/*
 * Copyright (C) 2005-2020 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 otbReduceSpectralResponse_hxx
#define otbReduceSpectralResponse_hxx

#include <algorithm>
#include "itkNumericTraits.h"
#include "otbReduceSpectralResponse.h"

namespace otb
{

template <class TSpectralResponse, class TRSR>
ReduceSpectralResponse<TSpectralResponse, TRSR>::ReduceSpectralResponse() : m_ReflectanceMode(false)
{
  m_ReduceResponse = InputSpectralResponseType::New();
}

template <class TSpectralResponse, class TRSR>
bool ReduceSpectralResponse<TSpectralResponse, TRSR>::Clear()
{
  return (m_InputSatRSR->Clear() & m_InputSpectralResponse->Clear());
}

template <typename T>
inline T trapezoid_area(T x1, T x2, T y1, T y2)
{
  /* We compute the area of the trapezoid
      by computing the lower square and the
      upper triangle.
                   /- |y2
                 /-   |
               /-     |
             /-       |
      y1   +----------+
           |          |
           |          |
           |          |
           +----------+
          x1          x2

    (x2-x1)*min(y1,y2) + (x2-x1)*abs(y2-y1)/2
  */
  return (x2 - x1) * std::min(y1, y2) + (x2 - x1) * fabs(y2 - y1) * 0.5;
}

template <class TSpectralResponse, class TRSR>
inline typename ReduceSpectralResponse<TSpectralResponse, TRSR>::ValuePrecisionType ReduceSpectralResponse<TSpectralResponse, TRSR>::
operator()(const unsigned int numBand)
{
  if (numBand >= m_InputSatRSR->GetNbBands())
  {
    itkExceptionMacro(<< "There is no band num " << numBand << " in the RSR vector!(Size of the current RSR vector is " << m_InputSatRSR->GetNbBands() << ")");
  }
  else
  {
    ValuePrecisionType                           res             = itk::NumericTraits<ValuePrecisionType>::ZeroValue();
    typename InputRSRType::SpectralResponseType* solarIrradiance = this->m_InputSatRSR->GetSolarIrradiance();

    if (m_ReflectanceMode)
    {
      if (solarIrradiance == nullptr)
      {
        itkExceptionMacro(<< "Error occurs getting solar irradiance. Solar irradiance is mandatory using the reflectance mode.");
      }
    }
    typename VectorPairType::const_iterator it;
    VectorPairType                          pairs = (m_InputSatRSR->GetRSR())[numBand]->GetResponse();
    it                                            = pairs.begin();
    ValuePrecisionType totalArea(0);
    // start with the second value for the numerical integration
    ++it;
    while (it != pairs.end())
    {
      ValuePrecisionType rsr1 = (*(it - 1)).second;
      ValuePrecisionType rsr2 = (*it).second;
      if (rsr1 > 0 || rsr2 > 0)
      {
        PrecisionType lambda1 = (*(it - 1)).first;
        PrecisionType lambda2 = (*it).first;
        //      PrecisionType deltaLambda = lambda2-lambda1;
        ValuePrecisionType spectrum1 = (*m_InputSpectralResponse)(lambda1);
        ValuePrecisionType spectrum2 = (*m_InputSpectralResponse)(lambda2);
        /*
        In order to simplify the computation for the reflectance mode,
        we introduce the solar irradiance in the general formula with
        a value of 1.0 for the radiance case.

        In this way the formula is the same if we weight the RSR by
        the solar irradiance before the integration.
      */
        ValuePrecisionType solarIrradiance1(1.0);
        ValuePrecisionType solarIrradiance2(1.0);
        if (m_ReflectanceMode)
        {
          solarIrradiance1 = (*solarIrradiance)(lambda1);
          solarIrradiance2 = (*solarIrradiance)(lambda2);
        }
        rsr1 *= solarIrradiance1;
        rsr2 *= solarIrradiance2;
        res += trapezoid_area(lambda1, lambda2, rsr1 * spectrum1, rsr2 * spectrum2);
        totalArea += trapezoid_area(lambda1, lambda2, rsr1, rsr2);
      }
      ++it;
    }
    return res / totalArea;
  }
}

template <class TSpectralResponse, class TRSR>
void ReduceSpectralResponse<TSpectralResponse, TRSR>::CalculateResponse()
{
  m_ReduceResponse->Clear();
  // Compute the reduce response for each band of the sensor
  for (unsigned int i = 0; i < m_InputSatRSR->GetNbBands(); ++i)
  {
    m_InputSpectralResponse->SetPosGuessMin((this->m_InputSatRSR->GetRSR())[i]->GetInterval().first);
    m_InputSpectralResponse->SetUsePosGuess(true);
    PairType pair;
    // pair.first = center wavelength of the band
    pair.first  = ((this->m_InputSatRSR->GetRSR())[i]->GetInterval().first + (this->m_InputSatRSR->GetRSR())[i]->GetInterval().second);
    pair.first  = pair.first / 2.0;
    pair.second = (*this)(i);
    m_ReduceResponse->GetResponse().push_back(pair);
    m_InputSpectralResponse->SetUsePosGuess(false);
  }
}


template <class TSpectralResponse, class TRSR>
void ReduceSpectralResponse<TSpectralResponse, TRSR>::LoadInputsFromFiles(const std::string& spectralResponseFile, const std::string& RSRFile,
                                                                          const unsigned int nbRSRBands, ValuePrecisionType coefNormSpectre,
                                                                          ValuePrecisionType coefNormRSR)
{
  // Instantiation
  m_InputSpectralResponse = InputSpectralResponseType::New();
  /** Load the spectral response file*/
  m_InputSpectralResponse->Load(spectralResponseFile, coefNormSpectre);

  m_InputSatRSR = InputRSRType::New();
  /** Set the satellite number of bands */
  m_InputSatRSR->SetNbBands(nbRSRBands);
  /** Load the satellite response file*/
  m_InputSatRSR->Load(RSRFile, coefNormRSR);
}


template <class TSpectralResponse, class TRSR>
void ReduceSpectralResponse<TSpectralResponse, TRSR>::PrintSelf(std::ostream& os, itk::Indent indent) const
{
  Superclass::PrintSelf(os, indent);
  os << std::endl;
  os << "spectre " << m_InputSpectralResponse << std::endl;
  os << "Sat RSR " << m_InputSatRSR << std::endl;
  os << std::endl;

  if (m_ReflectanceMode)
  {
    os << "Solar irradiance " << std::endl;
    this->m_InputSatRSR->GetSolarIrradiance()->PrintSelf(os, indent);
    os << std::endl;
    os << indent << "[Center Wavelength (micrometers), Reflectance (percent)]" << std::endl;
  }
  else
  {
    os << indent << "[Center Wavelength (micrometers), Radiance (percent)]" << std::endl;
  }

  for (typename VectorPairType::const_iterator it = m_ReduceResponse->GetResponse().begin(); it != m_ReduceResponse->GetResponse().end(); ++it)
  {
    os << indent << "Band Nb : " << it - m_ReduceResponse->GetResponse().begin() << ": [" << (*it).first << "," << (*it).second << "]" << std::endl;
  }
}


} // end namespace otb

#endif
