!> @file user_spectra.f90
!--------------------------------------------------------------------------------------------------!
! This file is part of the PALM model system.
!
! PALM 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.
!
! PALM 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 PALM. If not, see
! <http://www.gnu.org/licenses/>.
!
! Copyright 1997-2021 Leibniz Universitaet Hannover
!--------------------------------------------------------------------------------------------------!
!
!
! Description:
! ------------
!> Calculation of user-defined spectra.
!> See section 3.5.4 on how to define, calculate, and output user defined quantities.
!--------------------------------------------------------------------------------------------------!
 SUBROUTINE user_spectra( mode, m, pr )


    USE arrays_3d

    USE control_parameters

    USE indices

    USE kinds

    USE spectra_mod

    USE statistics

    USE user

    IMPLICIT NONE

    CHARACTER(LEN=*) ::  mode  !<

    INTEGER(iwp) ::  m   !<
    INTEGER(iwp) ::  pr  !<


!
!-- Next line is to avoid compiler warning about unused variable. Please remove.
    IF ( pr == 0 )  CONTINUE

!
!-- Sample on how to calculate spectra of user-defined quantities. Each quantity is identified by
!-- the corresponding user profile index "pr_palm+#" where "#" is an integer starting from 1. These
!-- user-profile-numbers must also be assigned to the respective strings given by
!-- data_output_pr_user in routine user_check_data_output_pr.
    IF ( mode == 'preprocess' )  THEN

       SELECT CASE ( TRIM( data_output_sp(m) ) )

          CASE ( 'u', 'v', 'w', 'theta', 'q', 's' )
!--          Not allowed here since these are the standard quantities used in preprocess_spectra.

!          CASE ( 'u*v*' )
!             pr = pr_palm+1
!             d(nzb+1:nzt,nys:nyn,nxl:nxr) = ustvst(nzb+1:nzt,nys:nyn,nxl:nxr)

          CASE DEFAULT
             message_string = 'Spectra of ' // TRIM( data_output_sp(m) ) // ' can not be calculated'
             CALL message( 'user_spectra', 'UI0010', 0, 1, 0, 6, 0 )

       END SELECT

    ELSEIF ( mode == 'data_output' )  THEN

       SELECT CASE ( TRIM( data_output_sp(m) ) )

          CASE ( 'u', 'v', 'w', 'theta', 'q', 's' )
!--          Not allowed here since these are the standard quantities used in data_output_spectra.

!          CASE ( 'u*v*' )
!             pr = 6

          CASE DEFAULT
             message_string = 'Spectra of ' // TRIM( data_output_sp(m) ) // ' are not defined'
             CALL message( 'user_spectra', 'UI0011', 0, 0, 0, 6, 0 )

          END SELECT

    ENDIF

 END SUBROUTINE user_spectra