/****************************************************************************
 *
 * MODULE:       m.measure
 * AUTHOR(S):    Created from d.measure by Glynn Clements, 2010
 *               James Westervelt and Michael Shapiro 
 *                (CERL - original contributors)
 *               Markus Neteler <neteler itc.it>, 
 *               Reinhard Brunzema <r.brunzema@web.de>, 
 *               Bernhard Reiter <bernhard intevation.de>, 
 *               Huidae Cho <grass4u gmail.com>, 
 *               Eric G. Miller <egm2 jps.net>, 
 *               Glynn Clements <glynn gclements.plus.com>, 
 *               Hamish Bowman <hamish_b yahoo.com>, 
 *               Jan-Oliver Wagner <jan intevation.de>
 *               Martin Landa <landa.martin gmail.com>
 * PURPOSE:      Distance and area measurement
 * COPYRIGHT:    (C) 1999-2006, 2010 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 <stdio.h>
#include <stdlib.h>
#include <grass/gis.h>
#include <grass/glocale.h>

int main(int argc, char **argv)
{
    struct GModule *module;
    struct Option *coords, *units;
    struct Flag *shell;

    double *x, *y;
    double length, area, f, sq_f;
    int i, npoints;
    const char *units_name, *sq_units_name;

    /* Initialize the GIS calls */
    G_gisinit(argv[0]);

    module = G_define_module();
    module->description = _("Measures the lengths and areas of features.");
    G_add_keyword(_("miscellaneous"));
    G_add_keyword(_("measurement"));
    G_add_keyword(_("distance"));
    G_add_keyword(_("area"));

    coords = G_define_standard_option(G_OPT_M_COORDS);
    coords->required = YES;
    coords->multiple = YES;

    units = G_define_standard_option(G_OPT_M_UNITS);
    units->label = _("Units");
    units->description = _("Default: location map units");
    
    shell = G_define_flag();
    shell->key = 'g';
    shell->description = _("Shell script style");
    
    if (G_parser(argc, argv))
	exit(EXIT_FAILURE);

    npoints = 0;
    for (i = 0; coords->answers[i]; i += 2)
	npoints++;
    x = G_malloc(npoints * sizeof(double));
    y = G_malloc(npoints * sizeof(double));

    for (i = 0; i < npoints; i++)
    {
	x[i] = atof(coords->answers[2*i+0]);
	y[i] = atof(coords->answers[2*i+1]);
    }

    /* determine units */
    if (G_projection() == PROJECTION_LL && !units->answer) {
	units_name    = G_get_units_name(U_METERS, 1, 0);
	sq_units_name = G_get_units_name(U_METERS, 1, 1);
    }
    else {
	units_name    = G_get_units_name(G_units(units->answer), 1, 0);
	sq_units_name = G_get_units_name(G_units(units->answer), 1, 1);
    }
    f    = G_meters_to_units_factor(G_units(units->answer));
    sq_f = G_meters_to_units_factor_sq(G_units(units->answer));
    
    G_debug(1, "using '%s (%f) %s (%f)'",
	    units_name, f, sq_units_name, sq_f);
    
    G_begin_distance_calculations();
    length = 0;
    for (i = 1; i < npoints; i++)
	length += G_distance(x[i-1], y[i-1], x[i], y[i]);

    if (shell->answer) {
	printf("units=%s,%s\n", units_name, sq_units_name);
	/* length */
	printf("length=%.6f\n", f * length);
    }
    else {
	printf("%-8s %10.6f %s\n", _("Length:"), f * length, units_name);
	       
    }
    
    if (npoints > 3) {
	G_begin_polygon_area_calculations();
	area = G_area_of_polygon(x, y, npoints);
	if (shell->answer) {
	    printf("area=%.6f\n", sq_f * area);
	}
	else {
	    printf("%-8s %10.6f %s\n", _("Area:"), sq_f * area, sq_units_name);
	}
    }

    exit(EXIT_SUCCESS);
}