# The LearningOnline Network with CAPA
# Navigate Maps Handler
#
# $Id: lonnavmaps.pm,v 1.102 2002/11/12 18:24:38 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
#

package Apache::lonnavmaps;

use strict;
use Apache::Constants qw(:common :http);
use Apache::lonnet();
use Apache::loncommon();
use GDBM_File;
use POSIX qw (floor strftime);

sub handler {
    my $r = shift;

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

    # 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 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;
    }

    # Header
    $r->print(&Apache::loncommon::bodytag('Navigate Course Map','',
                                          ''));
    $r->print('<script>window.focus();</script>');

    $r->print('<table border="0" cellpadding="2" cellspacing="0">');
    my $date=localtime;
    $r->print('<tr><td align="right" valign="bottom">Key:&nbsp;&nbsp;</td>');

    # Print discussions and feedback header
    if ($navmap->{LAST_CHECK}) {
        $r->print('<td align="center" valign="bottom">&nbsp;&nbsp;'.
                  '<img src="/adm/lonMisc/chat.gif"> New discussion since '.
                  strftime("%A, %b %e at %I:%M %P", localtime($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 {
        $r->print('<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>'); 
    }
    $r->print('</tr></table>');

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

    if ($condition) {
        $r->print('<a href="navmaps?condition=0&filter=">Close All Folders</a>');
    } else {
        $r->print('<a href="navmaps?condition=1&filter=">Open All Folders</a>');
    }

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

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

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

    # Grab a resource object so we have access to the constants; this
    # is technically not proper, but should be harmless
    my $res = $navmap->firstResource();

    # These are some data tables, which make it easy to change some of
    # of the specific visualization parameters if desired.

    # Defines a status->color mapping, null string means don't color
    my %colormap = 
    ( $res->NETWORK_FAILURE        => '',
      $res->CORRECT                => '',
      $res->EXCUSED                => '#BBBBFF',
      $res->PAST_DUE_ANSWER_LATER  => '',
      $res->PAST_DUE_NO_ANSWER     => '',
      $res->ANSWER_OPEN            => '#CCFFCC',
      $res->OPEN_LATER             => '',
      $res->TRIES_LEFT             => '',
      $res->INCORRECT              => '',
      $res->OPEN                   => '',
      $res->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";

    my %statusIconMap = 
        ( $res->NETWORK_FAILURE    => '',
          $res->NOTHING_SET        => '',
          $res->CORRECT            => 'navmap.correct.gif',
          $res->EXCUSED            => 'navmap.correct.gif',
          $res->PAST_DUE_NO_ANSWER => 'navmap.wrong.gif',
          $res->PAST_DUE_ANSWER_LATER => 'navmap.wrong.gif',
          $res->ANSWER_OPEN        => 'navmap.wrong.gif',
          $res->OPEN_LATER         => '',
          $res->TRIES_LEFT         => 'navmap.open.gif',
          $res->INCORRECT          => 'navmap.wrong.gif',
          $res->OPEN               => 'navmap.open.gif',
          $res->ATTEMPTED          => 'navmap.open.gif' );

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

    my %condenseStatuses =
        ( $res->NETWORK_FAILURE    => 1,
          $res->NOTHING_SET        => 1,
          $res->CORRECT            => 1 );

    my %filterHash;
    # Figure out what we're not displaying
    foreach (split(/\,/, $ENV{"form.filter"})) {
        if ($_) {
            $filterHash{$_} = "1";
        }
    }

    # Is this a new-style course? If so, we want to suppress showing the top-level
    # maps in their own folders, in favor of "inlining" them.
    my $topResource = $navmap->getById("0.0");
    my $inlineTopLevelMaps = $topResource->src() =~ m|^/uploaded/.*default\.sequence$|;

    my $currenturl = $ENV{'form.postdata'};
    $currenturl=~s/^http\:\/\///;
    $currenturl=~s/^[^\/]+//;

    # alreadyHere allows us to only open the maps necessary to view
    # the current location once, while at the same time remembering
    # the current location. Without that check, the user would never
    # be able to close those maps; the user would close it, and the
    # currenturl scan would re-open it.
    my $queryAdd = "postdata=" . &Apache::lonnet::escape($currenturl) .
        "&alreadyHere=1";

    # Begin the HTML table
    # four cols: resource + indent, chat+feedback, icon, text string
    $r->print('<table cellspacing="0" cellpadding="3" border="0" bgcolor="#FFFFFF">' ."\n");

    # This needs to be updated to use symbs from the remote, 
    # instead of uris. The changes to this and the main rendering
    # loop should be obvious.
    # Here's a simple example of the iterator.
    # Preprocess the map: Look for current URL, force inlined maps to display

    my $mapIterator = $navmap->getIterator(undef, undef, \%filterHash, 1);
    my $found = 0;
    my $depth = 1;
    my $currentUrlIndex = 0; # 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 $currentUrlDelta = 5; # change this to change how many resources are displayed
                             # before the current resource when using #current
    $mapIterator->next(); # discard the first BEGIN_MAP
    my $curRes = $mapIterator->next();
    my $counter = 0;
    
    while ($depth > 0) {
        if ($curRes == $mapIterator->BEGIN_MAP()) { $depth++; }
        if ($curRes == $mapIterator->END_MAP()) { $depth--; }

        if (ref($curRes)) { $counter++; }

        my $mapStack = $mapIterator->getStack();
        if ($currenturl && !$ENV{'form.alreadyHere'} && ref($curRes) && 
            $curRes->src() eq $currenturl) {
            # If this is the correct resource, be sure to 
            # show it by making sure the containing maps
            # are open.

            # 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.
            $currentUrlIndex = $counter;
            
            # Ensure the parent maps are open
            for my $map (@{$mapStack}) {
                if ($condition) {
                    undef $filterHash{$map->map_pc()};
                } else {
                    $filterHash{$map->map_pc()} = 1;
                }
            }
            $ENV{'form.alreadyHere'} = 1;
        }
            
        # Preprocessing: If we're inlining nav maps into the top-level display,
        # make sure we show this map!
        if ($inlineTopLevelMaps && ref($curRes) && $curRes->is_map && 
            scalar(@{$mapStack}) == 1) {
            if ($condition) {
                undef $filterHash{$curRes->map_pc()};
            } else {
                $filterHash{$curRes->map_pc()} = 1;
            }
        }

        $curRes = $mapIterator->next();
    }
    
    undef $res; # so we don't accidentally use it later
    my $indentLevel = 0;
    my $indentString = "<img src=\"/adm/lonIcons/whitespace1.gif\" width=\"25\" height=\"1\" alt=\"\" border=\"0\" />";

    my $isNewBranch = 0;
    my $now = time();
    my $in24Hours = $now + 24 * 60 * 60;
    my $displayedHereMarker = 0;
    
    # We know the first thing is a BEGIN_MAP (see "$self->{STARTED}"
    # code in iterator->next), so ignore the first one
    $mapIterator = $navmap->getIterator(undef, undef, \%filterHash,
                                           $condition);
    $mapIterator->next();
    $curRes = $mapIterator->next();
    my $deltadepth = 0;
    $depth = 1;

    my @backgroundColors = ("#FFFFFF", "#F6F6F6");
    my $rowNum = 0;

    $counter = 0;

    # Print the 'current' anchor here if it would fall off the top
    if ($currentUrlIndex - $currentUrlDelta < 0) {
        $r->print('<a name="current" />');
    }

    while ($depth > 0) {
        # If this is an inlined map, cancel the shift to the right,
        # which has the effect of making the map look inlined
        if ($inlineTopLevelMaps && scalar(@{$mapIterator->getStack()}) == 1 &&
            ref($curRes) && $curRes->is_map()) {
            $deltadepth = -1;
            $curRes = $mapIterator->next();
            next;
        }

        if ($curRes == $mapIterator->BEGIN_MAP() ||
            $curRes == $mapIterator->BEGIN_BRANCH()) {
            $indentLevel++;
        }
        if ($curRes == $mapIterator->END_MAP() ||
            $curRes == $mapIterator->END_BRANCH()) {
            $indentLevel--;
        }
        if ($curRes == $mapIterator->BEGIN_BRANCH()) {
            $isNewBranch = 1;
        }
        if ($curRes == $mapIterator->BEGIN_MAP()) { $depth++; }
        if ($curRes == $mapIterator->END_MAP()) { $depth--; }

        if (ref($curRes)) { $counter++; }

        if ($depth == 1) { $deltadepth = 0; } # we're done shifting, because we're
                                              # out of the inlined map

        # Is this resource being ignored because it is in a random-out
        # map and it was not selected?
        if (ref($curRes) && !advancedUser() && $curRes->randomout()) {
            $curRes = $mapIterator->next();
            next; # if yes, then just ignore this resource
        }

        if (ref($curRes) && $curRes->src()) {

            # Step one: Decide which parts to show
            my @parts = @{$curRes->parts()};
            my $multipart = scalar(@parts) > 1;
            my $condensed = 0;
                
            if ($curRes->is_problem()) {

                # Is it multipart?
                if ($multipart) {
                    # If it's multipart, see if part 0 is "open"
                    # if it is, display all parts, if it isn't,
                    # just display first
                    if (!$curRes->opendate("0")) {
                        # no parts are open, display as one part
                        @parts = ("0");
                        $condensed = 1;
                    } else {
                        # Otherwise, only display part 0 if we want to 
                        # attach feedback or email information to it
                        if ($curRes->hasDiscussion() || $curRes->getFeedback()) {
                            shift @parts;
                        } else {
                            # Now, we decide whether to condense the
                            # parts due to similarity
                            my $status = $curRes->status($parts[1]);
                            my $due = $curRes->duedate($parts[1]);
                            my $open = $curRes->opendate($parts[1]);
                            my $statusAllSame = 1;
                            my $dueAllSame = 1;
                            my $openAllSame = 1;
                            for (my $i = 2; $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[1]);
                                $condensed = 1;
                            }
                        }
                    }
                }

            } else {
                $parts[0] = "0"; # this is to get past foreach loop below
                 # you can consider a non-problem resource as a resource
                  # with only one part without loss, and it simplifies the looping
            }

            # Is it a multipart problem with a single part, now in 
            # @parts with "0" filtered out? If so, 'forget' it's a multi-part
            # problem and treat it like a single-part problem.
            if ( scalar(@parts) == 1 ) {
                $multipart = 0;
            }

            # Display one part, in event of network error.
            # If this is a single part, we can at least show the correct
            # status, but if it's multipart, we're lost, since we can't
            # retreive the metadata to count the parts
            if ($curRes->{RESOURCE_ERROR}) {
                @parts = ("0");
            }

            # Step Two: Print the actual data.

            # For each part we intend to display...
            foreach my $part (@parts) {

                my $deltalevel = 0; # for inserting the branch icon
                my $nonLinkedText = ""; # unlinked stuff after title
                
                my $stack = $mapIterator->getStack();
                my $src = getLinkForResource($stack);

                # Pass the correct symb on the querystring, so the
                # remote will figure out where we are if we click a link
                my $srcHasQuestion = $src =~ /\?/;
                my $link = $src.
                    ($srcHasQuestion?'&':'?') .
                    'symb='.&Apache::lonnet::escape($curRes->symb()).
                    '"';

                my $title = $curRes->title();
                if (!$title) {
                    $title = $curRes->src();
                    $title = substr ($title, rindex($title, "/") + 1);
                }
                my $partLabel = "";
                my $newBranchText = "";

                # If this is a new branch, label it so
                if ($isNewBranch) {
                    $newBranchText = "<img src=\"/adm/lonIcons/branch.gif\" border=\"0\">";
                    $isNewBranch = 0;
                    $deltalevel = 1; # reserves space for the branch icon
                }

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

                my $icon = "<img src=\"/adm/lonIcons/html.gif\" alt=\"\" border=\"0\" />";
                if ($curRes->is_problem()) { 
                    if ($part eq "0" || $condensed) {
                        $icon = '<img src="/adm/lonIcons/problem.gif" alt="" border=\"0\" />'; 
                    } else {
                        $icon = $indentString;
                    }
                }

                # Display the correct icon, link to open or shut map
                if ($curRes->is_map()) { 
                    my $mapId = $curRes->map_pc();
                    my $nowOpen = (!defined($filterHash{$mapId}));
                    if ($condition) {$nowOpen = !$nowOpen;}
                    $icon = $nowOpen ?
                        "navmap.folder.closed.gif" : "navmap.folder.open.gif";
                    $icon = "<img src=\"/adm/lonIcons/$icon\" alt=\"\" border=\"0\" />";
                    $linkopen = "<a href=\"/adm/navmaps?filter=";
                    $linkopen .= ($nowOpen xor $condition) ? 
                        addToFilter(\%filterHash, $mapId) :
                        removeFromFilter(\%filterHash, $mapId);
                    $linkopen .= "&condition=$condition&$queryAdd\">";
                    $linkclose = "</a>";

                }
                
                my $colorizer = "";
                my $color;
                if ($curRes->is_problem()) {
                    my $status = $curRes->status($part);
                    $color = $colormap{$status};

                    # Special case in the navmaps: If in less then
                    # 24 hours, give it a bit of urgency
                    if (($status == $curRes->OPEN() || $status == $curRes->ATTEMPTED() ||
                         $status == $curRes->TRIES_LEFT())
                        && $curRes->duedate() &&
                        $curRes->duedate() < time()+(24*60*60) && 
                        $curRes->duedate() > time()) {
                        $color = $hurryUpColor;
                    }
                    # Special case: If this is the last try, and there is
                    # more then one available, and it's not due yet, give a bit of urgency
                    my $tries = $curRes->tries($part);
                    my $maxtries = $curRes->maxtries($part);
                    if ($tries && $maxtries && $maxtries > 1 &&
                        $maxtries - $tries == 1 && $curRes->duedate() &&
                        $curRes->duedate() > time()) {
                        $color = $hurryUpColor;
                    }
                    if ($color ne "") {
                        $colorizer = "bgcolor=\"$color\"";
                    }
                }

                if ($curRes->randomout()) {
                    $nonLinkedText .= ' <i>(hidden)</i> ';
                }

                $rowNum++;
                my $backgroundColor = $backgroundColors[$rowNum % scalar(@backgroundColors)];

                # FIRST COL: The resource indentation, branch icon, name, and anchor
                $r->print("  <tr bgcolor=\"$backgroundColor\"><td align=\"left\" valign=\"center\" width=\"60%\">\n");

                # Print the anchor if necessary
                if ($counter == $currentUrlIndex - $currentUrlDelta) {
                    $r->print('<a name="current" />');
                }

                # print indentation
                for (my $i = 0; $i < $indentLevel - $deltalevel + $deltadepth; $i++) {
                    $r->print($indentString);
                }

                $r->print("  ${newBranchText}${linkopen}$icon${linkclose}\n");

                my $curMarkerBegin = "";
                my $curMarkerEnd = "";

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

                if ($curRes->is_problem() && $part ne "0" && !$condensed) { 
                    $partLabel = " (Part $part)"; 
                    $title = "";
                }
                if ($multipart && $condensed) {
                    $nonLinkedText .= ' (' . $curRes->countParts() . ' parts)';
                }

                $r->print("  $curMarkerBegin<a href=\"$link\">$title$partLabel</a> $curMarkerEnd $nonLinkedText");

                if ($curRes->{RESOURCE_ERROR}) {
                    $r->print(&Apache::loncommon::help_open_topic ("Navmap_Host_Down",
                                              '<font size="-1">Host down</font>'));
                    }

                # SECOND COL: Is there text, feedback, errors??
                my $discussionHTML = ""; my $feedbackHTML = "";

                if ($curRes->hasDiscussion()) {
                    $discussionHTML = $linkopen .
                        '<img border="0" src="/adm/lonMisc/chat.gif" />' .
                        $linkclose;
                }

                if ($curRes->getFeedback()) {
                    my $feedback = $curRes->getFeedback();
                    foreach (split(/\,/, $feedback)) {
                        if ($_) {
                            $feedbackHTML .= '&nbsp;<a href="/adm/email?display='
                                . &Apache::lonnet::escape($_) . '">'
                                . '<img src="/adm/lonMisc/feedback.gif" '
                                . 'border="0" /></a>';
                        }
                    }
                }

                $r->print("<td width=\"75\" align=\"left\" valign=\"center\">$discussionHTML$feedbackHTML&nbsp;</td>");

                # Is this the first displayed part of a multi-part problem
                # that has not been condensed, so we should suppress these two
                # columns so we don't display useless status info about part
                # "0"?
                my $firstDisplayed = !$condensed && $multipart && $part eq "0";

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

                # FOURTH COL: Text description
                $r->print("<td align=\"right\" valign=\"center\">\n");
                
                if ($curRes->kind() eq "res" &&
                    $curRes->is_problem() &&
                    !$firstDisplayed) {
                    $r->print ("<font color=\"$color\"><b>") if ($color);
                    $r->print (getDescription($curRes, $part));
                    $r->print ("</b></font>") if ($color);
                }
                if ($curRes->is_map() && advancedUser() && $curRes->randompick()) {
                    $r->print('(randomly select ' . $curRes->randompick() .')');
                }

                $r->print("&nbsp;</td></tr>\n");
            }
        }
        $curRes = $mapIterator->next();
    }

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

    $navmap->untieHashes();

    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 == $res->NETWORK_FAILURE) { return ""; }
    if ($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";
        }
    }
}

# This puts a human-readable name on the ENV variable.
sub advancedUser {
    return $ENV{'user.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;
    }
}

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, and also provides the Apache handler for the "Navigation Map" button.

=head1 navmap object: 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;
    if (!(tie(%navmaphash, 'GDBM_File', $self->{NAV_HASH_FILE},
              &GDBM_READER(), 0640))) {
        return undef;
    }
    $self->{NAV_HASH} = \%navmaphash;
    
    my %parmhash;
    if (!(tie(%parmhash, 'GDBM_File', $self->{PARM_HASH_FILE},
              &GDBM_READER(), 0640)))
    {
        untie $self->{PARM_HASH};
        return undef;
    }
    $self->{PARM_HASH} = \%parmhash;
    $self->{HASH_TIED} = 1;

    bless($self);
        
    return $self;
}

sub init {
    my $self = shift;

    # 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);
                if ($reply!~/^error\:/) {
                    $courserdatas{$cid}=$reply;
                    $courserdatas{$cid.'.last_cache'}=time;
                }
                # check to see if network failed
                elsif ( $reply=~/no.such.host/i || $reply=~/con.*lost/i )
                {
                    $self->{NETWORK_FAILURE} = 1;
                }
            }
            foreach (split(/\&/,$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} = {};
}

# 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 = $self->{NAV_HASH}->{"map_start_$uri"};
    my $lastres = $self->{NAV_HASH}->{"map_finish_$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}} if ($self->{HASH_TIED});
    untie %{$self->{PARM_HASH}} if ($self->{HASH_TIED});
    $self->{HASH_TIED} = 0;
}

# when the object is destroyed, be sure to untie all the hashes we tied.
sub DESTROY {
    my $self = shift;
    $self->untieHashes();
}

# Private function: 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 $self->{DISCUSSION_TIME}->{$symb} >
           $self->{LAST_CHECK};
}

# Private function: 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};
}

=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.

=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.
    return Apache::lonnavmaps::resource->new($self, $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 = $self->{NAV_HASH}->{'map_start_' .
                     &Apache::lonnet::clutter($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 = $self->{NAV_HASH}->{'map_finish_' .
                     &Apache::lonnet::clutter($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 ($part,$id)=split(/\_/,$space);
        if ($id) {
            my $partgeneral=$self->parmval($part.".$qualifier",$symb);
            if (defined($partgeneral)) { return $partgeneral; }
        } else {
            my $resourcegeneral=$self->parmval("0.$qualifier",$symb);
            if (defined($resourcegeneral)) { return $resourcegeneral; }
        }
    }
    return '';
}


1;

package Apache::lonnavmaps::iterator;

=pod

=back

=head1 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): 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.

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.

=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; }
}

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;

    # 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

    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)) {
                my $resultingVal = $curRes->{DATA}->{$valName};
                my $nextResources = $curRes->$nextResourceMethod();
                my $resourceCount = scalar(@{$nextResources});
            
                if ($resourceCount == 1) {
                    my $current = $nextResources->[0]->{DATA}->{$valName} || 999999999;
                    $nextResources->[0]->{DATA}->{$valName} = min($resultingVal, $current);
                }
                
                if ($resourceCount > 1) {
                    foreach my $res (@{$nextResources}) {
                        my $current = $res->{DATA}->{$valName} || 999999999;
                        $res->{DATA}->{$valName} = min($current, $resultingVal + 1);
                    }
                }
            }
            
            # Assign the final val
            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;}
                }
            $curRes = $iterator->next();
        }
    }

    # 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
    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 ($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 ) {
            $here = $self->{HERE} = shift @{$self->{STACK}->[$i]};
            $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();
        }
    }

    # 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();

    for (@$nextUnfiltered) {
        if (!defined($self->{ALREADY_SEEN}->{$_->{ID}})) {
            push @{$self->{STACK}->[$_->{DATA}->{DISPLAY_DEPTH}]}, $_;
            $self->{ALREADY_SEEN}->{$_->{ID}} = 1;
        }
    }
    
    # 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});
    }

    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

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};
}

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::lonnavmap::navmap, and use the "start" method to obtain the starting resource.

=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 $self->{NAV_MAP}->{NAV_HASH}->{$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<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); }

=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_problem>: Returns true if the resource is a problem.

=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 || "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();
    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();
    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 won't 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 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 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 $part = shift;
    $part = '0' if (!defined($part));

    # Make sure return hash is loaded, should error check
    $self->getReturnHash();
    
    my $tries = $self->{RETURN_HASH}->{'resource.'.$part.'.tries'};
    if (!defined($tries)) {return '0';}
    return $tries;
}
sub type {
    (my $self, my $part) = @_;
    return $self->parmval("type", $part);
}
sub weight {
    (my $self, my $part) = @_;
    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;
    return $self->{NAV_MAP}->getFeedback($self->src());
}

=pod

=item * B<parts>(): Returns a list reference containing sorted strings corresponding to each part of the problem. To count the number of parts, use the list in a scalar context, and subtract one if greater then two. (One part problems have a part 0. Multi-parts have a part 0, plus a part for each part. Filtering part 0 if you want it is up to you.)

=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. Thus, B<parts> may return an array with fewer parts in it then countParts might lead you to believe.

=back

=cut

sub parts {
    my $self = shift;

    if ($self->ext) { return ['0']; }

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

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

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

    if (scalar(@{$parts}) < 2) { return 1;}

    return scalar(@{$parts}) - 1;
}

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

    $self->{PARTS} = [];

    # Retrieve part count, if this is a problem
    if ($self->is_problem()) {
        my $metadata = &Apache::lonnet::metadata($self->src(), 'allpossiblekeys');
        if (!$metadata) {
            $self->{RESOURCE_ERROR} = 1;
            $self->{PARTS} = [];
            return;
        }
        
        foreach (split(/\,/,$metadata)) {
            if ($_ =~ /^parameter\_(.*)\_opendate$/) {
                push @{$self->{PARTS}}, $1;
            }
        }
        
        
        # Is this possible to do in one line? - Jeremy
        my @sortedParts = sort @{$self->{PARTS}};
        $self->{PARTS} = \@sortedParts;
    }

    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: $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;
    my $part = shift;
    $part = "0" if (!defined($part));
    return $self->NETWORK_FAILURE if ($self->{NAV_MAP}->{NETWORK_FAILURE});

    # Make sure return hash exists
    $self->getReturnHash();
    
    my $status = $self->{RETURN_HASH}->{'resource.'.$part.'.solved'};

    # 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;
}

=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. 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):

=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 don't 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.

=back

=cut

sub TRIES_LEFT { return 10; }

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; }

    # There are a few whole rows we can dispose of:
    if ($completionStatus == CORRECT ||
        $completionStatus == CORRECT_BY_OVERRIDE ) {
        return 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 INCORRECT; # otherwise, return orange; student can't fix this
    }

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

=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);

        # Don't remember it if the student doesn't have browse priviledges
        # future note: this may properly belong in the client of the resource
        my $browsePriv = &Apache::lonnet::allowed('bre', $self->src);
        if (!($browsePriv ne '2' && $browsePriv ne 'F')) {
            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);

        # Don't remember it if the student doesn't have browse priviledges
        # future note: this may properly belong in the client of the resource
        my $browsePriv = &Apache::lonnet::allowed('bre', $self->src);
        if ($browsePriv ne '2' && $browsePriv ne 'F') {
            push @branches, $prev;
        }
    }
    return \@branches;
}

=pod

=back

=cut

1;

__END__