/*=========================================================================
 *
 *  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 "itkLBFGSBOptimizer.h"
#include "itkTextOutput.h"
#include "itkMath.h"
#include "itkTestingMacros.h"
#include <iostream>

/**
 *  LBFGSBCostFunction
 *
 *  The objective function is the quadratic form:
 *
 *  f(x) = 1/2 x^T A x - b^T x  subject to  -1 <= x <= 10
 *
 *  Where A is represented as an itkMatrix and
 *  b is represented as an itkVector
 *
 *  The system in this example is:
 *
 *          | 3  2 |       | 2|
 *      A=  | 2  6 |   b = |-8|
 *
 *   the solution is the vector | 4/3 -1 |
 *
 * \class LBFGSBCostFunction
 */
class LBFGSBCostFunction : public itk::SingleValuedCostFunction
{
public:
  using Self = LBFGSBCostFunction;
  using Superclass = itk::SingleValuedCostFunction;
  using Pointer = itk::SmartPointer<Self>;
  using ConstPointer = itk::SmartPointer<const Self>;
  itkNewMacro(Self);
  itkOverrideGetNameOfClassMacro(LBFGSBCostFunction);

  enum
  {
    SpaceDimension = 2
  };

  using ParametersType = Superclass::ParametersType;
  using DerivativeType = Superclass::DerivativeType;

  using VectorType = vnl_vector<double>;
  using MatrixType = vnl_matrix<double>;

  using MeasureType = double;

  LBFGSBCostFunction() = default;

  double
  GetValue(const ParametersType & position) const override
  {

    double x = position[0];
    double y = position[1];

    std::cout << "GetValue ( ";
    std::cout << x << " , " << y;
    std::cout << ") = ";

    double val = 0.5 * (3 * x * x + 4 * x * y + 6 * y * y) - 2 * x + 8 * y;

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

    return val;
  }

  void
  GetDerivative(const ParametersType & position, DerivativeType & derivative) const override
  {

    double x = position[0];
    double y = position[1];

    std::cout << "GetDerivative ( ";
    std::cout << x << " , " << y;
    std::cout << ") = ";

    derivative = DerivativeType(SpaceDimension);
    derivative[0] = 3 * x + 2 * y - 2;
    derivative[1] = 2 * x + 6 * y + 8;
    std::cout << '(';
    std::cout << derivative[0] << " , ";
    std::cout << derivative[1] << ')' << std::endl;
  }


  unsigned int
  GetNumberOfParameters() const override
  {
    return SpaceDimension;
  }
};

/** To ensure the events get fired. */
class EventChecker : public itk::Command
{
public:
  using Self = EventChecker;
  using Superclass = itk::Command;
  using Pointer = itk::SmartPointer<Self>;

  itkNewMacro(Self);

  bool
  GetHadStartEvent() const
  {
    return m_HadStartEvent;
  }
  bool
  GetHadIterationEvent() const
  {
    return m_HadIterationEvent;
  }
  bool
  GetHadEndEvent() const
  {
    return m_HadEndEvent;
  }

  void
  Execute(itk::Object * caller, const itk::EventObject & event) override
  {
    Execute((const itk::Object *)caller, event);
  }

  void
  Execute(const itk::Object *, const itk::EventObject & event) override
  {
    if (itk::StartEvent().CheckEvent(&event))
    {
      std::cout << "Received StartEvent." << std::endl;
      m_HadStartEvent = true;
    }
    if (itk::IterationEvent().CheckEvent(&event))
    {
      std::cout << "Received IterationEvent." << std::endl;
      m_HadIterationEvent = true;
    }
    if (itk::EndEvent().CheckEvent(&event))
    {
      std::cout << "Received EndEvent." << std::endl;
      m_HadEndEvent = true;
    }
  }

protected:
  EventChecker() = default;

private:
  bool m_HadStartEvent{ false };
  bool m_HadIterationEvent{ false };
  bool m_HadEndEvent{ false };
};


int
itkLBFGSBOptimizerTest(int, char *[])
{

  itk::OutputWindow::SetInstance(itk::TextOutput::New().GetPointer());

  using OptimizerType = itk::LBFGSBOptimizer;

  // Declaration of an itkOptimizer
  auto itkOptimizer = OptimizerType::New();

  ITK_EXERCISE_BASIC_OBJECT_METHODS(itkOptimizer, LBFGSBOptimizer, SingleValuedNonLinearVnlOptimizer);


  // Declaration of the CostFunction adaptor
  auto costFunction = LBFGSBCostFunction::New();


  itkOptimizer->SetCostFunction(costFunction);

  bool trace = false;
  ITK_TEST_SET_GET_BOOLEAN(itkOptimizer, Trace, trace);

  const double  F_Convergence_Factor = 1e+7;  // Function value tolerance
  const double  Projected_G_Tolerance = 1e-5; // Proj gradient tolerance
  constexpr int Max_Iterations = 100;         // Maximum number of iterations

  itkOptimizer->SetCostFunctionConvergenceFactor(F_Convergence_Factor);
  ITK_TEST_SET_GET_VALUE(F_Convergence_Factor, itkOptimizer->GetCostFunctionConvergenceFactor());

  itkOptimizer->SetProjectedGradientTolerance(Projected_G_Tolerance);
  ITK_TEST_SET_GET_VALUE(Projected_G_Tolerance, itkOptimizer->GetProjectedGradientTolerance());

  itkOptimizer->SetMaximumNumberOfIterations(Max_Iterations);
  ITK_TEST_SET_GET_VALUE(Max_Iterations, itkOptimizer->GetMaximumNumberOfIterations());

  itkOptimizer->SetMaximumNumberOfEvaluations(Max_Iterations);
  ITK_TEST_SET_GET_VALUE(Max_Iterations, itkOptimizer->GetMaximumNumberOfEvaluations());

  unsigned int maximumNumberOfCorrections = 5;
  itkOptimizer->SetMaximumNumberOfCorrections(maximumNumberOfCorrections);
  ITK_TEST_SET_GET_VALUE(maximumNumberOfCorrections, itkOptimizer->GetMaximumNumberOfCorrections());

  ITK_TEST_EXPECT_TRUE(!itkOptimizer->CanUseScales());

  constexpr unsigned int        SpaceDimension = 2;
  OptimizerType::ParametersType initialValue(SpaceDimension);

  // Starting point
  initialValue[0] = 10;
  initialValue[1] = 10;

  OptimizerType::ParametersType currentValue(2);

  currentValue = initialValue;

  itkOptimizer->SetInitialPosition(currentValue);

  // Set up boundary conditions
  OptimizerType::BoundValueType     lower(SpaceDimension);
  OptimizerType::BoundValueType     upper(SpaceDimension);
  OptimizerType::BoundSelectionType select(SpaceDimension);

  lower.Fill(-1);
  upper.Fill(10);
  select.Fill(2);

  itkOptimizer->SetLowerBound(lower);
  ITK_TEST_SET_GET_VALUE(lower, itkOptimizer->GetLowerBound());

  itkOptimizer->SetUpperBound(upper);
  ITK_TEST_SET_GET_VALUE(upper, itkOptimizer->GetUpperBound());

  itkOptimizer->SetBoundSelection(select);
  ITK_TEST_SET_GET_VALUE(select, itkOptimizer->GetBoundSelection());

  auto eventChecker = EventChecker::New();
  itkOptimizer->AddObserver(itk::StartEvent(), eventChecker);
  itkOptimizer->AddObserver(itk::IterationEvent(), eventChecker);
  itkOptimizer->AddObserver(itk::EndEvent(), eventChecker);

  try
  {

    itkOptimizer->StartOptimization();
  }
  catch (const itk::ExceptionObject & e)
  {
    std::cout << "Exception thrown ! " << std::endl;
    std::cout << "An error occurred during Optimization" << std::endl;
    std::cout << "Location    = " << e.GetLocation() << std::endl;
    std::cout << "Description = " << e.GetDescription() << std::endl;
    return EXIT_FAILURE;
  }

  const OptimizerType::ParametersType & finalPosition = itkOptimizer->GetCurrentPosition();

  std::cout << "Solution        = (" << finalPosition[0] << ',' << finalPosition[1] << ')' << std::endl;
  std::cout << "Final Function Value = " << itkOptimizer->GetValue() << std::endl;

  std::cout << "Infinity Norm of Projected Gradient = " << itkOptimizer->GetInfinityNormOfProjectedGradient()
            << std::endl;
  std::cout << "End condition   = " << itkOptimizer->GetStopConditionDescription() << std::endl;

  if (!eventChecker->GetHadStartEvent())
  {
    std::cout << "Did not have StartEvent!" << std::endl;
    return EXIT_FAILURE;
  }
  if (!eventChecker->GetHadIterationEvent())
  {
    std::cout << "Did not have IterationEvent!" << std::endl;
    return EXIT_FAILURE;
  }
  if (!eventChecker->GetHadEndEvent())
  {
    std::cout << "Did not have EndEvent!" << std::endl;
    return EXIT_FAILURE;
  }

  //
  // check results to see if it is within range
  //
  bool        pass = true;
  std::string errorIn;

  double trueParameters[2] = { 4.0 / 3.0, -1.0 };
  for (unsigned int j = 0; j < 2; ++j)
  {
    if (itk::Math::abs(finalPosition[j] - trueParameters[j]) > 0.01)
    {
      pass = false;
      errorIn = "solution";
    }
  }

  if (itk::Math::abs(itkOptimizer->GetValue() - -7.66667) > 0.01)
  {
    pass = false;
    errorIn = "final function value";
  }


  if (itk::Math::abs(itkOptimizer->GetInfinityNormOfProjectedGradient() - 1.77636e-15) > 0.01)
  {
    pass = false;
    errorIn = "infinity norm of projected gradient";
  }

  if (!pass)
  {
    std::cout << "\nError in " << errorIn << ".\n";
    std::cout << "Test failed." << std::endl;
    return EXIT_FAILURE;
  }

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