#!/usr/bin/env python
############################################################################
#
# MODULE:       i.in.probav
# AUTHOR(S):    Jonas Strobel, intern at mundialis and terrestris, Bonn
# PURPOSE:      i.in.probav
# COPYRIGHT:    (C) 2017 by stjo, and the GRASS Development Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
############################################################################

#%module
#% description: Imports PROBA-V NDVI data in netCDF format into a raster map with real NDVI data range.
#% keyword: imagery
#% keyword: import
#% keyword: NDVI
#% keyword: PROBA-V
#%end
#%option G_OPT_F_INPUT
#% description: Name of input PROBA-V NDVI .nc file
#%end
#%option G_OPT_R_OUTPUT
#%end
#%option
#% key: scale
#% type: double
#% required: no
#% multiple: no
#% answer: 0.004
#% key_desc: float
#% description: Scale factor for input
#%end
#%option
#% key: shift
#% type: double
#% required: no
#% multiple: no
#% answer: -0.08
#% key_desc: float
#% label: Shift factor for input
#% description: Offset factor for input
#%end
#%option
#% key: memory
#% type: double
#% required: no
#% multiple: no
#% options: 0-2047
#% answer: 300
#% key_desc: integer
#% description: Maximum memory to be used in MB
#%end

import sys
import os
import atexit
import grass.script as gscript
from grass.exceptions import CalledModuleError

def cleanup():
    pass


def main():

    global tmpfile
    infile = options['input']
    out = options['output']
    scale = options['scale']
    offset = options['shift']
    mem = options['memory']


    pid = os.getpid()
    tmpname = str(pid) + 'i.in.probav'
    tmpfile = gscript.tempfile()

    if not gscript.overwrite() and gscript.find_file(out)['file']:
        gscript.fatal(("<%s> already exists. Aborting.") % out)

    # Are we in LatLong location?
    s = gscript.read_command("g.proj", flags='j')
    kv = gscript.parse_key_val(s)
    if kv['+proj'] != 'longlat':
        gscript.fatal(("This module only operates in LatLong locations"))


    try:
        gscript.message('Importing raster map <' + out + '>...')
        gscript.run_command('r.in.gdal', input=infile, output=tmpname, memory=mem, quiet=True)
    except CalledModuleError:
        gscript.fatal(("An error occurred. Stop."))

    # What is the relation between the digital number and the real NDVI ?
    # Real NDVI =coefficient a * Digital Number + coefficient b
    #           = a * DN +b
    #
    # Coefficient a = scale
    # Coefficient b = offset

    # create temporary region
    gscript.use_temp_region()
    gscript.run_command('g.region', raster=tmpname, quiet=True)
    gscript.message("Remapping digital numbers to NDVI...")

    # do the mapcalc
    gscript.mapcalc("${out} = ${a} * ${tmpname} + ${b}", out=out, a=scale, tmpname=tmpname, b=offset)

    # remove original input
    gscript.run_command('g.remove', type='raster', name=tmpname, quiet=True, flags='f')
    
    # set color table to ndvi
    gscript.run_command('r.colors', map=out, color='ndvi')

    gscript.message(("Done: generated map <%s>") % out)

    return 0

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