/****************************************************************************
 * Copyright (C) 2009-2015 EPAM Systems
 * 
 * This file is part of Indigo toolkit.
 * 
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 3 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 * 
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 ***************************************************************************/

#ifndef __pool_h__
#define __pool_h__

#include "base_cpp/array.h"
#include "base_cpp/exception.h"

namespace indigo {

DECL_EXCEPTION(PoolError);

template <typename T> class Pool
{
public:
   DECL_TPL_ERROR(PoolError);

   Pool () : _size(0), _first(-1)
   {
   }

   int add () 
   {
      if (_first == -1)
      {
         _array.push();
         _next.push(-2);
         _size++;

         return _array.size() - 1;
      }

      int idx = _first;

      _first = _next[_first];

      if (_first == -2)
         throw Error("internal error: index %d is used in add()", idx);

      _next[idx] = -2;
      _size++;

      return idx;
   }

   int add (const T &item) 
   {
      int idx = add();

      _array[idx] = item;
      return idx;
   }

   void remove (int idx)
   {
      if (_next[idx] != -2)
         throw Error("trying to remove unused element #%d", idx);

      _next[idx] = _first;
      _first = idx;

      _size--;
   }

   bool hasElement(int idx) const
   {
      return (_next[idx] == -2);
   }

   int size () const
   {
      return _size;
   }

   int begin () const
   {
      int i;

      for (i = 0; i < _next.size(); i++)
         if (_next[i] == -2)
            break;

      return i;
   }

   int next (int i) const
   {
      for (i++; i < _next.size(); i++)
         if (_next[i] == -2)
            break;

      return i;
   }

   int end () const
   {
      return _array.size();
   }

   void clear ()
   {
      _array.clear();
      _next.clear();
      _size = 0;
      _first = -1;
   }

   const T & operator [] (int index) const
   {  
      if (_next[index] != -2)
         throw Error("access to unused element %d", index);
      return _array[index];
   }

   T & operator [] (int index)
   {  
      if (_next[index] != -2)
         throw Error("access to unused element %d", index);
      return _array[index];
   }

   const T & at (int index) const
   {                        
      return (*this)[index];
   }

   T & at (int index)
   {                        
      return (*this)[index];
   }

protected:
   Array<T>   _array; // pool elements

   // _next[i] >= 0  => _array[i] is not used,
   //                    _next[i] contains the index of the next unused element
   // _next[i] == -1 => _array[i] is the last unused element
   // _next[i] == -2 => _array[i] is used
   Array<int> _next;

   int        _size;  // number of _array items used

   int        _first; // index of the first unused element (-1 if all are used)

private:
   Pool (const Pool<T> & ); // no implicit copy
};

}

#endif
