add way for version backends to programmatically specify if they should be used

this allows for backends that should only be used if specific conditions are met

Signed-off-by: Robin Appelman <robin@icewind.nl>

apps/files_versions/lib/Versions/IVersionBackend.php

@@ -25,12 +25,24 @@ use OCP\Files\File;
 use OCP\Files\FileInfo;
 use OCP\Files\NotFoundException;
 use OCP\Files\SimpleFS\ISimpleFile;
+use OCP\Files\Storage\IStorage;
 use OCP\IUser;
 
 /**
  * @since 15.0.0
  */
 interface IVersionBackend {
+	/**
+	 * Whether or not this version backend should be used for a storage
+	 *
+	 * If false is returned then the next applicable backend will be used
+	 *
+	 * @param IStorage $storage
+	 * @return bool
+	 * @since 17.0.0
+	 */
+	public function useBackendForStorage(IStorage $storage): bool;
+
 	/**
 	 * Get all versions for a file
 	 *

apps/files_versions/lib/Versions/LegacyVersionsBackend.php

@@ -29,6 +29,7 @@ use OCP\Files\FileInfo;
 use OCP\Files\Folder;
 use OCP\Files\IRootFolder;
 use OCP\Files\NotFoundException;
+use OCP\Files\Storage\IStorage;
 use OCP\IUser;
 use OCP\IUserManager;
 
@@ -43,6 +44,10 @@ class LegacyVersionsBackend implements IVersionBackend {
 		$this->userManager = $userManager;
 	}
 
+	public function useBackendForStorage(IStorage $storage): bool {
+		return true;
+	}
+
 	public function getVersionsForFile(IUser $user, FileInfo $file): array {
 		$storage = $file->getStorage();
 		if ($storage->instanceOfStorage(SharedStorage::class)) {

apps/files_versions/lib/Versions/VersionManager.php

@@ -27,15 +27,18 @@ use OCP\Files\Storage\IStorage;
 use OCP\IUser;
 
 class VersionManager implements IVersionManager {
-	/** @var IVersionBackend[] */
+	/** @var (IVersionBackend[])[] */
 	private $backends = [];
 
 	public function registerBackend(string $storageType, IVersionBackend $backend) {
-		$this->backends[$storageType] = $backend;
+		if (!isset($this->backends[$storageType])) {
+			$this->backends[$storageType] = [];
+		}
+		$this->backends[$storageType][] = $backend;
 	}
 
 	/**
-	 * @return IVersionBackend[]
+	 * @return (IVersionBackend[])[]
 	 */
 	private function getBackends(): array {
 		return $this->backends;
@@ -49,20 +52,29 @@ class VersionManager implements IVersionManager {
 	public function getBackendForStorage(IStorage $storage): IVersionBackend {
 		$fullType = get_class($storage);
 		$backends = $this->getBackends();
-		$foundType = array_reduce(array_keys($backends), function ($type, $registeredType) use ($storage) {
+
+		$foundType = '';
+		$foundBackend = null;
+
+		foreach ($backends as $type => $backendsForType) {
 			if (
-				$storage->instanceOfStorage($registeredType) &&
-				($type === '' || is_subclass_of($registeredType, $type))
+				$storage->instanceOfStorage($type) &&
+				($foundType === '' || is_subclass_of($type, $foundType))
 			) {
-				return $registeredType;
-			} else {
-				return $type;
+				foreach ($backendsForType as $backend) {
+					/** @var IVersionBackend $backend */
+					if ($backend->useBackendForStorage($storage)) {
+						$foundBackend = $backend;
+						$foundType = $type;
+					}
+				}
 			}
-		}, '');
-		if ($foundType === '') {
+		}
+
+		if ($foundType === '' || $foundBackend === null) {
 			throw new BackendNotFoundException("Version backend for $fullType not found");
 		} else {
-			return $backends[$foundType];
+			return $foundBackend;
 		}
 	}
 
@@ -90,4 +102,8 @@ class VersionManager implements IVersionManager {
 		$backend = $this->getBackendForStorage($sourceFile->getStorage());
 		return $backend->getVersionFile($user, $sourceFile, $revision);
 	}
+
+	public function useBackendForStorage(IStorage $storage): bool {
+		return false;
+	}
 }

apps/files_versions/tests/Versions/VersionManagerTest.php

@@ -0,0 +1,84 @@
+<?php declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019 Robin Appelman <robin@icewind.nl>
+ *
+ * @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 OCA\files_versions\tests\Versions;
+
+use OC\Files\Storage\Local;
+use OCA\Files_Versions\Versions\IVersionBackend;
+use OCA\Files_Versions\Versions\VersionManager;
+use OCP\Files\Storage\IStorage;
+use Test\TestCase;
+
+class VersionManagerTest extends TestCase {
+	private function getBackend(bool $shouldUse = true): IVersionBackend {
+		$backend = $this->createMock(IVersionBackend::class);
+		$backend->method('useBackendForStorage')
+			->willReturn($shouldUse);
+		return $backend;
+	}
+
+	private function getStorage(string $class): IStorage {
+		return $this->getMockBuilder($class)
+			->disableOriginalConstructor()
+			->setMethodsExcept(['instanceOfStorage'])
+			->getMock();
+	}
+
+	public function testGetBackendSingle() {
+		$manager = new VersionManager();
+		$backend = $this->getBackend();
+		$manager->registerBackend(IStorage::class, $backend);
+
+		$this->assertEquals($backend, $manager->getBackendForStorage($this->getStorage(Local::class)));
+	}
+
+	public function testGetBackendMoreSpecific() {
+		$manager = new VersionManager();
+		$backend1 = $this->getBackend();
+		$backend2 = $this->getBackend();
+		$manager->registerBackend(IStorage::class, $backend1);
+		$manager->registerBackend(Local::class, $backend2);
+
+		$this->assertEquals($backend2, $manager->getBackendForStorage($this->getStorage(Local::class)));
+	}
+
+	public function testGetBackendNoUse() {
+		$manager = new VersionManager();
+		$backend1 = $this->getBackend();
+		$backend2 = $this->getBackend(false);
+		$manager->registerBackend(IStorage::class, $backend1);
+		$manager->registerBackend(Local::class, $backend2);
+
+		$this->assertEquals($backend1, $manager->getBackendForStorage($this->getStorage(Local::class)));
+	}
+
+	public function testGetBackendMultiple() {
+		$manager = new VersionManager();
+		$backend1 = $this->getBackend();
+		$backend2 = $this->getBackend(false);
+		$backend3 = $this->getBackend();
+		$manager->registerBackend(IStorage::class, $backend1);
+		$manager->registerBackend(Local::class, $backend2);
+		$manager->registerBackend(Local::class, $backend3);
+
+		$this->assertEquals($backend3, $manager->getBackendForStorage($this->getStorage(Local::class)));
+	}
+}