<?php
/**
 * @author Adam Williamson <awilliam@redhat.com>
 * @author Andreas Fischer <bantu@owncloud.com>
 * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
 * @author Bart Visscher <bartv@thisnet.nl>
 * @author Bernhard Posselt <dev@bernhard-posselt.com>
 * @author Birk Borkason <daniel.niccoli@gmail.com>
 * @author Björn Schießle <bjoern@schiessle.org>
 * @author Brice Maron <brice@bmaron.net>
 * @author Christopher Schäpers <kondou@ts.unde.re>
 * @author Christoph Wurst <christoph@owncloud.com>
 * @author Clark Tomlinson <fallen013@gmail.com>
 * @author cmeh <cmeh@users.noreply.github.com>
 * @author Florin Peter <github@florin-peter.de>
 * @author Frank Karlitschek <frank@karlitschek.de>
 * @author Georg Ehrke <georg@owncloud.com>
 * @author helix84 <helix84@centrum.sk>
 * @author Individual IT Services <info@individual-it.net>
 * @author Jakob Sack <mail@jakobsack.de>
 * @author Joas Schilling <coding@schilljs.com>
 * @author Jörn Friedrich Dreyer <jfd@butonic.de>
 * @author Kawohl <john@owncloud.com>
 * @author Lukas Reschke <lukas@statuscode.ch>
 * @author Markus Goetz <markus@woboq.com>
 * @author Martin Mattel <martin.mattel@diemattels.at>
 * @author Marvin Thomas Rabe <mrabe@marvinrabe.de>
 * @author Michael Gapczynski <GapczynskiM@gmail.com>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Philipp Schaffrath <github@philippschaffrath.de>
 * @author Robin Appelman <icewind@owncloud.com>
 * @author Robin McCorkell <robin@mccorkell.me.uk>
 * @author Roeland Jago Douma <rullzer@owncloud.com>
 * @author Stefan Rado <owncloud@sradonia.net>
 * @author Stefan Weil <sw@weilnetz.de>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 * @author Thomas Tanghus <thomas@tanghus.net>
 * @author Victor Dubiniuk <dubiniuk@owncloud.com>
 * @author Vincent Petry <pvince81@owncloud.com>
 * @author Volkan Gezer <volkangezer@gmail.com>
 *
 * @copyright Copyright (c) 2018, ownCloud GmbH
 * @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/>
 *
 */

use OC\Security\SignedUrl\Verifier;
use OC\User\LoginException;
use OCP\Authentication\Exceptions\AccountCheckException;
use OCP\Files\NoReadAccessException;
use OCP\IUser;
use OCP\License\ILicenseManager;

class OC_Util {
	public static $scripts = [];
	public static $styles = [];
	public static $headers = [];
	private static $rootMounted = false;
	private static $fsSetup = false;
	private static $version;
	public const EDITION_COMMUNITY = 'Community';
	public const EDITION_ENTERPRISE = 'Enterprise';

	protected static function getAppManager() {
		return \OC::$server->getAppManager();
	}

	private static function initLocalStorageRootFS() {
		// mount local file backend as root
		$configDataDirectory = \OC::$server->getSystemConfig()->getValue("datadirectory", OC::$SERVERROOT . "/data");
		//first set up the local "root" storage
		\OC\Files\Filesystem::initMountManager();
		if (!self::$rootMounted) {
			\OC\Files\Filesystem::mount('\OC\Files\Storage\Local', ['datadir' => $configDataDirectory], '/');
			self::$rootMounted = true;
		}
	}

	/**
	 * mounting an object storage as the root fs will in essence remove the
	 * necessity of a data folder being present.
	 * TODO make home storage aware of this and use the object storage instead of local disk access
	 *
	 * @param array $config containing 'class' and optional 'arguments'
	 */
	private static function initObjectStoreRootFS($config) {
		// check misconfiguration
		if (empty($config['class'])) {
			\OCP\Util::writeLog('files', 'No class given for objectstore', \OCP\Util::ERROR);
		}
		if (!isset($config['arguments'])) {
			$config['arguments'] = [];
		}

		// instantiate object store implementation
		$name = $config['class'];
		if (\strpos($name, 'OCA\\') === 0 && \substr_count($name, '\\') >= 2) {
			$segments = \explode('\\', $name);
			OC_App::loadApp(\strtolower($segments[1]));
		}
		$config['arguments']['objectstore'] = new $config['class']($config['arguments']);
		// mount with plain / root object store implementation
		$config['class'] = '\OC\Files\ObjectStore\ObjectStoreStorage';

		// mount object storage as root
		\OC\Files\Filesystem::initMountManager();
		if (!self::$rootMounted) {
			\OC\Files\Filesystem::mount($config['class'], $config['arguments'], '/');
			self::$rootMounted = true;
		}
	}

	/**
	 * Can be set up
	 *
	 * @param string $user
	 * @return boolean
	 * @description configure the initial filesystem based on the configuration
	 */
	public static function setupFS($user = '', $fullInit = true) {
		//setting up the filesystem twice can only lead to trouble
		if (self::$fsSetup) {
			return false;
		}

		\OC::$server->getEventLogger()->start('setup_fs', 'Setup filesystem');

		// If we are not forced to load a specific user we load the one that is logged in
		if ($user === null) {
			$user = '';
		} elseif ($user == "" && OC_User::isLoggedIn()) {
			$user = OC_User::getUser();
		}

		// load all filesystem apps before, so no setup-hook gets lost
		OC_App::loadApps(['filesystem']);

		// the filesystem will finish when $user is not empty,
		// mark fs setup here to avoid doing the setup from loading
		// OC_Filesystem
		if ($user != '') {
			self::$fsSetup = true;
		}

		\OC\Files\Filesystem::initMountManager();

		\OC\Files\Filesystem::logWarningWhenAddingStorageWrapper(false);
		\OC\Files\Filesystem::addStorageWrapper('mount_options', function ($mountPoint, \OCP\Files\Storage $storage, \OCP\Files\Mount\IMountPoint $mount) {
			if ($storage->instanceOfStorage('\OC\Files\Storage\Common')) {
				/** @var \OC\Files\Storage\Common $storage */
				'@phan-var \OC\Files\Storage\Common $storage';
				$storage->setMountOptions($mount->getOptions());
			}
			return $storage;
		});

		\OC\Files\Filesystem::addStorageWrapper('enable_sharing', function ($mountPoint, \OCP\Files\Storage $storage, \OCP\Files\Mount\IMountPoint $mount) {
			if (!$mount->getOption('enable_sharing', true)) {
				return new \OC\Files\Storage\Wrapper\PermissionsMask([
					'storage' => $storage,
					'mask' => \OCP\Constants::PERMISSION_ALL - \OCP\Constants::PERMISSION_SHARE
				]);
			}
			return $storage;
		});

		\OC\Files\Filesystem::addStorageWrapper('read_only', function ($mountPoint, \OCP\Files\Storage $storage, \OCP\Files\Mount\IMountPoint $mount) {
			if ($mount->getOption('read_only', false)) {
				return new \OC\Files\Storage\Wrapper\PermissionsMask([
					'storage' => $storage,
					'mask' => \OCP\Constants::PERMISSION_READ | \OCP\Constants::PERMISSION_SHARE
				]);
			}
			return $storage;
		});

		// install storage availability wrapper, before most other wrappers
		\OC\Files\Filesystem::addStorageWrapper('oc_availability', function ($mountPoint, $storage) {
			if (!$storage->instanceOfStorage('\OCA\Files_Sharing\SharedStorage') && !$storage->isLocal()) {
				return new \OC\Files\Storage\Wrapper\Availability(['storage' => $storage]);
			}
			return $storage;
		});

		// install storage checksum wrapper
		\OC\Files\Filesystem::addStorageWrapper('oc_checksum', function ($mountPoint, \OCP\Files\Storage\IStorage $storage) {
			if (!$storage->instanceOfStorage('\OCA\Files_Sharing\SharedStorage')) {
				return new \OC\Files\Storage\Wrapper\Checksum(['storage' => $storage]);
			}

			return $storage;
		}, 1);

		\OC\Files\Filesystem::addStorageWrapper('oc_encoding', function ($mountPoint, \OCP\Files\Storage $storage, \OCP\Files\Mount\IMountPoint $mount) {
			if ($mount->getOption('encoding_compatibility', false) && !$storage->instanceOfStorage('\OCA\Files_Sharing\SharedStorage') && !$storage->isLocal()) {
				return new \OC\Files\Storage\Wrapper\Encoding(['storage' => $storage]);
			}
			return $storage;
		});

		\OC\Files\Filesystem::addStorageWrapper('oc_quota', function ($mountPoint, $storage) {
			// set up quota for home storages, even for other users
			// which can happen when using sharing

			/**
			 * @var \OC\Files\Storage\Storage $storage
			 */
			if ($storage->instanceOfStorage('\OC\Files\Storage\Home')
				|| $storage->instanceOfStorage('\OC\Files\ObjectStore\HomeObjectStoreStorage')
			) {
				/** @var \OC\Files\Storage\Home $storage */
				if (\is_object($storage->getUser())) {
					$user = $storage->getUser()->getUID();
					$quota = OC_Util::getUserQuota($user);
					if ($quota !== \OCP\Files\FileInfo::SPACE_UNLIMITED) {
						return new \OC\Files\Storage\Wrapper\Quota([
							'mountPoint' => $mountPoint,
							'storage' => $storage,
							'quota' => $quota,
							'root' => 'files'
						]);
					}
				}
			}

			return $storage;
		});

		OC_Hook::emit('OC_Filesystem', 'preSetup', ['user' => $user]);
		\OC\Files\Filesystem::logWarningWhenAddingStorageWrapper(true);

		// Make users storage readonly if he is a guest or in a read_only group

		$isGuest = \OC::$server->getConfig()->getUserValue(
			$user,
			'owncloud',
			'isGuest',
			false
		);

		if (!$isGuest) {
			$readOnlyGroups = \json_decode(\OC::$server->getConfig()->getAppValue(
				'core',
				'read_only_groups',
				'[]'
			), true);

			if (!\is_array($readOnlyGroups)) {
				$readOnlyGroups = [];
			}
			$readOnlyGroupMemberships = [];
			if ($readOnlyGroups) {
				$userGroups = \array_keys(
					\OC::$server->getGroupManager()->getUserIdGroups($user)
				);

				$readOnlyGroupMemberships = \array_intersect(
					$readOnlyGroups,
					$userGroups
				);
			}
		}

		if ($isGuest === '1' || !empty($readOnlyGroupMemberships)) {
			\OC\Files\Filesystem::addStorageWrapper(
				'oc_readonly',
				function ($mountPoint, $storage) use ($user) {
					if ($mountPoint === '/' || $mountPoint === "/$user/") {
						return new \OC\Files\Storage\Wrapper\ReadOnlyJail(
							[
								'storage' => $storage,
								'mask' => \OCP\Constants::PERMISSION_READ,
								'path' => 'files'
							]
						);
					}

					return $storage;
				}
			);
		}

		//check if we are using an object storage
		$objectStore = \OC::$server->getSystemConfig()->getValue('objectstore', null);
		$objectStore = \OC::$server->getSystemConfig()->getValue('objectstore_multibucket', $objectStore);
		if (isset($objectStore)) {
			self::initObjectStoreRootFS($objectStore);
		} else {
			self::initLocalStorageRootFS();
		}

		if ($user != '' && !OCP\User::userExists($user)) {
			\OC::$server->getEventLogger()->end('setup_fs');
			return false;
		}

		//if we aren't logged in, there is no use to set up the filesystem
		if ($user != "") {
			$userDir = '/' . $user . '/files';

			//jail the user into his "home" directory
			\OC\Files\Filesystem::init($user, $userDir, $fullInit);

			OC_Hook::emit('OC_Filesystem', 'setup', ['user' => $user, 'user_dir' => $userDir]);
		}
		\OC::$server->getEventLogger()->end('setup_fs');
		return true;
	}

	/**
	 * check if a password is required for each public link.
	 * This is deprecated due to not reflecting all the possibilities now. Falling back to
	 * enforce password for read-only links. Note that read & write or write-only options won't
	 * be considered here
	 *
	 * @return boolean
	 * @deprecated
	 */
	public static function isPublicLinkPasswordRequired() {
		$appConfig = \OC::$server->getAppConfig();
		$enforcePassword = $appConfig->getValue('core', 'shareapi_enforce_links_password_read_only', 'no');
		return ($enforcePassword === 'yes') ? true : false;
	}

	/**
	 * check if share API enforces a default expire date
	 *
	 * @return boolean
	 */
	public static function isDefaultExpireDateEnforced() {
		$isDefaultExpireDateEnabled = \OC::$server->getConfig()->getAppValue('core', 'shareapi_default_expire_date', 'no');
		$enforceDefaultExpireDate = false;
		if ($isDefaultExpireDateEnabled === 'yes') {
			$value = \OC::$server->getConfig()->getAppValue('core', 'shareapi_enforce_expire_date', 'no');
			$enforceDefaultExpireDate = ($value === 'yes') ? true : false;
		}

		return $enforceDefaultExpireDate;
	}

	/**
	 * Get the quota of a user
	 *
	 * @param string|IUser $userId
	 * @return int Quota bytes
	 */
	public static function getUserQuota($userId) {
		if ($userId instanceof IUser) {
			$user = $userId;
		} else {
			$user = \OC::$server->getUserManager()->get($userId);
		}
		if ($user === null) {
			return \OCP\Files\FileInfo::SPACE_UNLIMITED;
		}
		$userQuota = $user->getQuota();
		if ($userQuota === null || $userQuota === 'default') {
			$userQuota = \OC::$server->getConfig()->getAppValue('files', 'default_quota', 'none');
		}
		if ($userQuota === null || $userQuota === 'none') {
			return \OCP\Files\FileInfo::SPACE_UNLIMITED;
		}
		return OC_Helper::computerFileSize($userQuota);
	}

	/**
	 * copies the skeleton to the users /files
	 *
	 * @param String $userId
	 * @param \OCP\Files\Folder $userDirectory
	 * @throws \OC\HintException
	 */
	public static function copySkeleton($userId, \OCP\Files\Folder $userDirectory) {
		$skeletonDirectory = \OC::$server->getConfig()->getSystemValue('skeletondirectory', \OC::$SERVERROOT . '/core/skeleton');

		// An empty setting for skeletondirectory means that no skeleton is required.
		if ($skeletonDirectory === '') {
			return;
		}

		if (!\is_dir($skeletonDirectory)) {
			throw new \OC\HintException('The skeleton folder '.$skeletonDirectory.' is not accessible');
		}

		if (!empty($skeletonDirectory)) {
			\OCP\Util::writeLog(
				'files_skeleton',
				'copying skeleton for '.$userId.' from '.$skeletonDirectory.' to '.$userDirectory->getFullPath('/'),
				\OCP\Util::DEBUG
			);
			self::copyr($skeletonDirectory, $userDirectory);
			// update the file cache
			$userDirectory->getStorage()->getScanner()->scan('', \OC\Files\Cache\Scanner::SCAN_RECURSIVE);
		}
	}

	/**
	 * copies a directory recursively by using streams
	 *
	 * @param string $source
	 * @param \OCP\Files\Folder $target
	 * @return void
	 * @throws NoReadAccessException
	 */
	public static function copyr($source, \OCP\Files\Folder $target) {
		$dir = @\opendir($source);
		if ($dir === false) {
			throw new NoReadAccessException('No read permission for folder ' . $source);
		}
		while (($file = \readdir($dir)) !== false) {
			if (!\OC\Files\Filesystem::isIgnoredDir($file)) {
				if (\is_dir($source . '/' . $file)) {
					$child = $target->newFolder($file);
					self::copyr($source . '/' . $file, $child);
				} else {
					$sourceFileHandle = @\fopen($source . '/' . $file, 'r');
					if ($sourceFileHandle === false) {
						throw new NoReadAccessException('No read permission for file ' . $file);
					}
					$child = $target->newFile($file);
					$targetFileHandle = $child->fopen('w');
					\stream_copy_to_stream($sourceFileHandle, $targetFileHandle);
					\fclose($targetFileHandle);
					\fclose($sourceFileHandle);

					// update cache sizes
					$cache = $target->getStorage()->getCache();
					if ($cache instanceof \OC\Files\Cache\Cache) {
						$cache->correctFolderSize($child->getInternalPath());
					}
				}
			}
		}
		\closedir($dir);
	}

	/**
	 * @return void
	 */
	public static function tearDownFS() {
		\OC\Files\Filesystem::tearDown();
		self::$fsSetup = false;
		self::$rootMounted = false;
	}

	/**
	 * get the current installed version of ownCloud
	 *
	 * @return array
	 */
	public static function getVersion() {
		OC_Util::loadVersion();
		return self::$version['OC_Version'];
	}

	/**
	 * get the current installed version string of ownCloud
	 *
	 * @return string
	 */
	public static function getVersionString() {
		OC_Util::loadVersion();
		return self::$version['OC_VersionString'];
	}

	/**
	 * @description get the current installed edition of ownCloud.
	 * There is the community edition that returns "Community" and
	 * the enterprise edition that returns "Enterprise".
	 * @return string
	 */
	public static function getEditionString() {
		$licenseManager = \OC::$server->getLicenseManager();
		// TODO: Need to open method in the licenseManager to expose the license type
		$licenseMessage = $licenseManager->getLicenseMessageFor('core');
		$licenseState = $licenseMessage['license_state'];
		$licenseType = $licenseMessage['type'];
		if ($licenseState !== ILicenseManager::LICENSE_STATE_MISSING &&
			$licenseState !== ILicenseManager::LICENSE_STATE_INVALID
		) {
			// if it's a expired demo key, we need to return community
			if ($licenseState === ILicenseManager::LICENSE_STATE_EXPIRED && $licenseType !== 0) {
				/**
				 * TODO: licenseType === 0 is documented as "normal" license in the
				 * ILicenseManager::getLicenseMessageFor method
				 * This needs to be properly exposed as constant by the ILicenseManager
				 */
				return OC_Util::EDITION_COMMUNITY;
			}
			return OC_Util::EDITION_ENTERPRISE;
		} else {
			return OC_Util::EDITION_COMMUNITY;
		}
	}

	/**
	 * @description get the update channel of the current installed of ownCloud.
	 * @return string
	 */
	public static function getChannel() {
		OC_Util::loadVersion();
		return self::$version['OC_Channel'];
	}

	/**
	 * @description get the build number of the current installed of ownCloud.
	 * @return string
	 */
	public static function getBuild() {
		OC_Util::loadVersion();
		return self::$version['OC_Build'];
	}

	/**
	 * @description load the version.php into the session as cache
	 */
	private static function loadVersion() {
		require __DIR__ . '/../../../version.php';
		/** @var $OC_Version string */
		/** @var $OC_VersionString string */
		/** @var $OC_Build string */
		/** @var $OC_Channel string */
		self::$version = [
			'OC_Version' => $OC_Version,
			'OC_VersionString' => $OC_VersionString,
			'OC_Build' => $OC_Build,
			'OC_Channel' => $OC_Channel,
		];

		// Allow overriding update channel

		if (\OC::$server->getSystemConfig()->getValue('installed', false)) {
			$channel = \OC::$server->getConfig()->getAppValue('core', 'OC_Channel', $OC_Channel);
			self::$version['OC_Channel'] = $channel;
		}
	}

	/**
	 * generates a path for JS/CSS files. If no application is provided it will create the path for core.
	 *
	 * @param string $application application to get the files from
	 * @param string $directory directory within this application (css, js, vendor, etc)
	 * @param string $file the file inside of the above folder
	 * @return string the path
	 */
	private static function generatePath($application, $directory, $file) {
		if ($file === null) {
			$file = $application;
			$application = "";
		}
		if (!empty($application)) {
			return "$application/$directory/$file";
		} else {
			return "$directory/$file";
		}
	}

	/**
	 * add a javascript file
	 *
	 * @param string $application application id
	 * @param string|null $file filename
	 * @param bool $prepend prepend the Script to the beginning of the list
	 * @return void
	 */
	public static function addScript($application, $file = null, $prepend = false) {
		$path = OC_Util::generatePath($application, 'js', $file);

		// core js files need separate handling
		if ($application !== 'core' && $file !== null) {
			self::addTranslations($application);
		}
		self::addExternalResource($application, $prepend, $path, "script");
	}

	/**
	 * add a javascript file from the vendor sub folder
	 *
	 * @param string $application application id
	 * @param string|null $file filename
	 * @param bool $prepend prepend the Script to the beginning of the list
	 * @return void
	 */
	public static function addVendorScript($application, $file = null, $prepend = false) {
		$path = OC_Util::generatePath($application, 'vendor', $file);
		self::addExternalResource($application, $prepend, $path, "script");
	}

	/**
	 * add a translation JS file
	 *
	 * @param string $application application id
	 * @param string $languageCode language code, defaults to the current language
	 * @param bool $prepend prepend the Script to the beginning of the list
	 */
	public static function addTranslations($application, $languageCode = null, $prepend = false) {
		if ($languageCode === null) {
			$languageCode = \OC::$server->getL10NFactory()->findLanguage($application);
		}
		if (!empty($application)) {
			$path = "$application/l10n/$languageCode";
		} else {
			$path = "l10n/$languageCode";
		}
		self::addExternalResource($application, $prepend, $path, "script");
	}

	/**
	 * add a css file
	 *
	 * @param string $application application id
	 * @param string|null $file filename
	 * @param bool $prepend prepend the Style to the beginning of the list
	 * @return void
	 */
	public static function addStyle($application, $file = null, $prepend = false) {
		$path = OC_Util::generatePath($application, 'css', $file);
		self::addExternalResource($application, $prepend, $path, "style");
	}

	/**
	 * add a css file from the vendor sub folder
	 *
	 * @param string $application application id
	 * @param string|null $file filename
	 * @param bool $prepend prepend the Style to the beginning of the list
	 * @return void
	 */
	public static function addVendorStyle($application, $file = null, $prepend = false) {
		$path = OC_Util::generatePath($application, 'vendor', $file);
		self::addExternalResource($application, $prepend, $path, "style");
	}

	/**
	 * add an external resource css/js file
	 *
	 * @param string $application application id
	 * @param bool $prepend prepend the file to the beginning of the list
	 * @param string $path
	 * @param string $type (script or style)
	 * @return void
	 */
	private static function addExternalResource($application, $prepend, $path, $type = "script") {
		if ($type === "style") {
			if (!\in_array($path, self::$styles)) {
				if ($prepend === true) {
					\array_unshift(self::$styles, $path);
				} else {
					self::$styles[] = $path;
				}
			}
		} elseif ($type === "script") {
			if (!\in_array($path, self::$scripts)) {
				if ($prepend === true) {
					\array_unshift(self::$scripts, $path);
				} else {
					self::$scripts [] = $path;
				}
			}
		}
	}

	/**
	 * Add a custom element to the header
	 * If $text is null then the element will be written as empty element.
	 * So use "" to get a closing tag.
	 * @param string $tag tag name of the element
	 * @param array $attributes array of attributes for the element
	 * @param string $text the text content for the element
	 */
	public static function addHeader($tag, $attributes, $text=null) {
		self::$headers[] = [
			'tag' => $tag,
			'attributes' => $attributes,
			'text' => $text
		];
	}

	/**
	 * formats a timestamp in the "right" way
	 *
	 * @param int $timestamp
	 * @param bool $dateOnly option to omit time from the result
	 * @param DateTimeZone|string $timeZone where the given timestamp shall be converted to
	 * @return string timestamp
	 *
	 * @deprecated Use \OC::$server->query('DateTimeFormatter') instead
	 */
	public static function formatDate($timestamp, $dateOnly = false, $timeZone = null) {
		if ($timeZone !== null && !$timeZone instanceof \DateTimeZone) {
			$timeZone = new \DateTimeZone($timeZone);
		}

		/** @var \OC\DateTimeFormatter $formatter */
		$formatter = \OC::$server->query('DateTimeFormatter');
		if ($dateOnly) {
			return $formatter->formatDate($timestamp, 'long', $timeZone);
		}
		return $formatter->formatDateTime($timestamp, 'long', 'long', $timeZone);
	}

	/**
	 * check if the current server configuration is suitable for ownCloud
	 *
	 * @param \OCP\IConfig $config
	 * @return array arrays with error messages and hints
	 */
	public static function checkServer(\OCP\IConfig $config) {
		$l = \OC::$server->getL10N('lib');
		$errors = [];
		$CONFIG_DATADIRECTORY = $config->getSystemValue('datadirectory', OC::$SERVERROOT . '/data');

		if (!self::needUpgrade($config) && $config->getSystemValue('installed', false)) {
			// this check needs to be done every time
			$errors = self::checkDataDirectoryValidity($CONFIG_DATADIRECTORY);
		}

		// Assume that if checkServer() succeeded before in this session, then all is fine.
		if (\OC::$server->getSession()->exists('checkServer_succeeded') && \OC::$server->getSession()->get('checkServer_succeeded')) {
			return $errors;
		}

		$webServerRestart = false;
		$setup = new \OC\Setup(
			$config,
			\OC::$server->getIniWrapper(),
			\OC::$server->getL10N('lib'),
			new \OC_Defaults(),
			\OC::$server->getLogger(),
			\OC::$server->getSecureRandom()
		);

		$urlGenerator = \OC::$server->getURLGenerator();

		$availableDatabases = $setup->getSupportedDatabases();
		if (empty($availableDatabases)) {
			$errors[] = [
				'error' => $l->t('No database drivers (sqlite, mysql, or postgresql) installed.'),
				'hint' => '' //TODO: sane hint
			];
			$webServerRestart = true;
		}

		// Check if config folder is writable.
		if (!\OC::$server->getConfig()->isSystemConfigReadOnly()) {
			if (!\is_writable(OC::$configDir) or !\is_readable(OC::$configDir)) {
				$errors[] = [
					'error' => $l->t('Cannot write into "config" directory'),
					'hint' => $l->t(
						'This can usually be fixed by '
						. '%sgiving the webserver write access to the config directory%s.',
						['<a href="' . $urlGenerator->linkToDocs('admin-dir_permissions') . '" target="_blank" rel="noreferrer">', '</a>']
					)
				];
			}
		}

		// Create root dir.
		if ($config->getSystemValue('installed', false)) {
			if (!\is_dir($CONFIG_DATADIRECTORY)) {
				$success = @\mkdir($CONFIG_DATADIRECTORY);
				if ($success) {
					$errors = \array_merge($errors, self::checkDataDirectoryPermissions($CONFIG_DATADIRECTORY));
				} else {
					$errors[] = [
						'error' => $l->t('Cannot create "data" directory'),
						'hint' => $l->t(
							'This can usually be fixed by '
							. '<a href="%s" target="_blank" rel="noreferrer">giving the webserver write access to the root directory</a>.',
							[$urlGenerator->linkToDocs('admin-dir_permissions')]
						)
					];
				}
			} elseif (!\is_writable($CONFIG_DATADIRECTORY) or !\is_readable($CONFIG_DATADIRECTORY)) {
				//common hint for all file permissions error messages
				$permissionsHint = $l->t(
					'Permissions can usually be fixed by '
					. '%sgiving the webserver write access to the root directory%s.',
					['<a href="' . $urlGenerator->linkToDocs('admin-dir_permissions') . '" target="_blank" rel="noreferrer">', '</a>']
				);
				$errors[] = [
					'error' => 'Your Data directory is not writable by ownCloud',
					'hint' => $permissionsHint
				];
			} else {
				$errors = \array_merge($errors, self::checkDataDirectoryPermissions($CONFIG_DATADIRECTORY));
			}
		}

		if (!OC_Util::isSetLocaleWorking()) {
			$errors[] = [
				'error' => $l->t(
					'Setting locale to %s failed',
					['en_US.UTF-8/fr_FR.UTF-8/es_ES.UTF-8/de_DE.UTF-8/ru_RU.UTF-8/'
						. 'pt_BR.UTF-8/it_IT.UTF-8/ja_JP.UTF-8/zh_CN.UTF-8']
				),
				'hint' => $l->t('Please install one of these locales on your system and restart your webserver.')
			];
		}

		// Contains the dependencies that should be checked against
		// classes = class_exists
		// functions = function_exists
		// defined = defined
		// ini = ini_get
		// If the dependency is not found the missing module name is shown to the EndUser
		// When adding new checks always verify that they pass on CI as well
		$dependencies = [
			'classes' => [
				'ZipArchive' => 'zip',
				'DOMDocument' => 'dom',
				'XMLWriter' => 'XMLWriter',
				'XMLReader' => 'XMLReader',
				'Collator' => 'intl',
			],
			'functions' => [
				'xml_parser_create' => 'libxml',
				'mb_strcut' => 'mb multibyte',
				'ctype_digit' => 'ctype',
				'json_encode' => 'JSON',
				'gd_info' => 'GD',
				'gzencode' => 'zlib',
				'iconv' => 'iconv',
				'simplexml_load_string' => 'SimpleXML',
				'hash' => 'HASH Message Digest Framework',
				'curl_init' => 'cURL',
			],
			'defined' => [
				'PDO::ATTR_DRIVER_NAME' => 'PDO'
			],
			'ini' => [
				'default_charset' => 'UTF-8',
			],
		];
		$missingDependencies = [];
		$invalidIniSettings = [];
		$moduleHint = $l->t('Please ask your server administrator to install the module.');

		/**
		 * FIXME: The dependency check does not work properly on HHVM on the moment
		 *        and prevents installation. Once HHVM is more compatible with our
		 *        approach to check for these values we should re-enable those
		 *        checks.
		 */
		$iniWrapper = \OC::$server->getIniWrapper();
		if (!self::runningOnHhvm()) {
			foreach ($dependencies['classes'] as $class => $module) {
				if (!\class_exists($class)) {
					$missingDependencies[] = $module;
				}
			}
			foreach ($dependencies['functions'] as $function => $module) {
				if (!\function_exists($function)) {
					$missingDependencies[] = $module;
				}
			}
			foreach ($dependencies['defined'] as $defined => $module) {
				if (!\defined($defined)) {
					$missingDependencies[] = $module;
				}
			}
			foreach ($dependencies['ini'] as $setting => $expected) {
				if (\is_bool($expected)) {
					if ($iniWrapper->getBool($setting) !== $expected) {
						$invalidIniSettings[] = [$setting, $expected];
					}
				}
				if (\is_int($expected)) {
					if ($iniWrapper->getNumeric($setting) !== $expected) {
						$invalidIniSettings[] = [$setting, $expected];
					}
				}
				if (\is_string($expected)) {
					if (\strtolower($iniWrapper->getString($setting)) !== \strtolower($expected)) {
						$invalidIniSettings[] = [$setting, $expected];
					}
				}
			}
		}

		foreach ($missingDependencies as $missingDependency) {
			$errors[] = [
				'error' => $l->t('PHP module %s not installed.', [$missingDependency]),
				'hint' => $moduleHint
			];
			$webServerRestart = true;
		}
		foreach ($invalidIniSettings as $setting) {
			if (\is_bool($setting[1])) {
				$setting[1] = ($setting[1]) ? 'on' : 'off';
			}
			$errors[] = [
				'error' => $l->t('PHP setting "%s" is not set to "%s".', [$setting[0], \var_export($setting[1], true)]),
				'hint' =>  $l->t('Adjusting this setting in php.ini will make ownCloud run again')
			];
			$webServerRestart = true;
		}

		/**
		 * The mbstring.func_overload check can only be performed if the mbstring
		 * module is installed as it will return null if the checking setting is
		 * not available and thus a check on the boolean value fails.
		 *
		 * TODO: Should probably be implemented in the above generic dependency
		 *       check somehow in the long-term.
		 */
		if ($iniWrapper->getBool('mbstring.func_overload') !== null &&
			$iniWrapper->getBool('mbstring.func_overload') === true) {
			$errors[] = [
				'error' => $l->t('mbstring.func_overload is set to "%s" instead of the expected value "0"', [$iniWrapper->getString('mbstring.func_overload')]),
				'hint' => $l->t('To fix this issue set <code>mbstring.func_overload</code> to <code>0</code> in your php.ini')
			];
		}

		if (\function_exists('xml_parser_create') &&
			\version_compare('2.7.0', LIBXML_DOTTED_VERSION) === 1) {
			$errors[] = [
				'error' => $l->t('libxml2 2.7.0 is at least required. Currently %s is installed.', [LIBXML_DOTTED_VERSION]),
				'hint' => $l->t('To fix this issue update your libxml2 version and restart your web server.')
			];
		}

		if (!self::isAnnotationsWorking()) {
			$errors[] = [
				'error' => $l->t('PHP is apparently set up to strip inline doc blocks. This will make several core apps inaccessible.'),
				'hint' => $l->t('This is probably caused by a cache/accelerator such as Zend OPcache or eAccelerator.')
			];
		}

		if (!\OC::$CLI && $webServerRestart) {
			$errors[] = [
				'error' => $l->t('PHP modules have been installed, but they are still listed as missing?'),
				'hint' => $l->t('Please ask your server administrator to restart the web server.')
			];
		}

		$errors = \array_merge($errors, self::checkDatabaseVersion());

		// Cache the result of this function
		\OC::$server->getSession()->set('checkServer_succeeded', \count($errors) == 0);

		return $errors;
	}

	/**
	 * Check the database version
	 *
	 * @return array errors array
	 */
	public static function checkDatabaseVersion() {
		$l = \OC::$server->getL10N('lib');
		$errors = [];
		$dbType = \OC::$server->getSystemConfig()->getValue('dbtype', 'sqlite');
		if ($dbType === 'pgsql') {
			// check PostgreSQL version
			try {
				$result = \OC_DB::executeAudited('SHOW SERVER_VERSION');
				$data = $result->fetchRow();
				if (isset($data['server_version'])) {
					$version = $data['server_version'];
					if (\version_compare($version, '9.0.0', '<')) {
						$errors[] = [
							'error' => $l->t('PostgreSQL >= 9 required'),
							'hint' => $l->t('Please upgrade your database version')
						];
					}
				}
			} catch (\Doctrine\DBAL\DBALException $e) {
				$logger = \OC::$server->getLogger();
				$logger->warning('Error occurred while checking PostgreSQL version, assuming >= 9');
				$logger->logException($e);
			}
		}
		return $errors;
	}

	/**
	 * Check for correct file permissions of data directory
	 *
	 * @param string $dataDirectory
	 * @return array arrays with error messages and hints
	 */
	public static function checkDataDirectoryPermissions($dataDirectory) {
		$l = \OC::$server->getL10N('lib');
		$errors = [];
		$permissionsModHint = $l->t('Please change the permissions to 0770 so that the directory'
			. ' cannot be listed by other users.');
		$perms = \substr(\decoct(@\fileperms($dataDirectory)), -3);
		if (\substr($perms, -1) != '0') {
			\chmod($dataDirectory, 0770);
			\clearstatcache();
			$perms = \substr(\decoct(@\fileperms($dataDirectory)), -3);
			if (\substr($perms, 2, 1) != '0') {
				$errors[] = [
					'error' => $l->t('Your Data directory is readable by other users'),
					'hint' => $permissionsModHint
				];
			}
		}
		return $errors;
	}

	/**
	 * Check that the data directory exists and is valid by
	 * checking the existence of the ".ocdata" file.
	 *
	 * @param string $dataDirectory data directory path
	 * @return array errors found
	 */
	public static function checkDataDirectoryValidity($dataDirectory) {
		$l = \OC::$server->getL10N('lib');
		$errors = [];
		if ($dataDirectory[0] !== '/') {
			$errors[] = [
				'error' => $l->t('Your Data directory must be an absolute path'),
				'hint' => $l->t('Check the value of "datadirectory" in your configuration')
			];
		}
		if (!\file_exists($dataDirectory . '/.ocdata')) {
			$errors[] = [
				'error' => $l->t('Your Data directory  is invalid'),
				'hint' => $l->t('Please check that the data directory contains a file' .
					' ".ocdata" in its root.')
			];
		}
		return $errors;
	}

	/**
	 * @return bool
	 * @throws LoginException
	 */
	private static function checkPreSignedUrl(): bool {
		$request = \Sabre\HTTP\Sapi::createFromServerArray($_SERVER);
		$verifier = new Verifier($request, \OC::$server->getConfig());
		if ($verifier->isSignedRequest()) {
			if (!$verifier->signedRequestIsValid()) {
				throw new LoginException('Invalid pre signed url');
			}

			$urlCredential = $verifier->getUrlCredential();
			$user = \OC::$server->getUserManager()->get($urlCredential);
			if ($user === null) {
				$message = \OC::$server->getL10N('dav')->t('User unknown');
				throw new LoginException($message);
			}
			if (!$user->isEnabled()) {
				$message = \OC::$server->getL10N('dav')->t('User disabled');
				throw new LoginException($message);
			}
			\OC::$server->getUserSession()->setUser($user);
			\OC_Util::setupFS($urlCredential);
			\OC::$server->getSession()->close();
			return true;
		}
		return false;
	}

	/**
	 * Check if the user is logged in, redirects to home if not. With
	 * redirect URL parameter to the request URI.
	 *
	 * @param bool $allowPreSigned
	 * @return void
	 * @throws LoginException
	 */
	public static function checkLoggedIn($allowPreSigned = false): void {
		if ($allowPreSigned && self::checkPreSignedUrl()) {
			return;
		}
		// Check if we are a user
		$userSession = \OC::$server->getUserSession();
		if ($userSession && !$userSession->isLoggedIn()) {
			\header(
				'Location: ' . \OC::$server->getURLGenerator()->linkToRoute(
					'core.login.showLoginForm',
					[
							'redirect_url' => \urlencode(\OC::$server->getRequest()->getRequestUri()),
						]
				)
			);
			exit();
		}
		// Redirect to index page if 2FA challenge was not solved yet
		if (\OC::$server->getTwoFactorAuthManager()->needsSecondFactor()) {
			\header('Location: ' . \OCP\Util::linkToAbsolute('', 'index.php'));
			exit();
		}
		// Redirect to index page if any IAuthModule check fails
		try {
			\OC::$server->getAccountModuleManager()->check($userSession->getUser());
		} catch (AccountCheckException $ex) {
			\header('Location: ' . \OCP\Util::linkToAbsolute('', 'index.php'));
			exit();
		}
	}

	/**
	 * Check if the user is a admin, redirects to home if not
	 *
	 * @return void
	 */
	public static function checkAdminUser() {
		OC_Util::checkLoggedIn();
		if (!OC_User::isAdminUser(OC_User::getUser())) {
			\header('Location: ' . \OCP\Util::linkToAbsolute('', 'index.php'));
			exit();
		}
	}

	/**
	 * Check if it is allowed to remember login.
	 *
	 * @note Every app can set 'rememberlogin' to 'false' to disable the remember login feature
	 *
	 * @return bool
	 */
	public static function rememberLoginAllowed() {
		$apps = OC_App::getEnabledApps();

		foreach ($apps as $app) {
			$appInfo = OC_App::getAppInfo($app);
			if (isset($appInfo['rememberlogin']) && $appInfo['rememberlogin'] === 'false') {
				return false;
			}
		}
		return true;
	}

	/**
	 * Check if the user is a subadmin, redirects to home if not
	 *
	 * @return null|boolean $groups where the current user is subadmin
	 */
	public static function checkSubAdminUser() {
		OC_Util::checkLoggedIn();
		$userObject = \OC::$server->getUserSession()->getUser();
		$isSubAdmin = false;
		if ($userObject !== null) {
			$isSubAdmin = \OC::$server->getGroupManager()->getSubAdmin()->isSubAdmin($userObject);
		}

		if (!$isSubAdmin) {
			\header('Location: ' . \OCP\Util::linkToAbsolute('', 'index.php'));
			exit();
		}
		return true;
	}

	/**
	 * Returns the URL of the default page
	 * based on the system configuration and
	 * the apps visible for the current user
	 *
	 * @return string URL
	 */
	public static function getDefaultPageUrl() {
		$urlGenerator = \OC::$server->getURLGenerator();
		// Deny the redirect if the URL contains a @
		// This prevents unvalidated redirects like ?redirect_url=:user@domain.com
		if (isset($_REQUEST['redirect_url']) && \strpos($_REQUEST['redirect_url'], '@') === false) {
			$location = $urlGenerator->getAbsoluteURL(\urldecode($_REQUEST['redirect_url']));
		} else {
			$defaultPage = \OC::$server->getAppConfig()->getValue('core', 'defaultpage');
			if ($defaultPage) {
				$location = $urlGenerator->getAbsoluteURL($defaultPage);
			} else {
				$appId = 'files';
				$uid = \OC_User::getUser();
				$config = \OC::$server->getConfig();
				$defaultApps = \explode(',', $config->getSystemValue('defaultapp', 'files'));

				if ($uid) {
					$userDefaultApp = $config->getUserValue($uid, 'core', 'defaultapp', null);
					if ($userDefaultApp) {
						\array_unshift($defaultApps, $userDefaultApp);
					}
				}

				// find the first app that is enabled for the current user
				foreach ($defaultApps as $defaultApp) {
					$defaultApp = OC_App::cleanAppId(\strip_tags($defaultApp));
					if (static::getAppManager()->isEnabledForUser($defaultApp)) {
						$appId = $defaultApp;
						break;
					}
				}

				if (\getenv('front_controller_active') === 'true') {
					$location = $urlGenerator->getAbsoluteURL('/apps/' . $appId . '/');
				} else {
					$location = $urlGenerator->getAbsoluteURL('/index.php/apps/' . $appId . '/');
				}
			}
		}
		return $location;
	}

	/**
	 * Redirect to the user default page
	 *
	 * @return void
	 */
	public static function redirectToDefaultPage() {
		$location = self::getDefaultPageUrl();
		\header('Location: ' . $location);
		exit();
	}

	/**
	 * get an id unique for this instance
	 *
	 * @return string
	 */
	public static function getInstanceId() {
		$id = \OC::$server->getSystemConfig()->getValue('instanceid', null);
		if ($id === null) {
			// We need to guarantee at least one letter in instanceid so it can be used as the session_name
			$id = 'oc' . \OC::$server->getSecureRandom()->generate(10, \OCP\Security\ISecureRandom::CHAR_LOWER.\OCP\Security\ISecureRandom::CHAR_DIGITS);
			\OC::$server->getSystemConfig()->setValue('instanceid', $id);
		}
		return $id;
	}

	/**
	 * Public function to sanitize HTML
	 *
	 * This function is used to sanitize HTML and should be applied on any
	 * string or array of strings before displaying it on a web page.
	 *
	 * @param string|array $value
	 * @return string|array an array of sanitized strings or a single sanitized string, depends on the input parameter.
	 */
	public static function sanitizeHTML($value) {
		if (\is_array($value)) {
			$value = \array_map(function ($value) {
				return self::sanitizeHTML($value);
			}, $value);
		} else {
			// Specify encoding for PHP<5.4
			$value = \htmlspecialchars((string)$value, ENT_QUOTES, 'UTF-8');
		}
		return $value;
	}

	/**
	 * Public function to encode url parameters
	 *
	 * This function is used to encode path to file before output.
	 * Encoding is done according to RFC 3986 with one exception:
	 * Character '/' is preserved as is.
	 *
	 * @param string $component part of URI to encode
	 * @return string
	 */
	public static function encodePath($component) {
		$encoded = \rawurlencode($component);
		$encoded = \str_replace('%2F', '/', $encoded);
		return $encoded;
	}

	public function createHtaccessTestFile(\OCP\IConfig $config) {
		// php dev server does not support htaccess
		if (\php_sapi_name() === 'cli-server') {
			return false;
		}
		if (\OC::$CLI) {
			return false;
		}

		// testdata
		$fileName = '/htaccesstest.txt';
		// test content containing the string "HTACCESSFAIL"
		$testContent = 'HTACCESSFAIL: This is used for testing whether htaccess is properly enabled to disallow access from the outside. This file can be safely removed.';

		// creating a test file
		$testFile = $config->getSystemValue('datadirectory', OC::$SERVERROOT . '/data') . '/' . $fileName;

		if (\file_exists($testFile)) {// already running this test, possible recursive call
			return false;
		}

		$fp = @\fopen($testFile, 'w');
		if (!$fp) {
			throw new OC\HintException(
				'Can\'t create test file to check for working .htaccess file.',
				'Make sure it is possible for the webserver to write to ' . $testFile
			);
		}
		\fwrite($fp, $testContent);
		\fclose($fp);
	}

	/**
	 * Check if the setlocal call does not work. This can happen if the right
	 * local packages are not available on the server.
	 *
	 * @return bool
	 */
	public static function isSetLocaleWorking() {
		if (\basename('§') === '§') {
			return true;
		}

		\setlocale(LC_ALL, 'C.UTF-8', 'C');
		\setlocale(LC_CTYPE, 'en_US.UTF-8', 'fr_FR.UTF-8', 'es_ES.UTF-8', 'de_DE.UTF-8', 'ru_RU.UTF-8', 'pt_BR.UTF-8', 'it_IT.UTF-8', 'ja_JP.UTF-8', 'zh_CN.UTF-8', '0');

		return \basename('§') === '§';
	}

	/**
	 * Check if it's possible to get the inline annotations
	 *
	 * @return bool
	 */
	public static function isAnnotationsWorking() {
		$reflection = new \ReflectionMethod(__METHOD__);
		$docs = $reflection->getDocComment();

		return (\is_string($docs) && \strlen($docs) > 50);
	}

	/**
	 * Check if the PHP module fileinfo is loaded.
	 *
	 * @return bool
	 */
	public static function fileInfoLoaded() {
		return \function_exists('finfo_open');
	}

	/**
	 * clear all levels of output buffering
	 *
	 * @return void
	 */
	public static function obEnd() {
		while (\ob_get_level()) {
			\ob_end_clean();
		}
	}

	/**
	 * Checks whether the server is running on the given OS type
	 *
	 * @param string $osType linux|mac|bsd etc
	 * @return bool true if running on that OS type, false otherwise
	 */
	public static function runningOn($osType) {
		$osType = \strtolower($osType) === 'mac' ? 'darwin' : \strtolower($osType);

		if ($osType === 'bsd') {
			return (\strpos(\strtolower(PHP_OS), $osType) !== false);
		} else {
			return (\strtolower(\substr(PHP_OS, 0, \strlen($osType))) === $osType);
		}
	}

	/**
	 * Checks whether server is running on HHVM
	 *
	 * @return bool True if running on HHVM, false otherwise
	 */
	public static function runningOnHhvm() {
		return \defined('HHVM_VERSION');
	}

	/**
	 * Handles the case that there may not be a theme, then check if a "default"
	 * theme exists and take that one
	 *
	 * @return \OCP\Theme\ITheme the theme
	 */
	public static function getTheme() {
		/** @var \OCP\Theme\IThemeService $themeService */
		$themeService = \OC::$server->query('ThemeService');
		return $themeService->getTheme();
	}

	/**
	 * Clear a single file from the opcode cache
	 * This is useful for writing to the config file
	 * in case the opcode cache does not re-validate files
	 * Returns true if successful, false if unsuccessful:
	 * caller should fall back on clearing the entire cache
	 * with clearOpcodeCache() if unsuccessful
	 *
	 * @param string $path the path of the file to clear from the cache
	 * @return bool true if underlying function returns true, otherwise false
	 */
	public static function deleteFromOpcodeCache($path) {
		$ret = false;
		if ($path) {
			// APC >= 3.1.1
			if (\function_exists('apc_delete_file')) {
				$ret = @apc_delete_file($path);
			}
			// Zend OpCache >= 7.0.0, PHP >= 5.5.0
			if (\function_exists('opcache_invalidate')) {
				$ret = \opcache_invalidate($path);
			}
		}
		return $ret;
	}

	/**
	 * Clear the opcode cache if one exists
	 * This is necessary for writing to the config file
	 * in case the opcode cache does not re-validate files
	 *
	 * @return void
	 */
	public static function clearOpcodeCache() {
		// APC
		if (\function_exists('apc_clear_cache')) {
			\apc_clear_cache();
		}
		// Zend Opcache
		if (\function_exists('accelerator_reset')) {
			accelerator_reset();
		}
		// Opcache (PHP >= 5.5)
		if (\function_exists('opcache_reset')) {
			\opcache_reset();
		}
	}

	/**
	 * Normalize a unicode string
	 *
	 * @param string $value a not normalized string
	 * @return bool|string
	 */
	public static function normalizeUnicode($value) {
		if (Normalizer::isNormalized($value)) {
			return $value;
		}

		$normalizedValue = Normalizer::normalize($value);
		if ($normalizedValue === null || $normalizedValue === false) {
			\OC::$server->getLogger()->warning('normalizing failed for "' . $value . '"', ['app' => 'core']);
			return $value;
		}

		return $normalizedValue;
	}

	/**
	 * @param boolean|string $file
	 * @return string
	 */
	public static function basename($file) {
		$file = \rtrim($file, '/');
		$t = \explode('/', $file);
		return \array_pop($t);
	}

	/**
	 * Remove the ".part" extension from the path. The "ocTransferId" part added for the uploads
	 * can also be removed.
	 * @params string $path the path to be cleaned up
	 * @params bool $stripTransferId whether the method should also remove the "ocTransferId" if it exists
	 * @return string the cleaned path
	 */
	public static function stripPartialFileExtension(string $path, bool $stripTransferId = true): string {
		$extension = \pathinfo($path, PATHINFO_EXTENSION);

		if ($extension === 'part') {
			$newLength = \strlen($path) - 5; // 5 = strlen(".part")
			$fPath = \substr($path, 0, $newLength);

			// if path also contains a transaction id, we remove it too
			$extension = \pathinfo($fPath, PATHINFO_EXTENSION);
			if ($stripTransferId && \substr($extension, 0, 12) === 'ocTransferId') { // 12 = strlen("ocTransferId")
				$newLength = \strlen($fPath) - \strlen($extension) -1;
				$fPath = \substr($fPath, 0, $newLength);
			}
			return $fPath;
		} else {
			return $path;
		}
	}

	/**
	 * A human readable string is generated based on version, channel and build number
	 *
	 * @return string
	 */
	public static function getHumanVersion() {
		$version = OC_Util::getVersionString() . ' (' . OC_Util::getChannel() . ')';
		$build = OC_Util::getBuild();
		if (!empty($build) and OC_Util::getChannel() === 'daily') {
			$version .= ' Build:' . $build;
		}
		return $version;
	}

	/**
	 * Returns whether the given file name is valid
	 *
	 * @param string $file file name to check
	 * @return bool true if the file name is valid, false otherwise
	 * @deprecated use \OC\Files\View::verifyPath()
	 */
	public static function isValidFileName($file) {
		$trimmed = \trim($file);
		if ($trimmed === '') {
			return false;
		}
		if (\OC\Files\Filesystem::isIgnoredDir($trimmed)) {
			return false;
		}

		// detect part files
		if (\preg_match('/' . \OCP\Files\FileInfo::BLACKLIST_FILES_REGEX . '/', $trimmed) !== 0) {
			return false;
		}

		foreach (\str_split($trimmed) as $char) {
			if (\strpos(\OCP\Constants::FILENAME_INVALID_CHARS, $char) !== false) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Check whether the instance needs to perform an upgrade,
	 * either when the core version is higher or any app requires
	 * an upgrade.
	 *
	 * @param \OCP\IConfig $config
	 * @return bool whether the core or any app needs an upgrade
	 * @throws \OC\HintException When the upgrade from the given version is not allowed
	 */
	public static function needUpgrade(\OCP\IConfig $config) {
		if ($config->getSystemValue('installed', false)) {
			$installedVersion = $config->getSystemValue('version', '0.0.0');
			$currentVersion = \implode('.', \OCP\Util::getVersion());
			$versionDiff = \version_compare($currentVersion, $installedVersion);
			if ($versionDiff > 0) {
				return true;
			} elseif ($config->getSystemValue('debug', false) && $versionDiff < 0) {
				// downgrade with debug
				$installedMajor = \explode('.', $installedVersion);
				$installedMajor = $installedMajor[0] . '.' . $installedMajor[1];
				$currentMajor = \explode('.', $currentVersion);
				$currentMajor = $currentMajor[0] . '.' . $currentMajor[1];
				if ($installedMajor === $currentMajor) {
					// Same major, allow downgrade for developers
					return true;
				} else {
					// downgrade attempt, throw exception
					throw new \OC\HintException('Downgrading is not supported and is likely to cause unpredictable issues (from ' . $installedVersion . ' to ' . $currentVersion . ')');
				}
			} elseif ($versionDiff < 0) {
				// downgrade attempt, throw exception
				throw new \OC\HintException('Downgrading is not supported and is likely to cause unpredictable issues (from ' . $installedVersion . ' to ' . $currentVersion . ')');
			}

			// also check for upgrades for apps (independently from the user)
			$apps = \OC_App::getEnabledApps(false, true);
			$shouldUpgrade = false;
			foreach ($apps as $app) {
				if (\OC_App::shouldUpgrade($app)) {
					$shouldUpgrade = true;
					break;
				}
			}
			return $shouldUpgrade;
		} else {
			return false;
		}
	}
}
