[crypt.pl] refactor - private apply method

This separates out the state change into a single private method.
(Or several multimethods when Rakudo does private multimethods.)
Interestingly, the condition for achievement unlocked now changed
since we're not applying the events until they have all been
constructed.

crypt.pl

@@ -91,19 +91,34 @@
                 );
             }
         }
-        @target_rod.push( @source_rod.pop );
         my $size = $moved_disk.words[0];
         my @events = DiskMoved.new(:$size, :$source, :$target);
-        if %!state<right> == @disks && $!achievement eq 'locked' {
-            $!achievement = 'unlocked';
+        if %!state<right> == @disks-1
+           && $target eq 'right'
+           && $!achievement eq 'locked' {
             @events.push(AchievementUnlocked.new);
         }
         if $size eq 'small' && $!achievement eq 'unlocked' {
-            $!achievement = 'locked';
             @events.push(AchievementLocked.new);
         }
+        self!apply($_) for @events;
         return @events;
     }
+
+    # RAKUDO: private multimethods NYI
+    method !apply(Event $_) {
+        when DiskMoved {
+            my @source_rod := %!state{.source};
+            my @target_rod := %!state{.target};
+            @target_rod.push( @source_rod.pop );
+        }
+        when AchievementUnlocked {
+            $!achievement = 'unlocked';
+        }
+        when AchievementLocked {
+            $!achievement = 'locked';
+        }
+    }
 }
 
 sub throws_exception(&code, $ex_type, $message, &followup?) {