#!/usr/bin/env python

#import of SRTM hgt files into GRASS
# written by Markus Neteler 11/2003 neteler AT itc it
#
# COPYRIGHT:	(C) 2004, 2006 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.
#
# Dec 2004: merged with srtm_generate_hdr.sh (M. Neteler)
#           corrections and refinement (W. Kyngesburye)
# Aug 2004: modified to accept files from other directories
#           (by H. Bowman)
# June 2005: added flag to read in US 1-arcsec tiles (H. Bowman)
# April 2006: links updated from ftp://e0dps01u.ecs.nasa.gov/srtm/             
#             to current links below
# October 2008: Converted to Python by Glynn Clements
#########################
#Derived from:
# ftp://e0srp01u.ecs.nasa.gov/srtm/version1/Documentation/Notes_for_ARCInfo_users.txt
#     (note: document was updated silently end of 2003)
#
# ftp://e0srp01u.ecs.nasa.gov/srtm/version1/Documentation/SRTM_Topo.txt
#  "3.0 Data Formats
#  [...]
#  To be more exact, these coordinates refer to the geometric center of 
#  the lower left pixel, which in the case of SRTM-1 data will be about
#  30 meters in extent."
#
#- SRTM 90 Tiles are 1 degree by 1 degree
#- SRTM filename coordinates are said to be the *center* of the LL pixel.
#       N51E10 -> lower left cell center
#
#- BIL uses *center* of the UL (!) pixel:
#      http://downloads.esri.com/support/whitepapers/other_/eximgav.pdf
#  
#- GDAL uses *corners* of pixels for its coordinates.
#
# NOTE: Even, if small difference: SRTM is referenced to EGM96, not WGS84 ellps
# http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm96/intpt.html
#
#########################

#%Module
#%  description: Import SRTM HGT files into GRASS
#%  keywords: raster, import
#%End
#%option
#% key: input
#% gisprompt: old_file,file,input
#% type: string
#% description: SRTM input tile (file without .hgt.zip extension)
#% required : yes
#%end
#%option
#% key: output
#% gisprompt: new,cell,raster
#% type: string
#% description: Output raster map (default: input tile)
#% required : no
#%end
#%flag
#%  key: 1
#%  description: Input is a 1-arcsec tile (default: 3-arcsec)
#%end

tmpl1sec = """BYTEORDER M
LAYOUT BIL
NROWS 3601
NCOLS 3601
NBANDS 1
NBITS 16
BANDROWBYTES 7202
TOTALROWBYTES 7202
BANDGAPBYTES 0
PIXELTYPE SIGNEDINT
NODATA -32768
ULXMAP %s
ULYMAP %s
XDIM 0.000277777777777778
YDIM 0.000277777777777778
"""

tmpl3sec = """BYTEORDER M
LAYOUT BIL
NROWS 1201
NCOLS 1201
NBANDS 1
NBITS 16
BANDROWBYTES 2402
TOTALROWBYTES 2402
BANDGAPBYTES 0
PIXELTYPE SIGNEDINT
NODATA -32768
ULXMAP %s
ULYMAP %s
XDIM 0.000833333333333
YDIM 0.000833333333333
"""

proj = ''.join([
    'GEOGCS[',
    '"wgs84",',
    'DATUM["WGS_1984",SPHEROID["wgs84",6378137,298.257223563],TOWGS84[0.000000,0.000000,0.000000]],',
    'PRIMEM["Greenwich",0],',
    'UNIT["degree",0.0174532925199433]',
    ']'])

import sys
import os
import shutil
import atexit
from grass.script import core, raster as grass

def cleanup():
    if not in_temp:
	return
    for ext in ['.bil', '.hdr', '.prj', '.hgt.zip']:
	grass.try_remove(tile + ext)
    os.chdir('..')
    grass.try_rmdir(tmpdir)

def main():
    global tile, tmpdir, in_temp

    in_temp = False

    input = options['input']
    output = options['output']
    one = flags['1']

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

    # use these from now on:
    infile = input
    while infile[-4:].lower() in ['.hgt', '.zip']:
	infile = infile[:-4]
    (fdir, tile) = os.path.split(infile)

    if not output:
	tileout = tile
    else:
	tileout = output

    zipfile = infile + ".hgt.zip"
    hgtfile = infile + ".hgt"
    if os.path.isfile(zipfile):
        #### check if we have unzip
	if not grass.find_program('unzip'):
	    grass.fatal('The "unzip" program is required, please install it first')

	# really a ZIP file?
	# make it quiet in a safe way (just in case -qq isn't portable)
	tenv = os.environ.copy()
	tenv['UNZIP'] = '-qq'
	if grass.call(['unzip', '-t', zipfile], env = tenv) != 0:
	    grass.fatal("'%s' does not appear to be a valid zip file." % zipfile)

	is_zip = True
    elif os.path.isfile(hgtfile):
	# try and see if it's already unzipped
	is_zip = False
    else:
	grass.fatal("File '%s' or '%s' not found" % (zipfile, hgtfile))

    #make a temporary directory
    tmpdir = grass.tempfile()
    grass.try_remove(tmpdir)
    os.mkdir(tmpdir)

    if is_zip:
	shutil.copyfile(zipfile, os.path.join(tmpdir, zipfile))
    else:
	shutil.copyfile(hgtfile, os.path.join(tmpdir, hgtfile))

    #change to temporary directory
    os.chdir(tmpdir)
    in_temp = True

    zipfile = tile + ".hgt.zip"
    hgtfile = tile + ".hgt"
    bilfile = tile + ".bil"

    if is_zip:
        #unzip & rename data file:
	grass.message("Extracting '%s'..." % infile)
	if grass.call(['unzip', zipfile], env = tenv) != 0:
	    grass.fatal("Unable to unzip file.")

    grass.message("Converting input file to BIL...")
    os.rename(hgtfile, bilfile)

    north = tile[0]
    ll_latitude  = int(tile[1:3])
    east = tile[3]
    ll_longitude = int(tile[4:7])

    # are we on the southern hemisphere? If yes, make LATITUDE negative.
    if north == "S":
	ll_latitude *= -1

    # are we west of Greenwich? If yes, make LONGITUDE negative.
    if east == "W":
	ll_longitude *= -1

    # Calculate Upper Left from Lower Left
    ulxmap = "%.1f" % ll_longitude
    # SRTM90 tile size is 1 deg:
    ulymap = "%.1f" % (ll_latitude + 1)

    if not one:
	tmpl = tmpl3sec
    else:
	grass.message("Attempting to import 1-arcsec data.")
	tmpl = tmpl1sec

    header = tmpl % (ulxmap, ulymap)
    hdrfile = tile + '.hdr'
    outf = file(hdrfile, 'w')
    outf.write(header)
    outf.close()

    #create prj file: To be precise, we would need EGS96! But who really cares...
    prjfile = tile + '.prj'
    outf = file(prjfile, 'w')
    outf.write(proj)
    outf.close()

    if grass.run_command('r.in.gdal', input = bilfile, out = tileout) != 0:
	grass.fatal("Unable to import data")

    # nice color table
    grass.run_command('r.colors', map = tileout, color = 'srtm')

    # write cmd history:
    grass.raster_history(tileout)

    grass.message("Done: generated map " + tileout)
    grass.message("(Note: Holes in the data can be closed with 'r.fillnulls' using splines)")

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