/*
 * Copyright (C) 2005-2022 Centre National d'Etudes Spatiales (CNES)
 *
 * This file is part of Orfeo Toolbox
 *
 *     https://www.orfeo-toolbox.org/
 *
 * 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
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 otbReciprocalBarnesDecompImageFilter_h
#define otbReciprocalBarnesDecompImageFilter_h

#include "otbMath.h"
#include "vnl/algo/vnl_complex_eigensystem.h"
#include <algorithm>

#include "otbFunctorImageFilter.h"

namespace otb
{

namespace Functor
{

/** \class otbBarnesDecompFunctor
 *
 * \brief Evaluate the Huynen decomposition from the reciprocal Sinclair matrix image.
 *
 * Use otb::BarnesDecompImageFilter to apply
 *
 * \ingroup OTBPolarimetry
 */
template <class TInput, class TOutput>
class ReciprocalBarnesDecompFunctor
{
public:
  typedef typename std::complex<double> ComplexType;
  typedef vnl_matrix<ComplexType>       VNLMatrixType;
  typedef vnl_vector<ComplexType>       VNLVectorType;
  typedef vnl_vector<double>            VNLDoubleVectorType;
  typedef std::vector<double>           VectorType;
  typedef typename TOutput::ValueType   OutputValueType;

  inline void operator()(TOutput& result, const TInput& Covariance) const
  {

    VNLMatrixType qi(3, 1);


    VNLMatrixType cov(3, 3);
    cov[0][0] = ComplexType(Covariance[0]);
    cov[0][1] = ComplexType(Covariance[1]);
    cov[0][2] = ComplexType(Covariance[2]);
    cov[1][0] = std::conj(ComplexType(Covariance[1]));
    cov[1][1] = ComplexType(Covariance[3]);
    cov[1][2] = ComplexType(Covariance[4]);
    cov[2][0] = std::conj(ComplexType(Covariance[2]));
    cov[2][1] = std::conj(ComplexType(Covariance[4]));
    cov[2][2] = ComplexType(Covariance[5]);


    qi[0][0]           = ComplexType(1., 0.);
    qi[1][0]           = ComplexType(0., 0.);
    qi[2][0]           = ComplexType(0., 0.);
    ComplexType   norm = (qi.conjugate_transpose() * cov * qi)[0][0];
    VNLMatrixType ki   = cov * qi / std::sqrt(norm);
    result[0]          = static_cast<OutputValueType>(ki[0][0]);
    result[1]          = static_cast<OutputValueType>(ki[1][0]);
    result[2]          = static_cast<OutputValueType>(ki[2][0]);


    qi[0][0]  = ComplexType(0., 0.);
    qi[1][0]  = ComplexType(1. / std::sqrt(2.), 0.);
    qi[2][0]  = ComplexType(0., 1. / std::sqrt(2.));
    norm      = (qi.conjugate_transpose() * cov * qi)[0][0];
    ki        = cov * qi / std::sqrt(norm);
    result[3] = static_cast<OutputValueType>(ki[0][0]);
    result[4] = static_cast<OutputValueType>(ki[1][0]);
    result[5] = static_cast<OutputValueType>(ki[2][0]);


    qi[0][0]  = ComplexType(0., 0.);
    qi[1][0]  = ComplexType(0., 1. / std::sqrt(2.));
    qi[2][0]  = ComplexType(1. / std::sqrt(2.), 0.);
    norm      = (qi.conjugate_transpose() * cov * qi)[0][0];
    ki        = cov * qi / std::sqrt(norm);
    result[6] = static_cast<OutputValueType>(ki[0][0]);
    result[7] = static_cast<OutputValueType>(ki[1][0]);
    result[8] = static_cast<OutputValueType>(ki[2][0]);
  }

  constexpr size_t OutputSize(...) const
  {
    // Size of the result
    return 9;
  }

private:
  static constexpr double m_Epsilon = 1e-6;
};
} // namespace Functor

/**
 * \typedef ReciprocalBarnesDecompImageFilter
 * \brief Applies otb::Functor::ReciprocalBarnesDecompFunctor
 * \sa otb::Functor::ReciprocalBarnesDecompFunctor
 *
 * Set inputs with:
 * \code
 * SetInput<0>(inputPtr);
 * \endcode
 *
 * \ingroup OTBPolarimetry
 */
template <typename TInputImage, typename TOutputImage>
using ReciprocalBarnesDecompImageFilter =
    FunctorImageFilter<Functor::ReciprocalBarnesDecompFunctor<typename TInputImage::PixelType, typename TOutputImage::PixelType>>;
} // end namespace otb

#endif
