feat(federation): rollbackFriendRequestCreate + side-effect registration

packages/server/src/utils/federationRollback.ts

@@ -12,6 +12,11 @@
  * Errors thrown by callbacks are logged but not re-thrown — rollback failure
  * must not prevent the outbox entry from being deleted.
  */
+import { getDb } from '../db/index.js';
+import * as schema from '../db/schema.js';
+import { eq } from 'drizzle-orm';
+import { connectionManager } from '../ws/handler.js';
+
 type PermanentFailureCallback = (messageId: string, reason: string) => void;
 
 const callbacks = new Map<string, PermanentFailureCallback>();
@@ -37,3 +42,54 @@ export function invokePermanentFailureCallback(eventType: string, messageId: str
 export function _resetCallbacks(): void {
   callbacks.clear();
 }
+
+/**
+ * Rollback handler for 'friend_request_create' outbox events.
+ *
+ * Deletes the pending friend request row whose relayMessageId matches the
+ * failed outbox message, then notifies the sender via WebSocket so the client
+ * can surface an appropriate error toast.
+ */
+export function rollbackFriendRequestCreate(messageId: string, receiverReason: string): void {
+  const db = getDb();
+
+  const row = db
+    .select()
+    .from(schema.friendRequests)
+    .where(eq(schema.friendRequests.relayMessageId, messageId))
+    .get();
+
+  if (!row) return; // Idempotent — no row to roll back.
+
+  // Look up recipient handle for the toast text BEFORE deleting.
+  const recipient = db
+    .select({ username: schema.users.username })
+    .from(schema.users)
+    .where(eq(schema.users.id, row.toId))
+    .get();
+  const targetHandle = recipient?.username ?? 'unknown';
+
+  db.delete(schema.friendRequests).where(eq(schema.friendRequests.id, row.id)).run();
+
+  // Reason mapping: receiver-side reason → client-facing reason.
+  //   'recipient_not_found' → 'user_not_found' (the looked-up identity vanished)
+  //   anything else         → 'peer_rejected' (catch-all)
+  const reason: 'user_not_found' | 'peer_rejected' =
+    receiverReason === 'recipient_not_found' ? 'user_not_found' : 'peer_rejected';
+
+  const message =
+    reason === 'user_not_found'
+      ? `User ${targetHandle} no longer exists on the remote instance.`
+      : `Friend request to ${targetHandle} was rejected by the remote instance.`;
+
+  connectionManager.sendToUser(row.fromId, {
+    type: 'friend_request_relay_failed',
+    requestId: row.id,
+    reason,
+    message,
+    targetHandle,
+  });
+}
+
+// Register the callback at module-load time so the worker invokes it.
+registerPermanentFailureCallback('friend_request_create', rollbackFriendRequestCreate);