/*=========================================================================
 *
 *  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 itkFEMLoadEdge_h
#define itkFEMLoadEdge_h

#include "itkFEMLoadElementBase.h"
#include "ITKFEMExport.h"
#include "vnl/vnl_matrix.h"

namespace itk
{
namespace fem
{
/**
 * \class LoadEdge
 * \brief A generic load that can be applied to an edge of the element.
 *
 * Can also be used to apply natural (Neumann) boundary condition on the
 * edge of the element. In this case m_Edge defines the edge or surface
 * of the element on which the BC exists and matrix m_Force holds the actual
 * prescribed values of the BC.
 * \ingroup ITKFEM
 */
class ITKFEM_EXPORT LoadEdge : public LoadElement
{
public:
  /** Standard class type aliases. */
  using Self = LoadEdge;
  using Superclass = LoadElement;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** New macro for creation of through the object factory. */
  itkSimpleNewMacro(Self);

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

  /** CreateAnother method will clone the existing instance of this type,
   * including its internal member variables. */
  itk::LightObject::Pointer
  CreateAnother() const override;

  /**
   * Set the edge number on which the force is being applied
   */
  void
  SetEdge(int edge);

  /**
   * Get the edge number on which the force is being applied
   */
  int
  GetEdge() const;

  /**
   * Set the edge force values
   */
  void
  SetForce(const vnl_matrix<itk::fem::Element::Float> force);

  /**
   * Get the edge force values
   */
  const vnl_matrix<itk::fem::Element::Float> &
  GetForce() const;
  vnl_matrix<itk::fem::Element::Float> &
  GetForce();

  /** Apply the load to the specified element */
  void
  ApplyLoad(Element::ConstPointer element, Element::VectorType & Fe) override;

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

  /**
   * Local number of the edge (face) of the element on which the load acts.
   * Check the corresponding element class for more info on edge numbering.
   */
  int m_Edge{};

  /**
   * An edge force matrix. This matrix specifies nodal forces on all
   * nodes within the edge or face on which the load acts. Each nodal
   * force is decomposed into several components (check the documentation
   * inside the element class). In case of 2D elements this components
   * are normal (1st component) and tangential (2nd component) force
   * acting on the edge of the element. A positive normal load acts in
   * a direction INTO the element. A positive tangential load acts in
   * an ANTICLOCKWISE direction with respect to the loaded element.
   * Each nodal force is stored in a column of the matrix. The number
   * of columns in the Force matrix must correspond to the number of
   * nodes that define the edge (face...). The force is interpolated
   * over the entire edge (face) by using the shape functions of the
   * element. Again check the documentation of the element class to which
   * the force is applied.
   */
  vnl_matrix<Float> m_Force{};
};
} // end namespace fem
} // end namespace itk

#endif // itkFEMLoadEdge_h