main: try to get target from actor.object

https://github.com/astro/buzzrelay/issues/15

src/actor.rs

@@ -84,6 +84,28 @@ impl Actor {
         Some(Actor { host, kind })
     }
 
+    pub fn from_object(action: &activitypub::Action<serde_json::Value>) -> Option<Self> {
+        let action_object = action.object.as_ref()?;
+
+        let mut action_target: Option<String> = None;
+        if let Some(action_object) = action_object.as_str() {
+            action_target = Some(action_object.to_string());
+        }
+        if let Some(action_object_0) = action_object.as_array()
+            .and_then(|action_object| {
+                if action_object.len() == 1 {
+                    action_object.first()
+                } else {
+                    None
+                }
+            }).and_then(|action_object_0| action_object_0.as_str())
+        {
+            action_target = Some(action_object_0.to_string());
+        }
+
+        action_target.and_then(|action_target| Self::from_uri(&action_target))
+    }
+
     pub fn uri(&self) -> String {
         match &self.kind {
             ActorKind::TagRelay(tag) =>

src/main.rs

@@ -148,7 +148,7 @@ async fn post_language_relay(
 async fn post_relay(
     state: State,
     endpoint: endpoint::Endpoint<'_>,
-    target: actor::Actor
+    mut target: actor::Actor
 ) -> Response {
     if let Some((redis, in_topic)) = &state.redis {
         if let Ok(data) = serde_json::to_vec(&endpoint.payload) {
@@ -188,6 +188,13 @@ async fn post_relay(
         let Ok(remote_actor) = remote_actor else {
             return (StatusCode::BAD_REQUEST, "Invalid actor").into_response();
         };
+        if let Some(action_target) = Actor::from_object(&action) {
+            if action_target.host == state.hostname {
+                // A sharedInbox receives the actual follow target in the
+                // `object` field.
+                target = action_target;
+            }
+        }
         let priv_key = state.priv_key.clone();
         let client = state.client.clone();
         tokio::spawn(async move {
@@ -243,6 +250,13 @@ async fn post_relay(
         let Ok(remote_actor) = remote_actor else {
             return (StatusCode::BAD_REQUEST, "Invalid actor").into_response();
         };
+        if let Some(action_target) = Actor::from_object(&action) {
+            if action_target.host == state.hostname {
+                // A sharedInbox receives the actual follow target in the
+                // `object` field.
+                target = action_target;
+            }
+        }
         match state.database.del_follow(
             &remote_actor.id,
             &target.uri(),