/**************************************************************************
 * newbucket.hxx -- new bucket routines for better world modeling
 *
 * Written by Curtis L. Olson, started February 1999.
 *
 * Copyright (C) 1999  Curtis L. Olson - http://www.flightgear.org/~curt/
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * $Id$
 **************************************************************************/


#ifdef HAVE_CONFIG_H
#  include <simgear_config.h>
#endif

#include <math.h>

#include <simgear/misc/sg_path.hxx>

#include "newbucket.hxx"


// default constructor
SGBucket::SGBucket() {
}


// constructor for specified location
SGBucket::SGBucket(const double dlon, const double dlat) {
    set_bucket(dlon, dlat);
}

SGBucket::SGBucket(const SGGeod& geod) {
    set_bucket(geod);
}

// create an impossible bucket if false
SGBucket::SGBucket(const bool is_good) {
    set_bucket(0.0, 0.0);
    if ( !is_good ) {
	lon = -1000;
    }
}


// Parse a unique scenery tile index and find the lon, lat, x, and y
SGBucket::SGBucket(const long int bindex) {
    long int index = bindex;
	
    lon = index >> 14;
    index -= lon << 14;
    lon -= 180;

    lat = index >> 6;
    index -= lat << 6;
    lat -= 90;

    y = index >> 3;
    index -= y << 3;

    x = index;
}


// Set the bucket params for the specified lat and lon
void SGBucket::set_bucket( double *lonlat ) {
    set_bucket( lonlat[0], lonlat[1] );
}	


// Set the bucket params for the specified lat and lon
void SGBucket::set_bucket( double dlon, double dlat ) {
    //
    // latitude first
    //
    double span = sg_bucket_span( dlat );
    double diff = dlon - (double)(int)dlon;

    // cout << "diff = " << diff << "  span = " << span << endl;

    /* Calculate the greatest integral longitude less than
     * or equal to the given longitude (floor(dlon)),
     * but attribute coordinates near the east border
     * to the next tile.
     */
    if ( (dlon >= 0) || (fabs(diff) < SG_EPSILON) ) {
	lon = (int)dlon;
    } else {
	lon = (int)dlon - 1;
    }

    // find subdivision or super lon if needed
    if ( span < SG_EPSILON ) {
        /* sg_bucket_span() never returns 0.0
         * or anything near it, so this really
         * should not occur at any time.
         */
	// polar cap
	lon = 0;
	x = 0;
    } else if ( span <= 1.0 ) {
        /* We have more than one tile per degree of
         * longitude, so we need an x offset.
         */
	x = (int)((dlon - lon) / span);
    } else {
        /* We have one or more degrees per tile,
         * so we need to find the base longitude
         * of that tile.
         *
         * First we calculate the integral base longitude
         * (e.g. -85.5 => -86) and then find the greatest
         * multiple of span that is less than or equal to
         * that longitude.
         *
         * That way, the Greenwich Meridian is always
         * a tile border.
         *
         * This gets us into trouble with the polar caps,
         * which have width 360 and thus either span
         * the range from 0 to 360 or from -360 to 0
         * degrees, depending on whether lon is positive
         * or negative!
         *
         * We also get into trouble with the 8 degree tiles
         * north of 88N and south of 88S, because the west-
         * and east-most tiles in that range will cover 184W
         * to 176W and 176E to 184E respectively, with their
         * center at 180E/W!
         */
        lon=(int)floor(floor((lon+SG_EPSILON)/span)*span);
        /* Correct the polar cap issue */
        if ( lon < -180 ) {
            lon = -180;
        }
	x = 0;
    }

    //
    // then latitude
    //
    diff = dlat - (double)(int)dlat;

    /* Again, a modified floor() function (see longitude) */
    if ( (dlat >= 0) || (fabs(diff) < SG_EPSILON) ) {
	lat = (int)dlat;
    } else {
	lat = (int)dlat - 1;
    }
    /* Latitude base and offset are easier, as
     * tiles always are 1/8 degree of latitude wide.
     */
    y = (int)((dlat - lat) * 8);
}


void SGBucket::set_bucket(const SGGeod& geod)
{
    set_bucket(geod.getLongitudeDeg(), geod.getLatitudeDeg());
}

// Build the path name for this bucket
std::string SGBucket::gen_base_path() const {
    // long int index;
    int top_lon, top_lat, main_lon, main_lat;
    char hem, pole;
    char raw_path[256];

    top_lon = lon / 10;
    main_lon = lon;
    if ( (lon < 0) && (top_lon * 10 != lon) ) {
	top_lon -= 1;
    }
    top_lon *= 10;
    if ( top_lon >= 0 ) {
	hem = 'e';
    } else {
	hem = 'w';
	top_lon *= -1;
    }
    if ( main_lon < 0 ) {
	main_lon *= -1;
    }
    
    top_lat = lat / 10;
    main_lat = lat;
    if ( (lat < 0) && (top_lat * 10 != lat) ) {
	top_lat -= 1;
    }
    top_lat *= 10;
    if ( top_lat >= 0 ) {
	pole = 'n';
    } else {
	pole = 's';
	top_lat *= -1;
    }
    if ( main_lat < 0 ) {
	main_lat *= -1;
    }

    sprintf(raw_path, "%c%03d%c%02d/%c%03d%c%02d", 
	    hem, top_lon, pole, top_lat, 
	    hem, main_lon, pole, main_lat);

    SGPath path( raw_path );

    return path.str();
}


// return width of the tile in degrees
double SGBucket::get_width() const {
    if (lon==-180 && (lat==-89 || lat==88) ) {
        /* Normally the tile at 180W in 88N and 89S
         * would cover 184W to 176W and the next
         * on the east side starts at 176W.
         * To correct, make this a special tile
         * from 180W to 176W with 4 degrees width
         * instead of the normal 8 degrees at
         * that latitude.
         */
         return 4.0;
    }
    return sg_bucket_span( get_center_lat() );
}


// return height of the tile in degrees
double SGBucket::get_height() const {
    return SG_BUCKET_SPAN;
}


// return width of the tile in meters
double SGBucket::get_width_m() const {
    double clat = (int)get_center_lat();
    if ( clat > 0 ) {
	clat = (int)clat + 0.5;
    } else {
	clat = (int)clat - 0.5;
    }
    double clat_rad = clat * SGD_DEGREES_TO_RADIANS;
    double cos_lat = cos( clat_rad );
    double local_radius = cos_lat * SG_EQUATORIAL_RADIUS_M;
    double local_perimeter = local_radius * SGD_2PI;
    double degree_width = local_perimeter / 360.0;

    return get_width() * degree_width;
}


// return height of the tile in meters
double SGBucket::get_height_m() const {
    double perimeter = SG_EQUATORIAL_RADIUS_M * SGD_2PI;
    double degree_height = perimeter / 360.0;

    return SG_BUCKET_SPAN * degree_height;
}


// find the bucket which is offset by the specified tile units in the
// X & Y direction.  We need the current lon and lat to resolve
// ambiguities when going from a wider tile to a narrower one above or
// below.  This assumes that we are feeding in
SGBucket sgBucketOffset( double dlon, double dlat, int dx, int dy ) {
    SGBucket result( dlon, dlat );
    double clat = result.get_center_lat() + dy * SG_BUCKET_SPAN;

    // walk dy units in the lat direction
    result.set_bucket( dlon, clat );

    // find the lon span for the new latitude
    double span = sg_bucket_span( clat );

    // walk dx units in the lon direction
    double tmp = dlon + dx * span;
    while ( tmp < -180.0 ) {
	tmp += 360.0;
    }
    while ( tmp >= 180.0 ) {
	tmp -= 360.0;
    }
    result.set_bucket( tmp, clat );

    return result;
}


// calculate the offset between two buckets
void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy ) {

    // Latitude difference
    double c1_lat = b1.get_center_lat();
    double c2_lat = b2.get_center_lat();
    double diff_lat = c2_lat - c1_lat;

#ifdef HAVE_RINT
    *dy = (int)rint( diff_lat / SG_BUCKET_SPAN );
#else
    if ( diff_lat > 0 ) {
	*dy = (int)( diff_lat / SG_BUCKET_SPAN + 0.5 );
    } else {
	*dy = (int)( diff_lat / SG_BUCKET_SPAN - 0.5 );
    }
#endif

    // longitude difference
    double diff_lon=0.0;
    double span=0.0;

    SGBucket tmp_bucket;
    // To handle crossing the bucket size boundary
    //  we need to account for different size buckets.

    if ( sg_bucket_span(c1_lat) <= sg_bucket_span(c2_lat) )
    {
	span = sg_bucket_span(c1_lat);
    } else {
	span = sg_bucket_span(c2_lat);
    }

    diff_lon = b2.get_center_lon() - b1.get_center_lon();

    if (diff_lon <0.0)
    {
       diff_lon -= b1.get_width()*0.5 + b2.get_width()*0.5 - span;
    } 
    else
    {
       diff_lon += b1.get_width()*0.5 + b2.get_width()*0.5 - span;
    }


#ifdef HAVE_RINT
    *dx = (int)rint( diff_lon / span );
#else
    if ( diff_lon > 0 ) {
	*dx = (int)( diff_lon / span + 0.5 );
    } else {
	*dx = (int)( diff_lon / span - 0.5 );
    }
#endif
}


