// Copyright (c) 2009-2015 GeometryFactory (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1.2/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/orient_polygon_soup.h $
// $Id: include/CGAL/Polygon_mesh_processing/orient_polygon_soup.h 37e2b278910 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Laurent Rineau and Sebastien Loriot


#ifndef CGAL_POLYGON_MESH_PROCESSING_ORIENT_POLYGON_SOUP
#define CGAL_POLYGON_MESH_PROCESSING_ORIENT_POLYGON_SOUP

#include <CGAL/license/Polygon_mesh_processing/orientation.h>

#include <CGAL/disable_warnings.h>

#include <CGAL/tuple.h>
#include <CGAL/array.h>
#include <CGAL/assertions.h>
#include <CGAL/Named_function_parameters.h>
#include <CGAL/boost/graph/named_params_helper.h>

#include <boost/container/flat_set.hpp>
#include <boost/container/flat_map.hpp>

#include <set>
#include <map>
#include <stack>
#include <vector>
#include <algorithm>
#include <iostream>

namespace CGAL {

namespace Polygon_mesh_processing {

/** \ingroup PMP_orientation_grp
 *
 *  Default visitor model of `PMPPolygonSoupOrientationVisitor`.
 *  All of its functions have an empty body. This class can be used as a
 *  base class if only some of the functions of the concept will be overridden.
 */
struct Default_orientation_visitor{
  void non_manifold_edge(std::size_t, std::size_t, std::size_t){}
  void non_manifold_vertex(std::size_t,std::size_t){}
  void duplicated_vertex(std::size_t, std::size_t){}
  void vertex_id_in_polygon_replaced(std::size_t, std::size_t, std::size_t){}
  void polygon_orientation_reversed(std::size_t) {}
  void link_connected_polygons(std::size_t, const std::vector<std::size_t>&){}
};

namespace internal {

template<class PointRange, class PolygonRange, class Visitor = Default_orientation_visitor>
struct Polygon_soup_orienter
{
  typedef typename PointRange::value_type                               Point_3;
  typedef typename PolygonRange::value_type                           Polygon_3;
/// Index types
  typedef typename std::iterator_traits<
            typename Polygon_3::iterator >::value_type                     V_ID;
  typedef typename std::vector<Polygon_3>::size_type                       P_ID;
//  typedef int                                                             CC_ID;
  typedef std::pair<V_ID, V_ID>                                       V_ID_pair;
/// Container types
  typedef PointRange                                                     Points;
  typedef PolygonRange                                                 Polygons;

  typedef std::set<V_ID_pair>                                      Marked_edges;
  typedef boost::container::flat_map< V_ID, boost::container::flat_set<P_ID> >  Internal_map_type;
  typedef std::vector< Internal_map_type >                             Edge_map;
  typedef typename Internal_map_type::iterator                Edge_map_iterator;

/// Data members
  Points& points;             //< the set of input points
  Polygons& polygons;         //< the set of input polygons
  Edge_map edges;             //< the set of edges of the input polygons
  Marked_edges marked_edges;  //< the set of singular edges or edges incident
                              //<   to non-compatible orientation polygons
  Visitor& visitor;

  /// for each polygon referenced by its position in `polygons`, indicates
  /// the connected component it belongs too after orientation.
//  std::vector< CC_ID > polygon_cc_id;

/// Utility functions
  static V_ID_pair canonical_edge(V_ID i, V_ID j)
  {
    return i<j ? V_ID_pair(i,j):V_ID_pair(j,i);
  }

  static bool is_edge_marked(V_ID i, V_ID j, Marked_edges& marked_edges)
  {
    return marked_edges.count(canonical_edge(i,j)) > 0;
  }

  static void set_edge_marked(V_ID i, V_ID j, Marked_edges& marked_edges)
  {
    marked_edges.insert(canonical_edge(i,j));

  }

  static std::array<V_ID,3>
  get_neighbor_vertices(V_ID v_id, P_ID polygon_index, const Polygons& polygons)
  {
    std::size_t nbv = polygons[polygon_index].size(), pvid=0;
    for (; pvid!=nbv; ++pvid)
      if (v_id==polygons[polygon_index][pvid]) break;
    CGAL_assertion( pvid!=nbv );
    V_ID prev = polygons[polygon_index][ (pvid+nbv-1)%nbv ];
    V_ID next = polygons[polygon_index][ (pvid+1)%nbv ];
    return make_array(prev,v_id,next);
  }

  static std::pair<V_ID,P_ID>
  next_cw_vertex_around_source(V_ID src, V_ID tgt, const Polygons& polygons, Edge_map& edges, Marked_edges& marked_edges)
  {
    typedef std::pair<V_ID,P_ID> VID_and_PID;
    if ( is_edge_marked(src,tgt,marked_edges) ) return VID_and_PID(src,300612);
    Edge_map_iterator em_it=edges[tgt].find(src);
    if ( em_it==edges[tgt].end() ) return VID_and_PID(src,300612);// the vertex is on the border
    CGAL_assertion(em_it->second.size()==1);
    P_ID p_id = *(em_it->second.begin());
    return VID_and_PID(get_neighbor_vertices(src, p_id, polygons)[2], p_id);
  }

  static std::pair<V_ID,P_ID>
  next_ccw_vertex_around_target(V_ID src, V_ID tgt, const Polygons& polygons, Edge_map& edges, Marked_edges& marked_edges)
  {
    typedef std::pair<V_ID,P_ID> VID_and_PID;
    if ( is_edge_marked(src,tgt,marked_edges) ) return VID_and_PID(tgt,300612);
    Edge_map_iterator em_it=edges[tgt].find(src);
    if ( em_it==edges[tgt].end() ) return VID_and_PID(tgt,300612);// the vertex is on the border
    CGAL_assertion(em_it->second.size()==1);
    P_ID p_id = *(em_it->second.begin());
    return VID_and_PID(get_neighbor_vertices(tgt, p_id, polygons)[0], p_id);
  }

  void inverse_orientation(const std::size_t index) {
    visitor.polygon_orientation_reversed(index);
    std::reverse(polygons[index].begin(), polygons[index].end());
  }

  void replace_vertex_index_in_polygon(
    std::size_t polygon_id,
    V_ID old_index,
    V_ID new_index)
  {
    visitor.vertex_id_in_polygon_replaced(polygon_id, old_index, new_index);
    for(V_ID& i : polygons[polygon_id])
      if( i==old_index )
        i=new_index;
  }

/// Functions filling containers
  static void fill_incident_polygons_per_vertex(
    const Polygons& polygons,
    std::vector< std::vector<P_ID> >& incident_polygons_per_vertex)
  {
    P_ID nb_polygons=polygons.size();
    for(P_ID ip=0; ip<nb_polygons; ++ip)
    {
      for(V_ID iv : polygons[ip])
        incident_polygons_per_vertex[iv].push_back(ip);
    }
  }

  Polygon_soup_orienter(Points& points, Polygons& polygons, Visitor& visitor)
    : points(points), polygons(polygons), edges(points.size()), visitor(visitor)
  {}

//filling containers
  static void fill_edge_map(Edge_map& edges, Marked_edges& marked_edges, const Polygons& polygons, Visitor& visitor) {
    // Fill edges
    for (P_ID i = 0; i < polygons.size(); ++i)
    {
      const P_ID size = polygons[i].size();
      for (P_ID j = 0; j < size; ++j) {
        V_ID i0 = polygons[i][j];
        V_ID i1 = polygons[i][(j + 1) % size];
        edges[i0][i1].insert(i);
      }
    }

    // Fill non-manifold edges
    marked_edges.clear();
    for (P_ID i = 0; i < polygons.size(); ++i)
    {
      const P_ID size = polygons[i].size();
      for (P_ID j = 0; j < size; ++j) {
        V_ID i0 = polygons[i][j];
        V_ID i1 = polygons[i][(j + 1) % size];

        std::size_t nb_edges = 0;
        Edge_map_iterator em_it = edges[i0].find(i1);
        if (em_it != edges[i0].end()) nb_edges += em_it->second.size();
        em_it = edges[i1].find(i0);
        if (em_it != edges[i1].end()) nb_edges += em_it->second.size();

        if (nb_edges > 2)
        {
          visitor.non_manifold_edge(i0, i1, nb_edges);
          set_edge_marked(i0, i1, marked_edges);
        }
      }
    }
  }

  static void fill_edge_map(Edge_map& edges, Marked_edges& marked_edges, const Polygons& polygons) {
    Visitor dum;
    fill_edge_map(edges, marked_edges, polygons, dum);
  }
  void fill_edge_map()
  {
    fill_edge_map(edges, marked_edges, polygons, visitor);
  }

  /// We try to orient polygon consistently by walking in the dual graph, from
  /// a not yet re-oriented polygon.
  /// We have an edge between two polygons if they share an edge, and this edge
  /// is shared by exactly two polygons. While walking along an edge, we reorient
  /// the polygon we walked in if its orientation is not compatible with the one
  /// we come from.
  /// If the polygon was already marked as oriented, then we cut the dual edge
  /// in the graph and the primal edge is marked.
  /// At the same time, we assign an id to each polygon in the same connected
  /// component of the dual graph.
  void orient()
  {
    std::vector<bool> oriented;
    std::stack<std::size_t> stack;
//    polygon_cc_id.resize(polygons.size(), -1);

    // We first consider all polygons as non-oriented
    oriented.resize(polygons.size());

    P_ID polygon_index = 0;

//    CC_ID current_cc_index=-1;
    while (polygon_index != polygons.size())
    {
      // We look for the first polygon not already oriented
      while ( polygon_index != polygons.size() && oriented[polygon_index] ) {
        ++polygon_index;
      }
      if(polygon_index == polygons.size()) break;

//      ++ current_cc_index; // visit a new connected component

      // we visit the connected component by crossing edges manifold edges
      oriented[polygon_index] = true;
      stack.push(polygon_index);
      while(! stack.empty() )
      {
        const P_ID to_be_oriented_index = stack.top();
        stack.pop();

//        CGAL_assertion(polygon_cc_id[to_be_oriented_index]==-1);
//        polygon_cc_id[to_be_oriented_index]=current_cc_index;

        const P_ID size = polygons[to_be_oriented_index].size();
        for(P_ID ih = 0 ; ih < size ; ++ih) {
          P_ID ihp1 = (ih+1)%size;
          const V_ID i1 = polygons[to_be_oriented_index][ih];
          const V_ID i2 = polygons[to_be_oriented_index][ihp1];

          if( is_edge_marked(i1,i2,marked_edges) ) continue;

          // edge (i1,i2)
          Edge_map_iterator it_same_orient = edges[i1].find(i2);
          // edges (i2,i1)
          Edge_map_iterator it_other_orient = edges[i2].find(i1);

          CGAL_assertion(it_same_orient != edges[i1].end());
          CGAL_assertion(it_other_orient == edges[i2].end() ||
                         it_other_orient->second.size()==1);

          if (it_same_orient->second.size() > 1)
          {
            CGAL_assertion(it_other_orient == edges[i2].end());
            // one neighbor but with the same orientation
            P_ID index = *(it_same_orient->second.begin());
            if(index == to_be_oriented_index)
              index = *(++it_same_orient->second.begin());
            if(oriented[index])
            {
              // polygon already oriented but its orientation is not compatible ---> mark the edge and continue
              set_edge_marked(i1,i2,marked_edges);
              continue; // next edge
            }

            // reverse the orientation
            const P_ID size = polygons[index].size();
            for(P_ID j = 0; j < size; ++j) {
              V_ID i0 = polygons[index][j];
              V_ID i1 = polygons[index][(j+1)%size];
              Edge_map_iterator em_it = edges[i0].find(i1);
              CGAL_assertion_code(const bool r = )
                em_it->second.erase(index)
              CGAL_assertion_code(!= 0);
              CGAL_assertion(r);
              if ( em_it->second.empty() ) edges[i0].erase(em_it);
            }
            inverse_orientation(index);
            for(P_ID j = 0; j < size; ++j) {
              V_ID i0 = polygons[index][j];
              V_ID i1 = polygons[index][(j+1)%size];
              edges[i0][i1].insert(index);
            }
            // inverse the orientation of polygon #index
            oriented[index] = true;
            stack.push(index);
          }
          else{
            if( it_other_orient != edges[i2].end() ){
              CGAL_assertion(it_same_orient->second.size() == 1);
              CGAL_assertion(it_other_orient->second.size() == 1);
              // one polygon, same orientation
              const P_ID index = *(it_other_orient->second.begin());
              if(oriented[index]) continue; //nothing todo already processed and correctly oriented
              oriented[index] = true;
              // keep the orientation of polygon #index
              stack.push(index);
            }
          }
        } // end for on all edges of one
      } // end while loop on the polygons of the connected component
    } // end while loop on all non-oriented polygons remaining
  }

  /// A vertex is said to be singular if its link is neither a cycle nor a chain,
  /// but several cycles and chains.
  /// For each such vertex v, we consider each set of polygons incident to v
  /// and sharing a non-marked edge incident to v. A copy of v is assigned to
  /// each but one set of incident polygons.
  void duplicate_singular_vertices()
  {
    // for each vertex, indicates the list of polygon containing it
    std::vector< std::vector<P_ID> > incident_polygons_per_vertex(points.size());
    fill_incident_polygons_per_vertex(polygons, incident_polygons_per_vertex);
    std::vector< std::pair<V_ID, std::vector<P_ID> > > vertices_to_duplicate;

    V_ID nbv = static_cast<V_ID>( points.size() );
    for (V_ID v_id = 0; v_id < nbv; ++v_id)
    {
      const std::vector< P_ID >& incident_polygons = incident_polygons_per_vertex[v_id];

      if ( incident_polygons.empty() ) continue; //isolated vertex
      std::set<P_ID> visited_polygons;

      std::size_t nb_link_ccs=0;
      for(P_ID p_id : incident_polygons)
      {
        if ( !visited_polygons.insert(p_id).second ) continue; // already visited

        if (++nb_link_ccs != 1)
        {
          // the vertex is non-manifold
          vertices_to_duplicate.push_back(std::pair<V_ID, std::vector<P_ID> >());
          vertices_to_duplicate.back().first=v_id;

          // call the visitor only if the function has been overridden
          if (nb_link_ccs==2 && &Visitor::link_connected_polygons != &Default_orientation_visitor::link_connected_polygons)
          {
            std::vector<std::size_t> tmp(visited_polygons.begin(), visited_polygons.end());
            tmp.erase(std::remove(tmp.begin(), tmp.end(), p_id), tmp.end());
            visitor.link_connected_polygons(v_id, tmp);
          }
        }

        const std::array<V_ID,3>& neighbors = get_neighbor_vertices(v_id,p_id,polygons);

        V_ID next = neighbors[2];

        if(nb_link_ccs != 1)
          vertices_to_duplicate.back().second.push_back(p_id);

        do{
          P_ID other_p_id;
          std::tie(next, other_p_id) = next_cw_vertex_around_source(v_id, next, polygons, edges, marked_edges);
          if (next==v_id) break;
          visited_polygons.insert(other_p_id);
          if(nb_link_ccs != 1)
            vertices_to_duplicate.back().second.push_back(other_p_id);
        }
        while(next!=neighbors[0]);

        if (next==v_id){
          /// turn the otherway round
          next = neighbors[0];
          do{
            P_ID other_p_id;
            std::tie(next, other_p_id) = next_ccw_vertex_around_target(next, v_id, polygons, edges, marked_edges);
            if (next==v_id) break;
            visited_polygons.insert(other_p_id);
            if(nb_link_ccs != 1)
              vertices_to_duplicate.back().second.push_back(other_p_id);
          }
          while(true);
        }
        if (nb_link_ccs != 1)
          visitor.link_connected_polygons(v_id, vertices_to_duplicate.back().second);
      }
      if (nb_link_ccs != 1) visitor.non_manifold_vertex(v_id, nb_link_ccs);
    }

    /// now duplicate the vertices
    typedef std::pair<V_ID, std::vector<P_ID> > V_ID_and_Polygon_ids;
    edges.resize(edges.size()+vertices_to_duplicate.size());
    for(const V_ID_and_Polygon_ids& vid_and_pids : vertices_to_duplicate)
    {
      V_ID new_index = static_cast<V_ID>(points.size());
      visitor.duplicated_vertex(vid_and_pids.first, new_index);
      points.push_back( points[vid_and_pids.first] );
      for(P_ID polygon_id : vid_and_pids.second)
        replace_vertex_index_in_polygon(polygon_id, vid_and_pids.first, new_index);
    }
  }

  static bool has_singular_vertices(
    std::size_t nb_points,
    const Polygons& polygons,
    Edge_map& edges,
    Marked_edges& marked_edges)
  {
    // for each vertex, indicates the list of polygon containing it
    std::vector< std::vector<P_ID> > incident_polygons_per_vertex(nb_points);
    fill_incident_polygons_per_vertex(polygons, incident_polygons_per_vertex);

    V_ID nbv = static_cast<V_ID>( nb_points );
    for (V_ID v_id = 0; v_id < nbv; ++v_id)
    {
      const std::vector< P_ID >& incident_polygons = incident_polygons_per_vertex[v_id];

      if ( incident_polygons.empty() ) continue; //isolated vertex
      std::set<P_ID> visited_polygons;

      bool first_pass = true;
      for(P_ID p_id : incident_polygons)
      {
        if ( !visited_polygons.insert(p_id).second ) continue; // already visited

        if (!first_pass)
          return false; //there will be duplicate vertices

        const std::array<V_ID,3>& neighbors = get_neighbor_vertices(v_id,p_id,polygons);

        V_ID next = neighbors[2];

        do{
          P_ID other_p_id;
          std::tie(next, other_p_id) = next_cw_vertex_around_source(v_id, next, polygons, edges, marked_edges);
          if (next==v_id) break;
          visited_polygons.insert(other_p_id);
        }
        while(next!=neighbors[0]);

        if (next==v_id){
          /// turn the otherway round
          next = neighbors[0];
          do{
            P_ID other_p_id;
            std::tie(next, other_p_id) = next_ccw_vertex_around_target(next, v_id, polygons, edges, marked_edges);
            if (next==v_id) break;
            visited_polygons.insert(other_p_id);
          }
          while(true);
        }
        first_pass=false;
      }
    }
    return true;
  }
};
} // namespace internal

/**
 * \ingroup PMP_orientation_grp
 *
 * \brief tries to consistently orient a soup of polygons in 3D space.
 *
 * The algorithm re-orients polygons such that the orientation
 * of adjacent polygons is consistent. Note that the adjacency is
 * defined in a combinatorial sense, i.e. two polygons are sharing
 * an edge if and only if the endpoints of this edge are represented
 * by the same point indices in both faces (possibly in a different order);
 * it is not sufficient for the points to be geometrically identical.
 * One may use `CGAL::Polygon_mesh_processing::merge_duplicate_points_in_polygon_soup()`
 * to convert geometrical point equality into combinatorial point equality.
 *
 * When it is not possible to produce a combinatorial manifold surface
 * (for example, if the polygon soup makes up a Möbius strip),
 * some points are duplicated.
 * Because a polygon soup does not have any connectivity (each point
 * has as many occurrences as the number of polygons it belongs to),
 * duplicating one point (or a pair of points)
 * amounts to duplicating the polygon to which it belongs.
 *
 * These points are either an endpoint of an edge incident to more
 * than two polygons, an endpoint of an edge between
 * two polygons with incompatible orientations (during the re-orientation process),
 * or more generally a point \a p at which the intersection
 * of an infinitesimally small ball centered at \a p
 * with the polygons incident to it is not a topological disk.
 *
 * The algorithm is described in \cgalCite{gueziec2001cutting}.
 *
 * @tparam PointRange a model of the concepts `RandomAccessContainer`
 * and `BackInsertionSequence` whose value type is the point type.
 * @tparam PolygonRange a model of the concept `RandomAccessContainer`
 * whose `value_type` is a model of the concept `RandomAccessContainer`
 * whose `value_type` is `std::size_t`.
 * \tparam NamedParameters a sequence of named parameters
 *
 * @param points points of the soup of polygons. Some additional points might be pushed back to resolve
 *               non-manifoldness or non-orientability issues.
 * @param polygons each element in the vector describes a polygon using the index of the points in `points`.
 *                 If needed the order of the indices of a polygon might be reversed.
 * @param np optional sequence of named parameters among the ones listed below
 *
 * \cgalNamedParamsBegin
 *   \cgalParamNBegin{visitor}
 *     \cgalParamDescription{a visitor used to be notified of the presence of non-manifold simplices and of the modifications done to polygons during orientation.}
 *     \cgalParamType{a class model of `PMPPolygonSoupOrientationVisitor`}
 *     \cgalParamDefault{`Default_orientation_visitor`}
 *   \cgalParamNEnd
 * \cgalNamedParamsEnd
 *
 * @return `true`  if the orientation operation succeeded.
 * @return `false` if some points were duplicated, thus producing a combinatorially manifold but self-intersecting polyhedron.
 *
 * @sa `orient_triangle_soup_with_reference_triangle_mesh()`
 */
template <class PointRange, class PolygonRange,
          class NamedParameters = parameters::Default_named_parameters>
bool orient_polygon_soup(PointRange& points,
                         PolygonRange& polygons,
                         const NamedParameters& np = parameters::default_values())
{
  using parameters::choose_parameter;
  using parameters::get_parameter;

  typedef typename internal_np::Lookup_named_param_def <
    internal_np::visitor_t,
    NamedParameters,
    Default_orientation_visitor//default
  > ::type Visitor;
  Visitor visitor(choose_parameter<Visitor>(get_parameter(np, internal_np::visitor)));
  std::size_t inital_nb_pts = points.size();
  internal::Polygon_soup_orienter<PointRange, PolygonRange, Visitor>
      orienter(points, polygons, visitor);
  orienter.fill_edge_map();
  orienter.orient();
  orienter.duplicate_singular_vertices();

  return inital_nb_pts==points.size();
}

} }//end namespace CGAL::Polygon_mesh_processing

#include <CGAL/enable_warnings.h>

#endif // CGAL_POLYGON_MESH_PROCESSING_ORIENT_POLYGON_SOUP
