/*=========================================================================
 *
 *  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 "itkKalmanLinearEstimator.h"

#include <iostream>

/**
 *  This program test one instantiation of the itk::KalmanLinearEstimator class
 *
 *  The test is done by providing a Linear Equation in 6D for which the
 *  coefficients are known. A population of samples is generated and
 *  passed to the KalmanLinearEstimator.
 *
 */

int
itkKalmanLinearEstimatorTest(int, char *[])
{


  using KalmanFilterType = itk::KalmanLinearEstimator<double, 6>;

  using VectorType = KalmanFilterType::VectorType;
  using ValueType = KalmanFilterType::ValueType;

  KalmanFilterType filter;

  filter.ClearEstimation();
  filter.SetVariance(1.0);

  ValueType  measure;
  VectorType predictor;

  VectorType planeEquation;

  planeEquation(0) = 9.0;
  planeEquation(1) = 6.0;
  planeEquation(2) = 7.0;
  planeEquation(3) = 9.0;
  planeEquation(4) = 4.0;
  planeEquation(5) = 6.0;

  constexpr unsigned int N = 10;

  predictor(5) = 1.0;
  for (unsigned int ax = 0; ax < N; ++ax)
  {
    predictor(0) = ax;
    for (unsigned int bx = 0; bx < N; ++bx)
    {
      predictor(1) = bx;
      for (unsigned int cx = 0; cx < N; ++cx)
      {
        predictor(2) = cx;
        for (unsigned int dx = 0; dx < N; ++dx)
        {
          predictor(3) = dx;
          for (unsigned int ex = 0; ex < N; ++ex)
          {
            predictor(4) = ex;

            measure = dot_product(predictor, planeEquation);

            filter.UpdateWithNewMeasure(measure, predictor);
          }
        }
      }
    }
  }

  VectorType estimation = filter.GetEstimator();

  std::cout << std::endl << "The Right answer should be : " << std::endl;
  std::cout << planeEquation;

  std::cout << std::endl << "The Estimation is : " << std::endl;
  std::cout << estimation;

  VectorType error = estimation - planeEquation;
  ValueType  errorMagnitude = dot_product(error, error);

  std::cout << std::endl << "Errors : " << std::endl;
  std::cout << error;

  std::cout << std::endl << "Error Magnitude : " << std::endl;
  std::cout << errorMagnitude;

  std::cout << std::endl << "Variance : " << std::endl;
  std::cout << filter.GetVariance();

  std::cout << std::endl << std::endl;

  bool pass = true;

  const float tolerance = 1e-4;

  if (errorMagnitude > tolerance)
  {
    pass = false;
  }

  if (!pass)
  {
    std::cout << "Test failed." << std::endl;
    return EXIT_FAILURE;
  }

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