// Copyright (c) 2019-2022 Google LLC (USA).
// Copyright (c) 2025 GeometryFactory (France)
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL: https://github.com/CGAL/cgal/blob/v6.2/Alpha_wrap_2/include/CGAL/Alpha_wrap_2/internal/gate_priority_queue.h $
// $Id: include/CGAL/Alpha_wrap_2/internal/gate_priority_queue.h cac3e9d75e2 $
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Pierre Alliez
//                 Cedric Portaneri,
//                 Mael Rouxel-Labbé
//                 Andreas Fabri
//                 Michael Hemmer
//
#ifndef CGAL_ALPHA_WRAP_2_INTERNAL_GATE_PRIORITY_QUEUE_H
#define CGAL_ALPHA_WRAP_2_INTERNAL_GATE_PRIORITY_QUEUE_H

#include <CGAL/license/Alpha_wrap_2.h>

#include <boost/property_map/property_map.hpp>

#include <cassert>
#include <iostream>
#include <optional>

namespace CGAL {
namespace Alpha_wraps_2 {
namespace internal {

enum class Steiner_status
{
  UNKNOWN = 0,
  NO_STEINER_POINT,
  RULE_1,
  RULE_2
};

#ifdef CGAL_AW2_COMPUTE_AND_STORE_STEINER_INFO_AT_GATE_CREATION
template <typename Tr>
struct Gate_steiner_info
{
  using Point_2 = typename Tr::Geom_traits::Point_2;

  Gate_steiner_info() : m_steiner_status(Steiner_status::UNKNOWN), m_steiner_point(std::nullopt) { }

  Steiner_status m_steiner_status;
  std::optional<Point_2> m_steiner_point;

  bool has_steiner_point() const { return m_steiner_point.has_value(); }
  bool has_steiner_from_intersection() const { return (m_steiner_status == Steiner_status::RULE_1); }
  bool has_steiner_from_projection() const { return (m_steiner_status == Steiner_status::RULE_2); }
  const Point_2& steiner_point() const {
    CGAL_precondition(has_steiner_point());
    return *m_steiner_point;
  }
};
#endif

#ifdef CGAL_AW2_USE_SORTED_PRIORITY_QUEUE

// Represents an alpha-traversable edge in the mutable priority queue
template <typename Tr>
class Gate
#ifdef CGAL_AW2_COMPUTE_AND_STORE_STEINER_INFO_AT_GATE_CREATION
  : public Gate_steiner_info<Tr>
#endif
{
  using Edge = typename Tr::Edge;
  using FT = typename Tr::Geom_traits::FT;

private:
  Edge m_edge;
  FT m_priority; // circumcircle sq_radius
  bool m_is_permissive_edge;

public:
  // Constructors
  Gate(const Edge& edge,
       const FT& priority,
       const bool is_permissive_edge)
    :
      m_edge(edge),
      m_priority(priority),
      m_is_permissive_edge(is_permissive_edge)
  {
    CGAL_assertion(priority >= 0);
  }

  // This overload is only used for contains() and erase(), priority and bbox flag are dummy value
  Gate(const Edge& edge)
    : Gate(edge, 0, false)
  { }

public:
  const Edge& edge() const { return m_edge; }
  const FT& priority() const { return m_priority; }
  bool is_permissive_edge() const { return m_is_permissive_edge; }
};

struct Less_gate
{
  template <typename Tr>
  bool operator()(const Gate<Tr>& a, const Gate<Tr>& b) const
  {
    // If one is permissive and the other is not, give priority to the permissive edge.
    //
    // The permissive edge are given highest priority because they need to be treated
    // regardless of their circumradius. Treating them first allow the part that depends
    // on alpha to be treated uniformly in a way: whatever the alpha, all permissive faces
    // will first be treated.
    if(a.is_permissive_edge() != b.is_permissive_edge())
      return a.is_permissive_edge();

    if(a.priority() == b.priority())
    {
      // arbitrary, the sole purpose is to make it a total order for determinism
      if(a.edge().first->time_stamp() == b.edge().first->time_stamp())
        return a.edge().second < b.edge().second;

      return a.edge().first->time_stamp() < b.edge().first->time_stamp();
    }

    return a.priority() > b.priority();
  }
};

#else // CGAL_AW2_USE_SORTED_PRIORITY_QUEUE

// Represents an alpha-traversable edge in the mutable priority queue
template <typename Tr>
class Gate
#ifdef CGAL_AW2_COMPUTE_AND_STORE_STEINER_INFO_AT_GATE_CREATION
  : public Gate_steiner_info<Tr>
#endif
{
  using Edge = typename Tr::Edge;
  using FT = typename Tr::Geom_traits::FT;

private:
  Edge m_edge, m_mirror_edge;
  const unsigned int m_erase_counter_mem;
  const unsigned int m_mirror_erase_counter_mem;

public:
  // Constructors
  Gate(const Edge& edge,
       const Tr& tr)
    :
      m_edge(edge),
      m_mirror_edge(tr.mirror_edge(edge)),
      m_erase_counter_mem(m_edge.first->erase_counter()),
      m_mirror_erase_counter_mem(m_mirror_edge.first->erase_counter())
  {
  }

public:
  const Edge& edge() const { return m_edge; }

  bool is_zombie() const
  {
#ifdef CGAL_AW2_DEBUG_PP
    std::cout << "Zombie check of " << std::endl;
    std::cout << "  " << &*(m_edge.first) << ": " << m_edge.first->erase_counter() << " " << m_erase_counter_mem << std::endl;
    std::cout << "  " << &*(m_mirror_edge.first) << ": " << m_mirror_edge.first->erase_counter() << " " << m_mirror_erase_counter_mem << std::endl;
#endif

    return (m_edge.first->erase_counter() != m_erase_counter_mem) ||
           (m_mirror_edge.first->erase_counter() != m_mirror_erase_counter_mem);
  }
};

#endif // CGAL_AW2_USE_SORTED_PRIORITY_QUEUE

template <typename Tr>
struct Gate_ID_PM
{
  using key_type = Gate<Tr>;
  using value_type = std::size_t;
  using reference = std::size_t;
  using category = boost::readable_property_map_tag;

  inline friend value_type get(Gate_ID_PM, const key_type& k)
  {
    using Edge = typename Tr::Edge;

    const Edge& f = k.edge();
    return (3 * f.first->time_stamp() + f.second);
  }
};

} // namespace internal
} // namespace Alpha_wraps_2
} // namespace CGAL

#endif // CGAL_ALPHA_WRAP_2_INTERNAL_GATE_PRIORITY_QUEUE_H
