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>

3 files changed, 45 insertions, 12 deletions

diff --git a/apps/files_versions/lib/Versions/IVersionBackend.php b/apps/files_versions/lib/Versions/IVersionBackend.php
index 616d535f7fd..913745c9850 100644
--- a/apps/files_versions/lib/Versions/IVersionBackend.php
+++ b/apps/files_versions/lib/Versions/IVersionBackend.php
@@ -25,6 +25,7 @@ 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;
 
 /**
@@ -32,6 +33,17 @@ use OCP\IUser;
  */
 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
 	 *
 	 * @param IUser $user
diff --git a/apps/files_versions/lib/Versions/LegacyVersionsBackend.php b/apps/files_versions/lib/Versions/LegacyVersionsBackend.php
index 99424f54564..aceddef29d2 100644
--- a/apps/files_versions/lib/Versions/LegacyVersionsBackend.php
+++ b/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)) {
diff --git a/apps/files_versions/lib/Versions/VersionManager.php b/apps/files_versions/lib/Versions/VersionManager.php
index 757b6002710..99fa9f62bc8 100644
--- a/apps/files_versions/lib/Versions/VersionManager.php
+++ b/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;
+	}
 }