feat(activitypub): implement user outbox endpoint and federate thoughts to followers

thoughts-backend/api/src/federation.rs

@@ -0,0 +1,71 @@
+use app::{
+    persistence::{follow, user},
+    state::AppState,
+};
+use models::domains::thought;
+use serde_json::json;
+
+// This function handles pushing a new thought to all followers.
+pub async fn federate_thought(
+    state: AppState,
+    thought: thought::Model,
+    author: models::domains::user::Model,
+) {
+    // Find all followers of the author
+    let follower_ids = match follow::get_follower_ids(&state.conn, author.id).await {
+        Ok(ids) => ids,
+        Err(e) => {
+            tracing::error!("Failed to get followers for federation: {}", e);
+            return;
+        }
+    };
+
+    if follower_ids.is_empty() {
+        tracing::debug!("No followers to federate to for user {}", author.username);
+        return;
+    }
+
+    let base_url = "http://localhost:3000"; // Replace in production
+    let thought_url = format!("{}/thoughts/{}", base_url, thought.id);
+    let author_url = format!("{}/users/{}", base_url, author.username);
+
+    // Construct the "Create" activity containing the "Note" object
+    let activity = json!({
+        "@context": "https://www.w3.org/ns/activitystreams",
+        "id": format!("{}/activity", thought_url),
+        "type": "Create",
+        "actor": author_url,
+        "object": {
+            "id": thought_url,
+            "type": "Note",
+            "attributedTo": author_url,
+            "content": thought.content,
+            "published": thought.created_at.to_rfc3339(),
+            "to": ["https://www.w3.org/ns/activitystreams#Public"],
+            "cc": [format!("{}/followers", author_url)]
+        }
+    });
+
+    // Get the inbox URLs for all followers
+    // In a real federated app, you would store remote users' full inbox URLs.
+    // For now, we assume followers are local and construct their inbox URLs.
+    let followers = match user::get_users_by_ids(&state.conn, follower_ids).await {
+        Ok(users) => users,
+        Err(e) => {
+            tracing::error!("Failed to get follower user objects: {}", e);
+            return;
+        }
+    };
+
+    let client = reqwest::Client::new();
+    for follower in followers {
+        let inbox_url = format!("{}/users/{}/inbox", base_url, follower.username);
+        tracing::info!("Federating post {} to {}", thought.id, inbox_url);
+
+        let res = client.post(&inbox_url).json(&activity).send().await;
+
+        if let Err(e) = res {
+            tracing::error!("Failed to federate to {}: {}", inbox_url, e);
+        }
+    }
+}