feat(loro-websocket): add sendExternalUpdates method to LoroWebsocketClient (#46)

Add a new public method sendExternalUpdates() that allows users to send
additional updates to a specified room that are not from the local peer's
document. This is useful for forwarding updates received from other
sources or peers.

The method:
- Takes crdt type, roomId, and an array of update payloads
- Validates that the room is active and WebSocket is open
- Uses existing sendUpdateOrFragments() for proper fragmentation handling
- Throws descriptive errors if preconditions are not met

Co-authored-by: lody <[email protected]>

Author: lodyai[bot]

packages/loro-websocket/src/client/index.ts

@@ -1215,6 +1215,41 @@ export class LoroWebsocketClient {
     );
   }
 
+  /**
+   * Send additional updates to a specified room.
+   *
+   * This method allows sending updates that are not from the local peer's document,
+   * such as updates received from other sources or peers. The updates will be
+   * broadcast to the room and other connected clients.
+   *
+   * @param crdt - The CRDT type of the room
+   * @param roomId - The room ID to send updates to
+   * @param updates - Array of update payloads to send
+   * @throws Error if not connected or room is not active
+   */
+  sendExternalUpdates(
+    crdt: CrdtType,
+    roomId: string,
+    updates: Uint8Array[]
+  ): void {
+    const id = crdt + roomId;
+    const active = this.activeRooms.get(id);
+    if (!active) {
+      throw new Error(
+        `Cannot send updates: room ${roomId} (${crdt}) is not active`
+      );
+    }
+
+    if (!this.ws || this.ws.readyState !== WebSocket.OPEN) {
+      throw new Error("Cannot send updates: WebSocket is not open");
+    }
+
+    // Send each update individually, fragmenting when necessary
+    for (const update of updates) {
+      this.sendUpdateOrFragments(crdt, roomId, update);
+    }
+  }
+
   consumeSentBatch(refId: HexString): { roomKey: string; updates: Uint8Array[] } | undefined {
     const entry = this.sentUpdateBatches.get(refId);
     if (entry) {