! (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 get values using keys from GRIB messages
!
!
program grib_get_keys
   use eccodes
   implicit none

   integer                            ::  ifile
   integer                            ::  iret
   integer                            ::  igrib
   real                               ::  latitudeOfFirstPointInDegrees
   real                               ::  longitudeOfFirstPointInDegrees
   real                               ::  latitudeOfLastPointInDegrees
   real                               ::  longitudeOfLastPointInDegrees
   integer(4)                         ::  numberOfPointsAlongAParallel
   integer(8)                         ::  numberOfPointsAlongAMeridian
   real, dimension(:), allocatable    ::  values
   integer                            ::  numberOfValues
   real                               ::  average, min_val, max_val
   integer                            ::  is_missing, is_defined
   character(len=10)                  ::  open_mode = 'r'

   call codes_open_file(ifile, '../../data/reduced_latlon_surface.grib1', open_mode)

   ! loop on all the messages in a file
   LOOP: DO WHILE (.true.)
      ! a new GRIB message is loaded from file.
      ! igrib is the grib id to be used in subsequent calls
      call codes_grib_new_from_file(ifile, igrib, iret)
      if (iret == CODES_END_OF_FILE) exit LOOP

      ! check key is defined
      is_defined = 0
      call codes_is_defined(igrib, 'Ni', is_defined)
      write (*, *) 'Key Ni is defined? ', is_defined

      ! check if the value of the key is MISSING
      is_missing = 0
      call codes_is_missing(igrib, 'Ni', is_missing)
      if (is_missing /= 1) then
         ! key value is not missing so get as an integer
         call codes_get(igrib, 'Ni', numberOfPointsAlongAParallel)
         write (*, *) 'numberOfPointsAlongAParallel=', &
            numberOfPointsAlongAParallel
      else
         write (*, *) 'numberOfPointsAlongAParallel is missing'
      end if

      ! get as an integer
      call codes_get(igrib, 'Nj', numberOfPointsAlongAMeridian)
      write (*, *) 'numberOfPointsAlongAMeridian=', &
         numberOfPointsAlongAMeridian

      ! get as a real
      call codes_get(igrib, 'latitudeOfFirstGridPointInDegrees', &
                     latitudeOfFirstPointInDegrees)
      write (*, *) 'latitudeOfFirstGridPointInDegrees=', &
         latitudeOfFirstPointInDegrees

      ! get as a real
      call codes_get(igrib, 'longitudeOfFirstGridPointInDegrees', &
                     longitudeOfFirstPointInDegrees)
      write (*, *) 'longitudeOfFirstGridPointInDegrees=', &
         longitudeOfFirstPointInDegrees

      ! get as a real
      call codes_get(igrib, 'latitudeOfLastGridPointInDegrees', &
                     latitudeOfLastPointInDegrees)
      write (*, *) 'latitudeOfLastGridPointInDegrees=', &
         latitudeOfLastPointInDegrees

      ! get as a real
      call codes_get(igrib, 'longitudeOfLastGridPointInDegrees', &
                     longitudeOfLastPointInDegrees)
      write (*, *) 'longitudeOfLastGridPointInDegrees=', &
         longitudeOfLastPointInDegrees

      ! get the size of the values array
      call codes_get_size(igrib, 'values', numberOfValues)
      write (*, *) 'numberOfValues=', numberOfValues

      allocate (values(numberOfValues), stat=iret)
      ! get data values
      call codes_get(igrib, 'values', values)
      call codes_get(igrib, 'min', min_val) ! can also be obtained through minval(values)
      call codes_get(igrib, 'max', max_val) ! can also be obtained through maxval(values)
      call codes_get(igrib, 'average', average) ! can also be obtained through maxval(values)

      deallocate (values)

      write (*, *) 'There are ', numberOfValues, &
         ' average is ', average, &
         ' min is ', min_val, &
         ' max is ', max_val

      call codes_release(igrib)

   end do LOOP

   call codes_close_file(ifile)

end program grib_get_keys