!-------------------------------------------------------------------------------

! This file is part of Code_Saturne, a general-purpose CFD tool.
!
! Copyright (C) 1998-2021 EDF S.A.
!
! This program is free software; you can redistribute it and/or modify it under
! the terms of the GNU General Public License as published by the Free Software
! Foundation; either version 2 of the License, or (at your option) any later
! version.
!
! This program is distributed in the hope that it will be useful, but WITHOUT
! ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
! FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
! details.
!
! You should have received a copy of the GNU General Public License along with
! this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
! Street, Fifth Floor, Boston, MA 02110-1301, USA.

!-------------------------------------------------------------------------------

subroutine cfmsfp &
!================

 ( nvar   , nscal  , iterns , ncepdp , ncesmp ,          &
   icepdc , icetsm , itypsm ,                            &
   dt     , vela   ,                                     &
   ckupdc , smacel ,                                     &
   flumas , flumab )

!===============================================================================
! FONCTION :
! ----------

!  "MASS FLUX" AT THE FACES CALCULATION FOR THE CFL RESTRICTION CALCULATION
!   AND THE SOLVING OF THE PRESSURE

!-------------------------------------------------------------------------------
!ARGU                             ARGUMENTS
!__________________.____._____.________________________________________________.
! name             !type!mode ! role                                           !
!__________________!____!_____!________________________________________________!
! nvar             ! i  ! <-- ! total number of variables                      !
! nscal            ! i  ! <-- ! total number of scalars                        !
! iterns           ! i  ! <-- ! Navier-Stokes iteration number                 !
! ncepdp           ! i  ! <-- ! number of cells with head loss                 !
! ncesmp           ! i  ! <-- ! number of cells with mass source term          !
! icepdc(ncelet)   ! te ! <-- ! numero des ncepdp cellules avec pdc            !
! icetsm(ncesmp)   ! te ! <-- ! numero des cellules a source de masse          !
! itypsm           ! te ! <-- ! type de source de masse pour les               !
! dt(ncelet)       ! ra ! <-- ! time step (per cell)                           !
! vela             ! ra ! <-- ! variable value at time step beginning          !
! ckupdc           ! tr ! <-- ! work array for the head loss                   !
!  (ncepdp,6)      !    !     !                                                !
! smacel           ! tr ! <-- ! variable value associated to the mass source   !
! (ncesmp,*)       !    !     ! term (for ivar=ipr, smacel is the mass flux    !
!                  !    !     ! \f$ \Gamma^n \f$)                              !
! flumas(nfac)     ! tr ! --> ! flux de masse aux faces internes               !
! flumab(nfabor)   ! tr ! --> ! flux de masse aux faces de bord                !
!__________________!____!_____!________________________________________________!

!     Type: i (integer), r (real), s (string), a (array), l (logical),
!           and composite types (ex: ra real array)
!     mode: <-- input, --> output, <-> modifies data, --- work array
!===============================================================================

!===============================================================================
! Module files
!===============================================================================

use cfpoin
use paramx
use numvar
use entsor
use optcal
use cstphy
use cstnum
use parall
use period
use ppppar
use ppthch
use ppincl
use mesh
use field
use cs_f_interfaces
use cs_c_bindings

!===============================================================================

implicit none

! Arguments

integer          nvar   , nscal, iterns
integer          ncepdp , ncesmp

integer          icepdc(ncepdp)
integer          icetsm(ncesmp), itypsm(ncesmp,nvar)

double precision dt(ncelet)
double precision ckupdc(6,ncepdp), smacel(ncesmp,nvar)
double precision flumas(nfac), flumab(nfabor)
double precision vela  (3  ,ncelet)

! Local variables

integer          ifac  , iel, ischcp, idftnp, ircflp
integer          init  , inc   , iccocg, isstpp
integer          imrgrp, nswrgp, imligp, iwarnp, iconvp, idiffp
integer          icvflb, f_id0
integer          isou  , jsou
integer          iflmb0, itypfl
integer          itsqdm, imasac

double precision epsrgp, climgp, extrap, thetap, blencp, relaxp
double precision rom

double precision, allocatable, dimension(:) :: w1
double precision, dimension(:), pointer :: crom, brom
double precision, dimension(:), pointer :: viscl, visct
double precision, dimension(:,:), allocatable :: tsexp, gavinj
double precision, allocatable, dimension(:,:) :: vel0
double precision, dimension(:,:,:), allocatable :: tsimp
double precision, allocatable, dimension(:,:,:), target :: viscf
double precision, allocatable, dimension(:,:) :: viscce
double precision, allocatable, dimension(:) :: viscb
double precision, allocatable, dimension(:) :: secvif, secvib
double precision, allocatable, dimension(:,:,:) :: coefbv

double precision, dimension(:,:), pointer :: coefau, cofafu
double precision, dimension(:,:,:), pointer :: coefbu, cofbfu

type(var_cal_opt) :: vcopt_u, vcopt_p

double precision rvoid(1)
!===============================================================================

!===============================================================================
! 1. INITIALISATION
!===============================================================================

call field_get_coefa_v(ivarfl(iu), coefau)
call field_get_coefb_v(ivarfl(iu), coefbu)
call field_get_coefaf_v(ivarfl(iu), cofafu)
call field_get_coefbf_v(ivarfl(iu), cofbfu)

! Allocate work arrays
allocate(w1(ncelet))
allocate(tsexp(3,ncelet))
allocate(gavinj(3,ncelet))
allocate(tsimp(3,3,ncelet))
allocate(coefbv(3,3,nfabor))
allocate(vel0(3,ncelet))

call field_get_key_struct_var_cal_opt(ivarfl(iu), vcopt_u)
call field_get_key_struct_var_cal_opt(ivarfl(ipr), vcopt_p)

if (iand(vcopt_u%idften, ISOTROPIC_DIFFUSION).ne.0) then
  allocate(viscf(1, 1, nfac), viscb(nfabor))
else if (iand(vcopt_u%idften, ANISOTROPIC_LEFT_DIFFUSION).ne.0) then
  allocate(viscf(3, 3, nfac), viscb(nfabor))
  allocate(viscce(6,ncelet))
endif

if (ivisse.eq.1) then
  allocate(secvif(nfac),secvib(nfabor))
endif

f_id0 = -1

! Density

call field_get_val_s(icrom, crom)
call field_get_val_s(ibrom, brom)

!===============================================================================
! 2. MASS FLUX AT THE FACES
!===============================================================================

!     2.1 SOURCE TERMS OF THE MOMENTUM EQUATIONS
!     ==========================================

!     Some first tests (double expansion waves in a shock tube)
!       has shown that taking into account all the
!       momentum equation terms in the mass equation seems to be a
!       bad idea (in particular the convective term, but the diffusive
!       term, the transposed gradient, the mass and user source terms
!       were all null in the considered tests).
!       However, it may be due to a bug at that early stage of implementation
!       of the algorithm (but we didn't find it).
!     We thus recommand not to take into account the momentum source terms,
!       except the gravity term (because it is in balance with the pressure
!       gradient and because its effect is visible at equilibrium).
!     However, we keep here the implementation of the preliminary tests
!       (1.1.0.h version) with an overall test so that the correction is not
!       active (thus, there is no user question and there is always the
!       possibility to perform other tests in the future).
!     Note that, with these terms, the thoeretical analysis is harder
!     (Without these terms we are in the configuration Euler + gravity)

! --- Initialization
do iel = 1, ncel
  do isou = 1, 3
    tsexp(isou,iel) = 0.d0
    do jsou = 1, 3
      tsimp(isou,jsou,iel) = 0.d0
    enddo
  enddo
enddo

!     Test on momentum source terms
itsqdm = 0
if (itsqdm.ne.0) then

  if (ivisse.eq.1) then

    call visecv &
 ( secvif , secvib )

  endif


  ! --- User source term
  call ustsnv &
 ( nvar   , nscal  , ncepdp , ncesmp ,                            &
   iu  ,                                                          &
   icepdc , icetsm , itypsm ,                                     &
   dt     ,                                                       &
   ckupdc , smacel , tsexp  , tsimp )

  ! C version
  call user_source_terms(ivarfl(iu), tsexp, tsimp)

  ! Convective of the momentum equation
  ! in upwind and without reconstruction
  iconvp = vcopt_u%iconv

  init   = 1
  inc    = 1
  iccocg = 1
  iflmb0 = 1
  imrgrp = vcopt_u%imrgra
  nswrgp = vcopt_u%nswrgr
  imligp = vcopt_u%imligr
  iwarnp = vcopt_u%iwarni
  epsrgp = vcopt_u%epsrgr
  climgp = vcopt_u%climgr
  extrap = vcopt_u%extrag
  relaxp = vcopt_u%relaxv
  thetap = vcopt_u%thetav

  itypfl = 1

  ! Mass flux calculation
  call inimav                                                   &
  !==========
( ivarfl(iu)      , itypfl ,                                     &
  iflmb0 , init   , inc    , imrgrp , nswrgp , imligp ,          &
  iwarnp ,                                                       &
  epsrgp , climgp ,                                              &
  crom, brom,                                                    &
  vela,                                                          &
  coefau , coefbu ,                                              &
  flumas , flumab )

  ! ---> Face diffusivity for the velocity
  idiffp = vcopt_u%idiff
  if (idiffp.ge. 1) then

     call field_get_val_s(iviscl, viscl)
     call field_get_val_s(ivisct, visct)

     if (itytur.eq.3) then
        do iel = 1, ncel
           w1(iel) = viscl(iel)
        enddo
     else
        do iel = 1, ncel
           w1(iel) = viscl(iel) + vcopt_u%idifft*visct(iel)
        enddo
     endif

     ! Scalar diffusivity (Default)
     if (iand(vcopt_u%idften, ISOTROPIC_DIFFUSION).ne.0) then

        call viscfa &
        !==========
     ( imvisf ,                                                       &
       w1     ,                                                       &
       viscf  , viscb  )

     ! Tensorial diffusion of the velocity (in case of tensorial porosity)
     else if (iand(vcopt_u%idften, ANISOTROPIC_LEFT_DIFFUSION).ne.0) then

        do iel = 1, ncel
          do isou = 1, 3
            viscce(isou, iel) = w1(iel)
          enddo
          do isou = 4, 6
            viscce(isou, iel) = 0.d0
          enddo
        enddo

        call vistnv (imvisf, viscce, viscf, viscb)

     endif

  ! --- If no diffusion, viscosity is set to 0.
  else

     do ifac = 1, nfac
       viscf(1,1,ifac) = 0.d0
     enddo
     do ifac = 1, nfabor
       viscb(ifac) = 0.d0
     enddo

  endif

  idftnp = vcopt_u%idften

  ! no recontruction
  ircflp = 0;

  ! upwind
  ischcp = 0;
  blencp = 0;
  isstpp = 0;

  inc = 1;

  icvflb = 0;

  ! The added convective scalar mass flux is:
  !      (thetap*Y_\face-imasac*Y_\celli)*mf.
  ! When building the implicit part of the rhs, one
  ! has to impose 1 on mass accumulation.
  imasac = 1

  call bilscv &
  !==========
( idtvar , ivarfl(iu)      , iconvp , idiffp , nswrgp , imligp , ircflp , &
  ischcp , isstpp , inc    , imrgrp , ivisse ,                            &
  iwarnp , idftnp , imasac ,                                              &
  blencp , epsrgp , climgp , relaxp , thetap ,                            &
  vela   , vela   ,                                                       &
  coefau , coefbu , cofafu , cofbfu ,                                     &
  flumas , flumab , viscf  , viscb  , secvif , secvib ,                   &
  rvoid  , rvoid  , rvoid  ,                                              &
  icvflb , icvfli ,                                                       &
  tsexp  )

endif

! End of the test on momentum source terms

! Mass source term
if (ncesmp.gt.0) then

  ! The momentum balance is used in its conservative form here
  ! so the mass source term is only composed of gamma*uinj
  ! => array of previous velocity has to be set to zero

  do iel = 1, ncel
    do isou = 1,3
      vel0(isou,iel) = 0.d0
    enddo
  enddo

  call catsmv(ncesmp, iterns, icetsm, itypsm(:,iu),                      &
              cell_f_vol, vel0, smacel(:,iu), smacel(:,ipr),             &
              tsexp, tsimp, gavinj)

  do iel = 1, ncel
    do isou = 1, 3
      tsexp(isou,iel) = tsexp(isou,iel) + gavinj(isou,iel)
    enddo
  enddo

endif

! --- Volumic forces term (gravity)
do iel = 1, ncel
  rom = crom(iel)
  tsexp(1,iel) = gx + tsexp(1,iel)/rom
  tsexp(2,iel) = gy + tsexp(2,iel)/rom
  tsexp(3,iel) = gz + tsexp(3,iel)/rom
enddo

! --- Calculation of the convective "velocities at the cell centers
!     (Calculation of u^n+dt*f^n)

do iel = 1, ncel
  do isou = 1, 3
    tsexp(isou,iel) = dt(iel)*tsexp(isou,iel)
  enddo
enddo

! Computation of the flux

! volumic flux part based on dt*f^n

! Initialization of the mass flux
init   = 1
! As mentioned above, for homogeneous Neumann
inc    = 0
iccocg = 1
iflmb0 = 1
! Reconstruction is useless here
nswrgp = 0 ! FIXME
imrgrp = vcopt_p%imrgra
imligp = vcopt_p%imligr
iwarnp = vcopt_p%iwarni
epsrgp = vcopt_p%epsrgr
climgp = vcopt_p%climgr
extrap = vcopt_p%extrag

! Velocity flux (crom, brom not used)
itypfl = 0

! No contribution of f to the boundary mass flux
do ifac = 1, nfabor
  do isou = 1, 3
    do jsou = 1, 3
      coefbv(isou,jsou,ifac) = 0.d0
    enddo
  enddo
enddo

call inimav                                                      &
!==========
( f_id0  , itypfl ,                                              &
  iflmb0 , init   , inc    , imrgrp , nswrgp , imligp ,          &
  iwarnp ,                                                       &
  epsrgp , climgp ,                                              &
  crom, brom,                                                    &
  tsexp,                                                         &
  coefau , coefbv ,                                              &
  flumas , flumab )

! volumic flux part based on velocity u^n
init   = 0
! take into account Dirichlet velocity boundary conditions
inc    = 1

call inimav                                                      &
!==========
( ivarfl(iu)      , itypfl ,                                     &
  iflmb0 , init   , inc    , imrgrp , nswrgp , imligp ,          &
  iwarnp ,                                                       &
  epsrgp , climgp ,                                              &
  crom, brom,                                                    &
  vela,                                                          &
  coefau , coefbu ,                                              &
  flumas , flumab )

! Free memory
deallocate(w1)
deallocate(tsexp)
deallocate(gavinj)
deallocate(tsimp)
deallocate(viscf, viscb)
if (allocated(secvif)) deallocate(secvif, secvib)
if (allocated(viscce)) deallocate(viscce)
deallocate(coefbv)
deallocate(vel0)

!--------
! FORMATS
!--------


!----
! FIN
!----

return

end subroutine
