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

@@ -55,6 +55,14 @@ pub trait ApObjectHandler: Send + Sync {
     /// 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<()>;
 
+    /// Called when an inbound Note tags a local user with a Mention.
+    async fn on_mention(
+        &self,
+        thought_ap_id: &Url,
+        mentioned_user_uuid: uuid::Uuid,
+        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

@@ -147,7 +147,44 @@ impl ApObjectHandler for ThoughtsObjectHandler {
                 note.in_reply_to.as_ref(),
             )
             .await
-            .map_err(|e| anyhow!("{e}"))
+            .map_err(|e| anyhow!("{e}"))?;
+
+        // Fire mention notifications for local @mentions in the note's tag array.
+        let base_url = url::Url::parse(&self.urls.base_url)
+            .ok()
+            .and_then(|u| u.host_str().map(|h| h.to_string()))
+            .unwrap_or_default();
+
+        for tag in &note.tag {
+            if tag.get("type").and_then(|t| t.as_str()) != Some("Mention") {
+                continue;
+            }
+            let href = match tag.get("href").and_then(|h| h.as_str()) {
+                Some(h) => h,
+                None => continue,
+            };
+            let href_url = match url::Url::parse(href) {
+                Ok(u) => u,
+                Err(_) => continue,
+            };
+            if href_url.host_str().unwrap_or("") != base_url {
+                continue;
+            }
+            let user_uuid = href_url
+                .path()
+                .strip_prefix("/users/")
+                .and_then(|s| s.split('/').next())
+                .and_then(|s| uuid::Uuid::parse_str(s).ok());
+            if let Some(uuid) = user_uuid {
+                self.on_mention(ap_id, uuid, actor_url)
+                    .await
+                    .unwrap_or_else(|e| {
+                        tracing::warn!(error = %e, "failed to process mention notification");
+                    });
+            }
+        }
+
+        Ok(())
     }
 
     async fn on_update(
@@ -225,6 +262,46 @@ impl ApObjectHandler for ThoughtsObjectHandler {
         Ok(())
     }
 
+    async fn on_mention(
+        &self,
+        thought_ap_id: &url::Url,
+        mentioned_user_uuid: uuid::Uuid,
+        actor_url: &url::Url,
+    ) -> anyhow::Result<()> {
+        let author_user_id = match self
+            .repo
+            .find_remote_actor_id(actor_url)
+            .await
+            .map_err(|e| anyhow!("{e}"))?
+        {
+            Some(id) => id,
+            None => return Ok(()),
+        };
+
+        let thought_uuid = thought_ap_id
+            .path()
+            .strip_prefix("/thoughts/")
+            .and_then(|s| s.split('/').next())
+            .and_then(|s| uuid::Uuid::parse_str(s).ok());
+
+        let thought_uuid = match thought_uuid {
+            Some(u) => u,
+            None => return Ok(()),
+        };
+
+        if let Some(ep) = &self.event_publisher {
+            ep.publish(&domain::events::DomainEvent::MentionReceived {
+                thought_id: domain::value_objects::ThoughtId::from_uuid(thought_uuid),
+                mentioned_user_id: domain::value_objects::UserId::from_uuid(mentioned_user_uuid),
+                author_user_id,
+            })
+            .await
+            .map_err(|e| anyhow!("{e}"))?;
+        }
+
+        Ok(())
+    }
+
     async fn on_announce_received(&self, object_url: &Url, actor_url: &Url) -> Result<()> {
         let thought_uuid = object_url
             .path()

crates/adapters/activitypub/src/note.rs

@@ -24,6 +24,8 @@ pub struct ThoughtNote {
     pub sensitive: bool,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub summary: Option<String>,
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
+    pub tag: Vec<serde_json::Value>,
 }
 
 impl ThoughtNote {
@@ -50,6 +52,7 @@ impl ThoughtNote {
             in_reply_to,
             sensitive,
             summary,
+            tag: Vec::new(),
         }
     }
 }

crates/adapters/event-payload/src/lib.rs

@@ -81,6 +81,11 @@ pub enum EventPayload {
         connection_type: String,
         page: u32,
     },
+    MentionReceived {
+        thought_id: String,
+        mentioned_user_id: String,
+        author_user_id: String,
+    },
 }
 
 impl EventPayload {
@@ -104,6 +109,7 @@ impl EventPayload {
             Self::ProfileUpdated { .. } => "users.profile_updated",
             Self::FetchRemoteActorPosts { .. } => "federation.fetch_outbox",
             Self::FetchActorConnections { .. } => "federation.fetch_connections",
+            Self::MentionReceived { .. } => "mentions.received",
         }
     }
 }
@@ -234,6 +240,15 @@ impl From<&DomainEvent> for EventPayload {
                 connection_type: connection_type.clone(),
                 page: *page,
             },
+            DomainEvent::MentionReceived {
+                thought_id,
+                mentioned_user_id,
+                author_user_id,
+            } => Self::MentionReceived {
+                thought_id: thought_id.to_string(),
+                mentioned_user_id: mentioned_user_id.to_string(),
+                author_user_id: author_user_id.to_string(),
+            },
         }
     }
 }
@@ -373,6 +388,18 @@ impl TryFrom<EventPayload> for DomainEvent {
                 connection_type,
                 page,
             },
+            EventPayload::MentionReceived {
+                thought_id,
+                mentioned_user_id,
+                author_user_id,
+            } => DomainEvent::MentionReceived {
+                thought_id: ThoughtId::from_uuid(parse_uuid(&thought_id, "thought_id")?),
+                mentioned_user_id: UserId::from_uuid(parse_uuid(
+                    &mentioned_user_id,
+                    "mentioned_user_id",
+                )?),
+                author_user_id: UserId::from_uuid(parse_uuid(&author_user_id, "author_user_id")?),
+            },
         })
     }
 }

crates/application/src/services/notification_event.rs

@@ -112,6 +112,23 @@ impl NotificationEventService {
                     })
                     .await
             }
+            DomainEvent::MentionReceived {
+                thought_id,
+                mentioned_user_id,
+                author_user_id,
+            } => {
+                self.notifications
+                    .save(&Notification {
+                        id: NotificationId::new(),
+                        user_id: mentioned_user_id.clone(),
+                        notification_type: NotificationType::Mention,
+                        from_user_id: Some(author_user_id.clone()),
+                        thought_id: Some(thought_id.clone()),
+                        read: false,
+                        created_at: Utc::now(),
+                    })
+                    .await
+            }
             _ => Ok(()),
         }
     }

crates/domain/src/events.rs

@@ -73,6 +73,11 @@ pub enum DomainEvent {
         connection_type: String,
         page: u32,
     },
+    MentionReceived {
+        thought_id: ThoughtId,
+        mentioned_user_id: UserId,
+        author_user_id: UserId,
+    },
 }
 
 pub struct EventEnvelope {