# The LearningOnline Network with CAPA
# Dynamic plot
#
# $Id: lonplot.pm,v 1.22 2001/12/28 19:04:56 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/
#
# 12/15/01 Matthew
# 12/17 12/18 12/19 12/20 12/21 12/27 12/28 Matthew
package Apache::lonplot;

use strict;
use Apache::File;
use Apache::response;
use Apache::lonxml;
use Apache::edit;

sub BEGIN {
  &Apache::lonxml::register('Apache::lonplot',('plot'));
}

## 
## Description of data structures:
##
##  %plot       %key    %axis
## --------------------------
##  height      title   color
##  width       box     xmin
##  bgcolor     pos     xmax
##  fgcolor             ymin
##  transparent         ymax
##  grid
##  border
##  font
##  align
##
##  @labels: $labels[$i] = \%label
##           %label: text, xpos, ypos, justify
##
##  @curves: $curves[$i] = \%curve
##           %curve: name, linestyle, ( function | data )
##
##  $curves[$i]->{'data'} = [ [x1,x2,x3,x4],
##                            [y1,y2,y3,y4] ]
##

###################################################################
##                                                               ##
##        Tests used in checking the validitity of input         ##
##                                                               ##
###################################################################
my $int_test       = sub {$_[0]=~s/\s+//g;$_[0]=~/^\d+$/};
my $real_test      = 
    sub {$_[0]=~s/\s+//g;$_[0]=~/^[+-]?\d*\.?\d*([eE][+-]\d+)?$/};
my $color_test     = sub {$_[0]=~s/\s+//g;$_[0]=~/^x[\da-f]{6}$/};
my $onoff_test     = sub {$_[0]=~/^(on|off)$/};
my $key_pos_test   = sub {$_[0]=~/^(top|bottom|right|left|outside|below| )+$/};
my $sml_test       = sub {$_[0]=~/^(small|medium|large)$/};
my $linestyle_test = sub {$_[0]=~/^(lines|linespoints|dots|points|steps)$/};
my $words_test     = sub {$_[0]=~s/\s+/ /g;$_[0]=~/^([\w\(\)]+ ?)+$/};

###################################################################
##                                                               ##
##                      Attribute metadata                       ##
##                                                               ##
###################################################################
my %plot_defaults = 
    (
     height       => {
	 default     => 200,
	 test        => $int_test,
	 description => 'vertical size of image (pixels)',
	 edit_type   => 'entry' 
	 },
     width        => {
	 default     => 200,
	 test        => $int_test,
	 description => 'horizontal size of image (pixels)',
	 edit_type   => 'entry'
	 },
     bgcolor      => {
	 default     => 'xffffff',
	 test        => $color_test, 
	 description => 'background color of image (xffffff)',
	 edit_type   => 'entry'
	 },
     fgcolor      => {
	 default     => 'x000000',
	 test        => $color_test,
	 description => 'foreground color of image (x000000)',
	 edit_type   => 'entry' 
	 },
     transparent  => {
	 default     => 'off',
	 test        => $onoff_test, 
	 description => '',
	 edit_type   => 'on_off'
	 },
     grid         => {
	 default     => 'off',
	 test        => $onoff_test, 
	 description => '',
	 edit_type   => 'on_off'
	 },
     border       => {
	 default     => 'on',
	 test        => $onoff_test, 
	 description => '',
	 edit_type   => 'on_off'
	 },
     font         => {
	 default     => 'medium',
	 test        => $sml_test,
	 description => 'Size of font to use',
	 edit_type   => 'choice',
	 choices     => ['small','medium','large']
	 },
     align        => {
	 default     => 'left',
	 test        => sub {$_[0]=~/^(left|right|center)$/},
	 description => 'alignment for image in html',
	 edit_type   => 'choice',
	 choices     => ['left','right','center']
	 } 
     );

my %key_defaults = 
    (
     title => { 
	 default => '',
	 test => $words_test,
	 description => 'Title of key',
	 edit_type   => 'entry'
	 },
     box   => { 
	 default => 'off',
	 test => $onoff_test,
	 description => 'Draw a box around the key?',
	 edit_type   => 'on_off'
	 },
     pos   => { 
	 default => 'top right', 
	 test => $key_pos_test, 
	 description => 'position of the key on the plot',
	 edit_type   => 'choice',
	 choices     => ['top left','top right','bottom left','bottom right',
			 'outside','below']
	 }
     );

my %label_defaults = 
    (
     xpos    => {
	 default => 0,
	 test => $real_test,
	 description => 'x position of label (graph coordinates)',
	 edit_type   => 'entry'
	 },
     ypos    => {
	 default => 0, 
	 test => $real_test,
	 description => 'y position of label (graph coordinates)',
	 edit_type   => 'entry'
	 },
     justify => {
	 default => 'left',    
	 test => sub {$_[0]=~/^(left|right|center)$/},
	 description => 'justification of the label text on the plot',
	 edit_type   => 'choice',
	 choices     => ['left','right','center']
     }
     );

my %axis_defaults = 
    (
     color     => {
	 default => 'x000000', 
	 test => $color_test,
	 description => 'color of axes (x000000)',
	 edit_type   => 'entry'
	 },
     xmin      => {
	 default => '-10.0',
	 test => $real_test,
	 description => 'minimum x-value shown in plot',
	 edit_type   => 'entry'
	 },
     xmax      => {
	 default => ' 10.0',
	 test => $real_test,
	 description => 'maximum x-value shown in plot',	 
	 edit_type   => 'entry'
	 },
     ymin      => {
	 default => '-10.0',
	 test => $real_test,
	 description => 'minimum y-value shown in plot',	 
	 edit_type   => 'entry'
	 },
     ymax      => {
	 default => ' 10.0',
	 test => $real_test,
	 description => 'maximum y-value shown in plot',	 
	 edit_type   => 'entry'
	 },
     linestyle => {
	 default => 'points',
	 test => $linestyle_test,
	 description => 'Style of the axis lines',
	 edit_type   => 'choice',
	 choices     => ['lines','linespoints','dots','points']
	 }
     );

my %curve_defaults = 
    (
     color     => {
	 default => 'x000000',
	 test => $color_test,
	 description => 'color of curve (x000000)',
	 edit_type   => 'entry'
	 },
     name      => {
	 default => '',
	 test => $words_test,
	 description => 'name of curve to appear in key',
	 edit_type   => 'entry'
	 },
     linestyle => {
	 default => 'lines',
	 test => $linestyle_test,
	 description => 'Style of the axis lines',
	 edit_type   => 'choice',
	 choices     => ['lines','linespoints','dots','points','steps']
	 }
     );

###################################################################
##                                                               ##
##                    parsing and edit rendering                 ##
##                                                               ##
###################################################################
my (%plot,%key,%axis,$title,$xlabel,$ylabel,@labels,@curves);

sub start_plot {
    %plot    = undef;   %key     = undef;   %axis   = undef; 
    $title   = undef;   $xlabel  = undef;   $ylabel = undef;
    $#labels = -1;      $#curves = -1;
    #
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	&Apache::lonxml::register('Apache::lonplot',
	      ('title','xlabel','ylabel','key','axis','label','curve'));
	push (@Apache::lonxml::namespace,'plot');
	## Always evaluate the insides of the <plot></plot> tags
	my $inside = &Apache::lonxml::get_all_text("/plot",$$parser[-1]);
	$inside=&Apache::run::evaluate($inside,$safeeval,$$parstack[-1]);
	&Apache::lonxml::newparser($parser,\$inside);
	##-------------------------------------------------------
	&get_attributes(\%plot,\%plot_defaults,$parstack,$safeeval,
			$tagstack->[-1]);
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	$result .= &edit_attributes($target,$token,\%plot_defaults);
    } elsif ($target eq 'modified') {
	my $constructtag=&Apache::edit::get_new_args
	    ($token,$parstack,$safeeval,keys %plot_defaults);
	if ($constructtag) {
	    $result = &Apache::edit::rebuild_tag($token);
	    $result.= &Apache::edit::handle_insert();
	}
    }
    return $result;
}

sub end_plot {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    pop @Apache::lonxml::namespace;
    &Apache::lonxml::deregister('Apache::lonplot',
	('title','xlabel','ylabel','key','axis','label','curve'));
    my $result = '';
    if ($target eq 'web') {
	&check_inputs(); # Make sure we have all the data we need
	##
	## Determine filename
	my $tmpdir = '/home/httpd/perl/tmp/';
	my $filename = $ENV{'user.name'}.'_'.$ENV{'user.domain'}.
	    '_'.time.'_'.$$.'_plot.data';
	## Write the plot description to the file
	my $fh=Apache::File->new(">$tmpdir$filename");
	print $fh &write_gnuplot_file();
	close($fh);
	## return image tag for the plot
	$result .= <<"ENDIMAGE";
<img src    = "/cgi-bin/plot.gif?$filename" 
     width  = "$plot{'width'}" 
     height = "$plot{'height'}"
     align  = "$plot{'align'}"
     alt    = "/cgi-bin/plot.gif?$filename" />
ENDIMAGE
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}

##----------------------------------------------------------------- key
sub start_key {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	&get_attributes(\%key,\%key_defaults,$parstack,$safeeval,
		    $tagstack->[-1]);
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	$result .= &edit_attributes($target,$token,\%key_defaults);
    } elsif ($target eq 'modified') {
	my $constructtag=&Apache::edit::get_new_args
	    ($token,$parstack,$safeeval,keys %key_defaults);
	if ($constructtag) {
	    $result = &Apache::edit::rebuild_tag($token);
	    $result.= &Apache::edit::handle_insert();
	}
    }
    return $result;
}

sub end_key {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}

##------------------------------------------------------------------- title
sub start_title {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	$title = &Apache::lonxml::get_all_text("/title",$$parser[-1]);
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_start($target,$token);
	my $text=&Apache::lonxml::get_all_text("/title",$$parser[-1]);
	$result.='</td></tr><tr><td colspan="3">'.
	    &Apache::edit::editfield('',$text,'',20,1).
	    &Apache::edit::end_table();
    } elsif ($target eq 'modified') {
	my $text=$$parser[-1]->get_text("/function");
	$result.=&Apache::edit::modifiedfield($token);
    }
    return $result;
}

sub end_title {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}
##------------------------------------------------------------------- xlabel
sub start_xlabel {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	$xlabel = &Apache::lonxml::get_all_text("/xlabel",$$parser[-1]);
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_start($target,$token);
	my $text=&Apache::lonxml::get_all_text("/xlabel",$$parser[-1]);
	$result.='</td></tr><tr><td colspan="3">'.
	    &Apache::edit::editfield('',$text,'',20,1).
	    &Apache::edit::end_table();
    } elsif ($target eq 'modified') {
	my $text=$$parser[-1]->get_text("/function");
	$result.=&Apache::edit::modifiedfield($token);
    }
    return $result;
}

sub end_xlabel {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}

##------------------------------------------------------------------- ylabel
sub start_ylabel {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	$ylabel = &Apache::lonxml::get_all_text("/ylabel",$$parser[-1]);
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	my $text = &Apache::lonxml::get_all_text("/ylabel",$$parser[-1]);
	$result .= '</td></tr><tr><td colspan="3">'.
	    &Apache::edit::editfield('',$text,'',20,1).
	    &Apache::edit::end_table();
    } elsif ($target eq 'modified') {
	my $text=$$parser[-1]->get_text("/function");
	$result.=&Apache::edit::modifiedfield($token);
    }
    return $result;
}

sub end_ylabel {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}

##------------------------------------------------------------------- label
sub start_label {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	my %label;
	&get_attributes(\%label,\%label_defaults,$parstack,$safeeval,
		    $tagstack->[-1]);
	$label{'text'} = &Apache::lonxml::get_all_text("/label",$$parser[-1]);
	if (! &$words_test($label{'text'})) {
	    # I should probably warn about it, too.
	    $label{'text'} = 'Illegal text';
	}
	push(@labels,\%label);
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	$result .= &edit_attributes($target,$token,\%label_defaults);
	my $text = &Apache::lonxml::get_all_text("/label",$$parser[-1]);
	$result .= '</td></tr><tr><td colspan="3">'.
	    &Apache::edit::editfield('',$text,'',20,1).
	    &Apache::edit::end_table();
    } elsif ($target eq 'modified') {
	my $constructtag=&Apache::edit::get_new_args
	    ($token,$parstack,$safeeval,keys %label_defaults);
	if ($constructtag) {
	    $result = &Apache::edit::rebuild_tag($token);
	    $result.= &Apache::edit::handle_insert();
	}
	my $text=$$parser[-1]->get_text("/label");
	$result.=&Apache::edit::modifiedfield($token);
    }
    return $result;
}

sub end_label {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}

##------------------------------------------------------------------- curve
sub start_curve {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	my %curve;
	&get_attributes(\%curve,\%curve_defaults,$parstack,$safeeval,
		    $tagstack->[-1]);
	push (@curves,\%curve);
	&Apache::lonxml::register('Apache::lonplot',('function','data'));
	push (@Apache::lonxml::namespace,'curve');
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	$result .= &edit_attributes($target,$token,\%curve_defaults);
    } elsif ($target eq 'modified') {
	my $constructtag=&Apache::edit::get_new_args
	    ($token,$parstack,$safeeval,keys %label_defaults);
	if ($constructtag) {
	    $result = &Apache::edit::rebuild_tag($token);
	    $result.= &Apache::edit::handle_insert();
	}
    }
    return $result;
}

sub end_curve {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
	pop @Apache::lonxml::namespace;
	&Apache::lonxml::deregister('Apache::lonplot',('function','data'));
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    }
    return $result;
}

##------------------------------------------------------------ curve function
sub start_function {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	if (exists($curves[-1]->{'data'})) {
	    &Apache::lonxml::warning('Use of <function> precludes use of <data>.  The <data> will be omitted in favor of the <function> declaration.');
	    delete $curves[-1]->{'data'} ;
	}
	$curves[-1]->{'function'} = 
	    &Apache::lonxml::get_all_text("/function",$$parser[-1]);
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	my $text = &Apache::lonxml::get_all_text("/function",$$parser[-1]);
	$result .= '</td></tr><tr><td colspan="3">'.
	    &Apache::edit::editfield('',$text,'',20,1).
	    &Apache::edit::end_table();

    } elsif ($target eq 'modified') {
	# Why do I do this?
	my $text=$$parser[-1]->get_text("/function");
	$result.=&Apache::edit::modifiedfield($token);
    }
    return $result;
}

sub end_function {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
    }
    return $result;
}

##------------------------------------------------------------ curve  data
sub start_data {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	if (exists($curves[-1]->{'function'})) {
	    &Apache::lonxml::warning('Use of <data> precludes use of .'.
	    '<function>.  The <function> will be omitted in favor of '.
            'the <data> declaration.');
	    delete($curves[-1]->{'function'});
	}
	my $datatext = &Apache::lonxml::get_all_text("/data",$$parser[-1]);
	$datatext =~ s/\s+/ /g;  
	# Need to do some error checking on the @data array - 
	# make sure it's all numbers and make sure each array 
	# is of the same length.
	my @data;
	if ($datatext =~ /,/) {
	    @data = split /,/,$datatext;
	} else { # Assume it's space seperated.
	    @data = split / /,$datatext;
	}
	for (my $i=0;$i<=$#data;$i++) {
	    # Check that it's non-empty
	    if (! defined($data[$i])) {
		&Apache::lonxml::warning(
		    'undefined <data> value.  Replacing with '.
		    ' pi/e = 1.15572734979092');
		$data[$i] = 1.15572734979092;
	    }
	    # Check that it's a number
	    if (! &$real_test($data[$i]) & ! &$int_test($data[$i])) {
		&Apache::lonxml::warning(
		    'Bad <data> value of '.$data[$i].'  Replacing with '.
		    ' pi/e = 1.15572734979092');
		$data[$i] = 1.15572734979092;
	    }
	}
	push  @{$curves[-1]->{'data'}},\@data;
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	my $text = &Apache::lonxml::get_all_text("/data",$$parser[-1]);
	$result .= '</td></tr><tr><td colspan="3">'.
	    &Apache::edit::editfield('',$text,'',20,1).
	    &Apache::edit::end_table();
    } elsif ($target eq 'modified') {
	my $text=$$parser[-1]->get_text("/data");
	$result.=&Apache::edit::modifiedfield($token);
    }
    return $result;
}

sub end_data {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
    }
    return $result;
}

##------------------------------------------------------------------- axis
sub start_axis {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result='';
    if ($target eq 'web') {
	&get_attributes(\%axis,\%axis_defaults,$parstack,$safeeval,
			$tagstack->[-1]);
    } elsif ($target eq 'edit') {
	$result .= &Apache::edit::tag_start($target,$token);
	$result .= &edit_attributes($target,$token,\%axis_defaults);
    } elsif ($target eq 'modified') {
    }
    return $result;
}

sub end_axis {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    my $result = '';
    if ($target eq 'web') {
    } elsif ($target eq 'edit') {
	$result.=&Apache::edit::tag_end($target,$token);
    } elsif ($target eq 'modified') {
	my $constructtag=&Apache::edit::get_new_args
	    ($token,$parstack,$safeeval,keys %axis_defaults);
	if ($constructtag) {
	    $result = &Apache::edit::rebuild_tag($token);
	    $result.= &Apache::edit::handle_insert();
	}
    }
    return $result;
}

###################################################################
##                                                               ##
##        Utility Functions                                      ##
##                                                               ##
###################################################################

##----------------------------------------------------------- set_defaults
sub set_defaults {
    my ($var,$defaults) = @_;
    my $key;
    foreach $key (keys %$defaults) {
	$var->{$key} = $defaults->{$key}->{'default'};
    }
}

##------------------------------------------------------------------- misc
sub get_attributes{
    my ($values,$defaults,$parstack,$safeeval,$tag) = @_;
    foreach my $attr (keys %{$defaults}) {
	$values->{$attr} = 
	    &Apache::lonxml::get_param($attr,$parstack,$safeeval);
	if ($values->{$attr} eq '' | !defined($values->{$attr})) {
	    $values->{$attr} = $defaults->{$attr}->{'default'};
	    next;
	}
	my $test = $defaults->{$attr}->{'test'};
	if (! &$test($values->{$attr})) {
	    &Apache::lonxml::warning
		($tag.':'.$attr.': Bad value.'.'Replacing your value with : '
		 .$defaults->{$attr}->{'default'} );
	    $values->{$attr} = $defaults->{$attr}->{'default'};
	}
    }
    return ;
}
##------------------------------------------------------- write_gnuplot_file
sub write_gnuplot_file {
    my $gnuplot_input = '';
    my $curve;
    # Collect all the colors
    my @Colors;
    push @Colors, $plot{'bgcolor'};
    push @Colors, $plot{'fgcolor'}; 
    push @Colors, (defined($axis{'color'})?$axis{'color'}:$plot{'fgcolor'});
    foreach $curve (@curves) {
	push @Colors, ($curve->{'color'} ne '' ? 
		       $curve->{'color'}       : 
		       $plot{'fgcolor'}        );
    }
    # set term
    $gnuplot_input .= 'set term gif ';
    $gnuplot_input .= 'transparent ' if ($plot{'transparent'} eq 'on');
    $gnuplot_input .= $plot{'font'} . ' ';
    $gnuplot_input .= 'size '.$plot{'width'}.','.$plot{'height'}.' ';
    $gnuplot_input .= "@Colors\n";
    # grid
    $gnuplot_input .= 'set grid'.$/ if ($plot{'grid'} eq 'on');
    # border
    $gnuplot_input .= ($plot{'border'} eq 'on'?
		       'set border'.$/           :
		       'set noborder'.$/         );    # title, xlabel, ylabel
    $gnuplot_input .= "set output\n";
    $gnuplot_input .= "set title  \"$title\"\n"  if (defined($title)) ;
    $gnuplot_input .= "set xlabel \"$xlabel\"\n" if (defined($xlabel));
    $gnuplot_input .= "set ylabel \"$ylabel\"\n" if (defined($ylabel));
    if (defined(%axis)) {
	$gnuplot_input .= "set xrange \[$axis{'xmin'}:$axis{'xmax'}\]\n";
	$gnuplot_input .= "set yrange \[$axis{'ymin'}:$axis{'ymax'}\]\n";
    }
    # Key
    if (defined(%key)) {
	$gnuplot_input .= 'set key '.$key{'pos'}.' ';
	if ($key{'title'} ne '') {
	    $gnuplot_input .= 'title "'.$key{'title'}.'" ';
	} 
	$gnuplot_input .= ($key{'box'} eq 'on' ? 'box ' : 'nobox ').$/;
    } else {
	$gnuplot_input .= 'set nokey'.$/;
    }
    # labels
    my $label;
    foreach $label (@labels) {
	$gnuplot_input .= 'set label "'.$label->{'text'}.'" at '.
	    $label->{'xpos'}.','.$label->{'ypos'}.' '.$label->{'justify'}.$/ ;
    }
    # curves
    $gnuplot_input .= 'plot ';
    my $datatext = '';
    for (my $i = 0;$i<=$#curves;$i++) {
	$curve = $curves[$i];
	$gnuplot_input.= ', ' if ($i > 0);
	if (exists($curve->{'function'})) {
	    $gnuplot_input.= 
		$curve->{'function'}.' title "'.
		$curve->{'name'}.'" with '.
		$curve->{'linestyle'};
	} elsif (exists($curve->{'data'})) {
	    $gnuplot_input.= '\'-\' title "'.
		$curve->{'name'}.'" with '.
		$curve->{'linestyle'};
	    my @Data = @{$curve->{'data'}};
	    my @Data0 = @{$Data[0]};
	    for (my $i =0; $i<=$#Data0; $i++) {
		my $dataset;
		foreach $dataset (@Data) {
		    $datatext .= $dataset->[$i] . ' ';
		}
		$datatext .= $/;
	    }
	    $datatext .=$/;
	}
    }
    $gnuplot_input .= $/.$datatext;
    return $gnuplot_input;
}

#---------------------------------------------- check_inputs
sub check_inputs {
    ## Note: no inputs, no outputs - this acts only on global variables.
    ## Make sure we have all the input we need:
    if (! defined(%plot  )) { &set_defaults(\%plot,\%plot_defaults); }
    if (! defined(%key   )) {} # No key for this plot, thats okay
    if (! defined(%axis  )) { &set_defaults(\%axis,\%axis_defaults); }
    if (! defined($title )) {} # No title for this plot, thats okay
    if (! defined($xlabel)) {} # No xlabel for this plot, thats okay
    if (! defined($ylabel)) {} # No ylabel for this plot, thats okay
    if ($#labels < 0) { }      # No labels for this plot, thats okay
    if ($#curves < 0) { 
	&Apache::lonxml::warning("No curves specified for plot!!!!");
	return '';
    }
    my $curve;
    foreach $curve (@curves) {
	if (!defined($curve->{'function'})&&!defined($curve->{'data'})){
	    &Apache::lonxml::warning("One of the curves specified did not contain any <data> or <function> declarations\n");
	    return '';
	}
    }
}

#------------------------------------------------ make_edit
sub edit_attributes {
    my ($target,$token,$defaults) = @_;
    my $result;
    foreach my $attr (%$defaults) {
	if ($defaults->{$attr}->{'edit_type'} eq 'entry') {
	    $result .= &Apache::edit::text_arg(
                 $defaults->{$attr}->{'description'},
		 $attr,
		 $token);
	} elsif ($defaults->{$attr}->{'edit_type'} eq 'choice') {
	    $result .= &Apache::edit::select_arg(
		 $defaults->{$attr}->{'description'},
		 $attr,
		 $defaults->{$attr}->{'choices'},
		 $token);
	}
    }
    return $result;
}


###################################################################
##                                                               ##
##           Insertion functions for editing plots               ##
##                                                               ##
###################################################################

#------------------------------------------------ insert_xxxxxxx
sub insert_plot {
    my $result;
    #  plot attributes
    $result .= '<plot ';
    foreach my $attr (%plot_defaults) {
	$result .= '     '.$attr.' "'.$plot_defaults{$attr}->{'default'}.
	    "\"\n";
    }
    $result .= ">\n";
    # Add the components
    $result .= &insert_key();
    $result .= &insert_axis();
    $result .= &insert_label();    
    $result .= &insert_curve();
    $result .= &insert_function();    
    $result .= "</curve>\n";
    $result .= &insert_curve();
    $result .= &insert_data();    
    $result .= "</curve>\n";
    # close up the <plot>
    $result .= "</plot>\n";
    return $result;
}

sub insert_key {
    my $result;
    $result .= '    <key ';
    foreach my $attr (%key_defaults) {
	$result .= '         '.$attr.' "'.$key_defaults{$attr}->{'default'}.
	    "\"\n";
    }
    $result .= "   />\n";
    return $result;
}

sub insert_axis{
    my $result;
    $result .= '    <axis ';
    foreach my $attr (%axis_defaults) {
	$result .= '         '.$attr.' "'.$axis_defaults{$attr}->{'default'}.
	    "\"\n";
    }
    $result .= "   />\n";
    return $result;
}

sub insert_label {
    my $result;
    $result .= '    <label ';
    foreach my $attr (%label_defaults) {
	$result .= '         '.$attr.' "'.
	    $label_defaults{$attr}->{'default'}."\"\n";
    }
    $result .= "   ></label>\n";
    return $result;
}

sub insert_curve {
    my $result;
    $result .= '    <curve ';
    foreach my $attr (%curve_defaults) {
	$result .= '         '.$attr.' "'.
	    $curve_defaults{$attr}->{'default'}."\"\n";
    }
    $result .= "    >\n";
}

sub insert_function {
    my $result;
    $result .= "<function></function>\n";
    return $result;
}

sub insert_data {
    my $result;
    $result .= "     <data></data>\n";
    $result .= "     <data></data>\n";
    return $result;
}

##----------------------------------------------------------------------
1;
__END__