#ifndef DUNE_ONE_D_GRID_HIERITERATOR_HH
#define DUNE_ONE_D_GRID_HIERITERATOR_HH

/** \file
 * \brief The OneDGridHierarchicIterator class
 */

#include <stack>

#include <dune/grid/onedgrid/onedgridentitypointer.hh>

namespace Dune {

//**********************************************************************
//
// --OneDGridHierarchicIterator
// --HierarchicIterator
  /** \brief Iterator over the descendants of an entity.
   * \ingroup OneDGrid
  Mesh entities of codimension 0 ("elements") allow to visit all entities of
  codimension 0 obtained through nested, hierarchic refinement of the entity.
  Iteration over this set of entities is provided by the HierarchicIterator,
  starting from a given entity.
 */
template<class GridImp>
class OneDGridHierarchicIterator :
        public Dune::OneDGridEntityPointer <0,GridImp>
{
    enum { dim = GridImp::dimension };
    friend class OneDGridEntity<0,dim,GridImp>;

    // Stack entry
    typedef OneDGridList<OneDEntityImp<1> >::iterator StackEntry;

public:

    typedef typename GridImp::template Codim<0>::Entity Entity;
 
  //! Constructor
    OneDGridHierarchicIterator(int maxlevel) : OneDGridEntityPointer<0,GridImp>(OneDGridNullIteratorFactory<1>::null()),
                                               maxlevel_(maxlevel), elemStack()
    {}

    //! prefix increment
    void increment() {
      
        if (elemStack.empty())
            return;
        
        StackEntry old_target = elemStack.top();
        elemStack.pop();

        // Traverse the tree no deeper than maxlevel
        if (old_target->level_ < maxlevel_) {
            
            // Load sons of old target onto the iterator stack
            if (!old_target->isLeaf()) {

                elemStack.push(old_target->sons_[0]);
                
                // Add the second son only if it is different from the first one
                // i.e. the son is not just a copy of the father
                if (old_target->sons_[0] != old_target->sons_[1])
                    elemStack.push(old_target->sons_[1]);

            }
            
        }
        
        GridImp::getRealImplementation(this->virtualEntity_).setToTarget((elemStack.empty()) 
                                                                         ? OneDGridNullIteratorFactory<1>::null() : elemStack.top());
    }

private:

  //! max level to go down 
  int maxlevel_;

    std::stack<StackEntry> elemStack;

};

}  // end namespace Dune

#endif
