# The LearningOnline Network with CAPA
# .helper XML handler to implement the LON-CAPA helper
#
# $Id: lonhelper.pm,v 1.6 2003/04/11 17:21:18 bowersj2 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/
#
# (Page Handler
#
# (.helper handler
#

# FIXME: Change register calls to register with the helper.
# Then have the helper reg and unreg the tags.
# This removes my concerns about breaking other code.

=pod

=head1 lonhelper - HTML Helper framework for LON-CAPA

Helpers, often known as "wizards", are well-established UI widgets that users
feel comfortable with. It can take a complicated multidimensional problem the
user has and turn it into a series of bite-sized one-dimensional questions.

For developers, helpers provide an easy way to bundle little bits of functionality
for the user, without having to write the tedious state-maintenence code.

Helpers are defined as XML documents, placed in the /home/httpd/html/adm/helpers 
directory and having the .helper file extension. For examples, see that directory.

All classes are in the Apache::lonhelper namespace.

=head2 lonhelper XML file format

A helper consists of a top-level <helper> tag which contains a series of states.
Each state contains one or more state elements, which are what the user sees, like
messages, resource selections, or date queries.

The helper tag is required to have one attribute, "title", which is the name
of the helper itself, such as "Parameter helper". 

=head2 State tags

State tags are required to have an attribute "name", which is the symbolic
name of the state and will not be directly seen by the user. The wizard is
required to have one state named "START", which is the state the wizard
will start with. By convention, this state should clearly describe what
the helper will do for the user, and may also include the first information
entry the user needs to do for the helper.

State tags are also required to have an attribute "title", which is the
human name of the state, and will be displayed as the header on top of 
the screen for the user.

=head2 Example Helper Skeleton

An example of the tags so far:

 <helper title="Example Helper">
   <state name="START" title="Demonstrating the Example Helper">
     <!-- notice this is the START state the wizard requires -->
     </state>
   <state name="GET_NAME" title="Enter Student Name">
     </state>
   </helper>

Of course this does nothing. In order for the wizard to do something, it is
necessary to put actual elements into the wizard. Documentation for each
of these elements follows.

=cut

package Apache::lonhelper;
use Apache::Constants qw(:common);
use Apache::File;
use Apache::lonxml;

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper', 
                              ('helper', 'state'));
}

# Since all wizards are only three levels deep (wizard tag, state tag, 
# substate type), it's easier and more readble to explicitly track 
# those three things directly, rather then futz with the tag stack 
# every time.
my $helper;
my $state;
my $substate;
# To collect parameters, the contents of the subtags are collected
# into this paramHash, then passed to the element object when the 
# end of the element tag is located.
my $paramHash; 

sub handler {
    my $r = shift;
    $ENV{'request.uri'} = $r->uri();
    my $filename = '/home/httpd/html' . $r->uri();
    my $fh = Apache::File->new($filename);
    my $file;
    read $fh, $file, 100000000;

    Apache::loncommon::get_unprocessed_cgi($ENV{QUERY_STRING});

    # Send header, don't cache this page
    if ($r->header_only) {
        if ($ENV{'browser.mathml'}) {
            $r->content_type('text/xml');
        } else {
            $r->content_type('text/html');
        }
        $r->send_http_header;
        return OK;
    }
    if ($ENV{'browser.mathml'}) {
        $r->content_type('text/xml');
    } else {
        $r->content_type('text/html');
    }
    $r->send_http_header;
    $r->rflush();

    # Discard result, we just want the objects that get created by the
    # xml parsing
    &Apache::lonxml::xmlparse($r, 'helper', $file);

    $r->print($helper->display());
    return OK;
}

sub start_helper {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    
    $helper = Apache::lonhelper::helper->new($token->[2]{'title'});
    return '';
}

sub end_helper {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
    
    if ($target ne 'helper') {
        return '';
    }
    
    return '';
}

sub start_state {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    $state = Apache::lonhelper::state->new($token->[2]{'name'},
                                           $token->[2]{'title'});
    return '';
}

# don't need this, so ignore it
sub end_state {
    return '';
}

1;

package Apache::lonhelper::helper;

use Digest::MD5 qw(md5_hex);
use HTML::Entities;
use Apache::loncommon;
use Apache::File;

sub new {
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = {};

    $self->{TITLE} = shift;
    
    # If there is a state from the previous form, use that. If there is no
    # state, use the start state parameter.
    if (defined $ENV{"form.CURRENT_STATE"})
    {
	$self->{STATE} = $ENV{"form.CURRENT_STATE"};
    }
    else
    {
	$self->{STATE} = "START";
    }

    $self->{TOKEN} = $ENV{'form.TOKEN'};
    # If a token was passed, we load that in. Otherwise, we need to create a 
    # new storage file
    # Tried to use standard Tie'd hashes, but you can't seem to take a 
    # reference to a tied hash and write to it. I'd call that a wart.
    if ($self->{TOKEN}) {
        # Validate the token before trusting it
        if ($self->{TOKEN} !~ /^[a-f0-9]{32}$/) {
            # Not legit. Return nothing and let all hell break loose.
            # User shouldn't be doing that!
            return undef;
        }

        # Get the hash.
        $self->{FILENAME} = $Apache::lonnet::tmpdir . md5_hex($self->{TOKEN}); # Note the token is not the literal file
        
        my $file = Apache::File->new($self->{FILENAME});
        my $contents = <$file>;

        # Now load in the contents
        for my $value (split (/&/, $contents)) {
            my ($name, $value) = split(/=/, $value);
            $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
            $self->{VARS}->{$name} = $value;
        }

        $file->close();
    } else {
        # Only valid if we're just starting.
        if ($self->{STATE} ne 'START') {
            return undef;
        }
        # Must create the storage
        $self->{TOKEN} = md5_hex($ENV{'user.name'} . $ENV{'user.domain'} .
                                 time() . rand());
        $self->{FILENAME} = $Apache::lonnet::tmpdir . md5_hex($self->{TOKEN});
    }

    # OK, we now have our persistent storage.

    if (defined $ENV{"form.RETURN_PAGE"})
    {
	$self->{RETURN_PAGE} = $ENV{"form.RETURN_PAGE"};
    }
    else
    {
	$self->{RETURN_PAGE} = $ENV{REFERER};
    }

    $self->{STATES} = {};
    $self->{DONE} = 0;

    bless($self, $class);
    return $self;
}

# Private function; returns a string to construct the hidden fields
# necessary to have the helper track state.
sub _saveVars {
    my $self = shift;
    my $result = "";
    $result .= '<input type="hidden" name="CURRENT_STATE" value="' .
        HTML::Entities::encode($self->{STATE}) . "\" />\n";
    $result .= '<input type="hidden" name="TOKEN" value="' .
        $self->{TOKEN} . "\" />\n";
    $result .= '<input type="hidden" name="RETURN_PAGE" value="' .
        HTML::Entities::encode($self->{RETURN_PAGE}) . "\" />\n";

    return $result;
}

# Private function: Create the querystring-like representation of the stored
# data to write to disk.
sub _varsInFile {
    my $self = shift;
    my @vars = ();
    for my $key (keys %{$self->{VARS}}) {
        push @vars, &Apache::lonnet::escape($key) . '=' .
            &Apache::lonnet::escape($self->{VARS}->{$key});
    }
    return join ('&', @vars);
}

# Use this to declare variables.
# FIXME: Document this
sub declareVar {
    my $self = shift;
    my $var = shift;

    if (!defined($self->{VARS}->{$var})) {
        $self->{VARS}->{$var} = '';
    }

    my $envname = 'form.' . $var . '.forminput';
    if (defined($ENV{$envname})) {
        $self->{VARS}->{$var} = $ENV{$envname};
    }
}

sub changeState {
    my $self = shift;
    $self->{STATE} = shift;
}

sub registerState {
    my $self = shift;
    my $state = shift;

    my $stateName = $state->name();
    $self->{STATES}{$stateName} = $state;
}

# Done in four phases
# 1: Do the post processing for the previous state.
# 2: Do the preprocessing for the current state.
# 3: Check to see if state changed, if so, postprocess current and move to next.
#    Repeat until state stays stable.
# 4: Render the current state to the screen as an HTML page.
sub display {
    my $self = shift;

    my $result = "";

    # Phase 1: Post processing for state of previous screen (which is actually
    # the "current state" in terms of the helper variables), if it wasn't the 
    # beginning state.
    if ($self->{STATE} ne "START" || $ENV{"form.SUBMIT"} eq "Next ->") {
	my $prevState = $self->{STATES}{$self->{STATE}};
            $prevState->postprocess();
    }
    
    # Note, to handle errors in a state's input that a user must correct,
    # do not transition in the postprocess, and force the user to correct
    # the error.

    # Phase 2: Preprocess current state
    my $startState = $self->{STATE};
    my $state = $self->{STATES}{$startState};
    
    # Error checking; it is intended that the developer will have
    # checked all paths and the user can't see this!
    if (!defined($state)) {
        $result .="Error! The state ". $startState ." is not defined.";
        return $result;
    }
    $state->preprocess();

    # Phase 3: While the current state is different from the previous state,
    # keep processing.
    while ( $startState ne $self->{STATE} )
    {
	$startState = $self->{STATE};
	$state = $self->{STATES}{$startState};
	$state->preprocess();
    }

    # Phase 4: Display.
    my $stateTitle = $state->title();
    my $bodytag = &Apache::loncommon::bodytag("$self->{TITLE}",'','');

    $result .= <<HEADER;
<html>
    <head>
        <title>LON-CAPA Helper: $self->{TITLE}</title>
    </head>
    $bodytag
HEADER
    if (!$state->overrideForm()) { $result.="<form name='wizform' method='GET'>"; }
    $result .= <<HEADER;
        <table border="0"><tr><td>
        <h2><i>$stateTitle</i></h2>
HEADER

    if (!$state->overrideForm()) {
        $result .= $self->_saveVars();
    }
    $result .= $state->render() . "<p>&nbsp;</p>";

    if (!$state->overrideForm()) {
        $result .= '<center>';
        if ($self->{STATE} ne $self->{START_STATE}) {
            #$result .= '<input name="SUBMIT" type="submit" value="&lt;- Previous" />&nbsp;&nbsp;';
        }
        if ($self->{DONE}) {
            my $returnPage = $self->{RETURN_PAGE};
            $result .= "<a href=\"$returnPage\">End Helper</a>";
        }
        else {
            $result .= '<input name="back" type="button" ';
            $result .= 'value="&lt;- Previous" onclick="history.go(-1)" /> ';
            $result .= '<input name="SUBMIT" type="submit" value="Next -&gt;" />';
        }
        $result .= "</center>\n";
    }

    foreach my $key (keys %{$self->{VARS}}) {
        $result .= "|$key| -> " . $self->{VARS}->{$key} . "<br />";
    }

    $result .= <<FOOTER;
              </td>
            </tr>
          </table>
        </form>
    </body>
</html>
FOOTER

    # Handle writing out the vars to the file
    my $file = Apache::File->new('>'.$self->{FILENAME});
    print $file $self->_varsInFile();

    return $result;
}

1;

package Apache::lonhelper::state;

# States bundle things together and are responsible for compositing the
# various elements together. It is not generally necessary for users to
# use the state object directly, so it is not perldoc'ed.

# Basically, all the states do is pass calls to the elements and aggregate
# the results.

sub new {
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = {};

    $self->{NAME} = shift;
    $self->{TITLE} = shift;
    $self->{ELEMENTS} = [];

    bless($self, $class);

    $helper->registerState($self);

    return $self;
}

sub name {
    my $self = shift;
    return $self->{NAME};
}

sub title {
    my $self = shift;
    return $self->{TITLE};
}

sub preprocess {
    my $self = shift;
    for my $element (@{$self->{ELEMENTS}}) {
        $element->preprocess();
    }
}

# FIXME: Document that all postprocesses must return a true value or
# the state transition will be overridden
sub postprocess {
    my $self = shift;

    # Save the state so we can roll it back if we need to.
    my $originalState = $helper->{STATE};
    my $everythingSuccessful = 1;

    for my $element (@{$self->{ELEMENTS}}) {
        my $result = $element->postprocess();
        if (!$result) { $everythingSuccessful = 0; }
    }

    # If not all the postprocesses were successful, override
    # any state transitions that may have occurred. It is the
    # responsibility of the states to make sure they have 
    # error handling in that case.
    if (!$everythingSuccessful) {
        $helper->{STATE} = $originalState;
    }
}

sub overrideForm {
    return 0;
}

sub addElement {
    my $self = shift;
    my $element = shift;
    
    push @{$self->{ELEMENTS}}, $element;
}

sub render {
    my $self = shift;
    my @results = ();

    for my $element (@{$self->{ELEMENTS}}) {
        push @results, $element->render();
    }
    return join("\n", @results);
}

1;

package Apache::lonhelper::element;
# Support code for elements

=pod

=head2 Element Base Class

The Apache::lonhelper::element base class provides support methods for
the elements to use, such as a multiple value processer.

B<Methods>:

=over 4

=item * process_multiple_choices(formName, varName): Process the form 
element named "formName" and place the selected items into the helper 
variable named varName. This is for things like checkboxes or 
multiple-selection listboxes where the user can select more then 
one entry. The selected entries are delimited by triple pipes in 
the helper variables, like this:  

 CHOICE_1|||CHOICE_2|||CHOICE_3

=back

=cut

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::element',
                              ('nextstate'));
}

# Because we use the param hash, this is often a sufficent
# constructor
sub new {
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = $paramHash;
    bless($self, $class);

    $self->{PARAMS} = $paramHash;
    $self->{STATE} = $state;
    $state->addElement($self);
    
    # Ensure param hash is not reused
    $paramHash = {};

    return $self;
}   

sub start_nextstate {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    
    $paramHash->{NEXTSTATE} = &Apache::lonxml::get_all_text('/nextstate',
                                                             $parser);
    return '';
}

sub end_nextstate { return ''; }

sub preprocess {
    return 1;
}

sub postprocess {
    return 1;
}

sub render {
    return '';
}

sub process_multiple_choices {
    my $self = shift;
    my $formname = shift;
    my $var = shift;

    my $formvalue = $ENV{'form.' . $formname};
    if ($formvalue) {
        # Must extract values from querystring directly, as there
        # may be more then one.
        my @values;
        for my $formparam (split (/&/, $ENV{QUERY_STRING})) {
            my ($name, $value) = split(/=/, $formparam);
            if ($name ne $formname) {
                next;
            }
            $value =~ tr/+/ /;
            $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
            push @values, $value;
        }
        $helper->{VARS}->{$var} = join('|||', @values);
    }
    
    return;
}

1;

package Apache::lonhelper::message;

=pod

=head2 Element: message

Message elements display the contents of their <message_text> tags, and
transition directly to the state in the <nextstate> tag. Example:

 <message>
   <nextstate>GET_NAME</nextstate>
   <message_text>This is the <b>message</b> the user will see, 
                 <i>HTML allowed</i>.</message_text>
   </message>

This will display the HTML message and transition to the <nextstate> if
given. The HTML will be directly inserted into the wizard, so if you don't
want text to run together, you'll need to manually wrap the <message_text>
in <p> tags, or whatever is appropriate for your HTML.

Message tags do not add in whitespace, so if you want it, you'll need to add
it into states. This is done so you can inline some elements, such as 
the <date> element, right between two messages, giving the appearence that 
the <date> element appears inline. (Note the elements can not be embedded
within each other.)

This is also a good template for creating your own new states, as it has
very little code beyond the state template.

=cut

no strict;
@ISA = ("Apache::lonhelper::element");
use strict;

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::message',
                              ('message', 'message_text'));
}

sub new {
    my $ref = Apache::lonhelper::element->new();
    bless($ref);
}

# CONSTRUCTION: Construct the message element from the XML
sub start_message {
    return '';
}

sub end_message {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    Apache::lonhelper::message->new();
    return '';
}

sub start_message_text {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    $paramHash->{MESSAGE_TEXT} = &Apache::lonxml::get_all_text('/message_text',
                                                               $parser);
}
    
sub end_message_text { return 1; }

sub render {
    my $self = shift;

    return $self->{MESSAGE_TEXT};
}
# If a NEXTSTATE was given, switch to it
sub postprocess {
    my $self = shift;
    if (defined($self->{NEXTSTATE})) {
        $helper->changeState($self->{NEXTSTATE});
    }

    return 1;
}
1;

package Apache::lonhelper::choices;

=pod

=head2 Element: choices

Choice states provide a single choice to the user as a text selection box.
A "choice" is two pieces of text, one which will be displayed to the user
(the "human" value), and one which will be passed back to the program
(the "computer" value). For instance, a human may choose from a list of
resources on disk by title, while your program wants the file name.

<choices> takes an attribute "variable" to control which helper variable
the result is stored in.

<choices> takes an attribute "multichoice" which, if set to a true
value, will allow the user to select multiple choices.

B<SUB-TAGS>

<choices> can have the following subtags:

=over 4

=item * <nextstate>state_name</nextstate>: If given, this will cause the
      choice element to transition to the given state after executing. If
      this is used, do not pass nextstates to the <choice> tag.

=item * <choice />: If the choices are static,
      this element will allow you to specify them. Each choice
      contains  attribute, "computer", as described above. The
      content of the tag will be used as the human label.
      For example,  
      <choice computer='234-12-7312'>Bobby McDormik</choice>.

<choice> may optionally contain a 'nextstate' attribute, which
will be the state transisitoned to if the choice is made, if
the choice is not multichoice.

=back

To create the choices programmatically, either wrap the choices in 
<condition> tags (prefered), or use an <exec> block inside the <choice>
tag. Store the choices in $state->{CHOICES}, which is a list of list
references, where each list has three strings. The first is the human
name, the second is the computer name. and the third is the option
next state. For example:

 <exec>
    for (my $i = 65; $i < 65 + 26; $i++) {
        push @{$state->{CHOICES}}, [chr($i), $i, 'next'];
    }
 </exec>

This will allow the user to select from the letters A-Z (in ASCII), while
passing the ASCII value back into the helper variables, and the state
will in all cases transition to 'next'.

You can mix and match methods of creating choices, as long as you always 
"push" onto the choice list, rather then wiping it out. (You can even 
remove choices programmatically, but that would probably be bad form.)

FIXME: Document and implement <exec> and <condition> in the element package.

=cut

no strict;
@ISA = ("Apache::lonhelper::element");
use strict;

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::choices',
                              ('choice', 'choices'));
}

sub new {
    my $ref = Apache::lonhelper::element->new();
    bless($ref);
}

# CONSTRUCTION: Construct the message element from the XML
sub start_choices {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    # Need to initialize the choices list, so everything can assume it exists
    $paramHash->{'variable'} = $token->[2]{'variable'};
    $helper->declareVar($paramHash->{'variable'});
    $paramHash->{'multichoice'} = $token->[2]{'multichoice'};
    $paramHash->{CHOICES} = [];
    return '';
}

sub end_choices {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    Apache::lonhelper::choices->new();
    return '';
}

sub start_choice {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    my $computer = $token->[2]{'computer'};
    my $human = &Apache::lonxml::get_all_text('/choice',
                                              $parser);
    my $nextstate = $token->[2]{'nextstate'};
    push @{$paramHash->{CHOICES}}, [$human, $computer, $nextstate];
    return '';
}

sub end_choice {
    return '';
}

sub render {
    # START HERE: Replace this with correct choices code.
    my $self = shift;
    my $var = $self->{'variable'};
    my $buttons = '';
    my $result = '';

    if ($self->{'multichoice'}) {
        $result .= <<SCRIPT;
<script>
    function checkall(value) {
	for (i=0; i<document.forms.wizform.elements.length; i++) {
            document.forms.wizform.elements[i].checked=value;
        }
    }
</script>
SCRIPT
        $buttons = <<BUTTONS;
<br />
<input type="button" onclick="checkall(true)" value="Select All" />
<input type="button" onclick="checkall(false)" value="Unselect All" />
<br />&nbsp;
BUTTONS
    }

    if (defined $self->{ERROR_MSG}) {
        $result .= '<br /><font color="#FF0000">' . $self->{ERROR_MSG} . '</font><br />';
    }

    $result .= $buttons;
    
    $result .= "<table>\n\n";

    my $type = "radio";
    if ($self->{'multichoice'}) { $type = 'checkbox'; }
    my $checked = 0;
    foreach my $choice (@{$self->{CHOICES}}) {
        $result .= "<tr>\n<td width='20'>&nbsp;</td>\n";
        $result .= "<td valign='top'><input type='$type' name='$var.forminput'"
            . "' value='" . 
            HTML::Entities::encode($choice->[1]) 
            . "'";
        if (!$self->{'multichoice'} && !$checked) {
            $result .= " checked ";
            $checked = 1;
        }
        $result .= "/></td><td> " . $choice->[0] . "</td></tr>\n";
    }
    $result .= "</table>\n\n\n";
    $result .= $buttons;

    return $result;
}

# If a NEXTSTATE was given or a nextstate for this choice was
# given, switch to it
sub postprocess {
    my $self = shift;
    my $chosenValue = $ENV{'form.' . $self->{'variable'} . '.forminput'};

    if (!$chosenValue) {
        $self->{ERROR_MSG} = "You must choose one or more choices to" .
            " continue.";
        return 0;
    }

    if ($self->{'multichoice'}) {
        $self->process_multiple_choices($self->{'variable'}.'.forminput',
                                        $self->{'variable'});
    }

    if (defined($self->{NEXTSTATE})) {
        $helper->changeState($self->{NEXTSTATE});
    }
    
    foreach my $choice (@{$self->{CHOICES}}) {
        if ($choice->[1] eq $chosenValue) {
            if (defined($choice->[2])) {
                $helper->changeState($choice->[2]);
            }
        }
    }
    return 1;
}
1;

package Apache::lonhelper::date;

=pod

=head2 Element: date

Date elements allow the selection of a date with a drop down list.

Date elements can take two attributes:

=over 4

=item * B<variable>: The name of the variable to store the chosen
        date in. Required.

=item * B<hoursminutes>: If a true value, the date will show hours
        and minutes, as well as month/day/year. If false or missing,
        the date will only show the month, day, and year.

=back

Date elements contain only an option <nextstate> tag to determine
the next state.

Example:

 <date variable="DUE_DATE" hoursminutes="1">
   <nextstate>choose_why</nextstate>
   </date>

=cut

no strict;
@ISA = ("Apache::lonhelper::element");
use strict;

use Time::localtime;

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::date',
                              ('date'));
}

# Don't need to override the "new" from element
sub new {
    my $ref = Apache::lonhelper::element->new();
    bless($ref);
}

my @months = ("January", "February", "March", "April", "May", "June", "July",
	      "August", "September", "October", "November", "December");

# CONSTRUCTION: Construct the message element from the XML
sub start_date {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    $paramHash->{'variable'} = $token->[2]{'variable'};
    $helper->declareVar($paramHash->{'variable'});
    $paramHash->{'hoursminutes'} = $token->[2]{'hoursminutes'};
}

sub end_date {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    Apache::lonhelper::date->new();
    return '';
}

sub render {
    my $self = shift;
    my $result = "";
    my $var = $self->{'variable'};

    my $date;
    
    # Default date: The current hour.
    $date = localtime();
    $date->min(0);

    if (defined $self->{ERROR_MSG}) {
        $result .= '<font color="#FF0000">' . $self->{ERROR_MSG} . '</font><br /><br />';
    }

    # Month
    my $i;
    $result .= "<select name='${var}month'>\n";
    for ($i = 0; $i < 12; $i++) {
        if ($i == $date->mon) {
            $result .= "<option value='$i' selected>";
        } else {
            $result .= "<option value='$i'>";
        }
        $result .= $months[$i] . "</option>\n";
    }
    $result .= "</select>\n";

    # Day
    $result .= "<select name='${var}day'>\n";
    for ($i = 1; $i < 32; $i++) {
        if ($i == $date->mday) {
            $result .= '<option selected>';
        } else {
            $result .= '<option>';
        }
        $result .= "$i</option>\n";
    }
    $result .= "</select>,\n";

    # Year
    $result .= "<select name='${var}year'>\n";
    for ($i = 2000; $i < 2030; $i++) { # update this after 64-bit dates
        if ($date->year + 1900 == $i) {
            $result .= "<option selected>";
        } else {
            $result .= "<option>";
        }
        $result .= "$i</option>\n";
    }
    $result .= "</select>,\n";

    # Display Hours and Minutes if they are called for
    if ($self->{'hoursminutes'}) {
        # Build hour
        $result .= "<select name='${var}hour'>\n";
        $result .= "<option " . ($date->hour == 0 ? 'selected ':'') .
            " value='0'>midnight</option>\n";
        for ($i = 1; $i < 12; $i++) {
            if ($date->hour == $i) {
                $result .= "<option selected value='$i'>$i a.m.</option>\n";
            } else {
                $result .= "<option value='$i'>$i a.m</option>\n";
            }
        }
        $result .= "<option " . ($date->hour == 12 ? 'selected ':'') .
            " value='12'>noon</option>\n";
        for ($i = 13; $i < 24; $i++) {
            my $printedHour = $i - 12;
            if ($date->hour == $i) {
                $result .= "<option selected value='$i'>$printedHour p.m.</option>\n";
            } else {
                $result .= "<option value='$i'>$printedHour p.m.</option>\n";
            }
        }

        $result .= "</select> :\n";

        $result .= "<select name='${var}minute'>\n";
        for ($i = 0; $i < 60; $i++) {
            my $printedMinute = $i;
            if ($i < 10) {
                $printedMinute = "0" . $printedMinute;
            }
            if ($date->min == $i) {
                $result .= "<option selected>";
            } else {
                $result .= "<option>";
            }
            $result .= "$printedMinute</option>\n";
        }
        $result .= "</select>\n";
    }

    return $result;

}
# If a NEXTSTATE was given, switch to it
sub postprocess {
    my $self = shift;
    my $var = $self->{'variable'};
    my $month = $ENV{'form.' . $var . 'month'}; 
    my $day = $ENV{'form.' . $var . 'day'}; 
    my $year = $ENV{'form.' . $var . 'year'}; 
    my $min = 0; 
    my $hour = 0;
    if ($self->{'hoursminutes'}) {
        $min = $ENV{'form.' . $var . 'minute'};
        $hour = $ENV{'form.' . $var . 'hour'};
    }

    my $chosenDate = Time::Local::timelocal(0, $min, $hour, $day, $month, $year);
    # Check to make sure that the date was not automatically co-erced into a 
    # valid date, as we want to flag that as an error
    # This happens for "Feb. 31", for instance, which is coerced to March 2 or
    # 3, depending on if it's a leapyear
    my $checkDate = localtime($chosenDate);

    if ($checkDate->mon != $month || $checkDate->mday != $day ||
        $checkDate->year + 1900 != $year) {
        $self->{ERROR_MSG} = "Can't use " . $months[$month] . " $day, $year as a "
            . "date because it doesn't exist. Please enter a valid date.";
        return 0;
    }

    $helper->{VARS}->{$var} = $chosenDate;

    if (defined($self->{NEXTSTATE})) {
        $helper->changeState($self->{NEXTSTATE});
    }

    return 1;
}
1;

package Apache::lonhelper::resource;

=pod

=head2 Element: resource

<resource> elements allow the user to select one or multiple resources
from the current course. You can filter out which resources they can view,
and filter out which resources they can select. The course will always
be displayed fully expanded, because of the difficulty of maintaining
selections across folder openings and closings. If this is fixed, then
the user can manipulate the folders.

<resource> takes the standard variable attribute to control what helper
variable stores the results. It also takes a "multichoice" attribute,
which controls whether the user can select more then one resource.

B<SUB-TAGS>

=over 4

=item * <filterfunc>: If you want to filter what resources are displayed
  to the user, use a filter func. The <filterfunc> tag should contain
  Perl code that when wrapped with "sub { my $res = shift; " and "}" is 
  a function that returns true if the resource should be displayed, 
  and false if it should be skipped. $res is a resource object. 
  (See Apache::lonnavmaps documentation for information about the 
  resource object.)

=item * <choicefunc>: Same as <filterfunc>, except that controls whether
  the given resource can be chosen. (It is almost always a good idea to
  show the user the folders, for instance, but you do not always want to 
  let the user select them.)

=item * <nextstate>: Standard nextstate behavior.

=item * <valuefunc>: This function controls what is returned by the resource
  when the user selects it. Like filterfunc and choicefunc, it should be
  a function fragment that when wrapped by "sub { my $res = shift; " and
  "}" returns a string representing what you want to have as the value. By
  default, the value will be the resource ID of the object ($res->{ID}).

=back

=cut

no strict;
@ISA = ("Apache::lonhelper::element");
use strict;

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::resource',
                              ('resource', 'filterfunc', 
                               'choicefunc', 'valuefunc'));
}

sub new {
    my $ref = Apache::lonhelper::element->new();
    bless($ref);
}

# CONSTRUCTION: Construct the message element from the XML
sub start_resource {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    $paramHash->{'variable'} = $token->[2]{'variable'};
    $helper->declareVar($paramHash->{'variable'});
    return '';
}

sub end_resource {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    if (!defined($paramHash->{FILTER_FUNC})) {
        $paramHash->{FILTER_FUNC} = sub {return 1;};
    }
    if (!defined($paramHash->{CHOICE_FUNC})) {
        $paramHash->{CHOICE_FUNC} = sub {return 1;};
    }
    if (!defined($paramHash->{VALUE_FUNC})) {
        $paramHash->{VALUE_FUNC} = sub {my $res = shift; return $res->{ID}; };
    }
    Apache::lonhelper::resource->new();
    return '';
}

sub start_filterfunc {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    my $contents = Apache::lonxml::get_all_text('/filterfunc',
                                                $parser);
    $contents = 'sub { my $res = shift; ' . $contents . '}';
    $paramHash->{FILTER_FUNC} = eval $contents;
}

sub end_filterfunc { return ''; }

sub start_choicefunc {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    my $contents = Apache::lonxml::get_all_text('/choicefunc',
                                                $parser);
    $contents = 'sub { my $res = shift; ' . $contents . '}';
    $paramHash->{CHOICE_FUNC} = eval $contents;
}

sub end_choicefunc { return ''; }

sub start_valuefunc {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    my $contents = Apache::lonxml::get_all_text('/valuefunc',
                                                $parser);
    $contents = 'sub { my $res = shift; ' . $contents . '}';
    $paramHash->{VALUE_FUNC} = eval $contents;
}

sub end_valuefunc { return ''; }

# A note, in case I don't get to this before I leave.
# If someone complains about the "Back" button returning them
# to the previous folder state, instead of returning them to
# the previous helper state, the *correct* answer is for the helper
# to keep track of how many times the user has manipulated the folders,
# and feed that to the history.go() call in the helper rendering routines.
# If done correctly, the helper itself can keep track of how many times
# it renders the same states, so it doesn't go in just this state, and
# you can lean on the browser back button to make sure it all chains
# correctly.
# Right now, though, I'm just forcing all folders open.

sub render {
    my $self = shift;
    my $result = "";
    my $var = $self->{'variable'};
    my $curVal = $helper->{VARS}->{$var};

    if (defined $self->{ERROR_MSG}) {
        $result .= '<font color="#FF0000">' . $self->{ERROR_MSG} . '</font><br /><br />';
    }

    my $filterFunc = $self->{FILTER_FUNC};
    my $choiceFunc = $self->{CHOICE_FUNC};
    my $valueFunc = $self->{VALUE_FUNC};

    # Create the composite function that renders the column on the nav map
    # have to admit any language that lets me do this can't be all bad
    #  - Jeremy (Pythonista) ;-)
    my $checked = 0;
    my $renderColFunc = sub {
        my ($resource, $part, $params) = @_;
        
        if (!&$choiceFunc($resource)) {
            return '<td>&nbsp;</td>';
        } else {
            my $col = "<td><input type='radio' name='${var}.forminput' ";
            if (!$checked) {
                $col .= "checked ";
                $checked = 1;
            }
            $col .= "value='" . 
                HTML::Entities::encode(&$valueFunc($resource)) 
                . "' /></td>";
            return $col;
        }
    };

    $ENV{'form.condition'} = 1;
    $result .= 
        &Apache::lonnavmaps::render( { 'cols' => [$renderColFunc, 
                                                  Apache::lonnavmaps::resource()],
                                       'showParts' => 0,
                                       'url' => $helper->{URL},
                                       'filterFunc' => $filterFunc,
                                       'resource_no_folder_link' => 1 }
                                       );
                                                
    return $result;
}
    
sub postprocess {
    my $self = shift;
    if (defined($self->{NEXTSTATE})) {
        $helper->changeState($self->{NEXTSTATE});
    }

    return 1;
}

1;

package Apache::lonhelper::student;

=pod

=head2 Element: student

Student elements display a choice of students enrolled in the current
course. Currently it is primitive; this is expected to evolve later.

Student elements take two attributes: "variable", which means what
it usually does, and "multichoice", which if true allows the user
to select multiple students.

=cut

no strict;
@ISA = ("Apache::lonhelper::element");
use strict;



BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::student',
                              ('student'));
}

sub new {
    my $ref = Apache::lonhelper::element->new();
    bless($ref);
}

sub start_student {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    $paramHash->{'variable'} = $token->[2]{'variable'};
    $helper->declareVar($paramHash->{'variable'});
    $paramHash->{'multichoice'} = $token->[2]{'multichoice'};
}    

sub end_student {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    Apache::lonhelper::student->new();
}

sub render {
    my $self = shift;
    my $result = '';
    my $buttons = '';

    if ($self->{'multichoice'}) {
        $result = <<SCRIPT;
<script>
    function checkall(value) {
	for (i=0; i<document.forms.wizform.elements.length; i++) {
            document.forms.wizform.elements[i].checked=value;
        }
    }
</script>
SCRIPT
        $buttons = <<BUTTONS;
<br />
<input type="button" onclick="checkall(true)" value="Select All" />
<input type="button" onclick="checkall(false)" value="Unselect All" />
<br />
BUTTONS
    }

    if (defined $self->{ERROR_MSG}) {
        $result .= '<font color="#FF0000">' . $self->{ERROR_MSG} . '</font><br /><br />';
    }

    # Load up the students
    my $choices = &Apache::loncoursedata::get_classlist();

    my @keys = keys %{$choices};

    # Constants
    my $section = Apache::loncoursedata::CL_SECTION();
    my $fullname = Apache::loncoursedata::CL_FULLNAME();

    # Sort by: Section, name
    @keys = sort {
        if ($choices->{$a}->[$section] ne $choices->{$b}->[$section]) {
            return $choices->{$a}->[$section] cmp $choices->{$b}->[$section];
        }
        return $choices->{$a}->[$fullname] cmp $choices->{$b}->[$fullname];
    } @keys;

    my $type = 'radio';
    if ($self->{'multichoice'}) { $type = 'checkbox'; }
    $result .= "<table cellspacing='2' cellpadding='2' border='0'>\n";
    $result .= "<tr><td></td><td align='center'><b>Student Name</b></td>".
        "<td align='center'><b>Section</b></td></tr>";

    my $checked = 0;
    foreach (@keys) {
        $result .= "<tr><td><input type='$type' name='" .
            $self->{'variable'} . '.forminput' . "'";
            
        if (!$self->{'multichoice'} && !$checked) {
            $result .= " checked ";
            $checked = 1;
        }
        $result .=
            " value='" . HTML::Entities::encode($_)
            . "' /></td><td>"
            . HTML::Entities::encode($choices->{$_}->[$fullname])
            . "</td><td align='center'>" 
            . HTML::Entities::encode($choices->{$_}->[$section])
            . "</td></tr>\n";
    }

    $result .= "</table>\n\n";
    $result .= $buttons;    
    
    return $result;
}

sub postprocess {
    my $self = shift;

    my $result = $ENV{'form.' . $self->{'variable'} . '.forminput'};
    if (!$result) {
        $self->{ERROR_MSG} = 'You must choose at least one student '.
            'to continue.';
        return 0;
    }

    if ($self->{'multichoice'}) {
        $self->process_multiple_choices($self->{'variable'}.'.forminput',
                                        $self->{'variable'});
    }
    if (defined($self->{NEXTSTATE})) {
        $helper->changeState($self->{NEXTSTATE});
    }

    return 1;
}

1;

package Apache::lonhelper::files;

=pod

=head2 Element: files

files allows the users to choose files from a given directory on the
server. It is always multichoice and stores the result as a triple-pipe
delimited entry in the helper variables. 

Since it is extremely unlikely that you can actually code a constant
representing the directory you wish to allow the user to search, <files>
takes a subroutine that returns the name of the directory you wish to
have the user browse.

files accepts the attribute "variable" to control where the files chosen
are put. It accepts the attribute "multichoice" as the other attribute,
defaulting to false, which if true will allow the user to select more
then one choice. 

<files> accepts three subtags. One is the "nextstate" sub-tag that works
as it does with the other tags. Another is a <filechoice> sub tag that
is Perl code that, when surrounded by "sub {" and "}" will return a
string representing what directory on the server to allow the user to 
choose files from. Finally, the <filefilter> subtag should contain Perl
code that when surrounded by "sub { my $filename = shift; " and "}",
returns a true value if the user can pick that file, or false otherwise.
The filename passed to the function will be just the name of the file, 
with no path info.

=cut

no strict;
@ISA = ("Apache::lonhelper::element");
use strict;

BEGIN {
    &Apache::lonxml::register('Apache::lonhelper::files',
                              ('files', 'filechoice', 'filefilter'));
}

sub new {
    my $ref = Apache::lonhelper::element->new();
    bless($ref);
}

sub start_files {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    $paramHash->{'variable'} = $token->[2]{'variable'};
    $helper->declareVar($paramHash->{'variable'});
    $paramHash->{'multichoice'} = $token->[2]{'multichoice'};
}    

sub end_files {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    if (!defined($paramHash->{FILTER_FUNC})) {
        $paramHash->{FILTER_FUNC} = sub { return 1; };
    }
    Apache::lonhelper::files->new();
}    

sub start_filechoice {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }
    $paramHash->{'filechoice'} = Apache::lonxml::get_all_text('/filechoice',
                                                              $parser);
}

sub end_filechoice { return ''; }

sub start_filefilter {
    my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;

    if ($target ne 'helper') {
        return '';
    }

    my $contents = Apache::lonxml::get_all_text('/filefilter',
                                                $parser);
    $contents = 'sub { my $filename = shift; ' . $contents . '}';
    $paramHash->{FILTER_FUNC} = eval $contents;
}

sub end_filefilter { return ''; }

sub render {
    my $self = shift;
    my $result = '';
    my $var = $self->{'variable'};
    
    my $subdirFunc = eval('sub {' . $self->{'filechoice'} . '}');
    my $subdir = &$subdirFunc();

    my $filterFunc = $self->{FILTER_FUNC};
    my $buttons = '';

    if ($self->{'multichoice'}) {
        $result = <<SCRIPT;
<script>
    function checkall(value) {
	for (i=0; i<document.forms.wizform.elements.length; i++) {
            ele = document.forms.wizform.elements[i];
            if (ele.type == "checkbox") {
                document.forms.wizform.elements[i].checked=value;
            }
        }
    }
</script>
SCRIPT
        my $buttons = <<BUTTONS;
<br /> &nbsp;
<input type="button" onclick="checkall(true)" value="Select All" />
<input type="button" onclick="checkall(false)" value="Unselect All" />
<br /> &nbsp;
BUTTONS
    }

    # Get the list of files in this directory.
    my @fileList;

    # If the subdirectory is in local CSTR space
    if ($subdir =~ m|/home/([^/]+)/public_html|) {
        my $user = $1;
        my $domain = $Apache::lonnet::perlvar{'lonDefDomain'};
        @fileList = &Apache::lonnet::dirlist($subdir, $domain, $user, '');
    } else {
        # local library server resource space
        @fileList = &Apache::lonnet::dirlist($subdir, $ENV{'user.domain'}, $ENV{'user.name'}, '');
    }

    $result .= $buttons;

    if (defined $self->{ERROR_MSG}) {
        $result .= '<br /><font color="#FF0000">' . $self->{ERROR_MSG} . '</font><br /><br />';
    }

    $result .= '<table border="0" cellpadding="1" cellspacing="1">';

    # Keeps track if there are no choices, prints appropriate error
    # if there are none. 
    my $choices = 0;
    my $type = 'radio';
    if ($self->{'multichoice'}) {
        $type = 'checkbox';
    }
    # Print each legitimate file choice.
    for my $file (@fileList) {
        $file = (split(/&/, $file))[0];
        if ($file eq '.' || $file eq '..') {
            next;
        }
        my $fileName = $subdir .'/'. $file;
        if (&$filterFunc($file)) {
            $result .= '<tr><td align="right">' .
                "<input type='$type' name='" . $var
            . ".forminput' value='" . HTML::Entities::encode($fileName) .
                "'";
            if (!$self->{'multichoice'} && $choices == 0) {
                $result .= ' checked';
            }
            $result .= "/></td><td>" . $file . "</td></tr>\n";
            $choices++;
        }
    }

    $result .= "</table>\n";

    if (!$choices) {
        $result .= '<font color="#FF0000">There are no files available to select in this directory. Please go back and select another option.</font><br /><br />';
    }

    $result .= $buttons;

    return $result;
}

sub postprocess {
    my $self = shift;
    my $result = $ENV{'form.' . $self->{'variable'} . '.forminput'};
    if (!$result) {
        $self->{ERROR_MSG} = 'You must choose at least one file '.
            'to continue.';
        return 0;
    }

    if ($self->{'multichoice'}) {
        $self->process_multiple_choices($self->{'variable'}.'.forminput',
                                        $self->{'variable'});
    }
    if (defined($self->{NEXTSTATE})) {
        $helper->changeState($self->{NEXTSTATE});
    }

    return 1;
}

1;

__END__