//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//============================================================================

#ifndef vtk_m_filter_particle_density_ngp_hxx
#define vtk_m_filter_particle_density_ngp_hxx

#include "ParticleDensityNearestGridPoint.h"
#include <vtkm/cont/CellLocatorUniformGrid.h>
#include <vtkm/cont/DataSetBuilderUniform.h>
#include <vtkm/filter/PolicyBase.h>
#include <vtkm/worklet/WorkletMapField.h>

namespace vtkm
{
namespace worklet
{
class NGPWorklet : public vtkm::worklet::WorkletMapField
{
public:
  using ControlSignature = void(FieldIn coords, ExecObject locator, AtomicArrayInOut density);
  using ExecutionSignature = void(_1, _2, _3);

  template <typename Point, typename CellLocatorExecObj, typename AtomicArray>
  VTKM_EXEC void operator()(const Point& point,
                            const CellLocatorExecObj& locator,
                            AtomicArray& density) const
  {
    vtkm::Id cellId{};
    vtkm::Vec3f parametric;

    // Find the cell containing the point
    if (locator->FindCell(point, cellId, parametric) == vtkm::ErrorCode::Success)
    {
      // increment density
      density.Add(cellId, 1);
    }

    // FIXME: what does mean when it is not found?
    // We simply ignore that particular particle.
  }
}; //NGPWorklet
} //worklet
} //vtkm


namespace vtkm
{
namespace filter
{
inline VTKM_CONT ParticleDensityNearestGridPoint::ParticleDensityNearestGridPoint(
  const vtkm::Id3& dimension,
  const vtkm::Vec3f& origin,
  const vtkm::Vec3f& spacing)
  : Dimension(dimension)
  , Origin(origin)
  , Spacing(spacing)
{
}

ParticleDensityNearestGridPoint::ParticleDensityNearestGridPoint(const Id3& dimension,
                                                                 const vtkm::Bounds& bounds)
  : Dimension(dimension)
  , Origin({ static_cast<vtkm::FloatDefault>(bounds.X.Min),
             static_cast<vtkm::FloatDefault>(bounds.Y.Min),
             static_cast<vtkm::FloatDefault>(bounds.Z.Min) })
  , Spacing(vtkm::Vec3f{ static_cast<vtkm::FloatDefault>(bounds.X.Length()),
                         static_cast<vtkm::FloatDefault>(bounds.Y.Length()),
                         static_cast<vtkm::FloatDefault>(bounds.Z.Length()) } /
            Dimension)
{
}

template <typename T, typename StorageType, typename Policy>
inline VTKM_CONT vtkm::cont::DataSet ParticleDensityNearestGridPoint::DoExecute(
  const vtkm::cont::DataSet&,
  const vtkm::cont::ArrayHandle<T, StorageType>& field,
  const vtkm::filter::FieldMetadata&,
  vtkm::filter::PolicyBase<Policy>)
{
  // TODO: it really doesn't need to be a UniformGrid, any CellSet with CellLocator will work.
  //  Make it another input rather an output generated.

  // We stores density as CellField which conforms to physicists' idea of particle density
  // better. However, VTK/VTKm's idea of "Image" Dataset and the ImageConnectivity filter
  // expect a PointField. For better separation of concerns, we create a uniform dataset
  // that has the cell dimension as expected and later convert the dataset to its dual.
  auto uniform = vtkm::cont::DataSetBuilderUniform::Create(
    this->Dimension + vtkm::Id3{ 1, 1, 1 }, this->Origin, this->Spacing);

  // Create a CellLocator
  vtkm::cont::CellLocatorUniformGrid locator;
  locator.SetCellSet(uniform.GetCellSet());
  locator.SetCoordinates(uniform.GetCoordinateSystem());
  locator.Update();

  // We create an ArrayHandle and pass it to the Worklet as AtomicArrayInOut.
  // However the ArrayHandle needs to be allocated and initialized first. The
  // easily way to do it is to copy from an ArrayHandleConstant
  vtkm::cont::ArrayHandle<vtkm::Id> density;
  vtkm::cont::ArrayCopy(vtkm::cont::ArrayHandleConstant<vtkm::Id>(0, uniform.GetNumberOfCells()),
                        density);

  this->Invoke(vtkm::worklet::NGPWorklet{}, field, locator, density);

  uniform.AddField(vtkm::cont::make_FieldCell("density", density));

  return uniform;
}

}
}
#endif //vtk_m_filter_particle_density_ngp_hxx