1 files changed, 112 insertions, 0 deletions
diff --git a/lib/private/DateTimeZone.php b/lib/private/DateTimeZone.php
new file mode 100644
index 00000000000..c693968fa3d
--- /dev/null
+++ b/lib/private/DateTimeZone.php
@@ -0,0 +1,112 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+namespace OC;
+
+use OCP\IConfig;
+use OCP\IDateTimeZone;
+use OCP\ISession;
+use Psr\Log\LoggerInterface;
+
+class DateTimeZone implements IDateTimeZone {
+	/** @var IConfig */
+	protected $config;
+
+	/** @var ISession */
+	protected $session;
+
+	/**
+	 * Constructor
+	 *
+	 * @param IConfig $config
+	 * @param ISession $session
+	 */
+	public function __construct(IConfig $config, ISession $session) {
+		$this->config = $config;
+		$this->session = $session;
+	}
+
+	/**
+	 * Get the timezone of the current user, based on their session information and config data
+	 *
+	 * @param bool|int $timestamp
+	 * @return \DateTimeZone
+	 */
+	public function getTimeZone($timestamp = false) {
+		$timeZone = $this->config->getUserValue($this->session->get('user_id'), 'core', 'timezone', null);
+		if ($timeZone === null) {
+			if ($this->session->exists('timezone')) {
+				return $this->guessTimeZoneFromOffset($this->session->get('timezone'), $timestamp);
+			}
+			$timeZone = $this->getDefaultTimeZone();
+		}
+
+		try {
+			return new \DateTimeZone($timeZone);
+		} catch (\Exception $e) {
+			\OC::$server->get(LoggerInterface::class)->debug('Failed to created DateTimeZone "' . $timeZone . '"', ['app' => 'datetimezone']);
+			return new \DateTimeZone($this->getDefaultTimeZone());
+		}
+	}
+
+	/**
+	 * Guess the DateTimeZone for a given offset
+	 *
+	 * We first try to find a Etc/GMT* timezone, if that does not exist,
+	 * we try to find it manually, before falling back to UTC.
+	 *
+	 * @param mixed $offset
+	 * @param bool|int $timestamp
+	 * @return \DateTimeZone
+	 */
+	protected function guessTimeZoneFromOffset($offset, $timestamp) {
+		try {
+			// Note: the timeZone name is the inverse to the offset,
+			// so a positive offset means negative timeZone
+			// and the other way around.
+			if ($offset > 0) {
+				$timeZone = 'Etc/GMT-' . $offset;
+			} else {
+				$timeZone = 'Etc/GMT+' . abs($offset);
+			}
+
+			return new \DateTimeZone($timeZone);
+		} catch (\Exception $e) {
+			// If the offset has no Etc/GMT* timezone,
+			// we try to guess one timezone that has the same offset
+			foreach (\DateTimeZone::listIdentifiers() as $timeZone) {
+				$dtz = new \DateTimeZone($timeZone);
+				$dateTime = new \DateTime();
+
+				if ($timestamp !== false) {
+					$dateTime->setTimestamp($timestamp);
+				}
+
+				$dtOffset = $dtz->getOffset($dateTime);
+				if ($dtOffset == 3600 * $offset) {
+					return $dtz;
+				}
+			}
+
+			// No timezone found, fallback to UTC
+			\OC::$server->get(LoggerInterface::class)->debug('Failed to find DateTimeZone for offset "' . $offset . '"', ['app' => 'datetimezone']);
+			return new \DateTimeZone($this->getDefaultTimeZone());
+		}
+	}
+
+	/**
+	 * Get the default timezone of the server
+	 *
+	 * Falls back to UTC if it is not yet set.
+	 *
+	 * @return string
+	 */
+	protected function getDefaultTimeZone() {
+		$serverTimeZone = date_default_timezone_get();
+		return $serverTimeZone ?: 'UTC';
+	}
+}