// Bibliotheque OpenCoordinate : fonctions coordonnees geographiques

#include "oc.h"

#include <stdio.h>
#include <math.h>


double oc_distance_between(struct point a, struct point b) {
  // retourne la distance entre les 2 points en metres
  double R = 6378137; // metres
  double d_lat = (b.lat-a.lat)/180*M_PI;
  double d_lon = (b.lon-a.lon)/180*M_PI;
  double alpha = sin(d_lat/2) * sin(d_lat/2) +
    cos(a.lat/180*M_PI) * cos(b.lat/180*M_PI) *
    sin(d_lon/2) * sin(d_lon/2);
  double c = 2 * atan2(sqrt(alpha), sqrt(1-alpha));
  return R * c;
}


struct point_relatif oc_convert(struct point o, struct point a) {
  //convert transforme des coordonnes WGS84 en metres par rapport au referentiel r
  struct point proj_x, proj_y;
  struct point_relatif pr;
  proj_x.lat=a.lat;
  proj_x.lon=o.lon;
  proj_y.lat=o.lat;
  proj_y.lon=a.lon;
  pr.x=oc_distance_between(proj_y,o);
  pr.y=oc_distance_between(proj_x,o);
  pr.z=0;
  if (proj_y.lon > o.lon) pr.x=-pr.x;
  if (proj_x.lat > o.lat) pr.y=-pr.y;
  return pr;
}


/*
  function unconvert(x,y) {
  if (origine==null) return null;
  else {
  var R = 6378137; // metres
  var lat1 = origine.lat()/180*Math.PI;
  var lon1 = origine.lng()/180*Math.PI;
  var d = Math.sqrt(x*x + y*y);
  var brng = Math.acos( y / d);
  var lat2 = Math.asin( Math.sin(lat1)*Math.cos(d/R) +
  Math.cos(lat1)*Math.sin(d/R)*Math.cos(brng) );
  var lon2 = lon1 +
  Math.atan2(Math.sin(brng)*Math.sin(d/R)*Math.cos(lat1),
  Math.cos(d/R)-Math.sin(lat1)*Math.sin(lat2));
  return new google.maps.LatLng(lat2*180/Math.PI, lon2*180/Math.PI);
  }
  }
*/


double oc_cap(struct point o, struct point a) {
  struct point_relatif pr=oc_convert(a, o);
  double alpha;
  printf("cap x=%f et y=%f\n",pr.x, pr.y);
  if (pr.x==0)
    if (pr.y>=0) return 360.0;
    else return 180.0;
  else {
    alpha=atan(pr.y/pr.x) * 180 / M_PI;
    printf("%f\n",alpha);
    if (pr.x>0)
      return ((450 - alpha)/360 - round((450 - alpha)/360))*360;
    else {
      //alpha=atan(-pr.y/pr.x) * 180 / PI;
      //printf("%f\n",alpha);
      return 270-alpha;
    }
  }
}