#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "mucal.h"
#include "panel.h"

/* ********************************************** */

int detector_ovlap(
   float dis,
   float Rdet,
   float Rfac,
   float *overlap_frac)
{

   float pi, x, x2, area1, area2;

   pi = 3.14159;
/*   
   printf("dis %4.2f Rdet %4.1f Rfac %4.1f ", dis, Rdet, Rfac);
*/
   if (fabs(dis) <= (fabs(Rdet) - fabs(Rfac))) {*overlap_frac = 1.0; /* printf("overlap: 1.0\n");*/  return(0);}
   if (fabs(dis) >= (fabs(Rdet) + fabs(Rfac))) {*overlap_frac = 0.0; /* printf("overlap: 0.0\n");*/ return(0);}

   x2 = Rfac*Rfac - (Rdet*Rdet - dis*dis - Rfac*Rfac) * (Rdet*Rdet - dis*dis - Rfac*Rfac) / (4.0 * dis*dis);
   
   x = sqrt(x2);

   area1 = Rfac*Rfac * asin(x / Rfac) - x * sqrt(Rfac*Rfac - x*x);
   area2 = Rdet*Rdet * asin(x / Rdet) - x * sqrt(Rdet*Rdet - x*x);

   if (dis*dis < (Rdet*Rdet - Rfac*Rfac)) 
      *overlap_frac = pi * Rfac * Rfac - area1 + area2;
   else					  
      *overlap_frac = area1 + area2;

   *overlap_frac /=  pi * Rfac * Rfac;
/*
   printf(
   "x2 %5.2f x %4.3f area1 %4.2f area2 %4.2f asin(x/Rf) %5.3f asin(x/Rd) %5.3f ovlp_frac %4.3f\n", 
      x2, x, area1, area2, asin(x / Rfac), asin(x / Rdet), *overlap_frac);
*/ 
   return(0);
}