use strict;
use warnings;

use Tie::File;

use Data::Dumper;

use Digest::MD5 qw(md5_hex);

# open an existing file in read-only mode
use Fcntl 'O_RDONLY';

die "Usage: $0 <unsorted input filename> <sorted output filename>" if ($#ARGV < 1);

our $recordsWrittenCount = 0;
our $fieldsSorted = 0;

our @array;

tie @array, 'Tie::File', $ARGV[0], memory => 50_000_000, mode => O_RDONLY or die "Cannot open $ARGV[0]: $!";

open(OUTFILE, ">" .  $ARGV[1]) or die "Cannot open $ARGV[1]: $!";

our @tempRecordStorage = ();

our $dx = 0;

# Now read in the EL6 file

our $numberOfLines = @array; # accessing @array in a loop might be expensive as it is tied?? 

for($dx = 0; $dx < $numberOfLines; ++$dx)
{
	if($array[$dx] eq 'RECORD')
	{
		++$recordsWrittenCount;
		
		my $endOfRecord = $dx;

		until($array[++$endOfRecord] eq '.')
		{
			push @tempRecordStorage, $array[$endOfRecord];
			++$fieldsSorted;
		}
		
		print OUTFILE "RECORD\n";

		local $, = "\n";
		print OUTFILE sort @tempRecordStorage;
		@tempRecordStorage = ();

		print OUTFILE "\n.\n"; # PERL does not postfix trailing separator after the last array element, so we need to do this ourselves)
		
		$dx = $endOfRecord;		
	}
}

close(OUTFILE);

# Display results to user

print "\n[*] Done: " . $fieldsSorted . " fields sorted from " . $recordsWrittenCount . " records written.\n";