Merge pull request #16682 from nextcloud/enh/12790/workflow-backend

workflow overhaul

18 files changed, 629 insertions, 48 deletions

diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 045c5ef7475..48be2fc03fb 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -438,9 +438,17 @@ return array(
     'OCP\\User\\Backend\\ISetDisplayNameBackend' => $baseDir . '/lib/public/User/Backend/ISetDisplayNameBackend.php',
     'OCP\\User\\Backend\\ISetPasswordBackend' => $baseDir . '/lib/public/User/Backend/ISetPasswordBackend.php',
     'OCP\\Util' => $baseDir . '/lib/public/Util.php',
+    'OCP\\WorkflowEngine\\GenericEntityEvent' => $baseDir . '/lib/public/WorkflowEngine/GenericEntityEvent.php',
     'OCP\\WorkflowEngine\\ICheck' => $baseDir . '/lib/public/WorkflowEngine/ICheck.php',
+    'OCP\\WorkflowEngine\\IComplexOperation' => $baseDir . '/lib/public/WorkflowEngine/IComplexOperation.php',
+    'OCP\\WorkflowEngine\\IEntity' => $baseDir . '/lib/public/WorkflowEngine/IEntity.php',
+    'OCP\\WorkflowEngine\\IEntityCheck' => $baseDir . '/lib/public/WorkflowEngine/IEntityCheck.php',
+    'OCP\\WorkflowEngine\\IEntityEvent' => $baseDir . '/lib/public/WorkflowEngine/IEntityEvent.php',
+    'OCP\\WorkflowEngine\\IFileCheck' => $baseDir . '/lib/public/WorkflowEngine/IFileCheck.php',
     'OCP\\WorkflowEngine\\IManager' => $baseDir . '/lib/public/WorkflowEngine/IManager.php',
     'OCP\\WorkflowEngine\\IOperation' => $baseDir . '/lib/public/WorkflowEngine/IOperation.php',
+    'OCP\\WorkflowEngine\\IRuleMatcher' => $baseDir . '/lib/public/WorkflowEngine/IRuleMatcher.php',
+    'OCP\\WorkflowEngine\\ISpecificOperation' => $baseDir . '/lib/public/WorkflowEngine/ISpecificOperation.php',
     'OC\\Accounts\\Account' => $baseDir . '/lib/private/Accounts/Account.php',
     'OC\\Accounts\\AccountManager' => $baseDir . '/lib/private/Accounts/AccountManager.php',
     'OC\\Accounts\\AccountProperty' => $baseDir . '/lib/private/Accounts/AccountProperty.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 600491e600e..0a5a1dc2fb6 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -472,9 +472,17 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OCP\\User\\Backend\\ISetDisplayNameBackend' => __DIR__ . '/../../..' . '/lib/public/User/Backend/ISetDisplayNameBackend.php',
         'OCP\\User\\Backend\\ISetPasswordBackend' => __DIR__ . '/../../..' . '/lib/public/User/Backend/ISetPasswordBackend.php',
         'OCP\\Util' => __DIR__ . '/../../..' . '/lib/public/Util.php',
+        'OCP\\WorkflowEngine\\GenericEntityEvent' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/GenericEntityEvent.php',
         'OCP\\WorkflowEngine\\ICheck' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/ICheck.php',
+        'OCP\\WorkflowEngine\\IComplexOperation' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IComplexOperation.php',
+        'OCP\\WorkflowEngine\\IEntity' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IEntity.php',
+        'OCP\\WorkflowEngine\\IEntityCheck' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IEntityCheck.php',
+        'OCP\\WorkflowEngine\\IEntityEvent' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IEntityEvent.php',
+        'OCP\\WorkflowEngine\\IFileCheck' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IFileCheck.php',
         'OCP\\WorkflowEngine\\IManager' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IManager.php',
         'OCP\\WorkflowEngine\\IOperation' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IOperation.php',
+        'OCP\\WorkflowEngine\\IRuleMatcher' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/IRuleMatcher.php',
+        'OCP\\WorkflowEngine\\ISpecificOperation' => __DIR__ . '/../../..' . '/lib/public/WorkflowEngine/ISpecificOperation.php',
         'OC\\Accounts\\Account' => __DIR__ . '/../../..' . '/lib/private/Accounts/Account.php',
         'OC\\Accounts\\AccountManager' => __DIR__ . '/../../..' . '/lib/private/Accounts/AccountManager.php',
         'OC\\Accounts\\AccountProperty' => __DIR__ . '/../../..' . '/lib/private/Accounts/AccountProperty.php',
diff --git a/lib/private/Files/Node/File.php b/lib/private/Files/Node/File.php
index a3eabbcc446..b504c7a29da 100644
--- a/lib/private/Files/Node/File.php
+++ b/lib/private/Files/Node/File.php
@@ -119,7 +119,7 @@ class File extends Node implements \OCP\Files\File {
 			$fileInfo = $this->getFileInfo();
 			$this->view->unlink($this->path);
 			$nonExisting = new NonExistingFile($this->root, $this->view, $this->path, $fileInfo);
-			$this->root->emit('\OC\Files', 'postDelete', array($nonExisting));
+			$this->sendHooks(['postDelete'], [$nonExisting]);
 			$this->exists = false;
 			$this->fileInfo = null;
 		} else {
diff --git a/lib/private/Files/Node/Folder.php b/lib/private/Files/Node/Folder.php
index 19f04048779..8b2a93ffdc2 100644
--- a/lib/private/Files/Node/Folder.php
+++ b/lib/private/Files/Node/Folder.php
@@ -156,14 +156,12 @@ class Folder extends Node implements \OCP\Files\Folder {
 		if ($this->checkPermissions(\OCP\Constants::PERMISSION_CREATE)) {
 			$fullPath = $this->getFullPath($path);
 			$nonExisting = new NonExistingFolder($this->root, $this->view, $fullPath);
-			$this->root->emit('\OC\Files', 'preWrite', array($nonExisting));
-			$this->root->emit('\OC\Files', 'preCreate', array($nonExisting));
+			$this->sendHooks(['preWrite', 'preCreate'], [$nonExisting]);
 			if(!$this->view->mkdir($fullPath)) {
 				throw new NotPermittedException('Could not create folder');
 			}
 			$node = new Folder($this->root, $this->view, $fullPath);
-			$this->root->emit('\OC\Files', 'postWrite', array($node));
-			$this->root->emit('\OC\Files', 'postCreate', array($node));
+			$this->sendHooks(['postWrite', 'postCreate'], [$node]);
 			return $node;
 		} else {
 			throw new NotPermittedException('No create permission for folder');
@@ -179,14 +177,12 @@ class Folder extends Node implements \OCP\Files\Folder {
 		if ($this->checkPermissions(\OCP\Constants::PERMISSION_CREATE)) {
 			$fullPath = $this->getFullPath($path);
 			$nonExisting = new NonExistingFile($this->root, $this->view, $fullPath);
-			$this->root->emit('\OC\Files', 'preWrite', array($nonExisting));
-			$this->root->emit('\OC\Files', 'preCreate', array($nonExisting));
+			$this->sendHooks(['preWrite', 'preCreate'], [$nonExisting]);
 			if (!$this->view->touch($fullPath)) {
 				throw new NotPermittedException('Could not create path');
 			}
 			$node = new File($this->root, $this->view, $fullPath);
-			$this->root->emit('\OC\Files', 'postWrite', array($node));
-			$this->root->emit('\OC\Files', 'postCreate', array($node));
+			$this->sendHooks(['postWrite', 'postCreate'], [$node]);
 			return $node;
 		}
 		throw new NotPermittedException('No create permission for path');
@@ -341,7 +337,7 @@ class Folder extends Node implements \OCP\Files\Folder {
 			$fileInfo = $this->getFileInfo();
 			$this->view->rmdir($this->path);
 			$nonExisting = new NonExistingFolder($this->root, $this->view, $this->path, $fileInfo);
-			$this->root->emit('\OC\Files', 'postDelete', array($nonExisting));
+			$this->sendHooks(['postDelete'], [$nonExisting]);
 			$this->exists = false;
 		} else {
 			throw new NotPermittedException('No delete permission for path');
diff --git a/lib/private/Files/Node/HookConnector.php b/lib/private/Files/Node/HookConnector.php
index f5adcde4a00..4783a71b07b 100644
--- a/lib/private/Files/Node/HookConnector.php
+++ b/lib/private/Files/Node/HookConnector.php
@@ -26,6 +26,8 @@ use OCP\Files\FileInfo;
 use OC\Files\Filesystem;
 use OC\Files\View;
 use OCP\Util;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\EventDispatcher\GenericEvent;
 
 class HookConnector {
 	/**
@@ -42,6 +44,8 @@ class HookConnector {
 	 * @var FileInfo[]
 	 */
 	private $deleteMetaCache = [];
+	/** @var EventDispatcherInterface */
+	private $dispatcher;
 
 	/**
 	 * HookConnector constructor.
@@ -49,9 +53,10 @@ class HookConnector {
 	 * @param Root $root
 	 * @param View $view
 	 */
-	public function __construct(Root $root, View $view) {
+	public function __construct(Root $root, View $view, EventDispatcherInterface $dispatcher) {
 		$this->root = $root;
 		$this->view = $view;
+		$this->dispatcher = $dispatcher;
 	}
 
 	public function viewToNode() {
@@ -79,72 +84,85 @@ class HookConnector {
 	public function write($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'preWrite', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::preWrite', new GenericEvent($node));
 	}
 
 	public function postWrite($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'postWrite', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::postWrite', new GenericEvent($node));
 	}
 
 	public function create($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'preCreate', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::preCreate', new GenericEvent($node));
 	}
 
 	public function postCreate($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'postCreate', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::postCreate', new GenericEvent($node));
 	}
 
 	public function delete($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->deleteMetaCache[$node->getPath()] = $node->getFileInfo();
 		$this->root->emit('\OC\Files', 'preDelete', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::preDelete', new GenericEvent($node));
 	}
 
 	public function postDelete($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		unset($this->deleteMetaCache[$node->getPath()]);
 		$this->root->emit('\OC\Files', 'postDelete', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::postDelete', new GenericEvent($node));
 	}
 
 	public function touch($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'preTouch', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::preTouch', new GenericEvent($node));
 	}
 
 	public function postTouch($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'postTouch', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::postTouch', new GenericEvent($node));
 	}
 
 	public function rename($arguments) {
 		$source = $this->getNodeForPath($arguments['oldpath']);
 		$target = $this->getNodeForPath($arguments['newpath']);
 		$this->root->emit('\OC\Files', 'preRename', [$source, $target]);
+		$this->dispatcher->dispatch('\OCP\Files::preRename', new GenericEvent([$source, $target]));
 	}
 
 	public function postRename($arguments) {
 		$source = $this->getNodeForPath($arguments['oldpath']);
 		$target = $this->getNodeForPath($arguments['newpath']);
 		$this->root->emit('\OC\Files', 'postRename', [$source, $target]);
+		$this->dispatcher->dispatch('\OCP\Files::postRename', new GenericEvent([$source, $target]));
 	}
 
 	public function copy($arguments) {
 		$source = $this->getNodeForPath($arguments['oldpath']);
 		$target = $this->getNodeForPath($arguments['newpath']);
 		$this->root->emit('\OC\Files', 'preCopy', [$source, $target]);
+		$this->dispatcher->dispatch('\OCP\Files::preCopy', new GenericEvent([$source, $target]));
 	}
 
 	public function postCopy($arguments) {
 		$source = $this->getNodeForPath($arguments['oldpath']);
 		$target = $this->getNodeForPath($arguments['newpath']);
 		$this->root->emit('\OC\Files', 'postCopy', [$source, $target]);
+		$this->dispatcher->dispatch('\OCP\Files::postCopy', new GenericEvent([$source, $target]));
 	}
 
 	public function read($arguments) {
 		$node = $this->getNodeForPath($arguments['path']);
 		$this->root->emit('\OC\Files', 'read', [$node]);
+		$this->dispatcher->dispatch('\OCP\Files::read', new GenericEvent([$node]));
 	}
 
 	private function getNodeForPath($path) {
diff --git a/lib/private/Files/Node/Node.php b/lib/private/Files/Node/Node.php
index dc025b79575..c440dd4a8f1 100644
--- a/lib/private/Files/Node/Node.php
+++ b/lib/private/Files/Node/Node.php
@@ -33,6 +33,7 @@ use OCP\Files\FileInfo;
 use OCP\Files\InvalidPathException;
 use OCP\Files\NotFoundException;
 use OCP\Files\NotPermittedException;
+use Symfony\Component\EventDispatcher\GenericEvent;
 
 // FIXME: this class really should be abstract
 class Node implements \OCP\Files\Node {
@@ -104,9 +105,12 @@ class Node implements \OCP\Files\Node {
 	/**
 	 * @param string[] $hooks
 	 */
-	protected function sendHooks($hooks) {
+	protected function sendHooks($hooks, array $args = null) {
+		$args = !empty($args) ? $args : [$this];
+		$dispatcher = \OC::$server->getEventDispatcher();
 		foreach ($hooks as $hook) {
-			$this->root->emit('\OC\Files', $hook, array($this));
+			$this->root->emit('\OC\Files', $hook, $args);
+			$dispatcher->dispatch('\OCP\Files::' . $hook, new GenericEvent($args));
 		}
 	}
 
@@ -394,14 +398,14 @@ class Node implements \OCP\Files\Node {
 		$parent = $this->root->get(dirname($targetPath));
 		if ($parent instanceof Folder and $this->isValidPath($targetPath) and $parent->isCreatable()) {
 			$nonExisting = $this->createNonExistingNode($targetPath);
-			$this->root->emit('\OC\Files', 'preCopy', [$this, $nonExisting]);
-			$this->root->emit('\OC\Files', 'preWrite', [$nonExisting]);
+			$this->sendHooks(['preCopy'], [$this, $nonExisting]);
+			$this->sendHooks(['preWrite'], [$nonExisting]);
 			if (!$this->view->copy($this->path, $targetPath)) {
 				throw new NotPermittedException('Could not copy ' . $this->path . ' to ' . $targetPath);
 			}
 			$targetNode = $this->root->get($targetPath);
-			$this->root->emit('\OC\Files', 'postCopy', [$this, $targetNode]);
-			$this->root->emit('\OC\Files', 'postWrite', [$targetNode]);
+			$this->sendHooks(['postCopy'], [$this, $targetNode]);
+			$this->sendHooks(['postWrite'], [$targetNode]);
 			return $targetNode;
 		} else {
 			throw new NotPermittedException('No permission to copy to path ' . $targetPath);
@@ -425,14 +429,14 @@ class Node implements \OCP\Files\Node {
 			)
 		) {
 			$nonExisting = $this->createNonExistingNode($targetPath);
-			$this->root->emit('\OC\Files', 'preRename', [$this, $nonExisting]);
-			$this->root->emit('\OC\Files', 'preWrite', [$nonExisting]);
+			$this->sendHooks(['preRename'], [$this, $nonExisting]);
+			$this->sendHooks(['preWrite'], [$nonExisting]);
 			if (!$this->view->rename($this->path, $targetPath)) {
 				throw new NotPermittedException('Could not move ' . $this->path . ' to ' . $targetPath);
 			}
 			$targetNode = $this->root->get($targetPath);
-			$this->root->emit('\OC\Files', 'postRename', [$this, $targetNode]);
-			$this->root->emit('\OC\Files', 'postWrite', [$targetNode]);
+			$this->sendHooks(['postRename'], [$this, $targetNode]);
+			$this->sendHooks(['postWrite'], [$targetNode]);
 			$this->path = $targetPath;
 			return $targetNode;
 		} else {
diff --git a/lib/private/Server.php b/lib/private/Server.php
index bce4f0feaef..433ee044fa4 100644
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@@ -298,7 +298,7 @@ class Server extends ServerContainer implements IServerContainer {
 				$this->getLogger(),
 				$this->getUserManager()
 			);
-			$connector = new HookConnector($root, $view);
+			$connector = new HookConnector($root, $view, $c->getEventDispatcher());
 			$connector->viewToNode();
 
 			$previewConnector = new \OC\Preview\WatcherConnector($root, $c->getSystemConfig());
diff --git a/lib/public/WorkflowEngine/GenericEntityEvent.php b/lib/public/WorkflowEngine/GenericEntityEvent.php
new file mode 100644
index 00000000000..3ea34c6fb87
--- /dev/null
+++ b/lib/public/WorkflowEngine/GenericEntityEvent.php
@@ -0,0 +1,79 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+/**
+ * Class GenericEntityEvent
+ *
+ * @package OCP\WorkflowEngine
+ *
+ * @since 18.0.0
+ */
+class GenericEntityEvent implements IEntityEvent {
+
+	/** @var string */
+	private $displayName;
+	/** @var string */
+	private $eventName;
+
+	/**
+	 * GenericEntityEvent constructor.
+	 *
+	 * @since 18.0.0
+	 */
+	public function __construct(string $displayName, string $eventName) {
+		if(trim($displayName) === '') {
+			throw new \InvalidArgumentException('DisplayName must not be empty');
+		}
+		if(trim($eventName) === '') {
+			throw new \InvalidArgumentException('EventName must not be empty');
+		}
+
+		$this->displayName = trim($displayName);
+		$this->eventName = trim($eventName);
+	}
+
+	/**
+	 * returns a translated name to be presented in the web interface.
+	 *
+	 * Example: "created" (en), "kreita" (eo)
+	 *
+	 * @since 18.0.0
+	 */
+	public function getDisplayName(): string {
+		return $this->displayName;
+	}
+
+	/**
+	 * returns the event name that is emitted by the EventDispatcher, e.g.:
+	 *
+	 * Example: "OCA\MyApp\Factory\Cats::postCreated"
+	 *
+	 * @since 18.0.0
+	 */
+	public function getEventName(): string {
+		return $this->eventName;
+	}
+}
diff --git a/lib/public/WorkflowEngine/ICheck.php b/lib/public/WorkflowEngine/ICheck.php
index 1d4fc966460..f5586e83d51 100644
--- a/lib/public/WorkflowEngine/ICheck.php
+++ b/lib/public/WorkflowEngine/ICheck.php
@@ -2,6 +2,7 @@
 /**
  * @copyright Copyright (c) 2016 Morris Jobke <hey@morrisjobke.de>
  *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
  * @author Morris Jobke <hey@morrisjobke.de>
  *
  * @license GNU AGPL version 3 or any later version
@@ -23,9 +24,6 @@
 
 namespace OCP\WorkflowEngine;
 
-
-use OCP\Files\Storage\IStorage;
-
 /**
  * Interface ICheck
  *
@@ -34,13 +32,6 @@ use OCP\Files\Storage\IStorage;
  */
 interface ICheck {
 	/**
-	 * @param IStorage $storage
-	 * @param string $path
-	 * @since 9.1
-	 */
-	public function setFileInfo(IStorage $storage, $path);
-
-	/**
 	 * @param string $operator
 	 * @param string $value
 	 * @return bool
@@ -55,4 +46,28 @@ interface ICheck {
 	 * @since 9.1
 	 */
 	public function validateCheck($operator, $value);
+
+	/**
+	 * returns a list of Entities the checker supports. The values must match
+	 * the class name of the entity.
+	 *
+	 * An empty result means the check is universally available.
+	 *
+	 * @since 18.0.0
+	 */
+	public function supportedEntities(): array;
+
+	/**
+	 * returns whether the operation can be used in the requested scope.
+	 *
+	 * Scope IDs are defined as constants in OCP\WorkflowEngine\IManager. At
+	 * time of writing these are SCOPE_ADMIN and SCOPE_USER.
+	 *
+	 * For possibly unknown future scopes the recommended behaviour is: if
+	 * user scope is permitted, the default behaviour should return `true`,
+	 * otherwise `false`.
+	 *
+	 * @since 18.0.0
+	 */
+	public function isAvailableForScope(int $scope): bool;
 }
diff --git a/lib/public/WorkflowEngine/IComplexOperation.php b/lib/public/WorkflowEngine/IComplexOperation.php
new file mode 100644
index 00000000000..63a4ca2460a
--- /dev/null
+++ b/lib/public/WorkflowEngine/IComplexOperation.php
@@ -0,0 +1,56 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+/**
+ * Interface IComplexOperation
+ *
+ * This interface represents an operator that is less generic and indicates
+ * that some of the tasks it does itself instead of relying on the engine.
+ * This includes:
+ *
+ * * registering listeners – the implementing app needs to ensure that the
+ *   business logic registers listeners to the events it listens to. For example
+ *   when direct storage access is required, adding a wrapper or listening to
+ *   a specific one is required over usual file events.
+ *
+ * @package OCP\WorkflowEngine
+ *
+ * @since 18.0.0
+ */
+interface IComplexOperation extends IOperation {
+
+	/**
+	 * As IComplexOperation chooses the triggering events itself, a hint has
+	 * to be shown to the user so make clear when this operation is becoming
+	 * active. This method returns such a translated string.
+	 *
+	 * Example: "When a file is accessed" (en)
+	 *
+	 * @since 18.0.0
+	 */
+	public function getTriggerHint(): string;
+
+}
diff --git a/lib/public/WorkflowEngine/IEntity.php b/lib/public/WorkflowEngine/IEntity.php
new file mode 100644
index 00000000000..c08e9072a38
--- /dev/null
+++ b/lib/public/WorkflowEngine/IEntity.php
@@ -0,0 +1,77 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+use Symfony\Component\EventDispatcher\GenericEvent;
+
+/**
+ * Interface IEntity
+ *
+ * This interface represents an entity that supports events the workflow engine
+ * can listen to. For example a file with the create, update, etc. events.
+ *
+ * Ensure to listen to 'OCP/WorkflowEngine::loadEntities' for registering your
+ * entities.
+ *
+ * @package OCP\WorkflowEngine
+ * @since 18.0.0
+ */
+interface IEntity {
+
+	/**
+	 * returns a translated name to be presented in the web interface.
+	 *
+	 * Example: "File" (en), "Dosiero" (eo)
+	 *
+	 * @since 18.0.0
+	 */
+	public function getName(): string;
+
+	/**
+	 * returns the URL to the icon of the entity for display in the web interface.
+	 *
+	 * Usually, the implementation would utilize the `imagePath()` method of the
+	 * `\OCP\IURLGenerator` instance and simply return its result.
+	 *
+	 * Example implementation: return $this->urlGenerator->imagePath('myApp', 'cat.svg');
+	 *
+	 * @since 18.0.0
+	 */
+	public function getIcon(): string;
+
+	/**
+	 * returns a list of supported events
+	 *
+	 * @return IEntityEvent[]
+	 * @since 18.0.0
+	 */
+	public function getEvents(): array;
+
+	/**
+	 * @since 18.0.0
+	 */
+	public function prepareRuleMatcher(IRuleMatcher $ruleMatcher, string $eventName, GenericEvent $event): void;
+
+}
diff --git a/lib/public/WorkflowEngine/IEntityCheck.php b/lib/public/WorkflowEngine/IEntityCheck.php
new file mode 100644
index 00000000000..7a4df0afd5f
--- /dev/null
+++ b/lib/public/WorkflowEngine/IEntityCheck.php
@@ -0,0 +1,54 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+
+use OCP\Files\Storage\IStorage;
+
+/**
+ * Interface IFileCheck
+ *
+ * @package OCP\WorkflowEngine
+ * @since 18.0.0
+ */
+interface IEntityCheck {
+	/**
+	 * Equips the check with a subject fitting the Entity. For instance, an
+	 * entity of File will receive an instance of OCP\Files\Node, or a comment
+	 * entity might get an IComment.
+	 *
+	 * The implementing check must be aware of the incoming type.
+	 *
+	 * If an unsupported subject is passed the implementation MAY throw an
+	 * \UnexpectedValueException.
+	 *
+	 * @param IEntity $entity
+	 * @param mixed $subject
+	 * @throws \UnexpectedValueException
+	 * @since 18.0.0
+	 */
+	public function setEntitySubject(IEntity $entity, $subject): void;
+
+}
diff --git a/lib/public/WorkflowEngine/IEntityEvent.php b/lib/public/WorkflowEngine/IEntityEvent.php
new file mode 100644
index 00000000000..8baa0573fa8
--- /dev/null
+++ b/lib/public/WorkflowEngine/IEntityEvent.php
@@ -0,0 +1,54 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+/**
+ * Interface IEntityEvent
+ *
+ * represents an entitiy event that is dispatched via EventDispatcher
+ *
+ * @package OCP\WorkflowEngine
+ *
+ * @since 18.0.0
+ */
+interface IEntityEvent {
+	/**
+	 * returns a translated name to be presented in the web interface.
+	 *
+	 * Example: "created" (en), "kreita" (eo)
+	 *
+	 * @since 18.0.0
+	 */
+	public function getDisplayName(): string;
+
+	/**
+	 * returns the event name that is emitted by the EventDispatcher, e.g.:
+	 *
+	 * Example: "OCA\MyApp\Factory\Cats::postCreated"
+	 *
+	 * @since 18.0.0
+	 */
+	public function getEventName(): string;
+}
diff --git a/lib/public/WorkflowEngine/IFileCheck.php b/lib/public/WorkflowEngine/IFileCheck.php
new file mode 100644
index 00000000000..557ba0f3c10
--- /dev/null
+++ b/lib/public/WorkflowEngine/IFileCheck.php
@@ -0,0 +1,42 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+
+use OCP\Files\Storage\IStorage;
+
+/**
+ * Interface IFileCheck
+ *
+ * @package OCP\WorkflowEngine
+ * @since 18.0.0
+ */
+interface IFileCheck extends IEntityCheck {
+	/**
+	 * @since 18.0.0
+	 */
+	public function setFileInfo(IStorage $storage, string $path);
+
+}
diff --git a/lib/public/WorkflowEngine/IManager.php b/lib/public/WorkflowEngine/IManager.php
index cd323a816f3..78fd718ec9e 100644
--- a/lib/public/WorkflowEngine/IManager.php
+++ b/lib/public/WorkflowEngine/IManager.php
@@ -23,9 +23,6 @@
 
 namespace OCP\WorkflowEngine;
 
-
-use OCP\Files\Storage\IStorage;
-
 /**
  * Interface IManager
  *
@@ -33,18 +30,40 @@ use OCP\Files\Storage\IStorage;
  * @since 9.1
  */
 interface IManager {
+
+	const SCOPE_ADMIN = 0;
+	const SCOPE_USER = 1;
+
+	const EVENT_NAME_REG_OPERATION = 'OCP\WorkflowEngine::registerOperations';
+	const EVENT_NAME_REG_ENTITY = 'OCP\WorkflowEngine::registerEntities';
+	const EVENT_NAME_REG_CHECK = 'OCP\WorkflowEngine::registerChecks';
+
+	/**
+	 * Listen to `\OCP\WorkflowEngine::EVENT_NAME_REG_ENTITY` at the
+	 * EventDispatcher for registering your entities.
+	 *
+	 * @since 18.0.0
+	 */
+	public function registerEntity(IEntity $entity): void;
+
+	/**
+	 * Listen to `\OCP\WorkflowEngine::EVENT_NAME_REG_OPERATION` at the
+	 * EventDispatcher for registering your operators.
+	 *
+	 * @since 18.0.0
+	 */
+	public function registerOperation(IOperation $operator): void;
+
 	/**
-	 * @param IStorage $storage
-	 * @param string $path
-	 * @since 9.1
+	 * Listen to `\OCP\WorkflowEngine::EVENT_NAME_REG_CHECK` at the
+	 * EventDispatcher for registering your operators.
+	 *
+	 * @since 18.0.0
 	 */
-	public function setFileInfo(IStorage $storage, $path);
+	public function registerCheck(ICheck $check): void;
 
 	/**
-	 * @param string $class
-	 * @param bool $returnFirstMatchingOperationOnly
-	 * @return array
-	 * @since 9.1
+	 * @since 18.0.0
 	 */
-	public function getMatchingOperations($class, $returnFirstMatchingOperationOnly = true);
+	public function getRuleMatcher(): IRuleMatcher;
 }
diff --git a/lib/public/WorkflowEngine/IOperation.php b/lib/public/WorkflowEngine/IOperation.php
index 491a805909c..d16fd618a84 100644
--- a/lib/public/WorkflowEngine/IOperation.php
+++ b/lib/public/WorkflowEngine/IOperation.php
@@ -23,6 +23,8 @@
 
 namespace OCP\WorkflowEngine;
 
+use Symfony\Component\EventDispatcher\GenericEvent;
+
 /**
  * Interface IOperation
  *
@@ -31,11 +33,71 @@ namespace OCP\WorkflowEngine;
  */
 interface IOperation {
 	/**
-	 * @param string $name
-	 * @param array[] $checks
-	 * @param string $operation
+	 * returns a translated name to be presented in the web interface
+	 *
+	 * Example: "Automated tagging" (en), "Aŭtomata etikedado" (eo)
+	 *
+	 * @since 18.0.0
+	 */
+	public function getDisplayName(): string;
+
+	/**
+	 * returns a translated, descriptive text to be presented in the web interface.
+	 *
+	 * It should be short and precise.
+	 *
+	 * Example: "Tag based automatic deletion of files after a given time." (en)
+	 *
+	 * @since 18.0.0
+	 */
+	public function getDescription(): string;
+
+	/**
+	 * returns the URL to the icon of the operator for display in the web interface.
+	 *
+	 * Usually, the implementation would utilize the `imagePath()` method of the
+	 * `\OCP\IURLGenerator` instance and simply return its result.
+	 *
+	 * Example implementation: return $this->urlGenerator->imagePath('myApp', 'cat.svg');
+	 *
+	 * @since 18.0.0
+	 */
+	public function getIcon(): string;
+
+	/**
+	 * returns whether the operation can be used in the requested scope.
+	 *
+	 * Scope IDs are defined as constants in OCP\WorkflowEngine\IManager. At
+	 * time of writing these are SCOPE_ADMIN and SCOPE_USER.
+	 *
+	 * For possibly unknown future scopes the recommended behaviour is: if
+	 * user scope is permitted, the default behaviour should return `true`,
+	 * otherwise `false`.
+	 *
+	 * @since 18.0.0
+	 */
+	public function isAvailableForScope(int $scope): bool;
+
+	/**
+	 * Validates whether a configured workflow rule is valid. If it is not,
+	 * an `\UnexpectedValueException` is supposed to be thrown.
+	 *
 	 * @throws \UnexpectedValueException
 	 * @since 9.1
 	 */
-	public function validateOperation($name, array $checks, $operation);
+	public function validateOperation(string $name, array $checks, string $operation): void;
+
+	/**
+	 * Is being called by the workflow engine when an event was triggered that
+	 * is configured for this operation. An evaluation whether the event
+	 * qualifies for this operation to run has still to be done by the
+	 * implementor by calling the RuleMatchers getMatchingOperations method
+	 * and evaluating the results.
+	 *
+	 * If the implementor is an IComplexOperation, this method will not be
+	 * called automatically. It can be used or left as no-op by the implementor.
+	 *
+	 * @since 18.0.0
+	 */
+	public function onEvent(string $eventName, GenericEvent $event, IRuleMatcher $ruleMatcher): void;
 }
diff --git a/lib/public/WorkflowEngine/IRuleMatcher.php b/lib/public/WorkflowEngine/IRuleMatcher.php
new file mode 100644
index 00000000000..5569800edb7
--- /dev/null
+++ b/lib/public/WorkflowEngine/IRuleMatcher.php
@@ -0,0 +1,39 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+/**
+ * Class IRuleMatcher
+ *
+ * @package OCP\WorkflowEngine
+ *
+ * @since 18.0.0
+ */
+interface IRuleMatcher extends IFileCheck {
+	/**
+	 * @since 18.0.0
+	 */
+	public function getMatchingOperations(string $class, bool $returnFirstMatchingOperationOnly = true): array;
+}
diff --git a/lib/public/WorkflowEngine/ISpecificOperation.php b/lib/public/WorkflowEngine/ISpecificOperation.php
new file mode 100644
index 00000000000..0b26770a13a
--- /dev/null
+++ b/lib/public/WorkflowEngine/ISpecificOperation.php
@@ -0,0 +1,50 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCP\WorkflowEngine;
+
+/**
+ * Interface ISpecificOperation
+ *
+ * This interface represents an operator that is designed to work with exactly
+ * one entity type.
+ *
+ * In almost all of the cases it is not necessary to have this limitation,
+ * because the action is not connected to the event. This mechanism suits
+ * special cases.
+ *
+ * @package OCP\WorkflowEngine
+ * @since 18.0.0
+ */
+interface ISpecificOperation extends IOperation {
+
+	/**
+	 * returns the id of the entity the operator is designed for
+	 *
+	 * Example: 'WorkflowEngine_Entity_File'
+	 *
+	 * @since 18.0.0
+	 */
+	public function getEntityId():string;
+}