!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright (C) 2000 - 2017  CP2K developers group                                               !
!--------------------------------------------------------------------------------------------------!

! **************************************************************************************************
!> \brief builds the input structure for the FORCE_EVAL section of cp2k
!> \par History
!>      06.2004 created [fawzi]
!> \author fawzi
! **************************************************************************************************
MODULE input_cp2k_force_eval
   USE cp_output_handling,              ONLY: add_last_numeric,&
                                              cp_print_key_section_create,&
                                              high_print_level,&
                                              low_print_level,&
                                              medium_print_level
   USE cp_units,                        ONLY: cp_unit_to_cp2k
   USE input_constants,                 ONLY: &
        do_eip, do_fist, do_mixed, do_qmmm, do_qs, do_stress_analytical, do_stress_diagonal_anal, &
        do_stress_diagonal_numer, do_stress_none, do_stress_numerical, numerical
   USE input_cp2k_dft,                  ONLY: create_bsse_section,&
                                              create_dft_section
   USE input_cp2k_eip,                  ONLY: create_eip_section
   USE input_cp2k_mixed,                ONLY: create_mix_section
   USE input_cp2k_mm,                   ONLY: create_mm_section
   USE input_cp2k_properties_dft,       ONLY: create_properties_section
   USE input_cp2k_qmmm,                 ONLY: create_qmmm_section
   USE input_cp2k_subsys,               ONLY: create_subsys_section
   USE input_keyword_types,             ONLY: keyword_create,&
                                              keyword_release,&
                                              keyword_type
   USE input_section_types,             ONLY: section_add_keyword,&
                                              section_add_subsection,&
                                              section_create,&
                                              section_release,&
                                              section_type
   USE input_val_types,                 ONLY: char_t,&
                                              integer_t,&
                                              lchar_t,&
                                              real_t
   USE kinds,                           ONLY: dp
   USE string_utilities,                ONLY: s2a
#include "./base/base_uses.f90"

   IMPLICIT NONE
   PRIVATE

   LOGICAL, PRIVATE, PARAMETER :: debug_this_module = .TRUE.
   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'input_cp2k_force_eval'

   PUBLIC :: create_force_eval_section

CONTAINS

! **************************************************************************************************
!> \brief creates the force_eval section
!> \param section the section to be created
!> \author fawzi
! **************************************************************************************************
   SUBROUTINE create_force_eval_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_force_eval_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, name="force_eval", &
                          description="parameters needed to calculate energy and forces and"// &
                          " describe the system you want to analyze.", &
                          n_keywords=1, n_subsections=9, repeats=.TRUE.)

      NULLIFY (subsection)
      NULLIFY (keyword)
      CALL keyword_create(keyword, name="METHOD", &
                          description="Which method should be used to compute forces", &
                          usage="METHOD <STRING>", &
                          enum_c_vals=s2a("QS", &
                                          "FIST", &
                                          "QMMM", &
                                          "EIP", &
                                          "QUICKSTEP", &
                                          "MIXED"), &
                          enum_desc=s2a("Alias for QUICKSTEP", &
                                        "Molecular Mechanics", &
                                        "Hybrid quantum classical", &
                                        "Empirical Interatomic Potential", &
                                        "Electronic structure methods (DFT, ...)", &
                                        "Use a combination of two of the above"), &
                          enum_i_vals=(/do_qs, do_fist, do_qmmm, do_eip, do_qs, do_mixed/), &
                          default_i_val=do_qs)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="STRESS_TENSOR", &
                          description="Controls the calculation of the stress tensor. The combinations defined below"// &
                          " are not implemented for all methods.", &
                          usage="stress_tensor (NONE|ANALYTICAL|NUMERICAL|DIAGONAL_ANA|DIAGONAL_NUM)", &
                          default_i_val=do_stress_none, &
                          enum_c_vals=s2a("NONE", "ANALYTICAL", "NUMERICAL", "DIAGONAL_ANALYTICAL", "DIAGONAL_NUMERICAL"), &
                          enum_i_vals=(/do_stress_none, do_stress_analytical, do_stress_numerical, &
                                        do_stress_diagonal_anal, do_stress_diagonal_numer/), &
                          enum_desc=s2a("Do not compute stress tensor", &
                                        "Compute the stress tensor analytically (if available).", &
                                        "Compute the stress tensor numerically.", &
                                        "Compute the diagonal part only of the stress tensor analytically (if available).", &
                                        "Compute the diagonal part only of the stress tensor numerically"))

      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="EMBED", &
                          description="Activates exporting electronic densities of the subsystems in DFET.", &
                          usage="EMBED FALSE", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)

      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL create_ext_pot_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_rescale_force_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_mix_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_dft_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_mm_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_qmmm_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_eip_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_bsse_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_subsys_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_properties_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_f_env_print_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_force_eval_section

! **************************************************************************************************
!> \brief Creates the section for applying an external potential
!> \param section ...
!> \date 03.2008
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_ext_pot_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_ext_pot_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, name="EXTERNAL_POTENTIAL", &
                          description="Section controlling the presence of an external potential dependent "// &
                          " on the atomic positions (X,Y,Z)", &
                          n_keywords=7, n_subsections=0, repeats=.TRUE.)
      NULLIFY (keyword)

      CALL keyword_create(keyword, name="ATOMS_LIST", &
                          description="Specifies the atoms on which the external potential will act", &
                          usage="ATOMS_LIST {INT} {INT} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="FUNCTION", &
                          description="Specifies the functional form in mathematical notation. Variables must be the atomic "// &
                          "coordinates (X,Y,Z).", usage="FUNCTION  X^2+Y^2+Z^2+LOG(ABS(X+Y))", &
                          type_of_var=lchar_t, n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="PARAMETERS", &
                          description="Defines the parameters of the functional form", &
                          usage="PARAMETERS a b D", type_of_var=char_t, &
                          n_var=-1, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="VALUES", &
                          description="Defines the values of  parameter of the functional form", &
                          usage="VALUES ", type_of_var=real_t, &
                          n_var=-1, repeats=.TRUE., unit_str="internal_cp2k")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="UNITS", &
                          description="Optionally, allows to define valid CP2K unit strings for each parameter value. "// &
                          "It is assumed that the corresponding parameter value is specified in this unit.", &
                          usage="UNITS angstrom eV*angstrom^-1 angstrom^1 K", type_of_var=char_t, &
                          n_var=-1, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="DX", &
                          description="Parameter used for computing the derivative with the Ridders' method.", &
                          usage="DX <REAL>", default_r_val=0.1_dp, unit_str="bohr")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="ERROR_LIMIT", &
                          description="Checks that the error in computing the derivative is not larger than "// &
                          "the value set; in case error is larger a warning message is printed.", &
                          usage="ERROR_LIMIT <REAL>", default_r_val=1.0E-12_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_ext_pot_section

! **************************************************************************************************
!> \brief Creates the section controlling the rescaling of forces
!> \param section the section to create
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_rescale_force_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_rescale_force_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, name="RESCALE_FORCES", &
                          description="Section controlling the rescaling of forces. Useful when"// &
                          " starting from quite bad geometries with unphysically large forces.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword)

      CALL keyword_create(keyword, name="MAX_FORCE", &
                          description="Specify the Maximum Values of the force. If the force"// &
                          " of one atom exceed this value it's rescaled to the MAX_FORCE"// &
                          " value.", &
                          default_r_val=cp_unit_to_cp2k(value=50.0_dp, &
                                                        unit_str="kcalmol*angstrom^-1"), &
                          unit_str="hartree*bohr^-1")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_rescale_force_section

! **************************************************************************************************
!> \brief ...
!> \param section ...
!> \author fawzi
! **************************************************************************************************
   SUBROUTINE create_f_env_print_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_f_env_print_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: print_key

      NULLIFY (keyword)
      NULLIFY (print_key)

      CPASSERT(.NOT. ASSOCIATED(section))

      CALL section_create(section, name="PRINT", &
                          description="Properties that you want to output and that are common to all methods", &
                          n_keywords=0, n_subsections=5, repeats=.FALSE.)

      CALL cp_print_key_section_create(print_key, "PROGRAM_RUN_INFO", &
                                       description="Controls the printing of basic information generated by force_eval", &
                                       print_level=low_print_level, add_last=add_last_numeric, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create(print_key, "FORCES", &
                                       description="Controls the printing of the forces after each force evaluation", &
                                       print_level=high_print_level, filename="__STD_OUT__")
      CALL keyword_create(keyword=keyword, &
                          name="NDIGITS", &
                          description="Specifies the number of digits used "// &
                          "for the printing of the forces", &
                          usage="NDIGITS 6", &
                          default_i_val=8, &
                          repeats=.FALSE.)
      CALL section_add_keyword(print_key, keyword)
      CALL keyword_release(keyword)
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create( &
         print_key, "GRID_INFORMATION", &
         description="Controls the printing of information regarding the PW and RS grid structures.", &
         print_level=medium_print_level, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create(print_key, "TOTAL_NUMBERS", &
                                       description="Controls the printing of the total number of atoms, kinds,...", &
                                       print_level=medium_print_level, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create(print_key, "DISTRIBUTION", &
                                       description="Controls the printing of the distribution of molecules, atoms, ...", &
                                       print_level=medium_print_level, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create(print_key, "DISTRIBUTION2D", &
                                       description="Controls the printing of the distribution of matrix blocks,...", &
                                       print_level=high_print_level, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create(print_key, "DISTRIBUTION1D", &
                                       description="Each node prints out its distribution info ...", &
                                       print_level=high_print_level, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL cp_print_key_section_create(print_key, "STRESS_TENSOR", &
                                       description="Controls the printing of the stress tensor", &
                                       print_level=high_print_level, filename="__STD_OUT__")
      CALL keyword_create(keyword=keyword, &
                          name="NDIGITS", &
                          description="Specifies the number of digits used "// &
                          "for the printing of the stress tensor", &
                          usage="NDIGITS 6", &
                          default_i_val=8, &
                          repeats=.FALSE.)
      CALL section_add_keyword(print_key, keyword)
      CALL keyword_release(keyword)
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

   END SUBROUTINE create_f_env_print_section

END MODULE input_cp2k_force_eval
