refactor: extract _writePrimingEvent helper method

Author: felixweinberger

src/server/streamableHttp.ts

@@ -258,6 +258,22 @@ export class StreamableHTTPServerTransport implements Transport {
         }
     }
 
+    /**
+     * Writes a priming event to establish resumption capability.
+     * This primes the client's Last-Event-ID for reconnection.
+     */
+    private async _writePrimingEvent(res: ServerResponse, streamId: string): Promise<void> {
+        const primingEventId = this._eventStore
+            ? await this._eventStore.storeEvent(streamId, {} as JSONRPCMessage)
+            : `priming-${Date.now()}`;
+
+        let primingEvent = `id: ${primingEventId}\ndata: \n\n`;
+        if (this._retryInterval !== undefined) {
+            primingEvent = `id: ${primingEventId}\nretry: ${this._retryInterval}\ndata: \n\n`;
+        }
+        res.write(primingEvent);
+    }
+
     /**
      * Handles GET requests for SSE stream
      */
@@ -329,18 +345,7 @@ export class StreamableHTTPServerTransport implements Transport {
         // otherwise the client will just wait for the first message
         res.writeHead(200, headers).flushHeaders();
 
-        // Send priming event to establish resumption capability
-        // This primes the client's Last-Event-ID for reconnection
-        const primingEventId = this._eventStore
-            ? await this._eventStore.storeEvent(this._standaloneSseStreamId, {} as JSONRPCMessage)
-            : `priming-${Date.now()}`;
-
-        // Build priming event - always include id for resumability, optionally add retry for polling
-        let primingEvent = `id: ${primingEventId}\ndata: \n\n`;
-        if (this._retryInterval !== undefined) {
-            primingEvent = `id: ${primingEventId}\nretry: ${this._retryInterval}\ndata: \n\n`;
-        }
-        res.write(primingEvent);
+        await this._writePrimingEvent(res, this._standaloneSseStreamId);
 
         // Assign the response to the standalone SSE stream
         this._streamMapping.set(this._standaloneSseStreamId, res);
@@ -570,18 +575,7 @@ export class StreamableHTTPServerTransport implements Transport {
 
                     res.writeHead(200, headers);
 
-                    // Send priming event to establish resumption capability
-                    // This primes the client's Last-Event-ID for reconnection
-                    const primingEventId = this._eventStore
-                        ? await this._eventStore.storeEvent(streamId, {} as JSONRPCMessage)
-                        : `priming-${Date.now()}`;
-
-                    // Build priming event - always include id for resumability, optionally add retry for polling
-                    let primingEvent = `id: ${primingEventId}\ndata: \n\n`;
-                    if (this._retryInterval !== undefined) {
-                        primingEvent = `id: ${primingEventId}\nretry: ${this._retryInterval}\ndata: \n\n`;
-                    }
-                    res.write(primingEvent);
+                    await this._writePrimingEvent(res, streamId);
                 }
                 // Store the response for this request to send messages back through this connection
                 // We need to track by request ID to maintain the connection