/*=========================================================================
 *
 *  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.
 *
 *=========================================================================*/
#include "itkRegistrationParameterScalesFromIndexShift.h"
#include "itkImageToImageMetricv4.h"

#include "itkAffineTransform.h"
#include "itkDisplacementFieldTransform.h"
#include "itkMath.h"

/**
 *  \class RegistrationParameterScalesFromIndexShiftTestMetric for test.
 *  Create a simple metric to use for testing here.
 */
template <typename TFixedImage, typename TMovingImage, typename TVirtualImage = TFixedImage>
class RegistrationParameterScalesFromIndexShiftTestMetric
  : public itk::ImageToImageMetricv4<TFixedImage, TMovingImage, TVirtualImage>
{
public:
  /** Standard class type aliases. */
  using Self = RegistrationParameterScalesFromIndexShiftTestMetric;
  using Superclass = itk::ImageToImageMetricv4<TFixedImage, TMovingImage, TVirtualImage>;
  using Pointer = itk::SmartPointer<Self>;
  using ConstPointer = itk::SmartPointer<const Self>;

  using typename Superclass::MeasureType;
  using typename Superclass::DerivativeType;
  using typename Superclass::ParametersType;
  using typename Superclass::ParametersValueType;

  itkOverrideGetNameOfClassMacro(RegistrationParameterScalesFromIndexShiftTestMetric);

  itkNewMacro(Self);

  // Pure virtual functions that all Metrics must provide
  unsigned int
  GetNumberOfParameters() const override
  {
    return 5;
  }

  MeasureType
  GetValue() const override
  {
    return 1.0;
  }

  void
  GetValueAndDerivative(MeasureType & value, DerivativeType & derivative) const override
  {
    value = 1.0;
    derivative.Fill(0.0);
  }

  unsigned int
  GetNumberOfLocalParameters() const override
  {
    return 0;
  }

  void
  UpdateTransformParameters(const DerivativeType &, ParametersValueType) override
  {}

  const ParametersType &
  GetParameters() const override
  {
    return m_Parameters;
  }

  void
  Initialize() override
  {}

  ParametersType m_Parameters;

  // Image related types
  using FixedImageType = TFixedImage;
  using MovingImageType = TMovingImage;
  using VirtualImageType = TVirtualImage;

  using FixedImageConstPointer = typename FixedImageType::ConstPointer;
  using MovingImageConstPointer = typename MovingImageType::ConstPointer;
  using VirtualImagePointer = typename VirtualImageType::Pointer;
  using VirtualRegionType = typename VirtualImageType::RegionType;

  /* Image dimension accessors */
  static constexpr itk::SizeValueType FixedImageDimension = FixedImageType::ImageDimension;
  static constexpr itk::SizeValueType MovingImageDimension = MovingImageType::ImageDimension;
  static constexpr itk::SizeValueType VirtualImageDimension = VirtualImageType::ImageDimension;

private:
  RegistrationParameterScalesFromIndexShiftTestMetric() = default;
  ~RegistrationParameterScalesFromIndexShiftTestMetric() override = default;
};

/**
 */
int
itkRegistrationParameterScalesFromIndexShiftTest(int, char *[])
{

  // Image begins
  constexpr itk::SizeValueType ImageDimension = 2;
  using PixelType = double;
  using FloatType = double;

  // Image Types
  using FixedImageType = itk::Image<PixelType, ImageDimension>;
  using MovingImageType = itk::Image<PixelType, ImageDimension>;
  using VirtualImageType = itk::Image<PixelType, ImageDimension>;

  auto                      fixedImage = FixedImageType::New();
  auto                      movingImage = MovingImageType::New();
  VirtualImageType::Pointer virtualImage = fixedImage;

  MovingImageType::SizeType size;
  size.Fill(100);

  movingImage->SetRegions(size);
  fixedImage->SetRegions(size);
  // Image done

  // Transform begins
  using MovingTransformType = itk::AffineTransform<double, ImageDimension>;
  auto movingTransform = MovingTransformType::New();
  movingTransform->SetIdentity();

  using FixedTransformType = itk::TranslationTransform<double, ImageDimension>;
  auto fixedTransform = FixedTransformType::New();
  fixedTransform->SetIdentity();
  // Transform done

  // Metric
  using MetricType = RegistrationParameterScalesFromIndexShiftTestMetric<FixedImageType, MovingImageType>;
  auto metric = MetricType::New();

  metric->SetVirtualDomainFromImage(virtualImage);
  metric->SetFixedImage(fixedImage);
  metric->SetMovingImage(movingImage);

  metric->SetFixedTransform(fixedTransform);
  metric->SetMovingTransform(movingTransform);

  // Testing RegistrationParameterScalesFromIndexShift
  using RegistrationParameterScalesFromShiftType = itk::RegistrationParameterScalesFromIndexShift<MetricType>;
  RegistrationParameterScalesFromShiftType::Pointer shiftScaleEstimator =
    RegistrationParameterScalesFromShiftType::New();

  shiftScaleEstimator->SetMetric(metric);

  // Testing moving scales
  RegistrationParameterScalesFromShiftType::ScalesType movingScales(movingTransform->GetNumberOfParameters());
  shiftScaleEstimator->EstimateScales(movingScales);
  std::cout << "Shift scales for the affine transform = " << movingScales << std::endl;

  // determine truth
  RegistrationParameterScalesFromShiftType::ScalesType theoreticalMovingScales(
    movingTransform->GetNumberOfParameters());
  VirtualImageType::PointType upperPoint;
  virtualImage->TransformIndexToPhysicalPoint(virtualImage->GetLargestPossibleRegion().GetUpperIndex(), upperPoint);

  itk::SizeValueType param = 0;
  for (itk::SizeValueType row = 0; row < ImageDimension; ++row)
  {
    for (itk::SizeValueType col = 0; col < ImageDimension; ++col)
    {
      theoreticalMovingScales[param++] = upperPoint[col] * upperPoint[col];
    }
  }
  for (itk::SizeValueType row = 0; row < ImageDimension; ++row)
  {
    theoreticalMovingScales[param++] = 1;
  }

  // compare test to truth
  bool affinePass = true;
  for (itk::SizeValueType p = 0; p < theoreticalMovingScales.GetSize(); ++p)
  {
    if (itk::Math::abs((movingScales[p] - theoreticalMovingScales[p]) / theoreticalMovingScales[p]) > 0.01)
    {
      affinePass = false;
      break;
    }
  }
  if (!affinePass)
  {
    std::cout << "Failed: the shift scales for the affine transform are not correct." << std::endl;
  }
  else
  {
    std::cout << "Passed: the shift scales for the affine transform are correct." << std::endl;
  }

  // test for non-uniform scales, expected with an affine transform
  bool nonUniformForAffine = false;
  for (itk::SizeValueType p = 1; p < movingScales.GetSize(); ++p)
  {
    if (itk::Math::NotExactlyEquals(movingScales[p], movingScales[0]))
    {
      nonUniformForAffine = true;
      break;
    }
  }
  if (!nonUniformForAffine)
  {
    std::cout << "Error: the shift scales for an affine transform are equal for all parameters." << std::endl;
  }

  //
  // Testing the step scale
  //
  MovingTransformType::ParametersType movingStep(movingTransform->GetNumberOfParameters());
  movingStep = movingTransform->GetParameters(); // the step is an identity transform
  FloatType stepScale = shiftScaleEstimator->EstimateStepScale(movingStep);
  std::cout << "The step scale of shift for the affine transform = " << stepScale << std::endl;
  FloatType learningRate = 1.0 / stepScale;
  std::cout << "The learning rate of shift for the affine transform = " << learningRate << std::endl;

  // compute truth
  FloatType theoreticalStepScale = 0.0;
  for (itk::SizeValueType row = 0; row < ImageDimension; ++row)
  {
    theoreticalStepScale += upperPoint[row] * upperPoint[row];
  }
  theoreticalStepScale = std::sqrt(theoreticalStepScale);

  // compare truth and test
  bool stepScalePass = false;
  if (itk::Math::abs((stepScale - theoreticalStepScale) / theoreticalStepScale) < 0.01)
  {
    stepScalePass = true;
  }
  if (!stepScalePass)
  {
    std::cout << "Failed: the step scale for the affine transform is not correct." << std::endl;
  }
  else
  {
    std::cout << "Passed: the step scale for the affine transform is correct." << std::endl;
  }

  //
  // Testing local scales for a transform with local support, ex. DisplacementFieldTransform
  //
  using DisplacementTransformType = itk::DisplacementFieldTransform<double, ImageDimension>;
  using FieldType = DisplacementTransformType::DisplacementFieldType;
  using VectorType = itk::Vector<double, ImageDimension>;

  VectorType zero;
  zero.Fill(0.0);

  auto field = FieldType::New();
  field->SetRegions(virtualImage->GetLargestPossibleRegion());
  field->SetSpacing(virtualImage->GetSpacing());
  field->SetOrigin(virtualImage->GetOrigin());
  field->SetDirection(virtualImage->GetDirection());
  field->Allocate();
  field->FillBuffer(zero);

  auto displacementTransform = DisplacementTransformType::New();
  displacementTransform->SetDisplacementField(field);

  metric->SetMovingTransform(displacementTransform);
  shiftScaleEstimator->SetTransformForward(true);
  RegistrationParameterScalesFromShiftType::ScalesType localScales;
  shiftScaleEstimator->EstimateScales(localScales);
  std::cout << "Shift scales for the displacement field transform = " << localScales << std::endl;

  // Check the correctness
  RegistrationParameterScalesFromShiftType::ScalesType theoreticalLocalScales(
    displacementTransform->GetNumberOfLocalParameters());
  theoreticalLocalScales.Fill(1.0);

  bool displacementPass = true;
  for (itk::SizeValueType p = 0; p < theoreticalLocalScales.GetSize(); ++p)
  {
    if (itk::Math::abs((localScales[p] - theoreticalLocalScales[p]) / theoreticalLocalScales[p]) > 0.01)
    {
      displacementPass = false;
      break;
    }
  }
  if (!displacementPass)
  {
    std::cout << "Failed: the shift scales for the displacement field transform are not correct." << std::endl;
  }
  else
  {
    std::cout << "Passed: the shift scales for the displacement field transform are correct." << std::endl;
  }

  //
  // Testing the step scale for the displacement field transform
  //
  DisplacementTransformType::ParametersType displacementStep(displacementTransform->GetNumberOfParameters());
  displacementStep.Fill(1.0);
  FloatType localStepScale = shiftScaleEstimator->EstimateStepScale(displacementStep);
  std::cout << "The step scale of shift for the displacement field transform = " << localStepScale << std::endl;
  FloatType localLearningRate = 1.0 / localStepScale;
  std::cout << "The learning rate of shift for the displacement field transform = " << localLearningRate << std::endl;

  bool      localStepScalePass = false;
  FloatType theoreticalLocalStepScale = std::sqrt(2.0);
  if (itk::Math::abs((localStepScale - theoreticalLocalStepScale) / theoreticalLocalStepScale) < 0.01)
  {
    localStepScalePass = true;
  }
  if (!localStepScalePass)
  {
    std::cout << "Failed: the step scale for the displacement field transform is not correct." << std::endl;
  }
  else
  {
    std::cout << "Passed: the step scale for the displacement field transform is correct." << std::endl;
  }

  //
  // Scales for the fixed translation transform
  //
  shiftScaleEstimator->SetTransformForward(false);
  shiftScaleEstimator->Print(std::cout);
  std::cout << std::endl;

  RegistrationParameterScalesFromShiftType::ScalesType fixedScales(fixedTransform->GetNumberOfParameters());
  shiftScaleEstimator->EstimateScales(fixedScales);
  std::cout << "Shift scales for the translation transform = " << fixedScales << std::endl;

  // Check the correctness
  RegistrationParameterScalesFromShiftType::ScalesType theoreticalFixedScales(fixedTransform->GetNumberOfParameters());
  theoreticalFixedScales.Fill(1.0);

  bool translationPass = true;
  for (itk::SizeValueType p = 0; p < theoreticalFixedScales.GetSize(); ++p)
  {
    if (itk::Math::abs((fixedScales[p] - theoreticalFixedScales[p]) / theoreticalFixedScales[p]) > 0.01)
    {
      translationPass = false;
      break;
    }
  }
  if (!translationPass)
  {
    std::cout << "Failed: the shift scales for the translation transform are not correct." << std::endl;
  }
  else
  {
    std::cout << "Passed: the shift scales for the translation transform are correct." << std::endl;
  }

  bool uniformForTranslation = true;
  for (itk::SizeValueType p = 1; p < fixedScales.GetSize(); ++p)
  {
    if (itk::Math::NotExactlyEquals(fixedScales[p], fixedScales[0]))
    {
      uniformForTranslation = false;
      break;
    }
  }
  if (!uniformForTranslation)
  {
    std::cout << "Error: the shift scales for a translation transform are not equal for all parameters." << std::endl;
  }

  // Check the correctness of all cases above
  std::cout << std::endl;
  if (translationPass && uniformForTranslation && affinePass && nonUniformForAffine && localStepScalePass &&
      displacementPass && stepScalePass)
  {
    std::cout << "Test passed" << std::endl;
    return EXIT_SUCCESS;
  }
  else
  {
    std::cout << "Test failed" << std::endl;
    return EXIT_FAILURE;
  }
}