!--------------------------------------------------------------------------------------------------
!> @author Pratheek Shanthraj, Max-Planck-Institut für Eisenforschung GmbH
!> @author Luv Sharma, Max-Planck-Institut für Eisenforschung GmbH
!> @brief material subroutine incoprorating isotropic brittle damage source mechanism
!> @details to be done
!--------------------------------------------------------------------------------------------------
submodule(constitutive:constitutive_damage) source_damage_isoBrittle

  integer,                       dimension(:),           allocatable :: &
    source_damage_isoBrittle_offset, &
    source_damage_isoBrittle_instance

  type :: tParameters                                                                               !< container type for internal constitutive parameters
    real(pReal) :: &
      critStrainEnergy, &                                                                           !< critical elastic strain energy
      N                              
    character(len=pStringLen), allocatable, dimension(:) :: &
      output
  end type tParameters

  type(tParameters), dimension(:), allocatable :: param                                             !< containers of constitutive parameters (len Ninstance)

contains


!--------------------------------------------------------------------------------------------------
!> @brief module initialization
!> @details reads in material parameters, allocates arrays, and does sanity checks
!--------------------------------------------------------------------------------------------------
module function source_damage_isoBrittle_init(source_length) result(mySources)

  integer, intent(in)                  :: source_length  
  logical, dimension(:,:), allocatable :: mySources

  class(tNode), pointer :: &
    phases, &
    phase, &
    sources, &
    src
  integer :: Ninstance,sourceOffset,NipcMyPhase,p
  character(len=pStringLen) :: extmsg = ''

  write(6,'(/,a)') ' <<<+-  source_damage_isoBrittle init  -+>>>'

  mySources = source_active('damage_isoBrittle',source_length)
  
  Ninstance = count(mySources)
  write(6,'(a16,1x,i5,/)') '# instances:',Ninstance; flush(6)
  if(Ninstance == 0) return

  phases => material_root%get('phase')
  allocate(param(Ninstance))
  allocate(source_damage_isoBrittle_offset  (phases%length), source=0)
  allocate(source_damage_isoBrittle_instance(phases%length), source=0)

  do p = 1, phases%length
    phase => phases%get(p) 
    if(any(mySources(:,p))) source_damage_isoBrittle_instance(p) = count(mySources(:,1:p))
    if(count(mySources(:,p)) == 0) cycle
    sources => phase%get('source')
    do sourceOffset = 1, sources%length
      if(mySources(sourceOffset,p)) then
        source_damage_isoBrittle_offset(p) = sourceOffset
        associate(prm  => param(source_damage_isoBrittle_instance(p)))
        src => sources%get(sourceOffset) 

        prm%N                = src%get_asFloat('m')
        prm%critStrainEnergy = src%get_asFloat('W_crit')

#if defined (__GFORTRAN__)
        prm%output = output_asStrings(src)
#else
        prm%output = src%get_asStrings('output',defaultVal=emptyStringArray)
#endif
 
        ! sanity checks
        if (prm%N                <= 0.0_pReal) extmsg = trim(extmsg)//' m'
        if (prm%critStrainEnergy <= 0.0_pReal) extmsg = trim(extmsg)//' W_crit'

        NipcMyPhase = count(material_phaseAt==p) * discretization_nIP
        call constitutive_allocateState(sourceState(p)%p(sourceOffset),NipcMyPhase,1,1,1)
        sourceState(p)%p(sourceOffset)%atol = src%get_asFloat('isoBrittle_atol',defaultVal=1.0e-3_pReal)
        if(any(sourceState(p)%p(sourceOffset)%atol < 0.0_pReal)) extmsg = trim(extmsg)//' isobrittle_atol'

        end associate

!--------------------------------------------------------------------------------------------------
!  exit if any parameter is out of range
        if (extmsg /= '') call IO_error(211,ext_msg=trim(extmsg)//'(damage_isoBrittle)')
      endif
    enddo
  enddo


end function source_damage_isoBrittle_init


!--------------------------------------------------------------------------------------------------
!> @brief calculates derived quantities from state
!--------------------------------------------------------------------------------------------------
module subroutine source_damage_isoBrittle_deltaState(C, Fe, ipc, ip, el)

  integer, intent(in) :: &
    ipc, &                                                                                          !< component-ID of integration point
    ip, &                                                                                           !< integration point
    el                                                                                              !< element
  real(pReal),  intent(in), dimension(3,3) :: &
    Fe
  real(pReal),  intent(in), dimension(6,6) :: &
    C

  integer :: &
    phase, &
    constituent, &
    sourceOffset
  real(pReal), dimension(6) :: &
    strain
  real(pReal) :: &
    strainenergy

  phase = material_phaseAt(ipc,el)                                                                  !< phase ID at ipc,ip,el
  constituent = material_phasememberAt(ipc,ip,el)                                                   !< state array offset for phase ID at ipc,ip,el
  sourceOffset = source_damage_isoBrittle_offset(phase)

  strain = 0.5_pReal*math_sym33to6(matmul(transpose(Fe),Fe)-math_I3)

  associate(prm => param(source_damage_isoBrittle_instance(phase)))
  strainenergy = 2.0_pReal*sum(strain*matmul(C,strain))/prm%critStrainEnergy
  ! ToDo: check strainenergy = 2.0_pReal*dot_product(strain,matmul(C,strain))/param(instance)%critStrainEnergy

  if (strainenergy > sourceState(phase)%p(sourceOffset)%subState0(1,constituent)) then
    sourceState(phase)%p(sourceOffset)%deltaState(1,constituent) = &
      strainenergy - sourceState(phase)%p(sourceOffset)%state(1,constituent)
  else
    sourceState(phase)%p(sourceOffset)%deltaState(1,constituent) = &
      sourceState(phase)%p(sourceOffset)%subState0(1,constituent) - &
      sourceState(phase)%p(sourceOffset)%state(1,constituent)
  endif
  end associate

end subroutine source_damage_isoBrittle_deltaState


!--------------------------------------------------------------------------------------------------
!> @brief returns local part of nonlocal damage driving force
!--------------------------------------------------------------------------------------------------
module subroutine source_damage_isoBrittle_getRateAndItsTangent(localphiDot, dLocalphiDot_dPhi, phi, phase, constituent)

  integer, intent(in) :: &
    phase, &
    constituent
  real(pReal),  intent(in) :: &
    phi
  real(pReal),  intent(out) :: &
    localphiDot, &
    dLocalphiDot_dPhi

  integer :: &
    sourceOffset

  sourceOffset = source_damage_isoBrittle_offset(phase)

  associate(prm => param(source_damage_isoBrittle_instance(phase)))
  localphiDot = (1.0_pReal - phi)**(prm%n - 1.0_pReal) &
              - phi*sourceState(phase)%p(sourceOffset)%state(1,constituent)
  dLocalphiDot_dPhi = - (prm%n - 1.0_pReal)* (1.0_pReal - phi)**max(0.0_pReal,prm%n - 2.0_pReal) &
                      - sourceState(phase)%p(sourceOffset)%state(1,constituent)
  end associate

end subroutine source_damage_isoBrittle_getRateAndItsTangent


!--------------------------------------------------------------------------------------------------
!> @brief writes results to HDF5 output file
!--------------------------------------------------------------------------------------------------
module subroutine source_damage_isoBrittle_results(phase,group)

  integer,          intent(in) :: phase
  character(len=*), intent(in) :: group

  integer :: o

  associate(prm => param(source_damage_isoBrittle_instance(phase)), &
            stt => sourceState(phase)%p(source_damage_isoBrittle_offset(phase))%state)
  outputsLoop: do o = 1,size(prm%output)
    select case(trim(prm%output(o)))
      case ('f_phi')
        call results_writeDataset(group,stt,trim(prm%output(o)),'driving force','J/m³')
    end select
  enddo outputsLoop
  end associate

end subroutine source_damage_isoBrittle_results

end submodule source_damage_isoBrittle