MODULE sao_intp
   !!======================================================================
   !!                    ***  MODULE sao_intp ***
   !! ** Purpose : Run NEMO observation operator in offline mode
   !!======================================================================
   !! NEMO modules
   USE in_out_manager
   USE diaobs
   !! Stand Alone Observation operator modules
   USE sao_read
   USE sao_data

   IMPLICIT NONE
   PRIVATE

   PUBLIC sao_interp

   CONTAINS

      SUBROUTINE sao_interp
         !!----------------------------------------------------------------------
         !!                    ***  SUBROUTINE sao_interp ***
         !!
         !! ** Purpose : To interpolate the model as if it were running online.
         !!
         !! ** Method : 1. Populate model counterparts
         !!             2. Call dia_obs at appropriate time steps
         !!----------------------------------------------------------------------
         INTEGER :: istp ! time step index
         !! Loop over entire run
         istp = nit000 - 1
         nstop = 0
         DO WHILE ( istp <= nitend .AND. nstop == 0 )
            IF (jifile <= n_files + 1) THEN
               IF ( MOD(istp, nn_sao_freq) == nit000 ) THEN
                  !! Read next model counterpart
                  CALL sao_rea_dri(jifile)
                  jifile = jifile + 1
               ENDIF
               !! Interpolate single time step
               CALL dia_obs(istp)
            ENDIF
            !! Increment model step
            istp = istp + 1
         END DO
      END SUBROUTINE sao_interp

END MODULE sao_intp