use strict;
use List::Util qw(sum);

# Represent the matchables with upper and lower case letters.
# Double the strings so rotations are all represented.
my @tiles = (
   "",         # filler
   "AbDCAbDC", # 1  Top of A, bottom of b, top of D, top of C
   "ABdcABdc", # 2
   "adcbadcb", # 3
   "ABDcABDc", # 4
   "CDbaCDba", # 5
   "AcdBAcdB", # 6
   "DdCBDdCB", # 7
   "AacDAacD", # 8
   "ABcbABcb", # 9
);
my $TOP = 0;
my $RIGHT = 1;
my $BOTTOM = 2;
my $LEFT = 3;

# rotation index
my (@rot, @pick, @tries, @passes, $rotation);
$rot[0] = 0;

sub get_target {
   my ($oldpos, $oldside) = @_;
   # match single constraint
   my $target = substr($tiles[$pick[$oldpos]], $rot[$oldpos] + $oldsid
+e, 1);
   $target =~ tr/A-Da-d/a-dA-D/;
   return $target;
}

sub get_target2 {
   my ($oldpos, $oldside, $oldpos2, $oldside2) = @_;
   # Two contraints in a row, clockwise.
   my $target1 = substr($tiles[$pick[$oldpos]], $rot[$oldpos] + $oldsi
+de, 1);
   my $target2 = substr($tiles[$pick[$oldpos2]], $rot[$oldpos2] + $old
+side2, 1);
   my $target = $target1 . $target2;
   $target =~ tr/A-Da-d/a-dA-D/;
   return $target;
}

sub fit_tile {
   my ($mypos, $tile, $side, $target) = @_;

   $tries[$mypos]++;

   my $ind = index($tiles[$tile], $target);
   return -1 if ($ind < 0);

   $passes[$mypos]++;

   # rotation to have letters match
   my $rotation = ($ind - $side) % 4;

   $pick[$mypos] = $tile;
   $rot[$mypos] = $rotation;
   return $rotation;
}

sub print_solution {
   print 0+$pick[8],":",0+$rot[8]," ",$pick[1],":",$rot[1], " ", $pick
+[2],":",$rot[2],"\n";
   print $pick[7],":",$rot[7]," ",$pick[0],":",$rot[0], " ", $pick[3],
+":",$rot[3],"\n";
   print $pick[6],":",$rot[6]," ",$pick[5],":",$rot[5], " ", $pick[4],
+":",$rot[4],"\n";
   print "\n";
   my $i;
   for $i (0..8) {
      print 0+$tries[$i]," tries, ",0+$passes[$i]," passes for level "
+,$i,"\n";
   }
   print sum(@tries)," total tries\n";
   print sum(@passes)," total passes\n";
}

# Note: the tiles that are not yet assigned
my ($un0, $un1, $un2, $un3, $un4, $un5, $un6, $un7, $un8);
# The current tile number.
my ($p0, $p1, $p2, $p3, $p4, $p5, $p6, $p7, $p8);
# What the tile has to match.
my ($t1, $t2, $t3, $t4, $t5, $t6, $t7, $t8);

# Try to fill in the tiles in the following order:
#    8  1  2
#    7  0  3
#    6  5  4

$un0 = "123456789";
MAJOR:
foreach $p0 (split(//,$un0)) {
   $pick[0] = $p0;
   $tries[0]++;
   $passes[0]++;
   my $un1 = $un0;
   $un1 =~ s/$p0//;
   $t1 = get_target(0, $TOP);  # top of inner tile
   foreach $p1 (split(//,$un1)) {
      $rotation = fit_tile(1, $p1, $BOTTOM, $t1);
      next if ($rotation < 0);
      $un2 = $un1;
      $un2 =~ s/$p1//;
      $t2 = get_target(1, $RIGHT); # side of tile 1
      foreach $p2 (split(//,$un2)) {
         $rotation = fit_tile(2, $p2, $LEFT, $t2);
         next if ($rotation < 0);
         $un3 = $un2;
         $un3 =~ s/$p2//;
         $t3 = get_target2(0, $RIGHT, 2, $BOTTOM); # sides of 0, 2
         foreach $p3 (split(//,$un3)) {
            $rotation = fit_tile(3, $p3, $LEFT, $t3);
            next if ($rotation < 0);
            $un4 = $un3;
            $un4 =~ s/$p3//;
            $t4 = get_target(3, $BOTTOM);
            foreach $p4 (split(//,$un4)) {
               $rotation = fit_tile(4, $p4, $TOP, $t4);
               next if ($rotation < 0);
               $un5 = $un4;
               $un5 =~ s/$p4//;
               $t5 = get_target2(0, $BOTTOM, 4, $LEFT);
               foreach $p5 (split(//,$un5)) {
                  $rotation = fit_tile(5, $p5, $TOP, $t5);
                  next if ($rotation < 0);
                  $un6 = $un5;
                  $un6 =~ s/$p5//;
                  $t6 = get_target(5, $LEFT);
                  foreach $p6 (split(//,$un6)) {
                     $rotation = fit_tile(6, $p6, $RIGHT, $t6);
                     next if ($rotation < 0);
                     $un7 = $un6;
                     $un7 =~ s/$p6//;
                     $t7 = get_target2(0, $LEFT, 6, $TOP);
                     foreach $p7 (split(//,$un7)) {
                        $rotation = fit_tile(7, $p7, $RIGHT, $t7);
                        next if ($rotation < 0);
                        $un8 = $un7;
                        $un8 =~ s/$p7//;
                        $t8 = get_target2(1, $LEFT, 7, $TOP);
                        $p8 = $un8;
                        $rotation = fit_tile(8, $p8, $RIGHT, $t8);
                        next if ($rotation < 0);
                        print_solution();
                        last MAJOR;
                     } # p7, p8
                  } # p6
               } # p5
            } # p4
         } # p3
      } # p2
   } # p1
} # p0

print "Done\n";
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