// Copyright (c) 2018 INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v5.5/Shape_detection/include/CGAL/Shape_detection/Region_growing/Region_growing_on_point_set/Least_squares_line_fit_sorting.h $
// $Id: Least_squares_line_fit_sorting.h 553d3c2 2020-04-10T13:03:50+02:00 Maxime Gimeno
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Florent Lafarge, Simon Giraudot, Thien Hoang, Dmitry Anisimov
//

#ifndef CGAL_SHAPE_DETECTION_REGION_GROWING_POINT_SET_LEAST_SQUARES_LINE_FIT_SORTING_H
#define CGAL_SHAPE_DETECTION_REGION_GROWING_POINT_SET_LEAST_SQUARES_LINE_FIT_SORTING_H

#include <CGAL/license/Shape_detection.h>

// STL includes.
#include <vector>
#include <algorithm>

// CGAL includes.
#include <CGAL/assertions.h>
#include <CGAL/Cartesian_converter.h>
#include <CGAL/Eigen_diagonalize_traits.h>
#include <CGAL/linear_least_squares_fitting_2.h>
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>

// Internal includes.
#include <CGAL/Shape_detection/Region_growing/internal/utils.h>
#include <CGAL/Shape_detection/Region_growing/internal/property_map.h>

namespace CGAL {
namespace Shape_detection {
namespace Point_set {

  /*!
    \ingroup PkgShapeDetectionRGOnPoints

    \brief Sorting of 2D points with respect to the local line fit quality.

    Indices of 2D input points are sorted with respect to the quality of the
    least squares line fit applied to the neighboring points of each point.

    \tparam GeomTraits
    must be a model of `Kernel`.

    \tparam InputRange
    must be a model of `ConstRange` whose iterator type is `RandomAccessIterator`.

    \tparam NeighborQuery
    must be a model of `NeighborQuery`.

    \tparam PointMap
    must be an `LvaluePropertyMap` whose key type is the value type of the input
    range and value type is `Kernel::Point_2`.
  */
  template<
  typename GeomTraits,
  typename InputRange,
  typename NeighborQuery,
  typename PointMap>
  class Least_squares_line_fit_sorting {

  public:

    /// \name Types
    /// @{

    /// \cond SKIP_IN_MANUAL
    using Traits = GeomTraits;
    using Input_range = InputRange;
    using Neighbor_query = NeighborQuery;
    using Point_map = PointMap;
    using Seed_map = internal::Seed_property_map;
    /// \endcond

    #ifdef DOXYGEN_RUNNING
      /*!
        an `LvaluePropertyMap` whose key and value type is `std::size_t`.
        This map provides an access to the ordered indices of input points.
      */
      typedef unspecified_type Seed_map;
    #endif

    /// @}

    /// \name Initialization
    /// @{

    /*!
      \brief initializes all internal data structures.

      \param input_range
      an instance of `InputRange` with 2D points

      \param neighbor_query
      an instance of `NeighborQuery` that is used internally to
      access point's neighbors

      \param point_map
      an instance of `PointMap` that maps an item from `input_range`
      to `Kernel::Point_2`

      \pre `input_range.size() > 0`
    */
    Least_squares_line_fit_sorting(
      const InputRange& input_range,
      NeighborQuery& neighbor_query,
      const PointMap point_map = PointMap()) :
    m_input_range(input_range),
    m_neighbor_query(neighbor_query),
    m_point_map(point_map),
    m_to_local_converter() {

      CGAL_precondition(input_range.size() > 0);

      m_order.resize(m_input_range.size());
      for (std::size_t i = 0; i < m_input_range.size(); ++i)
        m_order[i] = i;
      m_scores.resize(m_input_range.size());
    }

    /// @}

    /// \name Sorting
    /// @{

    /*!
      \brief sorts indices of input points.
    */
    void sort() {

      compute_scores();
      CGAL_postcondition(m_scores.size() > 0);

      Compare_scores cmp(m_scores);
      std::sort(m_order.begin(), m_order.end(), cmp);
    }

    /// @}

    /// \name Access
    /// @{

    /*!
      \brief returns an instance of `Seed_map` to access the ordered indices
      of input points.
    */
    Seed_map seed_map() {
      return Seed_map(m_order);
    }

    /// @}

  private:

    // Types.
    using Local_traits = Exact_predicates_inexact_constructions_kernel;
    using Local_FT = typename Local_traits::FT;
    using Local_point_2 = typename Local_traits::Point_2;
    using Local_line_2 = typename Local_traits::Line_2;
    using To_local_converter = Cartesian_converter<Traits, Local_traits>;
    using Compare_scores = internal::Compare_scores<Local_FT>;

    // Functions.
    void compute_scores() {

      std::vector<std::size_t> neighbors;
      std::vector<Local_point_2> points;

      for (std::size_t i = 0; i < m_input_range.size(); ++i) {

        neighbors.clear();
        m_neighbor_query(i, neighbors);
        neighbors.push_back(i);

        points.clear();
        for (std::size_t j = 0; j < neighbors.size(); ++j) {
          CGAL_precondition(neighbors[j] < m_input_range.size());

          const auto& key = *(m_input_range.begin() + neighbors[j]);
          points.push_back(m_to_local_converter(get(m_point_map, key)));
        }
        CGAL_postcondition(points.size() == neighbors.size());

        Local_line_2  fitted_line;
        Local_point_2 fitted_centroid;

        m_scores[i] = CGAL::linear_least_squares_fitting_2(
          points.begin(), points.end(),
          fitted_line, fitted_centroid,
          CGAL::Dimension_tag<0>(),
          Local_traits(),
          CGAL::Eigen_diagonalize_traits<Local_FT, 2>());
      }
    }

    // Fields.
    const Input_range& m_input_range;
    Neighbor_query& m_neighbor_query;
    const Point_map m_point_map;

    std::vector<std::size_t> m_order;
    std::vector<Local_FT> m_scores;

    const To_local_converter m_to_local_converter;
  };

} // namespace Point_set
} // namespace Shape_detection
} // namespace CGAL

#endif // CGAL_SHAPE_DETECTION_REGION_GROWING_POINT_SET_LEAST_SQUARES_LINE_FIT_SORTING_H
