/*!
  \file gis/proj3.c

  \brief GIS Library - Projection support
  
  (C) 2001-2009 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.
  
  \author Original author CERL
 */

#include <string.h>
#include <grass/gis.h>
#include <grass/glocale.h>

static const char *lookup_proj(const char *);
static const char *lookup_units(const char *);
static int equal(const char *, const char *);
static int lower(char);

static int initialized;
static struct Key_Value *proj_info, *proj_units;

static void init(void)
{
    if (G_is_initialized(&initialized))
	return;

    proj_info = G_get_projinfo();
    proj_units = G_get_projunits();

    G_initialize_done(&initialized);
}

/*!
 * \brief Get database units
 *
 * Returns a string describing the database grid units. It returns a
 * plural form (eg. feet) if <i>plural</i> is true. Otherwise it
 * returns a singular form (eg. foot).
 *
 * \param plural plural form if true
 *
 * \return units name
 */
const char *G_database_unit_name(int plural)
{
    int n;
    const char *name;

    switch (n = G_projection()) {
    case PROJECTION_XY:
    case PROJECTION_UTM:
    case PROJECTION_LL:
    case PROJECTION_SP:
	return G__unit_name(G__projection_units(n), plural);
    }

    name = lookup_units(plural ? "units" : "unit");
    if (!name)
	return plural ? "units" : "unit";

    return name;
}


/*!
 * \brief Query cartographic projection
 *
 * Returns a pointer to a string which is a printable name for
 * projection code <i>proj</i> (as returned by G_projection). Returns
 * NULL if <i>proj</i> is not a valid projection.
 *
 * \return projection name
 */
const char *G_database_projection_name(void)
{
    int n;
    const char *name;

    switch (n = G_projection()) {
    case PROJECTION_XY:
    case PROJECTION_UTM:
    case PROJECTION_LL:
    case PROJECTION_SP:
	return G__projection_name(n);
    }

    name = lookup_proj("name");
    if (!name)
	return _("Unknown projection");

    return name;
}

/*!
 * \brief Conversion to meters
 *
 * Returns a factor which converts the grid unit to meters (by
 * multiplication). If the database is not metric (eg. imagery) then
 * 0.0 is returned.
 *
 * \return value
 */
double G_database_units_to_meters_factor(void)
{
    const char *unit;
    const char *buf;
    double factor;
    int n;

    static const struct
    {
	char *unit;
	double factor;
    } table[] = {
	{"unit",  1.0},
	{"meter", 1.0},
	{"foot", .3048},
	{"inch", .0254},
	{NULL, 0.0}
    };

    factor = 0.0;
    buf = lookup_units("meters");
    if (buf)
	sscanf(buf, "%lf", &factor);
    if (factor <= 0.0) {
	unit = G_database_unit_name(0);
	for (n = 0; table[n].unit; n++)
	    if (equal(unit, table[n].unit)) {
		factor = table[n].factor;
		break;
	    }
    }
    return factor;
}

/*!
 * \brief Get datum name for database
 *
 * Returns a pointer to the name of the map datum of the current
 * database. If there is no map datum explicitely associated with the
 * acutal database, the standard map datum WGS84 is returned, on error
 * a NULL pointer is returned.
 *
 * \return datum name
 */
const char *G_database_datum_name(void)
{
    const char *name;
    char buf[256], params[256];
    int datumstatus;

    name = lookup_proj("datum");
    if (name)
	return name;
    else if (!proj_info)
	return NULL;
    else
	datumstatus = G_get_datumparams_from_projinfo(proj_info, buf, params);

    if (datumstatus == 2)
	return G_store(params);
    else
	return NULL;
}

/*!
  \brief Get ellipsoid name of current database
  
  \return pointer to valid name if ok
  \return NULL on error
*/
const char *G_database_ellipse_name(void)
{
    const char *name;

    name = lookup_proj("ellps");
    if (!name) {
	char buf[256];
	double a, es;

	G_get_ellipsoid_parameters(&a, &es);
	sprintf(buf, "a=%.16g es=%.16g", a, es);
	name = G_store(buf);
    }

    /* strcpy (name, "Unknown ellipsoid"); */
    return name;
}

static const char *lookup_proj(const char *key)
{
    init();
    return G_find_key_value(key, proj_info);
}

static const char *lookup_units(const char *key)
{
    init();
    return G_find_key_value(key, proj_units);
}

static int equal(const char *a, const char *b)
{
    if (a == NULL || b == NULL)
	return a == b;
    while (*a && *b)
	if (lower(*a++) != lower(*b++))
	    return 0;
    if (*a || *b)
	return 0;
    return 1;
}

static int lower(char c)
{
    if (c >= 'A' && c <= 'Z')
	c += 'a' - 'A';
    return c;
}