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lonstatistics.pm:
   POD cleanups
   @SelectedSections is set when we read the classlist.
   Added variables $top_map, @Sequences, and @Assessments.  These are
      initialized by &PrepareCourseData($r).
   Added &PrepareCourseData($r) which is essentially a wrapper for
      &Apache::loncoursedata::get_sequence_assessment_data().
   Added &MapSelect() to output a <select> box for sequences.  Not tested.
   Added &SectionSelect(..) to output a <select> box for sections.  Tested.
   Added &DisplayClasslist($r) which displays a table of the current classlist
      that is sortable by each column.  Does not bother with 'update time' as
      this should not be an issue for the user.  Tested.
   Added call to &PrepareCourseData by the handler.
lonpercentage.pm, lonproblemanalysis.pm, lonproblemstatistics.pm,
lonstudentassessment.pm: modified to call &Apache::lonstatistics::SectionSelect
   instead of the method in lonhtmlcommon.pm.

# The LearningOnline Network with CAPA
#
# $Id: lonstatistics.pm,v 1.60 2003/02/25 20:47:47 matthew 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/
#
# (Navigate problems for statistical reports
#
###

=pod

=head1 NAME

lonstatistics

=head1 SYNOPSIS

Main handler for statistics and chart.

=head1 PACKAGES USED

    use strict;
    use Apache::Constants qw(:common :http);
    use Apache::lonnet();
    use Apache::lonhomework;
    use Apache::loncommon;
    use Apache::loncoursedata;
    use Apache::lonhtmlcommon;
    use Apache::lonproblemanalysis;
    use Apache::lonproblemstatistics;
    use Apache::lonstudentassessment;
    use Apache::lonpercentage;
    use GDBM_File;

=over 4

=cut

package Apache::lonstatistics;

use strict;
use Apache::Constants qw(:common :http);
use Apache::lonnet();
use Apache::lonhomework;
use Apache::loncommon;
use Apache::loncoursedata;
use Apache::lonhtmlcommon;
use Apache::lonproblemanalysis;
use Apache::lonproblemstatistics;
use Apache::lonstudentassessment;
use Apache::lonpercentage;
use GDBM_File;

use vars qw/@FullClasslist @Students @Sections @SelectedSections
    $curr_student $prev_student $next_student 
    $top_map @Sequences @Assessments /;

#######################################################
#######################################################

=pod

=item Package Variables

=item @FullClasslist The full classlist

=item @Students The students we are concerned with for this invocation

=item @Sections The sections available in this class

=item $curr_student The student currently being examined

=item $prev_student The student previous in the classlist

=item $next_student The student next in the classlist

=over

=cut 

#######################################################
#######################################################
#
# Classlist variables
#
my @FullClasslist;
my @Students;
my @Sections;
my @SelectedSections;
my $curr_student;
my $prev_student;
my $next_student;

#######################################################
#######################################################

=pod

=item &clear_classlist_variables()

undef the following package variables:

=over

=item @FullClasslist

=item @Students

=item @Sections

=item @SelectedSections

=item $curr_student

=item $prev_student

=item $next_student

=back

=cut

#######################################################
#######################################################
sub clear_classlist_variables {
    undef(@FullClasslist);
    undef(@Students);
    undef(@Sections);
    undef(@SelectedSections);
    undef($curr_student);
    undef($prev_student);
    undef($next_student);
}

#######################################################
#######################################################

=pod

=item &PrepareClasslist()

Build up the classlist information.  The classlist information is kept in
the following package variables:

=over

=item @FullClasslist

=item @Students

=item @Sections

=item @SelectedSections

=item $curr_student

=item $prev_student

=item $next_student

=back

$curr_student, $prev_student, and $next_student may not be defined, depending
upon the calling context.

=cut

#######################################################
#######################################################
sub PrepareClasslist {
    my $r = shift;
    my %Sections;
    &clear_classlist_variables();
    #
    # Retrieve the classlist
    my $cid  = $ENV{'request.course.id'};
    my $cdom = $ENV{'course.'.$cid.'.domain'};
    my $cnum = $ENV{'course.'.$cid.'.num'};
    my ($classlist,$field_names) = &Apache::loncoursedata::get_classlist($cid,
                                                                  $cdom,$cnum);
    if (exists($ENV{'form.Section'})) {
        if (ref($ENV{'form.Section'})) {
            @SelectedSections = @$ENV{'form.Section'};
            # Remove the empty sections
            for (my $i=0; $i<=$#SelectedSections; $i++) {
                if ($SelectedSections[$i] =~ /^\s*$/) {
                    splice(@SelectedSections,$i,1);
                }
            }
        } else {
            if ($ENV{'form.Section'} !~ /^\s*$/) {
                @SelectedSections = ($ENV{'form.Section'});
            }
        }
    }
    @SelectedSections = ('any') if (! @SelectedSections);
    #
    # Process the classlist
    while (my ($student,$student_data) = each (%$classlist)) {
        my $studenthash = ();
        for (my $i=0; $i< scalar(@$field_names);$i++) {
            $studenthash->{$field_names->[$i]}=$student_data->[$i];
        }
        push (@FullClasslist,$studenthash);
        #
        # Build up a list of sections
        my $section = $studenthash->{'section'};
        if (! defined($section) || $section =~/^\s*$/ || $section == -1) {
            $studenthash->{'section'} = 'none';
            $section = $studenthash->{'section'};
        }
        $Sections{$section}++;
        #
        # Only put in the list those students we are interested in
        foreach my $sect (@SelectedSections) {
            if (($sect eq 'any') || ($section eq $sect)) {
                push (@Students,$studenthash);
                last;
            }
        }
    }
    #
    # Put the consolidated section data in the right place
    @Sections = sort {$a cmp $b} keys(%Sections);
    #
    # Sort the Students
    my $sortby = 'fullname';
    $sortby = $ENV{'form.sort'} if (exists($ENV{'form.sort'}));
    my @TmpStudents = sort { $a->{$sortby} cmp $b->{$sortby} ||
                             $a->{'fullname'} cmp $b->{'fullname'} } @Students;

    @Students = @TmpStudents;
    # 
    # Now deal with that current student thing....
    if (exists($ENV{'form.StudentAssessmentStudent'})) {
        my ($current_uname,$current_dom) = 
            split(':',$ENV{'form.StudentAssessmentStudent'});
        my $i;
        for ($i = 0; $i<=$#Students; $i++) {
            next if (($Students[$i]->{'username'} ne $current_uname) || 
                     ($Students[$i]->{'domain'}   ne $current_dom));
            $curr_student = $Students[$i];
            last; # If we get here, we have our student.
        }
        if ($i == 0) {
            $prev_student = 'none';
        } else {
            $prev_student = $Students[$i-1];
        }
        if ($i == $#Students) {
            $next_student = 'none';
        } else {
            $next_student = $Students[$i+1];
        }
    }
}

#######################################################
#######################################################
#
# Course Sequences variables
#
my $top_map;
my @Sequences;
my @Assessments;

#######################################################
#######################################################

=pod

=item &clear_sequence_variables()

=cut

#######################################################
#######################################################
sub clear_sequence_variables {
    undef($top_map);
    undef(@Sequences);
    undef(@Assessments);
}

#######################################################
#######################################################

=pod

=item &PrepareCourseData($r)

=cut

#######################################################
#######################################################
sub PrepareCourseData {
    my ($r) = @_;
    &clear_sequence_variables();
    my ($top,$sequences,$assessments) = &Apache::loncoursedata::get_sequence_assessment_data();
    if (! defined($top) || ! ref($top)) {
        # There has been an error, better report it
        &Apache::lonnet::logthis('top is undefined');
        return;
    }
    $top_map = $top if (ref($top));
    @Sequences = @{$sequences} if (ref($sequences) eq 'ARRAY');
    @Assessments = @{$assessments} if (ref($assessments) eq 'HASH');

=pod

    ##
    ## Debugging code
    ##
    foreach my $s (@Sequences) {
        next if ($s->{'title'} ne 'Bioenergetics: Enzyme Regulation');
        &Apache::lonnet::logthis('-----------------------------------');
        &Apache::lonnet::logthis('title      = '.$s->{'title'});
        &Apache::lonnet::logthis('symb       = '.$s->{'symb'});
        &Apache::lonnet::logthis('num_assess = '.$s->{'num_assess'});
        foreach my $a (@{$s->{'contents'}}) {
            &Apache::lonnet::logthis('   --------------------------------');
            &Apache::lonnet::logthis('   title      = '.$a->{'title'});
            &Apache::lonnet::logthis('   symb       = '.$a->{'symb'});
        }
    }

=cut

    return;
}

##############################################
##############################################

=pod 

=item &MapSelect($elementname,$status,$numvisible,$selected,$restriction) 

Returns html for a selection box allowing the user to choose one (or more) 
of the sequences in the course.  The values of the sequences are the symbs.
If the top sequence is selected, the value 'top' will result.

=over 4

=item $elementname The name of the HTML form element

=item $status 'multiple' or 'single' selection box

=item $numvisible The number of options to be visible

=item $selected Array ref to the names of the already selected maps.
If undef, $ENV{'form.'.$elementname} is used.  
If $ENV{'form.'.$elementname} is also empty, none will be selected.

=item $restriction Code reference to subroutine which returns true or 
false.  The code must expect a reference to a sequence data structure.

=back

=cut

##############################################
##############################################
sub MapSelect {
    my ($elementname,$status,$numvisible,$selected,$restriction)=@_;
    if ($numvisible < 1) {
        return;
    }
    #
    # Set up array of selected items
    my @Selected;
    if (! defined($selected)) {
        if (exists($ENV{'form.'.$elementname})) {
            if (ref($ENV{'form.'.$elementname})) {
                @Selected = @$ENV{'form.'.$elementname};
            } else {
                @Selected = ($ENV{'form.'.$elementname});
            }
        } else {
            @Selected = ();
        }
    } else {
        if (ref($selected)) {
            @Selected = @$selected;
        } else {
            @Selected = ($selected);
        }
    }
    #
    # Set up the restriction call
    if (! defined($restriction)) {
        $restriction = sub { 1; };
    }
    #
    # Build the form element
    my $Str = "\n";
    $Str .= '<select name="'.$elementname.'" ';
    if ($status ne 'single') {
        $Str .= 'multiple="true" ';
    }
    $Str .= 'size="'.$numvisible.'" >'."\n";
    #
    # Loop through the sequences
    foreach my $s (@Sequences) {
        next if (! $restriction->($s));
        $Str .= '    <option value="'.$s->{'symb'}.'" ';
        foreach (@Selected) {
            if ($s->{'symb'} eq $_) {
                $Str .= 'selected ';
                last;
            }
        }
        $Str .= '>'.$s->{'title'}."</option>\n";
    }
    $Str .= "</select>\n";
    return $Str;
}


##############################################
##############################################

=pod 

=item &SectionSelect($elementname,$status,$numvisible) 

Returns html for a selection box allowing the user to choose one (or more) 
of the sections in the course.  

=over 4

=item $elementname The name of the HTML form element

=item $status 'multiple' or 'single' selection box

=item $numvisible The number of options to be visible

=item $selected Array ref to the names of the already selected sections.
If undef, $ENV{'form.'.$elementname} is used.  
If $ENV{'form.'.$elementname} is also empty, none will be selected.

=item $restriction Code reference to subroutine which returns true or 
false.  The code must expect a reference to a sequence data structure.

=back

=cut

##############################################
##############################################
sub SectionSelect {
    my ($elementname,$status,$numvisible)=@_;
    if ($numvisible < 1) {
        return;
    }
    #
    # Build the form element
    my $Str = "\n";
    $Str .= '<select name="'.$elementname.'" ';
    if ($status ne 'single') {
        $Str .= 'multiple="true" ';
    }
    $Str .= 'size="'.$numvisible.'" >'."\n";
    #
    # Loop through the sequences
    foreach my $s (@Sections) {
        $Str .= '    <option value="'.$s.'" ';
        foreach (@SelectedSections) {
            if ($s eq $_ || $_ =~ /^(any|all)$/) {
                $Str .= 'selected ';
                last;
            }
        }
        $Str .= '>'.$s."</option>\n";
    }
    $Str .= "</select>\n";
    return $Str;
}

##############################################
##############################################

sub CheckFormElement {
    my ($cache, $ENVName, $cacheName, $default)=@_;

    if(defined($ENV{'form.'.$ENVName})) {
        $cache->{$cacheName} = $ENV{'form.'.$ENVName};
    } elsif(!defined($cache->{$cacheName})) {
        $cache->{$cacheName} = $default;
    } else {
        $ENV{'form.'.$ENVName} = $cache->{$cacheName};
    }
    return;
}

sub ProcessFormData{
    my ($cache)=@_;

    $cache->{'reportKey'} = 'false';

    &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},
                                            ['download',
                                             'reportSelected',
                                             'StudentAssessmentStudent',
                                             'ProblemStatisticsSort']);
    &CheckFormElement($cache, 'DownloadAll', 'DownloadAll', 'false');
    if ($cache->{'DownloadAll'} ne 'false') {
        # Clean the hell out of that cache!
        # We cannot untie the hash at this scope (stupid libgd :( )
        # So, remove every single key.  What a waste of time....
        # Of course, if you are doing this you are probably resigned
        # to waiting a while.
        &Apache::lonnet::logthis("Cleaning out the cache file");
        while (my ($key,undef)=each(%$cache)) {
            next if ($key eq 'DownloadAll');
            delete($cache->{$key});
        }
    }
    &CheckFormElement($cache, 'Status', 'Status', 'Active');
    &CheckFormElement($cache, 'postdata', 'reportSelected', 'Class list');
    &CheckFormElement($cache, 'reportSelected', 'reportSelected', 
                      'Class list');
    $cache->{'reportSelected'} = 
        &Apache::lonnet::unescape($cache->{'reportSelected'});
    &CheckFormElement($cache, 'sort', 'sort', 'fullname');
    &CheckFormElement($cache, 'download', 'download', 'false');
    &CheckFormElement($cache, 'StatisticsMaps', 
                      'StatisticsMaps', 'All Maps');
    &CheckFormElement($cache, 'StatisticsProblemSelect',
		      'StatisticsProblemSelect', 'All Problems');
    &CheckFormElement($cache, 'StatisticsPartSelect',
		      'StatisticsPartSelect', 'All Parts');
    if(defined($ENV{'form.Section'})) {
        my @sectionsSelected = (ref($ENV{'form.Section'}) ?
                               @{$ENV{'form.Section'}} :
                                ($ENV{'form.Section'}));
        $cache->{'sectionsSelected'} = join(':', @sectionsSelected);
    } elsif(!defined($cache->{'sectionsSelected'})) {
        $cache->{'sectionsSelected'} = $cache->{'sectionList'};
    }

    # student assessment
    if(defined($ENV{'form.CreateStudentAssessment'}) ||
       defined($ENV{'form.NextStudent'}) ||
       defined($ENV{'form.PreviousStudent'})) {
        $cache->{'reportSelected'} = 'Student Assessment';
    }
    if(defined($ENV{'form.NextStudent'})) {
        $cache->{'StudentAssessmentMove'} = 'next';
    } elsif(defined($ENV{'form.PreviousStudent'})) {
        $cache->{'StudentAssessmentMove'} = 'previous';
    } else {
        $cache->{'StudentAssessmentMove'} = 'selected';
    }
    &CheckFormElement($cache, 'StudentAssessmentStudent', 
                      'StudentAssessmentStudent', 'All Students');
    $cache->{'StudentAssessmentStudent'} = 
        &Apache::lonnet::unescape($cache->{'StudentAssessmentStudent'});
    &CheckFormElement($cache, 'DefaultColumns', 'DefaultColumns', 'false');

    # Problem analysis
    &CheckFormElement($cache, 'Interval', 'Interval', '1');

    # ProblemStatistcs
    &CheckFormElement($cache, 'DisplayCSVFormat',
                      'DisplayFormat', 'Display Table Format');
    &CheckFormElement($cache, 'ProblemStatisticsAscend',
                      'ProblemStatisticsAscend', 'Ascending');
    &CheckFormElement($cache, 'ProblemStatisticsSort',
                      'ProblemStatisticsSort', 'Homework Sets Order');
    &CheckFormElement($cache, 'DisplayLegend', 'DisplayLegend', 
		      'Hide Legend');
    &CheckFormElement($cache, 'SortProblems', 'SortProblems', 
                      'Sort Within Sequence');

    # Search only form elements
    my @headingColumns=();
    my @sequenceColumns=();
    my $foundColumn = 0;
    if(defined($ENV{'form.ReselectColumns'})) {
        my @reselected = (ref($ENV{'form.ReselectColumns'}) ? 
                          @{$ENV{'form.ReselectColumns'}}
                          : ($ENV{'form.ReselectColumns'}));
        foreach (@reselected) {
            if(/HeadingColumn/) {
                push(@headingColumns, $_);
                $foundColumn = 1;
            } elsif(/SequenceColumn/) {
                push(@sequenceColumns, $_);
                $foundColumn = 1;
            }
        }
    }

    $cache->{'reportKey'} = 'false';
    if($cache->{'reportSelected'} eq 'Analyze') {
        $cache->{'reportKey'} = 'Analyze';
    } elsif($cache->{'reportSelected'} eq 'DoDiffGraph') {
        $cache->{'reportKey'} = 'DoDiffGraph';
    } elsif($cache->{'reportSelected'} eq 'PercentWrongGraph') {
        $cache->{'reportKey'} = 'PercentWrongGraph';
    }

    if(defined($ENV{'form.DoDiffGraph'})) {
        $cache->{'reportSelected'} = 'DoDiffGraph';
        $cache->{'reportKey'} = 'DoDiffGraph';
    } elsif(defined($ENV{'form.PercentWrongGraph'})) {
        $cache->{'reportSelected'} = 'PercentWrongGraph';
        $cache->{'reportKey'} = 'PercentWrongGraph';
    }

    foreach (keys(%ENV)) {
        if(/form\.Analyze/) {
            $cache->{'reportSelected'} = 'Analyze';
            $cache->{'reportKey'} = 'Analyze';
            my $data;
            (undef, $data)=split(':::', $_);
            $cache->{'AnalyzeInfo'}=$data;
        } elsif(/form\.HeadingColumn/) {
            my $value = $_;
            $value =~ s/form\.//;
            push(@headingColumns, $value);
            $foundColumn=1;
        } elsif(/form\.SequenceColumn/) {
            my $value = $_;
            $value =~ s/form\.//;
            push(@sequenceColumns, $value);
            $foundColumn=1;
        }
    }

    if($foundColumn) {
        $cache->{'HeadingsFound'} = join(':', @headingColumns);
        $cache->{'SequencesFound'} = join(':', @sequenceColumns);;
    }
    if(!defined($cache->{'HeadingsFound'}) || 
       $cache->{'DefaultColumns'} ne 'false') {
        $cache->{'HeadingsFound'}='HeadingColumnFull Name';
    }
    if(!defined($cache->{'SequencesFound'}) ||
       $cache->{'DefaultColumns'} ne 'false') {
        $cache->{'SequencesFound'}='All Sequences';
    }
    $cache->{'DefaultColumns'} = 'false';

    return;
}

=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 ($cache)=@_;

    my @students = split(':::',$cache->{'NamesOfStudents'});
    my @sorted1Students=();
    foreach (@students) {
        if($cache->{'Status'} eq 'Any' || 
           $cache->{$_.':Status'} eq $cache->{'Status'}) {
            push(@sorted1Students, $_);
        }
    }

    my $sortBy = '';
    if(defined($cache->{'sort'})) {
        $sortBy = ':'.$cache->{'sort'};
    } else {
        $sortBy = ':fullname';
    }
    my @order = sort { lc($cache->{$a.$sortBy}) cmp lc($cache->{$b.$sortBy}) ||
                       lc($cache->{$a.':fullname'}) cmp lc($cache->{$b.':fullname'}) } 
                @sorted1Students;

    return \@order;
}

=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,$headings,$cache)=@_;

    # Initialize Lengths
    for(my $index=0; $index<(scalar @$headings); $index++) {
        my @titleLength=split(//,$headings->[$index]);
        $cache->{$studentInformation->[$index].':columnWidth'}=
            scalar @titleLength;
    }

    foreach my $name (@$students) {
        foreach (@$studentInformation) {
            my @dataLength=split(//,$cache->{$name.':'.$_});
            my $length=(scalar @dataLength);
            if($length > $cache->{$_.':columnWidth'}) {
                $cache->{$_.':columnWidth'}=$length;
            }
        }
    }

    return;
}

sub PrepareData {
    my ($c, $cacheDB, $studentInformation, $headings,$r)=@_;

    # Test for access to the cache data
    my $courseID=$ENV{'request.course.id'};
    my $isRecalculate=0;
    if(defined($ENV{'form.Recalculate'})) {
        $isRecalculate=1;
    }

    my $isCached = &Apache::loncoursedata::TestCacheData($cacheDB,
                                                         $isRecalculate);
    if($isCached < 0) {
        return "Unable to tie hash to db file.";
    }

    # Download class list information if not using cached data
    my %cache;
    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_WRCREAT(),0640)) {
        return "Unable to tie hash to db file.";
    }

#    if(!$isCached) {
        my $processTopResourceMapReturn=
            &Apache::loncoursedata::ProcessTopResourceMap(\%cache, $c);
        if($processTopResourceMapReturn ne 'OK') {
            untie(%cache);
            return $processTopResourceMapReturn;
        }
 #   }

    if($c->aborted()) {
        untie(%cache);
        return 'aborted'; 
    }

    my $classlist=&Apache::loncoursedata::DownloadClasslist($courseID,
                                                $cache{'ClasslistTimestamp'},
                                                $c);
    foreach (keys(%$classlist)) {
        if(/^(con_lost|error|no_such_host)/i) {
            untie(%cache);
            return "Error getting student data.";
        }
    }

    if($c->aborted()) {
        untie(%cache);
        return 'aborted'; 
    }

    # Active is a temporary solution, remember to change
    Apache::loncoursedata::ProcessClasslist(\%cache,$classlist,$courseID,$c);
    if($c->aborted()) {
        untie(%cache);
        return 'aborted'; 
    }

    &ProcessFormData(\%cache);
    my $students = &SortStudents(\%cache);
    &SpaceColumns($students, $studentInformation, $headings, \%cache);
    $cache{'updateTime:columnWidth'}=24;

    my $download = $cache{'download'};
    my $downloadAll = $cache{'DownloadAll'};
    my @allStudents=();
    if($download ne 'false') {
        $cache{'download'} = 'false';
    } elsif($downloadAll ne 'false') {
        $cache{'DownloadAll'} = 'false';
        if($downloadAll eq 'sorted') {
            @allStudents = @$students;
        } else {
            @allStudents = split(':::', $cache{'NamesOfStudents'});
        }
    }

    untie(%cache);

    if($download ne 'false') {
        my @who = ($download);
        if(&Apache::loncoursedata::DownloadStudentCourseData(\@who, 'false',
                                                             $cacheDB, 'true',
                                                             'false', $courseID,
                                                             $r, $c) ne 'OK') {
            return 'Stop at download individual';
        }
    } elsif($downloadAll ne 'false') {
        if(&Apache::loncoursedata::DownloadStudentCourseData(\@allStudents,
                                                             'false',
                                                             $cacheDB, 'true',
                                                             'true', $courseID,
                                                             $r, $c) ne 'OK') {
            return 'Stop at download all';
        }
    }

    return ('OK', $students);
}

sub DisplayClasslist {
    my ($r)=@_;
    #
    my @Fields = ('fullname','username','domain','id','section');
    #
    my $Str='';
    $Str .= '<table border="0"><tr><td bgcolor="#777777">'."\n";
    $Str .= '<table border="0" cellpadding="3"><tr bgcolor="#e6ffff">'."\n";
    foreach my $field (@Fields) {
        $Str .= '<th><a href="/adm/statistics?sort='.$field.'">'.$field.
            '</a></th>';
    }
    $Str .= '</tr>'."\n";
    #
    my $alternate = 0;
    foreach my $student (@Students) {
        my $sname = $student->{'username'}.':'.$student->{'domain'};
        if($alternate) {
            $Str .= '<tr bgcolor="#ffffe6">';
        } else {
            $Str .= '<tr bgcolor="#ffffc6">';
        }
        $alternate = ($alternate + 1) % 2;
        #
        foreach my $field (@Fields) {
            $Str .= '<td>';
            if ($field eq 'fullname') {
                $Str .= '<a href="/adm/statistics?reportSelected=';
                $Str .= &Apache::lonnet::escape('Student Assessment');
                $Str .= '&StudentAssessmentStudent=';
                $Str .= &Apache::lonnet::escape($student->{$field}).'">';
                $Str .= $student->{$field}.'&nbsp';
                $Str .= '</a>';
            } else {
                $Str .= $student->{$field};
            }
            $Str .= '</td>';
        }
        $Str .= "</tr>\n";
    }
    $Str .= '</table></td></tr></table>'."\n";
    #
    $r->print($Str);
    $r->rflush();
    #
    return;
}

sub BuildClasslist {
    my ($cacheDB,$students,$studentInformation,$headings,$r)=@_;

    my %cache;
    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
        return '<html><body>Unable to tie database.</body></html>';
    }

#    my $Ptr = '';
#    $Ptr .= '<table border="0"><tbody>';
#    $Ptr .= '<tr><td align="right"><b>Select Sections</b>';
#    $Ptr .= '</td>'."\n";
#    $Ptr .= '<td align="left">'."\n";
#    my @sectionsSelected = split(':',$cache{'sectionsSelected'});
#    my @sections = split(':',$cache{'sectionList'});
#    $Ptr .= &Apache::lonhtmlcommon::MultipleSectionSelect(\@sections,
#                                                          \@sectionsSelected,
#                                                          'Statistics');
#    $Ptr .= '</td></tr></table><br>';
#    $r->print($Ptr);
#    $r->rflush();
#    my %mySections = ();
#    foreach (@sections) { $mySections{$_} = 'True'; }
#    $r->print("<br>$cache{'sectionsSelected'}<br>");

    my $Str='';
    $Str .= '<table border="0"><tr><td bgcolor="#777777">'."\n";
    $Str .= '<table border="0" cellpadding="3"><tr bgcolor="#e6ffff">'."\n";

    my $displayString = '<td align="left"><a href="/adm/statistics?';
    $displayString .= 'sort=LINKDATA">DISPLAYDATA&nbsp</a></td>'."\n";
    $Str .= &Apache::lonhtmlcommon::CreateHeadings(\%cache,
                                                   $studentInformation,
                                                   $headings, $displayString);
    $Str .= '</tr>'."\n";

    my $alternate=0;
    foreach (@$students) {
#        if ($mySections{$cache{$_.':'.'section'}} ne 'True') {next;}
        my ($username, $domain) = split(':', $_);
        if($alternate) {
            $Str .= '<tr bgcolor="#ffffe6">';
        } else {
            $Str .= '<tr bgcolor="#ffffc6">';
        }
        $alternate = ($alternate + 1) % 2;
        foreach my $data (@$studentInformation) {
            $Str .= '<td>';
            if($data eq 'fullname') {
                $Str .= '<a href="/adm/statistics?reportSelected=';
                $Str .= &Apache::lonnet::escape('Student Assessment');
                $Str .= '&StudentAssessmentStudent=';
                $Str .= &Apache::lonnet::escape($cache{$_.':'.$data}).'">';
                $Str .= $cache{$_.':'.$data}.'&nbsp';
                $Str .= '</a>';
            } elsif($data eq 'updateTime') {
                $Str .= '<a href="/adm/statistics?reportSelected=';
                $Str .= &Apache::lonnet::escape('Class list');
                $Str .= '&download='.$_.'">';
                $Str .= $cache{$_.':'.$data}.'&nbsp';
                $Str .= '&nbsp</a>';
            } else {
                $Str .= $cache{$_.':'.$data}.'&nbsp';
            }

            $Str .= '</td>'."\n";
        }
    }

    $Str .= '</tr>'."\n";
    $Str .= '</table></td></tr></table>'."\n";
    $r->print($Str);
    $r->rflush();

    untie(%cache);

    return;
}

sub CreateMainMenu {
    my ($status, $reports)=@_;

    my $Str = '';

    $Str .= '<table border="0"><tbody><tr>'."\n";
    $Str .= '<td></td><td></td>'."\n";
    $Str .= '<td align="center"><b>Select a Report</b></td>'."\n";
    $Str .= '<td align="center"><b>Student Status</b></td></tr>'."\n";
    $Str .= '<tr>'."\n";
    $Str .= '<td align="center"><input type="submit" name="Refresh" ';
    $Str .= 'value="Refresh" /></td>'."\n";
    $Str .= '<td align="center"><input type="submit" name="DownloadAll" ';
    $Str .= 'value="Update All Student Data" /></td>'."\n";
    $Str .= '<td align="center">';
    $Str .= '<select name="reportSelected" onchange="document.';
    $Str .= 'Statistics.submit()">'."\n";

    foreach (sort(keys(%$reports))) {
        next if($_ eq 'reportSelected');
        $Str .= '<option name="'.$_.'"';
        if($reports->{'reportSelected'} eq $reports->{$_}) {
            $Str .= ' selected=""';
        }
        $Str .= '>'.$reports->{$_}.'</option>'."\n";
    }
    $Str .= '</select></td>'."\n";

    $Str .= '<td align="center">';
    $Str .= &Apache::lonhtmlcommon::StatusOptions($status, 'Statistics');
    $Str .= '</td>'."\n";

    $Str .= '</tr></tbody></table>'."\n";
    $Str .= '<hr>'."\n";

    return $Str;
}

sub BuildStatistics {
    my ($r)=@_;

    my $c = $r->connection;
    my @studentInformation=('fullname','section','id','domain','username',
                            'updateTime');
    my @headings=('Full Name', 'Section', 'PID', 'Domain', 'User Name',
                  'Last Updated');
    my $spacing = '   ';

    my %reports = ('classlist'          => 'Class list',
                   'problem_statistics' => 'Problem Statistics',
                   'student_assessment' => 'Student Assessment',
		   'percentage'         => 'Correct-problems Plot',
#                   'activitylog'        => 'Activity Log',
                   'reportSelected'     => 'Class list');

    my %cache;
    my $courseID=$ENV{'request.course.id'};
    my $cacheDB = "/home/httpd/perl/tmp/$ENV{'user.name'}".
                  "_$ENV{'user.domain'}_$courseID\_statistics.db";

    $r->print(&Apache::lonhtmlcommon::Title('Course Statistics and Charts'));

    my ($returnValue, $students) = &PrepareData($c, $cacheDB,
                                                \@studentInformation,
                                                \@headings,$r);
    if($returnValue ne 'OK') {
        $r->print($returnValue."\n".'</body></html>');
        return OK;
    }
    if(!$c->aborted()) {
        &Apache::loncoursedata::CheckForResidualDownload($cacheDB,
                                                         'true', 'true',
                                                         $courseID,
                                                         $r, $c);
    }

    my $GoToPage;
    if(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
        $GoToPage = $cache{'reportSelected'};
        $reports{'reportSelected'} = $cache{'reportSelected'};
        if(defined($cache{'reportKey'}) &&
           !exists($reports{$cache{'reportKey'}}) &&
           $cache{'reportKey'} ne 'false') {
            $reports{$cache{'reportKey'}} = $cache{'reportSelected'};
        }

        if(defined($cache{'OptionResponses'})) {
            $reports{'problem_analysis'} = 'Option Response Analysis';
        }

        $r->print('<form name="Statistics" ');
        $r->print('method="post" action="/adm/statistics">');
        $r->print(&CreateMainMenu($cache{'Status'}, \%reports));
        $r->rflush();
        untie(%cache);
    } else {
        $r->print('<html><body>Unable to tie database.</body></html>');
        return OK;
    }

    if($GoToPage eq 'Activity Log') {
        &Apache::lonproblemstatistics::Activity();
    } elsif($GoToPage eq 'Problem Statistics') {
        &Apache::lonproblemstatistics::BuildProblemStatisticsPage($cacheDB,
                                                                  $students,
                                                                  $courseID,
                                                                  $c,$r);
    } elsif($GoToPage eq 'Option Response Analysis') {
        &Apache::lonproblemanalysis::BuildProblemAnalysisPage($cacheDB, $r);
    } elsif($GoToPage eq 'Student Assessment') {
        &Apache::lonstudentassessment::BuildStudentAssessmentPage($cacheDB,
                                                          $students,
                                                          $courseID,
                                                          'Statistics',
                                                          \@headings,
                                                          $spacing,
                                                          \@studentInformation,
                                                          $r, $c);
    } elsif($GoToPage eq 'Analyze') {
        &Apache::lonproblemanalysis::BuildAnalyzePage($cacheDB, $students,
                                                      $courseID, $r);
    } elsif($GoToPage eq 'DoDiffGraph' || $GoToPage eq 'PercentWrongGraph') {
        my $courseDescription = $ENV{'course.'.$courseID.'.description'};
        $courseDescription =~ s/\ /"_"/eg;
        &Apache::lonproblemstatistics::BuildGraphicChart($GoToPage, $cacheDB,
                                                         $courseDescription,
                                                         $students, $courseID,
                                                         $r, $c);
    } elsif($GoToPage eq 'Class list') {
        &DisplayClasslist($r);
#        &BuildClasslist($cacheDB, $students, \@studentInformation,
#                        \@headings, $r);
    } elsif($GoToPage eq 'Correct-problems Plot') {
	&Apache::lonpercentage::BuildPercentageGraph($cacheDB, $students,
						     $courseID, $c, $r);
    }

    $r->print('</form>'."\n");
    $r->print("\n".'</body>'."\n".'</html>');
    $r->rflush();

    return OK;
}

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

sub handler {
    my $r=shift;

#    $jr = $r;

    my $loaderror=&Apache::lonnet::overloaderror($r);
    if ($loaderror) { return $loaderror; }
    $loaderror=
       &Apache::lonnet::overloaderror($r,
         $ENV{'course.'.$ENV{'request.course.id'}.'.home'});
    if ($loaderror) { return $loaderror; }

    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;
    }

    $r->content_type('text/html');
    $r->send_http_header;

    &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},
                                            ['sort']);

    &PrepareClasslist($r);

    &PrepareCourseData($r);

    &BuildStatistics($r);

    return OK;
}
1;

=pod

=back

=cut

__END__