Add checks & realpath() usage

- New util class "FileSystem"
- Add check in admin summary too

src/Util/FileSystem.php

@@ -0,0 +1,64 @@
+<?php
+
+namespace Friendica\Util;
+
+final class FileSystem
+{
+	/**
+	 * @var string a error message
+	 */
+	private $errorMessage;
+
+	public function createDir(string $file)
+	{
+		$dirname = null;
+		$pos = strpos($file, '://');
+
+		if (!$pos) {
+			$dirname = realpath(dirname($file));
+		}
+
+		if (substr($file, 0, 7) === 'file://') {
+			$dirname = realpath(dirname(substr($file, 7)));
+		}
+
+		if (isset($dirname) && !is_dir($dirname)) {
+			set_error_handler([$this, 'customErrorHandler']);
+			$status = mkdir($dirname, 0777, true);
+			restore_error_handler();
+
+			if (!$status && !is_dir($dirname)) {
+				throw new \UnexpectedValueException(sprintf('Directory "%s" cannot get created: ' . $this->errorMessage, $dirname));
+			}
+
+			return $dirname;
+		} elseif (isset($dirname) && is_dir($dirname)) {
+			return $dirname;
+		} else {
+			return '';
+		}
+	}
+
+	public function createStream(string $url)
+	{
+		$directory = $this->createDir($url);
+		set_error_handler([$this, 'customErrorHandler']);
+		if (!empty($directory)) {
+			$url = $directory . DIRECTORY_SEPARATOR . pathinfo($url, PATHINFO_BASENAME);
+		}
+
+		$stream = fopen($url, 'ab');
+		restore_error_handler();
+
+		if (!is_resource($stream)) {
+			throw new \UnexpectedValueException(sprintf('The stream or file "%s" could not be opened: ' . $this->errorMessage, $url));
+		}
+
+		return $stream;
+	}
+
+	private function customErrorHandler($code, $msg)
+	{
+		$this->errorMessage = preg_replace('{^(fopen|mkdir)\(.*?\): }', '', $msg);
+	}
+}