Cache the results of getAssetFiles

Fix the disk backlog during scoreboard pictures rendering.

Signed-off-by: cubercsl <2014cais01@gmail.com>

Co-authored-by: Soha Jin <soha@jin.sh>

Author: cubercsl

webapp/src/Service/DOMJudgeService.php

@@ -1340,16 +1340,24 @@ public function apiRelativeUrl(string $route, array $params = []): string
         return substr($route, strlen($apiRootRoute) + $offset);
     }
 
+
+    /** @var array<string, string[]> */
+    private static array $assetFiles = [];
+
     /**
      * Get asset files in the given directory with the given extension
      *
      * @return string[]
      */
     public function getAssetFiles(string $path): array
     {
+        if (isset(self::$assetFiles[$path])) {
+            return self::$assetFiles[$path];
+        }
+
         $customDir = sprintf('%s/public/%s', $this->params->get('kernel.project_dir'), $path);
         if (!is_dir($customDir)) {
-            return [];
+            return self::$assetFiles[$path] = [];
         }
 
         $results = [];
@@ -1361,7 +1369,7 @@ public function getAssetFiles(string $path): array
             }
         }
 
-        return $results;
+        return self::$assetFiles[$path] = $results;
     }
 
     /**