--- trunk/webwork-modperl/lib/WeBWorK/ContentGenerator/Problem.pm	2002/08/20 01:07:18	476
+++ trunk/webwork-modperl/lib/WeBWorK/ContentGenerator/Problem.pm	2003/02/28 20:02:29	755
@@ -1,5 +1,5 @@
 ################################################################################
-# WeBWorK mod_perl (c) 1995-2002 WeBWorK Team, Univeristy of Rochester
+# WeBWorK mod_perl (c) 2000-2002 WeBWorK Project
 # $Id$
 ################################################################################
 
@@ -15,16 +15,16 @@
 use warnings;
 use base qw(WeBWorK::ContentGenerator);
 use CGI qw();
+use File::Temp qw(tempdir);
 use WeBWorK::Form;
 use WeBWorK::PG;
-use WeBWorK::Utils qw(ref2string encodeAnswers decodeAnswers);
-
-# TODO:
-# 7. make warnings work
+use WeBWorK::PG::IO;
+use WeBWorK::Utils qw(writeLog encodeAnswers decodeAnswers ref2string);
 
 ############################################################
 # 
 # user
+# effectiveUser
 # key
 # 
 # displayMode
@@ -45,10 +45,7 @@
 	my $courseEnv = $self->{courseEnvironment};
 	my $r = $self->{r};
 	my $userName = $r->param('user');
-	
-	# fix format of setName and problem
-	$setName =~ s/^set//;
-	$problemNumber =~ s/^prob//;
+	my $effectiveUserName = $r->param('effectiveUser');
 	
 	##### database setup #####
 	
@@ -57,29 +54,56 @@
 	my $authdb = WeBWorK::DB::Auth->new($courseEnv);
 	
 	my $user            = $cldb->getUser($userName);
-	my $set             = $wwdb->getSet($userName, $setName);
-	my $problem         = $wwdb->getProblem($userName, $setName, $problemNumber);
+	my $effectiveUser   = $cldb->getUser($effectiveUserName);
+	my $set             = $wwdb->getSet($effectiveUserName, $setName);
+	my $problem         = $wwdb->getProblem($effectiveUserName, $setName, $problemNumber);
+	my $psvn            = $wwdb->getPSVN($effectiveUserName, $setName);
 	my $permissionLevel = $authdb->getPermissions($userName);
 	
+	$self->{cldb}            = $cldb;
+	$self->{wwdb}            = $wwdb;
+	$self->{authdb}          = $authdb;
+	
+	$self->{userName}        = $userName;
+	$self->{user}            = $user;
+	$self->{effectiveUser}   = $effectiveUser;
+	$self->{set}             = $set;
+	$self->{problem}         = $problem;
+	$self->{permissionLevel} = $permissionLevel;
+	
 	##### form processing #####
 	
 	# set options from form fields (see comment at top of file for names)
-	my $displayMode        = $r->param("displayMode")        || $courseEnv->{pg}->{options}->{displayMode};
+	my $displayMode        = $r->param("displayMode") || $courseEnv->{pg}->{options}->{displayMode};
 	my $redisplay          = $r->param("redisplay");
 	my $submitAnswers      = $r->param("submitAnswers");
+	my $checkAnswers       = $r->param("checkAnswers");
+	my $previewAnswers     = $r->param("previewAnswers");
 	
 	# coerce form fields into CGI::Vars format
 	my $formFields = { WeBWorK::Form->new_from_paramable($r)->Vars };
 	
+	$self->{displayMode}    = $displayMode;
+	$self->{redisplay}      = $redisplay;
+	$self->{submitAnswers}  = $submitAnswers;
+	$self->{checkAnswers}   = $checkAnswers;
+	$self->{previewAnswers} = $previewAnswers;
+	$self->{formFields}     = $formFields;
+	
 	##### permissions #####
 	
+	# are we allowed to view this problem?
+	$self->{isOpen} = time >= $set->open_date || $permissionLevel > 0;
+	return unless $self->{isOpen};
+	
 	# what does the user want to do?
 	my %want = (
 		showOldAnswers     => $r->param("showOldAnswers")     || $courseEnv->{pg}->{options}->{showOldAnswers},
 		showCorrectAnswers => $r->param("showCorrectAnswers") || $courseEnv->{pg}->{options}->{showCorrectAnswers},
 		showHints          => $r->param("showHints")          || $courseEnv->{pg}->{options}->{showHints},
 		showSolutions      => $r->param("showSolutions")      || $courseEnv->{pg}->{options}->{showSolutions},
-		recordAnswers      => $r->param("recordAnswers")      || 1,
+		recordAnswers      => $submitAnswers,
+		checkAnswers       => $checkAnswers,
 	);
 	
 	# are certain options enforced?
@@ -89,6 +113,7 @@
 		showHints          => 0,
 		showSolutions      => 0,
 		recordAnswers      => mustRecordAnswers($permissionLevel),
+		checkAnswers       => 0,
 	);
 	
 	# does the user have permission to use certain options?
@@ -97,14 +122,17 @@
 		showCorrectAnswers => canShowCorrectAnswers($permissionLevel, $set->answer_date),
 		showHints          => 1,
 		showSolutions      => canShowSolutions($permissionLevel, $set->answer_date),
+		# attempts=num_correct+num_incorrect+1, as this happens before updating $problem
 		recordAnswers      => canRecordAnswers($permissionLevel, $set->open_date, $set->due_date,
 			$problem->max_attempts, $problem->num_correct + $problem->num_incorrect + 1),
-			# num_correct+num_incorrect+1 -- as this happens before updating $problem
+		checkAnswers       => canCheckAnswers($permissionLevel, $set->open_date,
+			$set->due_date, $set->answer_date, $problem->max_attempts,
+			$problem->num_correct + $problem->num_incorrect + 1),
 	);
 	
 	# final values for options
 	my %will;
-	foreach(keys %must) {
+	foreach (keys %must) {
 		$will{$_} = $can{$_} && ($want{$_} || $must{$_});
 	}
 	
@@ -120,36 +148,27 @@
 	
 	my $pg = WeBWorK::PG->new(
 		$courseEnv,
-		$r->param('user'),
+		$effectiveUser,
 		$r->param('key'),
-		$setName,
-		$problemNumber,
+		$set,
+		$problem,
+		$psvn,
+		$formFields,
 		{ # translation options
 			displayMode     => $displayMode,
 			showHints       => $will{showHints},
 			showSolutions   => $will{showSolutions},
 			refreshMath2img => $will{showHints} || $will{showSolutions},
-			# try leaving processAnswers on all the time?
-			processAnswers  => 1, #$submitAnswers ? 1 : 0,
+			processAnswers  => 1,
 		},
-		$formFields
 	);
 	
-	##### store fields #####
+	##### fix hint/solution options #####
 	
-	$self->{cldb}            = $cldb;
-	$self->{wwdb}            = $wwdb;
-	$self->{authdb}          = $authdb;
+	$can{showHints}     &&= $pg->{flags}->{hintExists};
+	$can{showSolutions} &&= $pg->{flags}->{solutionExists};
 	
-	$self->{user}            = $user;
-	$self->{set}             = $set;
-	$self->{problem}         = $problem;
-	$self->{permissionLevel} = $permissionLevel;
-	
-	$self->{displayMode}   = $displayMode;
-	$self->{redisplay}     = $redisplay;
-	$self->{submitAnswers} = $submitAnswers;
-	$self->{formFields}    = $formFields;
+	##### store fields #####
 	
 	$self->{want} = \%want;
 	$self->{must} = \%must;
@@ -159,9 +178,23 @@
 	$self->{pg} = $pg;
 }
 
-#sub header {
-#	# *** we need to print $pg->{header_text} here!
-#}
+sub if_warnings($$) {
+	my ($self, $arg) = @_;
+	return 0 unless $self->{isOpen};
+	return $self->{pg}->{warnings} ne "";
+}
+
+sub if_errors($$) {
+	my ($self, $arg) = @_;
+	return 0 unless $self->{isOpen};
+	return $self->{pg}->{flags}->{error_flag};
+}
+
+sub head {
+	my $self = shift;
+	return "" unless $self->{isOpen};
+	return $self->{pg}->{head_text} if $self->{pg}->{head_text};
+}
 
 sub path {
 	my $self = shift;
@@ -175,7 +208,7 @@
 	return $self->pathMacro($args,
 		"Home" => "$root",
 		$courseName => "$root/$courseName",
-		$setName => "$root/$courseName/set$setName",
+		$setName => "$root/$courseName/$setName",
 		"Problem $problemNumber" => "",
 	);
 }
@@ -189,14 +222,17 @@
 	my $root = $ce->{webworkURLs}->{root};
 	my $courseName = $ce->{courseName};
 	
+	print CGI::strong("Problems"), CGI::br();
+	
 	my $wwdb = $self->{wwdb};
-	my $user = $self->{r}->param("user");
+	my $effectiveUser = $self->{r}->param("effectiveUser");
 	my @problems;
-	push @problems, $wwdb->getProblem($user, $setName, $_)
-		foreach ($wwdb->getProblems($user, $setName));
+	push @problems, $wwdb->getProblem($effectiveUser, $setName, $_)
+		foreach ($wwdb->getProblems($effectiveUser, $setName));
 	foreach my $problem (sort { $a->id <=> $b->id } @problems) {
 		print CGI::a({-href=>"$root/$courseName/$setName/".$problem->id."/?"
-			. $self->url_authen_args}, "Problem ".$problem->id), CGI::br();
+			. $self->url_authen_args . "&displayMode=" . $self->{displayMode}},
+				"Problem ".$problem->id), CGI::br();
 	}
 }
 
@@ -210,19 +246,22 @@
 	my $root = $ce->{webworkURLs}->{root};
 	my $courseName = $ce->{courseName};
 	
-	my $wwdb = $self->{wwdb};
-	my $user = $self->{r}->param("user");
-	
-	my @links = ("Problem List" => "$root/$courseName/set$setName");
-	
-	my $prevProblem = $wwdb->getProblem($user, $setName, $problemNumber-1);
-	my $nextProblem = $wwdb->getProblem($user, $setName, $problemNumber+1);
-	unshift @links, "Previous Problem" => "$root/$courseName/set$setName/prob".$prevProblem->id
-		if $prevProblem;
-	push @links, "Next Problem" => "$root/$courseName/set$setName/prob".$nextProblem->id
-		if $nextProblem;
+	my $wwdb          = $self->{wwdb};
+	my $effectiveUser = $self->{r}->param("effectiveUser");
+	my $tail = "&displayMode=".$self->{displayMode};
+	
+	my @links = ("Problem List" , "$root/$courseName/$setName", "ProbList");
+	
+	my $prevProblem = $wwdb->getProblem($effectiveUser, $setName, $problemNumber-1);
+	my $nextProblem = $wwdb->getProblem($effectiveUser, $setName, $problemNumber+1);
+	unshift @links, "Previous Problem" , ($prevProblem
+		? "$root/$courseName/$setName/".$prevProblem->id
+		: "") , "Prev";
+	push @links, "Next Problem" , ($nextProblem
+		? "$root/$courseName/$setName/".$nextProblem->id
+		: "") , "Next";
 	
-	return $self->navMacro($args, @links);
+	return $self->navMacro($args, $tail, @links);
 }
 
 sub title {
@@ -236,7 +275,8 @@
 sub body {
 	my $self = shift;
 	
-	#$self->prepare(@_);
+	return CGI::p(CGI::font({-color=>"red"}, "This problem is not available because the problem set that contains it is not yet open."))
+		unless $self->{isOpen};
 	
 	# unpack some useful variables
 	my $r               = $self->{r};
@@ -245,14 +285,18 @@
 	my $problem         = $self->{problem};
 	my $permissionLevel = $self->{permissionLevel};
 	my $submitAnswers   = $self->{submitAnswers};
+	my $checkAnswers    = $self->{checkAnswers};
+	my $previewAnswers  = $self->{previewAnswers};
+	my %want            = %{ $self->{want} };
+	my %can             = %{ $self->{can} };
+	my %must            = %{ $self->{must} };
 	my %will            = %{ $self->{will} };
 	my $pg              = $self->{pg};
 	
 	##### translation errors? #####
 	
 	if ($pg->{flags}->{error_flag}) {
-		print translationError($pg->{errors}, $pg->{body_text});
-		return "";
+		return $self->errorOutput($pg->{errors}, $pg->{body_text});
 	}
 	
 	##### answer processing #####
@@ -276,18 +320,70 @@
 			$problem->num_correct($pg->{state}->{num_of_correct_ans});
 			$problem->num_incorrect($pg->{state}->{num_of_incorrect_ans});
 			$wwdb->setProblem($problem);
+			# write to the transaction log, just to make sure
+			writeLog($self->{courseEnvironment}, "transaction",
+				$problem->id."\t".
+				$problem->set_id."\t".
+				$problem->login_id."\t".
+				$problem->source_file."\t".
+				$problem->value."\t".
+				$problem->max_attempts."\t".
+				$problem->problem_seed."\t".
+				$problem->status."\t".
+				$problem->attempted."\t".
+				$problem->last_answer."\t".
+				$problem->num_correct."\t".
+				$problem->num_incorrect
+			);
 		}
 	}
 	
 	##### output #####
-	
+	print CGI::start_div({class=>"problemHeader"});
 	# attempt summary
 	if ($submitAnswers or $will{showCorrectAnswers}) {
 		# print this if user submitted answers OR requested correct answers
-		print attemptResults($pg, $submitAnswers, $will{showCorrectAnswers},
-			$pg->{flags}->{showPartialCorrectAnswers});
+		print $self->attemptResults($pg, $submitAnswers,
+			$will{showCorrectAnswers},
+			$pg->{flags}->{showPartialCorrectAnswers}, 1, 0);
+	} elsif ($checkAnswers) {
+		# print this if user previewed answers
+		print $self->attemptResults($pg, 1, 0, 1, 1, 0);
+			# show attempt answers
+			# don't show correct answers
+			# show attempt results (correctness)
+			# don't show attempt previews
+	} elsif ($previewAnswers) {
+		# print this if user previewed answers
+		print $self->attemptResults($pg, 1, 0, 0, 0, 1);
+			# show attempt answers
+			# don't show correct answers
+			# don't show attempt results (correctness)
+			# show attempt previews
 	}
 	
+	print CGI::end_div();
+	
+	print CGI::start_div({class=>"problem"});
+	#print CGI::hr();
+	# main form
+	print
+		CGI::startform("POST", $r->uri),
+		$self->hidden_authen_fields,
+		CGI::p($pg->{body_text}),
+		CGI::p($pg->{result}->{msg} ? CGI::b("Note: ") : "", CGI::i($pg->{result}->{msg})),
+		CGI::p(
+			($can{recordAnswers}
+				? CGI::submit(-name=>"submitAnswers",
+					-label=>"Submit Answers")
+				: ""),
+			($can{checkAnswers}
+				? CGI::submit(-name=>"checkAnswers",
+					-label=>"Check Answers")
+				: ""),
+			CGI::submit(-name=>"previewAnswers",
+				-label=>"Preview Answers"),
+		);
 	# score summary
 	my $attempts = $problem->num_correct + $problem->num_incorrect;
 	my $attemptsNoun = $attempts != 1 ? "times" : "time";
@@ -301,8 +397,11 @@
 		$attemptsLeft = $problem->max_attempts - $attempts;
 		$attemptsLeftNoun = $attemptsLeft == 1 ? "attempt" : "attempts";
 	}
+	
+	my $setClosed = 0;
 	my $setClosedMessage;
 	if (time < $set->open_date or time > $set->due_date) {
+		$setClosed = 1;
 		$setClosedMessage = "This problem set is closed.";
 		if ($permissionLevel > 0) {
 			$setClosedMessage .= " Since you are a privileged user, additional attempts will be recorded.";
@@ -315,101 +414,115 @@
 		$problem->attempted
 			? "Your recorded score is $lastScore." . CGI::br()
 			: "",
-		"You have $attemptsLeft $attemptsLeftNoun remaining.", CGI::br(),
-		$setClosedMessage,
+		$setClosed ? $setClosedMessage : "You have $attemptsLeft $attemptsLeftNoun remaining."
 	);
 	
-	# BY THE WAY..........
-	# we have to figure out some way to tell the student if their NEW answer,
-	# on THIS attempt, has been recorded. however, this is decided in part by
-	# the grader, so is there any way for us to know? we can rule out several
-	# cases where the answer is NOT being recorded, because of things decided
-	# in &canRecordAnswers...
-	
-	print CGI::hr();
-	
-	# main form
+		
 	print
-		CGI::startform("POST", $r->uri),
+		$self->viewOptions(),
+		CGI::endform();
+		
+	print CGI::end_div();
+	# feedback form
+	my $ce = $self->{courseEnvironment};
+	my $root = $ce->{webworkURLs}->{root};
+	my $courseName = $ce->{courseName};
+	my $feedbackURL = "$root/$courseName/feedback/";
+	print
+		CGI::startform("POST", $feedbackURL),
 		$self->hidden_authen_fields,
-		CGI::p(CGI::i($pg->{result}->{msg})),
-		CGI::p($pg->{body_text}),
-		CGI::p(CGI::submit(-name=>"submitAnswers", -label=>"Submit Answers")),
-		$self->viewOptions,
+		CGI::hidden("module",             __PACKAGE__),
+		CGI::hidden("set",                $set->id),
+		CGI::hidden("problem",            $problem->id),
+		CGI::hidden("displayMode",        $self->{displayMode}),
+		CGI::hidden("showOldAnswers",     $will{showOldAnswers}),
+		CGI::hidden("showCorrectAnswers", $will{showCorrectAnswers}),
+		CGI::hidden("showHints",          $will{showHints}),
+		CGI::hidden("showSolutions",      $will{showSolutions}),
+		CGI::p({-align=>"right"},
+			CGI::submit(-name=>"feedbackForm", -label=>"Send Feedback")
+		),
 		CGI::endform();
 	
+	# warning output
+	if ($pg->{warnings} ne "") {
+		print CGI::hr(), $self->warningOutput($pg->{warnings});
+	}
+	
 	# debugging stuff
-	#print
-	#	hr(),
-	#	h2("debugging information"),
-	#	h3("form fields"),
-	#	ref2string($formFields),
-	#	h3("user object"),
-	#	ref2string($user),
-	#	h3("set object"),
-	#	ref2string($set),
-	#	h3("problem object"),
-	#	ref2string($problem),
-	#	h3("PG object"),
-	#	ref2string($pg, {'WeBWorK::PG::Translator' => 1});
+	if (0) {
+		print
+			CGI::hr(),
+			CGI::h2("debugging information"),
+			CGI::h3("form fields"),
+			ref2string($self->{formFields}),
+			CGI::h3("user object"),
+			ref2string($self->{user}),
+			CGI::h3("set object"),
+			ref2string($set),
+			CGI::h3("problem object"),
+			ref2string($problem),
+			CGI::h3("PG object"),
+			ref2string($pg, {'WeBWorK::PG::Translator' => 1});
+	}
 	
 	return "";
 }
 
 ##### output utilities #####
 
-sub translationError($$) {
-	my ($error, $details) = @_;
-	return
-		CGI::h2("Software Error"),
-		CGI::p(<<EOF),
-WeBWorK has encountered a software error while attempting to process this problem.
-It is likely that there is an error in the problem itself.
-If you are a student, contact your professor to have the error corrected.
-If you are a professor, please consut the error output below for more informaiton.
-EOF
-		CGI::h3("Error messages"), CGI::blockquote(CGI::pre($error)),
-		CGI::h3("Error context"), CGI::blockquote(CGI::pre($details));
-}
-
-sub attemptResults($$$) {
+sub attemptResults($$$$$$) {
+	my $self = shift;
 	my $pg = shift;
 	my $showAttemptAnswers = shift;
 	my $showCorrectAnswers = shift;
 	my $showAttemptResults = $showAttemptAnswers && shift;
+	my $showSummary = shift;
+	my $showAttemptPreview = shift || 0;
 	my $problemResult = $pg->{result}; # the overall result of the problem
 	my @answerNames = @{ $pg->{flags}->{ANSWER_ENTRY_ORDER} };
 	
-	my $header = CGI::th("answer");
-	$header .= $showAttemptAnswers ? CGI::th("attempt")  : "";
-	$header .= $showCorrectAnswers ? CGI::th("correct")  : "";
-	$header .= $showAttemptResults ? CGI::th("result")   : "";
-	$header .= $showAttemptAnswers ? CGI::th("messages") : "";
+	my $showMessages = $showAttemptAnswers && grep { $pg->{answers}->{$_}->{ans_message} } @answerNames;
+	
+	my $header = CGI::th("Part");
+	$header .= $showAttemptAnswers ? CGI::th("Entered")  : "";
+	$header .= $showAttemptPreview ? CGI::th("Answer Preview")  : "";
+	$header .= $showCorrectAnswers ? CGI::th("Correct")  : "";
+	$header .= $showAttemptResults ? CGI::th("Result")   : "";
+	$header .= $showMessages       ? CGI::th("messages") : "";
 	my @tableRows = ( $header );
 	my $numCorrect;
 	foreach my $name (@answerNames) {
 		my $answerResult  = $pg->{answers}->{$name};
 		my $studentAnswer = $answerResult->{student_ans}; # original_student_ans
+		my $preview       = ($showAttemptPreview
+		                    	? $self->previewAnswer($answerResult)
+					: "");
 		my $correctAnswer = $answerResult->{correct_ans};
 		my $answerScore   = $answerResult->{score};
-		my $answerMessage = $showAttemptAnswers ? $answerResult->{ans_message} : "";
+		my $answerMessage = $showMessages ? $answerResult->{ans_message} : "";
 		
 		$numCorrect += $answerScore > 0;
-		my $resultString = $answerScore ? "correct :^)" : "incorrect >:(";
+		my $resultString = $answerScore ? "correct" : "incorrect";
+		
+		# get rid of the goofy prefix on the answer names (supposedly, the format
+		# of the answer names is changeable. this only fixes it for "AnSwEr"
+		$name =~ s/^AnSwEr//;
 		
 		my $row = CGI::td($name);
 		$row .= $showAttemptAnswers ? CGI::td($studentAnswer) : "";
+		$row .= $showAttemptPreview ? CGI::td($preview)       : "";
 		$row .= $showCorrectAnswers ? CGI::td($correctAnswer) : "";
 		$row .= $showAttemptResults ? CGI::td($resultString)  : "";
 		$row .= $answerMessage      ? CGI::td($answerMessage) : "";
 		push @tableRows, $row;
 	}
 	
-	my $numCorrectNoun = $numCorrect == 1 ? "question" : "questions";
+	my $numIncorrectNoun = scalar @answerNames == 1 ? "question" : "questions";
 	my $scorePercent = int ($problemResult->{score} * 100) . "\%";
-	my $summary = "On this attempt, you answered $numCorrect $numCorrectNoun out of "
-		. scalar @answerNames . " correct, for a score of $scorePercent.";
-	return CGI::table({-border=>1}, CGI::Tr(\@tableRows)) . CGI::p($summary);
+	my $summary = "On this attempt, you answered $numCorrect out of "
+		. scalar @answerNames . " $numIncorrectNoun correct, for a score of $scorePercent.";
+	return CGI::table({-class=>"attemptResults"}, CGI::Tr(\@tableRows)) . ($showSummary ? CGI::p($summary) : "");
 }
 
 sub viewOptions($) {
@@ -464,6 +577,65 @@
 	);
 }
 
+sub previewAnswer($$) {
+	my ($self, $answerResult) = @_;
+	my $ce            = $self->{courseEnvironment};
+	my $effectiveUser = $self->{effectiveUser};
+	my $set           = $self->{set};
+	my $problem       = $self->{problem};
+	my $displayMode   = $self->{displayMode};
+	
+	# note: right now, we have to do things completely differently when we are
+	# rendering math from INSIDE the translator and from OUTSIDE the translator.
+	# so we'll just deal with each case explicitly here. there's some code
+	# duplication that can be dealt with later by abstracting out tth/dvipng/etc.
+	
+	my $tex = $answerResult->{preview_latex_string};
+	
+	return "" unless $tex;
+	
+	if ($displayMode eq "plainText") {
+		return $tex;
+	} elsif ($displayMode eq "formattedText") {
+		my $tthCommand = $ce->{externalPrograms}->{tth}
+			. " -L -f5 -r 2> /dev/null <<END_OF_INPUT; echo > /dev/null\n"
+			. "\\(".$tex."\\)\n"
+			. "END_OF_INPUT\n";
+		
+		# call tth
+		my $result = `$tthCommand`;
+		if ($?) {
+			return "<b>[tth failed: $? $@]</b>";
+		}
+		return $result;
+	} elsif ($displayMode eq "images") {
+		# how are we going to name this?
+		my $targetPathCommon = "/png/"
+			. $effectiveUser->id . "."
+			. $set->id . "."
+			. $problem->id . "."
+			. $answerResult->{ans_name} . ".png";
+
+		# figure out where to put things
+		my $wd = tempdir("webwork-dvipng-XXXXXXXX", DIR => $ce->{courseDirs}->{html_temp});
+		my $latex = $ce->{externalPrograms}->{latex};
+		my $dvipng = $ce->{externalPrograms}->{dvipng};
+		my $targetPath = $ce->{courseDirs}->{html_temp} . $targetPathCommon;
+				# should use surePathToTmpFile, but we have to
+				# isolate it from the problem enivronment first
+		my $targetURL = $ce->{courseURLs}->{html_temp} . $targetPathCommon;
+
+		# call dvipng to generate a preview
+		warn $tex;
+		dvipng($wd, $latex, $dvipng, $tex, $targetPath);
+		if (-e $targetPath) {
+			return "<img src=\"$targetURL\" alt=\"$tex\" />";
+		} else {
+			return "<b>[math2img failed]</b>";
+		}
+	}
+}
+
 ##### permission queries #####
 
 # this stuff should be abstracted out into the permissions system
@@ -488,8 +660,14 @@
 	my ($permissionLevel, $openDate, $dueDate, $maxAttempts, $attempts) = @_;
 	my $permHigh = $permissionLevel > 0;
 	my $timeOK = time >= $openDate && time <= $dueDate;
-	my $attemptsOK = $attempts <= $maxAttempts;
-	return $permHigh || ($timeOK && $attemptsOK);
+	my $attemptsOK = $maxAttempts == -1 || $attempts <= $maxAttempts;
+	my $recordAnswers = $permHigh || ($timeOK && $attemptsOK);
+	return $recordAnswers;
+}
+
+sub canCheckAnswers($$$$$) {
+	my ($permissionLevel, $openDate, $dueDate, $answerDate, $maxAttempts, $attempts) = @_;
+	return time >= $answerDate or canRecordAnswers($permissionLevel, $openDate, $dueDate, $maxAttempts, $attempts);
 }
 
 sub mustRecordAnswers($) {