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! (C) Copyright 2005-2016 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 create a new GRIB message from a sample.
!               
!
program sample
  use eccodes
  implicit none  
  integer  :: err
  integer  :: outfile, datafile
  integer  :: igribsample,igribclone,igribdata, size1
  integer  :: date1, startStep, endStep, table2Version, indicatorOfParameter
  integer  :: decimalPrecision
  character(len=10) stepType
  real(kind=8), dimension(:), allocatable   :: v1,v2,v 

  date1 = 20080104
  startStep = 0
  endStep = 12
  stepType = 'accum'
  table2Version = 2
  indicatorOfParameter = 61
  decimalPrecision = 2

  !     A new grib message is loaded from an existing sample.
  !     Samples are searched in a default sample path (use codes_info
  !     to see where that is). The default sample path can be changed by
  !     setting the environment variable ECCODES_SAMPLES_PATH
  call codes_grib_new_from_samples(igribsample, "regular_latlon_surface.grib1")

  call codes_open_file(outfile, 'f_out.samples.grib1','w')
  call codes_open_file(datafile,'../../data/tp_ecmwf.grib','r')

  call codes_grib_new_from_file(datafile,igribdata,err)

  call codes_get_size(igribdata,'values',size1)
  allocate(v(size1))
  allocate(v1(size1))
  allocate(v2(size1))

  call codes_get(igribdata,'values',v)

  v=v*1000.0 ! different units for the output grib
  v1=v

  do while (err/=CODES_END_OF_FILE) 
 
    call codes_clone(igribsample,igribclone) ! clone sample before modifying it

    call codes_set(igribclone,'dataDate',date1)
    call codes_set(igribclone,'table2Version',table2Version)
    call codes_set(igribclone,'indicatorOfParameter',indicatorOfParameter)

    call codes_set(igribclone,'stepType',stepType)
    call codes_set(igribclone,'startStep',startStep)
    call codes_set(igribclone,'endStep',endStep)

    call codes_set(igribclone,'decimalPrecision',decimalPrecision)

    call codes_set(igribclone,'values',v)

    call codes_write(igribclone,outfile)
    
    call codes_grib_new_from_file(datafile,igribdata,err)

    if (err==0) then
      call codes_get(igribdata,'values',v2)

      v2=v2*1000.0 ! different units for the output grib

      v=v2-v1 ! accumulation from startStep to endStep

      v1=v2 ! save previous step field

      startStep=startStep+12
      endStep=endStep+12

    endif

  enddo

  call codes_release(igribsample)
  deallocate(v)
  deallocate(v1)
  deallocate(v2)

  call codes_close_file(outfile)

end program sample

#
# (C) Copyright 2005-2016 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 create a new GRIB message from a sample.
#
#

import traceback
import sys

from eccodes import *

INPUT = '../../data/tp_ecmwf.grib'
OUTPUT = 'p_out.grib_samples.grib'
VERBOSE = 1  # verbose error reporting


def example():
    sample_id = codes_grib_new_from_samples("regular_ll_sfc_grib1")
    fin = open(INPUT, 'rb')
    fout = open(OUTPUT, 'wwb')

    keys = {
        'dataDate': 20080104,
        'startStep': 0,
        'endStep': 12,
        'stepType': 'accum',
        'table2Version': 2,
        'indicatorOfParameter': 61,
        'decimalPrecision': 2,
    }

    prev_vals = None
    while 1:
        gid = codes_grib_new_from_file(fin)
        if gid is None:
            break

        curr_vals = codes_get_values(gid)

        if prev_vals is None:
            result = prev_vals = curr_vals
        else:
            try:
                # works with NumPy
                result = curr_vals - prev_vals
            except TypeError:  # but not with array
                result = curr_vals
                for i in range(len(result)):
                    result[i] -= prev_vals[i]

            prev_vals = curr_vals
            keys['startStep'] += 12
            keys['endStep'] += 12

        clone_id = codes_clone(sample_id)

        for key in keys:
            codes_set(clone_id, key, keys[key])

        codes_set_values(clone_id, result * 1000)

        codes_write(clone_id, fout)

        codes_release(gid)

    fin.close()
    fout.close()


def main():
    try:
        example()
    except CodesInternalError as err:
        if VERBOSE:
            traceback.print_exc(file=sys.stderr)
        else:
            sys.stderr.write(err.msg + '\n')

        return 1


if __name__ == "__main__":
    sys.exit(main())