Nexus/apps/web/src/app/api/sse/timeline/route.ts

import { eventBus } from "@capakraken/api/sse";
import { startReminderScheduler } from "@capakraken/api/lib/reminder-scheduler";
import { SSE_EVENT_TYPES } from "@capakraken/shared";
import { auth } from "~/server/auth.js";

// Start the reminder scheduler (idempotent — only starts once)
startReminderScheduler();

export const dynamic = "force-dynamic";
export const runtime = "nodejs";

export async function GET() {
  const session = await auth();

  if (!session) {
    return new Response("Unauthorized", { status: 401 });
  }

  const encoder = new TextEncoder();

  const stream = new ReadableStream({
    start(controller) {
      // Send initial connection confirmation
      controller.enqueue(
        encoder.encode(`data: ${JSON.stringify({ type: SSE_EVENT_TYPES.PING, timestamp: new Date().toISOString() })}\n\n`),
      );

      // Subscribe to event bus
      const unsubscribe = eventBus.subscribe((event) => {
        try {
          controller.enqueue(encoder.encode(`data: ${JSON.stringify(event)}\n\n`));
        } catch {
          // Client disconnected
        }
      });

      // Heartbeat every 30 seconds
      const heartbeat = setInterval(() => {
        try {
          controller.enqueue(
            encoder.encode(`data: ${JSON.stringify({ type: SSE_EVENT_TYPES.PING, timestamp: new Date().toISOString() })}\n\n`),
          );
        } catch {
          clearInterval(heartbeat);
          unsubscribe();
        }
      }, 30000);

      // Cleanup on close
      return () => {
        clearInterval(heartbeat);
        unsubscribe();
      };
    },
  });

  return new Response(stream, {
    headers: {
      "Content-Type": "text/event-stream",
      "Cache-Control": "no-cache, no-transform",
      Connection: "keep-alive",
      "X-Accel-Buffering": "no",
    },
  });
}