#!/usr/bin/env python
# -*- coding: utf-8 -*-
############################################################################
#
# MODULE:       v.explode
# AUTHOR(S):    Alexander Muriy
#               (Institute of Environmental Geoscience, Moscow, Russia)  
#               e-mail: amuriy AT gmail DOT com 
#
# PURPOSE:      "Explode" polylines, splitting them to separate lines
#
# COPYRIGHT:    (C) 2016 Alexander Muriy / 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: "Explode" polylines, splitting them to separate lines (uses v.split + v.category)
#%  keyword: display
#%  keyword: graphics
#%  keyword: vector
#%  keyword: symbology
#%End
#%Option
#%  key: input
#%  type: string
#%  required: yes
#%  multiple: no
#%  key_desc: name
#%  description: Name of input vector map
#%  gisprompt: old,vector,vector
#%End
#%Option
#%  key: output
#%  type: string
#%  required: no
#%  multiple: no
#%  key_desc: name
#%  description: Name of output vector map 
#%  gisprompt: new,vector,vector
#%End
############################################################################

import os
import atexit

try:
    import grass.script as grass
except:
    try:
        from grass.script import core as grass
    except:
        if not os.environ.has_key("GISBASE"):
            print("You must be in GRASS GIS to run this program.")
            sys.exit(1)
        

def cleanup():
    nuldev = file(os.devnull, 'w')
    grass.run_command('g.remove', type_ = 'vect', pattern = 'v_explode*', flags = 'f',
                      quiet = True, stderr = nuldev)

def main():
    inmap = options['input']
    outmap = options['output']

    global nuldev
    nuldev = None

    # check if input file exists
    if not grass.find_file(inmap, element = 'vector')['file']:
        grass.fatal(_("<%s> does not exist.") % inmap)

    
    out_split = 'v_explode' + '_' + 'split'
    grass.run_command('v.split', input_ = inmap, vertices = 2, 
                          out = out_split, quiet = True, stderr = nuldev)
    out_catdel = 'v_explode' + '_' + 'catdel'
    grass.run_command('v.category', input_ = out_split, opt = 'del', 
                      output = out_catdel, quiet = True, stderr = nuldev)
    grass.run_command('v.category', input_ = out_catdel, opt = 'add', 
                      output = outmap, quiet = True, stderr = nuldev)
    

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