/*=========================================================================
 *
 *  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 itkOptimizerParameterScalesEstimator_h
#define itkOptimizerParameterScalesEstimator_h

#include "itkObject.h"
#include "itkObjectFactory.h"
#include "itkOptimizerParameters.h"

namespace itk
{

/**
 * \class OptimizerParameterScalesEstimatorTemplate
 *  \brief OptimizerParameterScalesEstimatorTemplate is the base class offering a
 * empty method of estimating the parameter scales for optimizers.
 *
 * Its subclass RegistrationParameterScalesEstimator estimates scales for
 * registration optimizers.
 *
 * \ingroup ITKOptimizersv4
 */
template <typename TInternalComputationValueType = double>
class OptimizerParameterScalesEstimatorTemplate : public Object
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(OptimizerParameterScalesEstimatorTemplate);

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

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

  /** Type of scales */
  using ScalesType = OptimizerParameters<TInternalComputationValueType>;
  /** Type of parameters of the optimizer */
  using ParametersType = OptimizerParameters<TInternalComputationValueType>;

  /** Type of float */
  using FloatType = TInternalComputationValueType;

  /** Estimate parameter scales. */
  virtual void
  EstimateScales(ScalesType & scales) = 0;

  /** Estimate the scale of a step. */
  virtual FloatType
  EstimateStepScale(const ParametersType & step) = 0;

  /** Estimate the scales of local steps. */
  virtual void
  EstimateLocalStepScales(const ParametersType & step, ScalesType & localStepScales) = 0;

  /** Estimate the maximum size for steps. */
  virtual FloatType
  EstimateMaximumStepSize() = 0;

protected:
  OptimizerParameterScalesEstimatorTemplate() = default;
  ~OptimizerParameterScalesEstimatorTemplate() override = default;

  void
  PrintSelf(std::ostream & os, Indent indent) const override
  {
    Superclass::PrintSelf(os, indent);
  }
}; // class OptimizerParameterScalesEstimatorTemplate

/** This helps to meet backward compatibility */
using OptimizerParameterScalesEstimator = OptimizerParameterScalesEstimatorTemplate<double>;

} // namespace itk

#endif