# The LearningOnline Network with CAPA
# Navigate Maps Handler
#
# $Id: lonnavmaps.pm,v 1.199 2003/06/12 13:20:27 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
#
# (TeX Content Handler
#
# 05/29/00,05/30 Gerd Kortemeyer)
# 08/30,08/31,09/06,09/14,09/15,09/16,09/19,09/20,09/21,09/23,
# 10/02,10/10,10/14,10/16,10/18,10/19,10/31,11/6,11/14,11/16 Gerd Kortemeyer)
#
# 3/1/1,6/1,17/1,29/1,30/1,2/8,9/21,9/24,9/25 Gerd Kortemeyer
# YEAR=2002
# 1/1 Gerd Kortemeyer
# Oct-Nov Jeremy Bowers
# YEAR=2003
# Jeremy Bowers ... lots of days

package Apache::lonnavmaps;

use strict;
use Apache::Constants qw(:common :http);
use Apache::loncommon();
use Apache::lonmenu();
use POSIX qw (floor strftime);
use Data::Dumper; # for debugging, not always used

# symbolic constants
sub SYMB { return 1; }
sub URL { return 2; }
sub NOTHING { return 3; }

# Some data

my $resObj = "Apache::lonnavmaps::resource";

# Keep these mappings in sync with lonquickgrades, which uses the colors
# instead of the icons.
my %statusIconMap = 
    ( $resObj->NETWORK_FAILURE    => '',
      $resObj->NOTHING_SET        => '',
      $resObj->CORRECT            => 'navmap.correct.gif',
      $resObj->EXCUSED            => 'navmap.correct.gif',
      $resObj->PAST_DUE_NO_ANSWER => 'navmap.wrong.gif',
      $resObj->PAST_DUE_ANSWER_LATER => 'navmap.wrong.gif',
      $resObj->ANSWER_OPEN        => 'navmap.wrong.gif',
      $resObj->OPEN_LATER         => '',
      $resObj->TRIES_LEFT         => 'navmap.open.gif',
      $resObj->INCORRECT          => 'navmap.wrong.gif',
      $resObj->OPEN               => 'navmap.open.gif',
      $resObj->ATTEMPTED          => 'navmap.open.gif',
      $resObj->ANSWER_SUBMITTED   => '' );

my %iconAltTags = 
    ( 'navmap.correct.gif' => 'Correct',
      'navmap.wrong.gif'   => 'Incorrect',
      'navmap.open.gif'    => 'Open' );

# Defines a status->color mapping, null string means don't color
my %colormap = 
    ( $resObj->NETWORK_FAILURE        => '',
      $resObj->CORRECT                => '',
      $resObj->EXCUSED                => '#3333FF',
      $resObj->PAST_DUE_ANSWER_LATER  => '',
      $resObj->PAST_DUE_NO_ANSWER     => '',
      $resObj->ANSWER_OPEN            => '#006600',
      $resObj->OPEN_LATER             => '',
      $resObj->TRIES_LEFT             => '',
      $resObj->INCORRECT              => '',
      $resObj->OPEN                   => '',
      $resObj->NOTHING_SET            => '' );
# And a special case in the nav map; what to do when the assignment
# is not yet done and due in less then 24 hours
my $hurryUpColor = "#FF0000";

sub handler {
    my $r = shift;
    real_handler($r);
}

sub real_handler {
    my $r = shift;

    # Handle header-only request
    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;
    }

    # Send header, don't cache this page
    if ($ENV{'browser.mathml'}) {
        $r->content_type('text/xml');
    } else {
        $r->content_type('text/html');
    }
    &Apache::loncommon::no_cache($r);
    $r->send_http_header;

    # Create the nav map
    my $navmap = Apache::lonnavmaps::navmap->new(
                        $ENV{"request.course.fn"}.".db",
                        $ENV{"request.course.fn"}."_parms.db", 1, 1);


    if (!defined($navmap)) {
        my $requrl = $r->uri;
        $ENV{'user.error.msg'} = "$requrl:bre:0:0:Course not initialized";
        return HTTP_NOT_ACCEPTABLE;
    }

    $r->print("<html><head>\n");
    $r->print("<title>Navigate Course Contents</title>");
# ------------------------------------------------------------ Get query string
    &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},['register']);
    
# ----------------------------------------------------- Force menu registration
    my $addentries='';
    if ($ENV{'form.register'}) {
       $addentries=' onLoad="'.&Apache::lonmenu::loadevents().
	   '" onUnload="'.&Apache::lonmenu::unloadevents().'"';
       $r->print(&Apache::lonmenu::registerurl(1));
    }

    # Header
    $r->print('</head>'.
              &Apache::loncommon::bodytag('Navigate Course Contents','',
                                    $addentries,'','',$ENV{'form.register'}));
    $r->print('<script>window.focus();</script>');

    $r->rflush();

    # Now that we've displayed some stuff to the user, init the navmap
    $navmap->init();

    $r->print('<br>&nbsp;');
    $r->rflush();

    # Check that it's defined
    if (!($navmap->courseMapDefined())) {
        $r->print('<font size="+2" color="red">Coursemap undefined.</font>' .
                  '</body></html>');
        return OK;
    }

    # See if there's only one map in the top-level, if we don't
    # already have a filter... if so, automatically display it
    if ($ENV{QUERY_STRING} !~ /filter/) {
        my $iterator = $navmap->getIterator(undef, undef, undef, 0);
        my $depth = 1;
        $iterator->next();
        my $curRes = $iterator->next();
        my $sequenceCount = 0;
        my $sequenceId;
        while ($depth > 0) {
            if ($curRes == $iterator->BEGIN_MAP()) { $depth++; }
            if ($curRes == $iterator->END_MAP()) { $depth--; }
            
            if (ref($curRes) && $curRes->is_sequence()) {
                $sequenceCount++;
                $sequenceId = $curRes->map_pc();
            }
            
            $curRes = $iterator->next();
        }
        
        if ($sequenceCount == 1) {
            # The automatic iterator creation in the render call 
            # will pick this up. We know the condition because
            # the defined($ENV{'form.filter'}) also ensures this
            # is a fresh call.
            $ENV{'form.filter'} = "$sequenceId";
        }
    }

    my $jumpToFirstHomework = 0;
    # Check to see if the student is jumping to next open, do-able problem
    if ($ENV{QUERY_STRING} eq 'jumpToFirstHomework') {
        $jumpToFirstHomework = 1;
        # Find the next homework problem that they can do.
        my $iterator = $navmap->getIterator(undef, undef, undef, 1);
        my $depth = 1;
        $iterator->next();
        my $curRes = $iterator->next();
        my $foundDoableProblem = 0;
        my $problemRes;
        
        while ($depth > 0 && !$foundDoableProblem) {
            if ($curRes == $iterator->BEGIN_MAP()) { $depth++; }
            if ($curRes == $iterator->END_MAP()) { $depth--; }

            if (ref($curRes) && $curRes->is_problem()) {
                my $status = $curRes->status();
                if ($curRes->completable()) {
                    $problemRes = $curRes;
                    $foundDoableProblem = 1;

                    # Pop open all previous maps
                    my $stack = $iterator->getStack();
                    pop @$stack; # last resource in the stack is the problem
                                 # itself, which we don't need in the map stack
                    my @mapPcs = map {$_->map_pc()} @$stack;
                    $ENV{'form.filter'} = join(',', @mapPcs);

                    # Mark as both "here" and "jump"
                    $ENV{'form.postsymb'} = $curRes->symb();
                }
            }
        } continue {
            $curRes = $iterator->next();
        }

        # If we found no problems, print a note to that effect.
        if (!$foundDoableProblem) {
            $r->print("<font size='+2'>All homework assignments have been completed.</font><br /><br />");
        }
    } else {
        $r->print("<a href='navmaps?jumpToFirstHomework'>" .
                  "Go To My First Homework Problem</a><br />");
    }

    my $suppressEmptySequences = 0;
    my $filterFunc = undef;
    # Display only due homework.
    my $showOnlyHomework = 0;
    if ($ENV{QUERY_STRING} eq 'showOnlyHomework') {
        $showOnlyHomework = 1;
        $suppressEmptySequences = 1;
        $filterFunc = sub { my $res = shift; 
                            return $res->completable() || $res->is_sequence();
                        };
        $r->print("<p><font size='+2'>Uncompleted Homework</font></p>");
        $ENV{'form.filter'} = '';
        $ENV{'form.condition'} = 1;
    } else {
        $r->print("<a href='navmaps?showOnlyHomework'>" .
                  "Show Only Uncompleted Homework</a><br />");
    }

    # renderer call
    my $renderArgs = { 'cols' => [0,1,2,3],
                       'url' => '/adm/navmaps',
                       'navmap' => $navmap,
                       'suppressNavmap' => 1,
                       'suppressEmptySequences' => $suppressEmptySequences,
                       'filterFunc' => $filterFunc,
                       'r' => $r};
    my $render = render($renderArgs);
    $navmap->untieHashes();

    # If no resources were printed, print a reassuring message so the
    # user knows there was no error.
    if ($renderArgs->{'counter'} == 0) {
        if ($showOnlyHomework) {
            $r->print("<p><font size='+1'>All homework is currently completed.</font></p>");
        } else { # both jumpToFirstHomework and normal use the same: course must be empty
            $r->print("<p><font size='+1'>This course is empty.</font></p>");
        }
    }

    $r->print("</body></html>");
    $r->rflush();

    return OK;
}

# Convenience functions: Returns a string that adds or subtracts
# the second argument from the first hash, appropriate for the 
# query string that determines which folders to recurse on
sub addToFilter {
    my $hashIn = shift;
    my $addition = shift;
    my %hash = %$hashIn;
    $hash{$addition} = 1;

    return join (",", keys(%hash));
}

sub removeFromFilter {
    my $hashIn = shift;
    my $subtraction = shift;
    my %hash = %$hashIn;

    delete $hash{$subtraction};
    return join(",", keys(%hash));
}

# Convenience function: Given a stack returned from getStack on the iterator,
# return the correct src() value.
# Later, this should add an anchor when we start putting anchors in pages.
sub getLinkForResource {
    my $stack = shift;
    my $res;

    # Check to see if there are any pages in the stack
    foreach $res (@$stack) {
        if (defined($res) && $res->is_page()) {
            return $res->src();
        }
    }

    # Failing that, return the src of the last resource that is defined
    # (when we first recurse on a map, it puts an undefined resource
    # on the bottom because $self->{HERE} isn't defined yet, and we
    # want the src for the map anyhow)
    foreach (@$stack) {
        if (defined($_)) { $res = $_; }
    }

    return $res->src();
}

# Convenience function: This seperates the logic of how to create
# the problem text strings ("Due: DATE", "Open: DATE", "Not yet assigned",
# etc.) into a seperate function. It takes a resource object as the
# first parameter, and the part number of the resource as the second.
# It's basically a big switch statement on the status of the resource.

sub getDescription {
    my $res = shift;
    my $part = shift;
    my $status = $res->status($part);

    if ($status == $res->NETWORK_FAILURE) { 
        return "Having technical difficulties; please check status later"; 
    }
    if ($status == $res->NOTHING_SET) {
        return "Not currently assigned.";
    }
    if ($status == $res->OPEN_LATER) {
        return "Open " . timeToHumanString($res->opendate($part));
    }
    if ($status == $res->OPEN) {
        if ($res->duedate($part)) {
            return "Due " . timeToHumanString($res->duedate($part));
        } else {
            return "Open, no due date";
        }
    }
    if ($status == $res->PAST_DUE_ANSWER_LATER) {
        return "Answer open " . timeToHumanString($res->answerdate($part));
    }
    if ($status == $res->PAST_DUE_NO_ANSWER) {
        return "Was due " . timeToHumanString($res->duedate($part));
    }
    if ($status == $res->ANSWER_OPEN) {
        return "Answer available";
    }
    if ($status == $res->EXCUSED) {
        return "Excused by instructor";
    }
    if ($status == $res->ATTEMPTED) {
        return "Not yet graded.";
    }
    if ($status == $res->TRIES_LEFT) {
        my $tries = $res->tries($part);
        my $maxtries = $res->maxtries($part);
        my $triesString = "";
        if ($tries && $maxtries) {
            $triesString = "<font size=\"-1\"><i>($tries of $maxtries tries used)</i></font>";
            if ($maxtries > 1 && $maxtries - $tries == 1) {
                $triesString = "<b>$triesString</b>";
            }
        }
        if ($res->duedate()) {
            return "Due " . timeToHumanString($res->duedate($part)) .
                " $triesString";
        } else {
            return "No due date $triesString";
        }
    }
    if ($status == $res->ANSWER_SUBMITTED) {
        return 'Answer submitted';
    }
}

# Convenience function, so others can use it: Is the problem due in less then
# 24 hours, and still can be done?

sub dueInLessThen24Hours {
    my $res = shift;
    my $part = shift;
    my $status = $res->status($part);

    return ($status == $res->OPEN() || $status == $res->ATTEMPTED() ||
            $status == $res->TRIES_LEFT()) &&
           $res->duedate() && $res->duedate() < time()+(24*60*60) &&
           $res->duedate() > time();
}

# Convenience function, so others can use it: Is there only one try remaining for the
# part, with more then one try to begin with, not due yet and still can be done?
sub lastTry {
    my $res = shift;
    my $part = shift;

    my $tries = $res->tries($part);
    my $maxtries = $res->maxtries($part);
    return $tries && $maxtries && $maxtries > 1 &&
        $maxtries - $tries == 1 && $res->duedate() &&
        $res->duedate() > time();
}

# This puts a human-readable name on the ENV variable.

sub advancedUser {
    return $ENV{'request.role.adv'};
}


# timeToHumanString takes a time number and converts it to a
# human-readable representation, meant to be used in the following
# manner:
# print "Due $timestring"
# print "Open $timestring"
# print "Answer available $timestring"
# Very, very, very, VERY English-only... goodness help a localizer on
# this func...
sub timeToHumanString {
    my ($time) = @_;
    # zero, '0' and blank are bad times
    if (!$time) {
        return 'never';
    }

    my $now = time();

    my @time = localtime($time);
    my @now = localtime($now);

    # Positive = future
    my $delta = $time - $now;

    my $minute = 60;
    my $hour = 60 * $minute;
    my $day = 24 * $hour;
    my $week = 7 * $day;
    my $inPast = 0;

    # Logic in comments:
    # Is it now? (extremely unlikely)
    if ( $delta == 0 ) {
        return "this instant";
    }

    if ($delta < 0) {
        $inPast = 1;
        $delta = -$delta;
    }

    if ( $delta > 0 ) {

        my $tense = $inPast ? " ago" : "";
        my $prefix = $inPast ? "" : "in ";
        
        # Less then a minute
        if ( $delta < $minute ) {
            if ($delta == 1) { return "${prefix}1 second$tense"; }
            return "$prefix$delta seconds$tense";
        }

        # Less then an hour
        if ( $delta < $hour ) {
            # If so, use minutes
            my $minutes = floor($delta / 60);
            if ($minutes == 1) { return "${prefix}1 minute$tense"; }
            return "$prefix$minutes minutes$tense";
        }
        
        # Is it less then 24 hours away? If so,
        # display hours + minutes
        if ( $delta < $hour * 24) {
            my $hours = floor($delta / $hour);
            my $minutes = floor(($delta % $hour) / $minute);
            my $hourString = "$hours hours";
            my $minuteString = ", $minutes minutes";
            if ($hours == 1) {
                $hourString = "1 hour";
            }
            if ($minutes == 1) {
                $minuteString = ", 1 minute";
            }
            if ($minutes == 0) {
                $minuteString = "";
            }
            return "$prefix$hourString$minuteString$tense";
        }

        # Less then 5 days away, display day of the week and
        # HH:MM
        if ( $delta < $day * 5 ) {
            my $timeStr = strftime("%A, %b %e at %I:%M %P", localtime($time));
            $timeStr =~ s/12:00 am/midnight/;
            $timeStr =~ s/12:00 pm/noon/;
            return ($inPast ? "last " : "next ") .
                $timeStr;
        }
        
        # Is it this year?
        if ( $time[5] == $now[5]) {
            # Return on Month Day, HH:MM meridian
            my $timeStr = strftime("on %A, %b %e at %I:%M %P", localtime($time));
            $timeStr =~ s/12:00 am/midnight/;
            $timeStr =~ s/12:00 pm/noon/;
            return $timeStr;
        }

        # Not this year, so show the year
        my $timeStr = strftime("on %A, %b %e %G at %I:%M %P", localtime($time));
        $timeStr =~ s/12:00 am/midnight/;
        $timeStr =~ s/12:00 pm/noon/;
        return $timeStr;
    }
}


=pod

=head1 NAME

Apache::lonnavmap - Subroutines to handle and render the navigation maps

=head1 SYNOPSIS

The main handler generates the navigational listing for the course,
the other objects export this information in a usable fashion for
other modules

=head1 Object: render

The navmap renderer package provides a sophisticated rendering of the
standard navigation maps interface into HTML. The provided nav map
handler is actually just a glorified call to this.

Because of the large number of parameters this function presents,
instead of passing it arguments as is normal, pass it in an anonymous
hash with the given options. This is because there is no obvious order
you may wish to override these in and a hash is easier to read and
understand then "undef, undef, undef, 1, undef, undef, renderButton,
undef, 0" when you mostly want default behaviors.

The package provides a function called 'render', called as
Apache::lonnavmaps::renderer->render({}).

=head2 Overview of Columns

The renderer will build an HTML table for the navmap and return
it. The table is consists of several columns, and a row for each
resource (or possibly each part). You tell the renderer how many
columns to create and what to place in each column, optionally using
one or more of the preparent columns, and the renderer will assemble
the table.

Any additional generally useful column types should be placed in the
renderer code here, so anybody can use it anywhere else. Any code
specific to the current application (such as the addition of <input>
elements in a column) should be placed in the code of the thing using
the renderer.

At the core of the renderer is the array reference COLS (see Example
section below for how to pass this correctly). The COLS array will
consist of entries of one of two types of things: Either an integer
representing one of the pre-packaged column types, or a sub reference
that takes a resource reference, a part number, and a reference to the
argument hash passed to the renderer, and returns a string that will
be inserted into the HTML representation as it.

The pre-packaged column names are refered to by constants in the
Apache::lonnavmaps::renderer namespace. The following currently exist:

=over 4

=item * B<resource>:

The general info about the resource: Link, icon for the type, etc. The
first column in the standard nav map display. This column also accepts
the following parameter in the renderer hash:

=over 4

=item * B<resource_nolink>:

If true, the resource will not be linked. Default: false, resource
will have links.

=item * B<resource_part_count>:

If true (default), the resource will show a part count if the full
part list is not displayed. If false, the resource will never show a
part count.

=item * B<resource_no_folder_link>:

If true, the resource's folder will not be clickable to open or close
it. Default is false. True implies printCloseAll is false, since you
can't close or open folders when this is on anyhow.

=back

=item B<communication_status>:

Whether there is discussion on the resource, email for the user, or
(lumped in here) perl errors in the execution of the problem. This is
the second column in the main nav map.

=item B<quick_status>:

An icon for the status of a problem, with four possible states:
Correct, incorrect, open, or none (not open yet, not a problem). The
third column of the standard navmap.

=item B<long_status>:

A text readout of the details of the current status of the problem,
such as "Due in 22 hours". The fourth column of the standard navmap.

=back

If you add any others please be sure to document them here.

An example of a column renderer that will show the ID number of a
resource, along with the part name if any:

 sub { 
  my ($resource, $part, $params) = @_;   
  if ($part) { return '<td>' . $resource->{ID} . ' ' . $part . '</td>'; }
  return '<td>' . $resource->{ID} . '</td>';
 }

Note these functions are responsible for the TD tags, which allow them
to override vertical and horizontal alignment, etc.

=head2 Parameters

Most of these parameters are only useful if you are *not* using the
folder interface (i.e., the default first column), which is probably
the common case. If you are using this interface, then you should be
able to get away with just using 'cols' (to specify the columns
shown), 'url' (necessary for the folders to link to the current screen
correctly), and possibly 'queryString' if your app calls for it. In
that case, maintaining the state of the folders will be done
automatically.

=over 4

=item * B<iterator>:

A reference to a fresh ::iterator to use from the navmaps. The
rendering will reflect the options passed to the iterator, so you can
use that to just render a certain part of the course, if you like. If
one is not passed, the renderer will attempt to construct one from
ENV{'form.filter'} and ENV{'form.condition'} information, plus the
'iterator_map' parameter if any.

=item * B<iterator_map>:

If you are letting the renderer do the iterator handling, you can
instruct the renderer to render only a particular map by passing it
the source of the map you want to process, like
'/res/103/jerf/navmap.course.sequence'.

=item * B<navmap>:

A reference to a navmap, used only if an iterator is not passed in. If
this is necessary to make an iterator but it is not passed in, a new
one will be constructed based on ENV info. This is useful to do basic
error checking before passing it off to render.

=item * B<r>:

The standard Apache response object. This must be passed to the
renderer or the course hash will be locked.

=item * B<cols>:

An array reference

=item * B<showParts>:

A flag. If yes (default), a line for the resource itself, and a line
for each part will be displayed. If not, only one line for each
resource will be displayed.

=item * B<condenseParts>:

A flag. If yes (default), if all parts of the problem have the same
status and that status is Nothing Set, Correct, or Network Failure,
then only one line will be displayed for that resource anyhow. If no,
all parts will always be displayed. If showParts is 0, this is
ignored.

=item * B<jumpCount>:

A string identifying the URL to place the anchor 'curloc' at. Default
to no anchor at all. It is the responsibility of the renderer user to
ensure that the #curloc is in the URL. By default, determined through
the use of the ENV{} 'jump' information, and should normally "just
work" correctly.

=item * B<here>:

A Symb identifying where to place the 'here' marker. Default empty,
which means no marker.

=item * B<indentString>:

A string identifying the indentation string to use. By default, this
is a 25 pixel whitespace image with no alt text.

=item * B<queryString>:

A string which will be prepended to the query string used when the
folders are opened or closed.

=item * B<url>:

The url the folders will link to, which should be the current
page. Required if the resource info column is shown.

=item * B<currentJumpIndex>:

Describes the currently-open row number to cause the browser to jump
to, because the user just opened that folder. By default, pulled from
the Jump information in the ENV{'form.*'}.

=item * B<printKey>:

If true, print the key that appears on the top of the standard
navmaps. Default is false.

=item * B<printCloseAll>:

If true, print the "Close all folders" or "open all folders"
links. Default is true.

=item * B<filterFunc>:

A function that takes the resource object as its only parameter and
returns a true or false value. If true, the resource is displayed. If
false, it is simply skipped in the display. By default, all resources
are shown.

=item * B<suppressEmptySequences>:

If you're using a filter function, and displaying sequences to orient
the user, then frequently some sequences will be empty. Setting this to
true will cause those sequences not to display, so as not to confuse the
user into thinking that if the sequence is there there should be things
under it.

=item * B<suppressNavmaps>:

If true, will not display Navigate Content resources. Default to
false.

=back

=head2 Additional Info

In addition to the parameters you can pass to the renderer, which will
be passed through unchange to the column renderers, the renderer will
generate the following information which your renderer may find
useful:

If you want to know how many rows were printed, the 'counter' element
of the hash passed into the render function will contain the
count. You may want to check whether any resources were printed at
all.

=over 4

=back

=cut

sub resource { return 0; }
sub communication_status { return 1; }
sub quick_status { return 2; }
sub long_status { return 3; }

# Data for render_resource

sub render_resource {
    my ($resource, $part, $params) = @_;

    my $nonLinkedText = ''; # stuff after resource title not in link

    my $link = $params->{"resourceLink"};
    my $src = $resource->src();
    my $it = $params->{"iterator"};
    my $filter = $it->{FILTER};

    my $title = $resource->compTitle();
    if ($src =~ /^\/uploaded\//) {
        $nonLinkedText=$title;
        $title = '';
    }
    my $partLabel = "";
    my $newBranchText = "";
    
    # If this is a new branch, label it so
    if ($params->{'isNewBranch'}) {
        $newBranchText = "<img src='/adm/lonIcons/branch.gif' border='0' />";
    }

    # links to open and close the folder
    my $linkopen = "<a href='$link'>";
    my $linkclose = "</a>";

    # Default icon: HTML page
    my $icon = "<img src='/adm/lonIcons/html.gif' alt='' border='0' />";
    
    if ($resource->is_problem()) {
        if ($part eq '0' || $params->{'condensed'}) {
            $icon = '<img src="/adm/lonIcons/problem.gif" alt="" border="0" />';
        } else {
            $icon = $params->{'indentString'};
        }
    }

    # Display the correct map icon to open or shut map
    if ($resource->is_map()) {
        my $mapId = $resource->map_pc();
        my $nowOpen = !defined($filter->{$mapId});
        if ($it->{CONDITION}) {
            $nowOpen = !$nowOpen;
        }

        if (!$params->{'resource_no_folder_link'}) {
            $icon = 'navmap.folder.' . ($nowOpen ? 'closed' : 'open') . '.gif';
            $icon = "<img src='/adm/lonIcons/$icon' alt='' border='0' />";

            $linkopen = "<a href='" . $params->{'url'} . '?' . 
                $params->{'queryString'} . '&filter=';
            $linkopen .= ($nowOpen xor $it->{CONDITION}) ?
                addToFilter($filter, $mapId) :
                removeFromFilter($filter, $mapId);
            $linkopen .= "&condition=" . $it->{CONDITION} . '&hereType='
                . $params->{'hereType'} . '&here=' .
                &Apache::lonnet::escape($params->{'here'}) . 
                '&jump=' .
                &Apache::lonnet::escape($resource->symb()) . 
                "&folderManip=1'>";
        } else {
            # Don't allow users to manipulate folder
            $icon = 'navmap.folder.' . ($nowOpen ? 'closed' : 'open') .
                '.nomanip.gif';
            $icon = "<img src='/adm/lonIcons/$icon' alt='' border='0' />";

            $linkopen = "";
            $linkclose = "";
        }
    }

    if ($resource->randomout()) {
        $nonLinkedText .= ' <i>(hidden)</i> ';
    }
    
    # We're done preparing and finally ready to start the rendering
    my $result = "<td align='left' valign='center'>";

    my $indentLevel = $params->{'indentLevel'};
    if ($newBranchText) { $indentLevel--; }

    # print indentation
    for (my $i = 0; $i < $indentLevel; $i++) {
        $result .= $params->{'indentString'};
    }

    # Decide what to display
    $result .= "$newBranchText$linkopen$icon$linkclose";
    
    my $curMarkerBegin = '';
    my $curMarkerEnd = '';

    # Is this the current resource?
    if (!$params->{'displayedHereMarker'} && 
        $resource->symb() eq $params->{'here'} ) {
        $curMarkerBegin = '<font color="red" size="+2">&gt; </font>';
        $curMarkerEnd = '<font color="red" size="+2">&lt;</font>';
        $params->{'displayedHereMarker'} = 1;
    }

    if ($resource->is_problem() && $part ne '0' && 
        !$params->{'condensed'}) {
        $partLabel = " (Part $part)";
        $title = "";
    }

    if ($params->{'condensed'} && $resource->countParts() > 1) {
        $nonLinkedText .= ' (' . $resource->countParts() . ' parts)';
    }

    if (!$params->{'resource_nolink'}) {
        $result .= "  $curMarkerBegin<a href='$link'>$title$partLabel</a>$curMarkerEnd $nonLinkedText</td>";
    } else {
        $result .= "  $curMarkerBegin$title$partLabel$curMarkerEnd $nonLinkedText</td>";
    }

    return $result;
}

sub render_communication_status {
    my ($resource, $part, $params) = @_;
    my $discussionHTML = ""; my $feedbackHTML = ""; my $errorHTML = "";

    my $link = $params->{"resourceLink"};
    my $linkopen = "<a href='$link'>";
    my $linkclose = "</a>";

    if ($resource->hasDiscussion()) {
        $discussionHTML = $linkopen .
            '<img border="0" src="/adm/lonMisc/chat.gif" />' .
            $linkclose;
    }
    
    if ($resource->getFeedback()) {
        my $feedback = $resource->getFeedback();
        foreach (split(/\,/, $feedback)) {
            if ($_) {
                $feedbackHTML .= '&nbsp;<a href="/adm/email?display='
                    . &Apache::lonnet::escape($_) . '">'
                    . '<img src="/adm/lonMisc/feedback.gif" '
                    . 'border="0" /></a>';
            }
        }
    }
    
    if ($resource->getErrors()) {
        my $errors = $resource->getErrors();
        foreach (split(/,/, $errors)) {
            if ($_) {
                $errorHTML .= '&nbsp;<a href="/adm/email?display='
                    . &Apache::lonnet::escape($_) . '">'
                    . '<img src="/adm/lonMisc/bomb.gif" '
                    . 'border="0" /></a>';
            }
        }
    }

    if ($params->{'multipart'} && $part != '0') {
	$discussionHTML = $feedbackHTML = $errorHTML = '';
    }

    return "<td width=\"75\" align=\"left\" valign=\"center\">$discussionHTML$feedbackHTML$errorHTML&nbsp;</td>";

}
sub render_quick_status {
    my ($resource, $part, $params) = @_;
    my $result = "";
    my $firstDisplayed = !$params->{'condensed'} && 
        $params->{'multipart'} && $part eq "0";

    my $link = $params->{"resourceLink"};
    my $linkopen = "<a href='$link'>";
    my $linkclose = "</a>";

    if ($resource->is_problem() &&
        !$firstDisplayed) {
        my $icon = $statusIconMap{$resource->status($part)};
        my $alt = $iconAltTags{$icon};
        if ($icon) {
            $result .= "<td width='30' valign='center' width='50' align='right'>$linkopen<img width='25' height='25' src='/adm/lonIcons/$icon' border='0' alt='$alt' />$linkclose</td>\n";
        } else {
            $result .= "<td width='30'>&nbsp;</td>\n";
        }
    } else { # not problem, no icon
        $result .= "<td width='30'>&nbsp;</td>\n";
    }

    return $result;
}
sub render_long_status {
    my ($resource, $part, $params) = @_;
    my $result = "<td align='right' valign='center'>\n";
    my $firstDisplayed = !$params->{'condensed'} && 
        $params->{'multipart'} && $part eq "0";
                
    my $color;
    if ($resource->is_problem() && ($resource->countParts() <= 1 || $part ne '') ) {
        $color = $colormap{$resource->status};
        
        if (dueInLessThen24Hours($resource, $part) ||
            lastTry($resource, $part)) {
            $color = $hurryUpColor;
        }
    }
    
    if ($resource->kind() eq "res" &&
        $resource->is_problem() &&
        !$firstDisplayed) {
        if ($color) {$result .= "<font color=\"$color\"><b>"; }
        $result .= getDescription($resource, $part);
        if ($color) {$result .= "</b></font>"; }
    }
    if ($resource->is_map() && advancedUser() && $resource->randompick()) {
        $result .= '(randomly select ' . $resource->randompick() .')';
    }
    
    return $result;
}

my @preparedColumns = (\&render_resource, \&render_communication_status,
                       \&render_quick_status, \&render_long_status);

sub setDefault {
    my ($val, $default) = @_;
    if (!defined($val)) { return $default; }
    return $val;
}

sub render {
    my $args = shift;
    &Apache::loncommon::get_unprocessed_cgi($ENV{QUERY_STRING});
    my $result = '';

    # Configure the renderer.
    my $cols = $args->{'cols'};
    if (!defined($cols)) {
        # no columns, no nav maps.
        return '';
    }
    my $mustCloseNavMap = 0;
    my $navmap;
    if (defined($args->{'navmap'})) {
        $navmap = $args->{'navmap'};
    }

    my $r = $args->{'r'};
    my $queryString = $args->{'queryString'};
    my $jump = $args->{'jump'};
    my $here = $args->{'here'};
    my $suppressNavmap = setDefault($args->{'suppressNavmap'}, 0);
    my $currentJumpDelta = 2; # change this to change how many resources are displayed
                             # before the current resource when using #current

    # If we were passed 'here' information, we are not rendering
    # after a folder manipulation, and we were not passed an
    # iterator, make sure we open the folders to show the "here"
    # marker
    my $filterHash = {};
    # Figure out what we're not displaying
    foreach (split(/\,/, $ENV{"form.filter"})) {
        if ($_) {
            $filterHash->{$_} = "1";
        }
    }

    # Filter: Remember filter function and add our own filter: Refuse
    # to show hidden resources unless the user can see them.
    my $userCanSeeHidden = advancedUser();
    my $filterFunc = setDefault($args->{'filterFunc'},
                                sub {return 1;});
    if (!$userCanSeeHidden) {
        # Without renaming the filterfunc, the server seems to go into
        # an infinite loop
        my $oldFilterFunc = $filterFunc;
        $filterFunc = sub { my $res = shift; return !$res->randomout() && 
                                &$oldFilterFunc($res);};
    }

    my $condition = 0;
    if ($ENV{'form.condition'}) {
        $condition = 1;
    }

    if (!$ENV{'form.folderManip'} && !defined($args->{'iterator'})) {
        # Step 1: Check to see if we have a navmap
        if (!defined($navmap)) {
            $navmap = Apache::lonnavmaps::navmap->new(
                        $ENV{"request.course.fn"}.".db",
                        $ENV{"request.course.fn"}."_parms.db", 1, 1);
            $mustCloseNavMap = 1;
        }
        $navmap->init();

        # Step two: Locate what kind of here marker is necessary
        # Determine where the "here" marker is and where the screen jumps to.

        if ($ENV{'form.postsymb'}) {
            $here = $jump = $ENV{'form.postsymb'};
        } elsif ($ENV{'form.postdata'}) {
            # couldn't find a symb, is there a URL?
            my $currenturl = $ENV{'form.postdata'};
            #$currenturl=~s/^http\:\/\///;
            #$currenturl=~s/^[^\/]+//;
            
            $here = $jump = &Apache::lonnet::symbread($currenturl);
        }

        # Step three: Ensure the folders are open
        my $mapIterator = $navmap->getIterator(undef, undef, undef, 1);
        my $depth = 1;
        $mapIterator->next(); # discard the first BEGIN_MAP
        my $curRes = $mapIterator->next();
        my $found = 0;
        
        # We only need to do this if we need to open the maps to show the
        # current position. This will change the counter so we can't count
        # for the jump marker with this loop.
        while ($depth > 0 && !$found) {
            if ($curRes == $mapIterator->BEGIN_MAP()) { $depth++; }
            if ($curRes == $mapIterator->END_MAP()) { $depth--; }
            
            if (ref($curRes) && $curRes->symb() eq $here) {
                my $mapStack = $mapIterator->getStack();
                
                # Ensure the parent maps are open
                for my $map (@{$mapStack}) {
                    if ($condition) {
                        undef $filterHash->{$map->map_pc()};
                    } else {
                        $filterHash->{$map->map_pc()} = 1;
                    }
                }
                $found = 1;
            }
            
            $curRes = $mapIterator->next();
        }            
    }        

    if ( !defined($args->{'iterator'}) && $ENV{'form.folderManip'} ) { # we came from a user's manipulation of the nav page
        # If this is a click on a folder or something, we want to preserve the "here"
        # from the querystring, and get the new "jump" marker
        $here = $ENV{'form.here'};
        $jump = $ENV{'form.jump'};
    } 
    
    my $it = $args->{'iterator'};
    if (!defined($it)) {
        # Construct a default iterator based on $ENV{'form.'} information
        
        # Step 1: Check to see if we have a navmap
        if (!defined($navmap)) {
            $navmap = Apache::lonnavmaps::navmap->new($r, 
                        $ENV{"request.course.fn"}.".db",
                        $ENV{"request.course.fn"}."_parms.db", 1, 1);
            $mustCloseNavMap = 1;
        }
        # Paranoia: Make sure it's ready
        $navmap->init();

        # See if we're being passed a specific map
        if ($args->{'iterator_map'}) {
            my $map = $args->{'iterator_map'};
            $map = $navmap->getResourceByUrl($map);
            my $firstResource = $map->map_start();
            my $finishResource = $map->map_finish();

            $args->{'iterator'} = $it = $navmap->getIterator($firstResource, $finishResource, $filterHash, $condition);
        } else {
            $args->{'iterator'} = $it = $navmap->getIterator(undef, undef, $filterHash, $condition);
        }
    }
    
    # (re-)Locate the jump point, if any
    # Note this does not take filtering or hidden into account... need
    # to be fixed?
    my $mapIterator = $navmap->getIterator(undef, undef, $filterHash, 0);
    my $depth = 1;
    $mapIterator->next();
    my $curRes = $mapIterator->next();
    my $foundJump = 0;
    my $counter = 0;
    
    while ($depth > 0 && !$foundJump) {
        if ($curRes == $mapIterator->BEGIN_MAP()) { $depth++; }
        if ($curRes == $mapIterator->END_MAP()) { $depth--; }
        if (ref($curRes)) { $counter++; }
        
        if (ref($curRes) && $jump eq $curRes->symb()) {
            
            # This is why we have to use the main iterator instead of the
            # potentially faster DFS: The count has to be the same, so
            # the order has to be the same, which DFS won't give us.
            $args->{'currentJumpIndex'} = $counter;
            $foundJump = 1;
        }
        
        $curRes = $mapIterator->next();
    }

    my $showParts = setDefault($args->{'showParts'}, 1);
    my $condenseParts = setDefault($args->{'condenseParts'}, 1);
    # keeps track of when the current resource is found,
    # so we can back up a few and put the anchor above the
    # current resource
    my $printKey = $args->{'printKey'};
    my $printCloseAll = $args->{'printCloseAll'};
    if (!defined($printCloseAll)) { $printCloseAll = 1; }
    
    # Print key?
    if ($printKey) {
        $result .= '<table border="0" cellpadding="2" cellspacing="0">';
        my $date=localtime;
        $result.='<tr><td align="right" valign="bottom">Key:&nbsp;&nbsp;</td>';
        if ($navmap->{LAST_CHECK}) {
            $result .= 
                '<img src="/adm/lonMisc/chat.gif"> New discussion since '.
                strftime("%A, %b %e at %I:%M %P", localtime($navmap->{LAST_CHECK})).
                '</td><td align="center" valign="bottom">&nbsp;&nbsp;'.
                '<img src="/adm/lonMisc/feedback.gif"> New message (click to open)<p>'.
                '</td>'; 
        } else {
            $result .= '<td align="center" valign="bottom">&nbsp;&nbsp;'.
                '<img src="/adm/lonMisc/chat.gif"> Discussions</td><td align="center" valign="bottom">'.
                '&nbsp;&nbsp;<img src="/adm/lonMisc/feedback.gif"> New message (click to open)'.
                '</td>'; 
        }

        $result .= '</tr></table>';
    }

    if ($printCloseAll && !$args->{'resource_no_folder_link'}) {
        if ($condition) {
            $result.="<a href=\"navmaps?condition=0&filter=&$queryString" .
                "&here=" . Apache::lonnet::escape($here) .
                "\">Close All Folders</a>";
        } else {
            $result.="<a href=\"navmaps?condition=1&filter=&$queryString" .
                "&here=" . Apache::lonnet::escape($here) . 
                "\">Open All Folders</a>";
        }
        $result .= "<br /><br />\n";
    }    

    if ($r) {
        $r->print($result);
        $r->rflush();
        $result = "";
    }
    # End parameter setting
            
    # Data
    $result .= '<table cellspacing="0" cellpadding="3" border="0" bgcolor="#FFFFFF">' ."\n";
    my $res = "Apache::lonnavmaps::resource";
    my %condenseStatuses =
        ( $res->NETWORK_FAILURE    => 1,
          $res->NOTHING_SET        => 1,
          $res->CORRECT            => 1 );
    my @backgroundColors = ("#FFFFFF", "#F6F6F6");

    # Shared variables
    $args->{'counter'} = 0; # counts the rows
    $args->{'indentLevel'} = 0;
    $args->{'isNewBranch'} = 0;
    $args->{'condensed'} = 0;    
    $args->{'indentString'} = setDefault($args->{'indentString'}, "<img src='/adm/lonIcons/whitespace1.gif' width='25' height='1' alt='' border='0' />");
    $args->{'displayedHereMarker'} = 0;

    # If we're suppressing empty sequences, look for them here. Use DFS for speed,
    # since structure actually doesn't matter, except what map has what resources.
    if ($args->{'suppressEmptySequences'}) {
        my $dfsit = Apache::lonnavmaps::DFSiterator->new($navmap,
                                                         $it->{FIRST_RESOURCE},
                                                         $it->{FINISH_RESOURCE},
                                                         {}, undef, 1);
        $depth = 0;
        $dfsit->next();
        my $curRes = $dfsit->next();
        while ($depth > -1) {
            if ($curRes == $dfsit->BEGIN_MAP()) { $depth++; }
            if ($curRes == $dfsit->END_MAP()) { $depth--; }

            if (ref($curRes)) { 
                # Parallel pre-processing: Do sequences have non-filtered-out children?
                if ($curRes->is_sequence()) {
                    $curRes->{DATA}->{HAS_VISIBLE_CHILDREN} = 0;
                    # Sequences themselves do not count as visible children,
                    # unless those sequences also have visible children.
                    # This means if a sequence appears, there's a "promise"
                    # that there's something under it if you open it, somewhere.
                } else {
                    # Not a sequence: if it's filtered, ignore it, otherwise
                    # rise up the stack and mark the sequences as having children
                    if (&$filterFunc($curRes)) {
                        for my $sequence (@{$dfsit->getStack()}) {
                            $sequence->{DATA}->{HAS_VISIBLE_CHILDREN} = 1;
                        }
                    }
                }
            }
        } continue {
            $curRes = $dfsit->next();
        }
    }

    my $displayedJumpMarker = 0;
    # Set up iteration.
    $depth = 1;
    $it->next(); # discard initial BEGIN_MAP
    $curRes = $it->next();
    my $now = time();
    my $in24Hours = $now + 24 * 60 * 60;
    my $rownum = 0;

    # export "here" marker information
    $args->{'here'} = $here;

    while ($depth > 0) {
        if ($curRes == $it->BEGIN_MAP()) { $depth++; }
        if ($curRes == $it->END_MAP()) { $depth--; }

        # Maintain indentation level.
        if ($curRes == $it->BEGIN_MAP() ||
            $curRes == $it->BEGIN_BRANCH() ) {
            $args->{'indentLevel'}++;
        }
        if ($curRes == $it->END_MAP() ||
            $curRes == $it->END_BRANCH() ) {
            $args->{'indentLevel'}--;
        }
        # Notice new branches
        if ($curRes == $it->BEGIN_BRANCH()) {
            $args->{'isNewBranch'} = 1;
        }

        # If this isn't an actual resource, continue on
        if (!ref($curRes)) {
            next;
        }

        # If this has been filtered out, continue on
        if (!(&$filterFunc($curRes))) {
            $args->{'isNewBranch'} = 0; # Don't falsely remember this
            next;
        } 

        # If this is an empty sequence and we're filtering them, continue on
        if ($curRes->is_sequence() && $args->{'suppressEmptySequences'} &&
            !$curRes->{DATA}->{HAS_VISIBLE_CHILDREN}) {
            next;
        }

        # If we're suppressing navmaps and this is a navmap, continue on
        if ($suppressNavmap && $curRes->src() =~ /^\/adm\/navmaps/) {
            next;
        }

        $args->{'counter'}++;

        # Does it have multiple parts?
        $args->{'multipart'} = 0;
        $args->{'condensed'} = 0;
        my @parts;
            
        # Decide what parts to show.
        if ($curRes->is_problem() && $showParts) {
            @parts = @{$curRes->parts()};
            $args->{'multipart'} = $curRes->multipart();
            
            if ($condenseParts) { # do the condensation
                if (!$curRes->opendate("0")) {
                    @parts = ();
                    $args->{'condensed'} = 1;
                }
                if (!$args->{'condensed'}) {
                    # Decide whether to condense based on similarity
                    my $status = $curRes->status($parts[0]);
                    my $due = $curRes->duedate($parts[0]);
                    my $open = $curRes->opendate($parts[0]);
                    my $statusAllSame = 1;
                    my $dueAllSame = 1;
                    my $openAllSame = 1;
                    for (my $i = 1; $i < scalar(@parts); $i++) {
                        if ($curRes->status($parts[$i]) != $status){
                            $statusAllSame = 0;
                        }
                        if ($curRes->duedate($parts[$i]) != $due ) {
                            $dueAllSame = 0;
                        }
                        if ($curRes->opendate($parts[$i]) != $open) {
                            $openAllSame = 0;
                        }
                    }
                    # $*allSame is true if all the statuses were
                    # the same. Now, if they are all the same and
                    # match one of the statuses to condense, or they
                    # are all open with the same due date, or they are
                    # all OPEN_LATER with the same open date, display the
                    # status of the first non-zero part (to get the 'correct'
                    # status right, since 0 is never 'correct' or 'open').
                    if (($statusAllSame && defined($condenseStatuses{$status})) ||
                        ($dueAllSame && $status == $curRes->OPEN && $statusAllSame)||
                        ($openAllSame && $status == $curRes->OPEN_LATER && $statusAllSame) ){
                        @parts = ($parts[0]);
                        $args->{'condensed'} = 1;
                    }
                }
		# Multipart problem with one part: always "condense" (happens
		#  to match the desirable behavior)
		if ($curRes->countParts() == 1) {
		    @parts = ($parts[0]);
		    $args->{'condensed'} = 1;
		}
            }
        } 
            
        # If the multipart problem was condensed, "forget" it was multipart
        if (scalar(@parts) == 1) {
            $args->{'multipart'} = 0;
        } else {
            # Add part 0 so we display it correctly.
            unshift @parts, '0';
        }

        # Now, we've decided what parts to show. Loop through them and
        # show them.
        foreach my $part (@parts) {
            $rownum ++;
            my $backgroundColor = $backgroundColors[$rownum % scalar(@backgroundColors)];
            
            $result .= "  <tr bgcolor='$backgroundColor'>\n";

            # Set up some data about the parts that the cols might want
            my $filter = $it->{FILTER};
            my $stack = $it->getStack();
            my $src = getLinkForResource($stack);
            
            my $srcHasQuestion = $src =~ /\?/;
            $args->{"resourceLink"} = $src.
                ($srcHasQuestion?'&':'?') .
                'symb=' . &Apache::lonnet::escape($curRes->symb());
            
            # Now, display each column.
            foreach my $col (@$cols) {
                my $colHTML = '';
                if (ref($col)) {
                    $colHTML .= &$col($curRes, $part, $args);
                } else {
                    $colHTML .= &{$preparedColumns[$col]}($curRes, $part, $args);
                }

                # If this is the first column and it's time to print
                # the anchor, do so
                if ($col == $cols->[0] && 
                    $args->{'counter'} == $args->{'currentJumpIndex'} - 
                    $currentJumpDelta) {
                    # Jam the anchor after the <td> tag;
                    # necessary for valid HTML (which Mozilla requires)
                    $colHTML =~ s/\>/\>\<a name="curloc" \/\>/;
                    $displayedJumpMarker = 1;
                }
                $result .= $colHTML . "\n";
            }
            $result .= "    </tr>\n";
            $args->{'isNewBranch'} = 0;
        }

        if ($r && $rownum % 20 == 0) {
            $r->print($result);
            $result = "";
            $r->rflush();
        }
    } continue {
        $curRes = $it->next();
    }
    
    # Print out the part that jumps to #curloc if it exists
    # delay needed because the browser is processing the jump before
    # it finishes rendering, so it goes to the wrong place!
    # onload might be better, but this routine has no access to that.
    # On mozilla, the 0-millisecond timeout seems to prevent this;
    # it's quite likely this might fix other browsers, too, and 
    # certainly won't hurt anything.
    if ($displayedJumpMarker) {
        $result .= "<script>setTimeout(\"location += '#curloc';\", 0)</script>\n";
    }

    $result .= "</table>";
    
    if ($r) {
        $r->print($result);
        $result = "";
        $r->rflush();
    }
        
    if ($mustCloseNavMap) { $navmap->untieHashes(); } 

    return $result;
}

1;

package Apache::lonnavmaps::navmap;

=pod

lonnavmaps provides functions and objects for dealing with the
compiled course hashes generated when a user enters the course, the
Apache handler for the "Navigation Map" button, and a flexible
prepared renderer for navigation maps that are easy to use anywhere.

=head1 Object: navmap

Encapsulating the compiled nav map

navmap is an object that encapsulates a compiled course map and
provides a reasonable interface to it.

Most notably it provides a way to navigate the map sensibly and a
flexible iterator that makes it easy to write various renderers based
on nav maps.

You must obtain resource objects through the navmap object.

=head2 Methods

=over 4

=item * B<new>(navHashFile, parmHashFile, genCourseAndUserOptions,
  genMailDiscussStatus):

Binds a new navmap object to the compiled nav map hash and parm hash
given as filenames. genCourseAndUserOptions is a flag saying whether
the course options and user options hash should be generated. This is
for when you are using the parameters of the resources that require
them; see documentation in resource object
documentation. genMailDiscussStatus causes the nav map to retreive
information about the email and discussion status of
resources. Returns the navmap object if this is successful, or
B<undef> if not. You must check for undef; errors will occur when you
try to use the other methods otherwise.

=item * B<getIterator>(first, finish, filter, condition):

See iterator documentation below.

=cut

use strict;
use GDBM_File;

sub new {
    # magic invocation to create a class instance
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = {};

    $self->{NAV_HASH_FILE} = shift;
    $self->{PARM_HASH_FILE} = shift;
    $self->{GENERATE_COURSE_USER_OPT} = shift;
    $self->{GENERATE_EMAIL_DISCUSS_STATUS} = shift;

    # Resource cache stores navmap resources as we reference them. We generate
    # them on-demand so we don't pay for creating resources unless we use them.
    $self->{RESOURCE_CACHE} = {};

    # Network failure flag, if we accessed the course or user opt and
    # failed
    $self->{NETWORK_FAILURE} = 0;

    # tie the nav hash

    my %navmaphash;
    my %parmhash;
    if (!(tie(%navmaphash, 'GDBM_File', $self->{NAV_HASH_FILE},
              &GDBM_READER(), 0640))) {
        return undef;
    }
    
    if (!(tie(%parmhash, 'GDBM_File', $self->{PARM_HASH_FILE},
              &GDBM_READER(), 0640)))
    {
        untie %{$self->{PARM_HASH}};
        return undef;
    }

    $self->{NAV_HASH} = \%navmaphash;
    $self->{PARM_HASH} = \%parmhash;
    $self->{INITED} = 0;

    bless($self);
        
    return $self;
}

sub init {
    my $self = shift;
    if ($self->{INITED}) { return; }

    # If the course opt hash and the user opt hash should be generated,
    # generate them
    if ($self->{GENERATE_COURSE_USER_OPT}) {
        my $uname=$ENV{'user.name'};
        my $udom=$ENV{'user.domain'};
        my $uhome=$ENV{'user.home'};
        my $cid=$ENV{'request.course.id'};
        my $chome=$ENV{'course.'.$cid.'.home'};
        my ($cdom,$cnum)=split(/\_/,$cid);
        
        my $userprefix=$uname.'_'.$udom.'_';
        
        my %courserdatas; my %useropt; my %courseopt; my %userrdatas;
        unless ($uhome eq 'no_host') { 
# ------------------------------------------------- Get coursedata (if present)
            unless ((time-$courserdatas{$cid.'.last_cache'})<240) {
                my $reply=&Apache::lonnet::reply('dump:'.$cdom.':'.$cnum.
                                                 ':resourcedata',$chome);
                # Check for network failure
                if ( $reply =~ /no.such.host/i || $reply =~ /con_lost/i) {
                    $self->{NETWORK_FAILURE} = 1;
                } elsif ($reply!~/^error\:/) {
                    $courserdatas{$cid}=$reply;
                    $courserdatas{$cid.'.last_cache'}=time;
                }
            }
            foreach (split(/\&/,$courserdatas{$cid})) {
                my ($name,$value)=split(/\=/,$_);
                $courseopt{$userprefix.&Apache::lonnet::unescape($name)}=
                    &Apache::lonnet::unescape($value);
            }
# --------------------------------------------------- Get userdata (if present)
            unless ((time-$userrdatas{$uname.'___'.$udom.'.last_cache'})<240) {
                my $reply=&Apache::lonnet::reply('dump:'.$udom.':'.$uname.':resourcedata',$uhome);
                if ($reply!~/^error\:/) {
                    $userrdatas{$uname.'___'.$udom}=$reply;
                    $userrdatas{$uname.'___'.$udom.'.last_cache'}=time;
                }
                # check to see if network failed
                elsif ( $reply=~/no.such.host/i || $reply=~/con.*lost/i )
                {
                    $self->{NETWORK_FAILURE} = 1;
                }
            }
            foreach (split(/\&/,$userrdatas{$uname.'___'.$udom})) {
                my ($name,$value)=split(/\=/,$_);
                $useropt{$userprefix.&Apache::lonnet::unescape($name)}=
                    &Apache::lonnet::unescape($value);
            }
            $self->{COURSE_OPT} = \%courseopt;
            $self->{USER_OPT} = \%useropt;
        }
    }   

    if ($self->{GENERATE_EMAIL_DISCUSS_STATUS}) {
        my $cid=$ENV{'request.course.id'};
        my ($cdom,$cnum)=split(/\_/,$cid);
        
        my %emailstatus = &Apache::lonnet::dump('email_status');
        my $logoutTime = $emailstatus{'logout'};
        my $courseLeaveTime = $emailstatus{'logout_'.$ENV{'request.course.id'}};
        $self->{LAST_CHECK} = (($courseLeaveTime > $logoutTime) ?
                               $courseLeaveTime : $logoutTime);
        my %discussiontime = &Apache::lonnet::dump('discussiontimes', 
                                                   $cdom, $cnum);
        my %feedback=();
        my %error=();
        my $keys = &Apache::lonnet::reply('keys:'.
                                          $ENV{'user.domain'}.':'.
                                          $ENV{'user.name'}.':nohist_email',
                                          $ENV{'user.home'});

        foreach my $msgid (split(/\&/, $keys)) {
            $msgid=&Apache::lonnet::unescape($msgid);
            my $plain=&Apache::lonnet::unescape(&Apache::lonnet::unescape($msgid));
            if ($plain=~/(Error|Feedback) \[([^\]]+)\]/) {
                my ($what,$url)=($1,$2);
                my %status=
                    &Apache::lonnet::get('email_status',[$msgid]);
                if ($status{$msgid}=~/^error\:/) { 
                    $status{$msgid}=''; 
                }
                
                if (($status{$msgid} eq 'new') || 
                    (!$status{$msgid})) { 
                    if ($what eq 'Error') {
                        $error{$url}.=','.$msgid; 
                    } else {
                        $feedback{$url}.=','.$msgid;
                    }
                }
            }
        }
        
        $self->{FEEDBACK} = \%feedback;
        $self->{ERROR_MSG} = \%error; # what is this? JB
        $self->{DISCUSSION_TIME} = \%discussiontime;
        $self->{EMAIL_STATUS} = \%emailstatus;
        
    }    

    $self->{PARM_CACHE} = {};
    $self->{INITED} = 1;
}

# Internal function: Takes a key to look up in the nav hash and implements internal
# memory caching of that key.
sub navhash {
    my $self = shift; my $key = shift;
    return $self->{NAV_HASH}->{$key};
}

# Checks to see if coursemap is defined, matching test in old lonnavmaps
sub courseMapDefined {
    my $self = shift;
    my $uri = &Apache::lonnet::clutter($ENV{'request.course.uri'});

    my $firstres = $self->navhash("map_start_$uri");
    my $lastres = $self->navhash("map_finish_$uri");
    return $firstres && $lastres;
}

sub getIterator {
    my $self = shift;
    my $iterator = Apache::lonnavmaps::iterator->new($self, shift, shift,
                                                     shift, undef, shift);
    return $iterator;
}

# unties the hash when done
sub untieHashes {
    my $self = shift;
    untie %{$self->{NAV_HASH}};
    untie %{$self->{PARM_HASH}};
}

# Private method: Does the given resource (as a symb string) have
# current discussion? Returns 0 if chat/mail data not extracted.
sub hasDiscussion {
    my $self = shift;
    my $symb = shift;
    if (!defined($self->{DISCUSSION_TIME})) { return 0; }

    #return defined($self->{DISCUSSION_TIME}->{$symb});
    return $self->{DISCUSSION_TIME}->{$symb} >
           $self->{LAST_CHECK};
}

# Private method: Does the given resource (as a symb string) have
# current feedback? Returns the string in the feedback hash, which
# will be false if it does not exist.
sub getFeedback { 
    my $self = shift;
    my $symb = shift;

    if (!defined($self->{FEEDBACK})) { return ""; }
    
    return $self->{FEEDBACK}->{$symb};
}

# Private method: Get the errors for that resource (by source).
sub getErrors { 
    my $self = shift;
    my $src = shift;
    
    if (!defined($self->{ERROR_MSG})) { return ""; }
    return $self->{ERROR_MSG}->{$src};
}

=pod

=item * B<getById>(id):

Based on the ID of the resource (1.1, 3.2, etc.), get a resource
object for that resource. This method, or other methods that use it
(as in the resource object) is the only proper way to obtain a
resource object.

=item * B<getBySymb>(symb):

Based on the symb of the resource, get a resource object for that
resource. This is one of the proper ways to get a resource object.

=item * B<getMapByMapPc>(map_pc):

Based on the map_pc of the resource, get a resource object for
the given map. This is one of the proper ways to get a resource object.

=cut

# The strategy here is to cache the resource objects, and only construct them
# as we use them. The real point is to prevent reading any more from the tied
# hash then we have to, which should hopefully alleviate speed problems.
# Caching is just an incidental detail I throw in because it makes sense.

sub getById {
    my $self = shift;
    my $id = shift;

    if (defined ($self->{RESOURCE_CACHE}->{$id}))
    {
        return $self->{RESOURCE_CACHE}->{$id};
    }

    # resource handles inserting itself into cache.
    # Not clear why the quotes are necessary, but as of this
    # writing it doesn't work without them.
    return "Apache::lonnavmaps::resource"->new($self, $id);
}

sub getBySymb {
    my $self = shift;
    my $symb = shift;
    my ($mapUrl, $id, $filename) = split (/___/, $symb);
    my $map = $self->getResourceByUrl($mapUrl);
    return $self->getById($map->map_pc() . '.' . $id);
}

sub getByMapPc {
    my $self = shift;
    my $map_pc = shift;
    my $map_id = $self->{NAV_HASH}->{'map_id_' . $map_pc};
    $map_id = $self->{NAV_HASH}->{'ids_' . $map_id};
    return $self->getById($map_id);
}

=pod

=item * B<firstResource>():

Returns a resource object reference corresponding to the first
resource in the navmap.

=cut

sub firstResource {
    my $self = shift;
    my $firstResource = $self->navhash('map_start_' .
                     &Apache::lonnet::clutter($ENV{'request.course.uri'}));
    return $self->getById($firstResource);
}

=pod

=item * B<finishResource>():

Returns a resource object reference corresponding to the last resource
in the navmap.

=cut

sub finishResource {
    my $self = shift;
    my $firstResource = $self->navhash('map_finish_' .
                     &Apache::lonnet::clutter($ENV{'request.course.uri'}));
    return $self->getById($firstResource);
}

# Parmval reads the parm hash and cascades the lookups. parmval_real does
# the actual lookup; parmval caches the results.
sub parmval {
    my $self = shift;
    my ($what,$symb)=@_;
    my $hashkey = $what."|||".$symb;

    if (defined($self->{PARM_CACHE}->{$hashkey})) {
        return $self->{PARM_CACHE}->{$hashkey};
    }

    my $result = $self->parmval_real($what, $symb);
    $self->{PARM_CACHE}->{$hashkey} = $result;
    return $result;
}

sub parmval_real {
    my $self = shift;
    my ($what,$symb) = @_;

    my $cid=$ENV{'request.course.id'};
    my $csec=$ENV{'request.course.sec'};
    my $uname=$ENV{'user.name'};
    my $udom=$ENV{'user.domain'};

    unless ($symb) { return ''; }
    my $result='';

    my ($mapname,$id,$fn)=split(/\_\_\_/,$symb);

# ----------------------------------------------------- Cascading lookup scheme
    my $rwhat=$what;
    $what=~s/^parameter\_//;
    $what=~s/\_/\./;

    my $symbparm=$symb.'.'.$what;
    my $mapparm=$mapname.'___(all).'.$what;
    my $usercourseprefix=$uname.'_'.$udom.'_'.$cid;

    my $seclevel= $usercourseprefix.'.['.$csec.'].'.$what;
    my $seclevelr=$usercourseprefix.'.['.$csec.'].'.$symbparm;
    my $seclevelm=$usercourseprefix.'.['.$csec.'].'.$mapparm;

    my $courselevel= $usercourseprefix.'.'.$what;
    my $courselevelr=$usercourseprefix.'.'.$symbparm;
    my $courselevelm=$usercourseprefix.'.'.$mapparm;

    my $useropt = $self->{USER_OPT};
    my $courseopt = $self->{COURSE_OPT};
    my $parmhash = $self->{PARM_HASH};

# ---------------------------------------------------------- first, check user
    if ($uname and defined($useropt)) {
        if (defined($$useropt{$courselevelr})) { return $$useropt{$courselevelr}; }
        if (defined($$useropt{$courselevelm})) { return $$useropt{$courselevelm}; }
        if (defined($$useropt{$courselevel})) { return $$useropt{$courselevel}; }
    }

# ------------------------------------------------------- second, check course
    if ($csec and defined($courseopt)) {
        if (defined($$courseopt{$seclevelr})) { return $$courseopt{$seclevelr}; }
        if (defined($$courseopt{$seclevelm})) { return $$courseopt{$seclevelm}; }
        if (defined($$courseopt{$seclevel})) { return $$courseopt{$seclevel}; }
    }

    if (defined($courseopt)) {
        if (defined($$courseopt{$courselevelr})) { return $$courseopt{$courselevelr}; }
        if (defined($$courseopt{$courselevelm})) { return $$courseopt{$courselevelm}; }
        if (defined($$courseopt{$courselevel})) { return $$courseopt{$courselevel}; }
    }

# ----------------------------------------------------- third, check map parms

    my $thisparm=$$parmhash{$symbparm};
    if (defined($thisparm)) { return $thisparm; }

# ----------------------------------------------------- fourth , check default

    my $default=&Apache::lonnet::metadata($fn,$rwhat.'.default');
    if (defined($default)) { return $default}

# --------------------------------------------------- fifth , cascade up parts

    my ($space,@qualifier)=split(/\./,$rwhat);
    my $qualifier=join('.',@qualifier);
    unless ($space eq '0') {
	my @parts=split(/_/,$space);
	my $id=pop(@parts);
	my $part=join('_',@parts);
	if ($part eq '') { $part='0'; }
	my $partgeneral=$self->parmval($part.".$qualifier",$symb);
	if (defined($partgeneral)) { return $partgeneral; }
    }
    return '';
}

=pod

=item * B<getResourceByUrl>(url):

Retrieves a resource object by URL of the resource. If passed a
resource object, it will simply return it, so it is safe to use this
method in code like "$res = $navmap->getResourceByUrl($res)", if
you're not sure if $res is already an object, or just a URL. If the
resource appears multiple times in the course, only the first instance
will be returned. As a result, this is probably useful only for maps.

=item * B<retrieveResources>(map, filterFunc, recursive, bailout):

The map is a specification of a map to retreive the resources from,
either as a url or as an object. The filterFunc is a reference to a
function that takes a resource object as its one argument and returns
true if the resource should be included, or false if it should not
be. If recursive is true, the map will be recursively examined,
otherwise it will not be. If bailout is true, the function will return
as soon as it finds a resource, if false it will finish. By default,
the map is the top-level map of the course, filterFunc is a function
that always returns 1, recursive is true, bailout is false. The
resources will be returned in a list containing the resource objects
for the corresponding resources, with B<no structure information> in
the list; regardless of branching, recursion, etc., it will be a flat
list.

Thus, this is suitable for cases where you don't want the structure,
just a list of all resources. It is also suitable for finding out how
many resources match a given description; for this use, if all you
want to know is if I<any> resources match the description, the bailout
parameter will allow you to avoid potentially expensive enumeration of
all matching resources.

=item * B<hasResources>(map, filterFunc, recursive):

Convience method for

 scalar(retrieveResources($map, $filterFunc, $recursive, 1)) > 0

which will tell whether the map has resources matching the description
in the filter function.

=cut

sub getResourceByUrl {
    my $self = shift;
    my $resUrl = shift;

    if (ref($resUrl)) { return $resUrl; }

    $resUrl = &Apache::lonnet::clutter($resUrl);
    my $resId = $self->{NAV_HASH}->{'ids_' . $resUrl};
    if ($resId =~ /,/) {
        $resId = (split (/,/, $resId))[0];
    }
    if (!$resId) { return ''; }
    return $self->getById($resId);
}

sub retrieveResources {
    my $self = shift;
    my $map = shift;
    my $filterFunc = shift;
    if (!defined ($filterFunc)) {
        $filterFunc = sub {return 1;};
    }
    my $recursive = shift;
    if (!defined($recursive)) { $recursive = 1; }
    my $bailout = shift;
    if (!defined($bailout)) { $bailout = 0; }

    # Create the necessary iterator.
    if (!ref($map)) { # assume it's a url of a map.
        $map = $self->getResourceByUrl($map);
    }

    # Check the map's validity.
    if (!$map || !$map->is_map()) {
        # Oh, to throw an exception.... how I'd love that!
        return ();
    }

    # Get an iterator.
    my $it = $self->getIterator($map->map_start(), $map->map_finish(),
                                !$recursive);

    my @resources = ();

    # Run down the iterator and collect the resources.
    my $depth = 1;
    $it->next();
    my $curRes = $it->next();

    while ($depth > 0) {
        if ($curRes == $it->BEGIN_MAP()) {
            $depth++;
        }
        if ($curRes == $it->END_MAP()) {
            $depth--;
        }
        
        if (ref($curRes)) {
            if (!&$filterFunc($curRes)) {
                next;
            }

            push @resources, $curRes;

            if ($bailout) {
                return @resources;
            }
        }

        $curRes = $it->next();
    }

    return @resources;
}

sub hasResource {
    my $self = shift;
    my $map = shift;
    my $filterFunc = shift;
    my $recursive = shift;
    
    return scalar($self->retrieveResources($map, $filterFunc, $recursive, 1)) > 0;
}

1;

package Apache::lonnavmaps::iterator;

=pod

=back

=head1 Object: navmap Iterator

An I<iterator> encapsulates the logic required to traverse a data
structure. navmap uses an iterator to traverse the course map
according to the criteria you wish to use.

To obtain an iterator, call the B<getIterator>() function of a
B<navmap> object. (Do not instantiate Apache::lonnavmaps::iterator
directly.) This will return a reference to the iterator:

C<my $resourceIterator = $navmap-E<gt>getIterator();>

To get the next thing from the iterator, call B<next>:

C<my $nextThing = $resourceIterator-E<gt>next()>

getIterator behaves as follows:

=over 4

=item * B<getIterator>(firstResource, finishResource, filterHash, condition, forceTop, returnTopMap):

All parameters are optional. firstResource is a resource reference
corresponding to where the iterator should start. It defaults to
navmap->firstResource() for the corresponding nav map. finishResource
corresponds to where you want the iterator to end, defaulting to
navmap->finishResource(). filterHash is a hash used as a set
containing strings representing the resource IDs, defaulting to
empty. Condition is a 1 or 0 that sets what to do with the filter
hash: If a 0, then only resource that exist IN the filterHash will be
recursed on. If it is a 1, only resources NOT in the filterHash will
be recursed on. Defaults to 0. forceTop is a boolean value. If it is
false (default), the iterator will only return the first level of map
that is not just a single, 'redirecting' map. If true, the iterator
will return all information, starting with the top-level map,
regardless of content. returnTopMap, if true (default false), will
cause the iterator to return the top-level map object (resource 0.0)
before anything else.

Thus, by default, only top-level resources will be shown. Change the
condition to a 1 without changing the hash, and all resources will be
shown. Changing the condition to 1 and including some values in the
hash will allow you to selectively suppress parts of the navmap, while
leaving it on 0 and adding things to the hash will allow you to
selectively add parts of the nav map. See the handler code for
examples.

The iterator will return either a reference to a resource object, or a
token representing something in the map, such as the beginning of a
new branch. The possible tokens are:

=over 4

=item * BEGIN_MAP:

A new map is being recursed into. This is returned I<after> the map
resource itself is returned.

=item * END_MAP:

The map is now done.

=item * BEGIN_BRANCH:

A branch is now starting. The next resource returned will be the first
in that branch.

=item * END_BRANCH:

The branch is now done.

=back

The tokens are retreivable via methods on the iterator object, i.e.,
$iterator->END_MAP.

Maps can contain empty resources. The iterator will automatically skip
over such resources, but will still treat the structure
correctly. Thus, a complicated map with several branches, but
consisting entirely of empty resources except for one beginning or
ending resource, will cause a lot of BRANCH_STARTs and BRANCH_ENDs,
but only one resource will be returned.

=back

=cut

# Here are the tokens for the iterator:

sub BEGIN_MAP { return 1; }    # begining of a new map
sub END_MAP { return 2; }      # end of the map
sub BEGIN_BRANCH { return 3; } # beginning of a branch
sub END_BRANCH { return 4; }   # end of a branch
sub FORWARD { return 1; }      # go forward
sub BACKWARD { return 2; }

sub min {
    (my $a, my $b) = @_;
    if ($a < $b) { return $a; } else { return $b; }
}

# In the CVS repository, documentation of this algorithm is included 
# in /doc/lonnavdocs, as a PDF and .tex source. Markers like **1**
# will reference the same location in the text as the part of the
# algorithm is running through.

sub new {
    # magic invocation to create a class instance
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = {};

    $self->{NAV_MAP} = shift;
    return undef unless ($self->{NAV_MAP});

    # Handle the parameters
    $self->{FIRST_RESOURCE} = shift || $self->{NAV_MAP}->firstResource();
    $self->{FINISH_RESOURCE} = shift || $self->{NAV_MAP}->finishResource();

    # If the given resources are just the ID of the resource, get the
    # objects
    if (!ref($self->{FIRST_RESOURCE})) { $self->{FIRST_RESOURCE} = 
             $self->{NAV_MAP}->getById($self->{FIRST_RESOURCE}); }
    if (!ref($self->{FINISH_RESOURCE})) { $self->{FINISH_RESOURCE} = 
             $self->{NAV_MAP}->getById($self->{FINISH_RESOURCE}); }

    $self->{FILTER} = shift;

    # A hash, used as a set, of resource already seen
    $self->{ALREADY_SEEN} = shift;
    if (!defined($self->{ALREADY_SEEN})) { $self->{ALREADY_SEEN} = {} };
    $self->{CONDITION} = shift;

    # Do we want to automatically follow "redirection" maps?
    $self->{FORCE_TOP} = shift;

    # Do we want to return the top-level map object (resource 0.0)?
    $self->{RETURN_0} = shift;
    # have we done that yet?
    $self->{HAVE_RETURNED_0} = 0;

    # Now, we need to pre-process the map, by walking forward and backward
    # over the parts of the map we're going to look at.

    # The processing steps are exactly the same, except for a few small 
    # changes, so I bundle those up in the following list of two elements:
    # (direction_to_iterate, VAL_name, next_resource_method_to_call,
    # first_resource).
    # This prevents writing nearly-identical code twice.
    my @iterations = ( [FORWARD(), 'TOP_DOWN_VAL', 'getNext', 
                        'FIRST_RESOURCE'],
                       [BACKWARD(), 'BOT_UP_VAL', 'getPrevious', 
                        'FINISH_RESOURCE'] );

    my $maxDepth = 0; # tracks max depth

    # If there is only one resource in this map, and it's a map, we
    # want to remember that, so the user can ask for the first map
    # that isn't just a redirector.
    my $resource; my $resourceCount = 0;

    # **1**

    foreach my $pass (@iterations) {
        my $direction = $pass->[0];
        my $valName = $pass->[1];
        my $nextResourceMethod = $pass->[2];
        my $firstResourceName = $pass->[3];

        my $iterator = Apache::lonnavmaps::DFSiterator->new($self->{NAV_MAP}, 
                                                            $self->{FIRST_RESOURCE},
                                                            $self->{FINISH_RESOURCE},
                                                            {}, undef, 0, $direction);
    
        # prime the recursion
        $self->{$firstResourceName}->{DATA}->{$valName} = 0;
        my $depth = 0;
        $iterator->next();
        my $curRes = $iterator->next();
        while ($depth > -1) {
            if ($curRes == $iterator->BEGIN_MAP()) { $depth++; }
            if ($curRes == $iterator->END_MAP()) { $depth--; }
        
            if (ref($curRes)) {
                # If there's only one resource, this will save it
                # we have to filter empty resources from consideration here,
                # or even "empty", redirecting maps have two (start & finish)
                # or three (start, finish, plus redirector)
                if($direction == FORWARD && $curRes->src()) { 
                    $resource = $curRes; $resourceCount++; 
                }
                my $resultingVal = $curRes->{DATA}->{$valName};
                my $nextResources = $curRes->$nextResourceMethod();
                my $nextCount = scalar(@{$nextResources});

                if ($nextCount == 1) { # **3**
                    my $current = $nextResources->[0]->{DATA}->{$valName} || 999999999;
                    $nextResources->[0]->{DATA}->{$valName} = min($resultingVal, $current);
                }
                
                if ($nextCount > 1) { # **4**
                    foreach my $res (@{$nextResources}) {
                        my $current = $res->{DATA}->{$valName} || 999999999;
                        $res->{DATA}->{$valName} = min($current, $resultingVal + 1);
                    }
                }
            }
            
            # Assign the final val (**2**)
            if (ref($curRes) && $direction == BACKWARD()) {
                my $finalDepth = min($curRes->{DATA}->{TOP_DOWN_VAL},
                                     $curRes->{DATA}->{BOT_UP_VAL});
                
                $curRes->{DATA}->{DISPLAY_DEPTH} = $finalDepth;
                if ($finalDepth > $maxDepth) {$maxDepth = $finalDepth;}
            }
        } continue {
            $curRes = $iterator->next();
        }
    }

    # Check: Was this only one resource, a map?
    if ($resourceCount == 1 && $resource->is_map() && !$self->{FORCE_TOP}) { 
        my $firstResource = $resource->map_start();
        my $finishResource = $resource->map_finish();
        return 
            Apache::lonnavmaps::iterator->new($self->{NAV_MAP}, $firstResource,
                                              $finishResource, $self->{FILTER},
                                              $self->{ALREADY_SEEN}, 
                                              $self->{CONDITION}, 0);
        
    }

    # Set up some bookkeeping information.
    $self->{CURRENT_DEPTH} = 0;
    $self->{MAX_DEPTH} = $maxDepth;
    $self->{STACK} = [];
    $self->{RECURSIVE_ITERATOR_FLAG} = 0;

    for (my $i = 0; $i <= $self->{MAX_DEPTH}; $i++) {
        push @{$self->{STACK}}, [];
    }

    # Prime the recursion w/ the first resource **5**
    push @{$self->{STACK}->[0]}, $self->{FIRST_RESOURCE};
    $self->{ALREADY_SEEN}->{$self->{FIRST_RESOURCE}->{ID}} = 1;

    bless ($self);

    return $self;
}

sub next {
    my $self = shift;

    # If we want to return the top-level map object, and haven't yet,
    # do so.
    if ($self->{RETURN_0} && !$self->{HAVE_RETURNED_0}) {
        $self->{HAVE_RETURNED_0} = 1;
        return $self->{NAV_MAP}->getById('0.0');
    }

    if ($self->{RECURSIVE_ITERATOR_FLAG}) {
        # grab the next from the recursive iterator 
        my $next = $self->{RECURSIVE_ITERATOR}->next();

        # is it a begin or end map? If so, update the depth
        if ($next == BEGIN_MAP() ) { $self->{RECURSIVE_DEPTH}++; }
        if ($next == END_MAP() ) { $self->{RECURSIVE_DEPTH}--; }

        # Are we back at depth 0? If so, stop recursing
        if ($self->{RECURSIVE_DEPTH} == 0) {
            $self->{RECURSIVE_ITERATOR_FLAG} = 0;
        }

        return $next;
    }

    if (defined($self->{FORCE_NEXT})) {
        my $tmp = $self->{FORCE_NEXT};
        $self->{FORCE_NEXT} = undef;
        return $tmp;
    }

    # Have we not yet begun? If not, return BEGIN_MAP and
    # remember we've started.
    if ( !$self->{STARTED} ) { 
        $self->{STARTED} = 1;
        return $self->BEGIN_MAP();
    }

    # Here's the guts of the iterator.
    
    # Find the next resource, if any.
    my $found = 0;
    my $i = $self->{MAX_DEPTH};
    my $newDepth;
    my $here;
    while ( $i >= 0 && !$found ) {
        if ( scalar(@{$self->{STACK}->[$i]}) > 0 ) { # **6**
            $here = pop @{$self->{STACK}->[$i]}; # **7**
            $found = 1;
            $newDepth = $i;
        }
        $i--;
    }

    # If we still didn't find anything, we're done.
    if ( !$found ) {
        # We need to get back down to the correct branch depth
        if ( $self->{CURRENT_DEPTH} > 0 ) {
            $self->{CURRENT_DEPTH}--;
            return END_BRANCH();
        } else {
            return END_MAP();
        }
    }

    # If this is not a resource, it must be an END_BRANCH marker we want
    # to return directly.
    if (!ref($here)) { # **8**
        if ($here == END_BRANCH()) { # paranoia, in case of later extension
            $self->{CURRENT_DEPTH}--;
            return $here;
        }
    }

    # Otherwise, it is a resource and it's safe to store in $self->{HERE}
    $self->{HERE} = $here;

    # Get to the right level
    if ( $self->{CURRENT_DEPTH} > $newDepth ) {
        push @{$self->{STACK}->[$newDepth]}, $here;
        $self->{CURRENT_DEPTH}--;
        return END_BRANCH();
    }
    if ( $self->{CURRENT_DEPTH} < $newDepth) {
        push @{$self->{STACK}->[$newDepth]}, $here;
        $self->{CURRENT_DEPTH}++;
        return BEGIN_BRANCH();
    }

    # If we made it here, we have the next resource, and we're at the
    # right branch level. So let's examine the resource for where
    # we can get to from here.

    # So we need to look at all the resources we can get to from here,
    # categorize them if we haven't seen them, remember if we have a new
    my $nextUnfiltered = $here->getNext();
    my $maxDepthAdded = -1;
    
    for (@$nextUnfiltered) {
        if (!defined($self->{ALREADY_SEEN}->{$_->{ID}})) {
            my $depth = $_->{DATA}->{DISPLAY_DEPTH};
            push @{$self->{STACK}->[$depth]}, $_;
            $self->{ALREADY_SEEN}->{$_->{ID}} = 1;
            if ($maxDepthAdded < $depth) { $maxDepthAdded = $depth; }
        }
    }

    # Is this the end of a branch? If so, all of the resources examined above
    # led to lower levels then the one we are currently at, so we push a END_BRANCH
    # marker onto the stack so we don't forget.
    # Example: For the usual A(BC)(DE)F case, when the iterator goes down the
    # BC branch and gets to C, it will see F as the only next resource, but it's
    # one level lower. Thus, this is the end of the branch, since there are no
    # more resources added to this level or above.
    # We don't do this if the examined resource is the finish resource,
    # because the condition given above is true, but the "END_MAP" will
    # take care of things and we should already be at depth 0.
    my $isEndOfBranch = $maxDepthAdded < $self->{CURRENT_DEPTH};
    if ($isEndOfBranch && $here != $self->{FINISH_RESOURCE}) { # **9**
        push @{$self->{STACK}->[$self->{CURRENT_DEPTH}]}, END_BRANCH();
    }

    # That ends the main iterator logic. Now, do we want to recurse
    # down this map (if this resource is a map)?
    if ($self->{HERE}->is_map() &&
        (defined($self->{FILTER}->{$self->{HERE}->map_pc()}) xor $self->{CONDITION})) {
        $self->{RECURSIVE_ITERATOR_FLAG} = 1;
        my $firstResource = $self->{HERE}->map_start();
        my $finishResource = $self->{HERE}->map_finish();

        $self->{RECURSIVE_ITERATOR} = 
            Apache::lonnavmaps::iterator->new($self->{NAV_MAP}, $firstResource,
                                              $finishResource, $self->{FILTER},
                                              $self->{ALREADY_SEEN}, $self->{CONDITION});
    }

    # If this is a blank resource, don't actually return it.
    # Should you ever find you need it, make sure to add an option to the code
    #  that you can use; other things depend on this behavior.
    my $browsePriv = $self->{HERE}->browsePriv();
    if (!$self->{HERE}->src() || 
        (!($browsePriv eq 'F') && !($browsePriv eq '2')) ) {
        return $self->next();
    }

    return $self->{HERE};

}

=pod

The other method available on the iterator is B<getStack>, which
returns an array populated with the current 'stack' of maps, as
references to the resource objects. Example: This is useful when
making the navigation map, as we need to check whether we are under a
page map to see if we need to link directly to the resource, or to the
page. The first elements in the array will correspond to the top of
the stack (most inclusive map).

=cut

sub getStack {
    my $self=shift;

    my @stack;

    $self->populateStack(\@stack);

    return \@stack;
}

# Private method: Calls the iterators recursively to populate the stack.
sub populateStack {
    my $self=shift;
    my $stack = shift;

    push @$stack, $self->{HERE} if ($self->{HERE});

    if ($self->{RECURSIVE_ITERATOR_FLAG}) {
        $self->{RECURSIVE_ITERATOR}->populateStack($stack);
    }
}

1;

package Apache::lonnavmaps::DFSiterator;

# Not documented in the perldoc: This is a simple iterator that just walks
#  through the nav map and presents the resources in a depth-first search
#  fashion, ignorant of conditionals, randomized resources, etc. It presents
#  BEGIN_MAP and END_MAP, but does not understand branches at all. It is
#  useful for pre-processing of some kind, and is in fact used by the main
#  iterator that way, but that's about it.
# One could imagine merging this into the init routine of the main iterator,
#  but this might as well be left seperate, since it is possible some other
#  use might be found for it. - Jeremy

# Unlike the main iterator, this DOES return all resources, even blank ones.
#  The main iterator needs them to correctly preprocess the map.

sub BEGIN_MAP { return 1; }    # begining of a new map
sub END_MAP { return 2; }      # end of the map
sub FORWARD { return 1; }      # go forward
sub BACKWARD { return 2; }

# Params: Nav map ref, first resource id/ref, finish resource id/ref,
#         filter hash ref (or undef), already seen hash or undef, condition
#         (as in main iterator), direction FORWARD or BACKWARD (undef->forward).
sub new {
    # magic invocation to create a class instance
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = {};

    $self->{NAV_MAP} = shift;
    return undef unless ($self->{NAV_MAP});

    $self->{FIRST_RESOURCE} = shift || $self->{NAV_MAP}->firstResource();
    $self->{FINISH_RESOURCE} = shift || $self->{NAV_MAP}->finishResource();

    # If the given resources are just the ID of the resource, get the
    # objects
    if (!ref($self->{FIRST_RESOURCE})) { $self->{FIRST_RESOURCE} = 
             $self->{NAV_MAP}->getById($self->{FIRST_RESOURCE}); }
    if (!ref($self->{FINISH_RESOURCE})) { $self->{FINISH_RESOURCE} = 
             $self->{NAV_MAP}->getById($self->{FINISH_RESOURCE}); }

    $self->{FILTER} = shift;

    # A hash, used as a set, of resource already seen
    $self->{ALREADY_SEEN} = shift;
     if (!defined($self->{ALREADY_SEEN})) { $self->{ALREADY_SEEN} = {} };
    $self->{CONDITION} = shift;
    $self->{DIRECTION} = shift || FORWARD();

    # Flag: Have we started yet?
    $self->{STARTED} = 0;

    # Should we continue calling the recursive iterator, if any?
    $self->{RECURSIVE_ITERATOR_FLAG} = 0;
    # The recursive iterator, if any
    $self->{RECURSIVE_ITERATOR} = undef;
    # Are we recursing on a map, or a branch?
    $self->{RECURSIVE_MAP} = 1; # we'll manually unset this when recursing on branches
    # And the count of how deep it is, so that this iterator can keep track of
    # when to pick back up again.
    $self->{RECURSIVE_DEPTH} = 0;

    # For keeping track of our branches, we maintain our own stack
    $self->{STACK} = [];

    # Start with the first resource
    if ($self->{DIRECTION} == FORWARD) {
        push @{$self->{STACK}}, $self->{FIRST_RESOURCE};
    } else {
        push @{$self->{STACK}}, $self->{FINISH_RESOURCE};
    }

    bless($self);
    return $self;
}

sub next {
    my $self = shift;
    
    # Are we using a recursive iterator? If so, pull from that and
    # watch the depth; we want to resume our level at the correct time.
    if ($self->{RECURSIVE_ITERATOR_FLAG}) {
        # grab the next from the recursive iterator
        my $next = $self->{RECURSIVE_ITERATOR}->next();
        
        # is it a begin or end map? Update depth if so
        if ($next == BEGIN_MAP() ) { $self->{RECURSIVE_DEPTH}++; }
        if ($next == END_MAP() ) { $self->{RECURSIVE_DEPTH}--; }

        # Are we back at depth 0? If so, stop recursing.
        if ($self->{RECURSIVE_DEPTH} == 0) {
            $self->{RECURSIVE_ITERATOR_FLAG} = 0;
        }
        
        return $next;
    }

    # Is there a current resource to grab? If not, then return
    # END_MAP, which will end the iterator.
    if (scalar(@{$self->{STACK}}) == 0) {
        return $self->END_MAP();
    }

    # Have we not yet begun? If not, return BEGIN_MAP and 
    # remember that we've started.
    if ( !$self->{STARTED} ) {
        $self->{STARTED} = 1;
        return $self->BEGIN_MAP;
    }

    # Get the next resource in the branch
    $self->{HERE} = pop @{$self->{STACK}};

    # remember that we've seen this, so we don't return it again later
    $self->{ALREADY_SEEN}->{$self->{HERE}->{ID}} = 1;
    
    # Get the next possible resources
    my $nextUnfiltered;
    if ($self->{DIRECTION} == FORWARD()) {
        $nextUnfiltered = $self->{HERE}->getNext();
    } else {
        $nextUnfiltered = $self->{HERE}->getPrevious();
    }
    my $next = [];

    # filter the next possibilities to remove things we've 
    # already seen.
    foreach (@$nextUnfiltered) {
        if (!defined($self->{ALREADY_SEEN}->{$_->{ID}})) {
            push @$next, $_;
        }
    }

    while (@$next) {
        # copy the next possibilities over to the stack
        push @{$self->{STACK}}, shift @$next;
    }

    # If this is a map and we want to recurse down it... (not filtered out)
    if ($self->{HERE}->is_map() && 
         (defined($self->{FILTER}->{$self->{HERE}->map_pc()}) xor $self->{CONDITION})) { 
        $self->{RECURSIVE_ITERATOR_FLAG} = 1;
        my $firstResource = $self->{HERE}->map_start();
        my $finishResource = $self->{HERE}->map_finish();

        $self->{RECURSIVE_ITERATOR} =
          Apache::lonnavmaps::DFSiterator->new ($self->{NAV_MAP}, $firstResource, 
                     $finishResource, $self->{FILTER}, $self->{ALREADY_SEEN},
                                             $self->{CONDITION}, $self->{DIRECTION});
    }

    return $self->{HERE};
}

# Identical to the full iterator methods of the same name. Hate to copy/paste
# but I also hate to "inherit" either iterator from the other.

sub getStack {
    my $self=shift;

    my @stack;

    $self->populateStack(\@stack);

    return \@stack;
}

# Private method: Calls the iterators recursively to populate the stack.
sub populateStack {
    my $self=shift;
    my $stack = shift;

    push @$stack, $self->{HERE} if ($self->{HERE});

    if ($self->{RECURSIVE_ITERATOR_FLAG}) {
        $self->{RECURSIVE_ITERATOR}->populateStack($stack);
    }
}

1;

package Apache::lonnavmaps::resource;

use Apache::lonnet;

=pod

=head1 Object: resource

A resource object encapsulates a resource in a resource map, allowing
easy manipulation of the resource, querying the properties of the
resource (including user properties), and represents a reference that
can be used as the canonical representation of the resource by
lonnavmap clients like renderers.

A resource only makes sense in the context of a navmap, as some of the
data is stored in the navmap object.

You will probably never need to instantiate this object directly. Use
Apache::lonnavmaps::navmap, and use the "start" method to obtain the
starting resource.

Resource objects respect the parameter_hiddenparts, which suppresses 
various parts according to the wishes of the map author. As of this
writing, there is no way to override this parameter, and suppressed
parts will never be returned, nor will their response types or ids be
stored.

=head2 Public Members

resource objects have a hash called DATA ($resourceRef->{DATA}) that
you can store whatever you want in. This allows you to easily do
two-pass algorithms without worrying about managing your own
resource->data hash.

=head2 Methods

=over 4

=item * B<new>($navmapRef, $idString):

The first arg is a reference to the parent navmap object. The second
is the idString of the resource itself. Very rarely, if ever, called
directly. Use the nav map->getByID() method.

=back

=cut

sub new {
    # magic invocation to create a class instance
    my $proto = shift;
    my $class = ref($proto) || $proto;
    my $self = {};

    $self->{NAV_MAP} = shift;
    $self->{ID} = shift;

    # Store this new resource in the parent nav map's cache.
    $self->{NAV_MAP}->{RESOURCE_CACHE}->{$self->{ID}} = $self;
    $self->{RESOURCE_ERROR} = 0;

    # A hash that can be used by two-pass algorithms to store data
    # about this resource in. Not used by the resource object
    # directly.
    $self->{DATA} = {};
   
    bless($self);
    
    return $self;
}

# private function: simplify the NAV_HASH lookups we keep doing
# pass the name, and to automatically append my ID, pass a true val on the
# second param
sub navHash {
    my $self = shift;
    my $param = shift;
    my $id = shift;
    return $self->{NAV_MAP}->navhash($param . ($id?$self->{ID}:""));
}

=pod

B<Metadata Retreival>

These are methods that help you retrieve metadata about the resource:
Method names are based on the fields in the compiled course
representation.

=over 4

=item * B<compTitle>:

Returns a "composite title", that is equal to $res->title() if the
resource has a title, and is otherwise the last part of the URL (e.g.,
"problem.problem").

=item * B<ext>:

Returns true if the resource is external.

=item * B<goesto>:

Returns the "goesto" value from the compiled nav map. (It is likely
you want to use B<getNext> instead.)

=item * B<kind>:

Returns the kind of the resource from the compiled nav map.

=item * B<randomout>:

Returns true if this resource was chosen to NOT be shown to the user
by the random map selection feature. In other words, this is usually
false.

=item * B<randompick>:

Returns true for a map if the randompick feature is being used on the
map. (?)

=item * B<src>:

Returns the source for the resource.

=item * B<symb>:

Returns the symb for the resource.

=item * B<title>:

Returns the title of the resource.

=item * B<to>:

Returns the "to" value from the compiled nav map. (It is likely you
want to use B<getNext> instead.)

=back

=cut

# These info functions can be used directly, as they don't return
# resource information.
sub comesfrom { my $self=shift; return $self->navHash("comesfrom_", 1); }
sub ext { my $self=shift; return $self->navHash("ext_", 1) eq 'true:'; }
sub from { my $self=shift; return $self->navHash("from_", 1); }
sub goesto { my $self=shift; return $self->navHash("goesto_", 1); }
sub kind { my $self=shift; return $self->navHash("kind_", 1); }
sub randomout { my $self=shift; return $self->navHash("randomout_", 1); }
sub randompick { 
    my $self = shift;
    return $self->{NAV_MAP}->{PARM_HASH}->{$self->symb .
                                               '.0.parameter_randompick'};
}
sub src { 
    my $self=shift;
    return $self->navHash("src_", 1);
}
sub symb {
    my $self=shift;
    (my $first, my $second) = $self->{ID} =~ /(\d+).(\d+)/;
    my $symbSrc = &Apache::lonnet::declutter($self->src());
    return &Apache::lonnet::declutter(
         $self->navHash('map_id_'.$first)) 
        . '___' . $second . '___' . $symbSrc;
}
sub title { my $self=shift; return $self->navHash("title_", 1); }
sub to { my $self=shift; return $self->navHash("to_", 1); }
sub compTitle {
    my $self = shift;
    my $title = $self->title();
    $title=~s/\&colon\;/\:/gs;
    if (!$title) {
        $title = $self->src();
        $title = substr($title, rindex($title, '/') + 1);
    }
    return $title;
}
=pod

B<Predicate Testing the Resource>

These methods are shortcuts to deciding if a given resource has a given property.

=over 4

=item * B<is_map>:

Returns true if the resource is a map type.

=item * B<is_problem>:

Returns true if the resource is a problem type, false
otherwise. (Looks at the extension on the src field; might need more
to work correctly.)

=item * B<is_page>:

Returns true if the resource is a page.

=item * B<is_sequence>:

Returns true if the resource is a sequence.

=back

=cut


sub is_html {
    my $self=shift;
    my $src = $self->src();
    return ($src =~ /html$/);
}
sub is_map { my $self=shift; return defined($self->navHash("is_map_", 1)); }
sub is_page {
    my $self=shift;
    my $src = $self->src();
    return ($src =~ /page$/);
}
sub is_problem {
    my $self=shift;
    my $src = $self->src();
    return ($src =~ /problem$/);
}
sub is_sequence {
    my $self=shift;
    my $src = $self->src();
    return ($src =~ /sequence$/);
}

# Private method: Shells out to the parmval in the nav map, handler parts.
sub parmval {
    my $self = shift;
    my $what = shift;
    my $part = shift;
    if (!defined($part)) { 
        $part = '0'; 
    }
    return $self->{NAV_MAP}->parmval($part.'.'.$what, $self->symb());
}

=pod

B<Map Methods>

These methods are useful for getting information about the map
properties of the resource, if the resource is a map (B<is_map>).

=over 4

=item * B<map_finish>:

Returns a reference to a resource object corresponding to the finish
resource of the map.

=item * B<map_pc>:

Returns the pc value of the map, which is the first number that
appears in the resource ID of the resources in the map, and is the
number that appears around the middle of the symbs of the resources in
that map.

=item * B<map_start>:

Returns a reference to a resource object corresponding to the start
resource of the map.

=item * B<map_type>:

Returns a string with the type of the map in it.

=back

=cut

sub map_finish {
    my $self = shift;
    my $src = $self->src();
    $src = Apache::lonnet::clutter($src);
    my $res = $self->navHash("map_finish_$src", 0);
    $res = $self->{NAV_MAP}->getById($res);
    return $res;
}
sub map_pc {
    my $self = shift;
    my $src = $self->src();
    return $self->navHash("map_pc_$src", 0);
}
sub map_start {
    my $self = shift;
    my $src = $self->src();
    $src = Apache::lonnet::clutter($src);
    my $res = $self->navHash("map_start_$src", 0);
    $res = $self->{NAV_MAP}->getById($res);
    return $res;
}
sub map_type {
    my $self = shift;
    my $pc = $self->map_pc();
    return $self->navHash("map_type_$pc", 0);
}



#####
# Property queries
#####

# These functions will be responsible for returning the CORRECT
# VALUE for the parameter, no matter what. So while they may look
# like direct calls to parmval, they can be more then that.
# So, for instance, the duedate function should use the "duedatetype"
# information, rather then the resource object user.

=pod

=head2 Resource Parameters

In order to use the resource parameters correctly, the nav map must
have been instantiated with genCourseAndUserOptions set to true, so
the courseopt and useropt is read correctly. Then, you can call these
functions to get the relevant parameters for the resource. Each
function defaults to part "0", but can be directed to another part by
passing the part as the parameter.

These methods are responsible for getting the parameter correct, not
merely reflecting the contents of the GDBM hashes. As we move towards
dates relative to other dates, these methods should be updated to
reflect that. (Then, anybody using these methods will not have to update
their code.)

=over 4

=item * B<acc>:

Get the Client IP/Name Access Control information.

=item * B<answerdate>:

Get the answer-reveal date for the problem.

=item * B<duedate>:

Get the due date for the problem.

=item * B<tries>:

Get the number of tries the student has used on the problem.

=item * B<maxtries>:

Get the number of max tries allowed.

=item * B<opendate>:

Get the open date for the problem.

=item * B<sig>:

Get the significant figures setting.

=item * B<tol>:

Get the tolerance for the problem.

=item * B<tries>:

Get the number of tries the user has already used on the problem.

=item * B<type>:

Get the question type for the problem.

=item * B<weight>:

Get the weight for the problem.

=back

=cut

sub acc {
    (my $self, my $part) = @_;
    return $self->parmval("acc", $part);
}
sub answerdate {
    (my $self, my $part) = @_;
    # Handle intervals
    if ($self->parmval("answerdate.type", $part) eq 'date_interval') {
        return $self->duedate($part) + 
            $self->parmval("answerdate", $part);
    }
    return $self->parmval("answerdate", $part);
}
sub awarded { my $self = shift; return $self->queryRestoreHash('awarded', shift); }
sub duedate {
    (my $self, my $part) = @_;
    return $self->parmval("duedate", $part);
}
sub maxtries {
    (my $self, my $part) = @_;
    return $self->parmval("maxtries", $part);
}
sub opendate {
    (my $self, my $part) = @_;
    if ($self->parmval("opendate.type", $part) eq 'date_interval') {
        return $self->duedate($part) -
            $self->parmval("opendate", $part);
    }
    return $self->parmval("opendate");
}
sub problemstatus {
    (my $self, my $part) = @_;
    return $self->parmval("problemstatus", $part);
}
sub sig {
    (my $self, my $part) = @_;
    return $self->parmval("sig", $part);
}
sub tol {
    (my $self, my $part) = @_;
    return $self->parmval("tol", $part);
}
sub tries { 
    my $self = shift; 
    my $tries = $self->queryRestoreHash('tries', shift);
    if (!defined($tries)) { return '0';}
    return $tries;
}
sub type {
    (my $self, my $part) = @_;
    return $self->parmval("type", $part);
}
sub weight { 
    my $self = shift; my $part = shift;
    return $self->parmval("weight", $part);
}

# Multiple things need this
sub getReturnHash {
    my $self = shift;
    
    if (!defined($self->{RETURN_HASH})) {
        my %tmpHash  = &Apache::lonnet::restore($self->symb());
        $self->{RETURN_HASH} = \%tmpHash;
    }
}       

######
# Status queries
######

# These methods query the status of problems.

# If we need to count parts, this function determines the number of
# parts from the metadata. When called, it returns a reference to a list
# of strings corresponding to the parts. (Thus, using it in a scalar context
# tells you how many parts you have in the problem:
# $partcount = scalar($resource->countParts());
# Don't use $self->{PARTS} directly because you don't know if it's been
# computed yet.

=pod

=head2 Resource misc

Misc. functions for the resource.

=over 4

=item * B<hasDiscussion>:

Returns a false value if there has been discussion since the user last
logged in, true if there has. Always returns false if the discussion
data was not extracted when the nav map was constructed.

=item * B<getFeedback>:

Gets the feedback for the resource and returns the raw feedback string
for the resource, or the null string if there is no feedback or the
email data was not extracted when the nav map was constructed. Usually
used like this:

 for (split(/\,/, $res->getFeedback())) {
    my $link = &Apache::lonnet::escape($_);
    ...

and use the link as appropriate.

=cut

sub hasDiscussion {
    my $self = shift;
    return $self->{NAV_MAP}->hasDiscussion($self->symb());
}

sub getFeedback {
    my $self = shift;
    my $source = $self->src();
    if ($source =~ /^\/res\//) { $source = substr $source, 5; }
    return $self->{NAV_MAP}->getFeedback($source);
}

sub getErrors {
    my $self = shift;
    my $source = $self->src();
    if ($source =~ /^\/res\//) { $source = substr $source, 5; }
    return $self->{NAV_MAP}->getErrors($source);
}

=pod

=item * B<parts>():

Returns a list reference containing sorted strings corresponding to
each part of the problem. Single part problems have only a part '0'.
Multipart problems do not return their part '0', since they typically
do not really matter. 

=item * B<countParts>():

Returns the number of parts of the problem a student can answer. Thus,
for single part problems, returns 1. For multipart, it returns the
number of parts in the problem, not including psuedo-part 0. 

=item * B<multipart>():

Returns true if the problem is multipart, false otherwise. Use this instead
of countParts if all you want is multipart/not multipart.

=item * B<responseType>($part):

Returns the response type of the part, without the word "response" on the
end. Example return values: 'string', 'essay', 'numeric', etc.

=item * B<responseIds>($part):

Retreives the response IDs for the given part as an array reference containing
strings naming the response IDs. This may be empty.

=back

=cut

sub parts {
    my $self = shift;

    if ($self->ext) { return []; }

    $self->extractParts();
    return $self->{PARTS};
}

sub countParts {
    my $self = shift;
    
    my $parts = $self->parts();

    # If I left this here, then it's not necessary.
    #my $delta = 0;
    #for my $part (@$parts) {
    #    if ($part eq '0') { $delta--; }
    #}

    if ($self->{RESOURCE_ERROR}) {
        return 0;
    }

    return scalar(@{$parts}); # + $delta;
}

sub multipart {
    my $self = shift;
    return $self->countParts() > 1;
}

sub responseType {
    my $self = shift;
    my $part = shift;

    $self->extractParts();
    return $self->{RESPONSE_TYPE}->{$part};
}

sub responseIds {
    my $self = shift;
    my $part = shift;

    $self->extractParts();
    return $self->{RESPONSE_IDS}->{$part};
}

# Private function: Extracts the parts information, both part names and
# part types, and saves it. 
sub extractParts { 
    my $self = shift;
    
    return if (defined($self->{PARTS}));
    return if ($self->ext);

    $self->{PARTS} = [];

    my %parts;

    # Retrieve part count, if this is a problem
    if ($self->is_problem()) {
        my $metadata = &Apache::lonnet::metadata($self->src(), 'packages');
        if (!$metadata) {
            $self->{RESOURCE_ERROR} = 1;
            $self->{PARTS} = [];
            $self->{PART_TYPE} = {};
            return;
        }
        foreach (split(/\,/,$metadata)) {
            if ($_ =~ /^part_(.*)$/) {
                my $part = $1;
                # This floods the logs if it blows up
                if (defined($parts{$part})) {
                    Apache::lonnet::logthis("$part multiply defined in metadata for " . $self->symb());
                  }

                # check to see if part is turned off.

                if (!Apache::loncommon::check_if_partid_hidden($part, $self->symb())) {
                    $parts{$part} = 1;
                }
            }
        }
        
        
        my @sortedParts = sort keys %parts;
        $self->{PARTS} = \@sortedParts;

        my %responseIdHash;
        my %responseTypeHash;


        # Init the responseIdHash
        foreach (@{$self->{PARTS}}) {
            $responseIdHash{$_} = [];
        }

        # Now, the unfortunate thing about this is that parts, part name, and
        # response if are delimited by underscores, but both the part
        # name and response id can themselves have underscores in them.
        # So we have to use our knowlege of part names to figure out 
        # where the part names begin and end, and even then, it is possible
        # to construct ambiguous situations.
        foreach (split /,/, $metadata) {
            if ($_ =~ /^([a-zA-Z]+)response_(.*)/) {
                my $responseType = $1;
                my $partStuff = $2;
                my $partIdSoFar = '';
                my @partChunks = split /_/, $partStuff;
                my $i = 0;

                for ($i = 0; $i < scalar(@partChunks); $i++) {
                    if ($partIdSoFar) { $partIdSoFar .= '_'; }
                    $partIdSoFar .= $partChunks[$i];
                    if ($parts{$partIdSoFar}) {
                        my @otherChunks = @partChunks[$i+1..$#partChunks];
                        my $responseId = join('_', @otherChunks);
                        push @{$responseIdHash{$partIdSoFar}}, $responseId;
                        $responseTypeHash{$partIdSoFar} = $responseType;
                        last;
                    }
                }
            }
        }

        $self->{RESPONSE_IDS} = \%responseIdHash;
        $self->{RESPONSE_TYPES} = \%responseTypeHash;
    }

    return;
}

=pod

=head2 Resource Status

Problem resources have status information, reflecting their various
dates and completion statuses.

There are two aspects to the status: the date-related information and
the completion information.

Idiomatic usage of these two methods would probably look something
like

 foreach ($resource->parts()) {
    my $dateStatus = $resource->getDateStatus($_);
    my $completionStatus = $resource->getCompletionStatus($_);

    or

    my $status = $resource->status($_);

    ... use it here ...
 }

Which you use depends on exactly what you are looking for. The
status() function has been optimized for the nav maps display and may
not precisely match what you need elsewhere.

The symbolic constants shown below can be accessed through the
resource object: C<$res->OPEN>.

=over 4

=item * B<getDateStatus>($part):

($part defaults to 0). A convenience function that returns a symbolic
constant telling you about the date status of the part. The possible
return values are:

=back

B<Date Codes>

=over 4

=item * B<OPEN_LATER>:

The problem will be opened later.

=item * B<OPEN>:

Open and not yet due.


=item * B<PAST_DUE_ANSWER_LATER>:

The due date has passed, but the answer date has not yet arrived.

=item * B<PAST_DUE_NO_ANSWER>:

The due date has passed and there is no answer opening date set.

=item * B<ANSWER_OPEN>:

The answer date is here.

=item * B<NETWORK_FAILURE>:

The information is unknown due to network failure.

=back

=cut

# Apparently the compiler optimizes these into constants automatically
sub OPEN_LATER             { return 0; }
sub OPEN                   { return 1; }
sub PAST_DUE_NO_ANSWER     { return 2; }
sub PAST_DUE_ANSWER_LATER  { return 3; }
sub ANSWER_OPEN            { return 4; }
sub NOTHING_SET            { return 5; } 
sub NETWORK_FAILURE        { return 100; }

# getDateStatus gets the date status for a given problem part. 
# Because answer date, due date, and open date are fully independent
# (i.e., it is perfectly possible to *only* have an answer date), 
# we have to completely cover the 3x3 maxtrix of (answer, due, open) x
# (past, future, none given). This function handles this with a decision
# tree. Read the comments to follow the decision tree.

sub getDateStatus {
    my $self = shift;
    my $part = shift;
    $part = "0" if (!defined($part));

    # Always return network failure if there was one.
    return $self->NETWORK_FAILURE if ($self->{NAV_MAP}->{NETWORK_FAILURE});

    my $now = time();

    my $open = $self->opendate($part);
    my $due = $self->duedate($part);
    my $answer = $self->answerdate($part);

    if (!$open && !$due && !$answer) {
        # no data on the problem at all
        # should this be the same as "open later"? think multipart.
        return $self->NOTHING_SET;
    }
    if (!$open || $now < $open) {return $self->OPEN_LATER}
    if (!$due || $now < $due) {return $self->OPEN}
    if ($answer && $now < $answer) {return $self->PAST_DUE_ANSWER_LATER}
    if ($answer) { return $self->ANSWER_OPEN; }
    return PAST_DUE_NO_ANSWER;
}

=pod

B<>

=over 4

=item * B<getCompletionStatus>($part):

($part defaults to 0.) A convenience function that returns a symbolic
constant telling you about the completion status of the part, with the
following possible results:

=back

B<Completion Codes>

=over 4

=item * B<NOT_ATTEMPTED>:

Has not been attempted at all.

=item * B<INCORRECT>:

Attempted, but wrong by student.

=item * B<INCORRECT_BY_OVERRIDE>:

Attempted, but wrong by instructor override.

=item * B<CORRECT>:

Correct or correct by instructor.

=item * B<CORRECT_BY_OVERRIDE>:

Correct by instructor override.

=item * B<EXCUSED>:

Excused. Not yet implemented.

=item * B<NETWORK_FAILURE>:

Information not available due to network failure.

=item * B<ATTEMPTED>:

Attempted, and not yet graded.

=back

=cut

sub NOT_ATTEMPTED         { return 10; }
sub INCORRECT             { return 11; }
sub INCORRECT_BY_OVERRIDE { return 12; }
sub CORRECT               { return 13; }
sub CORRECT_BY_OVERRIDE   { return 14; }
sub EXCUSED               { return 15; }
sub ATTEMPTED             { return 16; }

sub getCompletionStatus {
    my $self = shift;
    return $self->NETWORK_FAILURE if ($self->{NAV_MAP}->{NETWORK_FAILURE});

    my $status = $self->queryRestoreHash('solved', shift);

    # Left as seperate if statements in case we ever do more with this
    if ($status eq 'correct_by_student') {return $self->CORRECT;}
    if ($status eq 'correct_by_override') {return $self->CORRECT_BY_OVERRIDE; }
    if ($status eq 'incorrect_attempted') {return $self->INCORRECT; }
    if ($status eq 'incorrect_by_override') {return $self->INCORRECT_BY_OVERRIDE; }
    if ($status eq 'excused') {return $self->EXCUSED; }
    if ($status eq 'ungraded_attempted') {return $self->ATTEMPTED; }
    return $self->NOT_ATTEMPTED;
}

sub queryRestoreHash {
    my $self = shift;
    my $hashentry = shift;
    my $part = shift;
    $part = "0" if (!defined($part) || $part eq '');
    return $self->NETWORK_FAILURE if ($self->{NAV_MAP}->{NETWORK_FAILURE});

    $self->getReturnHash();

    return $self->{RETURN_HASH}->{'resource.'.$part.'.'.$hashentry};
}

=pod

B<Composite Status>

Along with directly returning the date or completion status, the
resource object includes a convenience function B<status>() that will
combine the two status tidbits into one composite status that can
represent the status of the resource as a whole. This method represents
the concept of the thing we want to display to the user on the nav maps
screen, which is a combination of completion and open status. The precise logic is
documented in the comments of the status method. The following results
may be returned, all available as methods on the resource object
($res->NETWORK_FAILURE): In addition to the return values that match
the date or completion status, this function can return "ANSWER_SUBMITTED"
if that problemstatus parameter value is set to No, suppressing the
incorrect/correct feedback.

=over 4

=item * B<NETWORK_FAILURE>:

The network has failed and the information is not available.

=item * B<NOTHING_SET>:

No dates have been set for this problem (part) at all. (Because only
certain parts of a multi-part problem may be assigned, this can not be
collapsed into "open later", as we do not know a given part will EVER
be opened. For single part, this is the same as "OPEN_LATER".)

=item * B<CORRECT>:

For any reason at all, the part is considered correct.

=item * B<EXCUSED>:

For any reason at all, the problem is excused.

=item * B<PAST_DUE_NO_ANSWER>:

The problem is past due, not considered correct, and no answer date is
set.

=item * B<PAST_DUE_ANSWER_LATER>:

The problem is past due, not considered correct, and an answer date in
the future is set.

=item * B<ANSWER_OPEN>:

The problem is past due, not correct, and the answer is now available.

=item * B<OPEN_LATER>:

The problem is not yet open.

=item * B<TRIES_LEFT>:

The problem is open, has been tried, is not correct, but there are
tries left.

=item * B<INCORRECT>:

The problem is open, and all tries have been used without getting the
correct answer.

=item * B<OPEN>:

The item is open and not yet tried.

=item * B<ATTEMPTED>:

The problem has been attempted.

=item * B<ANSWER_SUBMITTED>:

An answer has been submitted, but the student should not see it.

=back

=cut

sub TRIES_LEFT       { return 20; }
sub ANSWER_SUBMITTED { return 21; }

sub status {
    my $self = shift;
    my $part = shift;
    if (!defined($part)) { $part = "0"; }
    my $completionStatus = $self->getCompletionStatus($part);
    my $dateStatus = $self->getDateStatus($part);

    # What we have is a two-dimensional matrix with 4 entries on one
    # dimension and 5 entries on the other, which we want to colorize,
    # plus network failure and "no date data at all".

    if ($completionStatus == NETWORK_FAILURE) { return NETWORK_FAILURE; }

    my $suppressFeedback = lc($self->parmval("problemstatus", $part)) eq 'no';

    # There are a few whole rows we can dispose of:
    if ($completionStatus == CORRECT ||
        $completionStatus == CORRECT_BY_OVERRIDE ) {
        return $suppressFeedback? ANSWER_SUBMITTED : CORRECT; 
    }

    if ($completionStatus == ATTEMPTED) {
        return ATTEMPTED;
    }

    # If it's EXCUSED, then return that no matter what
    if ($completionStatus == EXCUSED) {
        return EXCUSED; 
    }

    if ($dateStatus == NOTHING_SET) {
        return NOTHING_SET;
    }

    # Now we're down to a 4 (incorrect, incorrect_override, not_attempted)
    # by 4 matrix (date statuses).

    if ($dateStatus == PAST_DUE_ANSWER_LATER ||
        $dateStatus == PAST_DUE_NO_ANSWER ) {
        return $dateStatus; 
    }

    if ($dateStatus == ANSWER_OPEN) {
        return ANSWER_OPEN;
    }

    # Now: (incorrect, incorrect_override, not_attempted) x 
    # (open_later), (open)
    
    if ($dateStatus == OPEN_LATER) {
        return OPEN_LATER;
    }

    # If it's WRONG...
    if ($completionStatus == INCORRECT || $completionStatus == INCORRECT_BY_OVERRIDE) {
        # and there are TRIES LEFT:
        if ($self->tries($part) < $self->maxtries($part) || !$self->maxtries($part)) {
            return TRIES_LEFT;
        }
        return $suppressFeedback ? ANSWER_SUBMITTED : INCORRECT; # otherwise, return orange; student can't fix this
    }

    # Otherwise, it's untried and open
    return OPEN; 
}

=pod

B<Completable>

The completable method represents the concept of I<whether the student can
currently do the problem>. If the student can do the problem, which means
that it is open, there are tries left, and if the problem is manually graded
or the grade is suppressed via problemstatus, the student has not tried it
yet, then the method returns 1. Otherwise, it returns 0, to indicate that 
either the student has tried it and there is no feedback, or that for
some reason it is no longer completable (not open yet, successfully completed,
out of tries, etc.). As an example, this is used as the filter for the
"Uncompleted Homework" option for the nav maps.

If this does not quite meet your needs, do not fiddle with it (unless you are
fixing it to better match the student's conception of "completable" because
it's broken somehow)... make a new method.

=cut

sub completable {
    my $self = shift;
    if (!$self->is_problem()) { return 0; }
    my $partCount = $self->countParts();

    foreach my $part (@{$self->parts()}) {
        if ($part eq '0' && $partCount != 1) { next; }
        my $status = $self->status($part);
        # "If any of the parts are open, or have tries left (implies open),
        # and it is not "attempted" (manually graded problem), it is
        # not "complete"
        if (!(($status == OPEN() || $status == TRIES_LEFT()) 
              && $self->getCompletionStatus($part) != ATTEMPTED()
              && $status != ANSWER_SUBMITTED())) {
            return 0;
        }
    }
        
    # If all the parts were complete, so was this problem.
    return 1;
}

=pod

=head2 Resource/Nav Map Navigation

=over 4

=item * B<getNext>():

Retreive an array of the possible next resources after this
one. Always returns an array, even in the one- or zero-element case.

=item * B<getPrevious>():

Retreive an array of the possible previous resources from this
one. Always returns an array, even in the one- or zero-element case.

=cut

sub getNext {
    my $self = shift;
    my @branches;
    my $to = $self->to();
    foreach my $branch ( split(/,/, $to) ) {
        my $choice = $self->{NAV_MAP}->getById($branch);
        my $next = $choice->goesto();
        $next = $self->{NAV_MAP}->getById($next);

        push @branches, $next;
    }
    return \@branches;
}

sub getPrevious {
    my $self = shift;
    my @branches;
    my $from = $self->from();
    foreach my $branch ( split /,/, $from) {
        my $choice = $self->{NAV_MAP}->getById($branch);
        my $prev = $choice->comesfrom();
        $prev = $self->{NAV_MAP}->getById($prev);

        push @branches, $prev;
    }
    return \@branches;
}

sub browsePriv {
    my $self = shift;
    if (defined($self->{BROWSE_PRIV})) {
        return $self->{BROWSE_PRIV};
    }

    $self->{BROWSE_PRIV} = &Apache::lonnet::allowed('bre', $self->src());
}

=pod

=back

=cut

1;

__END__