#include "cctk.h"
#include "cctk_Functions.h"
#include "cctk_Parameters.h"

subroutine set_coeff_4_2 ( nsize, loc_order, bb, gsize, imin, imax, dd )

  implicit none

  DECLARE_CCTK_FUNCTIONS
  DECLARE_CCTK_PARAMETERS

  CCTK_REAL, parameter :: zero = 0.0
  integer, parameter :: wp = kind(zero)
  CCTK_INT, intent(IN) :: nsize, loc_order
  CCTK_INT, dimension(2), intent(IN) :: bb
  CCTK_INT, intent(IN) :: gsize
  CCTK_INT, dimension(nsize), intent(OUT) :: imin, imax
  CCTK_REAL, dimension(nsize,nsize), intent(OUT) :: dd

  CCTK_REAL, dimension(2), save :: a
  CCTK_REAL, dimension(6,4), save :: q 

  CCTK_INT :: i, il, ir

  logical, save :: first = .true.

  if ( first ) then
    a(1) = 2.0_wp/3.0_wp; a(2) = -1.0_wp/12.0_wp

    q(1,1) = -24.0_wp/17.0_wp; q(2,1) = 59.0_wp/34.0_wp
    q(3,1) = -4.0_wp/17.0_wp; q(4,1) = -3.0_wp/34.0_wp
    q(5,1) = zero; q(6,1) = zero
    q(1,2) = -1.0_wp/2.0_wp; q(2,2) = zero
    q(3,2) = 1.0_wp/2.0_wp; q(4,2) = zero
    q(5,2) = zero; q(6,2) = zero
    q(1,3) = 4.0_wp/43.0_wp; q(2,3) = -59.0_wp/86.0_wp
    q(3,3) = zero; q(4,3) = 59.0_wp/86.0_wp
    q(5,3) = -4.0_wp/43.0_wp; q(6,3) = zero
    q(1,4) = 3.0_wp/98.0_wp; q(2,4) = zero
    q(3,4) = -59.0_wp/98.0_wp; q(4,4) = zero
    q(5,4) = 32.0_wp/49.0_wp; q(6,4) = -4.0_wp/49.0_wp
    first = .false.
  end if

  dd = zero
  imin = 0
  imax = -1

  if ( bb(1) == 0 ) then
    il = 1 + gsize
  else
    dd(1:4,1) = q(1:4,1)
    imin(1) = 1; imax(1) = 4

    dd(1:3,2) = q(1:3,2)
    imin(2) = 1; imax(2) = 3

    dd(1:5,3) = q(1:5,3)
    imin(3) = 1; imax(3) = 5

    dd(1:6,4) = q(1:6,4)
    imin(4) = 1; imax(4) = 6

    il = 5
  end if
  if ( bb(2) == 0 ) then
    ir = nsize - gsize
  else
    dd(nsize-5:nsize,nsize-3) = -q(6:1:-1,4)
    imin(nsize-3) = nsize-5; imax(nsize-3) = nsize

    dd(nsize-4:nsize,nsize-2) = -q(5:1:-1,3)
    imin(nsize-2) = nsize-4; imax(nsize-2) = nsize

    dd(nsize-2:nsize,nsize-1) = -q(3:1:-1,2)
    imin(nsize-1) = nsize-2; imax(nsize-1) = nsize

    dd(nsize-3:nsize,nsize) = -q(4:1:-1,1)
    imin(nsize) = nsize-3; imax(nsize) = nsize
    ir = nsize - 4
  end if
  do i = il, ir
    dd(i-2:i-1,i) = -a(2:1:-1); dd(i+1:i+2,i) = a(1:2)
    imin(i) = i-2; imax(i) = i+2
  end do
end subroutine set_coeff_4_2