nextcloud / server

apps/dav/lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php

Indentation +442 added lines, -442 removed lines

@@ -51,446 +51,446 @@
  */
 class EmailProvider extends AbstractProvider {
 
-	/** @var string */
-	public const NOTIFICATION_TYPE = 'EMAIL';
-
-	/** @var IMailer */
-	private $mailer;
-
-	/**
-	 * @param IConfig $config
-	 * @param IMailer $mailer
-	 * @param ILogger $logger
-	 * @param L10NFactory $l10nFactory
-	 * @param IUrlGenerator $urlGenerator
-	 */
-	public function __construct(IConfig $config,
-								IMailer $mailer,
-								ILogger $logger,
-								L10NFactory $l10nFactory,
-								IURLGenerator $urlGenerator) {
-		parent::__construct($logger, $l10nFactory, $urlGenerator, $config);
-		$this->mailer = $mailer;
-	}
-
-	/**
-	 * Send out notification via email
-	 *
-	 * @param VEvent $vevent
-	 * @param string $calendarDisplayName
-	 * @param array $users
-	 * @throws \Exception
-	 */
-	public function send(VEvent $vevent,
-						 string $calendarDisplayName,
-						 array $users = []):void {
-		$fallbackLanguage = $this->getFallbackLanguage();
-
-		$emailAddressesOfSharees = $this->getEMailAddressesOfAllUsersWithWriteAccessToCalendar($users);
-		$emailAddressesOfAttendees = $this->getAllEMailAddressesFromEvent($vevent);
-
-		// Quote from php.net:
-		// If the input arrays have the same string keys, then the later value for that key will overwrite the previous one.
-		// => if there are duplicate email addresses, it will always take the system value
-		$emailAddresses = array_merge(
-			$emailAddressesOfAttendees,
-			$emailAddressesOfSharees
-		);
-
-		$sortedByLanguage = $this->sortEMailAddressesByLanguage($emailAddresses, $fallbackLanguage);
-		$organizer = $this->getOrganizerEMailAndNameFromEvent($vevent);
-
-		foreach ($sortedByLanguage as $lang => $emailAddresses) {
-			if (!$this->hasL10NForLang($lang)) {
-				$lang = $fallbackLanguage;
-			}
-			$l10n = $this->getL10NForLang($lang);
-			$fromEMail = \OCP\Util::getDefaultEmailAddress('reminders-noreply');
-
-			$template = $this->mailer->createEMailTemplate('dav.calendarReminder');
-			$template->addHeader();
-			$this->addSubjectAndHeading($template, $l10n, $vevent);
-			$this->addBulletList($template, $l10n, $calendarDisplayName, $vevent);
-			$template->addFooter();
-
-			foreach ($emailAddresses as $emailAddress) {
-				$message = $this->mailer->createMessage();
-				$message->setFrom([$fromEMail]);
-				if ($organizer) {
-					$message->setReplyTo($organizer);
-				}
-				$message->setTo([$emailAddress]);
-				$message->useTemplate($template);
-
-				try {
-					$failed = $this->mailer->send($message);
-					if ($failed) {
-						$this->logger->error('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' => implode(', ', $failed)]);
-					}
-				} catch (\Exception $ex) {
-					$this->logger->logException($ex, ['app' => 'dav']);
-				}
-			}
-		}
-	}
-
-	/**
-	 * @param IEMailTemplate $template
-	 * @param IL10N $l10n
-	 * @param VEvent $vevent
-	 */
-	private function addSubjectAndHeading(IEMailTemplate $template, IL10N $l10n, VEvent $vevent):void {
-		$template->setSubject('Notification: ' . $this->getTitleFromVEvent($vevent, $l10n));
-		$template->addHeading($this->getTitleFromVEvent($vevent, $l10n));
-	}
-
-	/**
-	 * @param IEMailTemplate $template
-	 * @param IL10N $l10n
-	 * @param string $calendarDisplayName
-	 * @param array $eventData
-	 */
-	private function addBulletList(IEMailTemplate $template,
-								   IL10N $l10n,
-								   string $calendarDisplayName,
-								   VEvent $vevent):void {
-		$template->addBodyListItem($calendarDisplayName, $l10n->t('Calendar:'),
-			$this->getAbsoluteImagePath('actions/info.png'));
-
-		$template->addBodyListItem($this->generateDateString($l10n, $vevent), $l10n->t('Date:'),
-			$this->getAbsoluteImagePath('places/calendar.png'));
-
-		if (isset($vevent->LOCATION)) {
-			$template->addBodyListItem((string) $vevent->LOCATION, $l10n->t('Where:'),
-				$this->getAbsoluteImagePath('actions/address.png'));
-		}
-		if (isset($vevent->DESCRIPTION)) {
-			$template->addBodyListItem((string) $vevent->DESCRIPTION, $l10n->t('Description:'),
-				$this->getAbsoluteImagePath('actions/more.png'));
-		}
-	}
-
-	/**
-	 * @param string $path
-	 * @return string
-	 */
-	private function getAbsoluteImagePath(string $path):string {
-		return $this->urlGenerator->getAbsoluteURL(
-			$this->urlGenerator->imagePath('core', $path)
-		);
-	}
-
-	/**
-	 * @param VEvent $vevent
-	 * @return array|null
-	 */
-	private function getOrganizerEMailAndNameFromEvent(VEvent $vevent):?array {
-		if (!$vevent->ORGANIZER) {
-			return null;
-		}
-
-		$organizer = $vevent->ORGANIZER;
-		if (strcasecmp($organizer->getValue(), 'mailto:') !== 0) {
-			return null;
-		}
-
-		$organizerEMail = substr($organizer->getValue(), 7);
-
-		$name = $organizer->offsetGet('CN');
-		if ($name instanceof Parameter) {
-			return [$organizerEMail => $name];
-		}
-
-		return [$organizerEMail];
-	}
-
-	/**
-	 * @param array $emails
-	 * @param string $defaultLanguage
-	 * @return array
-	 */
-	private function sortEMailAddressesByLanguage(array $emails,
-												  string $defaultLanguage):array {
-		$sortedByLanguage = [];
-
-		foreach ($emails as $emailAddress => $parameters) {
-			if (isset($parameters['LANG'])) {
-				$lang = $parameters['LANG'];
-			} else {
-				$lang = $defaultLanguage;
-			}
-
-			if (!isset($sortedByLanguage[$lang])) {
-				$sortedByLanguage[$lang] = [];
-			}
-
-			$sortedByLanguage[$lang][] = $emailAddress;
-		}
-
-		return $sortedByLanguage;
-	}
-
-	/**
-	 * @param VEvent $vevent
-	 * @return array
-	 */
-	private function getAllEMailAddressesFromEvent(VEvent $vevent):array {
-		$emailAddresses = [];
-
-		if (isset($vevent->ATTENDEE)) {
-			foreach ($vevent->ATTENDEE as $attendee) {
-				if (!($attendee instanceof VObject\Property)) {
-					continue;
-				}
-
-				$cuType = $this->getCUTypeOfAttendee($attendee);
-				if (\in_array($cuType, ['RESOURCE', 'ROOM', 'UNKNOWN'])) {
-					// Don't send emails to things
-					continue;
-				}
-
-				$partstat = $this->getPartstatOfAttendee($attendee);
-				if ($partstat === 'DECLINED') {
-					// Don't send out emails to people who declined
-					continue;
-				}
-				if ($partstat === 'DELEGATED') {
-					$delegates = $attendee->offsetGet('DELEGATED-TO');
-					if (!($delegates instanceof VObject\Parameter)) {
-						continue;
-					}
-
-					$emailAddressesOfDelegates = $delegates->getParts();
-					foreach ($emailAddressesOfDelegates as $addressesOfDelegate) {
-						if (strcasecmp($addressesOfDelegate, 'mailto:') === 0) {
-							$emailAddresses[substr($addressesOfDelegate, 7)] = [];
-						}
-					}
-
-					continue;
-				}
-
-				$emailAddressOfAttendee = $this->getEMailAddressOfAttendee($attendee);
-				if ($emailAddressOfAttendee !== null) {
-					$properties = [];
-
-					$langProp = $attendee->offsetGet('LANG');
-					if ($langProp instanceof VObject\Parameter) {
-						$properties['LANG'] = $langProp->getValue();
-					}
-
-					$emailAddresses[$emailAddressOfAttendee] = $properties;
-				}
-			}
-		}
-
-		if (isset($vevent->ORGANIZER) && $this->hasAttendeeMailURI($vevent->ORGANIZER)) {
-			$emailAddresses[$this->getEMailAddressOfAttendee($vevent->ORGANIZER)] = [];
-		}
-
-		return $emailAddresses;
-	}
-
-
-
-	/**
-	 * @param VObject\Property $attendee
-	 * @return string
-	 */
-	private function getCUTypeOfAttendee(VObject\Property $attendee):string {
-		$cuType = $attendee->offsetGet('CUTYPE');
-		if ($cuType instanceof VObject\Parameter) {
-			return strtoupper($cuType->getValue());
-		}
-
-		return 'INDIVIDUAL';
-	}
-
-	/**
-	 * @param VObject\Property $attendee
-	 * @return string
-	 */
-	private function getPartstatOfAttendee(VObject\Property $attendee):string {
-		$partstat = $attendee->offsetGet('PARTSTAT');
-		if ($partstat instanceof VObject\Parameter) {
-			return strtoupper($partstat->getValue());
-		}
-
-		return 'NEEDS-ACTION';
-	}
-
-	/**
-	 * @param VObject\Property $attendee
-	 * @return bool
-	 */
-	private function hasAttendeeMailURI(VObject\Property $attendee):bool {
-		return stripos($attendee->getValue(), 'mailto:') === 0;
-	}
-
-	/**
-	 * @param VObject\Property $attendee
-	 * @return string|null
-	 */
-	private function getEMailAddressOfAttendee(VObject\Property $attendee):?string {
-		if (!$this->hasAttendeeMailURI($attendee)) {
-			return null;
-		}
-
-		return substr($attendee->getValue(), 7);
-	}
-
-	/**
-	 * @param array $users
-	 * @return array
-	 */
-	private function getEMailAddressesOfAllUsersWithWriteAccessToCalendar(array $users):array {
-		$emailAddresses = [];
-
-		foreach ($users as $user) {
-			$emailAddress = $user->getEMailAddress();
-			if ($emailAddress) {
-				$lang = $this->l10nFactory->getUserLanguage($user);
-				if ($lang) {
-					$emailAddresses[$emailAddress] = [
-						'LANG' => $lang,
-					];
-				} else {
-					$emailAddresses[$emailAddress] = [];
-				}
-			}
-		}
-
-		return $emailAddresses;
-	}
-
-	/**
-	 * @param IL10N $l10n
-	 * @param VEvent $vevent
-	 * @return string
-	 * @throws \Exception
-	 */
-	private function generateDateString(IL10N $l10n, VEvent $vevent):string {
-		$isAllDay = $vevent->DTSTART instanceof Property\ICalendar\Date;
-
-		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtstart */
-		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtend */
-		/** @var \DateTimeImmutable $dtstartDt */
-		$dtstartDt = $vevent->DTSTART->getDateTime();
-		/** @var \DateTimeImmutable $dtendDt */
-		$dtendDt = $this->getDTEndFromEvent($vevent)->getDateTime();
-
-		$diff = $dtstartDt->diff($dtendDt);
-
-		$dtstartDt = new \DateTime($dtstartDt->format(\DateTime::ATOM));
-		$dtendDt = new \DateTime($dtendDt->format(\DateTime::ATOM));
-
-		if ($isAllDay) {
-			// One day event
-			if ($diff->days === 1) {
-				return $this->getDateString($l10n, $dtstartDt);
-			}
-
-			return implode(' - ', [
-				$this->getDateString($l10n, $dtstartDt),
-				$this->getDateString($l10n, $dtendDt),
-			]);
-		}
-
-		$startTimezone = $endTimezone = null;
-		if (!$vevent->DTSTART->isFloating()) {
-			$startTimezone = $vevent->DTSTART->getDateTime()->getTimezone()->getName();
-			$endTimezone = $this->getDTEndFromEvent($vevent)->getDateTime()->getTimezone()->getName();
-		}
-
-		$localeStart = implode(', ', [
-			$this->getWeekDayName($l10n, $dtstartDt),
-			$this->getDateTimeString($l10n, $dtstartDt)
-		]);
-
-		// always show full date with timezone if timezones are different
-		if ($startTimezone !== $endTimezone) {
-			$localeEnd = implode(', ', [
-				$this->getWeekDayName($l10n, $dtendDt),
-				$this->getDateTimeString($l10n, $dtendDt)
-			]);
-
-			return $localeStart
-				. ' (' . $startTimezone . ') '
-				. ' - '
-				. $localeEnd
-				. ' (' . $endTimezone . ')';
-		}
-
-		// Show only the time if the day is the same
-		$localeEnd = $this->isDayEqual($dtstartDt, $dtendDt)
-			? $this->getTimeString($l10n, $dtendDt)
-			: implode(', ', [
-				$this->getWeekDayName($l10n, $dtendDt),
-				$this->getDateTimeString($l10n, $dtendDt)
-			]);
-
-		return $localeStart
-			. ' - '
-			. $localeEnd
-			. ' (' . $startTimezone . ')';
-	}
-
-	/**
-	 * @param DateTime $dtStart
-	 * @param DateTime $dtEnd
-	 * @return bool
-	 */
-	private function isDayEqual(DateTime $dtStart,
-								DateTime $dtEnd):bool {
-		return $dtStart->format('Y-m-d') === $dtEnd->format('Y-m-d');
-	}
-
-	/**
-	 * @param IL10N $l10n
-	 * @param DateTime $dt
-	 * @return string
-	 */
-	private function getWeekDayName(IL10N $l10n, DateTime $dt):string {
-		return $l10n->l('weekdayName', $dt, ['width' => 'abbreviated']);
-	}
-
-	/**
-	 * @param IL10N $l10n
-	 * @param DateTime $dt
-	 * @return string
-	 */
-	private function getDateString(IL10N $l10n, DateTime $dt):string {
-		return $l10n->l('date', $dt, ['width' => 'medium']);
-	}
-
-	/**
-	 * @param IL10N $l10n
-	 * @param DateTime $dt
-	 * @return string
-	 */
-	private function getDateTimeString(IL10N $l10n, DateTime $dt):string {
-		return $l10n->l('datetime', $dt, ['width' => 'medium|short']);
-	}
-
-	/**
-	 * @param IL10N $l10n
-	 * @param DateTime $dt
-	 * @return string
-	 */
-	private function getTimeString(IL10N $l10n, DateTime $dt):string {
-		return $l10n->l('time', $dt, ['width' => 'short']);
-	}
-
-	/**
-	 * @param VEvent $vevent
-	 * @param IL10N $l10n
-	 * @return string
-	 */
-	private function getTitleFromVEvent(VEvent $vevent, IL10N $l10n):string {
-		if (isset($vevent->SUMMARY)) {
-			return (string)$vevent->SUMMARY;
-		}
-
-		return $l10n->t('Untitled event');
-	}
+    /** @var string */
+    public const NOTIFICATION_TYPE = 'EMAIL';
+
+    /** @var IMailer */
+    private $mailer;
+
+    /**
+     * @param IConfig $config
+     * @param IMailer $mailer
+     * @param ILogger $logger
+     * @param L10NFactory $l10nFactory
+     * @param IUrlGenerator $urlGenerator
+     */
+    public function __construct(IConfig $config,
+                                IMailer $mailer,
+                                ILogger $logger,
+                                L10NFactory $l10nFactory,
+                                IURLGenerator $urlGenerator) {
+        parent::__construct($logger, $l10nFactory, $urlGenerator, $config);
+        $this->mailer = $mailer;
+    }
+
+    /**
+     * Send out notification via email
+     *
+     * @param VEvent $vevent
+     * @param string $calendarDisplayName
+     * @param array $users
+     * @throws \Exception
+     */
+    public function send(VEvent $vevent,
+                            string $calendarDisplayName,
+                            array $users = []):void {
+        $fallbackLanguage = $this->getFallbackLanguage();
+
+        $emailAddressesOfSharees = $this->getEMailAddressesOfAllUsersWithWriteAccessToCalendar($users);
+        $emailAddressesOfAttendees = $this->getAllEMailAddressesFromEvent($vevent);
+
+        // Quote from php.net:
+        // If the input arrays have the same string keys, then the later value for that key will overwrite the previous one.
+        // => if there are duplicate email addresses, it will always take the system value
+        $emailAddresses = array_merge(
+            $emailAddressesOfAttendees,
+            $emailAddressesOfSharees
+        );
+
+        $sortedByLanguage = $this->sortEMailAddressesByLanguage($emailAddresses, $fallbackLanguage);
+        $organizer = $this->getOrganizerEMailAndNameFromEvent($vevent);
+
+        foreach ($sortedByLanguage as $lang => $emailAddresses) {
+            if (!$this->hasL10NForLang($lang)) {
+                $lang = $fallbackLanguage;
+            }
+            $l10n = $this->getL10NForLang($lang);
+            $fromEMail = \OCP\Util::getDefaultEmailAddress('reminders-noreply');
+
+            $template = $this->mailer->createEMailTemplate('dav.calendarReminder');
+            $template->addHeader();
+            $this->addSubjectAndHeading($template, $l10n, $vevent);
+            $this->addBulletList($template, $l10n, $calendarDisplayName, $vevent);
+            $template->addFooter();
+
+            foreach ($emailAddresses as $emailAddress) {
+                $message = $this->mailer->createMessage();
+                $message->setFrom([$fromEMail]);
+                if ($organizer) {
+                    $message->setReplyTo($organizer);
+                }
+                $message->setTo([$emailAddress]);
+                $message->useTemplate($template);
+
+                try {
+                    $failed = $this->mailer->send($message);
+                    if ($failed) {
+                        $this->logger->error('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' => implode(', ', $failed)]);
+                    }
+                } catch (\Exception $ex) {
+                    $this->logger->logException($ex, ['app' => 'dav']);
+                }
+            }
+        }
+    }
+
+    /**
+     * @param IEMailTemplate $template
+     * @param IL10N $l10n
+     * @param VEvent $vevent
+     */
+    private function addSubjectAndHeading(IEMailTemplate $template, IL10N $l10n, VEvent $vevent):void {
+        $template->setSubject('Notification: ' . $this->getTitleFromVEvent($vevent, $l10n));
+        $template->addHeading($this->getTitleFromVEvent($vevent, $l10n));
+    }
+
+    /**
+     * @param IEMailTemplate $template
+     * @param IL10N $l10n
+     * @param string $calendarDisplayName
+     * @param array $eventData
+     */
+    private function addBulletList(IEMailTemplate $template,
+                                    IL10N $l10n,
+                                    string $calendarDisplayName,
+                                    VEvent $vevent):void {
+        $template->addBodyListItem($calendarDisplayName, $l10n->t('Calendar:'),
+            $this->getAbsoluteImagePath('actions/info.png'));
+
+        $template->addBodyListItem($this->generateDateString($l10n, $vevent), $l10n->t('Date:'),
+            $this->getAbsoluteImagePath('places/calendar.png'));
+
+        if (isset($vevent->LOCATION)) {
+            $template->addBodyListItem((string) $vevent->LOCATION, $l10n->t('Where:'),
+                $this->getAbsoluteImagePath('actions/address.png'));
+        }
+        if (isset($vevent->DESCRIPTION)) {
+            $template->addBodyListItem((string) $vevent->DESCRIPTION, $l10n->t('Description:'),
+                $this->getAbsoluteImagePath('actions/more.png'));
+        }
+    }
+
+    /**
+     * @param string $path
+     * @return string
+     */
+    private function getAbsoluteImagePath(string $path):string {
+        return $this->urlGenerator->getAbsoluteURL(
+            $this->urlGenerator->imagePath('core', $path)
+        );
+    }
+
+    /**
+     * @param VEvent $vevent
+     * @return array|null
+     */
+    private function getOrganizerEMailAndNameFromEvent(VEvent $vevent):?array {
+        if (!$vevent->ORGANIZER) {
+            return null;
+        }
+
+        $organizer = $vevent->ORGANIZER;
+        if (strcasecmp($organizer->getValue(), 'mailto:') !== 0) {
+            return null;
+        }
+
+        $organizerEMail = substr($organizer->getValue(), 7);
+
+        $name = $organizer->offsetGet('CN');
+        if ($name instanceof Parameter) {
+            return [$organizerEMail => $name];
+        }
+
+        return [$organizerEMail];
+    }
+
+    /**
+     * @param array $emails
+     * @param string $defaultLanguage
+     * @return array
+     */
+    private function sortEMailAddressesByLanguage(array $emails,
+                                                    string $defaultLanguage):array {
+        $sortedByLanguage = [];
+
+        foreach ($emails as $emailAddress => $parameters) {
+            if (isset($parameters['LANG'])) {
+                $lang = $parameters['LANG'];
+            } else {
+                $lang = $defaultLanguage;
+            }
+
+            if (!isset($sortedByLanguage[$lang])) {
+                $sortedByLanguage[$lang] = [];
+            }
+
+            $sortedByLanguage[$lang][] = $emailAddress;
+        }
+
+        return $sortedByLanguage;
+    }
+
+    /**
+     * @param VEvent $vevent
+     * @return array
+     */
+    private function getAllEMailAddressesFromEvent(VEvent $vevent):array {
+        $emailAddresses = [];
+
+        if (isset($vevent->ATTENDEE)) {
+            foreach ($vevent->ATTENDEE as $attendee) {
+                if (!($attendee instanceof VObject\Property)) {
+                    continue;
+                }
+
+                $cuType = $this->getCUTypeOfAttendee($attendee);
+                if (\in_array($cuType, ['RESOURCE', 'ROOM', 'UNKNOWN'])) {
+                    // Don't send emails to things
+                    continue;
+                }
+
+                $partstat = $this->getPartstatOfAttendee($attendee);
+                if ($partstat === 'DECLINED') {
+                    // Don't send out emails to people who declined
+                    continue;
+                }
+                if ($partstat === 'DELEGATED') {
+                    $delegates = $attendee->offsetGet('DELEGATED-TO');
+                    if (!($delegates instanceof VObject\Parameter)) {
+                        continue;
+                    }
+
+                    $emailAddressesOfDelegates = $delegates->getParts();
+                    foreach ($emailAddressesOfDelegates as $addressesOfDelegate) {
+                        if (strcasecmp($addressesOfDelegate, 'mailto:') === 0) {
+                            $emailAddresses[substr($addressesOfDelegate, 7)] = [];
+                        }
+                    }
+
+                    continue;
+                }
+
+                $emailAddressOfAttendee = $this->getEMailAddressOfAttendee($attendee);
+                if ($emailAddressOfAttendee !== null) {
+                    $properties = [];
+
+                    $langProp = $attendee->offsetGet('LANG');
+                    if ($langProp instanceof VObject\Parameter) {
+                        $properties['LANG'] = $langProp->getValue();
+                    }
+
+                    $emailAddresses[$emailAddressOfAttendee] = $properties;
+                }
+            }
+        }
+
+        if (isset($vevent->ORGANIZER) && $this->hasAttendeeMailURI($vevent->ORGANIZER)) {
+            $emailAddresses[$this->getEMailAddressOfAttendee($vevent->ORGANIZER)] = [];
+        }
+
+        return $emailAddresses;
+    }
+
+
+
+    /**
+     * @param VObject\Property $attendee
+     * @return string
+     */
+    private function getCUTypeOfAttendee(VObject\Property $attendee):string {
+        $cuType = $attendee->offsetGet('CUTYPE');
+        if ($cuType instanceof VObject\Parameter) {
+            return strtoupper($cuType->getValue());
+        }
+
+        return 'INDIVIDUAL';
+    }
+
+    /**
+     * @param VObject\Property $attendee
+     * @return string
+     */
+    private function getPartstatOfAttendee(VObject\Property $attendee):string {
+        $partstat = $attendee->offsetGet('PARTSTAT');
+        if ($partstat instanceof VObject\Parameter) {
+            return strtoupper($partstat->getValue());
+        }
+
+        return 'NEEDS-ACTION';
+    }
+
+    /**
+     * @param VObject\Property $attendee
+     * @return bool
+     */
+    private function hasAttendeeMailURI(VObject\Property $attendee):bool {
+        return stripos($attendee->getValue(), 'mailto:') === 0;
+    }
+
+    /**
+     * @param VObject\Property $attendee
+     * @return string|null
+     */
+    private function getEMailAddressOfAttendee(VObject\Property $attendee):?string {
+        if (!$this->hasAttendeeMailURI($attendee)) {
+            return null;
+        }
+
+        return substr($attendee->getValue(), 7);
+    }
+
+    /**
+     * @param array $users
+     * @return array
+     */
+    private function getEMailAddressesOfAllUsersWithWriteAccessToCalendar(array $users):array {
+        $emailAddresses = [];
+
+        foreach ($users as $user) {
+            $emailAddress = $user->getEMailAddress();
+            if ($emailAddress) {
+                $lang = $this->l10nFactory->getUserLanguage($user);
+                if ($lang) {
+                    $emailAddresses[$emailAddress] = [
+                        'LANG' => $lang,
+                    ];
+                } else {
+                    $emailAddresses[$emailAddress] = [];
+                }
+            }
+        }
+
+        return $emailAddresses;
+    }
+
+    /**
+     * @param IL10N $l10n
+     * @param VEvent $vevent
+     * @return string
+     * @throws \Exception
+     */
+    private function generateDateString(IL10N $l10n, VEvent $vevent):string {
+        $isAllDay = $vevent->DTSTART instanceof Property\ICalendar\Date;
+
+        /** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtstart */
+        /** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtend */
+        /** @var \DateTimeImmutable $dtstartDt */
+        $dtstartDt = $vevent->DTSTART->getDateTime();
+        /** @var \DateTimeImmutable $dtendDt */
+        $dtendDt = $this->getDTEndFromEvent($vevent)->getDateTime();
+
+        $diff = $dtstartDt->diff($dtendDt);
+
+        $dtstartDt = new \DateTime($dtstartDt->format(\DateTime::ATOM));
+        $dtendDt = new \DateTime($dtendDt->format(\DateTime::ATOM));
+
+        if ($isAllDay) {
+            // One day event
+            if ($diff->days === 1) {
+                return $this->getDateString($l10n, $dtstartDt);
+            }
+
+            return implode(' - ', [
+                $this->getDateString($l10n, $dtstartDt),
+                $this->getDateString($l10n, $dtendDt),
+            ]);
+        }
+
+        $startTimezone = $endTimezone = null;
+        if (!$vevent->DTSTART->isFloating()) {
+            $startTimezone = $vevent->DTSTART->getDateTime()->getTimezone()->getName();
+            $endTimezone = $this->getDTEndFromEvent($vevent)->getDateTime()->getTimezone()->getName();
+        }
+
+        $localeStart = implode(', ', [
+            $this->getWeekDayName($l10n, $dtstartDt),
+            $this->getDateTimeString($l10n, $dtstartDt)
+        ]);
+
+        // always show full date with timezone if timezones are different
+        if ($startTimezone !== $endTimezone) {
+            $localeEnd = implode(', ', [
+                $this->getWeekDayName($l10n, $dtendDt),
+                $this->getDateTimeString($l10n, $dtendDt)
+            ]);
+
+            return $localeStart
+                . ' (' . $startTimezone . ') '
+                . ' - '
+                . $localeEnd
+                . ' (' . $endTimezone . ')';
+        }
+
+        // Show only the time if the day is the same
+        $localeEnd = $this->isDayEqual($dtstartDt, $dtendDt)
+            ? $this->getTimeString($l10n, $dtendDt)
+            : implode(', ', [
+                $this->getWeekDayName($l10n, $dtendDt),
+                $this->getDateTimeString($l10n, $dtendDt)
+            ]);
+
+        return $localeStart
+            . ' - '
+            . $localeEnd
+            . ' (' . $startTimezone . ')';
+    }
+
+    /**
+     * @param DateTime $dtStart
+     * @param DateTime $dtEnd
+     * @return bool
+     */
+    private function isDayEqual(DateTime $dtStart,
+                                DateTime $dtEnd):bool {
+        return $dtStart->format('Y-m-d') === $dtEnd->format('Y-m-d');
+    }
+
+    /**
+     * @param IL10N $l10n
+     * @param DateTime $dt
+     * @return string
+     */
+    private function getWeekDayName(IL10N $l10n, DateTime $dt):string {
+        return $l10n->l('weekdayName', $dt, ['width' => 'abbreviated']);
+    }
+
+    /**
+     * @param IL10N $l10n
+     * @param DateTime $dt
+     * @return string
+     */
+    private function getDateString(IL10N $l10n, DateTime $dt):string {
+        return $l10n->l('date', $dt, ['width' => 'medium']);
+    }
+
+    /**
+     * @param IL10N $l10n
+     * @param DateTime $dt
+     * @return string
+     */
+    private function getDateTimeString(IL10N $l10n, DateTime $dt):string {
+        return $l10n->l('datetime', $dt, ['width' => 'medium|short']);
+    }
+
+    /**
+     * @param IL10N $l10n
+     * @param DateTime $dt
+     * @return string
+     */
+    private function getTimeString(IL10N $l10n, DateTime $dt):string {
+        return $l10n->l('time', $dt, ['width' => 'short']);
+    }
+
+    /**
+     * @param VEvent $vevent
+     * @param IL10N $l10n
+     * @return string
+     */
+    private function getTitleFromVEvent(VEvent $vevent, IL10N $l10n):string {
+        if (isset($vevent->SUMMARY)) {
+            return (string)$vevent->SUMMARY;
+        }
+
+        return $l10n->t('Untitled event');
+    }
 }