!!******************************************************************************
!!
!!  This file is part of the AMUN source code, a program to perform
!!  Newtonian or relativistic magnetohydrodynamical simulations on uniform or
!!  adaptive mesh.
!!
!!  Copyright (C) 2017 Grzegorz Kowal <grzegorz@amuncode.org>
!!
!!  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 3 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, see <http://www.gnu.org/licenses/>.
!!
!!*****************************************************************************
!!
!! module: FORCING
!!
!!  This module provides energy injection, e.g. turbulence driving, supernova
!!  explosions, etc.
!!
!!*****************************************************************************
!
module forcing

#ifdef PROFILE
! import external subroutines
!
  use timers, only : set_timer, start_timer, stop_timer
#endif /* PROFILE */

! module variables are not implicit by default
!
  implicit none

#ifdef PROFILE
! timer indices
!
  integer, save :: ifi, ifu
#endif /* PROFILE */

! flag indicating if the energy injection is enabled
!
  logical, save :: forcing_enabled = .false.

! by default everything is private
!
  private

! declare public subroutines
!
  public :: initialize_forcing, finalize_forcing
  public :: update_forcing

!- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
!
  contains
!
!===============================================================================
!!
!!***  PUBLIC SUBROUTINES  *****************************************************
!!
!===============================================================================
!
!===============================================================================
!
! subroutine INITIALIZE_FORCING:
! -----------------------------
!
!   Subroutine initializes module FORCING.
!
!   Arguments:
!
!     verbose - flag determining if the subroutine should be verbose;
!     iret    - return flag of the procedure execution status;
!
!===============================================================================
!
  subroutine initialize_forcing(verbose, iret)

! import external procedures and variables
!
    use parameters, only : get_parameter_string

! local variables are not implicit by default
!
    implicit none

! subroutine arguments
!
    logical, intent(in)    :: verbose
    integer, intent(inout) :: iret

! local variables
!
    character(len=64) :: injection_method = "none"
!
!-------------------------------------------------------------------------------
!
#ifdef PROFILE
! set timer descriptions
!
    call set_timer('forcing:: initialization', ifi)
    call set_timer('forcing:: update'        , ifu)

! start accounting time for initialization/finalization
!
    call start_timer(ifi)
#endif /* PROFILE */

! obtain the chosen injection method
!
    call get_parameter_string("injection_method", injection_method)

! select the energy injection method
!
    select case(trim(injection_method))
    case default
      injection_method = "none"
    end select

! print information about the energy injection
!
    if (verbose) then

      write (*,"(4x,a16, 7x,'=',1x,a)") "energy injection"                     &
                                                      , trim(injection_method)

    end if

#ifdef PROFILE
! stop accounting time
!
    call stop_timer(ifi)
#endif /* PROFILE */

!-------------------------------------------------------------------------------
!
  end subroutine initialize_forcing
!
!===============================================================================
!
! subroutine FINALIZE_FORCING:
! ---------------------------
!
!   Subroutine releases memory used by the module variables.
!
!   Arguments:
!
!     iret    - return flag of the procedure execution status;
!
!===============================================================================
!
  subroutine finalize_forcing(iret)

! local variables are not implicit by default
!
    implicit none

! subroutine arguments
!
    integer, intent(inout) :: iret
!
!-------------------------------------------------------------------------------
!
#ifdef PROFILE
! start accounting time for initialization/finalization
!
    call start_timer(ifi)
#endif /* PROFILE */

#ifdef PROFILE
! stop accounting time
!
    call stop_timer(ifi)
#endif /* PROFILE */

!-------------------------------------------------------------------------------
!
  end subroutine finalize_forcing
!
!===============================================================================
!
! subroutine UPDATE_FORCING:
! -------------------------
!
!   Subroutine adds the energy injection terms.
!
!   Arguments:
!
!     t, dt - time and its increment;
!
!===============================================================================
!
  subroutine update_forcing(t, dt)

! local variables are not implicit by default
!
    implicit none

! subroutine arguments
!
    real(kind=8), intent(in) :: t, dt
!
!-------------------------------------------------------------------------------
!
#ifdef PROFILE
! start accounting time for forcing term update
!
    call start_timer(ifu)
#endif /* PROFILE */

! proceed only if forcing is enabled
!
    if (forcing_enabled) then

    end if ! forcing enabled

#ifdef PROFILE
! stop accounting time
!
    call stop_timer(ifu)
#endif /* PROFILE */

!-------------------------------------------------------------------------------
!
  end subroutine update_forcing

!===============================================================================
!
end module forcing