fix: Remove enums for compatibility with PHP 8

Author: jose-bittacora

src/DiagramElement/RelationsFilter.php

@@ -36,12 +36,12 @@ public function filterRelations(array $relation_expressions): array
         }
 
         if ([] !== $fromClasses) {
-            $output = array_merge($output, $this->filterClasses($fromClasses, DependenciesDirection::OUT));
+            $output = array_merge($output, $this->filterClasses($fromClasses, 'out'));
             $this->removeUnlinked = true;
         }
 
         if ([] !== $toClasses) {
-            $output = array_merge($output, $this->filterClasses($toClasses, DependenciesDirection::IN));
+            $output = array_merge($output, $this->filterClasses($toClasses, 'in'));
             $this->removeUnlinked = true;
         }
 
@@ -62,10 +62,9 @@ public function addRemoveUnlinkedDirective(array $relation_expressions): array
 
     /**
      * @param array<string> $filteredClasses
-     * @param DependenciesDirection $direction
      * @return array<string>
      */
-    public function filterClasses(array $filteredClasses, DependenciesDirection $direction): array
+    public function filterClasses(array $filteredClasses, string $direction): array
     {
         $currentDepth = 0;
         /** @var array<string> $matches */
@@ -74,7 +73,7 @@ public function filterClasses(array $filteredClasses, DependenciesDirection $dir
             $oldMatches = $matches;
             foreach ($matches as $match) {
                 $parts = explode(' ', trim($match));
-                $filteredClasses[] = $direction === DependenciesDirection::OUT ?
+                $filteredClasses[] = $direction === 'out' ?
                     end($parts) :
                     array_shift($parts)
                 ;
@@ -96,12 +95,12 @@ public function filterClasses(array $filteredClasses, DependenciesDirection $dir
         return $matches;
     }
 
-    function getFilteringRegex(string $filteredClass, DependenciesDirection $direction): string
+    function getFilteringRegex(string $filteredClass, string $direction): string
     {
         $filteredClass = str_replace('*', '.*?', $filteredClass);
         return match ($direction) {
-            DependenciesDirection::IN => "/.*?> ({$filteredClass}$|[\w_]+{$filteredClass}$)/",
-            DependenciesDirection::OUT => "/^({$filteredClass}|^[\w_]+{$filteredClass}) .*?>.*?/",
+            'in' => "/.*?> ({$filteredClass}$|[\w_]+{$filteredClass}$)/",
+            'out' => "/^({$filteredClass}|^[\w_]+{$filteredClass}) .*?>.*?/",
         };
     }
 }