/*=========================================================================
 *
 *  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 "itkMeanSquaresImageToImageMetricv4.h"
#include "itkTranslationTransform.h"
#include "itkVectorImageToImageMetricTraitsv4.h"
#include "itkMath.h"

/* Simple test to verify that class builds and runs.
 * Results are not verified. See ImageToImageObjectMetricTest
 * for verification of basic metric functionality.
 *
 * TODO Numerical verification.
 */

int
itkMeanSquaresImageToImageMetricv4OnVectorTest(int, char ** const)
{

  constexpr unsigned int imageSize = 5;
  constexpr unsigned int imageDimensionality = 3;
  constexpr unsigned int vectorLength = 2;

  using VectorType = itk::Vector<double, vectorLength>;
  using ImageType = itk::Image<VectorType, imageDimensionality>;

  ImageType::SizeType size;
  size.Fill(imageSize);
  ImageType::IndexType index;
  index.Fill(0);
  ImageType::RegionType region;
  region.SetSize(size);
  region.SetIndex(index);
  ImageType::SpacingType spacing;
  spacing.Fill(1.0);
  ImageType::PointType origin;
  origin.Fill(0);
  ImageType::DirectionType direction;
  direction.SetIdentity();

  /* Create simple test images. */
  auto fixedImage = ImageType::New();
  fixedImage->SetRegions(region);
  fixedImage->SetSpacing(spacing);
  fixedImage->SetOrigin(origin);
  fixedImage->SetDirection(direction);
  fixedImage->Allocate();

  auto movingImage = ImageType::New();
  movingImage->SetRegions(region);
  movingImage->SetSpacing(spacing);
  movingImage->SetOrigin(origin);
  movingImage->SetDirection(direction);
  movingImage->Allocate();

  /* Fill images */
  itk::ImageRegionIterator<ImageType> itFixed(fixedImage, region);
  itFixed.GoToBegin();
  unsigned int count = 1;
  while (!itFixed.IsAtEnd())
  {
    VectorType pix;
    pix[0] = count * count;
    pix[1] = pix[0];
    itFixed.Set(pix);
    count++;
    ++itFixed;
  }

  itk::ImageRegionIteratorWithIndex<ImageType> itMoving(movingImage, region);

  itMoving.GoToBegin();
  count = 1;

  while (!itMoving.IsAtEnd())
  {
    VectorType pix;
    pix[0] = 1.0 / (count * count);
    pix[1] = pix[0];
    itMoving.Set(pix);
    count++;
    ++itMoving;
  }

  /* Transforms */
  using FixedTransformType = itk::TranslationTransform<double, imageDimensionality>;
  using MovingTransformType = itk::TranslationTransform<double, imageDimensionality>;

  auto fixedTransform = FixedTransformType::New();
  auto movingTransform = MovingTransformType::New();

  fixedTransform->SetIdentity();
  movingTransform->SetIdentity();

  /* The metric */
  using MetricTraitsType = itk::VectorImageToImageMetricTraitsv4<ImageType, ImageType, ImageType, vectorLength, double>;
  using MetricType = itk::MeanSquaresImageToImageMetricv4<ImageType, ImageType, ImageType, double, MetricTraitsType>;

  auto metric = MetricType::New();

  /* Assign images and transforms.
   * By not setting a virtual domain image or virtual domain settings,
   * the metric will use the fixed image for the virtual domain. */
  metric->SetFixedImage(fixedImage);
  metric->SetMovingImage(movingImage);
  metric->SetFixedTransform(fixedTransform);
  metric->SetMovingTransform(movingTransform);
  metric->SetMaximumNumberOfWorkUnits(1);

  metric->DebugOn();

  /* Initialize. */
  try
  {
    std::cout << "Calling Initialize..." << std::endl;
    metric->Initialize();
  }
  catch (const itk::ExceptionObject & exc)
  {
    std::cerr << "Caught unexpected exception during Initialize: " << exc << std::endl;
    return EXIT_FAILURE;
  }
  std::cout << "Initialized" << std::endl;

  /* Evaluate with GetValueAndDerivative */
  MetricType::MeasureType    valueReturn1, valueReturn2;
  MetricType::DerivativeType derivativeReturn;

  try
  {
    std::cout << "Calling GetValueAndDerivative..." << std::endl;
    metric->GetValueAndDerivative(valueReturn1, derivativeReturn);
  }
  catch (const itk::ExceptionObject & exc)
  {
    std::cout << "Caught unexpected exception during GetValueAndDerivative: " << exc;
    return EXIT_FAILURE;
  }

  /* Re-initialize. */
  try
  {
    std::cout << "Calling Initialize..." << std::endl;
    metric->Initialize();
  }
  catch (const itk::ExceptionObject & exc)
  {
    std::cerr << "Caught unexpected exception during re-initialize: " << exc << std::endl;
    return EXIT_FAILURE;
  }

  try
  {
    std::cout << "Calling GetValue..." << std::endl;
    valueReturn2 = metric->GetValue();
  }
  catch (const itk::ExceptionObject & exc)
  {
    std::cout << "Caught unexpected exception during GetValue: " << exc;
    return EXIT_FAILURE;
  }

  /* Test same value returned by different methods */
  std::cout << "Check Value return values..." << std::endl;
  if (itk::Math::NotExactlyEquals(valueReturn1, valueReturn2))
  {
    std::cerr << "Results for Value don't match: " << valueReturn1 << ", " << valueReturn2 << std::endl;
  }
  else
  {
    std::cout << "Metric value = " << valueReturn1 << std::endl;
    std::cout << "Gradient value = " << derivativeReturn << std::endl;
  }

  std::cout << "Test passed." << std::endl;
  return EXIT_SUCCESS;
}