interface

  !> Create a tree and return its pointer
  !! @param tree_ctx     pointer to the tree
  subroutine Createtree_(tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    type(c_ptr), intent(out) :: tree_ctx
  end subroutine

  !> Delete the tree and free memeory
  !! @param tree_ctx     pointer to the tree
  subroutine DeleteTree(tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Get the node list for the tree
  !! @param node_coord   coordinates of each tree node {x1,y1,z1,x2,y2,z2,...}
  !! @param parent_lst   index of the parent node if it exists; -1 otherwise
  !! @param child_lst    index of 8 child nodes if it has children; -1 otherwise
  !! @param node_depth   depth of the tree node
  !! @param node_ghost   1 if the node is a ghost node; 0 otherwise
  !! @param node_leaf    1 if the node is a leaf  node; 0 otherwise
  !! @param Nnodes       number of tree nodes
  !! @param tree_ctx     pointer to the tree
  subroutine GetTree(node_coord, parent_lst, child_lst, node_depth, node_ghost, node_leaf, Nnodes, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    type(c_ptr), intent(out) :: node_coord  ! real*8, dimension(Nnode*3)
    type(c_ptr), intent(out) :: parent_lst  ! integer*4, dimension(Nnode)
    type(c_ptr), intent(out) :: child_lst   ! integer*4, dimension(Nnode*8)
    type(c_ptr), intent(out) :: node_depth  ! integer*1, dimension(Nnode)
    type(c_ptr), intent(out) :: node_ghost  ! integer*1, dimension(Nnode)
    type(c_ptr), intent(out) :: node_leaf   ! integer*1, dimension(Nnode)
    integer*4  , intent(out) :: Nnodes
    type(c_ptr), intent(in)  :: tree_ctx
  end subroutine

  !> Change refinement of the tree
  !! @param pt_coord         coordinates of the points
  !! @param Npt              number of points
  !! @param max_pts          maximum number of points per tree node
  !! @param level_restrict   .true. to enable level restriction
  !! @param periodic         .true. for periodic level restriction
  !! @param tree_ctx         pointer to the tree
  subroutine UpdateRefinement(pt_coord, Npt, max_pts, level_restrict, periodic, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    real*8     , intent(in) :: pt_coord(*)
    integer*4  , intent(in) :: Npt
    integer*4  , intent(in) :: max_pts
    logical    , intent(in) :: level_restrict
    logical    , intent(in) :: periodic
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Add some data to the tree nodes (for example multipole expansions)
  !! @param data_name   name for the data
  !! @param node_data   data array
  !! @param Ndata       length of the data array
  !! @param cnt         array of data-length for each node
  !! @param Ncnt        length of cnt array (must be equal to #-of-nodes)
  !! @param tree_ctx    pointer to the tree
  subroutine AddData(data_name, node_data, Ndata, cnt, Ncnt, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: data_name(*)
    real*8     , intent(in) :: node_data(*)
    integer*4  , intent(in) :: Ndata
    integer*4  , intent(in) :: cnt(*)
    integer*4  , intent(in) :: Ncnt
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Get node data from the tree
  !! @param node_data   data array
  !! @param Ndata       length of the data array
  !! @param cnt         array of data-length for each node
  !! @param Ncnt        length of cnt array (equal to #-of-nodes)
  !! @param data_name   name for the data
  !! @param tree_ctx    pointer to the tree
  subroutine GetData(node_data, Ndata, cnt, Ncnt, data_name, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    type(c_ptr), intent(out) :: node_data  ! real*8   , dimension(Ndata)
    integer*4  , intent(out) :: Ndata
    type(c_ptr), intent(out) :: cnt        ! integer*4, dimension(Ncnt)
    integer*4  , intent(out) :: Ncnt
    character  , intent(in)  :: data_name(*)
    type(c_ptr), intent(in)  :: tree_ctx
  end subroutine

  !> Delete node data from the tree
  !! @param data_name   name for the data
  !! @param tree_ctx    pointer to the tree
  subroutine DeleteData(data_name, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: data_name(*)
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Write VTK output
  !! @param fname       name of output file
  !! @param show_ghost  .true. to show ghost nodes
  !! @param tree_ctx    pointer to the tree
  subroutine WriteTreeVTK(fname, show_ghost, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: fname(*)
    logical    , intent(in) :: show_ghost
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine


  !> Add particles to the tree
  !! @param pt_name     name of the particles
  !! @param coord       coordinates of the particles {x1,y1,z1,x2,y2,...}
  !! @param Npt         number of particles
  !! @param tree_ctx    pointer to the tree
  subroutine AddParticles(pt_name, coord, Npt, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: pt_name
    real*8     , intent(in) :: coord(*)
    integer*4  , intent(in) :: Npt
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Associate some data with the particles (for example charge density). The
  !! data must be in the original order of the points.
  !! @param pt_name     name of the particles
  !! @param data_name   name of the data
  !! @param pt_data     data array
  !! @param Ndata       size of the data array
  !! @param tree_ctx    pointer to the tree
  subroutine AddParticleData(data_name, pt_name, pt_data, Ndata, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: data_name(*)
    character  , intent(in) :: pt_name(*)
    real*8     , intent(in) :: pt_data(*)
    integer*4  , intent(in) :: Ndata
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Get data associated with the particles. The output array will be ordered
  !! according to the original ordering of the points
  !! @param pt_data     data array
  !! @param Ndata       size of the data array
  !! @param data_name   name of the data
  !! @param tree_ctx    pointer to the tree
  subroutine GetParticleData(pt_data, Ndata, data_name, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    type(c_ptr), intent(out) :: pt_data    ! real*8, dimension(N)
    integer*4  , intent(out) :: Ndata
    character  , intent(in)  :: data_name(*)
    type(c_ptr), intent(in)  :: tree_ctx
  end subroutine

  !> Delete data associated with a particle (or a particle and all its data)
  !! @param data_name   name of the data (or particle)
  !! @param tree_ctx    pointer to the tree
  subroutine DeleteParticleData(data_name, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: data_name
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

  !> Write VTK output
  !! @param fname       name of output file
  !! @param data_name   name of the data
  !! @param show_ghost  .true. to show ghost nodes
  !! @param tree_ctx    pointer to the tree
  subroutine WriteParticleVTK(fname, data_name, show_ghost, tree_ctx)
    use, intrinsic :: ISO_C_BINDING
    character  , intent(in) :: fname(*)
    character  , intent(in) :: data_name(*)
    logical    , intent(in) :: show_ghost
    type(c_ptr), intent(in) :: tree_ctx
  end subroutine

end interface