#ifndef COORDINATES_H
#define COORDINATES_H

/// Coordinate types and rotations for molecular orientations on the unit sphere.
namespace coordinates {

/// Spherical position stored as (cos_theta, phi) to avoid repeated cos/acos.
struct SphericalPos {
  double cos_theta;
  double phi;
};

struct CartesianPos {
  double x;
  double y;
  double z;
};

/// Rotate a spherical position by polar angle alpha around an axis defined
/// by azimuthal angle beta (rotation about the original position's z-axis).
SphericalPos rotate(const SphericalPos &, double alpha, double beta);

CartesianPos spherical_to_xyz(const SphericalPos &);
SphericalPos xyz_to_spherical(const CartesianPos &);
} // namespace coordinates

#endif // COORDINATES_H