feat: harden xml parsing to avoid uncaught errors

src/BusProNet/XmlParser/DocumentsParser.php

@@ -44,15 +44,29 @@ class DocumentsParser
 
     private function decode(Crawler $node): string
     {
-        [, $pdfData] = explode(',', $node->text());
+        if (0 === $node->count()) {
+            throw new \InvalidArgumentException('Missing PDF node in document response.');
+        }
+
+        $parts = explode(',', $node->text(), 2);
+        if (2 !== count($parts)) {
+            throw new \InvalidArgumentException('Invalid PDF payload in document response.');
+        }
+
+        [, $pdfData] = $parts;
 
         return base64_decode($pdfData);
     }
 
     private function getFileInfo(Crawler $node): array
     {
-        $pdfData = $this->decode($node->filterXPath('//pdf'));
-        $filename = $node->filterXPath('//datei')->text();
+        $pdfData = $this->decode($node->filterXPath('.//pdf'));
+        $filenameNode = $node->filterXPath('.//datei');
+        if (0 === $filenameNode->count()) {
+            throw new \InvalidArgumentException('Missing filename node in document response.');
+        }
+
+        $filename = $filenameNode->text();
 
         return [$filename, $pdfData];
     }