// boxscan.c
// Colin Borys, 26 Sept 2003
//
// This program computes the parameters for the UIP command "BOX_SCAN".
// It takes as input the desired map size and spacing, checks 
// constraints, and outputs the most appropriate parameters.
//
// to compile:
// gcc -o boxscan boxscan.c -lm
#include <math.h>
#include <stdio.h>
#include <stdlib.h>



int main(int argc, char *argv[]) {
  float A;      // size of X dimension of scan in arcsec
  float B;      // size of Y dimension of scan in arcsec
  float Bprime; // size of Y dimension of scan in arcsec after applying
                // constraints

  float d;        // size of spacing
  float dprime;   // size of spacing after applying constraints

  float z,zprime; // width of the "diamond"


  float l;         // linear distance telescope must travel to complete scan
  int Nx,Ny;       // number of "diamonds" on each axis
  float rate=20.0; // scan rate (arcsec/sec)
  float scantime;  // time to complete scan (minutes)
  float sensitivity;

  int i;           // loop variable.
  if (argc <4) {
    fprintf(stderr,"Usage:\n");
    fprintf(stderr,"%s A B d [v]\n",argv[0]);
    exit(0);
  }
  if (!sscanf(argv[1], "%f",&A)) {
    fprintf(stderr,"Bad value for A: %s\n",argv[1]);
    exit(0);
  }
  if (!sscanf(argv[2], "%f",&B)) {
    fprintf(stderr,"Bad value for B: %s\n",argv[2]);
    exit(0);
  }
  if (!sscanf(argv[3], "%f",&d)) {
    fprintf(stderr,"Bad value for d: %s\n",argv[3]);
    exit(0);
  }
  // rate is an optional entry..default is 20 arcs/sec
  if (argc==5)
    if (!sscanf(argv[4], "%f",&rate)) {
      fprintf(stderr,"Bad value for scan rate: %s\n",argv[3]);
      exit(0);
    }
  
  z=sqrt(2)*d;  // width of diamond
  
  Nx=rint(A/z);         // number of diamonds in X direction
  zprime=A/(float)Nx;   // recompute width based on integer value
  dprime=zprime/sqrt(2);// recompute grid spacing
  
  Ny=rint(B/zprime);    // compute # of diamonds in Y direction

  if (Nx%2 == Ny%2) Ny--; // one must be odd, the other even....

  // Nx and Ny must not have a common factor between them
  // Therefore test for the first few odd factors.
  // (There will be no even factors since we've forced one
  // to be odd).  
  for (i=3;i<=11;i+=2)
    if ((Nx%i == 0)  && (Ny%i == 0)) Ny+=2;
 
  // we could test for higher odd factors but in practice the scans
  // will not have that many diamonds on a side.

  Bprime=zprime*Ny;     // compute actual size of Y direction

  l=4*Nx*Ny*dprime;    // length of scan (arcsec)

  scantime= l/(60.0*rate); // scan time
  sensitivity = 1000/sqrt(60.0*scantime/(A*B/(155.2*58.2)));

  // print out the UIP command and the required integration time
  printf("BOX_SCAN %8.3f %8.3f %4.1f 45 : %10.2f minutes\n",A,Bprime,rate,scantime);

  if (scantime>15.0) printf("# WARNING: scantime exceeds 15 minutes\n");
  if (rate>40.0)     printf("# WARNING: scan rate exceeds 40 arcsec/sec\n");
  if (dprime>40.0)   printf("# WARNING: grid spacing exceeds 40 arcsec\n");

  printf("# INFO: grid spacing is %8.3f\n",dprime);
  printf("# INFO: Number of diamonds is: [%4i X %4i]\n",Nx,Ny);
  printf("# INFO: Sensitivity estimate: %10.2f mJy/beam \n",sensitivity);
  return 1;

}