watchlist backfill

crates/adapters/postgres-federation/src/lib.rs

@@ -631,6 +631,45 @@ impl FederationRepository for PostgresFederationRepository {
         .await?;
         Ok(count > 0)
     }
+
+    async fn migrate_follower_actor(
+        &self,
+        old_actor_url: &str,
+        new_actor_url: &str,
+    ) -> Result<Vec<uuid::Uuid>> {
+        let candidates: Vec<String> = sqlx::query_scalar(
+            "SELECT local_user_id FROM ap_following
+             WHERE remote_actor_url = $1
+               AND local_user_id NOT IN (
+                   SELECT local_user_id FROM ap_following WHERE remote_actor_url = $2
+               )",
+        )
+        .bind(old_actor_url)
+        .bind(new_actor_url)
+        .fetch_all(&self.pool)
+        .await?;
+
+        if candidates.is_empty() {
+            return Ok(vec![]);
+        }
+
+        sqlx::query(
+            "UPDATE ap_following SET remote_actor_url = $1
+             WHERE remote_actor_url = $2
+               AND local_user_id NOT IN (
+                   SELECT local_user_id FROM ap_following WHERE remote_actor_url = $1
+               )",
+        )
+        .bind(new_actor_url)
+        .bind(old_actor_url)
+        .execute(&self.pool)
+        .await?;
+
+        candidates
+            .into_iter()
+            .map(|s| uuid::Uuid::parse_str(&s).map_err(|e| anyhow::anyhow!(e)))
+            .collect()
+    }
 }
 
 #[async_trait]