/*=========================================================================
 *
 *  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 itkMeanSampleFilter_h
#define itkMeanSampleFilter_h

#include "itkProcessObject.h"
#include "itkArray.h"
#include "itkSimpleDataObjectDecorator.h"

namespace itk
{
namespace Statistics
{
/**
 * \class MeanSampleFilter
 * \brief Given a sample, this filter computes the sample mean
 *
 * The sample is plugged in using SetSample method. Then invoke
 * update() method to compute the sample mean.
 *
 * The sample mean is computed as follows
 * \f$ = \frac{1}{n}\sum^{n}_{i=1}x_{i}\f$ where \f$n\f$ is the
 * number of measurement vectors in the target
 *
 * Recent API changes:
 * The static const macro to get the length of a measurement vector,
 * 'MeasurementVectorSize'  has been removed to allow the length of a measurement
 * vector to be specified at run time. It is now obtained from the input sample.
 * Please use the function GetMeasurementVectorSize() to obtain the length.
 * \ingroup ITKStatistics
 */

template <typename TSample>
class ITK_TEMPLATE_EXPORT MeanSampleFilter : public ProcessObject
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(MeanSampleFilter);

  /**Standard class type aliases. */
  using Self = MeanSampleFilter;
  using Superclass = ProcessObject;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;
  using SampleType = TSample;

  /**Standard Macros */
  itkOverrideGetNameOfClassMacro(MeanSampleFilter);
  itkNewMacro(Self);

  /** Type of each measurement vector in sample */
  using MeasurementVectorType = typename SampleType::MeasurementVectorType;

  /** Type of the length of each measurement vector */
  using MeasurementVectorSizeType = typename SampleType::MeasurementVectorSizeType;

  /** Type of measurement vector component value */
  using MeasurementType = typename SampleType::MeasurementType;

  /** Type of a measurement vector, holding floating point values */
  using MeasurementVectorRealType = typename NumericTraits<MeasurementVectorType>::RealType;

  /** Type of a floating point measurement component value */
  using MeasurementRealType = typename NumericTraits<MeasurementType>::RealType;


  /** Method to set the sample */
  using Superclass::SetInput;
  void
  SetInput(const SampleType * sample);

  /** Method to get the sample */
  const SampleType *
  GetInput() const;


  /** Get the mean measurement vector */
  const MeasurementVectorRealType
  GetMean() const;

  /** MeasurementVector is not a DataObject, we need to decorate it to push it down
   * a ProcessObject's pipeline */
  using MeasurementVectorDecoratedType = SimpleDataObjectDecorator<MeasurementVectorRealType>;
  const MeasurementVectorDecoratedType *
  GetOutput() const;
  using OutputType = MeasurementVectorDecoratedType;


  MeasurementVectorSizeType
  GetMeasurementVectorSize() const;

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

  /** DataObject pointer */
  using DataObjectPointer = DataObject::Pointer;

  using DataObjectPointerArraySizeType = ProcessObject::DataObjectPointerArraySizeType;
  using Superclass::MakeOutput;
  DataObjectPointer
  MakeOutput(DataObjectPointerArraySizeType idx) override;

  void
  GenerateData() override;
}; // end of class
} // end of namespace Statistics
} // end of namespace itk

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

#endif
