context) const;

  bool _gotoRoot;
  //list of steps to be performed.
  VectorOfDataItems _steps;
};

#endif