; ----------------------------------------------------------------------
;  Choose best AVP files for date of exposure.
;
pro nsx_choose_best_AVP, IMG, nsxdir, UseAVP
  common nsx
  
  maxnn = 100
  jds = dblarr(maxnn)

; Available files.
  UseAVP = '2017-11-02'
  ;> fill jds with the Julian Date of $nsxdir/cal/AVP.yyyy-mm-dd.info
;misc_delete_file("ncba.temp");
;sprintf(wrd,"ls -1d %scal/AVP.*.info > ncba.temp",nsxdir)
;system(wrd)
;infu = fopen_read("ncba.temp")
;nn=0
;while (fgetline(line,infu)) {
;  ii = cindex(line,"AVP.")
;  substrcpy_terminate(line,ii+4,ii+13,wrd,0); strcat(wrd,"T00:00:00.000")
;  jds[nn] = misc_zulu_to_julian(wrd)
;  ++nn
;  if (nn > maxnn-3) { printf("***error: ncbA: too many AVP.*.info files in '%scal'.\n",nsxdir); exit(1); }
;}
;fclose(infu)
;misc_delete_file("ncba.temp")
  lines = FILE_SEARCH(nsxdir + 'cal/AVP.*.info', count = nn)
  for ii = 0, nn-1 do jds[ii] =  misc_zulu_to_julian(strmid(file_basename(lines[ii], '.info'), 4,10))
  
;first_jd =("2017-11-02T00:00:00.000")
  jd = IMG.jd
;if (jd < first_jd) jd = first_jd
;losep=9.e+20; loii=-1
;for (ii=0; ii<nn; ++ii) {
;  sep = ABS(( jd - jds[ii] ))
;  if (sep < losep) { losep=sep; loii=ii; }
;}
;if (loii > -1) { misc_julian_to_zulu( jds[loii], UseAVP );
;UseAVP[10]='\0'; }
  temp = min( abs(jd - jds), loii)
  UseAVP = strmid(file_basename(lines[loii], '.info'), 4,10)
  print, format='("UT date of exposure is ",A,".")',IMG.utshut
  print, format='("Best AVP file match ",A,".")',UseAVP

end