/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkSymmetricEllipsoidInteriorExteriorSpatialFunction_hxx
#define itkSymmetricEllipsoidInteriorExteriorSpatialFunction_hxx

#include <cmath>

namespace itk
{
template <unsigned int VDimension, typename TInput>
SymmetricEllipsoidInteriorExteriorSpatialFunction<VDimension,
                                                  TInput>::SymmetricEllipsoidInteriorExteriorSpatialFunction()
{
  m_Center.Fill(0.0);      // Origin of ellipsoid
  m_Orientation.Fill(1.0); // Orientation of unique axis
}

template <unsigned int VDimension, typename TInput>
auto
SymmetricEllipsoidInteriorExteriorSpatialFunction<VDimension, TInput>::Evaluate(const InputType & position) const
  -> OutputType
{
  double uniqueTerm;    // Term in ellipsoid equation for unique axis
  double symmetricTerm; // Term in ellipsoid equation for symmetric axes

  Vector<double, VDimension> pointVector;
  Vector<double, VDimension> symmetricVector;

  // Project the position onto the major axis, normalize by axis length,
  // and determine whether position is inside ellipsoid.
  for (unsigned int i = 0; i < VDimension; ++i)
  {
    pointVector[i] = position[i] - m_Center[i];
  }

  uniqueTerm =
    std::pow(static_cast<double>(((pointVector * m_Orientation) / (.5 * m_UniqueAxis))), static_cast<double>(2));
  symmetricVector = pointVector - (m_Orientation * (pointVector * m_Orientation));
  symmetricTerm =
    std::pow(static_cast<double>(((symmetricVector.GetNorm()) / (.5 * m_SymmetricAxes))), static_cast<double>(2));

  if ((uniqueTerm + symmetricTerm) >= 0 && (uniqueTerm + symmetricTerm) <= 1)
  {
    return 1; // Inside the ellipsoid.
  }
  // Default return value assumes outside the ellipsoid
  return 0; // Outside the ellipsoid.
}

template <unsigned int VDimension, typename TInput>
void
SymmetricEllipsoidInteriorExteriorSpatialFunction<VDimension, TInput>::PrintSelf(std::ostream & os, Indent indent) const
{
  Superclass::PrintSelf(os, indent);

  os << indent << "Origin of Ellipsoid: ";
  os << m_Center << std::endl;
  os << indent << "Unique Axis Orientation: ";
  os << m_Orientation << std::endl;
  os << indent << "Unique Axis Length: ";
  os << m_UniqueAxis << std::endl;
  os << indent << "Symmetric Axis Length: ";
  os << m_SymmetricAxes << std::endl;
}

template <unsigned int VDimension, typename TInput>
void
SymmetricEllipsoidInteriorExteriorSpatialFunction<VDimension, TInput>::SetOrientation(VectorType orientation,
                                                                                      double     uniqueAxis,
                                                                                      double     symmetricAxes)
{
  m_Orientation = orientation;     // Orientation of unique axis of ellipsoid
  m_SymmetricAxes = symmetricAxes; // Length of symmetric axes
  m_UniqueAxis = uniqueAxis;       // Length of unique axis
}
} // end namespace itk

#endif
