feat(ap): handle Undo(Like) inbound activity

crates/adapters/activitypub-base/src/activities.rs

@@ -279,6 +279,20 @@ impl Activity for UndoActivity {
                     tracing::info!(ap_id = %ap_id_str, "undo Add (watchlist remove)");
                 }
             }
+            "Like" => {
+                if let Some(obj_url_str) = self.object.get("object").and_then(|o| o.as_str())
+                    && let Ok(obj_url) = Url::parse(obj_url_str)
+                    && obj_url.host_str().unwrap_or("") == data.domain
+                {
+                    data.object_handler
+                        .on_unlike(&obj_url, self.actor.inner())
+                        .await
+                        .unwrap_or_else(|e| {
+                            tracing::warn!(error = %e, "failed to process unlike");
+                        });
+                }
+                tracing::info!(actor = %self.actor.inner(), "received Undo(Like)");
+            }
             other => {
                 tracing::debug!(kind = %other, "ignoring Undo of unknown activity type");
             }

crates/adapters/activitypub-base/src/content.rs

@@ -52,6 +52,9 @@ pub trait ApObjectHandler: Send + Sync {
     /// `actor_url` is the AP URL of the remote actor who sent the Announce.
     async fn on_announce_received(&self, object_url: &Url, actor_url: &Url) -> anyhow::Result<()>;
 
+    /// Called when a remote actor removes a Like from a local thought.
+    async fn on_unlike(&self, object_url: &Url, actor_url: &Url) -> anyhow::Result<()>;
+
     /// Total number of locally-authored posts across all users.
     async fn count_local_posts(&self) -> anyhow::Result<u64>;
 }

crates/adapters/activitypub/src/handler.rs

@@ -221,6 +221,10 @@ impl ApObjectHandler for ThoughtsObjectHandler {
         Ok(())
     }
 
+    async fn on_unlike(&self, _object_url: &url::Url, _actor_url: &url::Url) -> anyhow::Result<()> {
+        Ok(())
+    }
+
     async fn on_announce_received(&self, object_url: &Url, actor_url: &Url) -> Result<()> {
         let thought_uuid = object_url
             .path()