/*=========================================================================
 *
 *  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 itkDistanceToCentroidMembershipFunction_h
#define itkDistanceToCentroidMembershipFunction_h

#include "itkMembershipFunctionBase.h"
#include "itkDistanceMetric.h"

namespace itk::Statistics
{
/** \class DistanceToCentroidMembershipFunction
 * \brief DistanceToCentroidMembershipFunction models class membership
 * using a distance metric.
 *
 * DistanceToCentroidMembershipFunction is a subclass of
 * MembershipFunctionBase that models class membership using the
 * distance to the centroid of the class. A choice of distance metric
 * can be specified using the SetDistanceMetric() method. Options
 * include EuclideanDistanceMetric, EuclideanSquaredDistanceMetric,
 * and ManhattanDistanceMetric. The centroid of the class is specified
 * using the SetCentroid() method. Any other parameters to control the
 * distance function evaluation have to be set directly on the
 * distance function itself.
 *
 * \ingroup ITKStatistics
 */
template <typename TVector>
class ITK_TEMPLATE_EXPORT DistanceToCentroidMembershipFunction : public MembershipFunctionBase<TVector>
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(DistanceToCentroidMembershipFunction);

  /** Standard class type aliases */
  using Self = DistanceToCentroidMembershipFunction;
  using Superclass = MembershipFunctionBase<TVector>;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** \see LightObject::GetNameOfClass() */
  /** @ITKStartGrouping */
  itkOverrideGetNameOfClassMacro(DistanceToCentroidMembershipFunction);
  itkNewMacro(Self);
  /** @ITKEndGrouping */
  /** SmartPointer class for superclass */
  using MembershipFunctionPointer = typename Superclass::Pointer;

  /** Typedef alias for the measurement vectors */
  using MeasurementVectorType = TVector;

  /** Typedef to represent the length of measurement vectors */
  using typename Superclass::MeasurementVectorSizeType;

  /**  Set the length of each measurement vector. */
  void SetMeasurementVectorSize(MeasurementVectorSizeType) override;

  /** Type of the DistanceMetric to use */
  using DistanceMetricType = DistanceMetric<MeasurementVectorType>;
  using DistanceMetricPointer = typename DistanceMetricType::Pointer;
  using CentroidType = typename DistanceMetricType::OriginType;

  /** Set the DistanceMetric to be used when calling the Evaluate() method */
  itkSetObjectMacro(DistanceMetric, DistanceMetricType);

  /** Get the DistanceMetric used by the MembershipFunction */
  itkGetModifiableObjectMacro(DistanceMetric, DistanceMetricType);

  /** Get the DistanceMetric used by the MembershipFunction. This is
   * a non-const version that allows you to configure the distance
   * function directly. */

  /** Set the centroid of the class (propagated to the DistanceMetric) */
  void
  SetCentroid(const CentroidType & centroid);

  /** Get the centroid of the class (requested from the DistanceMetric */
  const CentroidType &
  GetCentroid() const;

  /**
   * Method to get probability of an instance. The return value is the
   * value of the density function, not probability. */
  double
  Evaluate(const MeasurementVectorType & measurement) const override;

protected:
  DistanceToCentroidMembershipFunction();
  ~DistanceToCentroidMembershipFunction() override = default;
  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  /** Return a copy of the current membership function */
  [[nodiscard]] LightObject::Pointer
  InternalClone() const override;

private:
  DistanceMetricPointer m_DistanceMetric{};
};
} // namespace itk::Statistics

#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkDistanceToCentroidMembershipFunction.hxx"
#endif

#endif
