feat: Implement parsing of PANDOC-style YAML metadata

src/Controller/MainController.php

@@ -9,6 +9,7 @@ use Symfony\Component\Finder\Finder;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Process\Process;
 use Symfony\Component\Routing\Attribute\Route;
+use Symfony\Component\Yaml\Yaml;
 
 final class MainController extends AbstractController
 {
@@ -46,6 +47,10 @@ final class MainController extends AbstractController
         $fs = new Filesystem();
         $contents = $fs->exists($fullPath) ? $fs->readFile($fullPath) : null;
 
+        [
+            'data' => $metadata,
+            'text' => $text
+        ] = $this->extractMetadata($contents);
 
         // -------------------------------------------------- Get data tree ---
 
@@ -74,9 +79,37 @@ final class MainController extends AbstractController
 
         return $this->render('main/index.html.twig', [
             'path'     => $path,
-            'contents' => $contents,
+            'contents' => $text,
+            'metadata' => $metadata,
             'tree'     => $tree,
             'version'  => (new Process(['git', '-C', $gitDir, 'log', '-1', '--oneline']))->mustRun()->getOutput(),
         ]);
     }
+
+    /**
+     * Parses all YAML metadata blocks in a given string and returns the text
+     * without such blocks.
+     */
+    private function extractMetadata(?string $text): array
+    {
+        if ($text === null) return ['data' => null, 'text' => null];
+
+        $start = strpos($text, "---\n");
+        $end = strpos($text, "...\n", $start) ?: strpos($text, "---\n", $start + 4);
+
+        // No more moteadata, return as is. Recursion stop condition
+        if ($start === false or $end === false) {
+            return ['text' => $text, 'data' => []];
+        }
+
+        $yaml = Yaml::parse(substr($text, $start + 4, $end - $start - 4));
+        $rest = substr($text, 0, $start) . substr($text, $end + 4);
+
+        // Recurse until there's no more metadata blocks, overwriting as we go
+        $nextIteration = $this->extractMetadata($rest);
+        return [
+            'data' => $nextIteration['data'] + $yaml,
+            'text' => $nextIteration['text'],
+        ];
+    }
 }