! (C) Copyright 2005- ECMWF.
!
! This software is licensed under the terms of the Apache Licence Version 2.0
! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
!
! In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
! virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
!
! Description: How to read data for a given beam from scatterometer BUFR messages.
!
! Please note that scatterometer data can be encoded in various ways in BUFR. Therefore the code
! below might not work directly for other types of messages than the one used in the
! example. It is advised to use bufr_dump first to understand the structure of these messages.

program bufr_read_scatterometer
   use eccodes
   implicit none
   integer            :: ifile
   integer            :: iret
   integer            :: ibufr
   integer            :: i, count = 0
   integer(kind=4)    :: numObs, ii
   real(kind=8), dimension(:), allocatable :: latVal, lonVal, bscatterVal
   real(kind=8), dimension(:), allocatable :: year

   call codes_open_file(ifile, '../../data/bufr/asca_139.bufr', 'r')

   ! The first BUFR message is loaded from file,
   ! ibufr is the bufr id to be used in subsequent calls
   call codes_bufr_new_from_file(ifile, ibufr, iret)

   do while (iret /= CODES_END_OF_FILE)

      write (*, '(A,I3)') 'message: ', count

      ! We need to instruct ecCodes to expand all the descriptors
      ! i.e. unpack the data values
      call codes_set(ibufr, "unpack", 1);
      ! The BUFR file contains a single message with 2016 subsets in a compressed form.
      ! It means each subset has exactly the same structure: they store one location with
      ! several beams and one backscatter value in each beam.
      !
      ! To print the backScatter values for beamIdentifier=2 from all the subsets
      ! we will simply access the key by condition (see below).

      ! Read the total number of subsets.
      call codes_get(ibufr, 'numberOfSubsets', numObs)

      write (*, '(A,I5)') "Number of values:", numObs

      ! Get latitude (for all the subsets)
      call codes_get(ibufr, 'latitude', latVal);
      ! Get longitude (for all the subsets)
      call codes_get(ibufr, 'longitude', lonVal);
      allocate (year(numObs))
      call codes_get(ibufr, 'year', year);
      do ii = 1, size(year)
         write (*, '(A,I4,A,F8.1)') 'year(', ii, ')=', year(ii)
      end do

      ! Get backScatter for beam two. We use an access by condition for this key.
      ! (for all the subsets)
      call codes_get(ibufr, '/beamIdentifier=2/backscatter', bscatterVal);
      ! Check that all arrays are same size
      if (size(latVal) /= numObs .or. size(lonVal) /= numObs .or. size(bscatterVal) /= numObs) then
         print *, 'inconsistent array dimension'
         exit
      end if

      ! Print the values
      write (*, *) 'pixel   lat    lon     backscatter'
      write (*, *) "--------------------------------------"

      do i = 1, numObs
         write (*, '(I4,3F10.5)') i, latVal(i), lonVal(i), bscatterVal(i)
      end do

      ! Free arrays
      deallocate (latVal)
      deallocate (lonVal)
      deallocate (bscatterVal)

      ! Release the bufr message
      call codes_release(ibufr)

      ! Load the next bufr message
      call codes_bufr_new_from_file(ifile, ibufr, iret)

      count = count + 1

   end do

   ! Close file
   call codes_close_file(ifile)

end program bufr_read_scatterometer
