/*────────────────────────  Manual SSE chat handler  ─────────────────*/
async function handleChat(
  req: Request,
  env: Env,
  ctx: ExecutionContext
): Promise<Response> {
  /* Parse JSON body */
  const { message, lastResponseId, trace_id } = (await req.json()) as {
    message: string;
    lastResponseId?: string;
    trace_id?: string;
  };

  /* Get or generate trace_id for grouping conversations */
  const traceId = trace_id || `trace_${Math.random().toString(36).substring(2, 34)}`;

  /* Initialise tracing/exporter once */
  await initTracing(env.OPENAI_API_KEY);

  /* Dynamically import SDK pieces that may use crypto or fs */
  const { Agent, Runner, withTrace } = await import("@openai/agents");

  /* Build agent & runner */
  const agent = new Agent({
    name: "Site Assistant",
    instructions: "You will answer questions by using the search_tool(query).",
    outputType: "text",
    model: "gpt-4.1",
    // tools: [searchTool],
  });

  const runner = new Runner({
    tracingDisabled: false,          // default
  });

  let runResult: any;
  await withTrace('cf-assistant-ui', async () => {
    runResult = await runner.run(agent, message, {
      stream: true,
      previousResponseId: lastResponseId,
    });
  }, {
    traceId: traceId,
    groupId: traceId, // Use same ID for grouping conversations
  });

  /* Create manual SSE stream */
  const stream = new ReadableStream({
    async start(controller) {
      const encoder = new TextEncoder();
      
      try {
        for await (const ev of runResult) {
          // Handle raw model stream events which contain the delta text
          if (ev.type === 'raw_model_stream_event') {
            // Check if this is an output_text_delta event
            if (ev.data && ev.data.type === 'output_text_delta' && ev.data.delta) {
              const textDelta = (ev as any).data.delta;
              controller.enqueue(encoder.encode(`event: text-delta\ndata: ${textDelta}\n\n`));
            }
            // Handle completion
            else if (ev.data && ev.data.type === 'response_done') {
              controller.enqueue(encoder.encode(`event: lastResponseId\ndata: ${ev.data.response.id}\n\n`));
              controller.enqueue(encoder.encode(`event: trace_id\ndata: ${traceId}\n\n`));
              controller.enqueue(encoder.encode('event: done\ndata: [DONE]\n\n'));
              break;
            }
          }
        }
      } catch (error) {
        console.error('Error processing stream:', error);
        controller.enqueue(encoder.encode(`event: error\ndata: ${String(error)}\n\n`));
      } finally {
        controller.close();
      }
    }
  });

  

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream',
      'Cache-Control': 'no-cache',
      'Connection': 'keep-alive',
      'Access-Control-Allow-Origin': '*',
    }
  });
}