From bc438288c5104218b120ab5f064d465d70bf3325 Mon Sep 17 00:00:00 2001
From: John McQuah <jquah@mx.sdf.org>
Date: Wed, 24 May 2023 08:57:02 -0400
Subject: [PATCH] prt-auf: use Fun's algorithm instead of Kahn's

---
 scripts/prt-auf | 52 +++++++++++++++++++++++--------------------------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/scripts/prt-auf b/scripts/prt-auf
index 27d9f62..042a1f3 100755
--- a/scripts/prt-auf
+++ b/scripts/prt-auf
@@ -672,26 +672,37 @@ sub port_diff { # find differences between the pkgdb and the repo
 
 sub deporder { # returns a sorted list of packages required.
   my $type=shift; my @seeds=@_; our @treewalk=(); our %missing;
-  our %numPred = map { $_ => 0 } @seeds; our %children; my @result;
+  our %level = map { $_ => 1 } @seeds; our $maxLevel=1; my @result;
 
   # determine the minimal set of targets needed to satisfy all dependencies
-  foreach my $t (@seeds) { recurse_deptree(0,$t); }
+  foreach my $t (@seeds) { recurse_deptree(0,1,$t); }
 
   sub recurse_deptree {
-      my $greedy=shift; my $s=shift; my %curdeps;
+      my $greedy=shift; my $thisLevel=shift; my $s=shift; my %curdeps;
 
       # detect any dependencies that have been dropped from the repositories
-      if (! $V_REPO{$s}) { $missing{$s}=1; undef $numPred{$s}; return; }
+      if (! $V_REPO{$s}) { $missing{$s}=1; delete $level{$s}; return; }
 
       # cycle detection
-      ( grep /^$s$/, @treewalk ) ? return : push(@treewalk, $s);
+      if (grep /^$s$/, @treewalk) {
+	      return if ($greedy == 1);
+	      print "Dependency cycle found: ";
+	      foreach (@treewalk) { print "$_ => "; }
+	      print "$s\n";
+      } else { push(@treewalk, $s); }
+
+      # update the hash table and the height of the tree
+      if ( (! $level{$s}) or ($level{$s} < $thisLevel) ) {
+	      $level{$s} = $thisLevel;
+      } 
+      if ( $maxLevel < $thisLevel ) { $maxLevel = $thisLevel; }
 
       %curdeps = map { $_ => $greedy } split /[ ,]/, $DEPENDS{$s};
 
       # if the user toggles --softdeps, consider the optional dependencies 
       # that are already installed or are given on the command line
       if ($odepends{soft} == 1)  {
-           foreach (grep { ($V_INST{$_}) or ($numPred{$_}) } 
+           foreach (grep { ($V_INST{$_}) or ($level{$_}) } 
 		   split /[ ,]/, $SOFTDEPS{$s}) { 
    		$curdeps{$_} = 1;
 	   }
@@ -700,36 +711,21 @@ sub deporder { # returns a sorted list of packages required.
       foreach my $sd (keys %curdeps) {
 	      my $subit = who_aliased_to($sd);
 	      if ($subit) {
-		      $children{$s} .= " $subit ";
-		      $numPred{$subit} += 1 unless ($greedy == 1);
-		      recurse_deptree($curdeps{$sd},$subit);
+		      recurse_deptree($curdeps{$sd},$thisLevel+1,$subit);
 	      } else {
-		      $children{$s} .= " $sd ";
-		      $numPred{$sd} += 1 unless ($greedy == 1);
-		      recurse_deptree($curdeps{$sd},$sd);
+		      recurse_deptree($curdeps{$sd},$thisLevel+1,$sd);
 	      }
       }
       pop (@treewalk);
 
    } # proceed with the topological sort
-   # initialize a queue of nodes with in-degree zero (nothing depends on them)
-   my @indZero = grep { ($numPred{$_} == 0) } keys %numPred; 
-
-   # move each node from the queue to the sorted list, and reduce by 1 the
-   # in-degree of its dependencies (Kahn 1962)
-   while (my $q = shift @indZero) {
-	   push(@result, $q);
-	   next if (! $children{$q});
-	   foreach my $s (split / /, $children{$q}) {
-		   $numPred{$s} -= 1;
-		   push(@indZero,$s) if ($numPred{$s} == 0);
-	   }
+   # gather up all the targets farthest from the root of the tree,
+   # then reduce by 1 the level at which to search.
+   while ($maxLevel >= 1) {
+        push(@result, grep { ($level{$_} == $maxLevel) } keys %level);
+   	$maxLevel -= 1;
    }
 
-   # the resulting list is backwards (dependencies come after the packages they
-   # support), and must be reversed.
-   @result = reverse @result;
-
    if ((keys %missing > 0) and ($type ne "quickdep")) { push (@result, "MISSING", sort(keys %missing)); }
    return @result;
 }