#ifndef IGL_MASSMATRIX_H
#define IGL_MASSMATRIX_H
#include "igl_inline.h"

#define EIGEN_YES_I_KNOW_SPARSE_MODULE_IS_NOT_STABLE_YET
#include <Eigen/Dense>
#include <Eigen/Sparse>

namespace igl 
{

  enum MassMatrixType
  {
    MASSMATRIX_BARYCENTRIC,
    MASSMATRIX_VORONOI,
    MASSMATRIX_FULL
  };
#define NUM_MASSMATRIXTYPE 3

  // Constructs the mass (area) matrix for a given mesh (V,F).
  //
  // Templates:
  //   DerivedV  derived type of eigen matrix for V (e.g. derived from
  //     MatrixXd)
  //   DerivedF  derived type of eigen matrix for F (e.g. derived from
  //     MatrixXi)
  //   Scalar  scalar type for eigen sparse matrix (e.g. double)
  // Inputs:
  //   V  #V by dim list of mesh vertex positions
  //   F  #F by simplex_size list of mesh faces (must be triangles)
  //   type  one of the following ints:
  //     IGL_MASSMATRIX_BARYCENTRIC  barycentric
  //     IGL_MASSMATRIX_VORONOI voronoi-hybrid {default}
  //     IGL_MASSMATRIX_FULL full {not implemented}
  // Outputs: 
  //   M  #V by #V mass matrix
  //
  // See also: adjacency_matrix
  //
  template <typename DerivedV, typename DerivedF, typename Scalar>
  IGL_INLINE void massmatrix(
    const Eigen::MatrixBase<DerivedV> & V, 
    const Eigen::MatrixBase<DerivedF> & F, 
    const MassMatrixType type,
    Eigen::SparseMatrix<Scalar>& M);
}

#ifdef IGL_HEADER_ONLY
#  include "massmatrix.cpp"
#endif

#endif