Allow to respond with modified common read value on "not modified" messages

We need to set the status code to 200 when the header is modified,
because as per "section 10.3.5 of RFC 2616" entity headers shall be
stripped out on 304: https://stackoverflow.com/a/17822709
This means the header would not be sent to the clients at all, so
they wouldn't update the read marker when idling in the chat.
For the web interface this is not needed, as we update the info
every 30 seconds with the conversation list refresh and can therefor
save the query

Signed-off-by: Joas Schilling <coding@schilljs.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/lib/Controller/ChatController.php b/lib/Controller/ChatController.php
index fd3cd0458..9aecf0fbe 100644
--- a/lib/Controller/ChatController.php
+++ b/lib/Controller/ChatController.php
@@ -275,6 +275,9 @@ class ChatController extends AEnvironmentAwareController {
 	 * @param int $lookIntoFuture Polling for new messages (1) or getting the history of the chat (0)
 	 * @param int $limit Number of chat messages to receive (100 by default, 200 at most)
 	 * @param int $lastKnownMessageId The last known message (serves as offset)
+	 * @param int $lastCommonReadId The last known common read message
+	 *                              (so the response is 200 instead of 304 when
+	 *                              it changes even when there are no messages)
 	 * @param int $timeout Number of seconds to wait for new messages (30 by default, 30 at most)
 	 * @param int $setReadMarker Automatically set the last read marker when 1,
 	 *                           if your client does this itself via chat/{token}/read set to 0
@@ -287,7 +290,14 @@ class ChatController extends AEnvironmentAwareController {
 	 *         'actorDisplayName', 'timestamp' (in seconds and UTC timezone) and
 	 *         'message'.
 	 */
-	public function receiveMessages(int $lookIntoFuture, int $limit = 100, int $lastKnownMessageId = 0, int $timeout = 30, int $setReadMarker = 1, int $includeLastKnown = 0, int $noStatusUpdate = 0): DataResponse {
+	public function receiveMessages(int $lookIntoFuture,
+									int $limit = 100,
+									int $lastKnownMessageId = 0,
+									int $lastCommonReadId = 0,
+									int $timeout = 30,
+									int $setReadMarker = 1,
+									int $includeLastKnown = 0,
+									int $noStatusUpdate = 0): DataResponse {
 		$limit = min(200, $limit);
 		$timeout = min(30, $timeout);
 
@@ -343,8 +353,15 @@ class ChatController extends AEnvironmentAwareController {
 
 		if (empty($comments)) {
 			$response = new DataResponse([], Http::STATUS_NOT_MODIFIED);
-			if ($this->participant->getAttendee()->getReadPrivacy() === Participant::PRIVACY_PUBLIC) {
-				$response->addHeader('X-Chat-Last-Common-Read', $this->chatManager->getLastCommonReadMessage($this->room));
+			if ($lastCommonReadId && $this->participant->getAttendee()->getReadPrivacy() === Participant::PRIVACY_PUBLIC) {
+				$newLastCommonRead = $this->chatManager->getLastCommonReadMessage($this->room);
+				if ($lastCommonReadId !== $newLastCommonRead) {
+					// Set the status code to 200 so the header is sent to the client.
+					// As per "section 10.3.5 of RFC 2616" entity headers shall be
+					// stripped out on 304: https://stackoverflow.com/a/17822709
+					$response->setStatus(Http::STATUS_OK);
+				}
+				$response->addHeader('X-Chat-Last-Common-Read', $newLastCommonRead);
 			}
 			return $response;
 		}