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/* ** Copyright UCAR (c) 1990 - 2016                                         */
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/* ** Boulder, Colorado, USA                                                 */
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#include <toolsa/toolsa_macros.h>
#include <rapmath/trig.h>

/*----------------------------------------------------------------*/
/*
 * Convert from speed, dir (clockwise from true north, i.e. radar coords) 
 * to u, v.
 */ 
void
dir_speed_2_uv(float speed, float dir, float *u, float *v)
/* speed - in km/h, m/s, whatever
 * dir   - in degrees
 * u, v  - same units as speed
 */
{
    double d, s, uu, vv;
    double sind, cosd;

    /*
     * Convert direction from radar to polar coordinates.
     */
    s = (double)speed;
    d = (double)(90.0 - dir);

    /*
     * Put in range [0.0, 360)
     */
    while (d < 0.0)
        d += 360.0;

    /*
     * Convert degrees to radians.
     * 1 degree = (pi/180) radians
     */
    d *= DEG_TO_RAD;

    /*
     * This is essentially a conversion from polar coordinates
     * to cartesian coordinates
     */
    
    rap_sincos(d, &sind, &cosd);
    vv = s * sind;
    uu = s * cosd;

    *u = (float)uu;
    *v = (float)vv;
}

/*----------------------------------------------------------------*/
/*
 * Convert from speed, dir (counter-clockwise from true north, 
 *                          i.e. wind convention)
 * to u, v.
 */
void
wind_dir_speed_2_uv(float speed, float dir, float *u, float *v)
/* speed - in km/h, m/s, whatever
 * dir   - in degrees
 * u, v  - same units as speed
 */
{
  /*
   * Convert the direction to the convention of "from wind to origin"
   */
   dir += 180.0;
   if ( dir > 360.0 ) {
      dir -= 360.0;
   }

   dir_speed_2_uv( speed, dir, u, v );
}