#!/usr/bin/perl

# Routine to correct the syntax error in the NNSN FITS headers that list
# "A'HEARN" in the observer field, as identified in the "ahearn.lst" file.
# We'll need to fix both the FITS headers and PDS labels for these files.
# Fortunately, it looks like we can assume the OBSERVER line in the headers
# always occurs as the 15th line in the first FITS block and the 22nd line
# in the corresponding PDS label.
#
# Format: % fixmaobs

$TMPFILE = "__bob.tmp";

# First, we'll read the corrected lines from a file into a hash for easy
# reference and substitution later:

open (LST,"ahearn.new")  ||  die "Could not open 'ahearn.new' ($!)";

while ($line=<LST>)
  { chop $line;
    $filename = substr($line,0,8);
    $obsname  = substr($line,13);
    $newfits{$filename} = sprintf "%-80.80s", $obsname;
    
    $obsname =~ s/^[^']+'//;
    $obsname =~ s/' \/.*$//;
    $obsname =~ s/''/'/;
    $newpds{$filename} = sprintf "%-78.78s\r\n",
                                 "OBSERVER_FULL_NAME    = \"$obsname\"";
  }
close(LST);

# Now we'll loop through the list of files to be corrected (this list has the
# path information):

open (LST,"ahearn.lst")  ||  die "Could not open 'ahearn.lst' ($!)";

while ($file=<LST>)
  { chop $file;
    $filename = substr($file,12,8);

    # We'll start with the FITS file.  We know the OBSERVER line is the 15th
    # in the first FITS block.

    open (TMP,">$TMPFILE")  ||  die "Could not open $TMPFILE ($!)";
    open (FIT,$file)  ||  die "Could not open $file ($!)";

    read FIT,$block,2880;
    substr($block,1120,80) = $newfits{$filename};
    syswrite TMP,$block,2880;

    # Now just copy the rest of the file:

    while (!eof(FIT))
      { read FIT, $block, 2880;
        syswrite TMP, $block, 2880;
      }
    close(FIT);
    close(TMP);

    rename $TMPFILE, $file;

    # Now we'll do the PDS label.  We expect to find the OBSERVER line at line
    # 22 of the PDS label:

    $pdsname = $file;
    $pdsname =~ s/\.fit/.lbl/;

    open (TMP,">$TMPFILE")  ||  die "Could not open $TMPFILE ($!)";
    open (PDS,$pdsname)  ||  die "Could not open $pdsname ($!)";

    # Find the OBSERVER_FULL_NAME line and replace it with the new one:

    $line = <PDS>;

    while ($line !~ /^ *OBSERVER_FULL_NAME/)
      { print TMP $line;
        $line=<PDS>;
      }

    print TMP $newpds{$filename};

    # Transfer the rest of the label file:

    while ($line=<PDS>)
      { print TMP $line; }

    close(TMP);
    close(PDS);

    rename $TMPFILE, $pdsname;

  }