owncloud/core

<?php
/**
 * @author Joas Schilling <coding@schilljs.com>
 * @author Morris Jobke <hey@morrisjobke.de>
 *
 * @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/>
 *
 */

namespace OC;

use OCP\IConfig;
use OCP\IDateTimeZone;
use OCP\ISession;

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 his 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) {
            \OCP\Util::writeLog('datetimezone', 'Failed to created DateTimeZone "' . $timeZone . "'", \OCP\Util::DEBUG);
            return new \DateTimeZone($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
            \OCP\Util::writeLog('datetimezone', 'Failed to find DateTimeZone for offset "' . $offset . "'", \OCP\Util::DEBUG);
            return new \DateTimeZone($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';
    }
}