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# The LearningOnline Network with CAPA
#
# Page flip handler
#
# $Id: lonpageflip.pm,v 1.79 2009/04/23 17:31:25 bisitz 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/
#



package Apache::lonpageflip;

use strict;
use LONCAPA;
use Apache::Constants qw(:common :http REDIRECT);
use Apache::lonnet;
use Apache::loncommon();
use HTML::TokeParser;
use GDBM_File;

# ========================================================== Module Global Hash
  
my %hash;

sub cleanup {
    if (tied(%hash)){
	&Apache::lonnet::logthis('Cleanup pageflip: hash');
        unless (untie(%hash)) {
	    &Apache::lonnet::logthis('Failed cleanup pageflip: hash');
        }
    }
    return OK;
}

sub addrid {
    my ($current,$new,$condid)=@_;
    unless ($condid) { $condid=0; }

	if ($current) {
	    $current.=','.$new;
        } else {
            $current=''.$new;
        }

    return $current;
}

sub fullmove {
    my ($rid,$mapurl,$direction)=@_;
    if (tie(%hash,'GDBM_File',$env{'request.course.fn'}.'.db',
                        &GDBM_READER(),0640)) {
	($rid,$mapurl)=&move($rid,$mapurl,$direction);
        untie(%hash);
    }
    return($rid,$mapurl);
}

sub hash_src {
    my ($id)=@_;
    my ($mapid,$resid)=split(/\./,$id);
    my $symb=&Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},
					  $resid,$hash{'src_'.$id});
    if ($hash{'encrypted_'.$id}) {
	return (&Apache::lonenc::encrypted($hash{'src_'.$id}),
		&Apache::lonenc::encrypted($symb));
    }
    return ($hash{'src_'.$id},$symb);
}

sub move {
    my ($next,$endupmap,$direction) = @_;
    my $safecount=0;
    my $allowed=0;
    do {
	($next,$endupmap)=&get_next_possible_move($next,$endupmap,$direction);

	my $url = $hash{'src_'.$next};
	my ($mapid,$resid)=split(/\./,$next);
	my $symb = &Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},
						$resid,$url);
	if ($url eq '' || $symb eq '') {
	    $allowed = 0;
	} else {
	    my $priv = &Apache::lonnet::allowed('bre',$url,$symb);
	    $allowed = (($priv eq 'F') || ($priv eq '2'));
	}
	$safecount++;
    } while (   ($next)
	     && ($next!~/\,/)
	     && (
		    (!$hash{'src_'.$next})
		 || (
		        (!$env{'request.role.adv'})
		     &&  $hash{'randomout_'.$next}
		    )
		 || (!$allowed)
		)
	     && ($safecount<10000));

    return ($next,$endupmap);
}

sub get_next_possible_move {
    my ($rid,$mapurl,$direction)=@_;
    my $startoutrid=$rid;

    my $next='';

              my $mincond=1;
              my $posnext='';
              if ($direction eq 'forward') {
# --------------------------------------------------------------------- Forward
                  while ($hash{'type_'.$rid} eq 'finish') {
	             $rid=$hash{'ids_'.$hash{'map_id_'.(split(/\./,$rid))[0]}};
                  }
		  foreach my $id (split(/\,/,$hash{'to_'.$rid})) {
		     my $condition= $hash{'conditions_'.$hash{'goesto_'.$id}};
		     my $rescond  = &Apache::lonnet::docondval($condition);
		     my $linkcond = &Apache::lonnet::directcondval($hash{'condid_'.$hash{'undercond_'.$id}});
		     my $thiscond = ($rescond<$linkcond)?$rescond:$linkcond;
		     if ($thiscond>=$mincond) {
		          if ($posnext) {
		             $posnext.=','.$id.':'.$thiscond;
                          } else {
                             $posnext=$id.':'.$thiscond;
		          }
                          if ($thiscond>$mincond) { $mincond=$thiscond; }
	              }
                  } 
		  foreach my $id (split(/\,/,$posnext))  {
                      my ($linkid,$condval)=split(/\:/,$id);
                      if ($condval>=$mincond) {
		          $next=&addrid($next,$hash{'goesto_'.$linkid},
                                $hash{'condid_'.$hash{'undercond_'.$linkid}});
                      }
                  }
                  if ($hash{'is_map_'.$next}) {
# This jumps to the beginning of a new map (going down level)
                      if (
      $hash{'map_type_'.$hash{'map_pc_'.$hash{'src_'.$next}}} eq 'sequence') {
			  $mapurl=$hash{'src_'.$next};
			  $next=$hash{'map_start_'.$hash{'src_'.$next}};
                     } elsif (
# This jumps back up from an empty sequence, to a page up one level
                         $hash{'map_type_'.$hash{'map_pc_'.$hash{'src_'.$next}}} eq 'page') {
                         $mapurl=$hash{'map_id_'.(split(/\./,$next))[0]};
                     }
                  } elsif 
                    ((split(/\./,$startoutrid))[0]!=(split(/\./,$next))[0]) {
# This comes up from a map (coming up one level);
		      $mapurl=$hash{'map_id_'.(split(/\./,$next))[0]};
		  }
              } elsif ($direction eq 'back') {
# ------------------------------------------------------------------- Backwards
                 while ($hash{'type_'.$rid} eq 'start') {
	             $rid=$hash{'ids_'.$hash{'map_id_'.(split(/\./,$rid))[0]}};
		 }
		 foreach my $id (split(/\,/,$hash{'from_'.$rid})) {
		     my $condition= $hash{'conditions_'.$hash{'comesfrom_'.$id}};
		     my $rescond  = &Apache::lonnet::docondval($condition);
		     my $linkcond = &Apache::lonnet::directcondval($hash{'condid_'.$hash{'undercond_'.$id}});
		     my $thiscond = ($rescond<$linkcond)?$rescond:$linkcond;
		     if ($thiscond>=$mincond) {
			 if ($posnext) {
		             $posnext.=','.$id.':'.$thiscond;
			 } else {
                             $posnext=$id.':'.$thiscond;
			 }
			 if ($thiscond>$mincond) { $mincond=$thiscond; }
		     }
		 } 
		 foreach my $id (split(/\,/,$posnext)) {
		     my ($linkid,$condval)=split(/\:/,$id);
		     if ($condval>=$mincond) {
			 $next=&addrid($next,$hash{'comesfrom_'.$linkid},
				       $hash{'condid_'.$hash{'undercond_'.$linkid}});
		     }
		 }
                  if ($hash{'is_map_'.$next}) {
# This jumps to the end of a new map (going down one level)
                      if (
      $hash{'map_type_'.$hash{'map_pc_'.$hash{'src_'.$next}}} eq 'sequence') {
			  $mapurl=$hash{'src_'.$next};
			  $next=$hash{'map_finish_'.$hash{'src_'.$next}};
                      } elsif (
      $hash{'map_type_'.$hash{'map_pc_'.$hash{'src_'.$next}}} eq 'page') {
# This jumps back up from an empty sequence, to a page up one level
                          $mapurl=$hash{'map_id_'.(split(/\./,$next))[0]};
                      }
                  } elsif 
                    ((split(/\./,$startoutrid))[0]!=(split(/\./,$next))[0]) {
# This comes back up from a map (going up one level);
		      $mapurl=$hash{'map_id_'.(split(/\./,$next))[0]};
                  }
	      }
              return ($next,$mapurl);
}

sub navlaunch {
    my ($r)=@_;
    &Apache::loncommon::content_type($r,'text/html');
    &Apache::loncommon::no_cache($r);
    $r->send_http_header;
    $r->print(&Apache::loncommon::start_page('Launched'));   
    $r->print(<<ENDNAV);
    <p><a href="/adm/flip?postdata=firstres%3a">Goto first resource</a></p>
    <script type="text/javascript">
	function collapse() {
	    menu=window.open("/adm/navmaps?collapseExternal","loncapanav",
			     "height=600,width=400,scrollbars=1");
	    this.document.location='/adm/navmaps?turningOffExternal';
	}
    </script>
    <p><a href="javascript:collapse();">Collapse external navigation window</a></p>
ENDNAV
    $r->print(&Apache::loncommon::end_page());
}

sub first_accessible_resource {
    my $furl;
    if (tie(%hash,'GDBM_File',$env{'request.course.fn'}.'.db',
	    &GDBM_READER(),0640)) {
	$furl=$hash{'first_url'};
	my %args;
	my ($url,$args) = split(/\?/,$furl);
	foreach my $pair (split(/\&/,$args)) {
	    my ($name,$value) = split(/=/,$pair);
	    $args{&unescape($name)} = &unescape($value);
	}
        if (!&Apache::lonnet::allowed('bre',$url,$args{'symb'})) {
# Wow, we cannot see this ... move forward to the next one that we can see
	    my ($newrid,$newmap)=&move($hash{'first_rid'},$hash{'first_mapurl'},'forward');
# Build the new URL
	    my ($newmapid,$newresid)=split(/\./,$newrid);
	    my $symb=&Apache::lonnet::encode_symb($newmap,$newresid,$hash{'src_'.$newrid});
	    $furl=&add_get_param($hash{'src_'.$newrid},{ 'symb' => $symb });
	    if ($hash{'encrypted_'.$newrid}) {
		$furl=&Apache::lonenc::encrypted($furl);
	    }
	}
	untie(%hash);
	return $furl;
    } else {
	return '/adm/navmaps';
    }
}

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

sub handler {
   my $r=shift;

# ------------------------------------------- Set document type for header only

  if ($r->header_only) {
      &Apache::loncommon::content_type($r,'text/html');
      $r->send_http_header;
      return OK;
  }

  my %cachehash=(); 
  my $multichoice=0;
  my %multichoicehash=();
  my ($redirecturl,$redirectsymb);
  my $next='';
  my @possibilities=();
   &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},['postdata']);
  if (($env{'form.postdata'})&&($env{'request.course.fn'})) {
      $env{'form.postdata'}=~/(\w+)\:(.*)/;
      my $direction=$1;
      my $currenturl=$2;
      if ($currenturl=~m|^/enc/|) {
	  $currenturl=&Apache::lonenc::unencrypted($currenturl);
      }
      $currenturl=~s/\.\d+\.(\w+)$/\.$1/;
      if ($direction eq 'firstres') {
	  my $furl=&first_accessible_resource();
	  &Apache::loncommon::content_type($r,'text/html');
	  $r->header_out(Location => 
			 &Apache::lonnet::absolute_url().$furl);
	     
	  return REDIRECT;
      }
      if ($direction eq 'return' || $direction eq 'navlaunch') {
# -------------------------------------------------------- Return to last known
         my $last;
         if (tie(%hash,'GDBM_File',$env{'request.course.fn'}.'_symb.db',
                    &GDBM_READER(),0640)) {
	     $last=$hash{'last_known'};
             untie(%hash);
         }
         my $newloc;
         if (($last) && (tie(%hash,'GDBM_File',$env{'request.course.fn'}.'.db',
                        &GDBM_READER(),0640))) {
            my ($murl,$id,$fn)=&Apache::lonnet::decode_symb($last);
	    $id=$hash{'map_pc_'.&Apache::lonnet::clutter($murl)}.'.'.$id;
	    $newloc=$hash{'src_'.$id};
	    if ($newloc) {
		if ($hash{'encrypted_'.$id}) { $newloc=&Apache::lonenc::encrypted($newloc); }
			      
	    } else {
		$newloc='/adm/navmaps';
	    }
            untie %hash;
         } else {
	    $newloc='/adm/navmaps';
         }  
	 if ($newloc eq '/adm/navmaps' && $direction eq 'navlaunch') {
	     &navlaunch($r);
	     return OK;
	 } else {
	     &Apache::loncommon::content_type($r,'text/html');
	     $r->header_out(Location => 
			    &Apache::lonnet::absolute_url().$newloc);
	     
	     return REDIRECT;
	 }
      }
      $currenturl=~s/^https?\:\/\///;
      $currenturl=~s/^[^\/]+//;
#
# Is the current URL on the map? If not, start with last known URL
#
      unless (&Apache::lonnet::is_on_map($currenturl)) {
	 my $last;
         if (tie(%hash,'GDBM_File',$env{'request.course.fn'}.'_symb.db',
                    &GDBM_READER(),0640)) {
	     $last=$hash{'last_known'};
             untie(%hash);
         }
         if ($last) {
	     $currenturl=&Apache::lonnet::clutter((&Apache::lonnet::decode_symb($last))[2]);
	 } else {
	     if ($direction eq 'return') {
		 &Apache::loncommon::content_type($r,'text/html');
		 $r->header_out(Location => 
				&Apache::lonnet::absolute_url().
				'/adm/noidea.html');
		 return REDIRECT;
	     } else {
		 &navlaunch($r);
		 return OK;
	     }
         }
      }
# ------------------------------------------- Do we have any idea where we are?
      my $position;
      if ($position=Apache::lonnet::symbread($currenturl)) {
# ------------------------------------------------------------------------- Yes
	  my ($startoutmap,$mapnum,$thisurl)=&Apache::lonnet::decode_symb($position);
          $cachehash{$startoutmap}{$thisurl}=[$thisurl,$mapnum];
          $cachehash{$startoutmap}{'last_known'}=
                             [&Apache::lonnet::declutter($currenturl),$mapnum];

# ============================================================ Tie the big hash
          if (tie(%hash,'GDBM_File',$env{'request.course.fn'}.'.db',
                        &GDBM_READER(),0640)) {
              my $rid=$hash{'map_pc_'.&Apache::lonnet::clutter($startoutmap)}.
                      '.'.$mapnum;

# ------------------------------------------------- Move forward, backward, etc
              my $endupmap;
              ($next,$endupmap)=&move($rid,$startoutmap,$direction);
# -------------------------------------- Do we have one and only one empty URL?
# We are now at at least one non-empty URL
# ----------------------------------------------------- Check out possibilities
              if ($next) {
                  @possibilities=split(/\,/,$next);
                  if ($#possibilities==0) {
# ---------------------------------------------- Only one possibility, redirect
	              ($redirecturl,$redirectsymb)=&hash_src($next);
                      $cachehash{$endupmap}{$redirecturl}=
			  [$redirecturl,(split(/\./,$next))[1]];
                  } else {
# ------------------------ There are multiple possibilities for a next resource
                      $multichoice=1;
		      foreach my $id (@possibilities) {
			  $multichoicehash{'src_'.$id}=$hash{'src_'.$id};
                          $multichoicehash{'title_'.$id}=$hash{'title_'.$id};
                          $multichoicehash{'type_'.$id}=$hash{'type_'.$id};
                          (my $first, my $second) = $id =~ /(\d+).(\d+)/;
                          my $symbSrc = Apache::lonnet::declutter($hash{'src_'.$id});
                          $multichoicehash{'symb_'.$id} = 
                              Apache::lonnet::declutter($hash{'map_id_'.$first}.'___'.
                                                        $second.'___'.$symbSrc);
                                                         
                          my ($choicemap,$choiceres)=split(/\./,$id);
			  my $map=&Apache::lonnet::declutter($hash{'src_'.$choicemap});
			  my $url=$multichoicehash{'src_'.$id};
                          $cachehash{$map}{$url}=[$url,$choiceres];
                      }
                  }
	      } else {
# -------------------------------------------------------------- No place to go
                  $multichoice=-1;
              }
# ----------------- The program must come past this point to untie the big hash
	      untie(%hash);
# --------------------------------------------------------- Store position info
              $cachehash{$startoutmap}{'last_direction'}=[$direction,'notasymb'];
              foreach my $thismap (keys %cachehash) {
		  my $mapnum=$cachehash{$thismap}->{'mapnum'};
		  delete($cachehash{$thismap}->{'mapnum'});
		  &Apache::lonnet::symblist($thismap,
					    %{$cachehash{$thismap}});
	      }
# ============================================== Do not return before this line
              if ($redirecturl) {
# ----------------------------------------------------- There is a URL to go to
		  if ($direction eq 'forward') {
                     &Apache::lonnet::linklog($currenturl,$redirecturl);
		  }
		  if ($direction eq 'back') {
                     &Apache::lonnet::linklog($redirecturl,$currenturl);
		  }
# ------------------------------------------------- Check for critical messages
		  if ((time-$env{'user.criticalcheck.time'})>300) {
                     my @what=&Apache::lonnet::dump
                                  ('critical',$env{'user.domain'},
                                              $env{'user.name'});
                     if ($what[0]) {
	                if (($what[0] ne 'con_lost') && 
                            ($what[0]!~/^error\:/)) {
	                   $redirecturl='/adm/email?critical=display';
			   $redirectsymb='';
                        }
                     }
                     &Apache::lonnet::appenv({'user.criticalcheck.time'=>time});
		  }

		  &Apache::loncommon::content_type($r,'text/html');
		  my $url=&Apache::lonnet::absolute_url().$redirecturl;
		  $url = &add_get_param($url, { 'symb' => $redirectsymb});
                  $r->header_out(Location => $url);
                  return REDIRECT;
	      } else {
# --------------------------------------------------------- There was a problem
                  &Apache::loncommon::content_type($r,'text/html');
                  $r->send_http_header;
		  my %lt=&Apache::lonlocal::texthash('title' => 'End of Sequence',
						     'explain' =>
						     'You have reached the end of the sequence of materials.',
						     'back' => 'Go Back',
						     'nav' => 'Navigate Course Content',
						     'wherenext' =>
						     'There are several possibilities of where to go next',
						     'pick' =>
						     'Please click on the the resource you intend to access',
						     'titleheader' => 'Title',
						     'type' => 'Type');
                  if ($#possibilities>0) {
		      my $start_page=
			  &Apache::loncommon::start_page('Multiple Resources');
                     $r->print(<<ENDSTART);
$start_page
<h3>$lt{'wherenext'}</h3>
<p>
$lt{'pick'}:
<p>
<table border="2">
<tr><th>$lt{'titleheader'}</th><th>$lt{'type'}</th></tr>
ENDSTART
                     foreach my $id (@possibilities) {
                        $r->print(
                              '<tr><td><a href="'.
				  &add_get_param($multichoicehash{'src_'.$id},
						 {'symb' =>
						      $multichoicehash{'symb_'.$id},
						  }).'">'.
                              $multichoicehash{'title_'.$id}.
                              '</a></td><td>'.$multichoicehash{'type_'.$id}.
			      '</td></tr>');
                     }
                     $r->print('</table>');
                  } else {
		      my $start_page=
			  &Apache::loncommon::start_page('No Resource');
		      $r->print(<<ENDNONE);
$start_page
<h3>$lt{'title'}</h3>
<p>$lt{'explain'}</p>
ENDNONE
		  }
		  $r->print(<<ENDMENU);
<ul>
<li><a href="/adm/flip?postdata=return:">$lt{'back'}</a></li>
<li><a href="/adm/navmaps">$lt{'nav'}</a></li>
</ul>
ENDMENU
                  $r->print(&Apache::loncommon::end_page());
                  return OK;
	      }
	  } else {
# ------------------------------------------------- Problem, could not tie hash
              $env{'user.error.msg'}="/adm/flip:bre:0:1:Course Data Missing";
              return HTTP_NOT_ACCEPTABLE; 
          }
      } else {
# ---------------------------------------- No, could not determine where we are
	  $r->internal_redirect('/adm/ambiguous');
      }
  } else {
# -------------------------- Class was not initialized or page fliped strangely
      $env{'user.error.msg'}="/adm/flip:bre:0:0:Choose Course";
      return HTTP_NOT_ACCEPTABLE; 
  } 
}

1;
__END__

=pod

=head1 NAME

Apache::lonpageflip

=head1 SYNOPSIS

Deals with forward, backward, and other page flips.

This is part of the LearningOnline Network with CAPA project
described at http://www.lon-capa.org.

=head1 OVERVIEW

(empty)

=head1 SUBROUTINES

=over cleanup()

=item addrid()

=item fullmove()

=item hash_src()

=item move()

=item get_next_possible_move()

=item navlaunch()

=item first_accessible_resource()

=item handler()

=back

=cut