/**
BSD 3-Clause License

This file is part of the Basalt project.
https://gitlab.com/VladyslavUsenko/basalt-headers.git

Copyright (c) 2019, Vladyslav Usenko and Nikolaus Demmel.
All rights reserved.

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modification, are permitted provided that the following conditions are met:

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  list of conditions and the following disclaimer.

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  this software without specific prior written permission.

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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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@file
@brief Implementation of generic camera model
*/

#pragma once

#include <basalt/camera/bal_camera.hpp>
#include <basalt/camera/double_sphere_camera.hpp>
#include <basalt/camera/extended_camera.hpp>
#include <basalt/camera/fov_camera.hpp>
#include <basalt/camera/kannala_brandt_camera4.hpp>
#include <basalt/camera/pinhole_camera.hpp>
#include <basalt/camera/unified_camera.hpp>

#include <variant>

namespace basalt {

using std::sqrt;

/// @brief Generic camera model that can store different camera models
///
/// Particular class of camera model is stored as \ref variant and can be casted
/// to specific type using std::visit.
template <typename Scalar_>
class GenericCamera {
  using Scalar = Scalar_;

  using Vec2 = Eigen::Matrix<Scalar, 2, 1>;
  using Vec3 = Eigen::Matrix<Scalar, 3, 1>;
  using Vec4 = Eigen::Matrix<Scalar, 4, 1>;
  using VecX = Eigen::Matrix<Scalar, Eigen::Dynamic, 1>;

  using Mat24 = Eigen::Matrix<Scalar, 2, 4>;
  using Mat42 = Eigen::Matrix<Scalar, 4, 2>;
  using Mat4 = Eigen::Matrix<Scalar, 4, 4>;

  using VariantT =
      std::variant<ExtendedUnifiedCamera<Scalar>, DoubleSphereCamera<Scalar>,
                   KannalaBrandtCamera4<Scalar>, UnifiedCamera<Scalar>,
                   PinholeCamera<Scalar>>;  ///< Possible variants of camera
                                            ///< models.

 public:
  /// @brief Cast to different scalar type
  template <typename Scalar2>
  inline GenericCamera<Scalar2> cast() const {
    GenericCamera<Scalar2> res;
    std::visit([&](const auto& v) { res.variant = v.template cast<Scalar2>(); },
               variant);
    return res;
  }

  /// @brief Number of intrinsic parameters
  inline int getN() const {
    int res;
    std::visit([&](const auto& v) { res = v.N; }, variant);
    return res;
  }

  /// @brief Camera model name
  inline std::string getName() const {
    std::string res;
    std::visit([&](const auto& v) { res = v.getName(); }, variant);
    return res;
  }

  /// @brief Set parameters from initialization
  ///
  /// @param[in] init vector [fx, fy, cx, cy]
  inline void setFromInit(const Vec4& init) {
    std::visit([&](auto& v) { return v.setFromInit(init); }, variant);
  }

  /// @brief Increment intrinsic parameters by inc and if necessary clamp the
  /// values to the valid range
  inline void applyInc(const VecX& inc) {
    std::visit([&](auto& v) { return v += inc; }, variant);
  }

  /// @brief Returns a vector of intrinsic parameters
  ///
  /// The order of parameters depends on the stored model.
  /// @return vector of intrinsic parameters vector
  inline VecX getParam() const {
    VecX res;
    std::visit([&](const auto& cam) { res = cam.getParam(); }, variant);
    return res;
  }

  /// @brief Project a single point and optionally compute Jacobian
  ///
  /// **SLOW** function, as it requires vtable lookup for every projection.
  ///
  /// @param[in] p3d point to project
  /// @param[out] proj result of projection
  /// @param[out] d_proj_d_p3d if not nullptr computed Jacobian of projection
  /// with respect to p3d
  /// @return if projection is valid
  template <typename DerivedJ3DPtr = std::nullptr_t>
  inline bool project(const Vec4& p3d, Vec2& proj,
                      DerivedJ3DPtr d_proj_d_p3d = nullptr) const {
    if constexpr (!std::is_same_v<DerivedJ3DPtr, std::nullptr_t>) {
      static_assert(std::is_pointer_v<DerivedJ3DPtr>);
      using DerivedJ3D = typename std::remove_pointer<DerivedJ3DPtr>::type;
      EIGEN_STATIC_ASSERT_MATRIX_SPECIFIC_SIZE(DerivedJ3D, 2, 4);
    }

    bool res;
    std::visit(
        [&](const auto& cam) { res = cam.project(p3d, proj, d_proj_d_p3d); },
        variant);
    return res;
  }

  /// @brief Unproject a single point and optionally compute Jacobian
  ///
  /// **SLOW** function, as it requires vtable lookup for every unprojection.
  ///
  /// @param[in] proj point to unproject
  /// @param[out] p3d result of unprojection
  /// @param[out] d_p3d_d_proj if not nullptr computed Jacobian of unprojection
  /// with respect to proj
  /// @return if unprojection is valid
  template <typename DerivedJ2DPtr = std::nullptr_t>
  inline bool unproject(const Vec2& proj, Vec4& p3d,
                        DerivedJ2DPtr d_p3d_d_proj = nullptr) const {
    if constexpr (!std::is_same_v<DerivedJ2DPtr, std::nullptr_t>) {
      static_assert(std::is_pointer_v<DerivedJ2DPtr>);
      using DerivedJ2D = typename std::remove_pointer<DerivedJ2DPtr>::type;
      EIGEN_STATIC_ASSERT_MATRIX_SPECIFIC_SIZE(DerivedJ2D, 4, 2);
    }

    bool res;
    std::visit(
        [&](const auto& cam) { res = cam.unproject(proj, p3d, d_p3d_d_proj); },
        variant);
    return res;
  }

  /// @brief Project a single point and optionally compute Jacobian
  ///
  /// **SLOW** function, as it requires vtable lookup for every projection.
  ///
  /// @param[in] p3d point to project
  /// @param[out] proj result of projection
  /// @param[out] d_proj_d_p3d if not nullptr computed Jacobian of projection
  /// with respect to p3d
  /// @return if projection is valid
  template <typename DerivedJ3DPtr = std::nullptr_t>
  inline bool project(const Vec3& p3d, Vec2& proj,
                      DerivedJ3DPtr d_proj_d_p3d = nullptr) const {
    if constexpr (!std::is_same_v<DerivedJ3DPtr, std::nullptr_t>) {
      static_assert(std::is_pointer_v<DerivedJ3DPtr>);
      using DerivedJ3D = typename std::remove_pointer<DerivedJ3DPtr>::type;
      EIGEN_STATIC_ASSERT_MATRIX_SPECIFIC_SIZE(DerivedJ3D, 2, 3);
    }

    bool res;
    std::visit(
        [&](const auto& cam) { res = cam.project(p3d, proj, d_proj_d_p3d); },
        variant);
    return res;
  }

  /// @brief Unproject a single point and optionally compute Jacobian
  ///
  /// **SLOW** function, as it requires vtable lookup for every unprojection.
  ///
  /// @param[in] proj point to unproject
  /// @param[out] p3d result of unprojection
  /// @param[out] d_p3d_d_proj if not nullptr computed Jacobian of unprojection
  /// with respect to proj
  /// @return if unprojection is valid
  template <typename DerivedJ2DPtr = std::nullptr_t>
  inline bool unproject(const Vec2& proj, Vec3& p3d,
                        DerivedJ2DPtr d_p3d_d_proj = nullptr) const {
    if constexpr (!std::is_same_v<DerivedJ2DPtr, std::nullptr_t>) {
      static_assert(std::is_pointer_v<DerivedJ2DPtr>);
      using DerivedJ2D = typename std::remove_pointer<DerivedJ2DPtr>::type;
      EIGEN_STATIC_ASSERT_MATRIX_SPECIFIC_SIZE(DerivedJ2D, 3, 2);
    }

    bool res;
    std::visit(
        [&](const auto& cam) { res = cam.unproject(proj, p3d, d_p3d_d_proj); },
        variant);
    return res;
  }

  /// @brief Project a vector of points
  ///
  /// @param[in] p3d points to project
  /// @param[in] T_c_w transformation from world to camera frame that should be
  /// applied to points before projection
  /// @param[out] proj results of projection
  /// @param[out] proj_success if projection is valid
  inline void project(const Eigen::aligned_vector<Vec3>& p3d, const Mat4& T_c_w,
                      Eigen::aligned_vector<Vec2>& proj,
                      std::vector<bool>& proj_success) const {
    std::visit(
        [&](const auto& cam) {
          proj.resize(p3d.size());
          proj_success.resize(p3d.size());
          for (size_t i = 0; i < p3d.size(); i++) {
            proj_success[i] =
                cam.project(T_c_w * p3d[i].homogeneous(), proj[i]);
          }
        },
        variant);
  }

  /// @brief Project a vector of points
  ///
  /// @param[in] p3d points to project
  /// @param[in] T_c_w transformation from world to camera frame that should be
  /// applied to points before projection
  /// @param[out] proj results of projection
  /// @param[out] proj_success if projection is valid
  inline void project(const Eigen::aligned_vector<Vec4>& p3d, const Mat4& T_c_w,
                      Eigen::aligned_vector<Vec2>& proj,
                      std::vector<bool>& proj_success) const {
    std::visit(
        [&](const auto& cam) {
          proj.resize(p3d.size());
          proj_success.resize(p3d.size());
          for (size_t i = 0; i < p3d.size(); i++) {
            proj_success[i] = cam.project(T_c_w * p3d[i], proj[i]);
          }
        },
        variant);
  }

  /// @brief Project a vector of points
  ///
  /// @param[in] p3d points to project
  /// @param[out] proj results of projection
  /// @param[out] proj_success if projection is valid
  inline void project(const Eigen::aligned_vector<Vec4>& p3d,
                      Eigen::aligned_vector<Vec2>& proj,
                      std::vector<bool>& proj_success) const {
    std::visit(
        [&](const auto& cam) {
          proj.resize(p3d.size());
          proj_success.resize(p3d.size());
          for (size_t i = 0; i < p3d.size(); i++) {
            proj_success[i] = cam.project(p3d[i], proj[i]);
          }
        },
        variant);
  }

  /// @brief Project a vector of points, compute polar and azimuthal angles
  ///
  /// @param[in] p3d points to project
  /// @param[in] T_c_w transformation from world to camera frame that should be
  /// applied to points before projection
  /// @param[out] proj results of projection
  /// @param[out] proj_success if projection is valid
  inline void project(
      const Eigen::aligned_vector<Vec4>& p3d, const Mat4& T_c_w,
      Eigen::aligned_vector<Vec2>& proj, std::vector<bool>& proj_success,
      Eigen::aligned_vector<Vec2>& polar_azimuthal_angle) const {
    std::visit(
        [&](const auto& cam) {
          proj.resize(p3d.size());
          proj_success.resize(p3d.size());
          polar_azimuthal_angle.resize(p3d.size());
          for (size_t i = 0; i < p3d.size(); i++) {
            Vec4 p3dt = T_c_w * p3d[i];

            proj_success[i] = cam.project(p3dt, proj[i]);

            Scalar r2 = p3dt[0] * p3dt[0] + p3dt[1] * p3dt[1];
            Scalar r = std::sqrt(r2);
            polar_azimuthal_angle[i][0] = std::atan2(r, p3dt[2]);
            polar_azimuthal_angle[i][1] = std::atan2(p3dt[0], p3dt[1]);
          }
        },
        variant);
  }

  /// @brief Unproject a vector of points
  ///
  /// @param[in] proj points to unproject
  /// @param[out] p3d results of unprojection
  /// @param[out] unproj_success if unprojection is valid
  inline void unproject(const Eigen::aligned_vector<Vec2>& proj,
                        Eigen::aligned_vector<Vec4>& p3d,
                        std::vector<bool>& unproj_success) const {
    std::visit(
        [&](const auto& cam) {
          p3d.resize(proj.size());
          unproj_success.resize(proj.size());
          for (size_t i = 0; i < p3d.size(); i++) {
            unproj_success[i] = cam.unproject(proj[i], p3d[i]);
          }
        },
        variant);
  }

  /// @brief Construct a particular type of camera model from name
  static GenericCamera<Scalar> fromString(const std::string& name) {
    GenericCamera<Scalar> res;

    constexpr size_t VARIANT_SIZE = std::variant_size<VariantT>::value;
    visitAllTypes<VARIANT_SIZE - 1>(res, name);

    return res;
  }

  VariantT variant;

 private:
  /// @brief Iterate over all possible types of the variant and construct that
  /// type that has a matching name
  template <int I>
  static void visitAllTypes(GenericCamera<Scalar>& res,
                            const std::string& name) {
    if constexpr (I >= 0) {
      using cam_t = typename std::variant_alternative<I, VariantT>::type;
      if (cam_t::getName() == name) {
        cam_t val;
        res.variant = val;
      }
      visitAllTypes<I - 1>(res, name);
    }
  }
};
}  // namespace basalt