!--------------------------------------------------------------------------------------------------
!> @author Martin Diehl, Max-Planck-Institut für Eisenforschung GmbH
!> @author Franz Roters, Max-Planck-Institut für Eisenforschung GmbH
!> @author Philip Eisenlohr, Max-Planck-Institut für Eisenforschung GmbH
!> @brief Isostrain (full constraint Taylor assuption) homogenization scheme
!--------------------------------------------------------------------------------------------------
module homogenization_mech_isostrain

  implicit none
  private
  enum, bind(c) 
    enumerator :: &
      parallel_ID, &
      average_ID
  end enum
 
  type, private :: tParameters                                                                      !< container type for internal constitutive parameters
    integer :: &
      Nconstituents
    integer(kind(average_ID)) :: &
      mapping
  end type
 
  type(tParameters), dimension(:), allocatable, private :: param                                    !< containers of constitutive parameters (len Ninstance)
 
  public :: &
    homogenization_isostrain_init, &
    homogenization_isostrain_partitionDeformation, &
    homogenization_isostrain_averageStressAndItsTangent

contains

!--------------------------------------------------------------------------------------------------
!> @brief allocates all neccessary fields, reads information from material configuration file
!--------------------------------------------------------------------------------------------------
subroutine homogenization_isostrain_init
  use debug, only: &
    debug_HOMOGENIZATION, &
    debug_level, &
    debug_levelBasic
  use IO, only: &
    IO_error
  use material, only: &
    homogenization_type, &
    material_homogenizationAt, &
    homogState, &
    HOMOGENIZATION_ISOSTRAIN_ID, &
    HOMOGENIZATION_ISOSTRAIN_LABEL, &
    homogenization_typeInstance
  use config, only: &
    config_homogenization
  
  implicit none
  integer :: &
    Ninstance, &
    h, &
    NofMyHomog
  character(len=65536) :: &
    tag  = ''
 
  write(6,'(/,a)')   ' <<<+-  homogenization_'//HOMOGENIZATION_ISOSTRAIN_label//' init  -+>>>'
 
  Ninstance = count(homogenization_type == HOMOGENIZATION_ISOSTRAIN_ID)
  if (iand(debug_level(debug_HOMOGENIZATION),debug_levelBasic) /= 0) &
    write(6,'(a16,1x,i5,/)') '# instances:',Ninstance
 
  allocate(param(Ninstance))                                                                        ! one container of parameters per instance
 
  do h = 1, size(homogenization_type)
    if (homogenization_type(h) /= HOMOGENIZATION_ISOSTRAIN_ID) cycle
    
    associate(prm => param(homogenization_typeInstance(h)),&
              config => config_homogenization(h))
   
    prm%Nconstituents = config_homogenization(h)%getInt('nconstituents')
    tag = 'sum'
    select case(trim(config%getString('mapping',defaultVal = tag)))
      case ('sum')
        prm%mapping = parallel_ID
      case ('avg')
        prm%mapping = average_ID
      case default
        call IO_error(211,ext_msg=trim(tag)//' ('//HOMOGENIZATION_isostrain_label//')')
    end select
 
    NofMyHomog = count(material_homogenizationAt == h)
    homogState(h)%sizeState       = 0
    homogState(h)%sizePostResults = 0
    allocate(homogState(h)%state0   (0,NofMyHomog))
    allocate(homogState(h)%subState0(0,NofMyHomog))
    allocate(homogState(h)%state    (0,NofMyHomog))
    
    end associate
 
  enddo

end subroutine homogenization_isostrain_init


!--------------------------------------------------------------------------------------------------
!> @brief partitions the deformation gradient onto the constituents
!--------------------------------------------------------------------------------------------------
subroutine homogenization_isostrain_partitionDeformation(F,avgF)
  use prec, only: &
    pReal
  
  implicit none
  real(pReal),   dimension (:,:,:), intent(out) :: F                                                !< partitioned deformation gradient
  
  real(pReal),   dimension (3,3),   intent(in)  :: avgF                                             !< average deformation gradient at material point
 
  F = spread(avgF,3,size(F,3))

end subroutine homogenization_isostrain_partitionDeformation


!--------------------------------------------------------------------------------------------------
!> @brief derive average stress and stiffness from constituent quantities 
!--------------------------------------------------------------------------------------------------
subroutine homogenization_isostrain_averageStressAndItsTangent(avgP,dAvgPdAvgF,P,dPdF,instance)
  use prec, only: &
    pReal
  
  implicit none
  real(pReal),   dimension (3,3),       intent(out) :: avgP                                         !< average stress at material point
  real(pReal),   dimension (3,3,3,3),   intent(out) :: dAvgPdAvgF                                   !< average stiffness at material point
 
  real(pReal),   dimension (:,:,:),     intent(in)  :: P                                            !< partitioned stresses
  real(pReal),   dimension (:,:,:,:,:), intent(in)  :: dPdF                                         !< partitioned stiffnesses
  integer,                              intent(in)  :: instance 
 
  associate(prm => param(instance))
  
  select case (prm%mapping)
    case (parallel_ID)
      avgP       = sum(P,3)
      dAvgPdAvgF = sum(dPdF,5)
    case (average_ID)
      avgP       = sum(P,3)   /real(prm%Nconstituents,pReal)
      dAvgPdAvgF = sum(dPdF,5)/real(prm%Nconstituents,pReal)
  end select
  
  end associate

end subroutine homogenization_isostrain_averageStressAndItsTangent

end module homogenization_mech_isostrain