// Copyright (c) 2020 GeometryFactory SARL (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1.1/Shape_regularization/include/CGAL/Shape_regularization/Segments/Offset_regularization_2.h $
// $Id: include/CGAL/Shape_regularization/Segments/Offset_regularization_2.h 08b27d3db14 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Dmitry Anisimov, Gennadii Sytov, Jean-Philippe Bauchet, Florent Lafarge
//

#ifndef CGAL_SHAPE_REGULARIZATION_OFFSET_REGULARIZATION_2_H
#define CGAL_SHAPE_REGULARIZATION_OFFSET_REGULARIZATION_2_H

#include <CGAL/license/Shape_regularization.h>

// Boost includes.
#include <CGAL/boost/graph/named_params_helper.h>
#include <CGAL/Named_function_parameters.h>

// Internal includes.
#include <CGAL/Shape_regularization/internal/Segment_wrapper_2.h>
#include <CGAL/Shape_regularization/internal/Collinear_groups_2.h>
#include <CGAL/Shape_regularization/internal/Unique_segments_2.h>

namespace CGAL {
namespace Shape_regularization {
namespace Segments {

  /*!
    \ingroup PkgShapeRegularizationRefSegments

    \brief An offset-based regularization type for 2D segments that reinforces
    collinearity relationships.

    The input groups of segments should each contain (near) parallel segments.
    In order to achieve that, one may use the class `Segments::Angle_regularization_2`
    or the function `Segments::parallel_groups()`. Each group of parallel segments
    may be inserted using the method `add_group()`.

    \tparam GeomTraits
    a model of `Kernel`

    \tparam InputRange
    a model of `Range` whose iterator type is `RandomAccessIterator`

    \tparam SegmentMap
    a model of `ReadWritePropertyMap` whose key type is the value type of the `InputRange`
    and value type is `GeomTraits::Segment_2`. The default is
    `CGAL::Identity_property_map<typename GeomTraits::Segment_2>`.

    \cgalModels{RegularizationType}
  */
  template<
  typename GeomTraits,
  typename InputRange,
  typename SegmentMap = CGAL::Identity_property_map<typename GeomTraits::Segment_2> >
  class Offset_regularization_2 {
  public:

    /// \name Types
    /// @{

    /// \cond SKIP_IN_MANUAL
    using Traits = GeomTraits;
    using Input_range = InputRange;
    using Segment_map = SegmentMap;
    /// \endcond

    /// Number type.
    typedef typename GeomTraits::FT FT;

    /// \cond SKIP_IN_MANUAL
    using Point_2 = typename Traits::Point_2;
    using Vector_2 = typename Traits::Vector_2;
    using Segment_2 = typename Traits::Segment_2;

    using Segment_wrapper_2 = internal::Segment_wrapper_2<Traits>;
    using Collinear_groups_2 = internal::Collinear_groups_2<Traits, Input_range, Segment_map>;
    using Unique_segments_2 = internal::Unique_segments_2<Traits, Input_range, Segment_map>;
    using Indices = std::vector<std::size_t>;
    /// \endcond

    /// @}

    /// \name Initialization
    /// @{

    /*!
      \brief initializes all internal data structures.

      \tparam NamedParameters
      a sequence of \ref bgl_namedparameters "Named Parameters"

      \param input_range
      a range of 2D segments to be regularized

      \param np
      an optional sequence of \ref bgl_namedparameters "Named Parameters"
      among the ones listed below; this parameter can be omitted,
      the default values are then used

      \cgalNamedParamsBegin
        \cgalParamNBegin{maximum_offset}
          \cgalParamDescription{maximum allowed orthogonal distance between two parallel segments
            such that they are considered to be collinear}
          \cgalParamType{`GeomTraits::FT`}
          \cgalParamDefault{0.5 unit length}
        \cgalParamNEnd
        \cgalParamNBegin{segment_map}
          \cgalParamDescription{an instance of `SegmentMap` that maps an item from `input_range`
          to `GeomTraits::Segment_2`}
          \cgalParamDefault{`SegmentMap()`}
        \cgalParamNEnd
      \cgalNamedParamsEnd

      \pre input_range.size() >= 2
      \pre maximum_offset >= 0
    */
    template<typename NamedParameters = parameters::Default_named_parameters>
    Offset_regularization_2(
      InputRange& input_range,
      const NamedParameters& np = parameters::default_values()) :
    m_input_range(input_range),
    m_segment_map(parameters::choose_parameter(parameters::get_parameter(
      np, internal_np::segment_map), SegmentMap())),
    m_num_modified_segments(0) {

      const FT max_offset = parameters::choose_parameter(
        parameters::get_parameter(np, internal_np::maximum_offset), FT(1) / FT(2));
      CGAL_precondition(max_offset >= FT(0));

      m_max_offset = max_offset;
      if (m_max_offset < FT(0)) {
        std::cerr << "WARNING: The maximum offset bound has to be within [0, +inf)! ";
        std::cerr << " Setting to the default value: 0.5." << std::endl;
        m_max_offset = FT(1) / FT(2);
      }
      clear();
      create_unique_group();
    }

    /*!
      \brief inserts a group of segments from `input_range`.

      Each group of segments is provided as a collection of their indices and only
      segments within the group are being regularized that is no relationships
      between segments from different groups are taken into account.

      The user must not use this method until he has meaningful groups of segments
      (see more in the user manual). By default, all segments are inserted as a group.

      \tparam IndexRange
      a model of `ConstRange` whose value type is `std::size_t`

      \param index_range
      a const range of segment indices

      \pre index_range.size() >= 2
    */
    template<typename IndexRange>
    void add_group(
      const IndexRange& index_range) {

      if (m_is_first_call) {
        clear();
        m_is_first_call = false;
      }

      if (index_range.size() < 2) return;
      update_wrappers(index_range);
      ++m_num_groups;
    }

    /// @}

    /// \name Access
    /// @{

    /*!
      \brief calculates the target value between 2 parallel segments, which are
      direct neighbors to each other.

      The target value is the distance between two parallel segments `i` and `j`,
      where the distance is defined as the distance between the midpoint of the
      ith segment and the projection of this point onto the supporting line
      of the jth segment.

      \param i
      index of the first segment

      \param j
      index of the second segment

      \pre i >= 0 && i < input_range.size()
      \pre j >= 0 && j < input_range.size()
    */
    FT target(
      const std::size_t i,
      const std::size_t j) const {

      CGAL_precondition(i < m_input_range.size());
      CGAL_precondition(j < m_input_range.size());
      CGAL_assertion(m_wraps.size() == m_input_range.size());

      const auto& wrapi = m_wraps[i];
      CGAL_assertion(wrapi.is_used);
      const auto& wrapj = m_wraps[j];
      CGAL_assertion(wrapj.is_used);

      const FT ydifference =
        wrapj.ref_coords.y() - wrapi.ref_coords.y();
      const FT target_value = ydifference;
      return target_value;
    }

    /*!
      \brief returns `maximum_offset`.
    */
    FT bound(const std::size_t) const {
      return m_max_offset;
    }

    /*!
      \brief applies new positions computed by the `QuadraticProgramTraits`
      to the initial segments.

      Number of values in `solution` equals to the number n of segments being
      regularized + the number m of neighbor pairs between these segments. Each
      of n values is an offset that is added to the initial segment position.

      \param solution
      a vector with offsets in unit lengths

      \pre solution.size() >= 1
    */
    void update(
      const std::vector<FT>& solution) {

      CGAL_precondition(solution.size() >= 1);
      m_num_modified_segments = 0;
      for (const auto& wrap : m_wraps) {
        if (!wrap.is_used) continue;

        // Get segment.
        const std::size_t seg_index = wrap.index;
        CGAL_assertion(seg_index < m_input_range.size());
        const auto& segment = get(m_segment_map,
          *(m_input_range.begin() + seg_index));
        const auto& source = segment.source();
        const auto& target = segment.target();

        // Get update values.
        CGAL_assertion(seg_index < solution.size());
        const FT difference = solution[seg_index];
        const auto normal =
          internal::perpendicular_vector_2(wrap.direction);

        // Update segment.
        Segment_2 modified;
        align_segment(source, target, difference, normal, modified);
        put(m_segment_map,
          *(m_input_range.begin() + seg_index), modified);
        ++m_num_modified_segments;
      }
    }

    /// @}

    /// \name Groups
    /// @{

    /*!
      \brief creates groups of indices, where each group represents collinear segments.

      This method calls `Segments::collinear_groups()`.

      \tparam OutIterator
      a model of `OutputIterator` that accepts elements of type `std::vector<std::size_t>`

      \param groups
      an output iterator with groups of segment indices
    */
    template<typename OutIterator>
    OutIterator collinear_groups(OutIterator groups) const {

      const Collinear_groups_2 grouping(
        m_input_range,
        CGAL::parameters::maximum_offset(m_max_offset),
        m_segment_map, Traits());
      return grouping.groups(groups);
    }

    /// @}

    /// \name Miscellaneous
    /// @{

    /*!
      \brief returns the number of modified segments.
    */
    std::size_t number_of_modified_segments() const {
      return m_num_modified_segments;
    }

    /*!
      \brief returns segments, which best-fit collinear groups.

      This method first calls `Segments::collinear_groups()`
      and then substitutes each group of collinear segments by an average segment.
      The number of returned segments is the number of detected collinear groups.

      \tparam OutIterator
      a model of `OutputIterator` that accepts segments of type `GeomTraits::Segment_2`

      \param segments
      an output iterator with the simplified segments
    */
    template<typename OutIterator>
    OutIterator unique_segments(OutIterator segments) const {

      const Unique_segments_2 unique(
        m_input_range,
        CGAL::parameters::maximum_offset(m_max_offset),
        m_segment_map, Traits());
      return unique.segments(segments);
    }

    /// @}

    /// \name Memory Management
    /// @{

    /*!
      \brief clears all internal data structures.
    */
    void clear() {
      m_num_groups = 0;
      m_is_first_call = true;
      m_num_modified_segments = 0;
      for (auto& wrap : m_wraps) {
        wrap.is_used = false;
      }
    }

    /// @}

    // EXTRA METHODS TO TEST THE CLASS!
    /// \cond SKIP_IN_MANUAL
    std::size_t number_of_groups() const {
      return m_num_groups;
    }
    /// \endcond

  private:
    Input_range& m_input_range;
    const Segment_map m_segment_map;

    FT m_max_offset;
    std::vector<Segment_wrapper_2> m_wraps;

    std::size_t m_num_modified_segments;
    std::size_t m_num_groups;
    bool m_is_first_call;

    void create_unique_group() {

      if (m_input_range.size() < 2) return;
      CGAL_precondition(m_input_range.size() >= 2);

      m_wraps.clear();
      m_wraps.resize(m_input_range.size());

      Indices group(m_input_range.size());
      std::iota(group.begin(), group.end(), 0);
      update_segment_data(group);
      m_num_groups = 1;
    }

    template<typename IndexRange>
    void update_segment_data(
      const IndexRange& index_range) {

      Point_2 frame_origin(FT(0), FT(0)); std::size_t count = 0;
      for (const auto seg_index : index_range) {
        CGAL_assertion(seg_index < m_wraps.size());
        auto& wrap = m_wraps[seg_index];

        const auto& segment =
          get(m_segment_map, *(m_input_range.begin() + seg_index));
        wrap.set_qp(seg_index, segment);

        if (count == 0) frame_origin = wrap.barycenter;
        wrap.set_ref_coords(frame_origin);
        ++count;
      }
    }

    template<typename IndexRange>
    void update_wrappers(
      const IndexRange& index_range) {

      Point_2 frame_origin(FT(0), FT(0)); std::size_t count = 0;
      for (const auto seg_index : index_range) {
        CGAL_assertion(seg_index < m_wraps.size());
        auto& wrap = m_wraps[seg_index];
        wrap.is_used = true;

        if (count == 0) frame_origin = wrap.barycenter;
        wrap.set_ref_coords(frame_origin);
        ++count;
      }
    }

    void align_segment(
      const Point_2& source,
      const Point_2& target,
      const FT difference,
      const Vector_2& normal,
      Segment_2& modified) const {

      const Point_2 new_source = Point_2(
        source.x() + difference * normal.x(),
        source.y() + difference * normal.y());
      const Point_2 new_target = Point_2(
        target.x() + difference * normal.x(),
        target.y() + difference * normal.y());
      modified = Segment_2(new_source, new_target);
    }
  };

} // namespace Segments
} // namespace Shape_regularization
} // namespace CGAL

#endif // CGAL_SHAPE_REGULARIZATION_OFFSET_REGULARIZATION_2_H
