--- rat/lonuserstate.pm	2005/01/19 20:18:44	1.78.2.1
+++ rat/lonuserstate.pm	2011/07/26 10:40:23	1.138
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Construct and maintain state and binary representation of course for user
 #
-# $Id: lonuserstate.pm,v 1.78.2.1 2005/01/19 20:18:44 albertel Exp $
+# $Id: lonuserstate.pm,v 1.138 2011/07/26 10:40:23 foxr Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -31,10 +31,9 @@ package Apache::lonuserstate;
 
 # ------------------------------------------------- modules used by this module
 use strict;
-use Apache::Constants qw(:common :http);
-use Apache::File;
 use HTML::TokeParser;
-use Apache::lonnet();
+use Apache::lonnet;
+use Apache::lonlocal;
 use Apache::loncommon();
 use GDBM_File;
 use Apache::lonmsg;
@@ -42,22 +41,35 @@ use Safe;
 use Safe::Hole;
 use Opcode;
 use Apache::lonenc;
+use Fcntl qw(:flock);
+use LONCAPA;
+use File::Basename;
+
+ 
 
 # ---------------------------------------------------- Globals for this package
 
-my $pc;      # Package counter
+my $pc;      # Package counter is this what 'Guts' calls the map counter?
 my %hash;    # The big tied hash
 my %parmhash;# The hash with the parameters
 my @cond;    # Array with all of the conditions
 my $errtext; # variable with all errors
-my $retfurl; # variable with the very first URL in the course
+my $retfrid; # variable with the very first RID in the course
+my $retfurl; # first URL
 my %randompick; # randomly picked resources
 my %randompickseed; # optional seed for randomly picking resources
+my %randomorder; # maps to order contents randomly
 my %encurl; # URLs in this folder are supposed to be encrypted
 my %hiddenurl; # this URL (or complete folder) is supposed to be hidden
 
 # ----------------------------------- Remove version from URL and store in hash
 
+sub versionerror {
+    my ($uri,$usedversion,$unusedversion)=@_;
+    return '<br />'.&mt('Version discrepancy: resource [_1] included in both version [_2] and version [_3]. Using version [_2].',
+                    $uri,$usedversion,$unusedversion).'<br />';
+}
+
 sub versiontrack {
     my $uri=shift;
     if ($uri=~/\.(\d+)\.\w+$/) {
@@ -65,7 +77,9 @@ sub versiontrack {
 	$uri=~s/\.\d+\.(\w+)$/\.$1/;
         unless ($hash{'version_'.$uri}) {
 	    $hash{'version_'.$uri}=$version;
-	}
+	} elsif ($version!=$hash{'version_'.$uri}) {
+            $errtext.=&versionerror($uri,$hash{'version_'.$uri},$version);
+        }
     }
     return $uri;
 }
@@ -74,6 +88,7 @@ sub versiontrack {
 
 sub putinversion {
     my $uri=shift;
+    my $key=$env{'request.course.id'}.'_'.&Apache::lonnet::clutter($uri);
     if ($hash{'version_'.$uri}) {
 	my $version=$hash{'version_'.$uri};
 	if ($version eq 'mostrecent') { return $uri; }
@@ -82,6 +97,7 @@ sub putinversion {
 	             { return $uri; }
 	$uri=~s/\.(\w+)$/\.$version\.$1/;
     }
+    &Apache::lonnet::do_cache_new('courseresversion',$key,&Apache::lonnet::declutter($uri),600);
     return $uri;
 }
 
@@ -92,298 +108,542 @@ sub processversionfile {
     my %versions=&Apache::lonnet::dump('resourceversions',
 				       $cenv{'domain'},
 				       $cenv{'num'});
-    foreach (keys %versions) {
-	if ($_=~/^error\:/) { return; }
-	$hash{'version_'.$_}=$versions{$_};
+    foreach my $ver (keys(%versions)) {
+	if ($ver=~/^error\:/) { return; }
+	$hash{'version_'.$ver}=$versions{$ver};
     }
 }
 
-# --------------------------------------------------------- Loads map from disk
+# --------------------------------------------------------- Loads from disk
 
 sub loadmap { 
-    my $uri=shift;
-    if ($hash{'map_pc_'.$uri}) { return OK; }
+    my ($uri,$parent_rid)=@_;
+
+    # Is the map already included?
+
+    if ($hash{'map_pc_'.$uri}) { 
+	$errtext.='<p class="LC_error">'.
+	    &mt('Multiple use of sequence/page [_1]! The course will not function properly.','<tt>'.$uri.'</tt>').
+	    '</p>';
+	return; 
+    }
+    # Register the resource in it's map_pc_ [for the URL]
+    # map_id.nnn is the nesting level -> to the URI.
 
     $pc++;
     my $lpc=$pc;
     $hash{'map_pc_'.$uri}=$lpc;
     $hash{'map_id_'.$lpc}=$uri;
 
-# Determine and check filename
+    # If the parent is of the form n.m hang this map underneath it in the
+    # map hierarchy.
+
+    if ($parent_rid =~ /^(\d+)\.\d+$/) {
+        my $parent_pc = $1;
+        if (defined($hash{'map_hierarchy_'.$parent_pc})) {
+            $hash{'map_hierarchy_'.$lpc}=$hash{'map_hierarchy_'.$parent_pc}.','.
+                                         $parent_pc;
+        } else {
+            $hash{'map_hierarchy_'.$lpc}=$parent_pc;
+        }
+    }
+
+# Determine and check filename of the sequence we need to read:
+
     my $fn=&Apache::lonnet::filelocation('',&putinversion($uri));
 
     my $ispage=($fn=~/\.page$/);
 
-    unless (($fn=~/\.sequence$/) ||
-            ($fn=~/\.page$/)) { 
-       $errtext.="Invalid map: $fn\n";
-       return OK; 
+    # We can only nest sequences or pages.  Anything else is an illegal nest.
+
+    unless (($fn=~/\.sequence$/) || $ispage) { 
+	$errtext.=&mt("<br />Invalid map: <tt>[_1]</tt>",$fn);
+	return; 
     }
 
+    # Read the XML that constitutes the file.
+
     my $instr=&Apache::lonnet::getfile($fn);
 
-    unless ($instr eq -1) {
+    if ($instr eq -1) {
+        $errtext.=&mt('<br />Map not loaded: The file <tt>[_1]</tt> does not exist.',$fn);
+	return;
+    }
+
+    # Successfully got file, parse it
+
+    # parse for parameter processing.
+    # Note that these are <param... / > tags
+    # so we only care about 'S' (tag start) nodes.
+
+
+    my $parser = HTML::TokeParser->new(\$instr);
+    $parser->attr_encoded(1);
+
+    # first get all parameters
+
+
+    while (my $token = $parser->get_token) {
+	next if ($token->[0] ne 'S');
+	if ($token->[1] eq 'param') {
+	    &parse_param($token,$lpc);
+	} 
+    }
+
+    # Get set to take another pass through the XML:
+    # for resources and links.
+
+    $parser = HTML::TokeParser->new(\$instr);
+    $parser->attr_encoded(1);
 
-# Successfully got file, parse it
+    my $linkpc=0;
 
-        my $parser = HTML::TokeParser->new(\$instr);
-        my $token;
+    $fn=~/\.(\w+)$/;
 
-        my $linkpc=0;
+    $hash{'map_type_'.$lpc}=$1;
 
-        $fn=~/\.(\w+)$/;
+    my $randomize = ($randomorder{$parent_rid} =~ /^yes$/i);
+
+    # Parse the resources, link and condition tags.
+    # Note that if randomorder or random select is chosen the links and
+    # conditions are meaningless but are determined by the randomization.
+    # This is handled in the next chunk of code.
+
+    my @map_ids;
+    while (my $token = $parser->get_token) {
+	next if ($token->[0] ne 'S');
+
+	# Resource
+
+	if ($token->[1] eq 'resource') {
+	    my $resource_id = &parse_resource($token,$lpc,$ispage,$uri);
+	    if (defined $resource_id) {
+		push(@map_ids, $resource_id);
+	    }
+
+       # Link
+
+	} elsif ($token->[1] eq 'link' && !$randomize) {
+	    &make_link(++$linkpc,$lpc,$token->[2]->{'to'},
+		       $token->[2]->{'from'},
+		       $token->[2]->{'condition'});
+
+	# condition
+
+	} elsif ($token->[1] eq 'condition' && !$randomize) {
+	    &parse_condition($token,$lpc);
+	}
+    }
+
+
+    # Handle randomization and random selection
+
+    if ($randomize) {
+	if (!$env{'request.role.adv'}) {
+	    my $seed;
+	    if (defined($randompickseed{$parent_rid})) {
+		$seed = $randompickseed{$parent_rid};
+	    } else {
+		my ($mapid,$resid)=split(/\./,$parent_rid);
+		my $symb=
+		    &Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},
+						 $resid,$hash{'src_'.$parent_rid});
+		
+		$seed = $symb;
+	    }
+
+	    # Here for sure we need to pass along the username/domain
+	    # so that we can impersonate users in lonprintout e.g.
+
+	    my $rndseed=&Apache::lonnet::rndseed($seed);
+	    &Apache::lonnet::setup_random_from_rndseed($rndseed);
+	    @map_ids=&Math::Random::random_permutation(@map_ids);
+	}
+	my $from = shift(@map_ids);
+	my $from_rid = $lpc.'.'.$from;
+	$hash{'map_start_'.$uri} = $from_rid;
+	$hash{'type_'.$from_rid}='start';
+
+	while (my $to = shift(@map_ids)) {
+	    &make_link(++$linkpc,$lpc,$to,$from);
+	    my $to_rid =  $lpc.'.'.$to;
+	    $hash{'type_'.$to_rid}='normal';
+	    $from = $to;
+	    $from_rid = $to_rid;
+	}
+
+	$hash{'map_finish_'.$uri}= $from_rid;
+	$hash{'type_'.$from_rid}='finish';
+    }
+
+    $parser = HTML::TokeParser->new(\$instr);
+    $parser->attr_encoded(1);
+    # last parse out the mapalias params so as to ignore anything
+    # refering to non-existant resources
+    while (my $token = $parser->get_token) {
+	next if ($token->[0] ne 'S');
+	if ($token->[1] eq 'param') {
+	    &parse_mapalias_param($token,$lpc);
+	} 
+    }
+}
 
-        $hash{'map_type_'.$lpc}=$1;
 
-        while ($token = $parser->get_token) {
-	    if ($token->[0] eq 'S') {
-                if ($token->[1] eq 'resource') {
 # -------------------------------------------------------------------- Resource
+#
+#  Parses a resource tag to produce the value to push into the
+#  map_ids array.
+# 
+#
+#  Information about the actual type of resource is provided by the file extension
+#  of the uri (e.g. .problem, .sequence etc. etc.).
+#
+#  Parameters:
+#    $token   - A token from HTML::TokeParser
+#               This is an array that describes the most recently parsed HTML item.
+#    $lpc     - Map nesting level (?)
+#    $ispage  - True if this resource is encapsulated in a .page (assembled resourcde).
+#    $uri     - URI of the enclosing resource.
+# Returns:
+#
+# Note:
+#   The token is an array that contains the following elements:
+#   [0]   => 'S' indicating this is a start token
+#   [1]   => 'resource'  indicating this tag is a <resource> tag.
+#   [2]   => Hash of attribute =>value pairs.
+#   [3]   => @(keys [2]).
+#   [4]   => unused.
+#
+#   The attributes of the resourcde tag include:
+#
+#   id     - The resource id.
+#   src    - The URI of the resource.
+#   type   - The resource type (e.g. start and finish).
+#   title  - The resource title.
+
+
+sub parse_resource {
+    my ($token,$lpc,$ispage,$uri) = @_;
+    
+    # I refuse to coutenance code like this that has 
+    # such a dirty side effect (and forcing this sub to be called within a loop).
+    #
+    #  if ($token->[2]->{'type'} eq 'zombie') { next; }
 
-                    my $rid=$lpc.'.'.$token->[2]->{'id'};
+    # Zombie resources don't produce anything useful.
 
-                    $hash{'kind_'.$rid}='res';
-                    $hash{'title_'.$rid}=$token->[2]->{'title'};
-                    my $turi=&versiontrack($token->[2]->{'src'});
-                    if ($token->[2]->{'version'}) {
-			unless ($hash{'version_'.$turi}) {
-			    $hash{'version_'.$turi}=$1;
-			}
-		    }
-		    &Apache::lonnet::do_cache(\%Apache::lonnet::titlecache,
-		       &Apache::lonnet::encode_symb($uri,$token->[2]->{'id'},
-						    $turi),
-					      $token->[2]->{'title'},'title');
-                    unless ($ispage) {
-                        $turi=~/\.(\w+)$/;
-                        my $embstyle=&Apache::loncommon::fileembstyle($1);
-                        if ($token->[2]->{'external'} eq 'true') { # external
-                            $turi=~s/^http\:\/\//\/adm\/wrapper\/ext\//;
-                        } elsif ($turi=~/^\/*uploaded\//) { # uploaded
-			    if (($embstyle eq 'img') || ($embstyle eq 'emb')) {
-                                $turi='/adm/wrapper'.$turi;
-			    } elsif ($embstyle eq 'ssi') {
-				#do nothing with these
-			    } elsif ($turi!~/\.(sequence|page)$/) {
-				$turi='/adm/coursedocs/showdoc'.$turi;
-                            }
-                        } elsif ($turi=~/\S/) { # normal non-empty internal resource
-			    my $mapdir=$uri;
-			    $mapdir=~s/[^\/]+$//;
-			    $turi=&Apache::lonnet::hreflocation($mapdir,$turi);
-			    if (($embstyle eq 'img') || ($embstyle eq 'emb')) {
-				$turi='/adm/wrapper'.$turi;
-			    }
-                        }
-		    }
+    if ($token->[2]->{'type'} eq 'zombie') {
+	return undef;
+    }
+
+    my $rid=$lpc.'.'.$token->[2]->{'id'};
+	    
+    $hash{'kind_'.$rid}='res';
+    $hash{'title_'.$rid}=$token->[2]->{'title'};
+    my $turi=&versiontrack($token->[2]->{'src'});
+    if ($token->[2]->{'version'}) {
+	unless ($hash{'version_'.$turi}) {
+	    $hash{'version_'.$turi}=$1;
+	}
+    }
+    my $title=$token->[2]->{'title'};
+    $title=~s/\&colon\;/\:/gs;
+#   my $symb=&Apache::lonnet::encode_symb($uri,
+#					  $token->[2]->{'id'},
+#					  $turi);
+#   &Apache::lonnet::do_cache_new('title',$symb,$title);
+    unless ($ispage) {
+	$turi=~/\.(\w+)$/;
+	my $embstyle=&Apache::loncommon::fileembstyle($1);
+	if ($token->[2]->{'external'} eq 'true') { # external
+	    $turi=~s/^https?\:\/\//\/adm\/wrapper\/ext\//;
+	} elsif ($turi=~/^\/*uploaded\//) { # uploaded
+	    if (($embstyle eq 'img') 
+		|| ($embstyle eq 'emb')
+		|| ($embstyle eq 'wrp')) {
+		$turi='/adm/wrapper'.$turi;
+	    } elsif ($embstyle eq 'ssi') {
+		#do nothing with these
+	    } elsif ($turi!~/\.(sequence|page)$/) {
+		$turi='/adm/coursedocs/showdoc'.$turi;
+	    }
+	} elsif ($turi=~/\S/) { # normal non-empty internal resource
+	    my $mapdir=$uri;
+	    $mapdir=~s/[^\/]+$//;
+	    $turi=&Apache::lonnet::hreflocation($mapdir,$turi);
+	    if (($embstyle eq 'img') 
+		|| ($embstyle eq 'emb')
+		|| ($embstyle eq 'wrp')) {
+		$turi='/adm/wrapper'.$turi;
+	    }
+	}
+    }
 # Store reverse lookup, remove query string
-		    my $idsuri=$turi;
-		    $idsuri=~s/\?.+$//;
-                    if (defined($hash{'ids_'.$idsuri})) {
-                        $hash{'ids_'.$idsuri}.=','.$rid;
-                    } else {
-                        $hash{'ids_'.$idsuri}=''.$rid;
-                    }
-               
-                    if
-	        ($turi=~/\/(syllabus|aboutme|navmaps|smppg|bulletinboard)$/) {
-			$turi.='?register=1';
-		    }
+    my $idsuri=$turi;
+    $idsuri=~s/\?.+$//;
+    if (defined($hash{'ids_'.$idsuri})) {
+	$hash{'ids_'.$idsuri}.=','.$rid;
+    } else {
+	$hash{'ids_'.$idsuri}=''.$rid;
+    }
+    
+    if ($turi=~/\/(syllabus|aboutme|navmaps|smppg|bulletinboard|viewclasslist)$/) {
+	$turi.='?register=1';
+    }
+    
+    $hash{'src_'.$rid}=$turi;
+    
+    if ($token->[2]->{'external'} eq 'true') {
+	$hash{'ext_'.$rid}='true:';
+    } else {
+	$hash{'ext_'.$rid}='false:';
+    }
+    if ($token->[2]->{'type'}) {
+	$hash{'type_'.$rid}=$token->[2]->{'type'};
+	if ($token->[2]->{'type'} eq 'start') {
+	    $hash{'map_start_'.$uri}="$rid";
+	}
+	if ($token->[2]->{'type'} eq 'finish') {
+	    $hash{'map_finish_'.$uri}="$rid";
+	}
+    }  else {
+	$hash{'type_'.$rid}='normal';
+    }
+    
+    if (($turi=~/\.sequence$/) ||
+	($turi=~/\.page$/)) {
+	$hash{'is_map_'.$rid}=1;
+	&loadmap($turi,$rid);
+    } 
+    return $token->[2]->{'id'};
+}
 
-                    $hash{'src_'.$rid}=$turi;
+sub make_link {
+    my ($linkpc,$lpc,$to,$from,$condition) = @_;
+    
+    my $linkid=$lpc.'.'.$linkpc;
+    my $goesto=$lpc.'.'.$to;
+    my $comesfrom=$lpc.'.'.$from;
+    my $undercond=0;
 
-                    if ($token->[2]->{'external'} eq 'true') {
-                        $hash{'ext_'.$rid}='true:';
-                    } else {
-                        $hash{'ext_'.$rid}='false:';
-                    }
-                    if ($token->[2]->{'type'}) {
-			$hash{'type_'.$rid}=$token->[2]->{'type'};
-                        if ($token->[2]->{'type'} eq 'start') {
-			    $hash{'map_start_'.$uri}="$rid";
-                        }
-                        if ($token->[2]->{'type'} eq 'finish') {
-			    $hash{'map_finish_'.$uri}="$rid";
-                        }
-                    }  else {
-                        $hash{'type_'.$rid}='normal';
-                    }
+    if ($condition) {
+	$undercond=$lpc.'.'.$condition;
+    }
+
+    $hash{'goesto_'.$linkid}=$goesto;
+    $hash{'comesfrom_'.$linkid}=$comesfrom;
+    $hash{'undercond_'.$linkid}=$undercond;
+
+    if (defined($hash{'to_'.$comesfrom})) {
+	$hash{'to_'.$comesfrom}.=','.$linkid;
+    } else {
+	$hash{'to_'.$comesfrom}=''.$linkid;
+    }
+    if (defined($hash{'from_'.$goesto})) {
+	$hash{'from_'.$goesto}.=','.$linkid;
+    } else {
+	$hash{'from_'.$goesto}=''.$linkid;
+    }
+}
 
-                    if (($turi=~/\.sequence$/) ||
-                        ($turi=~/\.page$/)) {
-                        $hash{'is_map_'.$rid}=1;
-                        &loadmap($turi);
-                    } 
-                    
-                } elsif ($token->[1] eq 'condition') {
 # ------------------------------------------------------------------- Condition
+sub parse_condition {
+    my ($token,$lpc) = @_;
+    my $rid=$lpc.'.'.$token->[2]->{'id'};
+    
+    $hash{'kind_'.$rid}='cond';
+
+    my $condition = $token->[2]->{'value'};
+    $condition =~ s/[\n\r]+/ /gs;
+    push(@cond, $condition);
+    $hash{'condid_'.$rid}=$#cond;
+    if ($token->[2]->{'type'}) {
+	$cond[$#cond].=':'.$token->[2]->{'type'};
+    }  else {
+	$cond[$#cond].=':normal';
+    }
+}
 
-                    my $rid=$lpc.'.'.$token->[2]->{'id'};
+# ------------------------------------------------------------------- Parameter
+# Parse a <parameter> tag in the map.
+# Parmameters:
+#    $token Token array for a start tag from HTML::TokeParser
+#           [0] = 'S'
+#           [1] = tagname ("param")
+#           [2] = Hash of {attribute} = values.
+#           [3] = Array of the keys in [2].
+#           [4] = unused.
+#    $lpc   Current map nesting level.a
+#
+#  Typical attributes:
+#     to=n      - Number of the resource the parameter applies to.
+#     type=xx   - Type of parameter value (e.g. string_yesno or int_pos).
+#     name=xxx  - Name ofr parameter (e.g. parameter_randompick or parameter_randomorder).
+#     value=xxx - value of the parameter.
+
+sub parse_param {
+    my ($token,$lpc) = @_;
+    my $referid=$lpc.'.'.$token->[2]->{'to'}; # Resource param applies to.
+    my $name=$token->[2]->{'name'};	      # Name of parameter
+    my $part;
 
-                    $hash{'kind_'.$rid}='cond';
-                    $cond[$#cond+1]=$token->[2]->{'value'};
-                    $hash{'condid_'.$rid}=$#cond;
-                    if ($token->[2]->{'type'}) {
-                        $cond[$#cond].=':'.$token->[2]->{'type'};
-                    }  else {
-                        $cond[$#cond].=':normal';
-                    }
 
-                } elsif ($token->[1] eq 'link') {
-# ----------------------------------------------------------------------- Links
+    if ($name=~/^parameter_(.*)_/) { 
+	$part=$1;
+    } else {
+	$part=0;
+    }
 
-                    $linkpc++;
-                    my $linkid=$lpc.'.'.$linkpc;
+    # Peel the parameter_ off the parameter name.
 
-                    my $goesto=$lpc.'.'.$token->[2]->{'to'};
-                    my $comesfrom=$lpc.'.'.$token->[2]->{'from'};
-                    my $undercond=0;
+    $name=~s/^.*_([^_]*)$/$1/;
 
-                    if ($token->[2]->{'condition'}) {
-			$undercond=$lpc.'.'.$token->[2]->{'condition'};
-                    }
+    # The value is:
+    #   type.part.name.value
 
-                    $hash{'goesto_'.$linkid}=$goesto;
-                    $hash{'comesfrom_'.$linkid}=$comesfrom;
-                    $hash{'undercond_'.$linkid}=$undercond;
-
-                    if (defined($hash{'to_'.$comesfrom})) {
-                        $hash{'to_'.$comesfrom}.=','.$linkid;
-                    } else {
-                        $hash{'to_'.$comesfrom}=''.$linkid;
-                    }
-                    if (defined($hash{'from_'.$goesto})) {
-                        $hash{'from_'.$goesto}.=','.$linkid;
-                    } else {
-                        $hash{'from_'.$goesto}=''.$linkid;
-                    }
-                } elsif ($token->[1] eq 'param') {
-# ------------------------------------------------------------------- Parameter
+    my $newparam=
+	&escape($token->[2]->{'type'}).':'.
+	&escape($part.'.'.$name).'='.
+	&escape($token->[2]->{'value'});
 
-                    my $referid=$lpc.'.'.$token->[2]->{'to'};
-		    my $name=$token->[2]->{'name'};
-		    my $part;
-		    if ($name=~/^parameter_(.*)_/) {
-			$part=$1;
-		    } else {
-			$part=0;
-		    }
-		    $name=~s/^.*_([^_]*)$/$1/;
-                    my $newparam=
-			&Apache::lonnet::escape($token->[2]->{'type'}).':'.
-			&Apache::lonnet::escape($part.'.'.$name).'='.
-			&Apache::lonnet::escape($token->[2]->{'value'});
-                    if (defined($hash{'param_'.$referid})) {
-                        $hash{'param_'.$referid}.='&'.$newparam;
-                    } else {
-                        $hash{'param_'.$referid}=''.$newparam;
-                    }
-                    if ($token->[2]->{'name'}=~/^parameter_(0_)*mapalias$/) {
-			$hash{'mapalias_'.$token->[2]->{'value'}}=$referid;
-                    }
-                    if ($token->[2]->{'name'}=~/^parameter_(0_)*randompick$/) {
-			$randompick{$referid}=$token->[2]->{'value'};
-                    }
-                    if ($token->[2]->{'name'}=~/^parameter_(0_)*randompickseed$/) {
-			$randompick{$referid}=$token->[2]->{'value'};
-                    }
-                    if ($token->[2]->{'name'}=~/^parameter_(0_)*encrypturl$/) {
-			if ($token->[2]->{'value'}=~/^yes$/i) {
-			    $hiddenurl{$referid}=1;
-			}
-                    }
-                    if ($token->[2]->{'name'}=~/^parameter_(0_)*hiddenresource$/) {
-			if ($token->[2]->{'value'}=~/^yes$/i) {
-			    $hiddenurl{$referid}=1;
-			}
-                    }
-                } 
+    # The hash key is param_resourceid.
+    # Multiple parameters for a single resource are & separated in the hash.
 
-            }
-        }
 
+    if (defined($hash{'param_'.$referid})) {
+	$hash{'param_'.$referid}.='&'.$newparam;
     } else {
-        $errtext.='Map not loaded: The file does not exist. ';
+	$hash{'param_'.$referid}=''.$newparam;
+    }
+    #
+    #  These parameters have to do with randomly selecting
+    # resources, therefore a separate hash is also created to 
+    # make it easy to locate them when actually computing the resource set later on
+    # See the code conditionalized by ($randomize) in loadmap().
+
+    if ($token->[2]->{'name'}=~/^parameter_(0_)*randompick$/) { # Random selection turned on
+	$randompick{$referid}=$token->[2]->{'value'};
+    }
+    if ($token->[2]->{'name'}=~/^parameter_(0_)*randompickseed$/) { # Randomseed provided.
+	$randompickseed{$referid}=$token->[2]->{'value'};
+    }
+    if ($token->[2]->{'name'}=~/^parameter_(0_)*randomorder$/) { # Random order turned on.
+	$randomorder{$referid}=$token->[2]->{'value'};
+    }
+
+    # These parameters have to do with how the URLs of resources are presented to
+    # course members(?).  encrypturl presents encypted url's while
+    # hiddenresource hides the URL.
+    #
+
+    if ($token->[2]->{'name'}=~/^parameter_(0_)*encrypturl$/) {
+	if ($token->[2]->{'value'}=~/^yes$/i) {
+	    $encurl{$referid}=1;
+	}
+    }
+    if ($token->[2]->{'name'}=~/^parameter_(0_)*hiddenresource$/) {
+	if ($token->[2]->{'value'}=~/^yes$/i) {
+	    $hiddenurl{$referid}=1;
+	}
+    }
+}
+
+sub parse_mapalias_param {
+    my ($token,$lpc) = @_;
+    my $referid=$lpc.'.'.$token->[2]->{'to'};
+    return if (!exists($hash{'src_'.$referid}));
+
+    if ($token->[2]->{'name'}=~/^parameter_(0_)*mapalias$/) {
+	&count_mapalias($token->[2]->{'value'},$referid);
+	$hash{'mapalias_'.$token->[2]->{'value'}}=$referid;
     }
 }
 
 # --------------------------------------------------------- Simplify expression
 
 sub simplify {
-   my $expression=shift;
+    my $expression=shift;
+# (0&1) = 1
+    $expression=~s/\(0\&([_\.\d]+)\)/$1/g;
 # (8)=8
-   $expression=~s/\((\d+)\)/$1/g;
+    $expression=~s/\(([_\.\d]+)\)/$1/g;
 # 8&8=8
-   $expression=~s/(\D)(\d+)\&\2(\D)/$1$2$3/g;
+    $expression=~s/([^_\.\d])([_\.\d]+)\&\2([^_\.\d])/$1$2$3/g;
 # 8|8=8
-   $expression=~s/(\D)(\d+)\|\2(\D)/$1$2$3/g;
+    $expression=~s/([^_\.\d])([_\.\d]+)\|\2([^_\.\d])/$1$2$3/g;
 # (5&3)&4=5&3&4
-   $expression=~s/\((\d+)((?:\&\d+)+)\)\&(\d+\D)/$1$2\&$3/g;
+    $expression=~s/\(([_\.\d]+)((?:\&[_\.\d]+)+)\)\&([_\.\d]+[^_\.\d])/$1$2\&$3/g;
 # (((5&3)|(4&6)))=((5&3)|(4&6))
-   $expression=~
-       s/\((\(\(\d+(?:\&\d+)*\)(?:\|\(\d+(?:\&\d+)*\))+\))\)/$1/g;
+    $expression=~
+	s/\((\(\([_\.\d]+(?:\&[_\.\d]+)*\)(?:\|\([_\.\d]+(?:\&[_\.\d]+)*\))+\))\)/$1/g;
 # ((5&3)|(4&6))|(1&2)=(5&3)|(4&6)|(1&2)
-   $expression=~
-       s/\((\(\d+(?:\&\d+)*\))((?:\|\(\d+(?:\&\d+)*\))+)\)\|(\(\d+(?:\&\d+)*\))/\($1$2\|$3\)/g;
-   return $expression;
+    $expression=~
+	s/\((\([_\.\d]+(?:\&[_\.\d]+)*\))((?:\|\([_\.\d]+(?:\&[_\.\d]+)*\))+)\)\|(\([_\.\d]+(?:\&[_\.\d]+)*\))/\($1$2\|$3\)/g;
+    return $expression;
 }
 
 # -------------------------------------------------------- Build condition hash
 
 sub traceroute {
     my ($sofar,$rid,$beenhere,$encflag,$hdnflag)=@_;
-    $sofar=simplify($sofar);
-    unless ($beenhere=~/\&$rid\&/) {
-       $beenhere.=$rid.'&';  
-       if ($hdnflag) {
-	   $hiddenurl{$rid}=1;
-       }
-       if ($encflag) {
-	   $encurl{$rid}=1;
-       }
-       if (($retfurl eq '') && ($hash{'src_'.$rid})
-        && ($hash{'src_'.$rid}!~/\.sequence$/)) {
-           my ($mapid,$resid)=split(/\./,$rid);
-           $retfurl=$hash{'src_'.$rid}.
-           (($hash{'src_'.$rid}=~/\?/)?'&':'?').'symb='.
-           &Apache::lonnet::symbclean(
-                           &Apache::lonnet::declutter($hash{'map_id_'.$mapid}).
-                           '___'.$resid.'___'.
-                           &Apache::lonnet::declutter($hash{'src_'.$rid}));
-       }
-       if (defined($hash{'conditions_'.$rid})) {
-	   $hash{'conditions_'.$rid}=simplify(
+    my $newsofar=$sofar=simplify($sofar);
+    unless ($beenhere=~/\&\Q$rid\E\&/) {
+	$beenhere.=$rid.'&';  
+	my ($mapid,$resid)=split(/\./,$rid);
+	my $symb=&Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},$resid,$hash{'src_'.$rid});
+	my $hidden=&Apache::lonnet::EXT('resource.0.hiddenresource',$symb);
+
+	if ($hdnflag || lc($hidden) eq 'yes') {
+	    $hiddenurl{$rid}=1;
+	}
+	if (!$hdnflag && lc($hidden) eq 'no') {
+	    delete($hiddenurl{$rid});
+	}
+
+	my $encrypt=&Apache::lonnet::EXT('resource.0.encrypturl',$symb);
+	if ($encflag || lc($encrypt) eq 'yes') { $encurl{$rid}=1; }
+	if (($retfrid eq '') && ($hash{'src_'.$rid})
+	    && ($hash{'src_'.$rid}!~/\.sequence$/)) {
+	    $retfrid=$rid;
+	}
+	if (defined($hash{'conditions_'.$rid})) {
+	    $hash{'conditions_'.$rid}=simplify(
            '('.$hash{'conditions_'.$rid}.')|('.$sofar.')');
-       } else {
-           $hash{'conditions_'.$rid}=$sofar;
-       }
-       if (defined($hash{'is_map_'.$rid})) {
-           if (defined($hash{'map_start_'.$hash{'src_'.$rid}})) {
-	       &traceroute($sofar,$hash{'map_start_'.$hash{'src_'.$rid}},'&',
-			   $encflag || $encurl{$rid},
-			   $hdnflag || $hiddenurl{$rid});
-               if (defined($hash{'map_finish_'.$hash{'src_'.$rid}})) {
-		   $sofar=
-                  $hash{'conditions_'.$hash{'map_finish_'.$hash{'src_'.$rid}}};
-               }
-           }
-       }
-       if (defined($hash{'to_'.$rid})) {
-          foreach (split(/\,/,$hash{'to_'.$rid})) {
+	} else {
+	    $hash{'conditions_'.$rid}=$sofar;
+	}
+
+	# if the expression is just the 0th condition keep it
+	# otherwise leave a pointer to this condition expression
+	$newsofar = ($sofar eq '0') ? $sofar : '_'.$rid;
+
+	if (defined($hash{'is_map_'.$rid})) {
+	    if (defined($hash{'map_start_'.$hash{'src_'.$rid}})) {
+		$sofar=$newsofar=
+		    &traceroute($sofar,
+				$hash{'map_start_'.$hash{'src_'.$rid}},
+				$beenhere,
+				$encflag || $encurl{$rid},
+				$hdnflag || $hiddenurl{$rid});
+	    }
+	}
+	if (defined($hash{'to_'.$rid})) {
+	    foreach my $id (split(/\,/,$hash{'to_'.$rid})) {
 		my $further=$sofar;
-                if ($hash{'undercond_'.$_}) {
-		   if (defined($hash{'condid_'.$hash{'undercond_'.$_}})) {
-  		       $further=simplify('('.$further.')&('.
-                              $hash{'condid_'.$hash{'undercond_'.$_}}.')');
-		   } else {
-                       $errtext.='Undefined condition ID: '
-                                 .$hash{'undercond_'.$_}.'. ';
-                   }
+                if ($hash{'undercond_'.$id}) {
+		    if (defined($hash{'condid_'.$hash{'undercond_'.$id}})) {
+			$further=simplify('('.'_'.$rid.')&('.
+					  $hash{'condid_'.$hash{'undercond_'.$id}}.')');
+		    } else {
+			$errtext.=&mt('<br />Undefined condition ID: [_1]',$hash{'undercond_'.$id});
+		    }
                 }
-                &traceroute($further,$hash{'goesto_'.$_},$beenhere,$encflag,$hdnflag);
-          }
-       }
+                $newsofar=&traceroute($further,$hash{'goesto_'.$id},$beenhere,
+				      $encflag,$hdnflag);
+	    }
+	}
     }
+    return $newsofar;
 }
 
 # ------------------------------ Cascading conditions, quick access, parameters
@@ -394,84 +654,78 @@ sub accinit {
     my %captured=();
     my $condcounter=0;
     $acchash{'acc.cond.'.$short.'.0'}=0;
-    foreach (keys %hash) {
-       if ($_=~/^conditions/) {
-	  my $expr=$hash{$_};
-         foreach ($expr=~m/(\(\(\d+(?:\&\d+)+\)(?:\|\(\d+(?:\&\d+)+\))+\))/g) {
-             my $sub=$_;
-             my $orig=$_;
-      $sub=~/\(\((\d+\&(:?\d+\&)*)(?:\d+\&*)+\)(?:\|\(\1(?:\d+\&*)+\))+\)/;
-             my $factor=$1;
-             $sub=~s/$factor//g;
-             $sub=~s/^\(/\($factor\(/;
-	     $sub.=')';
-             $sub=simplify($sub);
-             $orig=~s/(\W)/\\$1/g;
- 	     $expr=~s/$orig/$sub/;
-	  }
-          $hash{$_}=$expr;
-          unless (defined($captured{$expr})) {
-	      $condcounter++;
-              $captured{$expr}=$condcounter;
-              $acchash{'acc.cond.'.$short.'.'.$condcounter}=$expr;
-          } 
-       } elsif ($_=~/^param_(\d+)\.(\d+)/) {
-          my $prefix=&Apache::lonnet::declutter($hash{'map_id_'.$1}).
-      '___'.$2.'___'.&Apache::lonnet::declutter($hash{'src_'.$1.'.'.$2});
-          foreach (split(/\&/,$hash{$_})) {
-	     my ($typename,$value)=split(/\=/,$_);
-             my ($type,$name)=split(/\:/,$typename);
-             $parmhash{$prefix.'.'.&Apache::lonnet::unescape($name)}=
-                                   &Apache::lonnet::unescape($value);
-	     $parmhash{$prefix.'.'.&Apache::lonnet::unescape($name).'.type'}=
-                                   &Apache::lonnet::unescape($type);
-          }
-       }
-    }
-    foreach (keys %hash) {
-	if ($_=~/^ids/) {
-	  foreach (split(/\,/,$hash{$_})) {
-	    my $resid=$_;
-            my $uri=$hash{'src_'.$resid};
-            $uri=~s/^\/adm\/wrapper//;
-            $uri=&Apache::lonnet::declutter($uri);
-            my @uriparts=split(/\//,$uri);
-            my $urifile=$uriparts[$#uriparts];
-            $#uriparts--;
-            my $uripath=join('/',@uriparts);
-           if ($uripath) {
-            my $uricond='0';
-            if (defined($hash{'conditions_'.$resid})) {
- 		$uricond=$captured{$hash{'conditions_'.$resid}};
-            }
-            if (defined($acchash{'acc.res.'.$short.'.'.$uripath})) {
-                if ($acchash{'acc.res.'.$short.'.'.$uripath}=~
-                   /(\&\Q$urifile\E\:[^\&]*)/) {
-		    my $replace=$1;
-                    my $regexp=$replace;
-                    #$regexp=~s/\|/\\\|/g;
-                    $acchash{'acc.res.'.$short.'.'.$uripath}
-                     =~s/\Q$regexp\E/$replace\|$uricond/;
-                } else {
-		   $acchash{'acc.res.'.$short.'.'.$uripath}.=
-                     $urifile.':'.$uricond.'&';
-	        }
-            } else {
-                $acchash{'acc.res.'.$short.'.'.$uripath}=
-                 '&'.$urifile.':'.$uricond.'&';
-            }
-           } 
-         }
-      }
+    foreach my $key (keys(%hash)) {
+	if ($key=~/^conditions/) {
+	    my $expr=$hash{$key};
+	    # try to find and factor out common sub-expressions
+	    foreach my $sub ($expr=~m/(\(\([_\.\d]+(?:\&[_\.\d]+)+\)(?:\|\([_\.\d]+(?:\&[_\.\d]+)+\))+\))/g) {
+		my $orig=$sub;
+
+		my ($factor) = ($sub=~/\(\(([_\.\d]+\&(:?[_\.\d]+\&)*)(?:[_\.\d]+\&*)+\)(?:\|\(\1(?:[_\.\d]+\&*)+\))+\)/);
+		next if (!defined($factor));
+
+		$sub=~s/\Q$factor\E//g;
+		$sub=~s/^\(/\($factor\(/;
+		$sub.=')';
+		$sub=simplify($sub);
+		$expr=~s/\Q$orig\E/$sub/;
+	    }
+	    $hash{$key}=$expr;
+	    unless (defined($captured{$expr})) {
+		$condcounter++;
+		$captured{$expr}=$condcounter;
+		$acchash{'acc.cond.'.$short.'.'.$condcounter}=$expr;
+	    } 
+	} elsif ($key=~/^param_(\d+)\.(\d+)/) {
+	    my $prefix=&Apache::lonnet::encode_symb($hash{'map_id_'.$1},$2,
+						    $hash{'src_'.$1.'.'.$2});
+	    foreach my $param (split(/\&/,$hash{$key})) {
+		my ($typename,$value)=split(/\=/,$param);
+		my ($type,$name)=split(/\:/,$typename);
+		$parmhash{$prefix.'.'.&unescape($name)}=
+		    &unescape($value);
+		$parmhash{$prefix.'.'.&unescape($name).'.type'}=
+		    &unescape($type);
+	    }
+	}
+    }
+    foreach my $key (keys(%hash)) {
+	if ($key=~/^ids/) {
+	    foreach my $resid (split(/\,/,$hash{$key})) {
+		my $uri=$hash{'src_'.$resid};
+		my ($uripath,$urifile) =
+		    &Apache::lonnet::split_uri_for_cond($uri);
+		if ($uripath) {
+		    my $uricond='0';
+		    if (defined($hash{'conditions_'.$resid})) {
+			$uricond=$captured{$hash{'conditions_'.$resid}};
+		    }
+		    if (defined($acchash{'acc.res.'.$short.'.'.$uripath})) {
+			if ($acchash{'acc.res.'.$short.'.'.$uripath}=~
+			    /(\&\Q$urifile\E\:[^\&]*)/) {
+			    my $replace=$1;
+			    my $regexp=$replace;
+			    #$regexp=~s/\|/\\\|/g;
+			    $acchash{'acc.res.'.$short.'.'.$uripath} =~
+				s/\Q$regexp\E/$replace\|$uricond/;
+			} else {
+			    $acchash{'acc.res.'.$short.'.'.$uripath}.=
+				$urifile.':'.$uricond.'&';
+			}
+		    } else {
+			$acchash{'acc.res.'.$short.'.'.$uripath}=
+			    '&'.$urifile.':'.$uricond.'&';
+		    }
+		} 
+	    }
+	}
     }
     $acchash{'acc.res.'.$short.'.'}='&:0&';
     my $courseuri=$uri;
     $courseuri=~s/^\/res\///;
-    &Apache::lonnet::delenv('(acc\.|httpref\.)');
-    &Apache::lonnet::appenv(%acchash,
-                            "request.course.id"  => $short,
-                            "request.course.fn"  => $fn,
-                            "request.course.uri" => $courseuri); 
+    my $regexp = 1;
+    &Apache::lonnet::delenv('(acc\.|httpref\.)',$regexp);
+    &Apache::lonnet::appenv(\%acchash);
 }
 
 # ---------------- Selectively delete from randompick maps and hidden url parms
@@ -483,8 +737,8 @@ sub hiddenurls {
         my $mpc=$hash{'map_pc_'.$hash{'src_'.$rid}};
 # ------------------------------------------- put existing resources into array
         my @currentrids=();
-        foreach (sort(keys(%hash))) {
-	    if ($_=~/^src_($mpc\.\d+)/) {
+        foreach my $key (sort(keys(%hash))) {
+	    if ($key=~/^src_($mpc\.\d+)/) {
 		if ($hash{'src_'.$1}) { push @currentrids, $1; }
             }
         }
@@ -510,11 +764,10 @@ sub hiddenurls {
 		$hash{'randomout_'.$currentrids[$k]}=1;
                 my ($mapid,$resid)=split(/\./,$currentrids[$k]);
                 $randomoutentry.='&'.
-                 &Apache::lonnet::symbclean(
-		    &Apache::lonnet::declutter($hash{'map_id_'.$mapid}).
-                    '___'.$resid.'___'.
-		    &Apache::lonnet::declutter($hash{'src_'.$currentrids[$k]})
-                 ).'&';
+		    &Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},
+						 $resid,
+						 $hash{'src_'.$currentrids[$k]}
+						 ).'&';
             }
         }
     }
@@ -523,143 +776,439 @@ sub hiddenurls {
 	$hash{'randomout_'.$rid}=1;
 	my ($mapid,$resid)=split(/\./,$rid);
 	$randomoutentry.='&'.
-	    &Apache::lonnet::symbclean(
-		         &Apache::lonnet::declutter($hash{'map_id_'.$mapid}).
-				       '___'.$resid.'___'.
-		    &Apache::lonnet::declutter($hash{'src_'.$rid})
-				       ).'&';
+	    &Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},$resid,
+					 $hash{'src_'.$rid}).'&';
     }
 # --------------------------------------- append randomout entry to environment
     if ($randomoutentry) {
-	&Apache::lonnet::appenv('acc.randomout' => $randomoutentry);
+	&Apache::lonnet::appenv({'acc.randomout' => $randomoutentry});
     }
 }
 
 # ---------------------------------------------------- Read map and all submaps
 
 sub readmap {
-   my $short=shift;
-   $short=~s/^\///;
-   my %cenv=&Apache::lonnet::coursedescription($short);
-   my $fn=$cenv{'fn'};
-   my $uri;
-   $short=~s/\//\_/g;
-   unless ($uri=$cenv{'url'}) { 
-      &Apache::lonnet::logthis("<font color=blue>WARNING: ".
-                       "Could not load course $short.</font>"); 
-      return 'No course data available.';
-   }
-   @cond=('true:normal');
-   unlink($fn.'.db');
-   unlink($fn.'_symb.db');
-   unlink($fn.'.state');
-   unlink($fn.'parms.db');
-   undef %randompick;
-   undef %hiddenurl;
-   undef %encurl;
-   $retfurl='';
-   if ((tie(%hash,'GDBM_File',"$fn.db",&GDBM_WRCREAT(),0640)) &&
-       (tie(%parmhash,'GDBM_File',$fn.'_parms.db',&GDBM_WRCREAT(),0640))) {
-    %hash=();
+    my $short=shift;
+    $short=~s/^\///;
+
+    # TODO:  Hidden dependency on current user:
+
+    my %cenv=&Apache::lonnet::coursedescription($short,{'freshen_cache'=>1}); 
+
+    my $fn=$cenv{'fn'};
+    my $uri;
+    $short=~s/\//\_/g;
+    unless ($uri=$cenv{'url'}) { 
+	&Apache::lonnet::logthis('<font color="blue">WARNING: '.
+				 "Could not load course $short.</font>"); 
+	return ('',&mt('No course data available.'));;
+    }
+    @cond=('true:normal');
+
+    unless (open(LOCKFILE,">$fn.db.lock")) {
+	# 
+	# Most likely a permissions problem on the lockfile or its directory.
+	#
+        $errtext.='<br />'.&mt('Map not loaded - Lock file could not be opened when reading map:').' <tt>'.$fn.'</tt>.';
+        $retfurl = '';
+        return ($retfurl,$errtext);
+    }
+    my $lock=0;
+    my $gotstate=0;
+    
+    # If we can get the lock without delay any files there are idle
+    # and from some prior request.  We'll kill them off and regenerate them:
+
+    if (flock(LOCKFILE,LOCK_EX|LOCK_NB)) {	
+	$lock=1;		# Remember that we hold the lock.
+        &unlink_tmpfiles($fn);
+    }
+    undef %randompick;
+    undef %hiddenurl;
+    undef %encurl;
+    $retfrid='';
+    my ($untiedhash,$untiedparmhash,$tiedhash,$tiedparmhash); # More state flags.
+
+    # if we got the lock, regenerate course regnerate empty files and tie them.
+
+    if ($lock) {
+        if (tie(%hash,'GDBM_File',"$fn.db",&GDBM_WRCREAT(),0640)) {
+            $tiedhash = 1;
+            if (tie(%parmhash,'GDBM_File',$fn.'_parms.db',&GDBM_WRCREAT(),0640)) {
+                $tiedparmhash = 1;
+                $gotstate = &build_tmp_hashes($uri,
+					      $fn,
+					      $short,
+					      \%cenv); # TODO: Need to provide requested user@dom
+                unless ($gotstate) {
+                    &Apache::lonnet::logthis('Failed to write statemap at first attempt '.$fn.' for '.$uri.'.</font>');
+                }
+                $untiedparmhash = untie(%parmhash);
+                unless ($untiedparmhash) {
+                    &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                        'Could not untie coursemap parmhash '.$fn.' for '.$uri.'.</font>');
+                }
+            }
+            $untiedhash = untie(%hash);
+            unless ($untiedhash) {
+                &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                    'Could not untie coursemap hash '.$fn.' for '.$uri.'.</font>');
+            }
+        }
+	flock(LOCKFILE,LOCK_UN); # RF: this is what I don't get unless there are other
+	                         # unlocked places the remainder happens..seems like if we
+                                 # just kept the lock here the rest of the code would have
+                                 # been much easier? 
+    }
+    unless ($lock && $tiedhash && $tiedparmhash) { 
+	# if we are here it is likely because we are already trying to 
+	# initialize the course in another child, busy wait trying to 
+	# tie the hashes for the next 90 seconds, if we succeed forward 
+	# them on to navmaps, if we fail, throw up the Could not init 
+	# course screen
+	#
+	# RF: I'm not seeing the case where the ties/unties can fail in a way
+	#     that can be remedied by this.  Since we owned the lock seems
+	#     Tie/untie failures are a result of something like a permissions problem instead?
+	#
+
+	#  In any vent, undo what we did manage to do above first:
+	if ($lock) {
+	    # Got the lock but not the DB files
+	    flock(LOCKFILE,LOCK_UN);
+            $lock = 0;
+	}
+        if ($tiedhash) {
+            unless($untiedhash) {
+	        untie(%hash);
+            }
+        }
+        if ($tiedparmhash) {
+            unless($untiedparmhash) {
+                untie(%parmhash);
+            }
+        }
+	# Log our failure:
+
+	&Apache::lonnet::logthis('<font color="blue">WARNING: '.
+				 "Could not tie coursemap $fn for $uri.</font>");
+        $tiedhash = '';
+        $tiedparmhash = '';
+	my $i=0;
+
+	# Keep on retrying the lock for 90 sec until we succeed.
+
+	while($i<90) {
+	    $i++;
+	    sleep(1);
+	    if (flock(LOCKFILE,LOCK_EX|LOCK_NB)) {
+
+		# Got the lock, tie the hashes...the assumption in this code is
+		# that some other worker thread has created the db files quite recently
+		# so no load is needed:
+
+                $lock = 1;
+		if (tie(%hash,'GDBM_File',"$fn.db",&GDBM_READER(),0640)) {
+                    $tiedhash = 1;
+		    if (tie(%parmhash,'GDBM_File',$fn.'_parms.db',&GDBM_READER(),0640)) {
+                        $tiedparmhash = 1;
+                        if (-e "$fn.state") {
+		            $retfurl='/adm/navmaps';
+
+			    # BUG BUG: Side effect!
+			    # Should conditionalize on something so that we can use this
+			    # to load maps for courses that are not current?
+			    #
+		            &Apache::lonnet::appenv({"request.course.id"  => $short,
+		   			             "request.course.fn"  => $fn,
+					             "request.course.uri" => $uri});
+		            $untiedhash = untie(%hash);
+		            $untiedparmhash = untie(%parmhash);
+                            $gotstate = 1;
+		            last;
+		        }
+                        $untiedparmhash = untie(%parmhash);
+	            }
+	            $untiedhash = untie(%hash);
+                }
+            }
+	}
+        if ($lock) {
+            flock(LOCKFILE,LOCK_UN);
+            $lock = 0;
+            if ($tiedparmhash) {
+                unless ($untiedparmhash) {
+                    &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                        'Could not untie coursemap parmhash '.$fn.' for '.$uri.'.</font>');
+                }
+            }
+            if ($tiedparmhash) {
+                unless ($untiedhash) {
+                    &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                        'Could not untie coursemap hash '.$fn.' for '.$uri.'.</font>');
+                }
+            }
+        }
+    }
+    # I think this branch of code is all about what happens if we just did the stuff above, 
+    # but found that the  state file did not exist...again if we'd just held the lock
+    # would that have made this logic simpler..as generating all the files would be
+    # an atomic operation with respect to the lock.
+    #
+    unless ($gotstate) {
+        $lock = 0;
+        &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                     'Could not read statemap '.$fn.' for '.$uri.'.</font>');
+        &unlink_tmpfiles($fn);
+        if (flock(LOCKFILE,LOCK_EX|LOCK_NB)) {
+            $lock=1;
+        }
+        undef %randompick;
+        undef %hiddenurl;
+        undef %encurl;
+        $retfrid='';
+	#
+	# Once more through the routine of tying and loading and so on.
+	#
+        if ($lock) {
+            if (tie(%hash,'GDBM_File',"$fn.db",&GDBM_WRCREAT(),0640)) {
+                if (tie(%parmhash,'GDBM_File',$fn.'_parms.db',&GDBM_WRCREAT(),0640)) {
+                    $gotstate = &build_tmp_hashes($uri,$fn,$short,\%cenv); # TODO: User dependent?
+                    unless ($gotstate) {
+                        &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                            'Failed to write statemap at second attempt '.$fn.' for '.$uri.'.</font>');
+                    }
+                    unless (untie(%parmhash)) {
+                        &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                            'Could not untie coursemap parmhash '.$fn.'.db for '.$uri.'.</font>');
+                    }
+                } else {
+                    &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                        'Could not tie coursemap '.$fn.'__parms.db for '.$uri.'.</font>');
+                }
+                unless (untie(%hash)) {
+                    &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                        'Could not untie coursemap hash '.$fn.'.db for '.$uri.'.</font>');
+                }
+            } else {
+               &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+                   'Could not tie coursemap '.$fn.'.db for '.$uri.'.</font>');
+            }
+            flock(LOCKFILE,LOCK_UN);
+            $lock = 0;
+        } else {
+	    # Failed to get the immediate lock.
+
+            &Apache::lonnet::logthis('<font color="blue">WARNING: '.
+            'Could not obtain lock to tie coursemap hash '.$fn.'.db for '.$uri.'.</font>');
+        }
+    }
+    close(LOCKFILE);
+    unless (($errtext eq '') || ($env{'request.course.uri'} =~ m{^/uploaded/})) {
+        &Apache::lonmsg::author_res_msg($env{'request.course.uri'},
+                                        $errtext); # TODO: User dependent?
+    }
+# ------------------------------------------------- Check for critical messages
+
+#  Depends on user must parameterize this as well..or separate as this is:
+#  more part of determining what someone sees on entering a course?
+
+    my @what=&Apache::lonnet::dump('critical',$env{'user.domain'},
+				   $env{'user.name'});
+    if ($what[0]) {
+	if (($what[0] ne 'con_lost') && ($what[0]!~/^error\:/)) {
+	    $retfurl='/adm/email?critical=display';
+        }
+    }
+    return ($retfurl,$errtext);
+}
+
+#
+#  This sub is called when the course hash and the param hash have been tied and
+#  their lock file is held.
+#  Parameters:
+#     $uri      -  URI that identifies the course.
+#     $fn       -  The base path/filename of the files that make up the context
+#                  being built.
+#     $short    -  Short course name.
+#     $cenvref  -  Reference to the course environment hash returned by 
+#                  Apache::lonnet::coursedescription
+#
+#  Assumptions:
+#    The globals
+#    %hash, %paramhash are tied to their gdbm files and we hold the lock on them.
+#
+sub build_tmp_hashes {
+    my ($uri,$fn,$short,$cenvref) = @_;
+    
+    unless(ref($cenvref) eq 'HASH') {
+        return;
+    }
+    my %cenv = %{$cenvref};
+    my $gotstate = 0;
+    %hash=();			# empty the global course and  parameter hashes.
     %parmhash=();
-    $errtext='';
+    $errtext='';		# No error messages yet.
     $pc=0;
+    &clear_mapalias_count();
     &processversionfile(%cenv);
     my $furi=&Apache::lonnet::clutter($uri);
+    #
+    #  the map staring points.
+    #
     $hash{'src_0.0'}=&versiontrack($furi);
     $hash{'title_0.0'}=&Apache::lonnet::metadata($uri,'title');
     $hash{'ids_'.$furi}='0.0';
     $hash{'is_map_0.0'}=1;
-    loadmap($uri);
+    &loadmap($uri,'0.0');
     if (defined($hash{'map_start_'.$uri})) {
+        &Apache::lonnet::appenv({"request.course.id"  => $short,
+                                 "request.course.fn"  => $fn,
+                                 "request.course.uri" => $uri});
+        $env{'request.course.id'}=$short;
         &traceroute('0',$hash{'map_start_'.$uri},'&');
         &accinit($uri,$short,$fn);
         &hiddenurls();
     }
+    $errtext .= &get_mapalias_errors();
 # ------------------------------------------------------- Put versions into src
-    foreach (keys %hash) {
-	if ($_=~/^src\_/) {
-	    $hash{$_}=&putinversion($hash{$_});
-	}
+    foreach my $key (keys(%hash)) {
+        if ($key=~/^src_/) {
+            $hash{$key}=&putinversion($hash{$key});
+        } elsif ($key =~ /^(map_(?:start|finish|pc)_)(.*)/) {
+            my ($type, $url) = ($1,$2);
+            my $value = $hash{$key};
+            $hash{$type.&putinversion($url)}=$value;
+        }
     }
 # ---------------------------------------------------------------- Encrypt URLs
-    foreach (keys %encurl) {
-	$hash{'src_'.$_}=&Apache::lonenc::encrypted($hash{'src_'.$_});
+    foreach my $id (keys(%encurl)) {
+#           $hash{'src_'.$id}=&Apache::lonenc::encrypted($hash{'src_'.$id});
+        $hash{'encrypted_'.$id}=1;
     }
 # ----------------------------------------------- Close hashes to finally store
 # --------------------------------- Routine must pass this point, no early outs
-    unless ((untie(%hash)) && (untie(%parmhash))) {
-      &Apache::lonnet::logthis("<font color=blue>WARNING: ".
-                       "Could not untie coursemap $fn for $uri.</font>"); 
+    $hash{'first_rid'}=$retfrid;
+    my ($mapid,$resid)=split(/\./,$retfrid);
+    $hash{'first_mapurl'}=$hash{'map_id_'.$mapid};
+    my $symb=&Apache::lonnet::encode_symb($hash{'map_id_'.$mapid},$resid,$hash{'src_'.$retfrid});
+    $retfurl=&add_get_param($hash{'src_'.$retfrid},{ 'symb' => $symb });
+    if ($hash{'encrypted_'.$retfrid}) {
+        $retfurl=&Apache::lonenc::encrypted($retfurl,(&Apache::lonnet::allowed('adv') ne 'F'));
     }
+    $hash{'first_url'}=$retfurl;
 # ---------------------------------------------------- Store away initial state
     {
-     my $cfh;
-     if ($cfh=Apache::File->new(">$fn.state")) {
-        print $cfh join("\n",@cond);
-     } else {
-      &Apache::lonnet::logthis("<font color=blue>WARNING: ".
-                       "Could not write statemap $fn for $uri.</font>"); 
-     }
-    }  
-   } else {
-      &Apache::lonnet::logthis("<font color=blue>WARNING: ".
-                       "Could not tie coursemap $fn for $uri.</font>"); 
-   }
-   &Apache::lonmsg::author_res_msg($ENV{'request.course.uri'},$errtext);
-# ------------------------------------------------- Check for critical messages
+        my $cfh;
+        if (open($cfh,">$fn.state")) {
+            print $cfh join("\n",@cond);
+            $gotstate = 1;
+        } else {
+            &Apache::lonnet::logthis("<font color=blue>WARNING: ".
+                                     "Could not write statemap $fn for $uri.</font>");
+        }
+    }
+    return $gotstate;
+}
 
-    my @what=&Apache::lonnet::dump('critical',$ENV{'user.domain'},
-                                              $ENV{'user.name'});
-    if ($what[0]) {
-	if (($what[0] ne 'con_lost') && ($what[0]!~/^error\:/)) {
-	    $retfurl='/adm/email?critical=display';
+sub unlink_tmpfiles {
+    my ($fn) = @_;
+    my $file_dir = dirname($fn);
+
+    if ($fn eq LONCAPA::tempdir()) {
+        my @files = qw (.db _symb.db .state _parms.db);
+        foreach my $file (@files) {
+            if (-e $fn.$file) {
+                unless (unlink($fn.$file)) {
+                    &Apache::lonnet::logthis("<font color=blue>WARNING: ".
+                                 "Could not unlink ".$fn.$file."</font>");
+                }
+            }
         }
     }
-   return ($retfurl,$errtext);
+    return;
 }
 
 # ------------------------------------------------------- Evaluate state string
 
 sub evalstate {
-
-    my $fn=$ENV{'request.course.fn'}.'.state';
-    my $state='2';
+    my $fn=$env{'request.course.fn'}.'.state';
+    my $state='';
     if (-e $fn) {
-       my @conditions=();
-       {
-        my $fh=Apache::File->new($fn);
-        @conditions=<$fh>;
-       }  
-       my $safeeval = new Safe;
-       my $safehole = new Safe::Hole;
-       $safeeval->permit("entereval");
-       $safeeval->permit(":base_math");
-       $safeeval->deny(":base_io");
-       $safehole->wrap(\&Apache::lonnet::EXT,$safeeval,'&EXT');
-       foreach (@conditions) {
-	   my $line=$_;
-           chomp($line);
-	   my ($condition,$weight)=split(/\:/,$_);
-           if ($safeeval->reval($condition)) {
-	       if ($weight eq 'force') {
-		   $state.='3';
-               } else {
-                   $state.='2';
-               }
-           } else {
-               if ($weight eq 'stop') {
-		   $state.='0';
-               } else {
-                   $state.='1';
-               }
-           }
-       }
+	my @conditions=();
+	{
+	    open(my $fh,"<$fn");
+	    @conditions=<$fh>;
+            close($fh);
+	}  
+	my $safeeval = new Safe;
+	my $safehole = new Safe::Hole;
+	$safeeval->permit("entereval");
+	$safeeval->permit(":base_math");
+	$safeeval->deny(":base_io");
+	$safehole->wrap(\&Apache::lonnet::EXT,$safeeval,'&EXT');
+	foreach my $line (@conditions) {
+	    chomp($line);
+	    my ($condition,$weight)=split(/\:/,$line);
+	    if ($safeeval->reval($condition)) {
+		if ($weight eq 'force') {
+		    $state.='3';
+		} else {
+		    $state.='2';
+		}
+	    } else {
+		if ($weight eq 'stop') {
+		    $state.='0';
+		} else {
+		    $state.='1';
+		}
+	    }
+	}
     }
-    &Apache::lonnet::appenv('user.state.'.$ENV{'request.course.id'} => $state);
+    &Apache::lonnet::appenv({'user.state.'.$env{'request.course.id'} => $state});
     return $state;
 }
 
+#  This block seems to have code to manage/detect doubly defined
+#  aliases in maps.
+
+{
+    my %mapalias_cache;
+    sub count_mapalias {
+	my ($value,$resid) = @_;
+ 	push(@{ $mapalias_cache{$value} }, $resid);
+    }
+
+    sub get_mapalias_errors {
+	my $error_text;
+	foreach my $mapalias (sort(keys(%mapalias_cache))) {
+	    next if (scalar(@{ $mapalias_cache{$mapalias} } ) == 1);
+	    my $count;
+	    my $which =
+		join('</li><li>', 
+		     map {
+			 my $id = $_;
+			 if (exists($hash{'src_'.$id})) {
+			     $count++;
+			 }
+			 my ($mapid) = split(/\./,$id);
+                         &mt('Resource "[_1]" <br /> in Map "[_2]"',
+			     $hash{'title_'.$id},
+			     $hash{'title_'.$hash{'ids_'.$hash{'map_id_'.$mapid}}});
+		     } (@{ $mapalias_cache{$mapalias} }));
+	    next if ($count < 2);
+	    $error_text .= '<div class="LC_error">'.
+		&mt('Error: Found the mapalias "[_1]" defined multiple times.',
+		    $mapalias).
+		'</div><ul><li>'.$which.'</li></ul>';
+	}
+	&clear_mapalias_count();
+	return $error_text;
+    }
+    sub clear_mapalias_count {
+	undef(%mapalias_cache);
+    }
+}
 1;
 __END__
 
@@ -682,37 +1231,33 @@ of course for user.
 This is part of the LearningOnline Network with CAPA project
 described at http://www.lon-capa.org.
 
-=head1 HANDLER SUBROUTINE
-
-There is no handler subroutine.
-
-=head1 OTHER SUBROUTINES
+=head1 SUBROUTINES
 
-=over 4
+=over
 
-=item *
+=item loadmap()
 
-loadmap() : Loads map from disk
+Loads map from disk
 
-=item *
+=item simplify()
 
-simplify() : Simplify expression
+Simplify expression
 
-=item *
+=item traceroute()
 
-traceroute() : Build condition hash
+Build condition hash
 
-=item *
+=item accinit()
 
-accinit() : Cascading conditions, quick access, parameters
+Cascading conditions, quick access, parameters
 
-=item *
+=item readmap()
 
-readmap() : Read map and all submaps
+Read map and all submaps
 
-=item *
+=item evalstate()
 
-evalstate() : Evaluate state string
+Evaluate state string
 
 =back