/***************************************************************
 *
 * MODULE:       v.parallel
 * 
 * AUTHOR(S):    Radim Blazek
 *               
 * PURPOSE:      Create parallel lines
 *               
 * COPYRIGHT:    (C) 2001 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.
 *
 **************************************************************/
#include <stdlib.h> 
#include <math.h>
#include <grass/gis.h>
#include <grass/Vect.h>
#include <grass/glocale.h>

int 
main (int argc, char *argv[])
{
    struct GModule *module;
    struct Option *in_opt, *out_opt, *distance_opt, *layer_opt;
    struct Map_info In, Out;
    struct line_pnts *Points, *Points2;
    struct line_cats *Cats;
    int    layer;
    int    line, nlines;
    double distance, tolerance;

    G_gisinit(argv[0]);

    module = G_define_module();
    module->keywords = _("vector, geometry");
    module->description = "Create parallel line to input lines.";

    in_opt = G_define_standard_option(G_OPT_V_INPUT);
    out_opt = G_define_standard_option(G_OPT_V_OUTPUT);
    /* layer_opt = G_define_standard_option(G_OPT_V_FIELD); */
    
    distance_opt = G_define_option();
    distance_opt->key = "distance";
    distance_opt->type =  TYPE_DOUBLE;
    distance_opt->required = YES;
    distance_opt->multiple = NO;
    distance_opt->description = "Offset in map units, positive for right side, "
	                        "negative for left side.";

    if (G_parser (argc, argv)) exit(-1); 

    /* layer = atoi ( layer_opt->answer ); */
    distance = atof ( distance_opt->answer );
    tolerance = distance/10;

    Vect_set_open_level (2); 
    Vect_open_old (&In, in_opt->answer, ""); 
    Vect_open_new (&Out, out_opt->answer, 0);
    Vect_copy_head_data (&In, &Out);
    Vect_hist_copy (&In, &Out);
    Vect_hist_command ( &Out );
    
    Points = Vect_new_line_struct ();
    Points2 = Vect_new_line_struct ();
    Cats = Vect_new_cats_struct ();

    nlines = Vect_get_num_lines ( &In );

    for ( line = 1; line <= nlines; line++ ) {
	int ltype, cat;
	
	G_percent ( line, nlines, 1 );

	ltype = Vect_read_line ( &In, Points, Cats, line);

	if ( ltype & GV_LINES ) {
	    Vect_line_parallel ( Points, distance, tolerance, 1, Points2 );
	    Vect_write_line ( &Out, ltype, Points2, Cats );
	} else {
	    Vect_write_line ( &Out, ltype, Points, Cats );
	}
    }
    
    Vect_close (&In);
    Vect_build (&Out, stderr);
    Vect_close (&Out);

    exit(0) ;
}