<?php
/**
 * @copyright Copyright (c) 2016, ownCloud, Inc.
 *
 * @author Bart Visscher <bartv@thisnet.nl>
 * @author Bastien Ho <bastienho@urbancube.fr>
 * @author Bjoern Schiessle <bjoern@schiessle.org>
 * @author Björn Schießle <bjoern@schiessle.org>
 * @author Christoph Wurst <christoph@winzerhof-wurst.at>
 * @author Daniel Kesselberg <mail@danielkesselberg.de>
 * @author Florin Peter <github@florin-peter.de>
 * @author Georg Ehrke <oc.list@georgehrke.com>
 * @author Joas Schilling <coding@schilljs.com>
 * @author Jörn Friedrich Dreyer <jfd@butonic.de>
 * @author Juan Pablo Villafáñez <jvillafanez@solidgear.es>
 * @author Lars Knickrehm <mail@lars-sh.de>
 * @author Lukas Reschke <lukas@statuscode.ch>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Qingping Hou <dave2008713@gmail.com>
 * @author Robin Appelman <robin@icewind.nl>
 * @author Robin McCorkell <robin@mccorkell.me.uk>
 * @author Roeland Jago Douma <roeland@famdouma.nl>
 * @author Sjors van der Pluijm <sjors@desjors.nl>
 * @author Steven Bühner <buehner@me.com>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 * @author Victor Dubiniuk <dubiniuk@owncloud.com>
 * @author Vincent Petry <pvince81@owncloud.com>
 *
 * @license AGPL-3.0
 *
 * This code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * 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, version 3,
 * along with this program. If not, see <http://www.gnu.org/licenses/>
 *
 */

namespace OCA\Files_Trashbin;

use OC\Files\Cache\Cache;
use OC\Files\Cache\CacheEntry;
use OC\Files\Cache\CacheQueryBuilder;
use OC\Files\Filesystem;
use OC\Files\ObjectStore\ObjectStoreStorage;
use OC\Files\View;
use OCA\Files_Trashbin\AppInfo\Application;
use OCA\Files_Trashbin\Command\Expire;
use OCP\AppFramework\Utility\ITimeFactory;
use OCP\Files\File;
use OCP\Files\Folder;
use OCP\Files\NotFoundException;
use OCP\Files\NotPermittedException;
use OCP\Lock\ILockingProvider;
use OCP\Lock\LockedException;
use OCP\User;

class Trashbin {

	// unit: percentage; 50% of available disk space/quota
	public const DEFAULTMAXSIZE = 50;

	/**
	 * Whether versions have already be rescanned during this PHP request
	 *
	 * @var bool
	 */
	private static $scannedVersions = false;

	/**
	 * Ensure we don't need to scan the file during the move to trash
	 * by triggering the scan in the pre-hook
	 *
	 * @param array $params
	 */
	public static function ensureFileScannedHook($params) {
		try {
			self::getUidAndFilename($params['path']);
		} catch (NotFoundException $e) {
			// nothing to scan for non existing files
		}
	}

	/**
	 * get the UID of the owner of the file and the path to the file relative to
	 * owners files folder
	 *
	 * @param string $filename
	 * @return array
	 * @throws \OC\User\NoUserException
	 */
	public static function getUidAndFilename($filename) {
		$uid = Filesystem::getOwner($filename);
		$userManager = \OC::$server->getUserManager();
		// if the user with the UID doesn't exists, e.g. because the UID points
		// to a remote user with a federated cloud ID we use the current logged-in
		// user. We need a valid local user to move the file to the right trash bin
		if (!$userManager->userExists($uid)) {
			$uid = User::getUser();
		}
		if (!$uid) {
			// no owner, usually because of share link from ext storage
			return [null, null];
		}
		Filesystem::initMountPoints($uid);
		if ($uid !== User::getUser()) {
			$info = Filesystem::getFileInfo($filename);
			$ownerView = new View('/' . $uid . '/files');
			try {
				$filename = $ownerView->getPath($info['fileid']);
			} catch (NotFoundException $e) {
				$filename = null;
			}
		}
		return [$uid, $filename];
	}

	/**
	 * get original location of files for user
	 *
	 * @param string $user
	 * @return array (filename => array (timestamp => original location))
	 */
	public static function getLocations($user) {
		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
		$query->select('id', 'timestamp', 'location')
			->from('files_trash')
			->where($query->expr()->eq('user', $query->createNamedParameter($user)));
		$result = $query->execute();
		$array = [];
		while ($row = $result->fetch()) {
			if (isset($array[$row['id']])) {
				$array[$row['id']][$row['timestamp']] = $row['location'];
			} else {
				$array[$row['id']] = [$row['timestamp'] => $row['location']];
			}
		}
		$result->closeCursor();
		return $array;
	}

	/**
	 * get original location of file
	 *
	 * @param string $user
	 * @param string $filename
	 * @param string $timestamp
	 * @return string original location
	 */
	public static function getLocation($user, $filename, $timestamp) {
		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
		$query->select('location')
			->from('files_trash')
			->where($query->expr()->eq('user', $query->createNamedParameter($user)))
			->andWhere($query->expr()->eq('id', $query->createNamedParameter($filename)))
			->andWhere($query->expr()->eq('timestamp', $query->createNamedParameter($timestamp)));

		$result = $query->execute();
		$row = $result->fetch();
		$result->closeCursor();

		if (isset($row['location'])) {
			return $row['location'];
		} else {
			return false;
		}
	}

	private static function setUpTrash($user) {
		$view = new View('/' . $user);
		if (!$view->is_dir('files_trashbin')) {
			$view->mkdir('files_trashbin');
		}
		if (!$view->is_dir('files_trashbin/files')) {
			$view->mkdir('files_trashbin/files');
		}
		if (!$view->is_dir('files_trashbin/versions')) {
			$view->mkdir('files_trashbin/versions');
		}
		if (!$view->is_dir('files_trashbin/keys')) {
			$view->mkdir('files_trashbin/keys');
		}
	}


	/**
	 * copy file to owners trash
	 *
	 * @param string $sourcePath
	 * @param string $owner
	 * @param string $targetPath
	 * @param $user
	 * @param integer $timestamp
	 */
	private static function copyFilesToUser($sourcePath, $owner, $targetPath, $user, $timestamp) {
		self::setUpTrash($owner);

		$targetFilename = basename($targetPath);
		$targetLocation = dirname($targetPath);

		$sourceFilename = basename($sourcePath);

		$view = new View('/');

		$target = $user . '/files_trashbin/files/' . $targetFilename . '.d' . $timestamp;
		$source = $owner . '/files_trashbin/files/' . $sourceFilename . '.d' . $timestamp;
		$free = $view->free_space($target);
		$isUnknownOrUnlimitedFreeSpace = $free < 0;
		$isEnoughFreeSpaceLeft = $view->filesize($source) < $free;
		if ($isUnknownOrUnlimitedFreeSpace || $isEnoughFreeSpaceLeft) {
			self::copy_recursive($source, $target, $view);
		}


		if ($view->file_exists($target)) {
			$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
			$query->insert('files_trash')
				->setValue('id', $query->createNamedParameter($targetFilename))
				->setValue('timestamp', $query->createNamedParameter($timestamp))
				->setValue('location', $query->createNamedParameter($targetLocation))
				->setValue('user', $query->createNamedParameter($user));
			$result = $query->execute();
			if (!$result) {
				\OC::$server->getLogger()->error('trash bin database couldn\'t be updated for the files owner', ['app' => 'files_trashbin']);
			}
		}
	}


	/**
	 * move file to the trash bin
	 *
	 * @param string $file_path path to the deleted file/directory relative to the files root directory
	 * @param bool $ownerOnly delete for owner only (if file gets moved out of a shared folder)
	 *
	 * @return bool
	 */
	public static function move2trash($file_path, $ownerOnly = false) {
		// get the user for which the filesystem is setup
		$root = Filesystem::getRoot();
		[, $user] = explode('/', $root);
		[$owner, $ownerPath] = self::getUidAndFilename($file_path);

		// if no owner found (ex: ext storage + share link), will use the current user's trashbin then
		if (is_null($owner)) {
			$owner = $user;
			$ownerPath = $file_path;
		}

		$ownerView = new View('/' . $owner);
		// file has been deleted in between
		if (is_null($ownerPath) || $ownerPath === '' || !$ownerView->file_exists('/files/' . $ownerPath)) {
			return true;
		}

		self::setUpTrash($user);
		if ($owner !== $user) {
			// also setup for owner
			self::setUpTrash($owner);
		}

		$path_parts = pathinfo($ownerPath);

		$filename = $path_parts['basename'];
		$location = $path_parts['dirname'];
		/** @var ITimeFactory $timeFactory */
		$timeFactory = \OC::$server->query(ITimeFactory::class);
		$timestamp = $timeFactory->getTime();

		$lockingProvider = \OC::$server->getLockingProvider();

		// disable proxy to prevent recursive calls
		$trashPath = '/files_trashbin/files/' . $filename . '.d' . $timestamp;
		$gotLock = false;

		while (!$gotLock) {
			try {
				/** @var \OC\Files\Storage\Storage $trashStorage */
				[$trashStorage, $trashInternalPath] = $ownerView->resolvePath($trashPath);

				$trashStorage->acquireLock($trashInternalPath, ILockingProvider::LOCK_EXCLUSIVE, $lockingProvider);
				$gotLock = true;
			} catch (LockedException $e) {
				// a file with the same name is being deleted concurrently
				// nudge the timestamp a bit to resolve the conflict

				$timestamp = $timestamp + 1;

				$trashPath = '/files_trashbin/files/' . $filename . '.d' . $timestamp;
			}
		}

		/** @var \OC\Files\Storage\Storage $sourceStorage */
		[$sourceStorage, $sourceInternalPath] = $ownerView->resolvePath('/files/' . $ownerPath);


		if ($trashStorage->file_exists($trashInternalPath)) {
			$trashStorage->unlink($trashInternalPath);
		}

		$trashStorage->getUpdater()->renameFromStorage($sourceStorage, $sourceInternalPath, $trashInternalPath);

		try {
			$moveSuccessful = true;

			// when moving within the same object store, the cache update done above is enough to move the file
			if (!($trashStorage->instanceOfStorage(ObjectStoreStorage::class) && $trashStorage->getId() === $sourceStorage->getId())) {
				$trashStorage->moveFromStorage($sourceStorage, $sourceInternalPath, $trashInternalPath);
			}
		} catch (\OCA\Files_Trashbin\Exceptions\CopyRecursiveException $e) {
			$moveSuccessful = false;
			if ($trashStorage->file_exists($trashInternalPath)) {
				$trashStorage->unlink($trashInternalPath);
			}
			\OC::$server->getLogger()->error('Couldn\'t move ' . $file_path . ' to the trash bin', ['app' => 'files_trashbin']);
		}

		if ($sourceStorage->file_exists($sourceInternalPath)) { // failed to delete the original file, abort
			if ($sourceStorage->is_dir($sourceInternalPath)) {
				$sourceStorage->rmdir($sourceInternalPath);
			} else {
				$sourceStorage->unlink($sourceInternalPath);
			}

			if ($sourceStorage->file_exists($sourceInternalPath)) {
				// undo the cache move
				$sourceStorage->getUpdater()->renameFromStorage($trashStorage, $trashInternalPath, $sourceInternalPath);
			} else {
				$trashStorage->getUpdater()->remove($trashInternalPath);
			}
			return false;
		}

		if ($moveSuccessful) {
			$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
			$query->insert('files_trash')
				->setValue('id', $query->createNamedParameter($filename))
				->setValue('timestamp', $query->createNamedParameter($timestamp))
				->setValue('location', $query->createNamedParameter($location))
				->setValue('user', $query->createNamedParameter($owner));
			$result = $query->execute();
			if (!$result) {
				\OC::$server->getLogger()->error('trash bin database couldn\'t be updated', ['app' => 'files_trashbin']);
			}
			\OCP\Util::emitHook('\OCA\Files_Trashbin\Trashbin', 'post_moveToTrash', ['filePath' => Filesystem::normalizePath($file_path),
				'trashPath' => Filesystem::normalizePath($filename . '.d' . $timestamp)]);

			self::retainVersions($filename, $owner, $ownerPath, $timestamp);

			// if owner !== user we need to also add a copy to the users trash
			if ($user !== $owner && $ownerOnly === false) {
				self::copyFilesToUser($ownerPath, $owner, $file_path, $user, $timestamp);
			}
		}

		$trashStorage->releaseLock($trashInternalPath, ILockingProvider::LOCK_EXCLUSIVE, $lockingProvider);

		self::scheduleExpire($user);

		// if owner !== user we also need to update the owners trash size
		if ($owner !== $user) {
			self::scheduleExpire($owner);
		}

		return $moveSuccessful;
	}

	/**
	 * Move file versions to trash so that they can be restored later
	 *
	 * @param string $filename of deleted file
	 * @param string $owner owner user id
	 * @param string $ownerPath path relative to the owner's home storage
	 * @param integer $timestamp when the file was deleted
	 */
	private static function retainVersions($filename, $owner, $ownerPath, $timestamp) {
		if (\OCP\App::isEnabled('files_versions') && !empty($ownerPath)) {
			$user = User::getUser();
			$rootView = new View('/');

			if ($rootView->is_dir($owner . '/files_versions/' . $ownerPath)) {
				if ($owner !== $user) {
					self::copy_recursive($owner . '/files_versions/' . $ownerPath, $owner . '/files_trashbin/versions/' . basename($ownerPath) . '.d' . $timestamp, $rootView);
				}
				self::move($rootView, $owner . '/files_versions/' . $ownerPath, $user . '/files_trashbin/versions/' . $filename . '.d' . $timestamp);
			} elseif ($versions = \OCA\Files_Versions\Storage::getVersions($owner, $ownerPath)) {
				foreach ($versions as $v) {
					if ($owner !== $user) {
						self::copy($rootView, $owner . '/files_versions' . $v['path'] . '.v' . $v['version'], $owner . '/files_trashbin/versions/' . $v['name'] . '.v' . $v['version'] . '.d' . $timestamp);
					}
					self::move($rootView, $owner . '/files_versions' . $v['path'] . '.v' . $v['version'], $user . '/files_trashbin/versions/' . $filename . '.v' . $v['version'] . '.d' . $timestamp);
				}
			}
		}
	}

	/**
	 * Move a file or folder on storage level
	 *
	 * @param View $view
	 * @param string $source
	 * @param string $target
	 * @return bool
	 */
	private static function move(View $view, $source, $target) {
		/** @var \OC\Files\Storage\Storage $sourceStorage */
		[$sourceStorage, $sourceInternalPath] = $view->resolvePath($source);
		/** @var \OC\Files\Storage\Storage $targetStorage */
		[$targetStorage, $targetInternalPath] = $view->resolvePath($target);
		/** @var \OC\Files\Storage\Storage $ownerTrashStorage */

		$result = $targetStorage->moveFromStorage($sourceStorage, $sourceInternalPath, $targetInternalPath);
		if ($result) {
			$targetStorage->getUpdater()->renameFromStorage($sourceStorage, $sourceInternalPath, $targetInternalPath);
		}
		return $result;
	}

	/**
	 * Copy a file or folder on storage level
	 *
	 * @param View $view
	 * @param string $source
	 * @param string $target
	 * @return bool
	 */
	private static function copy(View $view, $source, $target) {
		/** @var \OC\Files\Storage\Storage $sourceStorage */
		[$sourceStorage, $sourceInternalPath] = $view->resolvePath($source);
		/** @var \OC\Files\Storage\Storage $targetStorage */
		[$targetStorage, $targetInternalPath] = $view->resolvePath($target);
		/** @var \OC\Files\Storage\Storage $ownerTrashStorage */

		$result = $targetStorage->copyFromStorage($sourceStorage, $sourceInternalPath, $targetInternalPath);
		if ($result) {
			$targetStorage->getUpdater()->update($targetInternalPath);
		}
		return $result;
	}

	/**
	 * Restore a file or folder from trash bin
	 *
	 * @param string $file path to the deleted file/folder relative to "files_trashbin/files/",
	 * including the timestamp suffix ".d12345678"
	 * @param string $filename name of the file/folder
	 * @param int $timestamp time when the file/folder was deleted
	 *
	 * @return bool true on success, false otherwise
	 */
	public static function restore($file, $filename, $timestamp) {
		$user = User::getUser();
		$view = new View('/' . $user);

		$location = '';
		if ($timestamp) {
			$location = self::getLocation($user, $filename, $timestamp);
			if ($location === false) {
				\OC::$server->getLogger()->error('trash bin database inconsistent! ($user: ' . $user . ' $filename: ' . $filename . ', $timestamp: ' . $timestamp . ')', ['app' => 'files_trashbin']);
			} else {
				// if location no longer exists, restore file in the root directory
				if ($location !== '/' &&
					(!$view->is_dir('files/' . $location) ||
						!$view->isCreatable('files/' . $location))
				) {
					$location = '';
				}
			}
		}

		// we need a  extension in case a file/dir with the same name already exists
		$uniqueFilename = self::getUniqueFilename($location, $filename, $view);

		$source = Filesystem::normalizePath('files_trashbin/files/' . $file);
		$target = Filesystem::normalizePath('files/' . $location . '/' . $uniqueFilename);
		if (!$view->file_exists($source)) {
			return false;
		}
		$mtime = $view->filemtime($source);

		// restore file
		if (!$view->isCreatable(dirname($target))) {
			throw new NotPermittedException("Can't restore trash item because the target folder is not writable");
		}
		$restoreResult = $view->rename($source, $target);

		// handle the restore result
		if ($restoreResult) {
			$fakeRoot = $view->getRoot();
			$view->chroot('/' . $user . '/files');
			$view->touch('/' . $location . '/' . $uniqueFilename, $mtime);
			$view->chroot($fakeRoot);
			\OCP\Util::emitHook('\OCA\Files_Trashbin\Trashbin', 'post_restore', ['filePath' => Filesystem::normalizePath('/' . $location . '/' . $uniqueFilename),
				'trashPath' => Filesystem::normalizePath($file)]);

			self::restoreVersions($view, $file, $filename, $uniqueFilename, $location, $timestamp);

			if ($timestamp) {
				$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
				$query->delete('files_trash')
					->where($query->expr()->eq('user', $query->createNamedParameter($user)))
					->andWhere($query->expr()->eq('id', $query->createNamedParameter($filename)))
					->andWhere($query->expr()->eq('timestamp', $query->createNamedParameter($timestamp)));
				$query->execute();
			}

			return true;
		}

		return false;
	}

	/**
	 * restore versions from trash bin
	 *
	 * @param View $view file view
	 * @param string $file complete path to file
	 * @param string $filename name of file once it was deleted
	 * @param string $uniqueFilename new file name to restore the file without overwriting existing files
	 * @param string $location location if file
	 * @param int $timestamp deletion time
	 * @return false|null
	 */
	private static function restoreVersions(View $view, $file, $filename, $uniqueFilename, $location, $timestamp) {
		if (\OCP\App::isEnabled('files_versions')) {
			$user = User::getUser();
			$rootView = new View('/');

			$target = Filesystem::normalizePath('/' . $location . '/' . $uniqueFilename);

			[$owner, $ownerPath] = self::getUidAndFilename($target);

			// file has been deleted in between
			if (empty($ownerPath)) {
				return false;
			}

			if ($timestamp) {
				$versionedFile = $filename;
			} else {
				$versionedFile = $file;
			}

			if ($view->is_dir('/files_trashbin/versions/' . $file)) {
				$rootView->rename(Filesystem::normalizePath($user . '/files_trashbin/versions/' . $file), Filesystem::normalizePath($owner . '/files_versions/' . $ownerPath));
			} elseif ($versions = self::getVersionsFromTrash($versionedFile, $timestamp, $user)) {
				foreach ($versions as $v) {
					if ($timestamp) {
						$rootView->rename($user . '/files_trashbin/versions/' . $versionedFile . '.v' . $v . '.d' . $timestamp, $owner . '/files_versions/' . $ownerPath . '.v' . $v);
					} else {
						$rootView->rename($user . '/files_trashbin/versions/' . $versionedFile . '.v' . $v, $owner . '/files_versions/' . $ownerPath . '.v' . $v);
					}
				}
			}
		}
	}

	/**
	 * delete all files from the trash
	 */
	public static function deleteAll() {
		$user = User::getUser();
		$userRoot = \OC::$server->getUserFolder($user)->getParent();
		$view = new View('/' . $user);
		$fileInfos = $view->getDirectoryContent('files_trashbin/files');

		try {
			$trash = $userRoot->get('files_trashbin');
		} catch (NotFoundException $e) {
			return false;
		}

		// Array to store the relative path in (after the file is deleted, the view won't be able to relativise the path anymore)
		$filePaths = [];
		foreach ($fileInfos as $fileInfo) {
			$filePaths[] = $view->getRelativePath($fileInfo->getPath());
		}
		unset($fileInfos); // save memory

		// Bulk PreDelete-Hook
		\OC_Hook::emit('\OCP\Trashbin', 'preDeleteAll', ['paths' => $filePaths]);

		// Single-File Hooks
		foreach ($filePaths as $path) {
			self::emitTrashbinPreDelete($path);
		}

		// actual file deletion
		$trash->delete();

		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
		$query->delete('files_trash')
			->where($query->expr()->eq('user', $query->createNamedParameter($user)));
		$query->execute();

		// Bulk PostDelete-Hook
		\OC_Hook::emit('\OCP\Trashbin', 'deleteAll', ['paths' => $filePaths]);

		// Single-File Hooks
		foreach ($filePaths as $path) {
			self::emitTrashbinPostDelete($path);
		}

		$trash = $userRoot->newFolder('files_trashbin');
		$trash->newFolder('files');

		return true;
	}

	/**
	 * wrapper function to emit the 'preDelete' hook of \OCP\Trashbin before a file is deleted
	 *
	 * @param string $path
	 */
	protected static function emitTrashbinPreDelete($path) {
		\OC_Hook::emit('\OCP\Trashbin', 'preDelete', ['path' => $path]);
	}

	/**
	 * wrapper function to emit the 'delete' hook of \OCP\Trashbin after a file has been deleted
	 *
	 * @param string $path
	 */
	protected static function emitTrashbinPostDelete($path) {
		\OC_Hook::emit('\OCP\Trashbin', 'delete', ['path' => $path]);
	}

	/**
	 * delete file from trash bin permanently
	 *
	 * @param string $filename path to the file
	 * @param string $user
	 * @param int $timestamp of deletion time
	 *
	 * @return int size of deleted files
	 */
	public static function delete($filename, $user, $timestamp = null) {
		$userRoot = \OC::$server->getUserFolder($user)->getParent();
		$view = new View('/' . $user);
		$size = 0;

		if ($timestamp) {
			$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
			$query->delete('files_trash')
				->where($query->expr()->eq('user', $query->createNamedParameter($user)))
				->andWhere($query->expr()->eq('id', $query->createNamedParameter($filename)))
				->andWhere($query->expr()->eq('timestamp', $query->createNamedParameter($timestamp)));
			$query->execute();

			$file = $filename . '.d' . $timestamp;
		} else {
			$file = $filename;
		}

		$size += self::deleteVersions($view, $file, $filename, $timestamp, $user);

		try {
			$node = $userRoot->get('/files_trashbin/files/' . $file);
		} catch (NotFoundException $e) {
			return $size;
		}

		if ($node instanceof Folder) {
			$size += self::calculateSize(new View('/' . $user . '/files_trashbin/files/' . $file));
		} elseif ($node instanceof File) {
			$size += $view->filesize('/files_trashbin/files/' . $file);
		}

		self::emitTrashbinPreDelete('/files_trashbin/files/' . $file);
		$node->delete();
		self::emitTrashbinPostDelete('/files_trashbin/files/' . $file);

		return $size;
	}

	/**
	 * @param View $view
	 * @param string $file
	 * @param string $filename
	 * @param integer|null $timestamp
	 * @param string $user
	 * @return int
	 */
	private static function deleteVersions(View $view, $file, $filename, $timestamp, $user) {
		$size = 0;
		if (\OCP\App::isEnabled('files_versions')) {
			if ($view->is_dir('files_trashbin/versions/' . $file)) {
				$size += self::calculateSize(new View('/' . $user . '/files_trashbin/versions/' . $file));
				$view->unlink('files_trashbin/versions/' . $file);
			} elseif ($versions = self::getVersionsFromTrash($filename, $timestamp, $user)) {
				foreach ($versions as $v) {
					if ($timestamp) {
						$size += $view->filesize('/files_trashbin/versions/' . $filename . '.v' . $v . '.d' . $timestamp);
						$view->unlink('/files_trashbin/versions/' . $filename . '.v' . $v . '.d' . $timestamp);
					} else {
						$size += $view->filesize('/files_trashbin/versions/' . $filename . '.v' . $v);
						$view->unlink('/files_trashbin/versions/' . $filename . '.v' . $v);
					}
				}
			}
		}
		return $size;
	}

	/**
	 * check to see whether a file exists in trashbin
	 *
	 * @param string $filename path to the file
	 * @param int $timestamp of deletion time
	 * @return bool true if file exists, otherwise false
	 */
	public static function file_exists($filename, $timestamp = null) {
		$user = User::getUser();
		$view = new View('/' . $user);

		if ($timestamp) {
			$filename = $filename . '.d' . $timestamp;
		}

		$target = Filesystem::normalizePath('files_trashbin/files/' . $filename);
		return $view->file_exists($target);
	}

	/**
	 * deletes used space for trash bin in db if user was deleted
	 *
	 * @param string $uid id of deleted user
	 * @return bool result of db delete operation
	 */
	public static function deleteUser($uid) {
		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
		$query->delete('files_trash')
			->where($query->expr()->eq('user', $query->createNamedParameter($uid)));
		return (bool) $query->execute();
	}

	/**
	 * calculate remaining free space for trash bin
	 *
	 * @param integer $trashbinSize current size of the trash bin
	 * @param string $user
	 * @return int available free space for trash bin
	 */
	private static function calculateFreeSpace($trashbinSize, $user) {
		$config = \OC::$server->getConfig();
		$userTrashbinSize = (int)$config->getUserValue($user, 'files_trashbin', 'trashbin_size', '-1');
		if ($userTrashbinSize > -1) {
			return $userTrashbinSize - $trashbinSize;
		}
		$systemTrashbinSize = (int)$config->getAppValue('files_trashbin', 'trashbin_size', '-1');
		if ($systemTrashbinSize > -1) {
			return $systemTrashbinSize - $trashbinSize;
		}

		$softQuota = true;
		$userObject = \OC::$server->getUserManager()->get($user);
		if (is_null($userObject)) {
			return 0;
		}
		$quota = $userObject->getQuota();
		if ($quota === null || $quota === 'none') {
			$quota = Filesystem::free_space('/');
			$softQuota = false;
			// inf or unknown free space
			if ($quota < 0) {
				$quota = PHP_INT_MAX;
			}
		} else {
			$quota = \OCP\Util::computerFileSize($quota);
		}

		// calculate available space for trash bin
		// subtract size of files and current trash bin size from quota
		if ($softQuota) {
			$userFolder = \OC::$server->getUserFolder($user);
			if (is_null($userFolder)) {
				return 0;
			}
			$free = $quota - $userFolder->getSize(false); // remaining free space for user
			if ($free > 0) {
				$availableSpace = ($free * self::DEFAULTMAXSIZE / 100) - $trashbinSize; // how much space can be used for versions
			} else {
				$availableSpace = $free - $trashbinSize;
			}
		} else {
			$availableSpace = $quota;
		}

		return $availableSpace;
	}

	/**
	 * resize trash bin if necessary after a new file was added to Nextcloud
	 *
	 * @param string $user user id
	 */
	public static function resizeTrash($user) {
		$size = self::getTrashbinSize($user);

		$freeSpace = self::calculateFreeSpace($size, $user);

		if ($freeSpace < 0) {
			self::scheduleExpire($user);
		}
	}

	/**
	 * clean up the trash bin
	 *
	 * @param string $user
	 */
	public static function expire($user) {
		$trashBinSize = self::getTrashbinSize($user);
		$availableSpace = self::calculateFreeSpace($trashBinSize, $user);

		$dirContent = Helper::getTrashFiles('/', $user, 'mtime');

		// delete all files older then $retention_obligation
		[$delSize, $count] = self::deleteExpiredFiles($dirContent, $user);

		$availableSpace += $delSize;

		// delete files from trash until we meet the trash bin size limit again
		self::deleteFiles(array_slice($dirContent, $count), $user, $availableSpace);
	}

	/**
	 * @param string $user
	 */
	private static function scheduleExpire($user) {
		// let the admin disable auto expire
		/** @var Application $application */
		$application = \OC::$server->query(Application::class);
		$expiration = $application->getContainer()->query('Expiration');
		if ($expiration->isEnabled()) {
			\OC::$server->getCommandBus()->push(new Expire($user));
		}
	}

	/**
	 * if the size limit for the trash bin is reached, we delete the oldest
	 * files in the trash bin until we meet the limit again
	 *
	 * @param array $files
	 * @param string $user
	 * @param int $availableSpace available disc space
	 * @return int size of deleted files
	 */
	protected static function deleteFiles($files, $user, $availableSpace) {
		/** @var Application $application */
		$application = \OC::$server->query(Application::class);
		$expiration = $application->getContainer()->query('Expiration');
		$size = 0;

		if ($availableSpace < 0) {
			foreach ($files as $file) {
				if ($availableSpace < 0 && $expiration->isExpired($file['mtime'], true)) {
					$tmp = self::delete($file['name'], $user, $file['mtime']);
					\OC::$server->getLogger()->info('remove "' . $file['name'] . '" (' . $tmp . 'B) to meet the limit of trash bin size (50% of available quota)', ['app' => 'files_trashbin']);
					$availableSpace += $tmp;
					$size += $tmp;
				} else {
					break;
				}
			}
		}
		return $size;
	}

	/**
	 * delete files older then max storage time
	 *
	 * @param array $files list of files sorted by mtime
	 * @param string $user
	 * @return integer[] size of deleted files and number of deleted files
	 */
	public static function deleteExpiredFiles($files, $user) {
		/** @var Expiration $expiration */
		$expiration = \OC::$server->query(Expiration::class);
		$size = 0;
		$count = 0;
		foreach ($files as $file) {
			$timestamp = $file['mtime'];
			$filename = $file['name'];
			if ($expiration->isExpired($timestamp)) {
				try {
					$size += self::delete($filename, $user, $timestamp);
					$count++;
				} catch (\OCP\Files\NotPermittedException $e) {
					\OC::$server->getLogger()->logException($e, ['app' => 'files_trashbin', 'level' => \OCP\ILogger::WARN, 'message' => 'Removing "' . $filename . '" from trashbin failed.']);
				}
				\OC::$server->getLogger()->info(
					'Remove "' . $filename . '" from trashbin because it exceeds max retention obligation term.',
					['app' => 'files_trashbin']
				);
			} else {
				break;
			}
		}

		return [$size, $count];
	}

	/**
	 * recursive copy to copy a whole directory
	 *
	 * @param string $source source path, relative to the users files directory
	 * @param string $destination destination path relative to the users root directoy
	 * @param View $view file view for the users root directory
	 * @return int
	 * @throws Exceptions\CopyRecursiveException
	 */
	private static function copy_recursive($source, $destination, View $view) {
		$size = 0;
		if ($view->is_dir($source)) {
			$view->mkdir($destination);
			$view->touch($destination, $view->filemtime($source));
			foreach ($view->getDirectoryContent($source) as $i) {
				$pathDir = $source . '/' . $i['name'];
				if ($view->is_dir($pathDir)) {
					$size += self::copy_recursive($pathDir, $destination . '/' . $i['name'], $view);
				} else {
					$size += $view->filesize($pathDir);
					$result = $view->copy($pathDir, $destination . '/' . $i['name']);
					if (!$result) {
						throw new \OCA\Files_Trashbin\Exceptions\CopyRecursiveException();
					}
					$view->touch($destination . '/' . $i['name'], $view->filemtime($pathDir));
				}
			}
		} else {
			$size += $view->filesize($source);
			$result = $view->copy($source, $destination);
			if (!$result) {
				throw new \OCA\Files_Trashbin\Exceptions\CopyRecursiveException();
			}
			$view->touch($destination, $view->filemtime($source));
		}
		return $size;
	}

	/**
	 * find all versions which belong to the file we want to restore
	 *
	 * @param string $filename name of the file which should be restored
	 * @param int $timestamp timestamp when the file was deleted
	 * @return array
	 */
	private static function getVersionsFromTrash($filename, $timestamp, $user) {
		$view = new View('/' . $user . '/files_trashbin/versions');
		$versions = [];

		/** @var \OC\Files\Storage\Storage $storage */
		[$storage,] = $view->resolvePath('/');

		//force rescan of versions, local storage may not have updated the cache
		if (!self::$scannedVersions) {
			$storage->getScanner()->scan('files_trashbin/versions');
			self::$scannedVersions = true;
		}

		$pattern = \OC::$server->getDatabaseConnection()->escapeLikeParameter(basename($filename));
		if ($timestamp) {
			// fetch for old versions
			$escapedTimestamp = \OC::$server->getDatabaseConnection()->escapeLikeParameter($timestamp);
			$pattern .= '.v%.d' . $escapedTimestamp;
			$offset = -strlen($escapedTimestamp) - 2;
		} else {
			$pattern .= '.v%';
		}

		// Manually fetch all versions from the file cache to be able to filter them by their parent
		$cache = $storage->getCache('');
		$query = new CacheQueryBuilder(
			\OC::$server->getDatabaseConnection(),
			\OC::$server->getSystemConfig(),
			\OC::$server->getLogger(),
			$cache
		);
		$normalizedParentPath = ltrim(Filesystem::normalizePath(dirname('files_trashbin/versions/'. $filename)), '/');
		$parentId = $cache->getId($normalizedParentPath);
		if ($parentId === -1) {
			return [];
		}

		$query->selectFileCache()
			->whereStorageId()
			->andWhere($query->expr()->eq('parent', $query->createNamedParameter($parentId)))
			->andWhere($query->expr()->iLike('name', $query->createNamedParameter($pattern)));

		/** @var CacheEntry[] $matches */
		$matches = array_map(function (array $data) {
			return Cache::cacheEntryFromData($data, \OC::$server->getMimeTypeLoader());
		}, $query->execute()->fetchAll());

		foreach ($matches as $ma) {
			if ($timestamp) {
				$parts = explode('.v', substr($ma['path'], 0, $offset));
				$versions[] = end($parts);
			} else {
				$parts = explode('.v', $ma['path']);
				$versions[] = end($parts);
			}
		}

		return $versions;
	}

	/**
	 * find unique extension for restored file if a file with the same name already exists
	 *
	 * @param string $location where the file should be restored
	 * @param string $filename name of the file
	 * @param View $view filesystem view relative to users root directory
	 * @return string with unique extension
	 */
	private static function getUniqueFilename($location, $filename, View $view) {
		$ext = pathinfo($filename, PATHINFO_EXTENSION);
		$name = pathinfo($filename, PATHINFO_FILENAME);
		$l = \OC::$server->getL10N('files_trashbin');

		$location = '/' . trim($location, '/');

		// if extension is not empty we set a dot in front of it
		if ($ext !== '') {
			$ext = '.' . $ext;
		}

		if ($view->file_exists('files' . $location . '/' . $filename)) {
			$i = 2;
			$uniqueName = $name . " (" . $l->t("restored") . ")" . $ext;
			while ($view->file_exists('files' . $location . '/' . $uniqueName)) {
				$uniqueName = $name . " (" . $l->t("restored") . " " . $i . ")" . $ext;
				$i++;
			}

			return $uniqueName;
		}

		return $filename;
	}

	/**
	 * get the size from a given root folder
	 *
	 * @param View $view file view on the root folder
	 * @return integer size of the folder
	 */
	private static function calculateSize($view) {
		$root = \OC::$server->getConfig()->getSystemValue('datadirectory', \OC::$SERVERROOT . '/data') . $view->getAbsolutePath('');
		if (!file_exists($root)) {
			return 0;
		}
		$iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($root), \RecursiveIteratorIterator::CHILD_FIRST);
		$size = 0;

		/**
		 * RecursiveDirectoryIterator on an NFS path isn't iterable with foreach
		 * This bug is fixed in PHP 5.5.9 or before
		 * See #8376
		 */
		$iterator->rewind();
		while ($iterator->valid()) {
			$path = $iterator->current();
			$relpath = substr($path, strlen($root) - 1);
			if (!$view->is_dir($relpath)) {
				$size += $view->filesize($relpath);
			}
			$iterator->next();
		}
		return $size;
	}

	/**
	 * get current size of trash bin from a given user
	 *
	 * @param string $user user who owns the trash bin
	 * @return integer trash bin size
	 */
	private static function getTrashbinSize($user) {
		$view = new View('/' . $user);
		$fileInfo = $view->getFileInfo('/files_trashbin');
		return isset($fileInfo['size']) ? $fileInfo['size'] : 0;
	}

	/**
	 * check if trash bin is empty for a given user
	 *
	 * @param string $user
	 * @return bool
	 */
	public static function isEmpty($user) {
		$view = new View('/' . $user . '/files_trashbin');
		if ($view->is_dir('/files') && $dh = $view->opendir('/files')) {
			while ($file = readdir($dh)) {
				if (!Filesystem::isIgnoredDir($file)) {
					return false;
				}
			}
		}
		return true;
	}

	/**
	 * @param $path
	 * @return string
	 */
	public static function preview_icon($path) {
		return \OC::$server->getURLGenerator()->linkToRoute('core_ajax_trashbin_preview', ['x' => 32, 'y' => 32, 'file' => $path]);
	}
}