# The LearningOnline Network with CAPA
# (Publication Handler
#
# $Id: lonchart.pm,v 1.58 2002/07/08 16:50:03 stredwic Exp $
#
# Copyright Michigan State University Board of Trustees
#
# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
#
# LON-CAPA is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# LON-CAPA is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with LON-CAPA; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# /home/httpd/html/adm/gpl.txt
#
# http://www.lon-capa.org/
#
# Homework Performance Chart
#
# (Navigate Maps Handler
#
# (Page Handler
#
# (TeX Content Handler
# YEAR=2000
# 05/29/00,05/30 Gerd Kortemeyer)
# 08/30,08/31,09/06,09/14,09/15,09/16,09/19,09/20,09/21,09/23,
# 10/02,10/10,10/14,10/16,10/18,10/19,10/31,11/6,11/14,11/16 Gerd Kortemeyer)
# YEAR=2001
# 3/1/1,6/1,17/1,29/1,30/1,31/1 Gerd Kortemeyer)
# 7/10/01 Behrouz Minaei
# 9/8 Gerd Kortemeyer
# 10/1, 10/19, 11/17, 11/22, 11/24, 11/28 12/18 Behrouz Minaei
# YEAR=2002
# 2/1, 2/6, 2/19, 2/28 Behrouz Minaei
#
###

=pod

=head1 NAME

lonchart

=head1 SYNOPSIS

Quick display of students grades for a course in a compressed table format.

=head1 DESCRIPTION

This module process all student grades for a course and turns them into a 
table like structure.

This is part of the LearningOnline Network with CAPA project
described at http://www.lon-capa.org

lonchart presents the user with a condensed view all a course's data.  The
class title, the number of students, and the date for the last update of the
displayed data.  There is also a legend that describes the chart values.  

For each valid grade for a student is linked with a submission record for that
problem.  The ability to add and remove columns of data from the chart was
added for reducing the burden of having to scroll through large quantities
of data.  The interface also allows for sorting of students by username,
last name, and section number of class.  Active and expired students are
also available.

The interface is controlled by three primary buttons: Recalculate Chart, 
Refresh Chart, and Reset Selections.  Recalculate Chart will update 
the chart to the most recent data and keep the display settings for the chart
the same.  Refresh Chart is used to redisplay the chart after selecting
different output formatting.  Reset Selections is used to set the chart
display options back to default values.

=head1 CODE LAYOUT DESCRIPTION

The code is broken down into five components: formatting data for printing,
downloading data from servers, processing data, helper functions,
and the central processing functions.  The module is broken into chunks
for each component.

=head1 PACKAGES USED

 Apache::Constants qw(:common :http)
 Apache::lonnet()
 Apache::loncommon()
 HTML::TokeParser
 GDBM_File

=cut

package Apache::lonchart;

use strict;
use Apache::Constants qw(:common :http);
use Apache::lonnet();
use Apache::loncommon();
use HTML::TokeParser;
use GDBM_File;

#my $jr; 

=pod

=head1 FORMAT DATA FOR PRINTING

=cut

# ----- FORMAT PRINT DATA ----------------------------------------------

=pod

=item &FormatStudentInformation()

This function produces a formatted string of the student's information:
username, domain, section, full name, and PID.

=over 4

Input: $cache, $name, $studentInformation, $spacePadding

$cache: This is a pointer to a hash that is tied to the cached data

$name:  The name and domain of the current student in name:domain format

$studentInformation: A pointer to an array holding the names used to

remove data from the hash.  They represent the name of the data to be removed.

$spacePadding: Extra spaces that represent the space between columns

Output: $Str

$Str: Formatted string.

=back

=cut

sub FormatStudentInformation {
    my ($cache,$name,$studentInformation,$spacePadding)=@_;
    my $Str='';

    for(my $index=0; $index<(scalar @$studentInformation); $index++) {
        if(!&ShouldShowColumn($cache, 'heading'.$index)) {
            next;
        }
	my $data=$cache->{$name.':'.$studentInformation->[$index]};
	$Str .= $data;

	my @dataLength=split(//,$data);
	my $length=scalar @dataLength;
	$Str .= (' 'x($cache->{$studentInformation->[$index].'Length'}-
                      $length));
	$Str .= $spacePadding;
    }

    return $Str;
}

=pod

=item &FormatStudentData()

First, FormatStudentInformation is called and prefixes the course information.
This function produces a formatted string of the student's course information.
Each column of data represents all the problems for a given sequence.  For
valid grade data, a link is created for that problem to a submission record
for that problem.

=over 4

Input: $name, $studentInformation, $spacePadding, $ChartDB

$name: The name and domain of the current student in name:domain format

$studentInformation: A pointer to an array holding the names used to 
remove data from the hash.  They represent 
the name of the data to be removed.

$spacePadding: Extra spaces that represent the space between columns

$ChartDB: The name of the cached data database which will be tied to that 
database.

Output: $Str

$Str: Formatted string that is an entire row of the chart.  It is a 
concatenation of student information and student course information.

=back

=cut

sub FormatStudentData {
    my ($name,$studentInformation,$spacePadding,$ChartDB)=@_;
    my ($sname,$sdom) = split(/\:/,$name);
    my $Str;
    my %CacheData;

    unless(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_READER,0640)) {
        return '';
    }
    # Handle Student information ------------------------------------------
    # Handle user data
    $Str=&FormatStudentInformation(\%CacheData, $name, $studentInformation, 
                                   $spacePadding);

    # Handle errors
    if($CacheData{$name.':error'} =~ /environment/) {
        $Str .= '<br>';
        untie(%CacheData);
        return $Str;
    }

    if($CacheData{$name.':error'} =~ /course/) {
        $Str .= '<br>';
        untie(%CacheData);
        return $Str;
    }

    # Handle problem data ------------------------------------------------
    my $Version;
    my $problemsCorrect = 0;
    my $totalProblems   = 0;
    my $problemsSolved  = 0;
    my $numberOfParts   = 0;
    foreach my $sequence (split(/\:/,$CacheData{'orderedSequences'})) {
        if(!&ShouldShowColumn(\%CacheData, 'sequence'.$sequence)) {
            next;
        }

	my $characterCount=0;
	foreach my $problemID (split(/\:/,$CacheData{$sequence.':problems'})) {
	    my $problem = $CacheData{$problemID.':problem'};
	    my $LatestVersion = $CacheData{$name.":version:$problem"};

            # Output blanks for all the parts of this problem if there
            # is no version information about the current problem.
            if(!$LatestVersion) {
                foreach my $part (split(/\:/,$CacheData{$sequence.':'.
                                                        $problemID.
                                                        ':parts'})) {
                    $Str .= ' ';
                    $totalProblems++;
                    $characterCount++;
                }
                next;
            }

            my %partData=undef;
            # Initialize part data, display skips correctly
            # Skip refers to when a student made no submissions on that
            # part/problem.
            foreach my $part (split(/\:/,$CacheData{$sequence.':'.
                                                    $problemID.
                                                    ':parts'})) {
                $partData{$part.':tries'}=0;
                $partData{$part.':code'}=' ';
            }

            # Looping through all the versions of each part, starting with the
            # oldest version.  Basically, it gets the most recent 
            # set of grade data for each part.
	    for(my $Version=1; $Version<=$LatestVersion; $Version++) {
                foreach my $part (split(/\:/,$CacheData{$sequence.':'.
                                                        $problemID.
                                                        ':parts'})) {

                    if(!defined($CacheData{$name.":$Version:$problem".
                                               ":resource.$part.solved"})) {
                        # No grade for this submission, so skip
                        next;
                    }

                    my $tries=0;
                    my $code=' ';

                    $tries = $CacheData{$name.":$Version:$problem".
                                        ":resource.$part.tries"};
                    $partData{$part.':tries'}=($tries) ? $tries : 0;

                    my $val = $CacheData{$name.":$Version:$problem".
                                         ":resource.$part.solved"};
                    if    ($val eq 'correct_by_student')   {$code = '*';} 
                    elsif ($val eq 'correct_by_override')  {$code = '+';}
                    elsif ($val eq 'incorrect_attempted')  {$code = '.';} 
                    elsif ($val eq 'incorrect_by_override'){$code = '-';}
                    elsif ($val eq 'excused')              {$code = 'x';}
                    elsif ($val eq 'ungraded_attempted')   {$code = '#';}
                    else                                   {$code = ' ';}
                    $partData{$part.':code'}=$code;
                }
            }

            # All grades (except for versionless parts) are displayed as links
            # to their submission record.  Loop through all the parts for the
            # current problem in the correct order and prepare the output links
            $Str.='<a href="/adm/grades?symb='.
                &Apache::lonnet::escape($problem).
                '&student='.$sname.'&domain='.$sdom.'&command=submission">'; 
            foreach(split(/\:/,$CacheData{$sequence.':'.$problemID.
                                          ':parts'})) {
                if($partData{$_.':code'} eq '*') {
                    $problemsCorrect++;
                    if (($partData{$_.':tries'}<10) &&
                        ($partData{$_.':tries'} ne '')) {
                        $partData{$_.':code'}=$partData{$_.':tries'};
                    }
                } elsif($partData{$_.':code'} eq '+') {
                    $problemsCorrect++;
                }

                $Str .= $partData{$_.':code'};
                $characterCount++;

                if($partData{$_.':code'} ne 'x') {
                    $totalProblems++;
                }
            }
            $Str.='</a>';
        }

        # Output the number of correct answers for the current sequence.
        # This part takes up 6 character slots, but is formated right 
        # justified.
        my $spacesNeeded=$CacheData{$sequence.':columnWidth'}-$characterCount;
        $spacesNeeded -= 3;
        $Str .= (' 'x$spacesNeeded);

	my $outputProblemsCorrect = sprintf( "%3d", $problemsCorrect );
	$Str .= '<font color="#007700">'.$outputProblemsCorrect.'</font>';
	$problemsSolved += $problemsCorrect;
	$problemsCorrect=0;

        $Str .= $spacePadding;
    }

    # Output the total correct problems over the total number of problems.
    # I don't like this type of formatting, but it is a solution.  Need
    # a way to dynamically determine the space requirements.
    my $outputProblemsSolved = sprintf( "%4d", $problemsSolved );
    my $outputTotalProblems  = sprintf( "%4d", $totalProblems );
    $Str .= '<font color="#000088">'.$outputProblemsSolved.
	    ' / '.$outputTotalProblems.'</font><br>';

    untie(%CacheData);
    return $Str;
}

=pod

=item &CreateTableHeadings()

This function generates the column headings for the chart.

=over 4

Inputs: $CacheData, $studentInformation, $headings, $spacePadding

$CacheData: pointer to a hash tied to the cached data database

$studentInformation: a pointer to an array containing the names of the data 
held in a column and is used as part of a key into $CacheData

$headings: The names of the headings for the student information

$spacePadding: The spaces to go between columns

Output: $Str

$Str: A formatted string of the table column headings.

=back

=cut

sub CreateTableHeadings {
    my ($CacheData,$studentInformation,$headings,$spacePadding)=@_;
    my $Str='<tr>';

    for(my $index=0; $index<(scalar @$headings); $index++) {
        if(!&ShouldShowColumn($CacheData, 'heading'.$index)) {
            next;
        }

        $Str .= '<td align="left"><pre>';
	my $data=$$headings[$index];
	$Str .= $data;

	my @dataLength=split(//,$data);
	my $length=scalar @dataLength;
	$Str .= (' 'x($CacheData->{$$studentInformation[$index].'Length'}-
                      $length));
	$Str .= $spacePadding;
        $Str .= '</pre></td>';
    }

    foreach my $sequence (split(/\:/,$CacheData->{'orderedSequences'})) {
        if(!&ShouldShowColumn($CacheData, 'sequence'.$sequence)) {
            next;
        }

        $Str .= '<td align="left"><pre>';
        my $name = $CacheData->{$sequence.':title'};
	$Str .= $name;
	my @titleLength=split(//,$CacheData->{$sequence.':title'});
	my $leftover=$CacheData->{$sequence.':columnWidth'}-
                     (scalar @titleLength);
	$Str .= (' 'x$leftover);
	$Str .= $spacePadding;
        $Str .= '</pre></td>';
    }

    $Str .= '<td><pre>Total Solved/Total Problems</pre></td>';
    $Str .= '</tr>';

    return $Str;
}

=pod

=item &CreateColumnSelectionBox()

If there are columns not being displayed then this selection box is created
with a list of those columns.  When selections are made and the page 
refreshed, the columns will be removed from this box and the column is
put back in the chart.  If there is no columns to select, no row is added
to the interface table.

=over 4
Input: $CacheData, $headings


$CacheData: A pointer to a hash tied to the cached data

$headings:  An array of the names of the columns for the student information.  
They are used for displaying which columns are missing.

Output: $notThere

$notThere: The string contains one row of a table.  The first column has the 
name of the selection box.  The second contains the selection box 
which has a size of four.

=back

=cut

sub CreateColumnSelectionBox {
    my ($CacheData,$headings)=@_;

    my $missing=0;
    my $notThere='<tr><td align="right"><b>Select column to view:</b>';
    my $name;
    $notThere .= '<td align="left">';
    $notThere .= '<select name="reselect" size="4" multiple="true">'."\n";

    for(my $index=0; $index<(scalar @$headings); $index++) {
        if(&ShouldShowColumn($CacheData, 'heading'.$index)) {
            next;
        }
        $name = $headings->[$index];
        $notThere .= '<option value="heading'.$index.'">';
        $notThere .= $name.'</option>'."\n";
        $missing++;
    }

    foreach my $sequence (split(/\:/,$CacheData->{'orderedSequences'})) {
        if(&ShouldShowColumn($CacheData, 'sequence'.$sequence)) {
            next;
        }
        $name = $CacheData->{$sequence.':title'};
        $notThere .= '<option value="sequence'.$sequence.'">';
        $notThere .= $name.'</option>'."\n";
        $missing++;
    }

    if($missing) {
        $notThere .= '</select>';
    } else {
        $notThere='<tr><td>';
    }

    return $notThere.'</td></tr>';
}

=pod

=item &CreateColumnSelectors()

This function generates the checkboxes above the column headings.  The 
column will be removed if the checkbox is unchecked.

=over 4

Input: $CacheData, $headings

$CacheData: A pointer to a hash tied to the cached data

$headings:  An array of the names of the columns for the student 
information.  They are used to know what are the student information columns

Output: $present

$present: The string contains the first row of a table.  Each column contains
a checkbox which is left justified.  Currently left justification is used
for consistency of location over the column in which it presides.

=back

=cut

sub CreateColumnSelectors {
    my ($CacheData,$headings)=@_;

    my $found=0;
    my ($name, $length, $position);

    my $present = '<tr>';
    for(my $index=0; $index<(scalar @$headings); $index++) {
        if(!&ShouldShowColumn($CacheData, 'heading'.$index)) {
            next;
        }
        $present .= '<td align="left">';
        $present .= '<input type="checkbox" checked="on" ';
        $present .= 'name="heading'.$index.'" />';
        $present .= '</td>';
        $found++;
    }

    foreach my $sequence (split(/\:/,$CacheData->{'orderedSequences'})) {
        if(!&ShouldShowColumn($CacheData, 'sequence'.$sequence)) {
            next;
        }
        $present .= '<td align="left">';
        $present .= '<input type="checkbox" checked="on" ';
        $present .= 'name="sequence'.$sequence.'" />';
        $present .= '</td>';
        $found++;
    }

    if(!$found) {
        $present = '';
    }

    return $present.'<td></td></tr></form>'."\n";;
}

=pod

=item &CreateForm()

The interface for this module consists primarily of the controls in this
function.  The student status selection (active, expired, any) is set here.
The sort buttons: username, last name, and section are set here.  The
other buttons are Recalculate Chart, Refresh Chart, and Reset Selections.
These controls are in a table to clean up the interface.

=over 4

Input: $CacheData

$CacheData is a hash pointer to tied database for cached data.

Output: $Ptr

$Ptr is a string containing all the html for the above mentioned buttons.

=back

=cut

sub CreateForm {
    my ($CacheData)=@_;
    my $OpSel1='';
    my $OpSel2='';
    my $OpSel3='';
    my $Status = $CacheData->{'form.status'};
    if ( $Status eq 'Any' ) { $OpSel3='selected'; }
    elsif ($Status eq 'Expired' ) { $OpSel2 = 'selected'; }
    else { $OpSel1 = 'selected'; }

    my $Ptr .= '<form name="stat" method="post" action="/adm/chart" >'."\n";
    $Ptr .= '<tr><td align="right">';
    $Ptr .= '</td><td align="left">';
    $Ptr .= '<input type="submit" name="recalculate" ';
    $Ptr .= 'value="Recalculate Chart"/>'."\n";
    $Ptr .= '&nbsp;&nbsp;&nbsp;';
    $Ptr .= '<input type="submit" name="refresh" ';
    $Ptr .= 'value="Refresh Chart"/>'."\n";
    $Ptr .= '&nbsp;&nbsp;&nbsp;';
    $Ptr .= '<input type="submit" name="reset" ';
    $Ptr .= 'value="Reset Selections"/></td>'."\n";
    $Ptr .= '</tr><tr><td align="right">';
    $Ptr .= '<b> Sort by: </b>'."\n";
    $Ptr .= '</td><td align="left">';
    $Ptr .= '<input type="submit" name="sort" value="User Name" />'."\n";
    $Ptr .= '&nbsp;&nbsp;&nbsp;';
    $Ptr .= '<input type="submit" name="sort" value="Last Name" />'."\n";
    $Ptr .= '&nbsp;&nbsp;&nbsp;';
    $Ptr .= '<input type="submit" name="sort" value="Section"/>'."\n";
    $Ptr .= '</td></tr><tr><td align="right">';
    $Ptr .= '<b> Student Status: &nbsp; </b>'."\n".
            '</td><td align="left">'.
            '<select name="status">'. 
            '<option '.$OpSel1.' >Active</option>'."\n".
            '<option '.$OpSel2.' >Expired</option>'."\n".
	    '<option '.$OpSel3.' >Any</option> </select> '."\n";
    $Ptr .= '</td></tr>';

    return $Ptr;
}

=pod

=item &CreateLegend()

This function returns a formatted string containing the legend for the
chart.  The legend describes the symbols used to represent grades for
problems.

=cut

sub CreateLegend {
    my $Str = "<p><pre>".
              "1..9: correct by student in 1..9 tries\n".
              "   *: correct by student in more than 9 tries\n".
	      "   +: correct by override\n".
              "   -: incorrect by override\n".
	      "   .: incorrect attempted\n".
	      "   #: ungraded attempted\n".
              "    : not attempted\n".
	      "   x: excused".
              "</pre><p>"; 
    return $Str;
}

=pod

=item &StartDocument()

Returns a string containing the header information for the chart: title,
logo, and course title.

=cut

sub StartDocument {
    my $Str = '';
    $Str .= '<html>';
    $Str .= '<head><title>';
    $Str .= 'LON-CAPA Assessment Chart</title></head>';
    $Str .= '<body bgcolor="#FFFFFF">';
    $Str .= '<script>window.focus();</script>';
    $Str .= '<img align=right src=/adm/lonIcons/lonlogos.gif>';
    $Str .= '<h1>Assessment Chart</h1>';
    $Str .= '<h1>'.$ENV{'course.'.$ENV{'request.course.id'}.'.description'};
    $Str .= '</h1>';

    return $Str;
}

# ----- END FORMAT PRINT DATA ------------------------------------------

=pod

=head1 DOWNLOAD INFORMATION

This section contains all the files that get data from other servers 
and/or itself.  There is one function that has a call to get remote
information but isn't included here which is ProcessTopLevelMap.  The
usage was small enough to be ignored, but that portion may be moved
here in the future.

=cut

# ----- DOWNLOAD INFORMATION -------------------------------------------

=pod

=item &DownloadPrerequisiteData()

Collects lastname, generation, middlename, firstname, PID, and section for each
student from their environment database.  The list of students is built from
collecting a classlist for the course that is to be displayed.

=over 4

Input: $courseID, $c

$courseID:  The id of the course

$c: The connection class that can determine if the browser has aborted.  It
is used to short circuit this function so that it doesn't continue to 
get information when there is no need.

Output: \%classlist

\%classlist: A pointer to a hash containing the following data:

-A list of student name:domain (as keys) (known below as $name)

-A hash pointer for each student containing lastname, generation, firstname,
middlename, and PID : Key is $name.'studentInformation'

-A hash pointer to each students section data : Key is $name.section

=back

=cut

sub DownloadPrerequisiteData {
    my ($courseID, $c)=@_;
    my ($courseDomain,$courseNumber)=split(/\_/,$courseID);

    my %classlist=&Apache::lonnet::dump('classlist',$courseDomain,
                                        $courseNumber);
    my ($checkForError)=keys (%classlist);
    if($checkForError =~ /^(con_lost|error|no_such_host)/i) {
        return \%classlist;
    }

    foreach my $name (keys(%classlist)) {
        if($c->aborted()) {
            $classlist{'error'}='aborted';
            return \%classlist;
        }

        my ($studentName,$studentDomain) = split(/\:/,$name);
        # Download student environment data, specifically the full name and id.
        my %studentInformation=&Apache::lonnet::get('environment',
                                                    ['lastname','generation',
                                                     'firstname','middlename',
                                                     'id'],
                                                    $studentDomain,
                                                    $studentName);
        $classlist{$name.':studentInformation'}=\%studentInformation;

        if($c->aborted()) {
            $classlist{'error'}='aborted';
            return \%classlist;
        }

        #Section
        my %section=&Apache::lonnet::dump('roles',$studentDomain,$studentName);
        $classlist{$name.':section'}=\%section;
    }

    return \%classlist;
}

=pod

=item &DownloadStudentCourseInformation()

Dump of all the course information for a single student.  There is no
pruning of data, it is all stored in a hash and returned.

=over 4

Input: $name, $courseID

$name: student name:domain

$courseID:  The id of the course

Output: \%courseData

\%courseData:  A hash pointer to the raw data from the student's course
database.

=back

=cut

sub DownloadStudentCourseInformation {
    my ($name,$courseID)=@_;
    my ($studentName,$studentDomain) = split(/\:/,$name);

    # Download student course data
    my %courseData=&Apache::lonnet::dump($courseID,$studentDomain,
					 $studentName);
    return \%courseData;
}

# ----- END DOWNLOAD INFORMATION ---------------------------------------

=pod

=head1 PROCESSING FUNCTIONS

These functions process all the data for all the students.  Also, they
are the only functions that access the cache database for writing.  Thus
they are the only functions that cache data.  The downloading and caching
were separated to reduce problems with stopping downloading then can't
tie hash to database later.

=cut

# ----- PROCESSING FUNCTIONS ---------------------------------------

=pod

=item &ProcessTopResourceMap()

Trace through the "big hash" created in rat/lonuserstate.pm::loadmap.  
Basically, this function organizes a subset of the data and stores it in
cached data.  The data stored is the problems, sequences, sequence titles,
parts of problems, and their ordering.  Column width information is also 
partially handled here on a per sequence basis.

=over 4

Input: $ChartDB, $c

$ChartDB:  The name of the cache database file

$c:  The connection class used to determine if an abort has been sent to the 
browser

Output: A string that contains an error message or "OK" if everything went 
smoothly.

=back

=cut

sub ProcessTopResourceMap {
    my ($ChartDB,$c)=@_;
    my %hash;
    my $fn=$ENV{'request.course.fn'};
    if(-e "$fn.db") {
	my $tieTries=0;
	while($tieTries < 3) {
	    if(tie(%hash,'GDBM_File',"$fn.db",&GDBM_READER,0640)) {
		last;
	    }
	    $tieTries++;
	    sleep 1;
	}
	if($tieTries >= 3) {
            return 'Coursemap undefined.';
        }
    } else {
        return 'Can not open Coursemap.';
    }

    my %CacheData;
    unless(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_WRCREAT,0640)) {
        untie(%hash);
	return 'Could not tie cache hash.';
    }

    # Initialize state machine.  Set information pointing to top level map.
    my (@sequences, @currentResource, @finishResource);
    my ($currentSequence, $currentResourceID, $lastResourceID);

    $currentResourceID=$hash{'ids_/res/'.$ENV{'request.course.uri'}};
    push(@currentResource, $currentResourceID);
    $lastResourceID=-1;
    $currentSequence=-1;
    my $topLevelSequenceNumber = $currentSequence;

    while(1) {
        if($c->aborted()) {
            last;
        }
	# HANDLE NEW SEQUENCE!
	#if page || sequence
	if(defined($hash{'map_pc_'.$hash{'src_'.$currentResourceID}})) {
	    push(@sequences, $currentSequence);
	    push(@currentResource, $currentResourceID);
	    push(@finishResource, $lastResourceID);

	    $currentSequence=$hash{'map_pc_'.$hash{'src_'.$currentResourceID}};

            # Mark sequence as containing problems.  If it doesn't, then
            # it will be removed when processing for this sequence is
            # complete.  This allows the problems in a sequence
            # to be outputed before problems in the subsequences
            if(!defined($CacheData{'orderedSequences'})) {
                $CacheData{'orderedSequences'}=$currentSequence;
            } else {
                $CacheData{'orderedSequences'}.=':'.$currentSequence;
            }

	    $lastResourceID=$hash{'map_finish_'.
				  $hash{'src_'.$currentResourceID}};
	    $currentResourceID=$hash{'map_start_'.
				     $hash{'src_'.$currentResourceID}};

	    if(!($currentResourceID) || !($lastResourceID)) {
		$currentSequence=pop(@sequences);
		$currentResourceID=pop(@currentResource);
		$lastResourceID=pop(@finishResource);
		if($currentSequence eq $topLevelSequenceNumber) {
		    last;
		}
	    }
	}

	# Handle gradable resources: exams, problems, etc
	$currentResourceID=~/(\d+)\.(\d+)/;
        my $partA=$1;
        my $partB=$2;
	if($hash{'src_'.$currentResourceID}=~
	   /\.(problem|exam|quiz|assess|survey|form)$/ &&
	   $partA eq $currentSequence) {
	    my $Problem = &Apache::lonnet::symbclean(
			  &Apache::lonnet::declutter($hash{'map_id_'.$partA}).
			  '___'.$partB.'___'.
			  &Apache::lonnet::declutter($hash{'src_'.
							 $currentResourceID}));

	    $CacheData{$currentResourceID.':problem'}=$Problem;
	    if(!defined($CacheData{$currentSequence.':problems'})) {
		$CacheData{$currentSequence.':problems'}=$currentResourceID;
	    } else {
		$CacheData{$currentSequence.':problems'}.=
		    ':'.$currentResourceID;
	    }

            # Get Parts for problem
	    my $meta=$hash{'src_'.$currentResourceID};
	    foreach (split(/\,/,&Apache::lonnet::metadata($meta,'keys'))) {
		if($_=~/^stores\_(\d+)\_tries$/) {
		    my $Part=&Apache::lonnet::metadata($meta,$_.'.part');
                    if(!defined($CacheData{$currentSequence.':'.
                                          $currentResourceID.':parts'})) {
                        $CacheData{$currentSequence.':'.$currentResourceID.
                                   ':parts'}=$Part;
                    } else {
                        $CacheData{$currentSequence.':'.$currentResourceID.
                                   ':parts'}.=':'.$Part;
                    }
		}
	    }
	}

	# if resource == finish resource, then it is the end of a sequence/page
	if($currentResourceID eq $lastResourceID) {
	    # pop off last resource of sequence
	    $currentResourceID=pop(@currentResource);
	    $lastResourceID=pop(@finishResource);

	    if(defined($CacheData{$currentSequence.':problems'})) {
		# Capture sequence information here
		$CacheData{$currentSequence.':title'}=
		    $hash{'title_'.$currentResourceID};

                my $totalProblems=0;
                foreach my $currentProblem (split(/\:/,
                                               $CacheData{$currentSequence.
                                               ':problems'})) {
                    foreach (split(/\:/,$CacheData{$currentSequence.':'.
                                                   $currentProblem.
                                                   ':parts'})) {
                        $totalProblems++;
                    }
                }
		my @titleLength=split(//,$CacheData{$currentSequence.
                                                    ':title'});
                # $extra is 3 for problems correct and 3 for space
                # between problems correct and problem output
                my $extra = 6;
		if(($totalProblems + $extra) > (scalar @titleLength)) {
		    $CacheData{$currentSequence.':columnWidth'}=
                        $totalProblems + $extra;
		} else {
		    $CacheData{$currentSequence.':columnWidth'}=
                        (scalar @titleLength);
		}
	    } else {
                # Remove sequence from list, if it contains no problems to
                # display.
                $CacheData{'orderedSequences'}=~s/$currentSequence//;
                $CacheData{'orderedSequences'}=~s/::/:/g;
                $CacheData{'orderedSequences'}=~s/^:|:$//g;
            }

	    $currentSequence=pop(@sequences);
	    if($currentSequence eq $topLevelSequenceNumber) {
		last;
	    }
	}

	# MOVE!!!
	# move to next resource
	unless(defined($hash{'to_'.$currentResourceID})) {
	    # big problem, need to handle.  Next is probably wrong
	    last;
	}
	my @nextResources=();
	foreach (split(/\,/,$hash{'to_'.$currentResourceID})) {
	    push(@nextResources, $hash{'goesto_'.$_});
	}
	push(@currentResource, @nextResources);
	# Set the next resource to be processed
	$currentResourceID=pop(@currentResource);
    }

    unless (untie(%hash)) {
        &Apache::lonnet::logthis("<font color=blue>WARNING: ".
                                 "Could not untie coursemap $fn (browse)".
                                 ".</font>"); 
    }

    unless (untie(%CacheData)) {
        &Apache::lonnet::logthis("<font color=blue>WARNING: ".
                                 "Could not untie Cache Hash (browse)".
                                 ".</font>"); 
    }

    return 'OK';
}

=pod

=item &ProcessSection()

Determine the section number for a student for the class.  A student can have 
multiple sections for the same class.  The correct one is chosen.

=over 4

Input: $sectionData, $courseid, $ActiveFlag

$sectionData:  A pointer to a hash containing all section data for this 
student for the class

$courseid:  The course ID.

$ActiveFlag:  The student's active status (Active/Expired)

Output: $oldsection, $cursection, or -1

$oldsection and $cursection and sections number that will be displayed in the 
chart.

-1 is returned if an error occurs.

=back

=cut

sub ProcessSection {
    my ($sectionData, $courseid,$ActiveFlag)=@_;
    $courseid=~s/\_/\//g;
    $courseid=~s/^(\w)/\/$1/;

    my $cursection='-1';
    my $oldsection='-1';
    my $status='Expired';
    my $section='';
    foreach my $key (keys (%$sectionData)) {
	my $value = $sectionData->{$key};
        if ($key=~/^$courseid(?:\/)*(\w+)*\_st$/) {
	    $section=$1;
	    if($key eq $courseid.'_st') {
		$section='';
	    }
	    my ($dummy,$end,$start)=split(/\_/,$value);
	    my $now=time;
	    my $notactive=0;
	    if ($start) {
		if($now<$start) {
		    $notactive=1;
		}
	    }
	    if($end) {
		if ($now>$end) {
		    $notactive=1;
		}
	    }
	    if($notactive == 0) {
		$status='Active';
		$cursection=$section;
		last;
	    }
	    if($notactive == 1) {
		$oldsection=$section;
	    }
	}
    }
    if($status eq $ActiveFlag) {
	if($cursection eq '-1') {
	    return $oldsection;
	}
	return $cursection;
    }
    if($ActiveFlag eq 'Any') {
	if($cursection eq '-1') {
	    return $oldsection;
	}
	return $cursection;
    }
    return '-1';
}

=pod

=item &ProcessStudentInformation()

Takes data downloaded for a student and breaks it up into managable pieces and 
stored in cache data.  The username, domain, class related date, PID, 
full name, and section are all processed here.

=over 4

Input: $CacheData, $studentInformation, $section, $date, $name, $courseID

$CacheData:  A hash pointer to the cached data

$studentInformation:  Student information is what was requested in 
&DownloadPrerequistedData().  See that function for what data is requested.

$section: A hash pointer to class section related information.

$date:  A composite of the start and end date for this class for this
student.  Format:  end:start

$name:  the username:domain information

$courseID: The course ID

Output: None

*NOTE:  There is no return value, but if an error occurs a key is added to 
the cache data with the value being the error message.  The key is 
username:domain:error.  It will only exist if an error occurs.

=back

=cut

sub ProcessStudentInformation {
    my ($CacheData,$studentInformation,$section,$date,$name,$courseID)=@_;
    my ($studentName,$studentDomain) = split(/\:/,$name);

    $CacheData->{$name.':username'}=$studentName;
    $CacheData->{$name.':domain'}=$studentDomain;
    $CacheData->{$name.':date'}=$date;

    my ($checkForError)=keys(%$studentInformation);
    if($checkForError =~ /^(con_lost|error|no_such_host)/i) {
	$CacheData->{$name.':error'}=
	    'Could not download student environment data.';
	$CacheData->{$name.':fullname'}='';
	$CacheData->{$name.':id'}='';
    } else {
	$CacheData->{$name.':fullname'}=&ProcessFullName(
                                          $studentInformation->{'lastname'},
				          $studentInformation->{'generation'},
				          $studentInformation->{'firstname'},
                                          $studentInformation->{'middlename'});
	$CacheData->{$name.':id'}=$studentInformation->{'id'};
    }

    # Get student's section number
    my $sec=&ProcessSection($section, $courseID, $CacheData->{'form.status'});
    if($sec != -1) {
	$CacheData->{$name.':section'}=$sec;
    } else {
	$CacheData->{$name.':section'}='';
    }

    return;
}

=pod

=item &ProcessClassList()

Taking the class list dumped from &DownloadPrerequisiteData(), all the 
students and their non-class information is processed using the 
&ProcessStudentInformation() function.  A date stamp is also recorded for
when the data was processed.

=over 4

Input: $classlist, $courseID, $ChartDB, $c

$classlist:  The hash of data collected about a student from 
&DownloadPrerequisteData().  The hash contains a list of students, a pointer 
to a hash of student information for each student, and each student's section 
number.

$courseID:  The course ID

$ChartDB:  The name of the cache database file.

$c:  The connection class used to determine if an abort has been sent to the 
browser

Output: @names

@names:  An array of students whose information has been processed, and are to 
be considered in an arbitrary order.

=back

=cut

sub ProcessClassList {
    my ($classlist,$courseID,$ChartDB,$c)=@_;
    my @names=();

    my %CacheData;
    if(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_WRCREAT,0640)) {
        foreach my $name (keys(%$classlist)) {
            if($name =~ /\:section/ || $name =~ /\:studentInformation/ ||
               $name eq '') {
                next;
            }
            if($c->aborted()) {
                last;
            }
            push(@names,$name);
            &ProcessStudentInformation(
                                    \%CacheData,
                                    $classlist->{$name.':studentInformation'},
                                    $classlist->{$name.':section'},
                                    $classlist->{$name},
                                    $name,$courseID);
        }

        # Time of download
        $CacheData{'time'}=localtime();
	untie(%CacheData);
    }

    return @names;
}

=pod

=item &ProcessStudentData()

Takes the course data downloaded for a student in 
&DownloadStudentCourseInformation() and breaks it up into key value pairs
to be stored in the cached data.  The keys are comprised of the 
$username:$domain:$keyFromCourseDatabase.  The student username:domain is
stored away signifying that the student's information has been downloaded and 
can be reused from cached data.

=over 4

Input: $courseData, $name, $ChartDB

$courseData:  A hash pointer that points to the course data downloaded for a 
student.

$name:  username:domain

$ChartDB:  The name of the cache database file which will allow the data to
be written to the cache.

Output: None

*NOTE:  There is no output, but an error message is stored away in the cache 
data.  This is checked in &FormatStudentData().  The key username:domain:error 
will only exist if an error occured.  The error is an error from 
&DownloadStudentCourseInformation().

=back

=cut

sub ProcessStudentData {
    my ($courseData, $name, $ChartDB)=@_;

    my %CacheData;
    if(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_WRCREAT,0640)) {
        my ($checkForError) = keys(%$courseData);
        if($checkForError =~ /^(con_lost|error|no_such_host)/i) {
            $CacheData{$name.':error'}='Could not download course data.';
        } else {
            foreach my $key (keys (%$courseData)) {
                $CacheData{$name.':'.$key}=$courseData->{$key};
            }
            if(defined($CacheData{'NamesOfStudents'})) {
                $CacheData{'NamesOfStudents'}.=':::'.$name;
            } else {
                $CacheData{'NamesOfStudents'}=$name;
            }
        }
        untie(%CacheData);
    }

    return;
}

=pod

=item &ProcessFormData()

Cache form data and set default form data (sort, status, heading.$number,
sequence.$number, reselect, reset, recalculate, and refresh)

=over 4

Input: $ChartDB, $isCached

$ChartDB: The name of the database for cached data

$isCached: Is there already data for this course cached.  This is used in 
conjunction with the absence of all form data to know to display all selection 
types.

Output: None

=back

=cut

# For all data, if ENV data doesn't exist for it, default values is used.
sub ProcessFormData {
    my ($ChartDB, $isCached)=@_;
    my %CacheData;

    if(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_WRCREAT,0640)) {
        # Ignore $ENV{'form.refresh'}
        # Ignore $ENV{'form.recalculate'}

        if(defined($ENV{'form.sort'})) {
            $CacheData{'form.sort'}=$ENV{'form.sort'};
        } elsif(!defined($CacheData{'form.sort'})) {
            $CacheData{'form.sort'}='username';
        }

        if(defined($ENV{'form.status'})) {
            $CacheData{'form.status'}=$ENV{'form.status'};
        } elsif(!defined($CacheData{'form.status'})) {
            $CacheData{'form.status'}='Active';
        }

        # $found checks for any instances of form data in the ENV.  If it is
        # missing I assume the chrt button on the remote has been pressed.
        my @headings=();
        my @sequences=();
        my $found=0;
        foreach (keys(%ENV)) {
            if(/form\.heading/) {
                $found++;
                push(@headings, $_);
            } elsif(/form\.sequence/) {
                $found++;
                push(@sequences, $_);
            } elsif(/form\./) {
                $found++;
            }
        }

        if($found) {
            $CacheData{'form.headings'}=join(":::",@headings);
            $CacheData{'form.sequences'}=join(":::",@sequences);
        }

        if(defined($ENV{'form.reselect'})) {
            my @reselected = (ref($ENV{'form.reselect'}) ? 
                              @{$ENV{'form.reselect'}}
                              : ($ENV{'form.reselect'}));
            foreach (@reselected) {
                if(/heading/) {
                    $CacheData{'form.headings'}.=":::".$_;
                } elsif(/sequence/) {
                    $CacheData{'form.sequences'}.=":::".$_;
                }
            }
        }

        # !$found and !$isCached are how I determine if the chrt button
        # on the remote was pressed and needs to reset all the selections
        if(defined($ENV{'form.reset'}) || (!$found && !$isCached)) {
            $CacheData{'form.reset'}='true';
            $CacheData{'form.status'}='Active';
            $CacheData{'form.sort'}='username';
            $CacheData{'form.headings'}='ALLHEADINGS';
            $CacheData{'form.sequences'}='ALLSEQUENCES';
        } else {
            $CacheData{'form.reset'}='false';
        }

        untie(%CacheData);
    }

    return;
}

=pod

=item &SpaceColumns()

Determines the width of all the columns in the chart.  It is based on
the max of the data for that column and its header.

=over 4

Input: $students, $studentInformation, $headings, $ChartDB

$students: An array pointer to a list of students (username:domain)

$studentInformatin: The type of data for the student information.  It is
used as part of the key in $CacheData.

$headings: The name of the student information columns.

$ChartDB: The name of the cache database which is opened for read/write.

Output: None - All data stored in cache.

=back

=cut

sub SpaceColumns {
    my ($students,$studentInformation,$headings,$ChartDB)=@_;

    my %CacheData;
    if(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_WRCREAT,0640)) {
        # Initialize Lengths
        for(my $index=0; $index<(scalar @$headings); $index++) {
	    my @titleLength=split(//,$$headings[$index]);
	    $CacheData{$$studentInformation[$index].'Length'}=
                scalar @titleLength;
	}

        foreach my $name (@$students) {
            foreach (@$studentInformation) {
		my @dataLength=split(//,$CacheData{$name.':'.$_});
		my $length=scalar @dataLength;
		if($length > $CacheData{$_.'Length'}) {
		    $CacheData{$_.'Length'}=$length;
		}
            }
        }
        untie(%CacheData);
    }

    return;
}

# ----- END PROCESSING FUNCTIONS ---------------------------------------

=pod

=head1 HELPER FUNCTIONS

These are just a couple of functions do various odd and end 
jobs.

=cut

# ----- HELPER FUNCTIONS -----------------------------------------------

=pod

=item &ProcessFullName()

Takes lastname, generation, firstname, and middlename (or some partial
set of this data) and returns the full name version as a string.  Format
is Lastname generation, firstname middlename or a subset of this.

=cut

sub ProcessFullName {
    my ($lastname, $generation, $firstname, $middlename)=@_;
    my $Str = '';

    if($lastname ne '') {
	$Str .= $lastname.' ';
	if($generation ne '') {
	    $Str .= $generation;
	} else {
	    chop($Str);
	}
	$Str .= ', ';
	if($firstname ne '') {
	    $Str .= $firstname.' ';
	}
	if($middlename ne '') {
	    $Str .= $middlename;
	} else {
	    chop($Str);
	    if($firstname eq '') {
		chop($Str);
	    }
	}
    } else {
	if($firstname ne '') {
	    $Str .= $firstname.' ';
	}
	if($middlename ne '') {
	    $Str .= $middlename.' ';
	}
	if($generation ne '') {
	    $Str .= $generation;
	} else {
	    chop($Str);
	}
    }

    return $Str;
}

=pod

=item &SortStudents()

Determines which students to display and in which order.  Which are 
displayed are determined by their status(active/expired).  The order
is determined by the sort button pressed (default to username).  The
type of sorting is username, lastname, or section.

=over 4

Input: $students, $CacheData

$students: A array pointer to a list of students (username:domain)

$CacheData: A pointer to the hash tied to the cached data

Output: @order

@order: An ordered list of students (username:domain)

=back

=cut

sub SortStudents {
    my ($students,$CacheData)=@_;

    my @sorted1Students=();
    foreach (@$students) {
        my ($end,$start)=split(/\:/,$CacheData->{$_.':date'});
        my $active=1;
        my $now=time;
        my $Status=$CacheData->{'form.status'};
        $Status = ($Status) ? $Status : 'Active';
        if((($end) && $now > $end) && (($Status eq 'Active'))) { 
            $active=0; 
        }
        if(($Status eq 'Expired') && ($end == 0 || $now < $end)) {
            $active=0;
        }
        if($active) {
            push(@sorted1Students, $_);
        }
    }

    my $Pos = $CacheData->{'form.sort'};
    my %sortData;
    if($Pos eq 'Last Name') {
	for(my $index=0; $index<scalar @sorted1Students; $index++) {
	    $sortData{$CacheData->{$sorted1Students[$index].':fullname'}}=
		$sorted1Students[$index];
	}
    } elsif($Pos eq 'Section') {
	for(my $index=0; $index<scalar @sorted1Students; $index++) {
	    $sortData{$CacheData->{$sorted1Students[$index].':section'}.
		      $sorted1Students[$index]}=$sorted1Students[$index];
	}
    } else {
	# Sort by user name
	for(my $index=0; $index<scalar @sorted1Students; $index++) {
	    $sortData{$sorted1Students[$index]}=$sorted1Students[$index];
	}
    }

    my @order = ();
    foreach my $key (sort(keys(%sortData))) {
	push (@order,$sortData{$key});
    }

    return @order;
}

=pod

=item &TestCacheData()

Determine if the cache database can be accessed with a tie.  It waits up to
ten seconds before returning failure.  This function exists to help with
the problems with stopping the data download.  When an abort occurs and the
user quickly presses a form button and httpd child is created.  This
child needs to wait for the other to finish (hopefully within ten seconds).

=over 4

Input: $ChartDB

$ChartDB: The name of the cache database to be opened

Output: -1, 0, 1

-1: Couldn't tie database
 0: Use cached data
 1: New cache database created, use that.

=back

=cut

sub TestCacheData {
    my ($ChartDB)=@_;
    my $isCached=-1;
    my %testData;
    my $tieTries=0;

    if ((-e "$ChartDB") && (!defined($ENV{'form.recalculate'}))) {
	$isCached = 1;
    } else {
	$isCached = 0;
    }

    while($tieTries < 10) {
        my $result=0;
        if($isCached) {
            $result=tie(%testData,'GDBM_File',$ChartDB,&GDBM_READER,0640);
        } else {
            $result=tie(%testData,'GDBM_File',$ChartDB,&GDBM_NEWDB,0640);
        }
        if($result) {
            last;
        }
        $tieTries++;
        sleep 1;
    }
    if($tieTries >= 10) {
        return -1;
    }

    untie(%testData);

    return $isCached;
}

=pod

=item &ShouldShowColumn()

Determine if a specified column should be shown on the chart.

=over 4

Input: $cache, $test

$cache: A pointer to the hash tied to the cached data

$test: The form name of the column (heading.$headingIndex) or 
(sequence.$sequenceIndex)

Output: 0 (false), 1 (true)

=back

=cut

sub ShouldShowColumn {
    my ($cache,$test)=@_;

    if($cache->{'form.reset'} eq 'true') {
        return 1;
    }

    my $headings=$cache->{'form.headings'};
    my $sequences=$cache->{'form.sequences'};
    if($headings eq 'ALLHEADINGS' || $sequences eq 'ALLSEQUENCES' ||
       $headings=~/$test/ || $sequences=~/$test/) {
        return 1;
    }

    return 0;
}

# ----- END HELPER FUNCTIONS --------------------------------------------

=pod

=head1 Handler and main function(BuildChart)

The handler does some initial error checking and then passes the torch to
BuildChart.  BuildChart calls all the appropriate functions to get the
job done.  These are the only two functions that use print ($r).  All other
functions return strings to BuildChart to be printed.

=cut

=pod

=item &BuildChart()

 The following is the process that BuildChart goes through to 
  create the html document.

 -Start the lonchart document
 -Test for access to the CacheData
 -Download class list information if not using cached data 
 -Sort students and print out table desciptive data
 -Output student data
 -If recalculating, store a list of students, but only if all 
  their data was downloaded.  Leave off the others.
 -End document

=over 4

Input: $r

$r:  Used to print html

Output: None

=back

=cut

sub BuildChart {
    my ($r)=@_;
    my $c = $r->connection;

    # Start the lonchart document
    $r->content_type('text/html');
    $r->send_http_header;
    $r->print(&StartDocument());
    $r->rflush();

    # Test for access to the CacheData
    my $isCached=0;
    my $cid=$ENV{'request.course.id'};
    my $ChartDB = "/home/httpd/perl/tmp/$ENV{'user.name'}".
                  "_$ENV{'user.domain'}_$cid\_chart.db";

    $isCached=&TestCacheData($ChartDB);
    if($isCached < 0) {
        $r->print("Unable to tie hash to db file");
        $r->rflush();
        return;
    }
    &ProcessFormData($ChartDB, $isCached);

    # Download class list information if not using cached data
    my %CacheData;
    my @students=();
    my @studentInformation=('username','domain','section','id','fullname');
    my @headings=('User Name','Domain','Section','PID','Full Name');
    my $spacePadding='   ';
    if(!$isCached) {
        my $processTopResourceMapReturn=&ProcessTopResourceMap($ChartDB,$c);
        if($processTopResourceMapReturn ne 'OK') {
            $r->print($processTopResourceMapReturn);
            return;
        }
        if($c->aborted()) { return; }
        my $classlist=&DownloadPrerequisiteData($cid, $c);
        my ($checkForError)=keys(%$classlist);
        if($checkForError =~ /^(con_lost|error|no_such_host)/i ||
           defined($classlist->{'error'})) {
            return;
        }
        if($c->aborted()) { return; }
        @students=&ProcessClassList($classlist,$cid,$ChartDB,$c);
        if($c->aborted()) { return; }
        &SpaceColumns(\@students,\@studentInformation,\@headings,
                      $ChartDB);
        if($c->aborted()) { return; }
    } else {
        if(!$c->aborted() && tie(%CacheData,'GDBM_File',$ChartDB,
                                 &GDBM_READER,0640)) {
            @students=split(/:::/,$CacheData{'NamesOfStudents'});
        }
    }

    # Sort students and print out table desciptive data
    my $downloadTime=0;
    if(tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_READER,0640)) {
        if(!$c->aborted()) { @students=&SortStudents(\@students,\%CacheData); }
        if(defined($CacheData{'time'})) { $downloadTime=$CacheData{'time'}; }
        else { $downloadTime=localtime(); }
        if(!$c->aborted()) { $r->print('<h3>'.$downloadTime.'</h3>'); }
        if(!$c->aborted()) { $r->print('<h1>'.(scalar @students).
                                       ' students</h1>'); }
	if(!$c->aborted()) { $r->rflush(); }
	if(!$c->aborted()) { $r->print(&CreateLegend()); }
        if(!$c->aborted()) { $r->print('<table border="0"><tbody>'); }
	if(!$c->aborted()) { $r->print(&CreateForm(\%CacheData)); }
	if(!$c->aborted()) { $r->print(&CreateColumnSelectionBox(
                                                       \%CacheData,
                                                       \@headings)); }
        if(!$c->aborted()) { $r->print('</tbody></table>'); }
        if(!$c->aborted()) { $r->print('<b>Note: Uncheck the boxes above a'); }
        if(!$c->aborted()) { $r->print(' column to remove that column from'); }
        if(!$c->aborted()) { $r->print(' the display.</b></pre>'); }
        if(!$c->aborted()) { $r->print('<table border="0" cellpadding="0" '); }
        if(!$c->aborted()) { $r->print('cellspacing="0"><tbody>'); }
	if(!$c->aborted()) { $r->print(&CreateColumnSelectors(
                                                       \%CacheData,
                                                       \@headings)); }
	if(!$c->aborted()) { $r->print(&CreateTableHeadings(
                                                         \%CacheData,
                                                         \@studentInformation, 
							 \@headings, 
							 $spacePadding)); }
        if(!$c->aborted()) { $r->print('</tbody></table>'); }
	if(!$c->aborted()) { $r->rflush(); }
	untie(%CacheData);
    } else {
	$r->print("Init2: Unable to tie hash to db file");
	return;
    }

    # Output student data
    my @updateStudentList = ();
    my $courseData;
    $r->print('<pre>');
    foreach (@students) {
        if($c->aborted()) {
            last;
        }

        if(!$isCached) {
            $courseData=&DownloadStudentCourseInformation($_, $cid);
            if($c->aborted()) { last; }
            push(@updateStudentList, $_);
            &ProcessStudentData($courseData, $_, $ChartDB);
        }
        $r->print(&FormatStudentData($_, \@studentInformation,
                                     $spacePadding, $ChartDB));
        $r->rflush();
    }

    # If recalculating, store a list of students, but only if all their 
    # data was downloaded.  Leave off the others.
    if(!$isCached && tie(%CacheData,'GDBM_File',$ChartDB,&GDBM_WRCREAT,0640)) {
        $CacheData{'NamesOfStudents'}=join(":::", @updateStudentList);
#		    $CacheData{'NamesOfStudents'}=
#		            &Apache::lonnet::arrayref2str(\@updateStudentList);
        untie(%CacheData);
    }

    # End document
    $r->print('</pre></body></html>');
    $r->rflush();

    return;
}

# ================================================================ Main Handler

=pod

=item &handler()

The handler checks for permission to access the course data and for 
initial header problem.  Then it passes the torch to the work horse
function BuildChart.

=over 4

Input: $r

$r: This is the object that is used to print.

Output: A Value (OK or HTTP_NOT_ACCEPTABLE)

=back

=cut

sub handler {
    my $r=shift;
#    $jr=$r;
    unless(&Apache::lonnet::allowed('vgr',$ENV{'request.course.id'})) {
	$ENV{'user.error.msg'}=
        $r->uri.":vgr:0:0:Cannot view grades for complete course";
	return HTTP_NOT_ACCEPTABLE; 
    }

    # Set document type for header only
    if ($r->header_only) {
        if($ENV{'browser.mathml'}) {
            $r->content_type('text/xml');
        } else {
            $r->content_type('text/html');
        }
        &Apache::loncommon::no_cache($r);
        $r->send_http_header;
        return OK;
    }

    unless($ENV{'request.course.fn'}) {
        my $requrl=$r->uri;
        $ENV{'user.error.msg'}="$requrl:bre:0:0:Course not initialized";
        return HTTP_NOT_ACCEPTABLE; 
    }

    &BuildChart($r);

    return OK;
}
1;
__END__