Port the PresenceRouter module interface to the new generic interface (#10524)

Port the PresenceRouter module interface to the new generic interface introduced in v1.37.0

3 files changed, 52 insertions, 14 deletions

diff --git a/docs/modules.md b/docs/modules.md
index 9a430390a4..ae8d6f5b73 100644
--- a/docs/modules.md
+++ b/docs/modules.md
@@ -282,6 +282,52 @@ the request is a server admin.
 Modules can modify the `request_content` (by e.g. adding events to its `initial_state`),
 or deny the room's creation by raising a `module_api.errors.SynapseError`.
 
+#### Presence router callbacks
+
+Presence router callbacks allow module developers to specify additional users (local or remote)
+to receive certain presence updates from local users. Presence router callbacks can be 
+registered using the module API's `register_presence_router_callbacks` method.
+
+The available presence router callbacks are:
+
+```python 
+async def get_users_for_states(
+    self,
+    state_updates: Iterable["synapse.api.UserPresenceState"],
+) -> Dict[str, Set["synapse.api.UserPresenceState"]]:
+```
+**Requires** `get_interested_users` to also be registered
+
+Called when processing updates to the presence state of one or more users. This callback can
+be used to instruct the server to forward that presence state to specific users. The module
+must return a dictionary that maps from Matrix user IDs (which can be local or remote) to the
+`UserPresenceState` changes that they should be forwarded.
+
+Synapse will then attempt to send the specified presence updates to each user when possible.
+
+```python
+async def get_interested_users(
+        self, 
+        user_id: str
+) -> Union[Set[str], "synapse.module_api.PRESENCE_ALL_USERS"]
+```
+**Requires** `get_users_for_states` to also be registered
+
+Called when determining which users someone should be able to see the presence state of. This
+callback should return complementary results to `get_users_for_state` or the presence information 
+may not be properly forwarded.
+
+The callback is given the Matrix user ID for a local user that is requesting presence data and
+should return the Matrix user IDs of the users whose presence state they are allowed to
+query. The returned users can be local or remote. 
+
+Alternatively the callback can return `synapse.module_api.PRESENCE_ALL_USERS`
+to indicate that the user should receive updates from all known users.
+
+For example, if the user `@alice:example.org` is passed to this method, and the Set 
+`{"@bob:example.com", "@charlie:somewhere.org"}` is returned, this signifies that Alice 
+should receive presence updates sent by Bob and Charlie, regardless of whether these users 
+share a room.
 
 ### Porting an existing module that uses the old interface
 
diff --git a/docs/presence_router_module.md b/docs/presence_router_module.md
index 4a3e720240..face54fe2b 100644
--- a/docs/presence_router_module.md
+++ b/docs/presence_router_module.md
@@ -1,3 +1,9 @@
+<h2 style="color:red">
+This page of the Synapse documentation is now deprecated. For up to date
+documentation on setting up or writing a presence router module, please see
+<a href="modules.md">this page</a>.
+</h2>
+
 # Presence Router Module
 
 Synapse supports configuring a module that can specify additional users
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index aeebcaf45f..6030e85a08 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -108,20 +108,6 @@ presence:
   #
   #enabled: false
 
-  # Presence routers are third-party modules that can specify additional logic
-  # to where presence updates from users are routed.
-  #
-  presence_router:
-    # The custom module's class. Uncomment to use a custom presence router module.
-    #
-    #module: "my_custom_router.PresenceRouter"
-
-    # Configuration options of the custom module. Refer to your module's
-    # documentation for available options.
-    #
-    #config:
-    #  example_option: 'something'
-
 # Whether to require authentication to retrieve profile data (avatars,
 # display names) of other users through the client API. Defaults to
 # 'false'. Note that profile data is also available via the federation