#pragma once

#include "BoundingVolume.h"
#include "Library.h"

#include <CesiumGeometry/CullingVolume.h>
#include <CesiumGeometry/Plane.h>
#include <CesiumGeospatial/Cartographic.h>
#include <CesiumGeospatial/Ellipsoid.h>

#include <glm/mat3x3.hpp>
#include <glm/vec2.hpp>
#include <glm/vec3.hpp>

#include <vector>

namespace Cesium3DTilesSelection {

/**
 * @brief The state of the view that is used during the traversal of a tileset.
 *
 * An instance of a view state can be created with the {@link create} function.
 */
class CESIUM3DTILESSELECTION_API ViewState final {

  // TODO: Add support for orthographic and off-center perspective frustums
public:
  /**
   * @brief Creates a new instance of a view state.
   *
   * @param position The position of the eye point of the camera.
   * @param direction The view direction vector of the camera.
   * @param up The up vector of the camera.
   * @param viewportSize The size of the viewport, in pixels.
   * @param horizontalFieldOfView The horizontal field-of-view (opening)
   * angle of the camera, in radians.
   * @param verticalFieldOfView The vertical field-of-view (opening)
   * angle of the camera, in radians.
   * @param ellipsoid The ellipsoid that will be used to compute the
   * {@link ViewState#getPositionCartographic cartographic position}
   * from the cartesian position.
   * Default value: {@link CesiumGeospatial::Ellipsoid::WGS84}.
   */
  static ViewState create(
      const glm::dvec3& position,
      const glm::dvec3& direction,
      const glm::dvec3& up,
      const glm::dvec2& viewportSize,
      double horizontalFieldOfView,
      double verticalFieldOfView,
      const CesiumGeospatial::Ellipsoid& ellipsoid CESIUM_DEFAULT_ELLIPSOID);

  /**
   * @brief Gets the position of the camera in Earth-centered, Earth-fixed
   * coordinates.
   */
  const glm::dvec3& getPosition() const noexcept { return this->_position; }

  /**
   * @brief Gets the look direction of the camera in Earth-centered, Earth-fixed
   * coordinates.
   */
  const glm::dvec3& getDirection() const noexcept { return this->_direction; }

  /**
   * @brief Gets the up direction of the camera in Earth-centered, Earth-fixed
   * coordinates.
   */
  const glm::dvec3& getUp() const noexcept { return this->_up; }

  /**
   * @brief Gets the position of the camera as a longitude / latitude / height.
   *
   * The result may be `std::nullopt` if the Cartesian position is
   * very near the center of the Ellipsoid.
   */
  const std::optional<CesiumGeospatial::Cartographic>&
  getPositionCartographic() const noexcept {
    return this->_positionCartographic;
  }

  /**
   * @brief Gets the size of the viewport in pixels.
   */
  const glm::dvec2& getViewportSize() const noexcept {
    return this->_viewportSize;
  }

  /**
   * @brief Gets the horizontal field-of-view angle in radians.
   */
  double getHorizontalFieldOfView() const noexcept {
    return this->_horizontalFieldOfView;
  }

  /**
   * @brief Gets the vertical field-of-view angle in radians.
   */
  double getVerticalFieldOfView() const noexcept {
    return this->_verticalFieldOfView;
  }

  /**
   * @brief Returns whether the given {@link BoundingVolume} is visible for this
   * camera
   *
   * Returns whether the given bounding volume is visible for this camera,
   * meaning that the given volume is at least partially contained in
   * the frustum of this camera.
   *
   * @return Whether the bounding volume is visible
   */
  bool
  isBoundingVolumeVisible(const BoundingVolume& boundingVolume) const noexcept;

  /**
   * @brief Computes the squared distance to the given {@link BoundingVolume}.
   *
   * Computes the squared euclidean distance from the position of this camera
   * to the closest point of the given bounding volume.
   *
   * @param boundingVolume The bounding volume
   * @returns The squared distance
   */
  double computeDistanceSquaredToBoundingVolume(
      const BoundingVolume& boundingVolume) const noexcept;

  /**
   * @brief Computes the screen space error from a given geometric error
   *
   * Computes the screen space error (SSE) that results from the given
   * geometric error, when it is viewed with this camera from the given
   * distance.
   *
   * The given distance will be clamped to a small positive value if
   * it is negative or too close to zero.
   *
   * @param geometricError The geometric error
   * @param distance The viewing distance
   * @return The screen space error
   */
  double computeScreenSpaceError(double geometricError, double distance)
      const noexcept;

private:
  /**
   * @brief Creates a new instance.
   *
   * @param position The position of the eye point of the camera.
   * @param direction The view direction vector of the camera.
   * @param up The up vector of the camera.
   * @param viewportSize The size of the viewport, in pixels.
   * @param horizontalFieldOfView The horizontal field-of-view (opening)
   * angle of the camera, in radians.
   * @param verticalFieldOfView The vertical field-of-view (opening)
   * angle of the camera, in radians.
   */
  ViewState(
      const glm::dvec3& position,
      const glm::dvec3& direction,
      const glm::dvec3& up,
      const glm::dvec2& viewportSize,
      double horizontalFieldOfView,
      double verticalFieldOfView,
      const std::optional<CesiumGeospatial::Cartographic>& positionCartographic,
      const CesiumGeospatial::Ellipsoid& ellipsoid);

  const glm::dvec3 _position;
  const glm::dvec3 _direction;
  const glm::dvec3 _up;
  const glm::dvec2 _viewportSize;
  const double _horizontalFieldOfView;
  const double _verticalFieldOfView;
  const CesiumGeospatial::Ellipsoid _ellipsoid;

  const double _sseDenominator;
  const std::optional<CesiumGeospatial::Cartographic> _positionCartographic;

  const CullingVolume _cullingVolume;
};

} // namespace Cesium3DTilesSelection