#pragma once

#include "geometry/parametrized_segment.hpp"
#include "geometry/point2d.hpp"
#include "geometry/rect2d.hpp"

#include "base/logging.hpp"
#include "base/math.hpp"

#include <algorithm>
#include <random>
#include <type_traits>
#include <utility>
#include <vector>

namespace m2
{
namespace detail
{
struct DefEqualFloat
{
  // 1e-9 is two orders of magnitude more accurate than our OSM source data.
  static double constexpr kPrecision = 1e-9;

  template <typename Point>
  bool EqualPoints(Point const & p1, Point const & p2) const
  {
    static_assert(std::is_floating_point<typename Point::value_type>::value, "");

    return base::AlmostEqualAbs(p1.x, p2.x, static_cast<typename Point::value_type>(kPrecision)) &&
           base::AlmostEqualAbs(p1.y, p2.y, static_cast<typename Point::value_type>(kPrecision));
  }

  template <typename Coord>
  bool EqualZeroSquarePrecision(Coord val) const
  {
    static_assert(std::is_floating_point<Coord>::value, "");

    return base::AlmostEqualAbs(val, 0.0, kPrecision * kPrecision);
  }
  // Determines if value of a val lays between a p1 and a p2 values with some precision.
  bool IsAlmostBetween(double val, double p1, double p2) const
  {
    return (val >= p1 - kPrecision && val <= p2 + kPrecision) ||
           (val <= p1 + kPrecision && val >= p2 - kPrecision);
  }
};

struct DefEqualInt
{
  template <typename Point>
  bool EqualPoints(Point const & p1, Point const & p2) const
  {
    return p1 == p2;
  }

  template <typename Coord>
  bool EqualZeroSquarePrecision(Coord val) const
  {
    return val == 0;
  }

  bool IsAlmostBetween(double val, double left, double right) const
  {
    return (val >= left && val <= right) || (val <= left && val >= right);
  }
};

template <int floating>
struct Traitsype;

template <>
struct Traitsype<1>
{
  typedef DefEqualFloat EqualType;
  typedef double BigType;
};

template <>
struct Traitsype<0>
{
  typedef DefEqualInt EqualType;
  typedef int64_t BigType;
};
}  // namespace detail

template <typename Point>
class Region
{
public:
  using Value = Point;
  using Coord = typename Point::value_type;
  using Container = std::vector<Point>;
  using Traits = detail::Traitsype<std::is_floating_point<Coord>::value>;

  /// @name Needed for boost region concept.
  //@{
  using IteratorT = typename Container::const_iterator;
  IteratorT Begin() const { return m_points.begin(); }
  IteratorT End() const { return m_points.end(); }
  size_t Size() const { return m_points.size(); }
  //@}

  Region() = default;

  template <typename Points,
            typename = std::enable_if_t<std::is_constructible<Container, Points>::value>>
  explicit Region(Points && points) : m_points(std::forward<Points>(points))
  {
    CalcLimitRect();
  }

  template <typename Iter>
  Region(Iter first, Iter last) : m_points(first, last)
  {
    CalcLimitRect();
  }

  template <typename Iter>
  void Assign(Iter first, Iter last)
  {
    m_points.assign(first, last);
    CalcLimitRect();
  }

  template <typename Iter, typename Fn>
  void AssignEx(Iter first, Iter last, Fn fn)
  {
    m_points.reserve(distance(first, last));

    while (first != last)
      m_points.push_back(fn(*first++));

    CalcLimitRect();
  }

  void AddPoint(Point const & pt)
  {
    m_points.push_back(pt);
    m_rect.Add(pt);
  }

  template <typename ToDo>
  void ForEachPoint(ToDo && toDo) const
  {
    for_each(m_points.begin(), m_points.end(), std::forward<ToDo>(toDo));
  }

  m2::Rect<Coord> const & GetRect() const { return m_rect; }
  size_t GetPointsCount() const { return m_points.size(); }
  bool IsValid() const { return GetPointsCount() > 2; }

  void Swap(Region<Point> & rhs)
  {
    m_points.swap(rhs.m_points);
    std::swap(m_rect, rhs.m_rect);
  }

  Container const & Data() const { return m_points; }

  template <typename EqualFn>
  static bool IsIntersect(Coord const & x11, Coord const & y11, Coord const & x12,
                          Coord const & y12, Coord const & x21, Coord const & y21,
                          Coord const & x22, Coord const & y22, EqualFn && equalF, Point & pt)
  {
    double const divider = ((y12 - y11) * (x22 - x21) - (x12 - x11) * (y22 - y21));
    if (equalF.EqualZeroSquarePrecision(divider))
      return false;
    double v = ((x12 - x11) * (y21 - y11) + (y12 - y11) * (x11 - x21)) / divider;
    Point p(x21 + (x22 - x21) * v, y21 + (y22 - y21) * v);

    if (!equalF.IsAlmostBetween(p.x, x11, x12))
      return false;
    if (!equalF.IsAlmostBetween(p.x, x21, x22))
      return false;
    if (!equalF.IsAlmostBetween(p.y, y11, y12))
      return false;
    if (!equalF.IsAlmostBetween(p.y, y21, y22))
      return false;

    pt = p;
    return true;
  }

  static bool IsIntersect(Point const & p1, Point const & p2, Point const & p3, Point const & p4,
                          Point & pt)
  {
    return IsIntersect(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, typename Traits::EqualType(),
                       pt);
  }

  /// Taken from Computational Geometry in C and modified
  template <typename EqualFn>
  bool Contains(Point const & pt, EqualFn equalF) const
  {
    if (!m_rect.IsPointInside(pt))
      return false;

    int rCross = 0; /* number of right edge/ray crossings */
    int lCross = 0; /* number of left edge/ray crossings */

    size_t const numPoints = m_points.size();

    using BigCoord = typename Traits::BigType;
    using BigPoint = ::m2::Point<BigCoord>;

    BigPoint prev = BigPoint(m_points[numPoints - 1]) - BigPoint(pt);
    for (size_t i = 0; i < numPoints; ++i)
    {
      if (equalF.EqualPoints(m_points[i], pt))
        return true;

      BigPoint const curr = BigPoint(m_points[i]) - BigPoint(pt);

      bool const rCheck = ((curr.y > 0) != (prev.y > 0));
      bool const lCheck = ((curr.y < 0) != (prev.y < 0));

      if (rCheck || lCheck)
      {
        ASSERT_NOT_EQUAL(curr.y, prev.y, ());

        BigCoord const delta = prev.y - curr.y;
        BigCoord const cp = CrossProduct(curr, prev);

        // Squared precision is needed here because of comparison between cross product of two
        // std::vectors and zero. It's impossible to compare them relatively, so they're compared
        // absolutely, and, as cross product is proportional to product of lengths of both
        // operands precision must be squared too.
        if (!equalF.EqualZeroSquarePrecision(cp))
        {
          bool const PrevGreaterCurr = delta > 0.0;

          if (rCheck && ((cp > 0) == PrevGreaterCurr))
            ++rCross;
          if (lCheck && ((cp > 0) != PrevGreaterCurr))
            ++lCross;
        }
      }

      prev = curr;
    }

    /* q on the edge if left and right cross are not the same parity. */
    if ((rCross & 1) != (lCross & 1))
      return true;  // on the edge

    /* q inside if an odd number of crossings. */
    if (rCross & 1)
      return true;  // inside
    else
      return false;  // outside
  }

  bool Contains(Point const & pt) const { return Contains(pt, typename Traits::EqualType()); }

  /// Finds point of intersection with the section.
  bool FindIntersection(Point const & point1, Point const & point2, Point & result) const
  {
    if (m_points.empty())
      return false;
    Point const * prev = &m_points.back();
    for (Point const & curr : m_points)
    {
      if (IsIntersect(point1, point2, *prev, curr, result))
        return true;
      prev = &curr;
    }
    return false;
  }

  /// Slow check that point lies at the border.
  template <typename EqualFn>
  bool AtBorder(Point const & pt, double const delta, EqualFn equalF) const
  {
    auto const rectDelta = static_cast<Coord>(delta);
    if (!Inflate(m_rect, rectDelta, rectDelta).IsPointInside(pt))
      return false;

    const double squaredDelta = delta * delta;
    size_t const numPoints = m_points.size();

    Point prev = m_points[numPoints - 1];

    for (size_t i = 0; i < numPoints; ++i)
    {
      Point const curr = m_points[i];

      // Borders often have same points with ways
      if (equalF.EqualPoints(m_points[i], pt))
        return true;

      ParametrizedSegment<Point> segment(prev, curr);
      if (segment.SquaredDistanceToPoint(pt) < squaredDelta)
        return true;

      prev = curr;
    }

    return false;  // Point lies outside the border.
  }

  bool AtBorder(Point const & pt, double const delta) const
  {
    return AtBorder(pt, delta, typename Traits::EqualType());
  }

  double CalculateArea() const
  {
    double area = 0.0;

    if (m_points.empty())
      return area;

    size_t const numPoints = m_points.size();
    Point prev = m_points[numPoints - 1];
    for (size_t i = 0; i < numPoints; ++i)
    {
      Point const curr = m_points[i];
      area += CrossProduct(prev, curr);
      prev = curr;
    }
    area = 0.5 * std::fabs(area);

    return area;
  }

  template <typename Engine>
  Point GetRandomPoint(Engine & engine) const
  {
    CHECK(m_rect.IsValid(), ());
    CHECK(!m_rect.IsEmptyInterior(), ());

    std::uniform_real_distribution<> distrX(m_rect.minX(), m_rect.maxX());
    std::uniform_real_distribution<> distrY(m_rect.minY(), m_rect.maxY());

    size_t const kMaxIterations = 1000;
    for (size_t it = 0; it < kMaxIterations; ++it)
    {
      auto const x = distrX(engine);
      auto const y = distrY(engine);
      Point const pt(x, y);
      if (Contains(pt))
        return pt;
    }

    LOG(LWARNING, ("Could not sample a random point from m2::Region"));
    return m_points[0];
  }

private:
  template <typename Archive, typename Pt>
  friend Archive & operator<<(Archive & ar, Region<Pt> const & region);

  template <typename Archive, typename Pt>
  friend Archive & operator>>(Archive & ar, Region<Pt> & region);

  template <typename T>
  friend std::string DebugPrint(Region<T> const &);

  void CalcLimitRect()
  {
    m_rect.MakeEmpty();
    for (size_t i = 0; i < m_points.size(); ++i)
      m_rect.Add(m_points[i]);
  }

  Container m_points;
  m2::Rect<Coord> m_rect;
};

template <typename Point>
void swap(Region<Point> & r1, Region<Point> & r2)
{
  r1.Swap(r2);
}

template <typename Archive, typename Point>
Archive & operator>>(Archive & ar, Region<Point> & region)
{
  ar >> region.m_rect;
  ar >> region.m_points;
  return ar;
}

template <typename Archive, typename Point>
Archive & operator<<(Archive & ar, Region<Point> const & region)
{
  ar << region.m_rect;
  ar << region.m_points;
  return ar;
}

template <typename Point>
std::string DebugPrint(Region<Point> const & r)
{
  return (DebugPrint(r.m_rect) + ::DebugPrint(r.m_points));
}

template <typename Point>
bool RegionsContain(std::vector<Region<Point>> const & regions, Point const & point)
{
  for (auto const & region : regions)
  {
    if (region.Contains(point))
      return true;
  }

  return false;
}

using RegionD = Region<m2::PointD>;
using RegionI = Region<m2::PointI>;
using RegionU = Region<m2::PointU>;
}  // namespace m2