#!/usr/bin/perl -w

#This module will take as input a string of DNA and print an output 
#file which contains the ORF's found in the DNA string. This is an 
#adjustment to somethign done last week, as you should recognize.

print "\nStoring codon information:\n\n";

print "Please enter DNA data file with no markings:\n";

$dnadataname = <STDIN>;

chomp $dnadataname;

#It is a good idea when you have an interactive data entry to have 
#an unless line to explain why the program stopped, if it had to:

unless(open(FILE,$dnadataname)){
	print "Trouble opening DNA data file\.\n\n";
	exit;
}

@DNA = <FILE>;

$longstring = join('',@DNA);
$longstring =~ s/\n//g;
$longstring =~ s/\s//g;

print "\nORF's in the original sequence:\n\n";

@nucleotides = split('',$longstring);

#As we already saw, this is how you open an output file. Don't forget
#the " "'s or > in the open(STOREDORFS, ">$outputfile)! 

$outputfile = "storedorfs";
unless(open(STOREDORFS, ">$outputfile")){
	print "\n Cannot open file \"$outputfile\"\n";
	exit;
}

close FILE;

$location = 0;
$ATG = 0;
$ORF = 0;

#This next loop is the main piece, and mainly taken from last week:

while($location < @nucleotides - 2)   
{$a = $nucleotides[$location].$nucleotides[$location + 1].$nucleotides[$location + 2];
	 ++$location;
     if($a =~ /ATG/i)
	  { $b = $location;
		print "ATG found at position $location\n";
		++$ATG;
		while($b < @nucleotides - 1){
			$c = $nucleotides[$b-1].$nucleotides[$b].$nucleotides[$b+1];
			if($c =~ /TAA/i){
				++$ORF;
				print "TAA found at position $b\.\n";
				$b = $b+2;
				print "ORF number $ORF from position $location to $b\.\n";

#The next two lines are the new part, and are repeated in each of the three if loops
#which check the three types of stop codons as the end of our ORF. The first 
#creates a string by the substr (=substring) function. It looks like sunstr($A,$B,$C), 
#where $A is a scalar variable (i.e., a string), $B is a numeric variable which 
#tells you the beginning position of the substring, and $C tells what the length 
#of the substring will be. So the next example below creates a string (named 
#$string) which is a substring of $longline, beginning at position $location -1 (I 
#switched back to the Perl location system, which starts from 0, not 1), and is 
#$b - $location + 1 characters long. It is then printed to theoutputfile as an added
#line in that file.

				$string = substr($longstring, $location-1, $b - $location + 1);
				print STOREDORFS ">ORF number $ORF:\n$string\n\n";
				$b = @nucleotides;
			}elsif($c =~ /TAG/i){
				++$ORF;
				print "TAG found at position $b\.\n";
				$b = $b+2;
				print "ORF number $ORF from position $location to $b\.\n\n";
				$string = substr($longstring, $location-1, $b - $location + 1);
				print STOREDORFS ">ORF number $ORF:\n$string\n\n";
				$b = @nucleotides;
			}elsif($c =~ /TGA/i){
				++$ORF;
				print "TGA found at position $b\.\n";
				$b = $b+2;
				print "ORF number $ORF from position $location to $b\.\n\n";
				$string = substr($longstring, $location-1, $b - $location + 1);
				print STOREDORFS ">ORF number $ORF:\n$string\n\n";
				$b = @nucleotides;
			}$b = $b + 3;
		}
	}$location = $location + 2;
}


print "\nTotal number of ORF\'s found in the original sequence = $ORF\.\n\n";

close STOREDORFS;

#Now let us have a look at what we have put in the file. The outputfile should remain
#as a file in the directory in which you have been using Perl.

$odata = "storedorfs";

open(ODATA,$odata);

@orfdata = <ODATA>;

close ODATA;

print "Here is what is contained in the file \"storedorfs\":\n";
print @orfdata;

exit;