Markdown: Escape some elements prior to sending them through Markdown

markdown/markdown.php

@@ -49,5 +49,25 @@ function markdown_post_local_start(App $a, &$request) {
 		return;
 	}
 
-	$request['body'] = Markdown::toBBCode($request['body']);
+	// Elements that shouldn't be parsed
+	$elements = ['code', 'noparse', 'nobb', 'pre'];
+	foreach ($elements as $element) {
+		$request['body'] = preg_replace_callback("/\[" . $element . "\](.*?)\[\/" . $element . "\]/ism",
+					function ($match)  use ($element) {
+						return '[base64' . $element . ']' . base64_encode($match[1]) . '[/base64' . $element . ']';
+					},
+					$request['body']
+				);
+	}
+
+	$request['body'] = Markdown::toBBCode($request['body']);
+
+	foreach ($elements as $element) {
+		$request['body'] = preg_replace_callback("/\[base64" . $element . "\](.*?)\[\/base64" . $element . "\]/ism",
+					function ($match)  use ($element) {
+						return '[' . $element . ']' . base64_decode($match[1]) . '[/' . $element . ']';
+					},
+					$request['body']
+				);
+	}
 }