#!/usr/local/bin/perl
# mcsimple.cgi, version 2.4 written in Perl 5.0, last revision 8/19/96.
# A PERL script that generates HTML pages containing either a 
#   multiple-choice question or the corresponding response page 
#   after the user submits an answer.
# Requires the cgi-utils.pl library, available at:
#   http://www-genome.wi.mit.edu/WWW/tools/scripting/cgi-utils.html
# The script reads the question and response information from a text
#   data file (with a *.qdf extension) of the form:
#     # The next two lines contain the page title and question topic that will be displayed at the top of the web page.
#     SEQ Question
#     Example 1
#     # The next line contains the question.
#     Where do plants get the carbon they need for growth?
#     # The next x lines are for the x number of answers for the question.
#     From the soil they are in.
#     From carbon dioxide in the atmosphere.
#     From water.
#     # The next 2 lines contain the sequential number of the correct answer and an optional explanation.
#     2
#     Plants convert carbon dioxide gas to sugar molecules via photosynthesis. The sugars store energy and provide the building blocks for the plant to grow.
#     # The next four lines are dummy slots for features not implemented.
#     NA
#     NA
#     NA
#     NA
# For more information see:
#   http://www.chem.vt.edu/chem-ed/CHP/scripts/perl/mcsimple.html.
# Program and concept by Ron Earp and Brian Tissue.
# Copyright 1996 by Ronald L. Earp and Brian M. Tissue, all rights reserved.

require "cgi-utils.pl";

# Path to the question script on YOUR server. MUST BE CHANGED!
$question_path="http://www.chem.vt.edu/cgi-bin/mcsimple.cgi";

# Set variables for question responses.
$incorrect_response="That answer is incorrect.";
$correct_response="That answer is correct.";
$answer_tag="<STRONG> *** Correct Answer *** </STRONG>";

# The following variables specify the line positions of information in
#  the data file. Counting starts at 0 for the first line of the data file.
$title1 = 1;
$title2 = 2;
$question = 4;
$answers = 6;
# The next two variables specify the positions of the correct answer and
#  explanation relative to the last answer choice. 
$answerpos = 1;
$explanationpos = 2;
# The next variable refers to the number of lines in the data file
# that are not displayed as part of the question.
$deadlines = 14; 

# Create top of HTML page.
&start_page;

# Gets the environment variables using cgi-utils.pl.
@passed = &get_query;

# Check to see if the script is being called for a question or an answer.
if ($passed[4] ne "makeanswer") 
	{
	$qfile = $passed[1];
	
	# Check for proper file type and if it can be opened
	if ($qfile =~ /.qdf/)
		{
		&checkfile;
		}
	else
		{
		$fail = 1;
		&error_message;
		}
	if ($fail != 1) 
	{
	# Read lines from the data file and store them as an array.
	$index = 0;
	@qarray = <QFILE>;
	$qlength = @qarray;

	# Code to display the question from the array. Backslash characters
	# are used to denote literals, such as @ or " within a string.
	&display_question;
	print "<FORM METHOD=GET ACTION=\"$question_path\">";
	print "\n";
	print "<INPUT TYPE=\"hidden\" NAME=\"makeanswer\" VALUE=\"yes\"> \n";
	print "<INPUT TYPE=\"hidden\" NAME=\"filename\" VALUE=\"$qfile\"> \n";

	# Display answers for question.
	print "<OL> \n";
	$maxcount = ($qlength - 14);
	$count = 0;
	while ($count < $maxcount)
		{
		$value = $count + 1;
		print "<LI><INPUT TYPE=\"radio\" NAME=\"answera\" VALUE=\"$value\">$qarray[$answers + $count] \n";
		$count++;
		} 
	print "</UL> \n";
	print "<BR>\n";
	print "<INPUT TYPE=submit value=\"Submit Answer\"> <INPUT TYPE=RESET VALUE=\"Start over\"> \n";
	print "</FORM>\n";
	print "<HR>\n";
	close(QFILE);
	}
	}
else
	{
	# Splits the query string into 2 separate pieces for use in the program.
	$qfile = $passed[3];
	$answer = $passed[1];
	
	# Check for proper file type and if it can be opened
	if ($qfile =~ /.qdf/)
		{
		&checkfile;
		}
	else
		{
		$fail = 1;
		&error_message;
		}

	if ($fail != 1) 
	{
		# Read lines from the data file and store them as an array, $qarray.
		# Data is read in exactly as stored in the datafile.
		$index = 0;
		@qarray = <QFILE>;
		$qlength = @qarray;

		# Call subroutine to display the question.
		&display_question;
		
		# Display answers for question 
		print "<OL> \n";
		$maxcount = ($qlength - $deadlines);
		$count = 0;
		while ($count < $maxcount)
			{
			if (($answers + $qarray[$answers + $maxcount + $answerpos]) == ($answers + $count + 1))
				{
				print "<LI>$qarray[$answers + $count]      $answer_tag\n";
				$count++;
				}
			else
				{
				print "<LI>$qarray[$answers+$count] \n";
				$count++;
				} 
			}
		print "</UL> \n";
		print "<HR>\n";
		
		# Branching to provide output based on the users selection.
		print "Your answer was $answer. ";
		if ($answer == $qarray[$answers + $maxcount + $answerpos])
			{
			print "$correct_response <BR> \n";
			}
		else
			{
			print "$incorrect_response <BR> \n";
			}
		$flag = $qarray[$answers + $maxcount + $explanationpos + 2];
		if ($flag ne "NO")
		 	{
			print $qarray[$answers + $maxcount + $explanationpos];
			}
		print "<BR>\n";
		print "<HR>\n";
	}
	}

# Create end of HTML page.
&end_page;
# END OF MAIN SCRIPT.

# BEGINNING OF SUBROUTINES.
sub start_page
{
	print ("Content-type: text/html\n\n");
	print ("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 3.2//EN\">\n");
	print "<HTML>\n";
}

sub end_page
{
	print "</BODY></HTML>";
}

sub error_message
{
	print "<HEAD><TITLE>File Access Error</TITLE></HEAD>\n";
	print "<P>\n";
	print "<HR>\n";
	print "<H2>Error serving request</H2>\n";
	print "Your filename is incorrect or doesn't exist. Ask your instructor to check the question link.\n";
	print "Question script is looking for:   ",$qfile,".";
}

sub checkfile
{
unless (open(QFILE, $qfile))
		{
		$fail = 1;
		&error_message;	
		}
}

sub display_question
{
	print "<HEAD><TITLE>",$qarray[$index + $title1],"</TITLE></HEAD>\n";
	print "<BODY><H1>",$qarray[$index + $title1],"</H1>\n";
	print "<H2>",$qarray[$index + $title2],"</H2>\n";
	print "<HR>\n";
	print "$qarray[$index + $question] \n";
	print "<P> \n";
}
# END OF SUBROUTINES.