use strict;
use warnings;
use Digest::MD5;

my $sourcedirectory = '//path/to/directory';

&main();

sub main {

	# creating file array
	my @files = &getfiles($sourcedirectory);
	# removal of the two directory structures which form the start of the file array
	my $rmdir = shift (@files);
	my $rmdir2 = shift (@files);

	# capture of a count of the number of files remaining in the array
	my $filecount = @files;
	
	# check to see if there are no files, if none, exit script
	if ($filecount == 0) {
		print "\nNo files to process\n\n";
		exit;
	}
	# where there are files, the routine subroutine is called for each item individually (except for md5 file types)
	else {
		foreach my $item (@files) {
			next if $item =~ /.md5/;
			my $filepath = "$sourcedirectory/$item";
			&routine($filepath, $item);
		}
	
	}
}


sub routine {

	# identify filepath and name as parameters passed to routine
	my $file = shift;
	my $name = shift;
	
	# open file, set to binary mode, close and process MD5
	open my $fh, '<', $file or die "Can't open file: $!";
	binmode ($fh);
	my $md5tocompare = &processmd5($fh);
	close $fh or die "Can't close file successfully: $!";
	
	# check file.md5 existence and open and read to memory
	open my $fh2, '<', "$file.md5" or next;
	my $originalmd5 = <$fh2>;
	close $fh2 or die "Can't close file successfully: $!";
	
	# check parity
	print "MD5 is $md5tocompare against orignal MD5 of $originalmd5\n";
	
	next if $md5tocompare eq $originalmd5;
	&logmd5($md5tocompare, $name);
}

# subroutine to process the MD5 Hex value of a filehandle passed
sub processmd5 {
	
	my $io_handle = shift;
	my $md5 = Digest::MD5->new;
	$md5->addfile($io_handle);
	my $value = $md5->hexdigest;
	return $value;
	
}

# logreport subroutine that receives a string message as an argument, and processes the log entry
sub logmd5 {
	
	# message, and definition of date/time variables to enable logging
	my $md5 = shift;
	my $md5filename = shift;
	my $md5file = "$sourcedirectory/Log.txt";
	# opening of log and appending of md5 to the log
	open(LOG, '>>', $md5file) or die "Can't open logfile $!";
	print LOG "ERROR: $md5filename does not match - $md5 is not the original checksum";
	close LOG;

}

# a subroutine to enable definition of files to be processed
sub getfiles {
	
	my $sourcefiles = shift;
	my @file_list;
	opendir(DIR, $sourcefiles) or die "Can't open directory, $!\n";
	@file_list = readdir(DIR);
	closedir(DIR);
	return @file_list;
	
}