/*
 * 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 otbSVMCrossValidationCostFunction_hxx
#define otbSVMCrossValidationCostFunction_hxx

#include "otbSVMCrossValidationCostFunction.h"
#include "otbMacro.h"

namespace otb
{
template <class TModel>
SVMCrossValidationCostFunction<TModel>::SVMCrossValidationCostFunction() : m_Model(), m_DerivativeStep(0.001)
{
}
template <class TModel>
SVMCrossValidationCostFunction<TModel>::~SVMCrossValidationCostFunction()
{
}
template <class TModel>
typename SVMCrossValidationCostFunction<TModel>::MeasureType SVMCrossValidationCostFunction<TModel>::GetValue(const ParametersType& parameters) const
{
  // Check the input model
  if (!m_Model)
  {
    itkExceptionMacro(<< "Model is null, can not evaluate accuracy.");
  }

  // Check for a positive and non-null C
  if (parameters[0] <= 0)
  {
    return 0;
  }

  // Updates vm_parameters according to current parameters
  this->UpdateParameters(parameters);

  return m_Model->CrossValidation();
}

template <class TModel>
void SVMCrossValidationCostFunction<TModel>::GetDerivative(const ParametersType& parameters, DerivativeType& derivative) const
{
  // Set derivative size
  derivative.SetSize(parameters.Size());
  derivative.Fill(itk::NumericTraits<ParametersValueType>::Zero);

  for (unsigned int i = 0; i < parameters.Size(); ++i)
  {
    MeasureType    y1, y2;
    ParametersType x1, x2;

    x1 = parameters;
    x1[i] -= m_DerivativeStep;
    y1 = this->GetValue(x1);

    x2 = parameters;
    x2[i] += m_DerivativeStep;
    y2 = this->GetValue(x2);

    derivative[i] = (y2 - y1) / (2 * m_DerivativeStep);
    otbMsgDevMacro(<< "x1= " << x1 << " x2= " << x2 << ", y1= " << y1 << ", y2= " << y2);
  }
  otbMsgDevMacro("Position: " << parameters << ", Value: " << this->GetValue(parameters) << ", Derivatives: " << derivative);
}

template <class TModel>
unsigned int SVMCrossValidationCostFunction<TModel>::GetNumberOfParameters(void) const
{
  if (!m_Model)
  {
    itkExceptionMacro(<< "Model is null, can not evaluate number of parameters.");
  }
  return m_Model->GetNumberOfKernelParameters();
}

template <class TModel>
void SVMCrossValidationCostFunction<TModel>::UpdateParameters(const ParametersType& parameters) const
{
  unsigned int nbParams = m_Model->GetNumberOfKernelParameters();
  m_Model->SetC(parameters[0]);
  if (nbParams > 1)
    m_Model->SetKernelGamma(parameters[1]);
  if (nbParams > 2)
    m_Model->SetKernelCoef0(parameters[2]);
}

} // namespace otb

#endif
