#ifndef _include_StackIterator_h__
#define _include_StackIterator_h__

#include <iostream>
#include <iomanip>

namespace stack {

  // forward decl.
  template<class Stack, class Particle> class StackIteratorInfo;

  /**
     @class StackIterator
     
     The StackIterator is the main interface to iterator over
     particles on a stack. At the same time StackIterator is a
     Particle object by itself, thus there is no difference between
     type and ref_type for convenience of the physicist.

     This allows to write code like
     \verbatim
     for (auto& p : theStack) { p.SetEnergy(newEnergy); }  
     \endverbatim

     The template argument Stack determines the type of Stack object
     the data is stored in. A pointer to the Stack object is part of
     the StackIterator. In addition to Stack the iterator only knows
     the index fIndex in the Stack data. 

     The template argument Particles acts as a policy to provide
     readout function of Particle data from the stack. The Particle
     class must know how to retrieve information from the Stack data
     for a particle entry at any index fIndex.
  */
  
  template<typename Stack, typename Particle>
  class StackIterator : public Particle
  {
    friend Stack;
    friend Particle;
    friend StackIteratorInfo<Stack,Particle>;
    
  private:
    int fIndex;
    
    //#warning stacks should not be copied because of this:
    Stack* fData;
    
  public:
    StackIterator() : fData(0), fIndex(0) { }
    StackIterator(Stack& data, const int index) : fData(&data), fIndex(index) { }
    StackIterator(const StackIterator& mit) : fData(mit.fData), fIndex(mit.fIndex) { }
    
    StackIterator& operator++() { ++fIndex; return *this; }
    StackIterator operator++(int) { StackIterator tmp(*this); ++fIndex; return tmp; }
    bool operator==(const StackIterator& rhs) { return fIndex == rhs.fIndex; }
    bool operator!=(const StackIterator& rhs) { return fIndex != rhs.fIndex; }
    
    StackIterator& operator*() { return *this; }
    const StackIterator& operator*() const { return *this; }
    
  protected:
    int GetIndex() const { return fIndex; }
    Stack& GetStack() { return *fData; }
    const Stack& GetStack() const { return *fData; }

    // this is probably not needed rigth now:
    //inline StackIterator<Stack,Particle>& BaseRef() { return static_cast<StackIterator<Stack, Particle>&>(*this); }
    //inline const StackIterator<Stack,Particle>& BaseRef() const { return static_cast<const StackIterator<Stack, Particle>&>(*this); }
  };

  

  /**
     @class StackIteratorInfo
     
     This is the class where custom ... 
     Internal helper class for StackIterator. Document better...
   */
  
  template<typename _Stack, typename Particle>
  class StackIteratorInfo {
    
    friend Particle;  
  private:
    StackIteratorInfo() {}
    
  protected:
    inline _Stack& GetStack() { return static_cast<StackIterator<_Stack, Particle>*>(this)->GetStack(); }
    inline int GetIndex() const { return static_cast<const StackIterator<_Stack, Particle>*>(this)->GetIndex(); }
    inline const _Stack& GetStack() const { return static_cast<const StackIterator<_Stack, Particle>*>(this)->GetStack(); }
  };

} // end namespace stack
  
#endif