/*=========================================================================
 *
 *  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.
 *
 *=========================================================================*/
#ifndef itkSingleValuedNonLinearVnlOptimizer_h
#define itkSingleValuedNonLinearVnlOptimizer_h

#include "itkSingleValuedNonLinearOptimizer.h"
#include "itkSingleValuedVnlCostFunctionAdaptor.h"
#include "itkCommand.h"
#include "ITKOptimizersExport.h"

namespace itk
{
/** \class SingleValuedNonLinearVnlOptimizer
 * \brief This class is a base for the Optimization methods that
 * optimize a single valued function.
 *
 * It is an Adaptor class for optimizers provided by the vnl library
 *
 * \ingroup Numerics Optimizers
 * \ingroup ITKOptimizers
 */
class ITKOptimizers_EXPORT SingleValuedNonLinearVnlOptimizer : public SingleValuedNonLinearOptimizer
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SingleValuedNonLinearVnlOptimizer);

  /** Standard class type aliases. */
  using Self = SingleValuedNonLinearVnlOptimizer;
  using Superclass = SingleValuedNonLinearOptimizer;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(SingleValuedNonLinearVnlOptimizer);

  /** Command observer that will interact with the ITKVNL cost-function
   * adaptor in order to generate iteration events. This will allow to overcome
   * the limitation of VNL optimizers not offering callbacks for every
   * iteration */
  using CommandType = ReceptorMemberCommand<Self>;

  /** Set the cost Function. This method has to be overloaded
   *  by derived classes because the CostFunctionAdaptor requires
   *  to know the number of parameters at construction time. This
   *  number of parameters is obtained at run-time from the itkCostFunction.
   *  As a consequence each derived optimizer should construct its own
   *  CostFunctionAdaptor when overloading this method  */
  void
  SetCostFunction(SingleValuedCostFunction * costFunction) override = 0;

  /** Methods to define whether the cost function will be maximized or
   * minimized. By default the VNL amoeba optimizer is only a minimizer.
   * Maximization is implemented here by notifying the CostFunctionAdaptor
   * which in its turn will multiply the function values and its derivative by
   * -1.0. */
  itkGetConstReferenceMacro(Maximize, bool);
  itkSetMacro(Maximize, bool);
  itkBooleanMacro(Maximize);
  bool
  GetMinimize() const
  {
    return !m_Maximize;
  }
  void
  SetMinimize(bool v)
  {
    this->SetMaximize(!v);
  }
  void
  MinimizeOn()
  {
    this->MaximizeOff();
  }
  void
  MinimizeOff()
  {
    this->MaximizeOn();
  }

  /** Return Cached Values. These method have the advantage of not triggering a
   * recomputation of the metric value, but it has the disadvantage of returning
   * a value that may not be the one corresponding to the current parameters. For
   * GUI update purposes, this method is a good option, for mathematical
   * validation you should rather call GetValue(). */
  itkGetConstReferenceMacro(CachedValue, MeasureType);
  itkGetConstReferenceMacro(CachedDerivative, DerivativeType);
  itkGetConstReferenceMacro(CachedCurrentPosition, ParametersType);

  /** Returns true if derived optimizer supports using scales.
   * For optimizers that do not support scaling, this
   * default function is overridden to return false.*/
  virtual bool
  CanUseScales() const
  {
    return true;
  }

protected:
  SingleValuedNonLinearVnlOptimizer();
  ~SingleValuedNonLinearVnlOptimizer() override;

  using CostFunctionAdaptorType = SingleValuedVnlCostFunctionAdaptor;

  void
  SetCostFunctionAdaptor(CostFunctionAdaptorType * adaptor);

  const CostFunctionAdaptorType *
  GetCostFunctionAdaptor() const;

  CostFunctionAdaptorType *
  GetCostFunctionAdaptor();

  /** The purpose of this method is to get around the lack of
   *  const-correctness in VNL cost-functions and optimizers */
  CostFunctionAdaptorType *
  GetNonConstCostFunctionAdaptor() const;

  /** Print out internal state */
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

private:
  /** Callback function for the Command Observer */
  void
  IterationReport(const EventObject & event);

  CostFunctionAdaptorType * m_CostFunctionAdaptor{};

  bool m_Maximize{};

  CommandType::Pointer m_Command{};

  mutable ParametersType m_CachedCurrentPosition{};
  mutable MeasureType    m_CachedValue{};
  mutable DerivativeType m_CachedDerivative{};
};
} // end namespace itk

#endif
