Add storage backend manager class

src/Core/StorageManager.php

@@ -0,0 +1,102 @@
+<?php
+
+namespace Friendica\Core;
+
+use Friendica\Core\Config;
+
+
+
+/**
+ * @brief Manage storage backends
+ *
+ * Core code uses this class to get and set current storage backend class.
+ * Addons use this class to register and unregister additional backends.
+ */
+class StorageManager
+{
+	private static $default_storages = [
+		'Filesystem' => \Friendica\Model\Storage\Filesystem::class,
+		'Database' => \Friendica\Model\Storage\Database::class,
+	];
+
+	private static $storages = [];
+
+	private static function setup()
+	{
+		if (count(self::$storages)==0) {
+			self::$storage = Config::get('storage', 'backends', self::$default_storages);
+		}
+	}
+
+	/**
+	 * @brief Return current storage backend class
+	 * @return string
+	 */
+	public static function getBackend()
+	{
+		return Config::get('storage', 'class', '');
+	}
+
+	/**
+	 * @brief Return storage backend class by registered name
+	 *
+	 * @param string  $name  Backend name
+	 * @return string Empty if no backend registered at $name exists
+	 */
+	public static function getByName($name)
+	{
+		self::setup();
+		return defaults(self::$storages, $name, '');
+	}
+
+	/**
+	 * @brief Set current storage backend class
+	 *
+	 * @param string  $class  Backend class name
+	 */
+	public static function setBackend($class)
+	{
+		/// @todo Check that $class implements IStorage
+		Config::set('storage', 'class', $class);
+	}
+
+	/**
+	 * @brief Get registered backends
+	 *
+	 * @return array
+	 */
+	public static function listBackends()
+	{
+		self::setup();
+		return self::$backends;
+	}
+
+
+
+	/**
+	 * @brief Register a storage backend class
+	 *
+	 * @param string  $name   User readable backend name
+	 * @param string  $class  Backend class name
+	 */
+	public static function register($name, $class)
+	{
+		/// @todo Check that $class implements IStorage
+		self::setup();
+		self::$storages[$name] = $class;
+		Config::set('storage', 'backends', self::$storages);
+	}
+
+
+	/**
+	 * @brief Unregister a storage backend class
+	 *
+	 * @param string  $name   User readable backend name
+	 */
+	public static function unregister($class)
+	{
+		self::setup();
+		unset(self::$storages[$name]);
+		Config::set('storage', 'backends', self::$storages);
+	}
+}

src/Model/Photo.php

@@ -11,6 +11,7 @@ use Friendica\Core\Cache;
 use Friendica\Core\Config;
 use Friendica\Core\L10n;
 use Friendica\Core\System;
+use Friendica\Core\StorageManager;
 use Friendica\Database\DBA;
 use Friendica\Database\DBStructure;
 use Friendica\Object\Image;
@@ -263,7 +264,7 @@ class Photo extends BaseObject
 			$backend_ref = (string)$existing_photo["backend-ref"];
 			$backend_class = (string)$existing_photo["backend-class"];
 		} else {
-			$backend_class = Config::get("storage", "class", "");
+			$backend_class = StorageManager::getBackend();
 		}
 		if ($backend_class === "") {
 			$data = $Image->asString();