nextcloud / server

lib/private/L10N/Factory.php

Indentation +636 added lines, -636 removed lines

@@ -49,640 +49,640 @@
  */
 class Factory implements IFactory {
 
-	/** @var string */
-	protected $requestLanguage = '';
-
-	/**
-	 * cached instances
-	 * @var array Structure: Lang => App => \OCP\IL10N
-	 */
-	protected $instances = [];
-
-	/**
-	 * @var array Structure: App => string[]
-	 */
-	protected $availableLanguages = [];
-
-	/**
-	 * @var array
-	 */
-	protected $localeCache = [];
-
-	/**
-	 * @var array
-	 */
-	protected $availableLocales = [];
-
-	/**
-	 * @var array Structure: string => callable
-	 */
-	protected $pluralFunctions = [];
-
-	public const COMMON_LANGUAGE_CODES = [
-		'en', 'es', 'fr', 'de', 'de_DE', 'ja', 'ar', 'ru', 'nl', 'it',
-		'pt_BR', 'pt_PT', 'da', 'fi_FI', 'nb_NO', 'sv', 'tr', 'zh_CN', 'ko'
-	];
-
-	/** @var IConfig */
-	protected $config;
-
-	/** @var IRequest */
-	protected $request;
-
-	/** @var IUserSession */
-	protected $userSession;
-
-	/** @var string */
-	protected $serverRoot;
-
-	/**
-	 * @param IConfig $config
-	 * @param IRequest $request
-	 * @param IUserSession $userSession
-	 * @param string $serverRoot
-	 */
-	public function __construct(IConfig $config,
-								IRequest $request,
-								IUserSession $userSession,
-								$serverRoot) {
-		$this->config = $config;
-		$this->request = $request;
-		$this->userSession = $userSession;
-		$this->serverRoot = $serverRoot;
-	}
-
-	/**
-	 * Get a language instance
-	 *
-	 * @param string $app
-	 * @param string|null $lang
-	 * @param string|null $locale
-	 * @return \OCP\IL10N
-	 */
-	public function get($app, $lang = null, $locale = null) {
-		return new LazyL10N(function () use ($app, $lang, $locale) {
-			$app = \OC_App::cleanAppId($app);
-			if ($lang !== null) {
-				$lang = str_replace(['\0', '/', '\\', '..'], '', (string)$lang);
-			}
-
-			$forceLang = $this->config->getSystemValue('force_language', false);
-			if (is_string($forceLang)) {
-				$lang = $forceLang;
-			}
-
-			$forceLocale = $this->config->getSystemValue('force_locale', false);
-			if (is_string($forceLocale)) {
-				$locale = $forceLocale;
-			}
-
-			if ($lang === null || !$this->languageExists($app, $lang)) {
-				$lang = $this->findLanguage($app);
-			}
-
-			if ($locale === null || !$this->localeExists($locale)) {
-				$locale = $this->findLocale($lang);
-			}
-
-			if (!isset($this->instances[$lang][$app])) {
-				$this->instances[$lang][$app] = new L10N(
-					$this, $app, $lang, $locale,
-					$this->getL10nFilesForApp($app, $lang)
-				);
-			}
-
-			return $this->instances[$lang][$app];
-		});
-	}
-
-	/**
-	 * Find the best language
-	 *
-	 * @param string|null $app App id or null for core
-	 * @return string language If nothing works it returns 'en'
-	 */
-	public function findLanguage($app = null) {
-		$forceLang = $this->config->getSystemValue('force_language', false);
-		if (is_string($forceLang)) {
-			$this->requestLanguage = $forceLang;
-		}
-
-		if ($this->requestLanguage !== '' && $this->languageExists($app, $this->requestLanguage)) {
-			return $this->requestLanguage;
-		}
-
-		/**
-		 * At this point Nextcloud might not yet be installed and thus the lookup
-		 * in the preferences table might fail. For this reason we need to check
-		 * whether the instance has already been installed
-		 *
-		 * @link https://github.com/owncloud/core/issues/21955
-		 */
-		if ($this->config->getSystemValue('installed', false)) {
-			$userId = !is_null($this->userSession->getUser()) ? $this->userSession->getUser()->getUID() :  null;
-			if (!is_null($userId)) {
-				$userLang = $this->config->getUserValue($userId, 'core', 'lang', null);
-			} else {
-				$userLang = null;
-			}
-		} else {
-			$userId = null;
-			$userLang = null;
-		}
-
-		if ($userLang) {
-			$this->requestLanguage = $userLang;
-			if ($this->languageExists($app, $userLang)) {
-				return $userLang;
-			}
-		}
-
-		try {
-			// Try to get the language from the Request
-			$lang = $this->getLanguageFromRequest($app);
-			if ($userId !== null && $app === null && !$userLang) {
-				$this->config->setUserValue($userId, 'core', 'lang', $lang);
-			}
-			return $lang;
-		} catch (LanguageNotFoundException $e) {
-			// Finding language from request failed fall back to default language
-			$defaultLanguage = $this->config->getSystemValue('default_language', false);
-			if ($defaultLanguage !== false && $this->languageExists($app, $defaultLanguage)) {
-				return $defaultLanguage;
-			}
-		}
-
-		// We could not find any language so fall back to english
-		return 'en';
-	}
-
-	/**
-	 * find the best locale
-	 *
-	 * @param string $lang
-	 * @return null|string
-	 */
-	public function findLocale($lang = null) {
-		$forceLocale = $this->config->getSystemValue('force_locale', false);
-		if (is_string($forceLocale) && $this->localeExists($forceLocale)) {
-			return $forceLocale;
-		}
-
-		if ($this->config->getSystemValue('installed', false)) {
-			$userId = null !== $this->userSession->getUser() ? $this->userSession->getUser()->getUID() :  null;
-			$userLocale = null;
-			if (null !== $userId) {
-				$userLocale = $this->config->getUserValue($userId, 'core', 'locale', null);
-			}
-		} else {
-			$userId = null;
-			$userLocale = null;
-		}
-
-		if ($userLocale && $this->localeExists($userLocale)) {
-			return $userLocale;
-		}
-
-		// Default : use system default locale
-		$defaultLocale = $this->config->getSystemValue('default_locale', false);
-		if ($defaultLocale !== false && $this->localeExists($defaultLocale)) {
-			return $defaultLocale;
-		}
-
-		// If no user locale set, use lang as locale
-		if (null !== $lang && $this->localeExists($lang)) {
-			return $lang;
-		}
-
-		// At last, return USA
-		return 'en_US';
-	}
-
-	/**
-	 * find the matching lang from the locale
-	 *
-	 * @param string $app
-	 * @param string $locale
-	 * @return null|string
-	 */
-	public function findLanguageFromLocale(string $app = 'core', string $locale = null) {
-		if ($this->languageExists($app, $locale)) {
-			return $locale;
-		}
-
-		// Try to split e.g: fr_FR => fr
-		$locale = explode('_', $locale)[0];
-		if ($this->languageExists($app, $locale)) {
-			return $locale;
-		}
-	}
-
-	/**
-	 * Find all available languages for an app
-	 *
-	 * @param string|null $app App id or null for core
-	 * @return array an array of available languages
-	 */
-	public function findAvailableLanguages($app = null) {
-		$key = $app;
-		if ($key === null) {
-			$key = 'null';
-		}
-
-		// also works with null as key
-		if (!empty($this->availableLanguages[$key])) {
-			return $this->availableLanguages[$key];
-		}
-
-		$available = ['en']; //english is always available
-		$dir = $this->findL10nDir($app);
-		if (is_dir($dir)) {
-			$files = scandir($dir);
-			if ($files !== false) {
-				foreach ($files as $file) {
-					if (substr($file, -5) === '.json' && substr($file, 0, 4) !== 'l10n') {
-						$available[] = substr($file, 0, -5);
-					}
-				}
-			}
-		}
-
-		// merge with translations from theme
-		$theme = $this->config->getSystemValue('theme');
-		if (!empty($theme)) {
-			$themeDir = $this->serverRoot . '/themes/' . $theme . substr($dir, strlen($this->serverRoot));
-
-			if (is_dir($themeDir)) {
-				$files = scandir($themeDir);
-				if ($files !== false) {
-					foreach ($files as $file) {
-						if (substr($file, -5) === '.json' && substr($file, 0, 4) !== 'l10n') {
-							$available[] = substr($file, 0, -5);
-						}
-					}
-				}
-			}
-		}
-
-		$this->availableLanguages[$key] = $available;
-		return $available;
-	}
-
-	/**
-	 * @return array|mixed
-	 */
-	public function findAvailableLocales() {
-		if (!empty($this->availableLocales)) {
-			return $this->availableLocales;
-		}
-
-		$localeData = file_get_contents(\OC::$SERVERROOT . '/resources/locales.json');
-		$this->availableLocales = \json_decode($localeData, true);
-
-		return $this->availableLocales;
-	}
-
-	/**
-	 * @param string|null $app App id or null for core
-	 * @param string $lang
-	 * @return bool
-	 */
-	public function languageExists($app, $lang) {
-		if ($lang === 'en') {//english is always available
-			return true;
-		}
-
-		$languages = $this->findAvailableLanguages($app);
-		return array_search($lang, $languages) !== false;
-	}
-
-	public function getLanguageIterator(IUser $user = null): ILanguageIterator {
-		$user = $user ?? $this->userSession->getUser();
-		if ($user === null) {
-			throw new \RuntimeException('Failed to get an IUser instance');
-		}
-		return new LanguageIterator($user, $this->config);
-	}
-
-	/**
-	 * Return the language to use when sending something to a user
-	 *
-	 * @param IUser|null $user
-	 * @return string
-	 * @since 20.0.0
-	 */
-	public function getUserLanguage(IUser $user = null): string {
-		$language = $this->config->getSystemValue('force_language', false);
-		if ($language !== false) {
-			return $language;
-		}
-
-		if ($user instanceof IUser) {
-			$language = $this->config->getUserValue($user->getUID(), 'core', 'lang', null);
-			if ($language !== null) {
-				return $language;
-			}
-		}
-
-		return $this->config->getSystemValue('default_language', 'en');
-	}
-
-	/**
-	 * @param string $locale
-	 * @return bool
-	 */
-	public function localeExists($locale) {
-		if ($locale === 'en') { //english is always available
-			return true;
-		}
-
-		if ($this->localeCache === []) {
-			$locales = $this->findAvailableLocales();
-			foreach ($locales as $l) {
-				$this->localeCache[$l['code']] = true;
-			}
-		}
-
-		return isset($this->localeCache[$locale]);
-	}
-
-	/**
-	 * @param string|null $app
-	 * @return string
-	 * @throws LanguageNotFoundException
-	 */
-	private function getLanguageFromRequest($app) {
-		$header = $this->request->getHeader('ACCEPT_LANGUAGE');
-		if ($header !== '') {
-			$available = $this->findAvailableLanguages($app);
-
-			// E.g. make sure that 'de' is before 'de_DE'.
-			sort($available);
-
-			$preferences = preg_split('/,\s*/', strtolower($header));
-			foreach ($preferences as $preference) {
-				list($preferred_language) = explode(';', $preference);
-				$preferred_language = str_replace('-', '_', $preferred_language);
-
-				foreach ($available as $available_language) {
-					if ($preferred_language === strtolower($available_language)) {
-						return $this->respectDefaultLanguage($app, $available_language);
-					}
-				}
-
-				// Fallback from de_De to de
-				foreach ($available as $available_language) {
-					if (substr($preferred_language, 0, 2) === $available_language) {
-						return $available_language;
-					}
-				}
-			}
-		}
-
-		throw new LanguageNotFoundException();
-	}
-
-	/**
-	 * if default language is set to de_DE (formal German) this should be
-	 * preferred to 'de' (non-formal German) if possible
-	 *
-	 * @param string|null $app
-	 * @param string $lang
-	 * @return string
-	 */
-	protected function respectDefaultLanguage($app, $lang) {
-		$result = $lang;
-		$defaultLanguage = $this->config->getSystemValue('default_language', false);
-
-		// use formal version of german ("Sie" instead of "Du") if the default
-		// language is set to 'de_DE' if possible
-		if (is_string($defaultLanguage) &&
-			strtolower($lang) === 'de' &&
-			strtolower($defaultLanguage) === 'de_de' &&
-			$this->languageExists($app, 'de_DE')
-		) {
-			$result = 'de_DE';
-		}
-
-		return $result;
-	}
-
-	/**
-	 * Checks if $sub is a subdirectory of $parent
-	 *
-	 * @param string $sub
-	 * @param string $parent
-	 * @return bool
-	 */
-	private function isSubDirectory($sub, $parent) {
-		// Check whether $sub contains no ".."
-		if (strpos($sub, '..') !== false) {
-			return false;
-		}
-
-		// Check whether $sub is a subdirectory of $parent
-		if (strpos($sub, $parent) === 0) {
-			return true;
-		}
-
-		return false;
-	}
-
-	/**
-	 * Get a list of language files that should be loaded
-	 *
-	 * @param string $app
-	 * @param string $lang
-	 * @return string[]
-	 */
-	// FIXME This method is only public, until OC_L10N does not need it anymore,
-	// FIXME This is also the reason, why it is not in the public interface
-	public function getL10nFilesForApp($app, $lang) {
-		$languageFiles = [];
-
-		$i18nDir = $this->findL10nDir($app);
-		$transFile = strip_tags($i18nDir) . strip_tags($lang) . '.json';
-
-		if (($this->isSubDirectory($transFile, $this->serverRoot . '/core/l10n/')
-				|| $this->isSubDirectory($transFile, $this->serverRoot . '/lib/l10n/')
-				|| $this->isSubDirectory($transFile, \OC_App::getAppPath($app) . '/l10n/')
-			)
-			&& file_exists($transFile)) {
-			// load the translations file
-			$languageFiles[] = $transFile;
-		}
-
-		// merge with translations from theme
-		$theme = $this->config->getSystemValue('theme');
-		if (!empty($theme)) {
-			$transFile = $this->serverRoot . '/themes/' . $theme . substr($transFile, strlen($this->serverRoot));
-			if (file_exists($transFile)) {
-				$languageFiles[] = $transFile;
-			}
-		}
-
-		return $languageFiles;
-	}
-
-	/**
-	 * find the l10n directory
-	 *
-	 * @param string $app App id or empty string for core
-	 * @return string directory
-	 */
-	protected function findL10nDir($app = null) {
-		if (in_array($app, ['core', 'lib'])) {
-			if (file_exists($this->serverRoot . '/' . $app . '/l10n/')) {
-				return $this->serverRoot . '/' . $app . '/l10n/';
-			}
-		} elseif ($app && \OC_App::getAppPath($app) !== false) {
-			// Check if the app is in the app folder
-			return \OC_App::getAppPath($app) . '/l10n/';
-		}
-		return $this->serverRoot . '/core/l10n/';
-	}
-
-
-	/**
-	 * Creates a function from the plural string
-	 *
-	 * Parts of the code is copied from Habari:
-	 * https://github.com/habari/system/blob/master/classes/locale.php
-	 * @param string $string
-	 * @return string
-	 */
-	public function createPluralFunction($string) {
-		if (isset($this->pluralFunctions[$string])) {
-			return $this->pluralFunctions[$string];
-		}
-
-		if (preg_match('/^\s*nplurals\s*=\s*(\d+)\s*;\s*plural=(.*)$/u', $string, $matches)) {
-			// sanitize
-			$nplurals = preg_replace('/[^0-9]/', '', $matches[1]);
-			$plural = preg_replace('#[^n0-9:\(\)\?\|\&=!<>+*/\%-]#', '', $matches[2]);
-
-			$body = str_replace(
-				[ 'plural', 'n', '$n$plurals', ],
-				[ '$plural', '$n', '$nplurals', ],
-				'nplurals='. $nplurals . '; plural=' . $plural
-			);
-
-			// add parents
-			// important since PHP's ternary evaluates from left to right
-			$body .= ';';
-			$res = '';
-			$p = 0;
-			$length = strlen($body);
-			for ($i = 0; $i < $length; $i++) {
-				$ch = $body[$i];
-				switch ($ch) {
-					case '?':
-						$res .= ' ? (';
-						$p++;
-						break;
-					case ':':
-						$res .= ') : (';
-						break;
-					case ';':
-						$res .= str_repeat(')', $p) . ';';
-						$p = 0;
-						break;
-					default:
-						$res .= $ch;
-				}
-			}
-
-			$body = $res . 'return ($plural>=$nplurals?$nplurals-1:$plural);';
-			$function = create_function('$n', $body);
-			$this->pluralFunctions[$string] = $function;
-			return $function;
-		} else {
-			// default: one plural form for all cases but n==1 (english)
-			$function = create_function(
-				'$n',
-				'$nplurals=2;$plural=($n==1?0:1);return ($plural>=$nplurals?$nplurals-1:$plural);'
-			);
-			$this->pluralFunctions[$string] = $function;
-			return $function;
-		}
-	}
-
-	/**
-	 * returns the common language and other languages in an
-	 * associative array
-	 *
-	 * @return array
-	 */
-	public function getLanguages() {
-		$forceLanguage = $this->config->getSystemValue('force_language', false);
-		if ($forceLanguage !== false) {
-			$l = $this->get('lib', $forceLanguage);
-			$potentialName = (string) $l->t('__language_name__');
-
-			return [
-				'commonlanguages' => [[
-					'code' => $forceLanguage,
-					'name' => $potentialName,
-				]],
-				'languages' => [],
-			];
-		}
-
-		$languageCodes = $this->findAvailableLanguages();
-
-		$commonLanguages = [];
-		$languages = [];
-
-		foreach ($languageCodes as $lang) {
-			$l = $this->get('lib', $lang);
-			// TRANSLATORS this is the language name for the language switcher in the personal settings and should be the localized version
-			$potentialName = (string) $l->t('__language_name__');
-			if ($l->getLanguageCode() === $lang && $potentialName[0] !== '_') {//first check if the language name is in the translation file
-				$ln = [
-					'code' => $lang,
-					'name' => $potentialName
-				];
-			} elseif ($lang === 'en') {
-				$ln = [
-					'code' => $lang,
-					'name' => 'English (US)'
-				];
-			} else {//fallback to language code
-				$ln = [
-					'code' => $lang,
-					'name' => $lang
-				];
-			}
-
-			// put appropriate languages into appropriate arrays, to print them sorted
-			// common languages -> divider -> other languages
-			if (in_array($lang, self::COMMON_LANGUAGE_CODES)) {
-				$commonLanguages[array_search($lang, self::COMMON_LANGUAGE_CODES)] = $ln;
-			} else {
-				$languages[] = $ln;
-			}
-		}
-
-		ksort($commonLanguages);
-
-		// sort now by displayed language not the iso-code
-		usort($languages, function ($a, $b) {
-			if ($a['code'] === $a['name'] && $b['code'] !== $b['name']) {
-				// If a doesn't have a name, but b does, list b before a
-				return 1;
-			}
-			if ($a['code'] !== $a['name'] && $b['code'] === $b['name']) {
-				// If a does have a name, but b doesn't, list a before b
-				return -1;
-			}
-			// Otherwise compare the names
-			return strcmp($a['name'], $b['name']);
-		});
-
-		return [
-			// reset indexes
-			'commonlanguages' => array_values($commonLanguages),
-			'languages' => $languages
-		];
-	}
+    /** @var string */
+    protected $requestLanguage = '';
+
+    /**
+     * cached instances
+     * @var array Structure: Lang => App => \OCP\IL10N
+     */
+    protected $instances = [];
+
+    /**
+     * @var array Structure: App => string[]
+     */
+    protected $availableLanguages = [];
+
+    /**
+     * @var array
+     */
+    protected $localeCache = [];
+
+    /**
+     * @var array
+     */
+    protected $availableLocales = [];
+
+    /**
+     * @var array Structure: string => callable
+     */
+    protected $pluralFunctions = [];
+
+    public const COMMON_LANGUAGE_CODES = [
+        'en', 'es', 'fr', 'de', 'de_DE', 'ja', 'ar', 'ru', 'nl', 'it',
+        'pt_BR', 'pt_PT', 'da', 'fi_FI', 'nb_NO', 'sv', 'tr', 'zh_CN', 'ko'
+    ];
+
+    /** @var IConfig */
+    protected $config;
+
+    /** @var IRequest */
+    protected $request;
+
+    /** @var IUserSession */
+    protected $userSession;
+
+    /** @var string */
+    protected $serverRoot;
+
+    /**
+     * @param IConfig $config
+     * @param IRequest $request
+     * @param IUserSession $userSession
+     * @param string $serverRoot
+     */
+    public function __construct(IConfig $config,
+                                IRequest $request,
+                                IUserSession $userSession,
+                                $serverRoot) {
+        $this->config = $config;
+        $this->request = $request;
+        $this->userSession = $userSession;
+        $this->serverRoot = $serverRoot;
+    }
+
+    /**
+     * Get a language instance
+     *
+     * @param string $app
+     * @param string|null $lang
+     * @param string|null $locale
+     * @return \OCP\IL10N
+     */
+    public function get($app, $lang = null, $locale = null) {
+        return new LazyL10N(function () use ($app, $lang, $locale) {
+            $app = \OC_App::cleanAppId($app);
+            if ($lang !== null) {
+                $lang = str_replace(['\0', '/', '\\', '..'], '', (string)$lang);
+            }
+
+            $forceLang = $this->config->getSystemValue('force_language', false);
+            if (is_string($forceLang)) {
+                $lang = $forceLang;
+            }
+
+            $forceLocale = $this->config->getSystemValue('force_locale', false);
+            if (is_string($forceLocale)) {
+                $locale = $forceLocale;
+            }
+
+            if ($lang === null || !$this->languageExists($app, $lang)) {
+                $lang = $this->findLanguage($app);
+            }
+
+            if ($locale === null || !$this->localeExists($locale)) {
+                $locale = $this->findLocale($lang);
+            }
+
+            if (!isset($this->instances[$lang][$app])) {
+                $this->instances[$lang][$app] = new L10N(
+                    $this, $app, $lang, $locale,
+                    $this->getL10nFilesForApp($app, $lang)
+                );
+            }
+
+            return $this->instances[$lang][$app];
+        });
+    }
+
+    /**
+     * Find the best language
+     *
+     * @param string|null $app App id or null for core
+     * @return string language If nothing works it returns 'en'
+     */
+    public function findLanguage($app = null) {
+        $forceLang = $this->config->getSystemValue('force_language', false);
+        if (is_string($forceLang)) {
+            $this->requestLanguage = $forceLang;
+        }
+
+        if ($this->requestLanguage !== '' && $this->languageExists($app, $this->requestLanguage)) {
+            return $this->requestLanguage;
+        }
+
+        /**
+         * At this point Nextcloud might not yet be installed and thus the lookup
+         * in the preferences table might fail. For this reason we need to check
+         * whether the instance has already been installed
+         *
+         * @link https://github.com/owncloud/core/issues/21955
+         */
+        if ($this->config->getSystemValue('installed', false)) {
+            $userId = !is_null($this->userSession->getUser()) ? $this->userSession->getUser()->getUID() :  null;
+            if (!is_null($userId)) {
+                $userLang = $this->config->getUserValue($userId, 'core', 'lang', null);
+            } else {
+                $userLang = null;
+            }
+        } else {
+            $userId = null;
+            $userLang = null;
+        }
+
+        if ($userLang) {
+            $this->requestLanguage = $userLang;
+            if ($this->languageExists($app, $userLang)) {
+                return $userLang;
+            }
+        }
+
+        try {
+            // Try to get the language from the Request
+            $lang = $this->getLanguageFromRequest($app);
+            if ($userId !== null && $app === null && !$userLang) {
+                $this->config->setUserValue($userId, 'core', 'lang', $lang);
+            }
+            return $lang;
+        } catch (LanguageNotFoundException $e) {
+            // Finding language from request failed fall back to default language
+            $defaultLanguage = $this->config->getSystemValue('default_language', false);
+            if ($defaultLanguage !== false && $this->languageExists($app, $defaultLanguage)) {
+                return $defaultLanguage;
+            }
+        }
+
+        // We could not find any language so fall back to english
+        return 'en';
+    }
+
+    /**
+     * find the best locale
+     *
+     * @param string $lang
+     * @return null|string
+     */
+    public function findLocale($lang = null) {
+        $forceLocale = $this->config->getSystemValue('force_locale', false);
+        if (is_string($forceLocale) && $this->localeExists($forceLocale)) {
+            return $forceLocale;
+        }
+
+        if ($this->config->getSystemValue('installed', false)) {
+            $userId = null !== $this->userSession->getUser() ? $this->userSession->getUser()->getUID() :  null;
+            $userLocale = null;
+            if (null !== $userId) {
+                $userLocale = $this->config->getUserValue($userId, 'core', 'locale', null);
+            }
+        } else {
+            $userId = null;
+            $userLocale = null;
+        }
+
+        if ($userLocale && $this->localeExists($userLocale)) {
+            return $userLocale;
+        }
+
+        // Default : use system default locale
+        $defaultLocale = $this->config->getSystemValue('default_locale', false);
+        if ($defaultLocale !== false && $this->localeExists($defaultLocale)) {
+            return $defaultLocale;
+        }
+
+        // If no user locale set, use lang as locale
+        if (null !== $lang && $this->localeExists($lang)) {
+            return $lang;
+        }
+
+        // At last, return USA
+        return 'en_US';
+    }
+
+    /**
+     * find the matching lang from the locale
+     *
+     * @param string $app
+     * @param string $locale
+     * @return null|string
+     */
+    public function findLanguageFromLocale(string $app = 'core', string $locale = null) {
+        if ($this->languageExists($app, $locale)) {
+            return $locale;
+        }
+
+        // Try to split e.g: fr_FR => fr
+        $locale = explode('_', $locale)[0];
+        if ($this->languageExists($app, $locale)) {
+            return $locale;
+        }
+    }
+
+    /**
+     * Find all available languages for an app
+     *
+     * @param string|null $app App id or null for core
+     * @return array an array of available languages
+     */
+    public function findAvailableLanguages($app = null) {
+        $key = $app;
+        if ($key === null) {
+            $key = 'null';
+        }
+
+        // also works with null as key
+        if (!empty($this->availableLanguages[$key])) {
+            return $this->availableLanguages[$key];
+        }
+
+        $available = ['en']; //english is always available
+        $dir = $this->findL10nDir($app);
+        if (is_dir($dir)) {
+            $files = scandir($dir);
+            if ($files !== false) {
+                foreach ($files as $file) {
+                    if (substr($file, -5) === '.json' && substr($file, 0, 4) !== 'l10n') {
+                        $available[] = substr($file, 0, -5);
+                    }
+                }
+            }
+        }
+
+        // merge with translations from theme
+        $theme = $this->config->getSystemValue('theme');
+        if (!empty($theme)) {
+            $themeDir = $this->serverRoot . '/themes/' . $theme . substr($dir, strlen($this->serverRoot));
+
+            if (is_dir($themeDir)) {
+                $files = scandir($themeDir);
+                if ($files !== false) {
+                    foreach ($files as $file) {
+                        if (substr($file, -5) === '.json' && substr($file, 0, 4) !== 'l10n') {
+                            $available[] = substr($file, 0, -5);
+                        }
+                    }
+                }
+            }
+        }
+
+        $this->availableLanguages[$key] = $available;
+        return $available;
+    }
+
+    /**
+     * @return array|mixed
+     */
+    public function findAvailableLocales() {
+        if (!empty($this->availableLocales)) {
+            return $this->availableLocales;
+        }
+
+        $localeData = file_get_contents(\OC::$SERVERROOT . '/resources/locales.json');
+        $this->availableLocales = \json_decode($localeData, true);
+
+        return $this->availableLocales;
+    }
+
+    /**
+     * @param string|null $app App id or null for core
+     * @param string $lang
+     * @return bool
+     */
+    public function languageExists($app, $lang) {
+        if ($lang === 'en') {//english is always available
+            return true;
+        }
+
+        $languages = $this->findAvailableLanguages($app);
+        return array_search($lang, $languages) !== false;
+    }
+
+    public function getLanguageIterator(IUser $user = null): ILanguageIterator {
+        $user = $user ?? $this->userSession->getUser();
+        if ($user === null) {
+            throw new \RuntimeException('Failed to get an IUser instance');
+        }
+        return new LanguageIterator($user, $this->config);
+    }
+
+    /**
+     * Return the language to use when sending something to a user
+     *
+     * @param IUser|null $user
+     * @return string
+     * @since 20.0.0
+     */
+    public function getUserLanguage(IUser $user = null): string {
+        $language = $this->config->getSystemValue('force_language', false);
+        if ($language !== false) {
+            return $language;
+        }
+
+        if ($user instanceof IUser) {
+            $language = $this->config->getUserValue($user->getUID(), 'core', 'lang', null);
+            if ($language !== null) {
+                return $language;
+            }
+        }
+
+        return $this->config->getSystemValue('default_language', 'en');
+    }
+
+    /**
+     * @param string $locale
+     * @return bool
+     */
+    public function localeExists($locale) {
+        if ($locale === 'en') { //english is always available
+            return true;
+        }
+
+        if ($this->localeCache === []) {
+            $locales = $this->findAvailableLocales();
+            foreach ($locales as $l) {
+                $this->localeCache[$l['code']] = true;
+            }
+        }
+
+        return isset($this->localeCache[$locale]);
+    }
+
+    /**
+     * @param string|null $app
+     * @return string
+     * @throws LanguageNotFoundException
+     */
+    private function getLanguageFromRequest($app) {
+        $header = $this->request->getHeader('ACCEPT_LANGUAGE');
+        if ($header !== '') {
+            $available = $this->findAvailableLanguages($app);
+
+            // E.g. make sure that 'de' is before 'de_DE'.
+            sort($available);
+
+            $preferences = preg_split('/,\s*/', strtolower($header));
+            foreach ($preferences as $preference) {
+                list($preferred_language) = explode(';', $preference);
+                $preferred_language = str_replace('-', '_', $preferred_language);
+
+                foreach ($available as $available_language) {
+                    if ($preferred_language === strtolower($available_language)) {
+                        return $this->respectDefaultLanguage($app, $available_language);
+                    }
+                }
+
+                // Fallback from de_De to de
+                foreach ($available as $available_language) {
+                    if (substr($preferred_language, 0, 2) === $available_language) {
+                        return $available_language;
+                    }
+                }
+            }
+        }
+
+        throw new LanguageNotFoundException();
+    }
+
+    /**
+     * if default language is set to de_DE (formal German) this should be
+     * preferred to 'de' (non-formal German) if possible
+     *
+     * @param string|null $app
+     * @param string $lang
+     * @return string
+     */
+    protected function respectDefaultLanguage($app, $lang) {
+        $result = $lang;
+        $defaultLanguage = $this->config->getSystemValue('default_language', false);
+
+        // use formal version of german ("Sie" instead of "Du") if the default
+        // language is set to 'de_DE' if possible
+        if (is_string($defaultLanguage) &&
+            strtolower($lang) === 'de' &&
+            strtolower($defaultLanguage) === 'de_de' &&
+            $this->languageExists($app, 'de_DE')
+        ) {
+            $result = 'de_DE';
+        }
+
+        return $result;
+    }
+
+    /**
+     * Checks if $sub is a subdirectory of $parent
+     *
+     * @param string $sub
+     * @param string $parent
+     * @return bool
+     */
+    private function isSubDirectory($sub, $parent) {
+        // Check whether $sub contains no ".."
+        if (strpos($sub, '..') !== false) {
+            return false;
+        }
+
+        // Check whether $sub is a subdirectory of $parent
+        if (strpos($sub, $parent) === 0) {
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Get a list of language files that should be loaded
+     *
+     * @param string $app
+     * @param string $lang
+     * @return string[]
+     */
+    // FIXME This method is only public, until OC_L10N does not need it anymore,
+    // FIXME This is also the reason, why it is not in the public interface
+    public function getL10nFilesForApp($app, $lang) {
+        $languageFiles = [];
+
+        $i18nDir = $this->findL10nDir($app);
+        $transFile = strip_tags($i18nDir) . strip_tags($lang) . '.json';
+
+        if (($this->isSubDirectory($transFile, $this->serverRoot . '/core/l10n/')
+                || $this->isSubDirectory($transFile, $this->serverRoot . '/lib/l10n/')
+                || $this->isSubDirectory($transFile, \OC_App::getAppPath($app) . '/l10n/')
+            )
+            && file_exists($transFile)) {
+            // load the translations file
+            $languageFiles[] = $transFile;
+        }
+
+        // merge with translations from theme
+        $theme = $this->config->getSystemValue('theme');
+        if (!empty($theme)) {
+            $transFile = $this->serverRoot . '/themes/' . $theme . substr($transFile, strlen($this->serverRoot));
+            if (file_exists($transFile)) {
+                $languageFiles[] = $transFile;
+            }
+        }
+
+        return $languageFiles;
+    }
+
+    /**
+     * find the l10n directory
+     *
+     * @param string $app App id or empty string for core
+     * @return string directory
+     */
+    protected function findL10nDir($app = null) {
+        if (in_array($app, ['core', 'lib'])) {
+            if (file_exists($this->serverRoot . '/' . $app . '/l10n/')) {
+                return $this->serverRoot . '/' . $app . '/l10n/';
+            }
+        } elseif ($app && \OC_App::getAppPath($app) !== false) {
+            // Check if the app is in the app folder
+            return \OC_App::getAppPath($app) . '/l10n/';
+        }
+        return $this->serverRoot . '/core/l10n/';
+    }
+
+
+    /**
+     * Creates a function from the plural string
+     *
+     * Parts of the code is copied from Habari:
+     * https://github.com/habari/system/blob/master/classes/locale.php
+     * @param string $string
+     * @return string
+     */
+    public function createPluralFunction($string) {
+        if (isset($this->pluralFunctions[$string])) {
+            return $this->pluralFunctions[$string];
+        }
+
+        if (preg_match('/^\s*nplurals\s*=\s*(\d+)\s*;\s*plural=(.*)$/u', $string, $matches)) {
+            // sanitize
+            $nplurals = preg_replace('/[^0-9]/', '', $matches[1]);
+            $plural = preg_replace('#[^n0-9:\(\)\?\|\&=!<>+*/\%-]#', '', $matches[2]);
+
+            $body = str_replace(
+                [ 'plural', 'n', '$n$plurals', ],
+                [ '$plural', '$n', '$nplurals', ],
+                'nplurals='. $nplurals . '; plural=' . $plural
+            );
+
+            // add parents
+            // important since PHP's ternary evaluates from left to right
+            $body .= ';';
+            $res = '';
+            $p = 0;
+            $length = strlen($body);
+            for ($i = 0; $i < $length; $i++) {
+                $ch = $body[$i];
+                switch ($ch) {
+                    case '?':
+                        $res .= ' ? (';
+                        $p++;
+                        break;
+                    case ':':
+                        $res .= ') : (';
+                        break;
+                    case ';':
+                        $res .= str_repeat(')', $p) . ';';
+                        $p = 0;
+                        break;
+                    default:
+                        $res .= $ch;
+                }
+            }
+
+            $body = $res . 'return ($plural>=$nplurals?$nplurals-1:$plural);';
+            $function = create_function('$n', $body);
+            $this->pluralFunctions[$string] = $function;
+            return $function;
+        } else {
+            // default: one plural form for all cases but n==1 (english)
+            $function = create_function(
+                '$n',
+                '$nplurals=2;$plural=($n==1?0:1);return ($plural>=$nplurals?$nplurals-1:$plural);'
+            );
+            $this->pluralFunctions[$string] = $function;
+            return $function;
+        }
+    }
+
+    /**
+     * returns the common language and other languages in an
+     * associative array
+     *
+     * @return array
+     */
+    public function getLanguages() {
+        $forceLanguage = $this->config->getSystemValue('force_language', false);
+        if ($forceLanguage !== false) {
+            $l = $this->get('lib', $forceLanguage);
+            $potentialName = (string) $l->t('__language_name__');
+
+            return [
+                'commonlanguages' => [[
+                    'code' => $forceLanguage,
+                    'name' => $potentialName,
+                ]],
+                'languages' => [],
+            ];
+        }
+
+        $languageCodes = $this->findAvailableLanguages();
+
+        $commonLanguages = [];
+        $languages = [];
+
+        foreach ($languageCodes as $lang) {
+            $l = $this->get('lib', $lang);
+            // TRANSLATORS this is the language name for the language switcher in the personal settings and should be the localized version
+            $potentialName = (string) $l->t('__language_name__');
+            if ($l->getLanguageCode() === $lang && $potentialName[0] !== '_') {//first check if the language name is in the translation file
+                $ln = [
+                    'code' => $lang,
+                    'name' => $potentialName
+                ];
+            } elseif ($lang === 'en') {
+                $ln = [
+                    'code' => $lang,
+                    'name' => 'English (US)'
+                ];
+            } else {//fallback to language code
+                $ln = [
+                    'code' => $lang,
+                    'name' => $lang
+                ];
+            }
+
+            // put appropriate languages into appropriate arrays, to print them sorted
+            // common languages -> divider -> other languages
+            if (in_array($lang, self::COMMON_LANGUAGE_CODES)) {
+                $commonLanguages[array_search($lang, self::COMMON_LANGUAGE_CODES)] = $ln;
+            } else {
+                $languages[] = $ln;
+            }
+        }
+
+        ksort($commonLanguages);
+
+        // sort now by displayed language not the iso-code
+        usort($languages, function ($a, $b) {
+            if ($a['code'] === $a['name'] && $b['code'] !== $b['name']) {
+                // If a doesn't have a name, but b does, list b before a
+                return 1;
+            }
+            if ($a['code'] !== $a['name'] && $b['code'] === $b['name']) {
+                // If a does have a name, but b doesn't, list a before b
+                return -1;
+            }
+            // Otherwise compare the names
+            return strcmp($a['name'], $b['name']);
+        });
+
+        return [
+            // reset indexes
+            'commonlanguages' => array_values($commonLanguages),
+            'languages' => $languages
+        ];
+    }
 }