/*=========================================================================
 *
 *  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 itkSubsamplerBase_h
#define itkSubsamplerBase_h

#include "itkObject.h"
#include "itkSample.h"
#include "itkSubsample.h"

namespace itk
{
namespace Statistics
{
/**
 * \class SubsamplerBase
 * \brief This is the base subsampler class which defines the subsampler API.
 *
 * This class will search a Sample provided by SetSample and return a
 * Subsample that are related in some way to the queried value.
 * Some examples of subsampling strategies include uniform random selection,
 * selection based on KdTree, and selection based on spatial proximity.
 *
 * This is an Abstract class that can not be instantiated.
 * There are multiple subsamplers that derive from this class and
 * provide specific implementations of subsampling strategies.
 *
 * \sa RegionConstrainedSubsampler, SpatialNeighborSubsampler
 * \sa GaussianRandomSpatialNeighborSubsampler
 * \sa UniformRandomSpatialNeighborSubsampler
 * \ingroup ITKStatistics
 */

template <typename TSample>
class ITK_TEMPLATE_EXPORT SubsamplerBase : public Object
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SubsamplerBase);

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

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

  /** implement type-specific clone method */
  itkCloneMacro(Self);

  /** type alias alias for the source data container */
  using SampleType = TSample;
  using SampleConstPointer = typename SampleType::ConstPointer;
  using MeasurementVectorType = typename TSample::MeasurementVectorType;
  using InstanceIdentifier = typename TSample::InstanceIdentifier;

  using SubsampleType = Subsample<TSample>;
  using SubsamplePointer = typename SubsampleType::Pointer;
  using SubsampleConstIterator = typename SubsampleType::ConstIterator;
  using InstanceIdentifierHolder = typename SubsampleType::InstanceIdentifierHolder;
  using SeedType = unsigned int;

  /** Plug in the actual sample data */
  itkSetConstObjectMacro(Sample, SampleType);
  itkGetConstObjectMacro(Sample, SampleType);

  /** Indicate whether the Search method can return the query point
   * as one element of the Subsample
   */
  itkSetMacro(CanSelectQuery, bool);
  itkGetConstReferenceMacro(CanSelectQuery, bool);
  itkBooleanMacro(CanSelectQuery);

  /** Provide an interface to set the seed.
   *  The seed value will be used by subclasses where appropriate.
   */
  itkSetMacro(Seed, SeedType);
  itkGetConstReferenceMacro(Seed, SeedType);


  /** Specify whether the subsampler should return all possible
   * matches. */
  virtual void
  RequestMaximumNumberOfResults()
  {
    if (!this->m_RequestMaximumNumberOfResults)
    {
      this->m_RequestMaximumNumberOfResults = true;
      this->Modified();
    }
  }

  /** Main Search method that MUST be implemented by each subclass
   * The Search method will find all points similar to query and return
   * them as a Subsample.  The definition of similar will be subclass-
   * specific.  And could mean spatial similarity or feature similarity
   * etc.  */
  virtual void
  Search(const InstanceIdentifier & query, SubsamplePointer & results) = 0;

protected:
  /**
   * Clone the current subsampler.
   * This does a complete copy of the subsampler state
   * to the new subsampler
   */
  typename LightObject::Pointer
  InternalClone() const override;

  SubsamplerBase();
  ~SubsamplerBase() override = default;

  void
  PrintSelf(std::ostream & os, Indent indent) const override;

  SampleConstPointer m_Sample{};
  bool               m_RequestMaximumNumberOfResults{};
  bool               m_CanSelectQuery{};
  SeedType           m_Seed{};
}; // end of class SubsamplerBase

} // end of namespace Statistics
} // end of namespace itk

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

#endif
