#!/usr/bin/perl

# hans muller, sax/sdc/sron 12 05 2000

# Script to get filename of appropriate "nearest" SAX/WFC response 
# matrix for a given date and [x,y] detector pixel 

# Written not that elegantly, but somehow works alright

# Script explains itself, when called without parameters:

if ( $ARGV[0] == "" && $ARGV[1] == 0 && $ARGV[2] == 0 && $ARGV[3] == 0 ) 
{
  print " ********* script which_rmf.pl ******** \n";
  print " * Find the nearest WFC responsematrix* \n";
  print " * for a given wfc, date and pixel    * \n";
  print " *                                    * \n";
  print " * Parameters:                        * \n";
  print " * 1. mod. julian daynumber           * \n";
  print " * 2. wfc  (w1 or w2)                 * \n";
  print " * 3. xpix                            * \n";
  print " * 4. ypix                            * \n";
  print " *                                    * \n";
  print " * Examples:                          * \n";
  print " * >> which_rmf 51550 w1 100 375      * \n";
  print " * >> which_rmf 51550.3 w1 36.5 405.5 * \n";
  print " ************************************** \n";

}
else
{

# initialise input variables
#---------------------------
$mjd     = $ARGV[0]; 
$wfc     = $ARGV[1];
@inpos   = ( $ARGV[2], $ARGV[3] );
$separ   = "_";


# error condition: pixel out of bounds
#-------------------------------------
if ( $ARGV[2] > 510 || $ARGV[2] < 0 ||
     $ARGV[3] > 510 || $ARGV[3] < 0 ||
     $ARGV[2] == 0 && $ARGV[3] == 0   )
{
  print " WFC pixel values have to lie between 0 and 511, exit \n";
  exit();
}

# error condition: date too early
#--------------------------------
if ( $ARGV[0] < 50200 )
{
  print " Mjd date = ", $ARGV[0] , ": SAX was not yet launched, exit \n";
  exit();
}

# error condition: date too late
#--------------------------------
if ( $ARGV[0] > 52000 )
{
  print " Mjd date = ", $ARGV[0] , ": SAX will have gone by then, exit \n";
   exit();
}

# error condition: wrong instrument
#--------------------------------
if ( $ARGV[1] ne "w1" && $ARGV[1] ne "w2" && $ARGV[1] ne "wfc1" && $ARGV[1] ne "wfc2" )
{
  print " WFC instrument ", $ARGV[1], " is unknown , exit \n";
  exit();
}

# change wfc names to file convention
#------------------------------------- 
if ( $wfc == "w1" ) { $wfc = "wfc1";}
if ( $wfc == "w2" ) { $wfc = "wfc2";}

# define response matrix pixel positions (grid of 5x5)
# and epochs (8, mod. julian date)
#--------------------------------------
@where       = ( 90, 173, 255, 337, 420 );
@when        = ( 50265, 50449, 50630, 50814, 50995, 51179, 51360, 51544 );
@date_string = ( "01jul96", "01jan97", "01jul97", "01jan98", "01jul98", "01jan99", "01jul99", "01jan00");
$minimum     = 100000.0;
$minimum_t   = 100000.0;

# loop over response matrix positions to find the
# most suitable response matrix: i.e., the one defined
# for the position closest by
# number of grid positions: 5 x 5
#----------------------------------------------------
foreach $i(0..4)
{
  foreach $j(0..4)
  {
    @rmfpos = ($where[$i], $where[$j]);
    &distance ( @inpos, @rmfpos );
    if ( $distance  < $minimum ) 
      { $minimum   = $distance ;
        $separ1 = "_";
        $separ2 = "_";
        if ( $where[$i] < 100 ) { $separ1 = "_0";}
        if ( $where[$j] < 100 ) { $separ2 = "_0";}

        $rmf_file       = "${wfc}${separ1}$where[$i]${separ2}$where[$j]";
#       $uncor_rmf_file = "${wfc}_u_$where[$i]_$where[$j].rmf";
      }
  }
}

#loop over dates to get nearest epoch
#------------------------------------
foreach $i(0..7)
{
   &time_distance ( $when[$i], $mjd ); 
   if ( $time_distance < $minimum_t )
     { $minimum_t  = $time_distance ;
       $when_min   = $when[$i];
       $imin       = $i;
     }
}

#print " Minimum time distance  = ", $minimum_t, " days for mjd ", $when_min, " rmf string = ", $date_string[$imin],"\n";
 
# conclude to response matrix file name
#--------------------------------------
$rmf_file = $rmf_file."_".$date_string[$imin].".rmf";
#print " Rmf file = ", $rmf_file , "\n";

# output minimum distance and suitable response matrix file name
#--------------------------------------------------------------
$~ = 'MYFORMAT';
write;

# calculate the Euclidean distance between 2 points
#--------------------------------------------------
sub distance
{

  $diff_x = $_[0] - $_[2];
  $diff_y = $_[1] - $_[3];

  $distance = sqrt ( $diff_x*$diff_x + $diff_y*$diff_y ) ;
#  print " Distance between ($_[0],$_[1]) and ($_[2],$_[3]) = " , $distance , "\n" ;

}

# calculate the time distance between 2 dates
#--------------------------------------------
sub time_distance
{
  $diff_t = $_[0] - $_[1];
  $time_distance = abs ( $diff_t );
#  print " Distance between ($_[0],$_[1]) = ", $time_distance, "\n" ;
}

format MYFORMAT = 
Distance =@###.# pixels, @###.# days to closest responsematrix @<<<<<<<<<<<<<<<<<<<<<<< 
                  $minimum       $minimum_t            $rmf_file 
.

}