Implementation of nextcloud#12885

Signed-off-by: hdijkema <hans@dykema.nl>

apps/dav/lib/CalDAV/Schedule/IMipPlugin.php

@@ -244,12 +244,51 @@ public function schedule(Message $iTipMessage) {
 		$template->addFooter();
 		$message->useTemplate($template);
 
-		$attachment = $this->mailer->createAttachment(
-			$iTipMessage->message->serialize(),
-			'event.ics',// TODO(leon): Make file name unique, e.g. add event id
-			'text/calendar; method=' . $iTipMessage->method
+		# We choose to work like thinderbird Lightning.
+		# using a plain text text/calendar ics.
+		# This plain text text/calendar part is needed for
+		# Microsoft Outlook versions <=2010 to work.
+
+		# The attachment base64 text/calendar part is removed from the code
+		#$attachment = $this->mailer->createAttachment(
+		#	$iTipMessage->message->serialize(),
+		#	'event.ics',// TODO(leon): Make file name unique, e.g. add event id
+		#	'text/calendar; method=' . $iTipMessage->method
+		#);
+		#$message->attach($attachment);
+
+		# The plain text text/calendar part is added to the code, but we need
+		# to do something more. Outlook (2010 and 2016 tested) has problems with canceled messages
+		# that contain Time Zone Identifications (e.g. ;TZID=Europe/Amsterdam:).
+		# A 'not-supported-calendar-message.ics' is shown and the cancellation is not recognized.
+		#
+		# See e.g.: https://stackoverflow.com/questions/48550054/icalendar-appointment-is-a-not-supported-calendar-message-ics
+		#
+		# To work around this problem, DTSTART and DTEND are converted to UTC.
+		# UTC date/times work in all situations.
+
+		$utc_tz = new \DateTimeZone("UTC");
+
+		$cvt_dtstart = $start;
+		$cvt_dtstart_dt = $cvt_dtstart->getDateTime();
+		$dtstart_ts = $cvt_dtstart_dt->getTimestamp();
+		$cvt_dtstart_dt = new \DateTime("now", $utc_tz);
+		$cvt_dtstart_dt->setTimestamp($dtstart_ts);
+		$cvt_dtstart->setDateTime($cvt_dtstart_dt, false);
+
+		$cvt_dtend = $end;
+		$cvt_dtend_dt = $cvt_dtend->getDateTime();
+		$dtend_ts = $cvt_dtend_dt->getTimestamp();
+		$cvt_dtend_dt = new \DateTime("now", $utc_tz);
+		$cvt_dtend_dt->setTimestamp($dtend_ts);
+		$cvt_dtend->setDateTime($cvt_dtend_dt, false);
+
+		$itip_msg = $iTipMessage->message->serialize();
+		$message->addPart(
+				$itip_msg,
+				'text/calendar; method=' . $iTipMessage->method,
+				'UTF-8'
 		);
-		$message->attach($attachment);
 
 		try {
 			$failed = $this->mailer->send($message);

lib/private/Mail/Message.php

@@ -58,6 +58,26 @@ public function attach(IAttachment $attachment): IMessage {
 		return $this;
 	}
 
+	/**
+	 * @param $body:  body of the mime part
+	 * @param $content-type = null: Mime Content-Type (e.g. text/plain or text/calendar)
+	 * @param $charset = null: Character Set (e.g. UTF-8)
+	 * @return $this
+	 * @since 14.0.4
+	 */
+	public function addPart($data, $content_type = null, $charset = null): IMessage {
+	       # To be sure this works with iCalendar messages, we encode with 8bit instead of
+	       # quoted-printable encoding. We save the current encoder, replace the current
+	       # encoder with an 8bit encoder and after we've finished, we reset the encoder
+	       # to the previous one.
+               $encoder = $this->swiftMessage->getEncoder();
+               $eightbit_encoder = new \Swift_Mime_ContentEncoder_PlainContentEncoder("8bit");
+               $this->swiftMessage->setEncoder($eightbit_encoder);
+               $this->swiftMessage->addPart($data, $content_type, $charset);
+               $this->swiftMessage->setEncoder($encoder);
+               return $this;
+        }
+
 	/**
 	 * SwiftMailer does currently not work with IDN domains, this function therefore converts the domains
 	 * FIXME: Remove this once SwiftMailer supports IDN

lib/public/Mail/IMessage.php

@@ -39,6 +39,15 @@ interface IMessage {
 	 */
 	public function attach(IAttachment $attachment): IMessage;
 
+	/**
+	 * @param $body:  body of the mime part
+	 * @param $content-type = null: Mime Content-Type (e.g. text/plain or text/calendar)
+	 * @param $charset = null: Character Set (e.g. UTF-8)
+	 * @return IMessage
+	 * @since 14.0.4
+	 */
+	public function addPart($body, $content_type = null, $charset = null): IMessage;
+
 	/**
 	 * Set the from address of this message.
 	 *