// Copyright (c) 2007-08  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you may redistribute it under
// the terms of the Q Public License version 1.0.
// See the file LICENSE.QPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL:
// $Id:
//
// Author(s) : Pierre Alliez and Laurent Saboret

#ifndef CGAL_AVERAGE_SPACING_3_H
#define CGAL_AVERAGE_SPACING_3_H

#include <CGAL/Search_traits_3.h>
#include <CGAL/Orthogonal_k_neighbor_search.h>

#include <iterator>
#include <list>

CGAL_BEGIN_NAMESPACE


/// Compute average spacing of one query point from K nearest neighbors.
///
/// Precondition: KNN >= 2.
///
/// @heading Parameters:
/// @param Kernel Geometric traits class.
/// @param Tree KD-tree.
///
/// @return average spacing (scalar).
template < typename Kernel,
           typename Tree >
typename Kernel::FT
average_spacing_3(const typename Kernel::Point_3& query, ///< 3D point whose spacing we want to compute
                  Tree& tree,                            ///< KD-tree
                  unsigned int KNN)                      ///< number of neighbors
{
  // basic geometric types
  typedef typename Kernel::FT FT;
  typedef typename Kernel::Point_3 Point;
  typedef typename Kernel::Plane_3 Plane;
  typedef typename Kernel::Vector_3 Vector;

  // types for K nearest neighbors search
  typedef typename CGAL::Search_traits_3<Kernel> Tree_traits;
  typedef typename CGAL::Orthogonal_k_neighbor_search<Tree_traits> Neighbor_search;
  typedef typename Neighbor_search::iterator Search_iterator;

  // performs KNN + 1 queries (if unique the query point is
  // output first). search may be aborted when KNN is greater
  // than number of input points
  Neighbor_search search(tree,query,KNN+1);
  Search_iterator search_iterator = search.begin();
  FT sum_distances = (FT)0.0;
  unsigned int i;
  for(i=0;i<(KNN+1);i++)
  {
    if(search_iterator == search.end())
      break; // premature ending

    Point p = search_iterator->first;
    sum_distances += std::sqrt(CGAL::squared_distance(query,p));
    search_iterator++;
  }

  // output average spacing
  return sum_distances / (FT)i;
}


/// Compute average spacing from K nearest neighbors.
/// This variant requires the kernel.
///
/// Precondition: KNN >= 2.
///
/// @heading Parameters:
/// @param InputIterator value_type is Point_3.
/// @param Kernel Geometric traits class.
///
/// @return average spacing (scalar).
template <typename InputIterator,
          typename Kernel
>
typename Kernel::FT
average_spacing_3(InputIterator first,    ///< input points
                  InputIterator beyond,
                  unsigned int KNN,       ///< number of neighbors
                  const Kernel& /*kernel*/)
{
  // types for K nearest neighbors search structure
  typedef typename Kernel::FT FT;
  typedef typename CGAL::Search_traits_3<Kernel> Tree_traits;
  typedef typename CGAL::Orthogonal_k_neighbor_search<Tree_traits> Neighbor_search;
  typedef typename Neighbor_search::Tree Tree;

  // precondition: at least one element in the container.
  // to fix: should have at least three distinct points
  // but this is costly to check
  CGAL_precondition(first != beyond);

  // precondition: at least 2 nearest neighbors
  CGAL_precondition(KNN >= 2);

  // instanciate a KD-tree search
  Tree tree(first,beyond);

  // iterate over input points, compute and output normal
  // vectors (already normalized)
  FT sum_spacings = (FT)0.0;
  unsigned int nb_points = 0;
  InputIterator it;
  for(it = first; it != beyond; it++)
  {
    sum_spacings += average_spacing_3<Kernel,Tree>(*it,tree,KNN);
    nb_points++;
  }

  // return average spacing
  return sum_spacings / (FT)nb_points;
}

/// Compute average spacing from K nearest neighbors.
/// This variant deduces the kernel from iterator types.
///
/// Precondition: KNN >= 2.
///
/// @heading Parameters:
/// @param InputIterator value_type is Point_3.
/// @param FT number type.
///
/// @return average spacing (scalar)
template < typename InputIterator,
           typename FT
>
FT
average_spacing_3(InputIterator first,    ///< input points
                  InputIterator beyond,
                  unsigned int KNN)       ///< number of neighbors
{
  typedef typename std::iterator_traits<InputIterator>::value_type Value_type;
  typedef typename Kernel_traits<Value_type>::Kernel Kernel;
  return average_spacing_3(first,beyond,KNN,Kernel());
}


CGAL_END_NAMESPACE

#endif // CGAL_AVERAGE_SPACING_3_H