Extract a class to hold / determine paths

src/Foundation/Paths.php

@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Foundation;
+
+use InvalidArgumentException;
+
+/**
+ * @property-read string base
+ * @property-read string public
+ * @property-read string storage
+ * @property-read string vendor
+ */
+class Paths
+{
+    private $paths;
+
+    public function __construct(array $paths)
+    {
+        if (! isset($paths['base'], $paths['public'], $paths['storage'])) {
+            throw new InvalidArgumentException(
+                'Paths array requires keys base, public and storage'
+            );
+        }
+
+        $this->paths = array_map(function ($path) {
+            return rtrim($path, '\/');
+        }, $paths);
+
+        // Assume a standard Composer directory structure unless specified
+        $this->paths['vendor'] = $this->vendor ?? $this->base.DIRECTORY_SEPARATOR.'vendor';
+    }
+
+    public function __get($name): ?string
+    {
+        return $this->paths[$name] ?? null;
+    }
+}