From 323227ceade1d69b66a5aebf713ba6431e840b32 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Tue, 11 Oct 2022 11:42:57 +0100
Subject: [PATCH] Implement behaviours for `m.read.private` receipts

---
 clientapi/routing/receipt.go        | 8 +++++---
 federationapi/consumers/receipts.go | 8 ++++++++
 syncapi/streams/stream_receipt.go   | 4 ++++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/clientapi/routing/receipt.go b/clientapi/routing/receipt.go
index 0f9b1b4ff..b70d85a17 100644
--- a/clientapi/routing/receipt.go
+++ b/clientapi/routing/receipt.go
@@ -37,9 +37,11 @@ func SetReceipt(req *http.Request, syncProducer *producers.SyncAPIProducer, devi
 		"timestamp":   timestamp,
 	}).Debug("Setting receipt")
 
-	// currently only m.read is accepted
-	if receiptType != "m.read" {
-		return util.MessageResponse(400, fmt.Sprintf("receipt type must be m.read not '%s'", receiptType))
+	switch receiptType {
+	case "m.read":
+	case "m.read.private":
+	default:
+		return util.MessageResponse(400, fmt.Sprintf("receipt type '%s' not known", receiptType))
 	}
 
 	if err := syncProducer.SendReceipt(req.Context(), device.UserID, roomID, eventID, receiptType, timestamp); err != nil {
diff --git a/federationapi/consumers/receipts.go b/federationapi/consumers/receipts.go
index 366cb264e..268ca626e 100644
--- a/federationapi/consumers/receipts.go
+++ b/federationapi/consumers/receipts.go
@@ -81,6 +81,14 @@ func (t *OutputReceiptConsumer) onMessage(ctx context.Context, msgs []*nats.Msg)
 		Type:    msg.Header.Get("type"),
 	}
 
+	switch receipt.Type {
+	case "m.read":
+		// These are allowed to be sent over federation
+	case "m.read.private":
+		// These must not be sent over federation
+		return true
+	}
+
 	// only send receipt events which originated from us
 	_, receiptServerName, err := gomatrixserverlib.SplitID('@', receipt.UserID)
 	if err != nil {
diff --git a/syncapi/streams/stream_receipt.go b/syncapi/streams/stream_receipt.go
index bba911022..977815078 100644
--- a/syncapi/streams/stream_receipt.go
+++ b/syncapi/streams/stream_receipt.go
@@ -67,6 +67,10 @@ func (p *ReceiptStreamProvider) IncrementalSync(
 		if _, ok := req.IgnoredUsers.List[receipt.UserID]; ok {
 			continue
 		}
+		// Don't send private read receipts to other users
+		if receipt.Type == "m.read.private" && req.Device.UserID != receipt.UserID {
+			continue
+		}
 		receiptsByRoom[receipt.RoomID] = append(receiptsByRoom[receipt.RoomID], receipt)
 	}