!***********************************************************************
! This file is part of OpenMolcas.                                     *
!                                                                      *
! OpenMolcas is free software; you can redistribute it and/or modify   *
! it under the terms of the GNU Lesser General Public License, v. 2.1. *
! OpenMolcas is distributed in the hope that it will be useful, but it *
! is provided "as is" and without any express or implied warranties.   *
! For more details see the full text of the license in the file        *
! LICENSE or in <http://www.gnu.org/licenses/>.                        *
!                                                                      *
! Copyright (C) 1991, Roland Lindh                                     *
!               2003, Hans-Joachim Werner                              *
!***********************************************************************

subroutine Drv1_Pot(FD,CCoor,pot,ngrid,ncmp,nordop)
!***********************************************************************
!                                                                      *
! Object: to compute the potential on a grid using density FD (triang) *
!         Grid provided in CCoor(3,ngrid)                              *
!         Potential values returned in pot                             *
!                                                                      *
! Generated by modification of drv_rf.f, naint.f, sogthr.f             *
! H.-J. Werner, Jan 2003                                               *
!***********************************************************************

use Index_Functions, only: nTri_Elem1
use Symmetry_Info, only: nIrrep
use Real_Spherical, only: ipSph, RSph
use iSD_data, only: iSD
use Basis_Info, only: dbsc, MolWgh, Shells
use Center_Info, only: dc
use Sizes_of_Seward, only: S
#ifdef _DEBUGPRINT_
use define_af, only: AngTp
use Symmetry_Info, only: ChOper
#endif
use stdalloc, only: mma_allocate, mma_deallocate
use Constants, only: Zero, One, Two, Three
use Definitions, only: wp, iwp, u6

implicit none
integer(kind=iwp), intent(in) :: ngrid, ncmp, nordop
real(kind=wp), intent(in) :: FD(*), CCoor(3,ngrid)
real(kind=wp), intent(out) :: pot(ncmp,ngrid)
integer(kind=iwp) :: iAng, iAO, iBas, iCmp, iCnt, iCnttp, iDCRR(0:7), iDCRT(0:7), igeo, iPrim, iS, iShell, iShll, iSmLbl, &
                     iStabM(0:7), iStabO(0:7), iuv, jAng, jAO, jBas, jCmp, jCnt, jCnttp, jPrim, jS, jShell, jShll, kk, lDCRR, &
                     lDCRT, lFinal, LmbdR, LmbdT, loper, mdci, mdcj, MemKer, nComp, nDAO, nDCRR, nDCRT, nOp(3), nOrder, nScr1, &
                     nScr2, nSkal, nSO, nStabM, nStabO
#ifdef _DEBUGPRINT_
integer(kind=iwp) :: i
#endif
real(kind=wp) :: A(3), B(3), FactNd, RB(3), TA(3), TRB(3), XX, YY, ZZ
real(kind=wp), allocatable :: DAO(:), DSO(:), DSOp(:), Kappa(:), Kern(:), PCoor(:,:), rFinal(:), Scrt1(:), Scrt2(:), Zeta(:), &
                              ZInv(:)
real(kind=wp), parameter :: ThreeI = One/Three
integer(kind=iwp), external :: MemSO1, n2Tri, NrOpr

!                                                                      *
!***********************************************************************
!                                                                      *
loper = 2**nIrrep-1
nComp = nTri_Elem1(nOrdOp)
if (ncomp /= ncmp) then
  call WarningMessage(2,'Drv1_pot: ncmp < ncomp')
  write(u6,*) 'ncmp < ncomp:',ncmp,ncomp
  call Abend()
end if
pot(:,:) = Zero

! Auxiliary memory allocation.

call mma_allocate(Zeta,S%m2Max,label='Zeta')
call mma_allocate(ZInv,S%m2Max,label='ZInv')
call mma_allocate(Kappa,S%m2Max,label='Kappa')
call mma_allocate(PCoor,S%m2Max,3,label='PCoor')
!                                                                      *
!***********************************************************************
!                                                                      *
call Nr_Shells(nSkal)
!                                                                      *
!***********************************************************************
!                                                                      *
! Double loop over shells. These loops decide the integral type

do iS=1,nSkal
  iShll = iSD(0,iS)
  iAng = iSD(1,iS)
  iCmp = iSD(2,iS)
  iBas = iSD(3,iS)
  iPrim = iSD(5,iS)
  iAO = iSD(7,iS)
  mdci = iSD(10,iS)
  iShell = iSD(11,iS)
  iCnttp = iSD(13,iS)
  iCnt = iSD(14,iS)
  A(1:3) = dbsc(iCnttp)%Coor(1:3,iCnt)
  do jS=1,iS
    jShll = iSD(0,jS)
    jAng = iSD(1,jS)
    jCmp = iSD(2,jS)
    jBas = iSD(3,jS)
    jPrim = iSD(5,jS)
    jAO = iSD(7,jS)
    mdcj = iSD(10,jS)
    jShell = iSD(11,jS)
    jCnttp = iSD(13,jS)
    jCnt = iSD(14,jS)
    B(1:3) = dbsc(jCnttp)%Coor(1:3,jCnt)

    iSmLbl = 1
    nSO = MemSO1(iSmLbl,iCmp,jCmp,iShell,jShell,iAO,jAO)
    if (nSO == 0) cycle
#   ifdef _DEBUGPRINT_
    write(u6,'(A,A,A,A,A)') ' ***** (',AngTp(iAng),',',AngTp(jAng),') *****'
#   endif

    ! Call kernel routine to get memory requirement.

    !call NAMem(nOrder,MemKer,iAng,jAng,nOrdOp)
    call EFMmP(nOrder,MemKer,iAng,jAng,nOrdOp)
    call mma_allocate(Kern,MemKer*S%m2Max,label='Kernel')

    ! Allocate memory for the final integrals, all in the primitive basis.

    lFinal = 1
    if (nOrdOp /= 0) lFinal = S%MaxPrm(iAng)*S%MaxPrm(jAng)*nTri_Elem1(iAng)*nTri_Elem1(jAng)*nComp
    call mma_allocate(rFinal,lFinal,label='Final')

    ! Scratch area for contraction step

    nScr1 = S%MaxPrm(iAng)*S%MaxPrm(jAng)*nTri_Elem1(iAng)*nTri_Elem1(jAng)
    call mma_allocate(Scrt1,nScr1,label='Scrtch')

    ! Scratch area for the transformation to spherical gaussians

    nScr2 = S%MaxPrm(iAng)*S%MaxPrm(jAng)*nTri_Elem1(iAng)*nTri_Elem1(jAng)
    call mma_allocate(Scrt2,nScr2,label='ScrSph')

    nDAO = iPrim*jPrim*nTri_Elem1(iAng)*nTri_Elem1(jAng)
    call mma_allocate(DAO,nDAO,label='DAO')

    ! At this point we can compute Zeta.

    call ZXia(Zeta,ZInv,iPrim,jPrim,Shells(iShll)%Exp,Shells(jShll)%Exp)

    ! Find the DCR for A and B

    call DCR(LmbdR,dc(mdci)%iStab,dc(mdci)%nStab,dc(mdcj)%iStab,dc(mdcj)%nStab,iDCRR,nDCRR)
#   ifdef _DEBUGPRINT_
    write(u6,'(10A)') ' {R}=(',(ChOper(iDCRR(i)),i=0,nDCRR-1),')'
#   endif

    ! Find the stabilizer for A and B

    call Inter(dc(mdci)%iStab,dc(mdci)%nStab,dc(mdcj)%iStab,dc(mdcj)%nStab,iStabM,nStabM)

    ! Allocate memory for the elements of the Fock or 1st order
    ! density matrix which are associated with the current shell pair.

    call mma_allocate(DSOp,nSO*iPrim*jPrim,label='DSOpr')
    call mma_allocate(DSO,nSO*iPrim*jPrim,label='DSO')

    ! Gather the elements from 1st order density / Fock matrix.

    call SOGthr(DSO,iBas,jBas,nSO,FD,n2Tri(iSmLbl),iSmLbl,iCmp,jCmp,iShell,jShell,iAO,jAO)

    ! Project the Fock/1st order density matrix in AO
    ! basis on to the primitive basis.

#   ifdef _DEBUGPRINT_
    call RecPrt(' Left side contraction',' ',Shells(iShll)%pCff,iPrim,iBas)
    call RecPrt(' Right side contraction',' ',Shells(jShll)%pCff,jPrim,jBas)
#   endif

    ! Transform IJ,AB to J,ABi
    call DGEMM_('T','T',jBas*nSO,iPrim,iBas,One,DSO,iBas,Shells(iShll)%pCff,iPrim,Zero,DSOp,jBas*nSO)
    ! Transform J,ABi to AB,ij
    call DGEMM_('T','T',nSO*iPrim,jPrim,jBas,One,DSOp,jBas,Shells(jShll)%pCff,jPrim,Zero,DSO,nSO*iPrim)
    ! Transpose to ij,AB
    call DGeTmO(DSO,nSO,nSO,iPrim*jPrim,DSOp,iPrim*jPrim)
    call mma_deallocate(DSO)

#   ifdef _DEBUGPRINT_
    call RecPrt(' Decontracted 1st order density/Fock matrix',' ',DSOp,iPrim*jPrim,nSO)
#   endif

    ! Loops over symmetry operations.

    do lDCRR=0,nDCRR-1
      call OA(iDCRR(lDCRR),B,RB)

      ! Generate stabilizer of the operator.

      call SOS(iStabO,nStabO,lOper)

      ! Find the DCR for M and S

      call DCR(LmbdT,iStabM,nStabM,iStabO,nStabO,iDCRT,nDCRT)
#     ifdef _DEBUGPRINT_
      write(u6,'(10A)') ' {M}=(',(ChOper(iStabM(i)),i=0,nStabM-1),')'
      write(u6,'(10A)') ' {O}=(',(ChOper(iStabO(i)),i=0,nStabO-1),')'
      write(u6,'(10A)') ' {T}=(',(ChOper(iDCRT(i)),i=0,nDCRT-1),')'
#     endif

      ! Compute normalization factor due the DCR symmetrization
      ! of the two basis functions and the operator.

      iuv = dc(mdci)%nStab*dc(mdcj)%nStab
      FactNd = real(iuv*nStabO,kind=wp)/real(nIrrep**2*LmbdT,kind=wp)
      if (MolWgh == 1) then
        FactNd = FactNd*real(nIrrep**2,kind=wp)/real(iuv,kind=wp)
      else if (MolWgh == 2) then
        FactNd = sqrt(real(iuv*nStabO,kind=wp)/real(nIrrep*LmbdT,kind=wp))
      end if

      do lDCRT=0,nDCRT-1
        nOp(1) = NrOpr(iDCRT(lDCRT))
        nOp(2) = NrOpr(ieor(iDCRT(lDCRT),iDCRR(lDCRR)))
        nOp(3) = NrOpr(0)

        call OA(iDCRT(lDCRT),A,TA)
        call OA(iDCRT(lDCRT),RB,TRB)
#       ifdef _DEBUGPRINT_
        write(u6,'(A,/,3(3F6.2,2X))') ' *** Centers A, B, C ***',(TA(i),i=1,3),(TRB(i),i=1,3)
        write(u6,*) ' nOp=',nOp
#       endif

        ! Desymmetrize the matrix with which we will contract the trace.

        call DesymD(iSmLbl,iAng,jAng,iCmp,jCmp,iShell,jShell,iShll,jShll,iAO,jAO,DAO,iPrim,jPrim,DSOp,nSO,nOp,FactNd)

        ! Project the spherical harmonic space onto the cartesian space.

        kk = nTri_Elem1(iAng)*nTri_Elem1(jAng)
        if (Shells(iShll)%Transf .or. Shells(jShll)%Transf) then

          ! ij,AB --> AB,ij
          call DGeTmO(DAO,iPrim*jPrim,iPrim*jPrim,iCmp*jCmp,Scrt1,iCmp*jCmp)
          ! AB,ij --> ij,ab
          call SphCar(Scrt1,iCmp*jCmp,iPrim*jPrim,Scrt2,nScr2,RSph(ipSph(iAng)),iAng,Shells(iShll)%Transf,Shells(iShll)%Prjct, &
                      RSph(ipSph(jAng)),jAng,Shells(jShll)%Transf,Shells(jShll)%Prjct,DAO,kk)
        end if
#       ifdef _DEBUGPRINT_
        call RecPrt(' Decontracted FD in the cartesian space',' ',DAO,iPrim*jPrim,kk)
#       endif

        ! Compute kappa and P.

        call Setup1(Shells(iShll)%Exp,iPrim,Shells(jShll)%Exp,jPrim,TA,TRB,Kappa,PCoor,ZInv)

        ! Compute primitive potential integrals and trace with density

        call potintd(Zeta,ZInv,Kappa,PCoor,iPrim*jPrim,iAng,jAng,TA,TRB,Kern,MemKer,rFinal,lFinal,nDAO,Ccoor,pot,ngrid,ncmp,DAO, &
                     nOrdOp)

      end do
    end do

    call mma_deallocate(Kern)
    call mma_deallocate(rFinal)
    call mma_deallocate(Scrt1)
    call mma_deallocate(Scrt2)
    call mma_deallocate(DAO)
    call mma_deallocate(DSOp)
  end do
end do
if (nOrdOp == 2) then
  ! modifify field gradients to get traceless form
  do igeo=1,ngrid
    XX = Two*pot(1,igeo)-pot(4,igeo)-pot(6,igeo)
    YY = Two*pot(4,igeo)-pot(1,igeo)-pot(6,igeo)
    ZZ = Two*pot(6,igeo)-pot(4,igeo)-pot(1,igeo)
    pot(1,igeo) = XX*ThreeI
    pot(4,igeo) = YY*ThreeI
    pot(6,igeo) = ZZ*ThreeI
  end do
end if

call mma_deallocate(Zeta)
call mma_deallocate(ZInv)
call mma_deallocate(Kappa)
call mma_deallocate(PCoor)

return

end subroutine Drv1_Pot
