Implement MSC4185

src/api/client_server/event_visibility.rs

@@ -0,0 +1,60 @@
+//! Implementation of [MSC4185](https://github.com/matrix-org/matrix-spec-proposals/pull/4185)
+
+use ruma::{
+    api::{request, response, Metadata},
+    metadata, OwnedEventId, OwnedRoomId, OwnedUserId,
+};
+
+use crate::{services, Ar, Ra, Result};
+
+const METADATA: Metadata = metadata! {
+    method: GET,
+    rate_limited: true,
+    authentication: AccessToken,
+
+    history: {
+        unstable => "/_matrix/client/unstable/net.tadzik/can_user_see_event/:room_id/:user_id/:event_id",
+    },
+};
+
+#[request]
+#[allow(clippy::struct_field_names)]
+pub(crate) struct Request {
+    #[ruma_api(path)]
+    pub(crate) room_id: OwnedRoomId,
+
+    #[ruma_api(path)]
+    pub(crate) user_id: OwnedUserId,
+
+    #[ruma_api(path)]
+    pub(crate) event_id: OwnedEventId,
+}
+
+#[response]
+pub(crate) struct Response {
+    #[ruma_api(body)]
+    pub(crate) is_visible: bool,
+}
+
+pub(crate) async fn can_user_see_event_route(
+    body: Ar<Request>,
+) -> Result<Ra<Response>> {
+    let Ok(true) = services().rooms.state_accessor.user_can_see_event(
+        body.sender_user.as_ref().expect("user is authenticated"),
+        &body.room_id,
+        &body.event_id,
+    ) else {
+        return Err(crate::Error::BadRequest(
+            ruma::api::client::error::ErrorKind::Unauthorized,
+            "event is not visible to requesting user",
+        ));
+    };
+
+    Ok(Ra(Response {
+        is_visible: services().rooms.state_accessor.user_can_see_event(
+            &body.user_id,
+            &body.room_id,
+            &body.event_id,
+        )?,
+    }))
+}