refactor(websocket): move websocket logic to its own module

server/modules/websocket/services/websocket-writer.service.ts

@@ -0,0 +1,38 @@
+import { WS_OPEN_STATE } from '@/modules/websocket/services/websocket-state.service.js';
+import type { RealtimeClientConnection } from '@/shared/types.js';
+
+/**
+ * Thin transport adapter that gives WebSocket connections the same interface as
+ * SSE writers used by API routes (`send`, `setSessionId`, `getSessionId`).
+ */
+export class WebSocketWriter {
+  ws: RealtimeClientConnection;
+  sessionId: string | null;
+  userId: string | number | null;
+  isWebSocketWriter: boolean;
+
+  constructor(ws: RealtimeClientConnection, userId: string | number | null = null) {
+    this.ws = ws;
+    this.sessionId = null;
+    this.userId = userId;
+    this.isWebSocketWriter = true;
+  }
+
+  send(data: unknown): void {
+    if (this.ws.readyState === WS_OPEN_STATE) {
+      this.ws.send(JSON.stringify(data));
+    }
+  }
+
+  updateWebSocket(newRawWs: RealtimeClientConnection): void {
+    this.ws = newRawWs;
+  }
+
+  setSessionId(sessionId: string): void {
+    this.sessionId = sessionId;
+  }
+
+  getSessionId(): string | null {
+    return this.sessionId;
+  }
+}