#!/usr/bin/env python
#
############################################################################
#
# MODULE:      r.out.ntv2
# AUTHOR(S):   Maciej Sieczka
# PURPOSE:     Export NTv2 datum transformation grid.
# COPYRIGHT:   (C) 2016 by the GRASS Development Team
#
#              This program is free software under the GNU General Public
#              License (>=v2). Read the file COPYING that comes with GRASS
#              for details.
#
#############################################################################

#%Module
#% description: Exports NTv2 datum transformation grid
#%End

#%option
#% key: latshift
#% type: string
#% gisprompt: old,cell,raster
#% description: Input raster map of lattitude datum shift values
#% required : yes
#%end

#%option
#% key: lonshift
#% type: string
#% gisprompt: old,cell,raster
#% description: Input raster map of longitude datum shift values
#% required : yes
#%end

#%option
#% key: output
#% type: string
#% description: Output NTv2 datum transformation grid file
#% gisprompt: new_file,file,output
#% required: yes
#%end

#%option
#% key: systemt
#% type: string
#% description: Transformation grid's destination coordinate system name
#% required : no
#% answer: WGS84
#%end

#%option
#% key: majort
#% type: string
#% description: Major ellipsoid axis of the transformation grid's destination coordinate system
#% required : no
#% answer: 6378137
#%end

#%option
#% key: minort
#% type: string
#% description: Minor ellipsoid axis of the transformation grid's destination coordinate system
#% required : no
#% answer: 6356752.314245
#%end

#%option
#% key: systemf
#% type: string
#% description: Transformation grid's input coordinate system name
#% required : no
#% answer: UNKNOWN
#%end

#%option
#% key: majorf
#% type: string
#% description: Major ellipsoid axis of the transformation grid's input coordinate system
#% required : no
#% answer: UNKNOWN
#%end

#%option
#% key: minorf
#% type: string
#% description: Minor ellipsoid axis of the transformation grid's input coordinate system
#% required : no
#% answer: UNKNOWN
#%end

'''
SYSTEM_F, SYSTEM_T, MAJOR_F, MINOR_F, MAJOR_T, MINOR_T are not used for
anything in GDAL or PROJ.4. They will always assume the *_T system is WGS84 and
the *_F system's parameters are simply ignored. It makes sense setting these
for documentation's sake only.

More about NTv2 format on https://github.com/Esri/ntv2-file-routines.
'''

import atexit, sys, uuid, time
from grass.script import core as grass

tmp_group = str(uuid.uuid4())

def cleanup():
  grass.run_command("g.remove",
                    type = "group",
                    name = tmp_group,
                    flags = "f",
                    quiet = True)

def main():
  grass.run_command("i.group",
                    input = (options["latshift"], options["lonshift"]),
                    group = tmp_group,
                    quiet = True)

  grass.run_command("r.out.gdal",
                    input = tmp_group,
                    output = options["output"],
                    format = "NTv2",
                    type = "Float32",
                    quiet = True,
                    metaopt = ("CREATED="+time.strftime("%Y%m%d"),
                              "GS_TYPE=SECONDS",
                              "SYSTEM_T="+options["systemt"],
                              "MAJOR_T="+options["majort"],
                              "MINOR_T="+options["minort"],
                              "SYSTEM_F="+options["systemf"],
                              "MAJOR_F="+options["majorf"],
                              "MINOR_F="+options["minorf"],
                              "PARENT=NONE",
                              "SUB_NAME=NONE",
                              "UPDATED="+time.strftime("%H%M%S"),
                              "VERSION=NTv2.0"))

if __name__ == "__main__":
  options, flags = grass.parser()
  atexit.register(cleanup)
  sys.exit(main())