From 0c53a1e83a2a866a8f52a6b2faa0c39b3d8ddbc1 Mon Sep 17 00:00:00 2001
From: Olivier 'reivilibre <oliverw@matrix.org>
Date: Mon, 22 Dec 2025 14:15:18 +0000
Subject: [PATCH] EventBase: add the concept of sticky_duration

---
 synapse/events/__init__.py | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index c7eaf7eda2..83916211af 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -36,7 +36,12 @@ from typing import (
 import attr
 from unpaddedbase64 import encode_base64
 
-from synapse.api.constants import EventContentFields, EventTypes, RelationTypes
+from synapse.api.constants import (
+    EventContentFields,
+    EventTypes,
+    RelationTypes,
+    StickyEvent,
+)
 from synapse.api.room_versions import EventFormatVersions, RoomVersion, RoomVersions
 from synapse.synapse_rust.events import EventInternalMetadata
 from synapse.types import (
@@ -318,6 +323,23 @@ class EventBase(metaclass=abc.ABCMeta):
         # this will be a no-op if the event dict is already frozen.
         self._dict = freeze(self._dict)
 
+    def sticky_duration(self) -> int | None:
+        """
+        Returns the effective sticky duration of this event, or None
+        if the event does not have a sticky duration.
+        (Sticky Events are a MSC4354 feature.)
+
+        Clamps the sticky duration to the maximum allowed duration.
+        """
+        sticky_obj = self.get_dict().get(StickyEvent.FIELD_NAME, None)
+        if type(sticky_obj) is not dict:
+            return None
+        sticky_duration_ms = sticky_obj.get("duration_ms", None)
+        # MSC: Valid values are the integer range 0-MAX_DURATION_MS
+        if type(sticky_duration_ms) is int and sticky_duration_ms >= 0:
+            return min(sticky_duration_ms, StickyEvent.MAX_DURATION_MS)
+        return None
+
     def __str__(self) -> str:
         return self.__repr__()